Vertigo v.0.26 documentationThe
Vertigo 
Flight Simulator
version 0.26
by
Anton Norup Sørensen 
Latest edition of this document: April, 2002
This document is distributed in HTML format as "ver_docs.htm" and in plain text 
as "vertigo.txt" 


  Contents
  Introduction 
  Description 
  Disclaimer 
  Instructions 
    Installation 
    Hardware requirements 
    Menus 
      Controls: Linear / exponential controls 
      Controls: Noise filter 
      Graphics resolution 
      Graphics: Viewing geometry 
      Graphics: Set landscape drawing distance 
      Calculations 
      Realism 
    Keyboard commands 
    Head Up Display 
      Navigation mode 
      Air to ground mode 
      Air to air mode 
    Instruments 
    Scenario 
  Flight Model 
    Propeller engines 
    Jet engines 
    Rocket engines 
  Weapons 
  Targets 
  Selectable aircraft 
    Grumman F-14A Tomcat 
    British Aerospace Sea Harrier 
    Lockheed F-104 Starfighter 
    Lockheed U-2 
    Vought F4U-1 Corsair 
    Saab MFI-17 Supporter 
    Dihedral demo 
    North American X-15A-2 
    Grumman Lunar Module 5 
  Carrier Landings 
  Catapult launches 
  Other things to try 
    Spins 
  Flight data logging 
  Tips for beginners 
  Version history 
    Latest changes: April 2002, version 0.26 
  Known bugs 
  Updating 
  Distribution 
  Troubleshooting 
  Other "home-built" flight sims 
  About the author 
  Why is the simulator called "Vertigo"? 
  How can YOU help making Vertigo better? 
  Credits 
  Feedback 



Introduction
I have wanted to write my own flight simulator since I got my first computer, a 
VIC-20 back in 1982, or so. The commercially available flight simulators often 
offered great game-play, but had frustratingly crude flight models. In the 
winter 1993/94, I enjoyed Eyal Lebedinsky's public domain simulator, "FLY8". It 
convinced me that it was possible to write a fairly realistic and fast 
simulator, running on a IBM-compatible PC, as a hobby project. In the summer of 
1994, I bought my first PC, and started writing Vertigo in the autumn. It was my 
first piece of C-code longer than ten lines.
Mean while, the quality of simulators for the PC has risen considerably, and 
some have quite nice flight models. Still, programming on your own is 
worthwhile, as a means to understanding the physics of flight and plainly having 
fun. 


Description
In short:
Vertigo is a flight simulator that focuses on realism of the flight model. 
Several types of aircraft are selectable. Scenario is a mountain-landscape with 
an airfield, surrounded by a sea on which an aircraft carrier sails. Also a 
Lunar scenario is available. Day or night illumination can be selected. 


Disclaimer
You are using this software at your own risk. I am not responsible for any 
damage to your soft- or hardware caused by the included software. 
This program is a computer game. It is not suitable for flight training or 
aircraft design. Failure to understand this may lead to a life-threatening 
situation. 
If this program crashes, interrupts may be left in a way that will crash the 
entire computer, requiring a reboot. So do not run any other programs operating 
on important files etc., while running Vertigo. 



Instructions
Installation
Vertigo is not plug-and-play. It will take a little effort to get it
running properly.
Please take your time to go through the steps described in INSTALL.TXT



Hardware requirements
         The simulator will in principle run on a 386 PC with math 
        co-processor, but to get proper performance, you will at least 
        need a 486DX2/66. A 100MHz Pentium or faster is recommended. 
	For low-end PCs, read the section on "Configure calculations"
	carefully.
		 
         For controls, an analog joystick is strongly recommended, but a
        mouse can also be used. Rudder pedals and throttle are supported. 
        There are problems with some modern joystics. The old-fashioned
        analog ones using the gameport usually work well.
	
         For sound, only Sound Blaster compatible cards are supported.
	For proper setup under DOS, define the BLASTER environment variable, 
        e.g. SET BLASTER=A220 I5 D1 H1 T4

Menus
	Access the Main Menu by pressing [ESC] in Vertigo.

        The nice MGUI (Morello Graphical User Interface) is used.
        The menu is intended to be mouse operated, but it is also
        possible to use keyboard:
         Arrow keys changes focus between items.
         TAB skips between sections.
         ENTER activates an item.
         F10 activates the upper menu bar.

        I like to think the menues are very easy to use.
        Nevertheless, here are a few explanations for some of the
        more obscure options:
                
Controls menu: Linear / Exponential controls:
        Exponential mode has 50% lower sensitivity at small deflection,
        but at larger deflection the sensitivity increases rapidly.
        The full stroke is the same in both modes. Exponential controls
        are recommended.

Controls menu: Noise filter:
        The joystick can be read 1, 3, or 5 times for each frame.
        The median of the readings is used as control input.
        For a noisy joystick setup, use a large number of readings.

Graphics: Graphics resolution:
        The three resolutions can only be selected at program start-up, 
        not in-flight. The monitor frequency will also be changed, but this
        will only be effective when the program is re-started.
        There is no guarantee that the resolutions listed in the menu
        actually works on your hardware.

Graphics menu: Viewing geometry:
        In order to percieve the correct perspective of the 3D 
        graphics, you must enter correct values here.
        If you do not have an extremely large monitor, or almost touch the
        screen with your nose, you will get a rather limited field of view,
        unfortunately. You can get a bigger FOV by altering the values,
        but this will introduce geometrical distortions, too.
        The default setting is for an unnaturally large field of view,
        typical of what is encountered in most simulators.

Graphics menu: Set landscape drawing distance:
	This parameter sets to what distance to draw the fractal
	landscape out to, between 4 and 10 kilometers, with 8 kilometers
	as defult. There is a difference in frame rate of up to 50% between
	the two extreme settings, so adjusting this parameter may help you
	to achieve a proper frame rate.

Configure calculations:
	Here you state how many iterations of the flight model that is
	performed for each screen update.
	 Calculations are done for a real-time model. The more iterations
	per second, the more precise the model will get. If the intervals 
	between calculations becomes comparable to the dynamic time-scale 
	for the aircraft, errors will be significant, leading to 
	oscillations, eventually making the plane unflyable.
         The onset of oscillations depends on the selected aircraft, but
	generally becomes a problem at high velocities,if the calculation 
	rate goes much below 20 Hertz.
	 On the ground the friction forces on the wheels will require
	more than 50 calculations per second to avoid oscillations.
	As the Harrier is the most sensitive aircraft to this problem, you
	should use this aircraft stationary on the ground when adjusting
	the rate.
         Another symptom of a too low calculation rate is violent 
        oscillations when locked onto the catapult.
	 Of course, you will also want to see what is going on, so 
	the calculation rate will be a compromise between precision and
	frame-rate.
		For 486's, around 5 calculations per update will give
	a calculation rate close to 70 Hz, and 10-15 frames/sec.
	This should be perfectly OK for both precision and vision.
		On 586's, you will have no trouble with precision or 
	frame-rate if you use more than 3 calculations per update. 
		The calculation/frame rate is also strongly depending
	on the selection of graphics detail. For the highest frame rate, 
      use "flat ground" instead of "fractal landscape".
	Only high-end machines are expected to perform properly using
	the fractal ground. Personally, I prefer flat ground for flying on 
      a 486DX2/66.
		The frame-rate and calculation-rate is displayed when
	you exit Vertigo. As the rate displayed is the average for the
	entire run, you will have to exit, reenter and then exit again,
	for a reliable number, if you change the configuration.

Realism:
                If you are having too many difficulties with controlling
        the aircraft, you may want to change the realism settings.
        Here are listed the settings for maximum realism:

        Realistic propeller engine       Active / button in
        Realistic jet engine             Active / button in
        Wind                             Active / button in
        Manual rudder control            Active / button in

Keyboard commands
	Please refer to the menu page, accessible by pressing [ESC].
        The keys are described in the seperate file KEYS.TXT for 
	easy access.
	
	Do not use the "Pause" button! This will confuse the timing of
	the flight model. Use "P" instead.

Head Up Display
        The default color of the HUD is monochrome green. If you want
        a multi-color HUD or to turn the HUD off, cycle between these
        modes by pressing "ALT h".
	 The HUD is similar to what is seen in other simulators:
	The small cross at the centre is where the nose is pointing,
	and is also the neutral point for the control deflection markers:
	red cross for the stick, and red vertical bar for the rudder.
	If your calibration seems OK, you can switch the control markers 
	off (and on again) by pressing [j].
	 If you have entered correct values in the Graphics configuration
	menu, the scale of the pitch ladder and the heading strip should
	correspond to the actual angle.
	 I have taken the liberty to extend the pitch ladder to the
	entire screen, which is probably what we will see with large
	HUDs or helmet mounted displays in the future.
       In the top right corner, angle of attack is displayed in degrees.
	The altitude ladder at the right side is displayed in feet.  
	Negative altitude is red. 005 reads 50 feet. Below the altitude
	is printed in numbers: 0004 reads 4 feet. Note that the altitude 
	is measured from sea-level, and is not indicating your height 
	above the ground.
	 Below that is the vertical velocity in feet per second. Vertical 
	velocity is also displayed by a vertical bar to the left of the 
	altitude ladder. Blue for positive, and red for negative. The bar 
        reaches the end of the scale at 100 fps, marked by a white border.
         If the altitude Above Ground Level is 3000ft or less, the
        altitude AGL is displayed to the lower right. If this gets below
        300 feet, the color will be red.
        If a ground collission is predicted within a few seconds, a "PULL UP"
        message will flash in the center of the HUD. As the prediction is
        very simple, based only on the ground directly below, it should
        be interpreted with caution. Lowering the undercarriage disables the
        warning.
	 The Indicated airspeed ladder is at the left, displaying knots.
        05 reads 50 kts. Below, true airspeed is printed by digits, and
        immediately below that, the Mach number is shown.
	 At the upper left is a g-load meter.
         A marker move around: The flight path marker is drawn as a 
	simple aircraft seen from behind, with body, wings and vertical
	stabilizer. This shows the direction of your velocity vector,
	i.e. where you are going. You may find this to be your most
	important instrument, especially during landing.

Navigation mode
         Above center, a compass tape is displayed. A 'V' arrow marks
        the direction to the selected waypoint.  To the lower right a
        text array provides further information:
        Uppermost to the left is the waypoint number, and to the right
	the waypoint type. Below to the left is the distance in
	nautical miles and to the right the direction to it.
	At the bottom the estimated time to reach the waypoint is
	shown, assuming current speed and course. If this is 100 minutes
	or more, "--:--" is displayed.
        At the very bottom, so low that it will be behind the analog
        instruments if they are displayed, you will find a bank indicator.
        There are tick marks for 0, 10, 20, 30, 45 and 60 degrees of
        bank. If the bank exceeds 60 degrees, the needle will be flashing.

Air to ground mode
         Two gun sight modes are available, depending on air-to-ground
        or air-to-air mode, as shown to the lower left along with the
        number of remaining gun rounds.
	 The CCIP (Continuous Calculated Impact Point) gun sight is a
        larger circle with a dot in the center, shown in A-G mode.
        This predicts where a bullet fired at this moment will hit the
        ground. It only shows up if the flight time of the bullet from
        shot to impact is less than 10 seconds. The calculation is rather
        precise, probably more than is possible in real life.

Air to air mode
         In A-A mode, a "snake" is shown, indicating the path that
        projectiles fired within about the last three seconds would follow.
        If a target is selected, it will be surrounded by a box, and if
        it is within the distance corresponding to the furthest point
        of the snake, a Lead Computing Optical Sight (LCOS) marker will
        be displayed. Placing this circle on a moving target and firing
        is not a guarantee for a hit, as the display lags one bullet
        time of flight behind. So think ahead!
         Inside the LCOS circle, a target range clock is shown. Each
        quarter of a circle represents a distance of 1000 feet.
         At the perimeter of the target box, two markers are shown: The
        line is the target heading reltive to yours, projected onto the
        horizontal plane. If you are on the same heading, the line will
        be above the box, and below if you are on opposite headings.
         The target aspect angle is displayed by a "V". Aspect angle is
        angle between the target heading and the line of sight between the
        target and you. If the V is at the bottom, the target will be seen
        from behind. If it is horizontal, you are looking at the side
        if the target.
         Extending from the center axis marker, a line is pointing
        towards the selected target, also if it is outside the screen.
         Target range (in nm) , closure speed (in knots) and aspect angle
        is written to the lower right.

Instruments
	Instruments normally not shown in a HUD is at the lower section
	of the screen.
         Throttle is displayed in the leftmost box. For the simple jet and
        propelle engine model, the red bar is the actual percentage RPM,
        while the broad green bar is the requested value.
        A yellow "A" is displayed in the middle of the throttle bar when
        auto-throttle is active (F-14 and Lunar Module only).
         For the detailed jet and propeller engine model, a black vertically
        sliding lever is the throttle. If the jet engine has afterburner,
        a number in the middle of the throttle slider indicates the number
        of afterburner stages set to burn.
         To the right of it there is a lever with a narrow blue handle for
        propeller RPM setting.
	 Further right is the flap setting indicator. Red again showing
	the actual position, and broad green the desired.
	 A number of "G"'s indicates the status of the gear. Their positions
	are corresponding to the location on the airframe.
	Gray for retracted.
	Red for moving.
	Yellow for down.
	Bright green for contact with ground.
	When wheel brakes are activated, the symbol changes to a "W".
	 Below, aircraft with air brakes will have the status of the 
	brake shown by a "B" in different colors like for the gear, but 
	with yellow indicating fully extended.
         Similarly, an "H" shows the status of the arresting hook.
	 For the Harrier, a nozzle angle diagram is shown. Angle ticks
	have 15 degrees intervals. Green line for desired angle, red 
	for actual.
         When DLC is activated in the F-14, spoiler deflection is indicated
        by a yellow marker between green middle and limit markers at the
        bottom of the screen.
        Also for the F-14, sweep mode and angle is displayed to the lower
        right by an arrow-like symbol, with "A" or "M" inside to indicate
        automatic or manual sweep mode, and the sweep angle is in degrees
        below.
      In the right corner, trim settings are displayed, using red marks on
      a grey cross resembling an aircraft. The tick on the vertical line
      displays elevator trim, on the long upper horizontal line, aileron
      trim, and on the lower short horizontal line, rudder trim is shown. 
	 Flying simpler aircraft like the Corsair and Supporter feels
	more realistic with the HUD off, which is the default mode for these
        aircraft. You can cycle between the HUD off mode and different
        color modes by pressing [ALT h] .


       At the bottom of the screen, a few "real" analog instruments are
      shown. The lay-out is in most cases inspired by the Supporter
      cockpit instruments.
      All aircraft:
       Artificial horizon:
        Displays pitch and roll. Shortcomings:
        Makes a unrealistic "flip" at zenith/nadir, and the numbers look weird.
        Cannot be tilted by nasty maneuvers.
       Airspeed:
        This displays indicated airspeed in knots.
       Vertical Velocity Indicator:
        Behaves ideally, i.e. no lag or altitude influence.
        Unit: Thousands of feet per minute.
       ILS needles:
        Works like those on the HUD. A red flag is visible when the ILS
        is inactive.
       Compass:
        Looks like a magnetic compass, but has no of the effects implemented
        that makes magnetic compasses tricky.
       Accellerometer:
        Displays G's pulled. Narrow needles indicate max/min load during
        the flight.
       Altimeter:
        Has a needle that turns once per 1000 feet and a digital display
        showing hundreds of feet. 
        Altitude based on air density is shown, *not* height over ground!
        Air pressure is always 1013 HPa at sea level in this simulation,
        so the altimeter does not need adjustment.
       Turn and slip:
        Consists of a ball, ideally supposed to show yaw, but in reality
        showing the ratio of acceleration in the aircraft's horizontal axis
        to the acceleration in the vertical axis. This means, that change in
        g-load and changes in rudder input, for instance, will also affect
        the position of the ball.
        The needle above shows the angular speed around the vertical axis,
        in arbitrary units.
       Fuel level:
        This twin dial shows the fraction of internal fuel left.
       Gear position indicator:
        The coloured of a letter for each wheel indicates the position:
        Dark for up, yellow for moving and green for down. Also airbrake and
        hook position are shown.
       For the VVI, IAS and ALT indictors, a delay in response time is
       modelled.
      Propeller engine only:
       RPM dial:
        Units are 100's of Rounds Per Minute.
       Manifold pressure:
        I'll have to work a little on this still to display proper values,
        especially at low RPM.
        Units are inches of Hg.
       Fuel flow:
        Units are gallons per hour.
      Jet engine only:
       These instruments are made to resemble the lay-out in the F14 as
       much as possible, with some modification to make them useable for
       single engine aircraft also.
       RPM percentage:
        A vertical strip shows the RPM, in units tens of percent of the
        military throttle RPM. The scale is in two segments in order to
        give more precise readings above idle RPM.
       Exhaust Gas Temperature (EGT):
        This two-scale vertical strip instrument shows the EGT in
        units of tens of degrees Celcius.
       Fuel flow:
        This two-scale vertical strip instrument shows the fuel flow
        to the combustion chamber in units of thousands of pounds per
        hour. The fuel flow to afterburners is not shown. 
       Map:
	 The only head-down instrument is a map, continuously updated to
	be centered on your position and rotated to your heading.
	View by pressing "m" and zoom in/out by pressing "+" and "-" on
	the keypad. Zooming out to draw a large portion of the map will
	make the computer extremely busy, which will mean less time to 
	perform flight model calculations. This may lead to unstable aircraft
	behaviour while you are looking at the map, so be careful!

Scenario
	Although the graphics is very simple, most of the time is spent 
	on drawing. To allow for precise flight model calculations, 
	graphics has to be kept at a minimum.

        Two scenarios are available: Earth and Moon landscapes. 

	Two types of landscape can be selected from the 
	Configure graphics => Landscape type menu.
	Flat:
         The ground is simply a green flat surface, with a blue sky above.
        The ground within 10 kilometers of the viewer is marked by
        a grid of brown lines. The side of a square is 1 km.
        Within 1 km of the viewer, another gray grid marks the ground.
        The side of a gray square is 100 m. 
	Fractal: 
	 This generates a random fractal mountain-landscape, with
	water at sea-level. The surface is drawn using triangles, whose
	shortest lines are 1 km. You will have to judge, if you can
	accept the decrease in frame-rate compared to the flat landscape.
	See the "Set landscape drawing distance" section to optimize this
	mode.

         The runway orientation is 00-18, and is 1500m long, 40m wide.

         In the sea, an aircraft carrier moves about. See the description
        further down.
      
        The Moon landscape is all grey, with hills and plains. There will
        always be at least a 1km square flat area at the intended landing 
        site. The most important difference is of course the atmospheric
        pressure of zero and the weak gravitational pull on the Moon.

         Illumination changes with the time of day. From the menu, day,
        night, dawn or dusk can be selected. During dawn and dusk, the
        lighting will change between day and night condition during half
        an hour. As the time since program start is added to the time
        selected in the menu, delecting dawn or dusk after a long flight
        may result in instant day or night.
         During nighttime, the runway and carrier will be marked by
        artificial lights.
         Almost all stars visible to the unaided eye will be displayed
        in the night sky. The orientation of the sky can be set by
        specifying the local latitude and the sidereal time in the menu.



Flight model

The aircraft is modelled as a combination of objects. For each object,
the forces acting on it are calculated, and from the object's position
relative to the centre of gravity of the entire set, resulting force and 
torque is calculated. By measuring the real time elapsed, the forces are 
translated to new vector and angular velocities for the airframe.

For each object the velocity and angle of the incoming air is calculated
from the attitude and speed of the aircraft, also taking into account
the angular velocity of the airframe. For instance, the airspeed of the
outer wing is influenced by yaw rate, and the AOA is influenced by
roll rate.

The group of objects, on which aerodynamic forces (lift, profile- and 
induced drag) are calculated typically consist of body, port/stb. inner
wing, port/stb. outer wing, horizontal and vertical stabilizer, totalling
7 objects. The properties (chamber, geometric AOA, area) of the relevant
objects are changed according to control input. E.g. the properties of the
two outer wing sections are modified by aileron input. The forces
are calculated from the empiric equations in basic aerodynamics textbooks.

The density of the atmosphere decreases exponentially with altitude,
and the temperature decreases linearly up to the tropospause, and
is constant above that.

On objects representing undercarriage, the only aerodynamic force 
calculated is profile drag. Forces on the wheels when on the ground 
distinguish between static and dynamic drag, and include rolling friction.
ABS-type brakes are implemented, so skidding along the rolling direction
will only occur if you also skid sideways.
Forces are calculated parallel and perpendicular to each wheel, making
steering possible, as the angle of one of the wheels is connected to the 
rudder input.
The spring forces in the upward direction are damped.
In addition, hard-points are at nose- tail- and wing-tips. These only
provide friction-drag and spring forces from the ground.
There are certainly still some shortcomings in the calculation of ground-
friction forces. While of limited precision during fairly normal attitudes,
they are completely wrong if you are inverted (You are also doing something
completely wrong, if you encounter that situation!)
If you go for a drive in the fractal landscape, you will find that the
wheel forces are not calculated correctly on non-horizontal surfaces.

For aircraft having hydraulic actuators for the control surfaces, the
rate of movement has an upper limit to emulate the response time.

Fuel tanks are located in wings and body, affecting aircraft weight and
inertia. Typically, the wing tanks are emptied before the body tanks
are used.

All objects, except hard-points are affected by gravitational forces.

 Auto-coordination can be activated, controlling rudder position to
minimize yaw. As this only can correct for yaw appearing, not anticipate
it, a small amount of yaw will still be present. Also, the rudder has
limited effectiveness, so you can enter a situation where a large amount
of yaw still occurs.

The aircraft are all conventionally stable: Any pitch and yaw will tend
to be eliminated without any control input from the pilot. The stability
combined with inadequate damping of the motion around the equilibrium
position appears as a "nose bounce" for some aircraft. You can minimize
the bounce by applying smooth stich movements and keep the aircraft in
trim.

Propeller and jet engines comes in two types: Simple force generators and
more detailed models described below.


Propeller engines
In the detailed version of the propeller engine, ehe engine is a torque
generator acting on the propeller. The amount of torque depends on the
throttle setting, RPM and air desity. Torque will typically try to increase
the RPM of the propeller, but at high RPM and low throttle, the engine will
act as a brake.
 The propeller has mass and rotates rapidly. Torque on the propeller
from the engine will inflict the opposite torque on the airframe and
the rotating mass will act as a huge gyroscope, turning the airframe
in a direction perpendicular to the direction that the airframe tries to
rotate the propeller.   
 The propeller is a rotating wing. The angle of attack of the propeller
depends on the blade pitch, RPM, position angle and radius on the 
propeller disc, airspeed, airframe pitch and yaw and the inflow and vortex 
airspeed. This results in pretty complex behaviour of the resulting
lift and drag vectors. These can be split in directions along the propeller
axis and perpendicular to it, resulting in thrust and drag acting as torque.
In addition propeller thrust and torque also depends on air density.
The actual lift and drag coefficients are derived from wind tunnel data
for the NACA0012 profile.
  Because of airframe pitch and yaw, the thrust is changing over the
propeller disc, causing asymmetric thrust, known as P-factor.
  The propeller thrust accelerates air backwards and the drag/torque
creates a vortex. The flow is partially absorbed by the body and wing
root, but some of it hits the tail surfaces. This increases control
efficiency at low speed, but the vortex hits at an angle, causing
a yaw moment that must be countered by rudder input.
 As the effective angle of attack and depends on airspeed, the propeller 
thrust efficiency is strongly depending on airspeed too. To expand the 
range with good thrust and efficiency, the propeller pitch can be changed. 
The pitch is adjusted by a servo mechanism to result in a fixed RPM. The
desired RPM can be set by the pilot.
 The Corsair engine has a two speed auxiliary blower in addition to the
constant speed supercharger. The blower operates in idle at low altitude
and at two speeds at higher altitude, controlled automatically. Also,
a 2:1 reduction gear between engine and propeller is implemented.

Jet engines
In the detailed version of the jet engine model, the throttle position
sets the desired RPM percentage, with a maximum RPM of 100%.
The thrust depends on RPM, altitude and airspeed. There is a slight
decrease in thrust at moderate airspeeds as the exhaust speed is
nearly constant while the intake airspeed increases. At higher airspeeds,
ram-effect helps the compressor, and thrust increases with the square
of the speed. At very high speeds, thrust may be limited by variable
air intake ramps, as for the F-14.
The RPM response speed degrades with altitude.
Fuel consumption vary with RPM setting and decreases with altitude.

Afterburners can be lit gradually, e.g. the F-14 has five burner stages.
The fuel consumption at full afterburner is about five times higher than
at conventional thrust, and giving only about a two-fold increase in thrust.
Note that the fuel flow to the afterburner will not be shown on the FF
instrument, but it will be seen after a short while on the fuel level gauge.
The afterburner throttle is indicated by a number in the middle of the
throttle handle slider.

A compressor stall may be started by poor intake airflow or a too high
combustion chamber pressure. The symptoms will be a sudden drop in thrust,
very high exhaust gas temperature, and dropping RPM. Provoking a compressor
stall may be done by a combination of high AoA or yaw, low indicated
airspeed, high throttle setting or advancing the throttle too fast.
The cure is to reduce throttle to idle and reduce AoA.

Flame outs also show the symptoms of a drop in thrust and RPM, but is
distinguished by a drop in EGT too. Flame outs may be started by flying
at very high altitudes or reducing the throttle too fast at high
altitudes. Also recovery from a compressor stall may lead to flame out.

Engine air restarts are initiated py pressing "e". For a succesfull restart,
go to moderate or low altitude and pick up speed to windmill RPM to a
useful range. Do not apply throttle too abruptly, or you will stall the
engine during the restart.

Rocket engines
The rocket engine is, at least in principle, the simplest of the three 
modelled types of engines. 
Thrust is proportional to the amount of fuel and oxidizer pumped into the
combustion chamber, regulated by the throttle.
The engines modeled for the X-15 and Lunar Module both have a considerable
thrust even at idle throttle. To toggle fuel flow and ignition, press "e".



Weapons

It was with mixed feelings that I started to implement weapons on 
aircraft in Vertigo. Violence is being glorified by a huge part
of the entertainment industry, and I believe this is contributing to
increasing violence among people.
Please, never forget the cruelty of war, whatever enjoyment you may have
from strafing the targets.

So far only cannons are implemented, as these are my idea of the weapon of
a classic ace.
Each gun has a limited amount of ammunition and a specific rate of fire.
The trajectory of projectiles are influenced by:
  Initial velocity: The sum of aircraft velocity and muzzle velocity. (You 
  will then have a slightly larger gun range when flying fast.)
  Gravity.
  Drag: Depending on speed and altitude.
  Mass: A heavy projectile will be less influenced by drag.
  Gun pointing, not necessarily parallel to the axis of the aircraft.
  Barrel imprecision: A small random angle to the pointing is added.
With all these factors, you will be happy to have the CCIP/LCOS gun sights 
described in the HUD section.
In turn, your aircraft feels the recoil from the guns. You may even 
utilize this for maneuvering on the ground!
Bullet impact is only checked for the ground and the practice targets.
Up to 500 individual trajectories are calculated at one time - if you 
fire very long salvos, you may have to let go of the trigger to 
allow some bullets to impact before you can shoot again.
Note, that long salvos may also reduce frame rate on other than high-end 
computers.
Only one bullet per gun can be fired for each calculation iteration.
If, for instance, your calculation frequency is less than 100 Hz, you 
will not be able to utilize the full fire power of the 100 rounds/second
gatling in the Starfighter.
A fraction of the projectiles are displayed as tracers, about one in three
for fast firing guns, and a higher ratio for slower guns. The tracers
cease to burn after five seconds, but the flight path of all projectiles
is calculated for 15 seconds, after which they are ignored.



Targets
You can hone your gunnery skills at a target range close to the airfield,
with a suitably named waypoint.
The targets are red and white diamonds that will withstand 10 direct
hits before they burst. With a diameter of about 4 meters, they are
quite difficult to hit.
One target is placed on the ground. Beware that you can see it through
a hill, but you can't fly through the hill.
Four targets circle at random altitudes, speeds and g-loads.
To lock on to the next target, press "SHIFT t".
To get external and internal padlock views, press "/" and "*".


Selectable aircraft

From Main Menu, under Select aircraft, you find six aircraft:
F-14A Tomcat, F-104 Starfighter, U-2, F4U Corsair, Harrier and
MFI-17 Supporter.

Do not be fooled by the precise naming of these models. The models
only have a very vague resemblance to the real aircraft.
For most of the aircraft, I have just entered crude overall sizes,
weight etc. from the one-page descriptions that can be found everywhere.
I have only little specific data to allow for a precise simulation of any
aircraft.
- I would be grateful to be provided with them though!
Comparisons of the performance of the models with the real thing are very 
welcome.
Among the reasons for choosing an aircraft to model are:
Unique aerodynamic properties (goes for the Harrier, U-2, F-14 and F-104),
engine properites: Corsair and sentimental reasons: Supporter.
A fair chance of proper modelling - You will not find dynamically unstable
fly-by-wire aircraft and other complicating matters - at least not yet...

Grumman F-14A Tomcat:
The Tomcat has in several ways a unique design, caused by the requirements
for a fleet defence aircraft: High speed, long patrol time, high payload,
low landing speed and good maneuverability. This is accomplished by
using variable geometry wings and other features, which are elaborated
on below:

Variable sweep wings:
  Sweep is controlled as a function of the Mach number. At low speed,
  sweep is at a minimum of 20 degrees to minimize induced drag.
  From about Mach 0.7 to 1.2, sweep is gradually increased to 68 degrees to
  minimize supersonic drag. 
  Increasing sweep moves the center of lift backwards, which decreases
  maneuverability.
  Sweep can also be controlled manually by using keys F9 to F12. Key "s"
  toggles between manual and automatic mode. Mode and sweep angle is
  displayed to the lower right by an arrow-like symbol, with "A" or "M"
  inside to indicate sweep mode, and the sweep angle in degrees below.
  At sweep angles larger than 55 degrees, flaps and spoilers will be
  retracted.

Glove vanes:
  Above Mach 1, the center of pressure moves backward, although this is
  not yet implemented in the flight model. This means a larger down-force
  on the elevator is required, creating more trim drag. To counter this,
  glove vanes are extended at Mach 1.4. This moves the center of lift
  forward, which in turn means less drag.

Tailerons and differential spoilers:
  As ailerons work badly in combination with variable sweep, the aileron
  function is moved to the tail. At sweep less than 55 degrees,
  differential spoilers on the upper side of the wings assist roll control.
  On the wing going down, the spoiler is extended, while it remains flush
  on the other wing. This method has the advantage of counteracting
  adverse yaw.

Landing:
  The Tomcat can be landed as any carrier-based aircraft, by fiddling
  with throttle and stick. Airspeed will be in the range of 115 to 145
  knots depending on fuel load, but the optimum AoA is always 10.8 deg.
  However, another way to land is to use the following two features:
  Auto-throttle:
    Toggle auto-throttle by pressing "t" while the throttle is about halfway
    forward. Now the engines are controlled by a servo mechanism reacting
    on the aircraft angle of attack. If AoA is less than 10.8 deg, you
    are going too fast and throttle is reduced, and vice versa.
    Auto-throttle can be disengaged by moving the throttle handle to idle
    or full power.
    A yellow "A" is displayed in the middle of the throttle bar when
    auto-throttle is active.
    Unfortunately, I find the auto-throttle very hard to use. Maybe
    I will manage to tweak it to behave nicer.
  Direct Lift Control:
    With constant airspeed and AoA, the way to control your position
    on the glideslope is to change the amount of lift by controlling the
    spoiler deflection.
    When gear is selected down and brakes out, DLC is activated.
    The spoilers deflect to a middle position of 7 degrees, and deflection
    is adjusted by pressing "q" for more lift and "a" for less lift.
    As the tomcat in this version is near minimum weight, you will need
    a quite large spoiler deflection to stay on the glide slope.
    Also when landing by stick and throttle only, it will be a good idea to
    set the DLC to an appropriate value.
    When DLC is active, spoiler deflection is indicated at the
    bottom of ths screen.
    Retracting the air brake will disengage DLC.
    At touchdown, the spoilers will move to a maximum deflection of
    55 degrees in order to avoid bouncing off the deck.
    Again, retracting air brakes will retract the spoilers.

Dual engines:
  The A-model Tomcat is generally considered under-powered. As this model
  is not loaded with external stores, that will not be a big problem.
  A single engine failure makes for an interesting flight due to the strong
  yaw produced by the remaining working engine.
  If you are not careful, you will end up in the notorious flat spin.
  An engine failure may be initiated by pressing "F", or by tormenting
  the engines. Especially, a yaw will make the engine in the turbulence
  from the nose prone to a compressor stall.

Armament:
  One 20mm M-61 gatling cannon with 675 rounds. 

There are a lot of books about the Tomcat - the one I like the most is:
  Aviation fact file: Modern fighting aircraft: F-14
  By Mike Spick
  Salamander books, 1985
  ISBN 0 86101 194 5

British Aerospace Sea Harrier:
Weight allows for VTOL.
Features vectored thrust and jet-supported attitude controls.
A ground cushion effect kludge is added. This increases vertical thrust 
gradually to 120% at 1 meter altitude.
New versions of the Harrier has gyro-stabilization to make hovering easier. 
In this simulation, you do not have that luxury.
It will probably take some practice to make this thing do what you 
actually planned to, when hovering.
Carrier landing configuration:
  You have no tail hook and will be ignored by the LSO.
  Use thrust vectoring for landing.
Armament:
  Two 30mm Aden cannons, with 130 rounds per gun.

Lockheed F-104 Starfighter:
Weight is as with tanks almost empty.
Stay fast!
Paint scheme inspired by USAF F-104N used for astronaut training.
Carrier landing configuration: 
  Yep, I know a real F-104 would never survive this.
  Fly the glide slope at +9.0 deg AoA. 
Armament: 
  One 20mm M-61 gatling cannon with 725 rounds. 
  Fires 6000 rounds/minute.

Lockheed U-2:
The single main gear is located well in front of the centre of 
gravity, so when the tail-wheel rises, you are in a very unstable
situation. I suggest you keep the tail wheel on the ground as long as
the main wheel is touching ground too. 
I recommend reading the section by Tony LeVier at the end of chapter 6 in
Ben R. Rich and Leo Janos' "Skunk Works" about landing the U-2.
No drop-off wheel struts at the wing tips during take-off, so be careful!
The real aircraft is extremely fragile, so this this will be really 
interesting to fly if I ever get to implement stress limits.
The engine is very powerful. Implementing altitude dependent engine
effectiveness would be interesting, as it only delivers 7% of the power 
at sea-level when at 70000ft.
Carrier landing configuration:
  +3.3 deg AoA.

Vought F4U-1 Corsair:
The 2000 HP R-2800-8 propeller engine provides tremendous power, but also
torque, asymmetric thrust, gyroscopic forces and slipstream vortex,
making this a very challenging aircraft.
If you select the realistic engine model, rudder pedals are
strongly recommended. If you don't have pedals, enable auto-coordination.
Be careful not to nose-over when using the wheel brakes.
The supercharger has an auxiliary blower that is operated automatically at
three speeds, depending on altitude:
  Neutral:     0 -  8000 ft
  Low    :  8000 - 13000 ft
  High   : 13000 -       ft
The blower setting is indicated by a letter on the throttle slider.
Carrier landing configuration:
  +6.0 deg AoA.
  The long nose will make it difficult to see the carrier during approach,
  but you can cheat by selection not to display the airframe from the
  cockpit.
Armament:
  Six 0.50 in machine guns 
  with 400 RPG (inboard four) and 375 RPG (outboard two).
  Convergence is set to 300 meters.

SAAB MFI-17 Supporter:
A small propeller aircraft used for basic training, reconnaissance and 
logistics by the Danish and Norwegian air forces, and even as a light attack 
aircraft by the Zambian and Pakistani Air Force.
This is the easiest aircraft to fly of those included, so if you are new
to Vertigo, you should start with this one.
Carrier landing configuration:
  +5.5 deg AoA.
  You have no tail hook, so step on the brakes when landed.
Armament:
  Although it has six weapons stations, no weapons are provided in
  this simulation.

Dihedral demo:
This model is based on the SAAB MFI-17, but is altered to test upgrades
of the flight model. The graphics is unchanged, but the flight model
is quite different.
As a new feature, wing dihedral can be specified, and this model has
a positive dihedral of 15 degrees. This creates a rather strong roll
stability.
Ailerons and flaps are disabled, but roll can easily be controlled
by the rudder due to the roll-yaw coupling that results from dihedral.
The vertical tail fin is made too small, making yaw stability much
smaller than roll stability. This makes it possible to demonstrate the
"Dutch roll" by kicking the rudder briefly.
The wing lift coefficient is as for a NACA0012 profile.

North American X-15A-2:
The X-15 was a hypersonic and high altitude research aircraft, that flew
from 1959 to 68. It provided essential information that made building the 
Space Shuttle possible. The second of three X-15s built, was modified to the 
X-15A-2, capable of carrying external jettisonable fuel tanks, which are 
not modelled in this simulation.
Dropped from about 50.000ft from a B-52, the flight profile may be relatively
flat, aiming for high speed, or steep if high altitude is desired.   
Without external tanks, the highest speed reached was 3565 knots TAS and the
highest Mach number 6.06. The highest altitude attained was 314.750 feet, well
above the boundary defined as space.
You may easily beat the altitude record in the simulation, but that would
likely mean a steeper re-entry that what was used, possibly over-stressing
the airframe. The steepest re-entry flown was -38 degrees, with an angle of
attack up to 26 degrees.
At extreme altitudes, the airflow will be too weak to provide adequate 
attitude control. Pressing "r" will toggle the activation of a Reaction Control 
System that will enable you to control the aircraft outside the atmosphere. 
When you leave the B-52, your airfield will be 175nm ahead of you. After
flying your research profile, you will have to glide back to a landing there. 
This is also a tribute to the guys from Argonaut Software that made Birds Of 
Prey back in 1992, including an X-15 simulation that I enjoyed a lot.

Grumman Lunar Module-5 "Eagle":
The Lunar Module was used in the Apollo missions for the first manned landings
on the Moon.
In this simulation, you can pilot the LM down from the "Low Gate" point to
touchdown. Low Gate is at a height of 500ft above the surface. The velocity
of the LM should at this point be 21 m/s forward and 5 m/s down. The amount of
useable fuel aboard has been reduced by the de-orbit maneuver from the original 
8164kg to 522kg, so there is not much left for loitering around.
Using throttle and attitude thrusters, guide the LM to a soft landing.
An auto-throttle function can be toggled by pressing "t". This will aim at a
descent rate of -1 m/s. During the descent, you will hear actual radio 
transmissions from the "Eagle" landing on 20 July 1969 at the appropriate
heights. At a height of 2 meters, you will get the "Contact lights" report,
and you may choose to turn off the engine by pressing "e", or continue down
under power.
Thanks to H. Frik for making the beautiful graphics for the LM descent
stage. It is by far the most detailed object in the entire program. He also
provided lots of data and sound files for the LM simulation.


Carrier landings

Maybe the greatest challenge in modern aviation is to land safely aboard an 
aircraft carrier. Here you get to practice clear weather day or night time
landings.
 
 The Carrier:
On startup, a Nimitz class carrier is placed somewhere in the sea. 
The deck will pitch, roll and heave proportionally to the strength of the
wind. You can select several locations relative to the carrier at startup:
 On deck: You will be placed ready for take-off, but you will have to do it
without the catapult.  
 On final: You will be placed in landing configuration on the glide slope a
few miles out.
 Approach: You will be placed behind the carrier several miles out and you
will have to put yourself on the glide slope.
You can of course also start from the runway and find the carrier, which will
be at the appropriate waypoint.

 LSO:
If you are approximately on the glide slope, the Landing Safety Officer will
establish contact when you are 3/4 nautical mile away from the deck.
At this point, the LSO will expect you to have gone dirty, i.e. lowered 
gear, hook and flaps.
You answer by telling aircraft type, that you have the ball in sight and
the amount fuel left in thousands of pounds.
You will then be guided by voice until you are safely down, or "waved off" if
the approach is unsafe. 

 Meatball:
At a distance of about two miles, the Optical Landing System will become
visible, located mid-ship on the port side. The arrangement looks like this:

            R   Y   R
            R   Y   R
  G G G G G R   Y   R G G G G G
            R   Y   R
                R    
 
The R, G, Y letters marks lamps of red, green and yellow color, respectively.
The yellow and red lights in the central column are made using a Fresnel lens 
system so that each light emits an approximately 0.5 degree wide cone in the 
vertical range and much broader horizontally. These lights make up the
"meatball".
Each lens is tilted so that if you are above the glide slope, you will see
one of the upper lamps and if below, the lower lamps. The lowest lamp is red
to warn of this dangerous situation. If you are within 0.15 degrees of the
glide slope, the lamp aligned with the green "datum line" will be visible -
you are on the correct -3.5 degree glide slope.
If you are deviating 1 degree or more vertically, no meatball will be
visible - you will have to eyeball what is wrong, use the ILS or listen to
the LSO.
At large distance, the position of the ball can be hard to see as the
entire arrangement just takes up a handfull of pixels. I have made the
vertical offset of the meatball larger than in reality to compensate for
this.
If you keep the ball centered, you will touch down with the hook hitting the
deck between the second and third wire, thereby catching the third wire.
As the vertical separation between the hook and your eyes is different for
the different aircraft, the height of the meatball has to be adjusted
accordingly. This is being done by rolling the lights a few degrees -
as you are sideways offset to the lights when in the groove, this will look
like a vertical displacement of the lights - beware that if you are not lined
up, the meatball will give wrong information, e.g. place you too low if you
are port of the centerline.
The entire OLS arrangement is gyroscopically stabilized, to avoid ship
movement affecting the glide slope indication. The stabilization can not
eliminate the vertical motion, though, so a pilot with a steady hand may be
able to notice a slightly oscillating meatball.
The two vertical rows of red lights are used for signalling "wave off".
 
 Lining up:
To line up visually, examine the center line painted on the deck and
continued vertically down at the rear. When lined up, the two line segments
must both appear vertical. Note that due to crosswind, you cannot just
place the HUD flight path marker on the center line. 
 
 Approach indexer:
Each aircraft has a specific angle of attack to maintain when on the
glide slope, providing high lift safely below the stall AoA.
The airspeed is closely linked to the AoA: If you are fast but following
the glide slope, the AoA will be too low and vice versa. The optimum
airspeed changes with aircraft weight, while the best AoA remains the
same, so if you keep the prescribed AoA and stay in the groove, you
(almost) don't have to think about the airspeed.
The AoA to be used is listed in the aircraft descriptions above.
The indexer is located in the mid-left part of the HUD, and will be visible
when HUD is on and gear down.
If the AoA is too large, the upper red downward pointing arrow will illuminate.
If AoA is too small, the lower green upward pointing arrow will light up.
Correct AoA will be marked by a yellow ring in between the arrows.

 ILS:
The Instrument Landing System displays a horizontal and a vertical needle,
at the center of the HUD, measuring line-up and glide-slope error, respectively.
At full stroke, the needles show you are 3 degrees off.
The type of ILS modelled here is a part of the modern Automated Carrier Landing
System, which eliminates ship roll and pitch from the signal, as well as
parallax angle to the antennas.
The ILS is not intended for daytime clear weather use, so when you get 
confident, try landing without it by switching to navigation mode (press "n")
instead of ILS mode (press "i"). 

 Landing grades:
Each landing attempt is graded by three values: The wire number caught, 
a classification and a score. The LSO will evaluate the score on your flying
from the moment he asks you to call the ball and until you catch a wire or
are waved off.
 Wire number: Catching the number three wire is the ideal, while number two
and four are acceptable. Catching the #1 wire may be a symptom of a dangerous 
situation where you were too close to the ramp.
 Classification     Score              Description 
     _OK_          4 points        Perfect!
      OK           4 points        Small deviations corrected by pilot.
     (OK) / Fair   3 points        Deviations usually corrected without LSO
                                   calls.
     No grade      2 points        Large deviations requiring LSO help.
     Cut pass      1 or 0 points   Unsafe pass - may have resulted in damage
                                   or injury without LSO help.
     Wave off      0 points        Landing aborted by LSO because of pilot
                                   error.
     Bolter        0 points        All wires missed.
In addition, out of the context of carrier operations, some statistics on the 
the individual types of deviations are given, in the form of Root-Mean-Square
error.
Also, a floating point "overall score" is given. A bonus is given for
switching off ILS and/or HUD before calling the ball. For each of the
realism options that are set for max. realism, a bonus is also given.
The maximum possible score is 10.0. I will keep a "Sierra Hotel" table
of the best landings on the Vertigo homepage.
To submit a landing score, mail me your name, the score, aircraft type,
HUD and ILS on/off status, realism menu options and the four letter
validation code printed below the score. 
Press "p" for a pause to study the landing debriefing.

 Landing pattern:
Selecting "Carrier: On final" sets you up for a straight-in landing, but in 
day-time and clear weather, a landing pattern is the correct method.
A pattern is flown by passing the carrier at 800 feet in the upwind direction,
where you will be ignored by the LSO, turning left and starting a slow
decelleration and descent, turning downwind and going dirty, turning base leg
behind the carrier and turning to arrive on final at 350 feet altitude,
3/4 of a mile beind the carrier and on approach speed, to be asked to
"call the ball" as you come out of the turn.
Due to the limited sense of spatial awareness possible in this simulator,
flying a pattern will be quite difficult. The waypoint padlock will
probably be helpful.

 Wind:
The carrier will be heading into the wind at a speed resulting in 25 kts of
wind down the deck. If the natural wind is more than 25 kts, this will not
be possible, and you will have stronger wind, regardless of what you are told
on the radio!
The landing strip is angled 9.2 degrees relative to the deck, so you will
have a slight crosswind from starboard. 
The carrier will maneuver to avoid ground, so the wind relative to the deck
may change. If you want to create more difficult landings, go to the menu and
switch wind off and on again - the wind will now be of a different strength
and direction.

 Trapping:
The wire force is set for each aircraft. The Corsair and U-2 will be
decellerated at 1G, the F-14 at 2G, and the F-104 at 3.5G, which would
probably rip it apart in the real world. When you come to a standstill,
you can raise the hook and take off under your own engine power only, 
or if you are in the F-14, you can proceed to the catapults.

 Credits:
The carrier landing simulation would never have been possible without the 
generous and competent advice from:
Cole Pierce (gun one), Mike Yukish, Chuck Kilogre, Bill Horne, 
Pete B. D., Tom M. Olivier, Jim Muse, John Simon and those I forgot in the 
hurry.
Thank you! 
Information for making the simulation more precise is always welcome.

Catapult launches

The four catapults on the aircraft carrier can be selected as
starting position in the menu - you will be assigned a random one,
or you can taxi onto a catapult from the deck.
Taxiing will have to be done extremely precisely and slowly, if you
are to be attached to the catapult. Normally, a "yellow shirt" would
guide you, but here you are on your own.
Behind you, the jet blast deflector will rise.
To launch, apply full throttle and go into afterburner. If you are using
keyboard for throttle control, first press on F4 will take you to full
military throttle, and subsequent presses will light the burner stages.
After a few seconds, the cat will fire. 
You will be pushed forward with an acceleration of approx. 2G.
Only aircraft properly equipped can be launched, which means the
F-14 Tomcat only.
If you experience oscillations when locked to the catapult, increase
the calculation rate in the graphics menu.




  Other things to try
  As you probably have found out by now, there are no missions. So how come that 
  I still do not find it completely uninteresting to fly this thing after a 
  couple of carrier traps and some targets destroyed? Below are listed a few 
  things, that I find funny to try: 
  Test piloting: 
    Take the aircraft and the flight model to the limits and find out how it 
    behaves. Compare with the performance of the real aircraft, if you have the 
    data, find out where the realism of the flight model fails. I'll be happy to 
    hear about your results. 
  Radio-controlled flight: 
    Viewing from the tower, you can fly in a manner similar to R/C flight. Be 
    sure to select a fairly slow aircraft with a small turning radius. You will 
    easily get confused interpreting the attitude of the aircraft, but this is 
    also experienced in real life in difficult lighting situations. 
  Aerobatics: 
    You can perform a wide range of aerobatic maneuvers, including some that 
    involve stalling. 
  Spins
    A stall may develop into a spin, especially if aileron and rudder input is 
    given to provoke it. The tendency to spin varies greatly between the 
    aircraft. Mainly because of their relatively short wings, the Starfighter 
    and Harrier tumbles rather than spins. The U-2 takes a lot of work to spin, 
    but when it gets going, it will be even harder to stop. The F-14 can be 
    spun, if strongly provoked, but shutting down one engine causes a high risk 
    of entering a flat spin. The T-17 spins easily and recovery is effortless. 
    The Corsair is very prone to enter a spin that may easily become flat and 
    tough to get out of.
    Recovery from a spin depends on a lot of factors, but roughly goes as this: 
      Flaps: Up 
      Throttle: Idle 
      Stick: Center, or a little forward 
      Rudder: Opposite rotation until it stops 
      Pull gently out of dive when airspeed is sufficient. 
  Landing: 
    The skills of a pilot is often judged in the smoothness of the landing. When 
    you routinely can bring the Starfighter to a stop before the end of the 
    runway, you are getting the hang of it. 
  Hovering: 
    A very difficult exercise is to practise vertical take-off and landings in 
    the Harrier. I believe the simulation is more difficult to handle than the 
    real Harrier, due to less stability and poorer awareness of your attitude. 
  Taxiing: 
    Aircraft are often quite clumsy on the ground, so high-speed taxiing can be 
    a challenge. 
  Strafing the tower: 
    Check your aim by switching to tower view immediately after firing. 



Flight data logging
For a detailed analysis of your flight, you can record many data parameters. 
Logging is toggled by the key "SHIFT l". The data are recorded in a file named 
fdata###.log, with a number increasing for each log created. Data are stored as 
plain text, and may be loaded into spreadsheets etc. The logging frequency is 
1Hz. A line is entered with the following data seperated in columns:
Time (s)
Aircraft x, y and z coordiantes (m)
Angular speed around x, y and z axis of aircraft (rad/s)
Vertical velocity (m/s)
TAS, IAS (kts)
Mach number
Angle of attack and yaw angle (rad)
Acceleration along x, y and z axis of aircraft (m/s/s)



Tips for beginners
There is really no need to make it too difficult for yourself in the beginning. 
These are the suggested options for a gentle start: 
Aircraft: MFI-17 Supporter.
Realism: Wind and realistic propeller engine: Off.
Graphics: Landscape type: Flat.
Press "ALT h" to get the head-up display.
Make sure that you have a quite large field of view, e.g. set the viewing 
distance to about half of the real value in the graphics menu. 



Version history
August 1995: Version 0.10
First release.

December 1995: Version 0.11
Fractal landscape added.

More details around the airfield.

Ground forces on wheels calculated in more detail.

Profile drag dependence on flap deflection included.

Some trimming on aircraft models, especially the Harrier.

SVGA graphics drivers removed because of poor performance.

March 1996: Version 0.12
More detailed rendering, with hidden surface removal.

Air brakes for the jet aircraft.

Quick joystick centering for those of us with a cheap game card.

Vought F4U Crusader, with more graphic detail than previous models.

Machine guns on aircraft.

CCIP gun-sight.

Pause mode.

Position lights on some aircraft.

Status line in external view.

May 1996: Version 0.13
More detailed rendering of the Harrier and the U-2

July 1996: Version 0.14
Filled polygons with light source shading for aircraft and landscape. 
All aircraft are now drawn using polygons. 
SAAB MFI-17 Supporter added. 
The generic aircraft models removed. 
Display of HUD [h] and controls position [j] can be toggled. 
Clean exit from floating point errors - reboot is still recommended, though. 
September 1996: Version 0.15
Video page flipping flicker eliminated. 
Less time spent on objects and terrain outside the field of view or far away. 
Undercarriage less hysterical about low calculation frequencies. 
November 1996: Version 0.16
First release compiled using djgpp: 
256 color SVGA graphics. 
Haze colouring of distant scenery. 
Gyroscopic precession forces from propeller included. 
Wind of random direction and strength added. 
Waypoints with HUD navigation info. 
Scrolling, zoom-able map. 
Messages from tower. 
Ground collision detection improved. 
Setup files for Thrustmaster FLCS and TQS included. 
Dots on ground to improve depth perception. 
Selectable landscape drawing distance. 
February 1997. Version 0.17
Nimitz class aircraft carrier: 
Sails into wind, trying to keep 25kts of wind over deck. 
Rolls, pitches and heaves depending on wind strength. 
Maneuvers to avoid land. 
Detailed arresting wire forces. 
ILS beacon. 
"Meatball" with adjustable tilt. 
Approach indexer 
Landing Safety Officer is guiding you down by voice. 
View from LSO station. Select by pressing "Home" 
Landing grades/score given. 
Sound support for Sound Blaster compatible cards: 
Aircraft sounds have doppler frequency change and 
volume depending on distance. 
Sampled speech (LSO etc.) 
Controls: 
Analog throttle supported. 
Adjustable null zone. 
Adjustable noise filter. 
Nicer menu structure. 
Control surface deflection decreased to more realistic values. 
Starting location menu. 
Wheel rotational momentum added. 
HUD-modes: 
Air-air Select by "Enter" 
Air-ground "Backspace" 
Navigation "n" 
ILS "i" 
HUD on/off Changed to "ALT h" 
Bugfixes: 
Scaling factor in gravitational torque corrected. 
Flaps now updated when swapping planes in mid-flight. 
FLCS un-pause works without delay. 
  June 1997. Version 0.18
  Propeller engine: 
    Engine torque depending on power, RPM and air density. 
    Propeller treated as a rotating wing, causing: 
      Efficiency depending on RPM, flight speed, 
      propeller pitch and air density. 
      P-factor. 
      Propeller slipstream / vortex affecting tail surfaces. 
      Torque from drag and inertia. 
    Constant speed propeller, with pitch depending on RPM. 
    Blade lift and drag calculated from wind tunnel data. 
    RPM setting handle: 
      CTRL F1: low RPM CTRL F4: high RPM 
      CTRL F2: decrease RPM CTRL F3: increase RPM 
    RPM display. 
  Flight model: 
    Angular momentum coupling between axes. 
    Induced drag calculations more detailed. Adverse yaw stronger. 
    Side-slipping forces stronger. 
    F-104: Landing speed lowered to 180 kts, AoA 7.4 deg. 
    F4U: "Toe-out" on gear for better ground handling. 
    F4U: Approach AoA lowered to 5.0 deg. 
    Anti-bounce kludge: Toggleable from Realism menu, this will make control 
    easier when turned on. But it has no real-world equivalent. 
  Control surfaces: 
    Limited actuator speed. 
    Rudder auto-coordination option. 
    Rudder trim: left: ( right: ) 
    Aileron trim: left: { right: } 
  Graphics: 
    Animated graphics of: 
      Control surfaces, flaps, brakes, landing gear and propeller. 
    Analog instruments: 
      Turn & slip indicator. 
      RPM dial. 
      Altimeter. 
    HUD: 
      "nose-pointer" added. 
      AoA display added. 
    Trim position indicators. 
    Vector graphics mode removed. 
  Sound: 
    Slight changes to LSO comms. 
    Stall horn added. 
    Menu for setting speech, engine and miscellaneous sound volume. 
    "-nosound" option for people with incompatible hardware. 
  Misc: 
    More reasonable wind directions when using RWY 00. 
    LSO wave-off limit and landing grades tweaked. 
    Documentation in HTML format. 
    Anti-flicker delay no longer needed. 
  Bugfixes: 
    Angular inertia of right size - it was too small before. 
    Polygons filling the entire screen are now (mostly) drawn. 
    LSO altitude instructions corrected. 
  September 1997. Version 0.19
  Sound: 
    Speech samples of higher quality contributed by Edward G. Kinateder (LSO 
    voice) and Mac McAuley (pilot voice). 
  Flight model: 
    F-14A Tomcat added, with: 
      Variable geometry wings and glove vanes, sweep set from Mach number. 
      Auto-throttle, toggle by pressing "t". 
      "Direct Lift Control" spoiler manipulation. Increase lift by pressing "q", 
      decrease by "a". 
      Roll control using taileron and differential spoilers. 
    Undercarriage cannot be lowered while on ground. 
    Gear-up landings improved. 
    Engine failures possible. Press "F" to get one within the next minute. 
    Wing C_p location depends on flap deflection. 
    Air temperature depends on altitude. 
    Location of center of pressure and gravity adjusted for less pitch and yaw 
    stability, decreasing "nose bounce". 
    Control surface gain adjusted. 
    Approach speed and AoA adjusted. 
    Anti-bounce kludge removed. 
  Graphics: 
    HUD: 
      Mach number display added. 
      Auto-throttle and DLC indicators (F-14 only). 
  Controls: 
    Linear and exponential controls now have same total stroke. 
  January 1998. Version 0.20
  Flight model: 
    F-14: 
      Decreased induced drag. 
      Glove vane servo improved. 
      Flaps retract at sweep above 55 deg. 
      Manual sweep mode: 
        Toggle auto/manual by "s" key. 
        [F9]: Minimum sweep, 20 deg. 
        [F10]: Decrease sweep by 5 deg. 
        [F11]: Increase sweep by 5 deg. 
        [F12]: Maximum sweep, 68deg. 
  Propeller engine: 
    F-4U engine has two-speed auxiliary blower, operated automatically. 
    F-4U engine has 2:1 reduction gear. 
    Manifold pressure display. 
  Graphics: 
    Night / dusk / day / dawn selection, with dynamically changing light 
    intensity. 
    Carrier and runway lights. 
    1630 stars displayed from the Yale Bright Star Catalogue. Sky orientation 
    can be set for any time and location. 
    Wing sweep angle and mode indicator (F-14 only). 
    HUD: 
      Monochrome option. Toggle by "ALT h". 
      Altitude above ground level and "PULL UP" warning are displayed. 
    Analog instruments: 
      Artificial horizon 
      Indicated Airspeed 
      Vertical Velocity Indicator 
      ILS needles 
      Magnetic compass 
      Accellerometer 
      Manifold pressure 
  User interface: 
    The graphical user interface, MGUI by Vincenzo Morello, is used. Among the 
    improvements to the menu system are the possibility of selecting aircraft 
    type before flight, and graphical joystick calibration. 
    Mouse support re-established. It causes some screen flickering when used. 
  Bug fix: 
    Sticky behaviour at 0/180 heading removed. 
    Auto-throttle now works with HUD off. 
    Vertical velocity on HUD now of correct size: Ft/sec. 
  June 1998. Version 0.21
  Flight model: 
    New aircraft, called "X-17" for demonstrating work in progress. Introduces 
    wing dihedral for roll stability and undersized tail fin, making aircraft 
    prone to "Dutch roll". Has no ailerons or flaps, but is easily steered using 
    rudder. 
    Stall angle increased when slats are extended. Makes handling of the F-14 
    better at high AoA. 
    Control sensitivity adjusted for each aircraft. 
  Catapults: 
    The four catapults can be selected as starting locations, or can be taxied 
    onto from the deck. Properly equipped aircraft (F-14 only) can then be 
    launched. 
  Graphics: 
    Wind-bag at airfield, turning and inflating according to wind. 
    Moving jet blast deflectors behind catapults. 
    Instrument panel display can be toggled by key "SHIFT i". 
    Padlock view of target or waypoint from cockpit by key "*". 
    Padlock view of target or waypoint in external view by key "/". 
    HUD: 
      In air-to-air mode, a gun "snake" is displayed, and a Lead Computing 
      Optical Sight pipper for the selected target. 
      Inside LCOS is a range clock. 
      Selected target has a box around it, with relative heading and aspect 
      markers. 
      To the lower right, target range, closure speed and aspect angle are 
      displayed. 
      Number of remaining gun rounds is written at lower left. 
    Analog instruments: 
      Delayed response for instruments sensing air pressure: VVI, ALT and IAS 
      indicators. 
  Guns: 
    Only a fraction of the rounds are tracers. 
    Tracers extinguish after 5 seconds, but all bullets flies for 15 seconds. 
    Recoil made less prominent. 
  Targets: 
    Gunnery practice range at waypoint "TARGETS". 
    Four circling targets at random speeds, g-loads and altitudes. 
    One stationary target on surface. 
    Next target can be selected by key "SHIFT t". 
  Sound: 
    Warning message when crash is likely. 
    Rumble from wheels when rolling. 
    Catapult launch sound. 
    Tweaked stall horn. 
    Sound when hitting or destroying a target. 
  Source code: 
    The source code for defining the graphic objects is now available for 
    downloading. You can design your own objects and load them into the 
    simulator. 
  November 1998. Version 0.22
  Flight model: 
    Fuel tanks, with selectable starting quantity. 
    Fuel consumption by jet and propeller engines. 
    Detailed jet engine model as option: 
      Thrust depending on Mach number and altitude. 
      Multi stage afterburners. 
      Compressor stalls. 
      Flame-outs. 
      Wind-milling and air-restarts, key "e". 
    Trans- and super-sonic drag. 
    Maximum control surface deflection decreases with increasing airspeed. 
    F-14 auto-throttle is now governed by AoA, but works poorly. 
    Restored efficiency of Harrier attitude controls. 
  Graphics: 
    Cockpit walls and canopy frames in internal view, although very crude. 
    Toggle by key "d". Caution: Panning while showing cockpit triggers a bug in 
    the graphics engine. 
    Display of aircraft in internal view can be toggled by key "SHIFT d". 
    Internal cockpit panning. 
    Smooth / instant panning option. 
    Analog instruments: 
      Dual fuel quantity display. 
      Fuel flow, jet and prop version. 
      RPM, now also jet version. 
      Exhaust gas temperature, jet only. 
      Undercarriage position. 
    HUD: 
      Bank indicator. 
  Sound: 
    Ball calls include fuel state. 
    Sounds for afterburner. 
  Misc: 
    LSO: 
      Now only judges airspeed from AoA. 
      Less eager to wave-off and more generous with grades. 
    More options saved in config file. 
  August 2000. Version 0.23
  Flight model: 
    North American X-15A-2 added: 
      Rocket engine w. fuel consumption 
      Reaction Control System, toggle activation by key "r". 
      High altitude drop option added. 
    Dynamic centre-of-gravity calculations corrected. 
    High altitude atmosphere model more detailed. 
  Graphics: 
    Sky darkens with altitude, and stars appear. 
    Menu-system debugged and tweaked. 
    AoA chevron colours swapped to correct order. 
  Sound: 
    Rocket engine sound added. 
  Misc: 
    Larger fraction of source code released. 
    Black screen startup pause on some systems is removed. 
    Jet fuel flow indicator now shows zero when out of fuel. 
    Auto-throttle debug info removed. 
  September 2001. Version 0.24
  Flight model: 
    Grumman Lunar Module added: 
      Highly detailed descent module graphics made by H. Frik. 
    More detailed rocket engine model: 
      General orientation. 
      Non-zero idle thrust. 
      Fuel flow toggle by key "e". 
      Auto throttle (key "T") for Lunar Module. 
  Scenario: 
    Moon scenario added: 
      Grey landscape with mountains and "seas". 
      No atmosphere and reduced gravity. 
      "On surface" and "Low Gate" starting locations. 
  Graphics: 
    Solar position on the sky depends on time and geographic latitude. 
    Contrast of illumination depends on atmospheric pressure. 
    A few custom colours for aircraft, in stead of the fixed pallette. 
  Sound: 
    Radio communications for the Apollo 11 mission added. 
  Misc: 
    Complete source code released. 
    Engineering mode, key "E" for more panning and zooming freedom. 
  September 2001. Version 0.24.1
  Maintenance release 
  Graphics: 
    Page flipping works again when using the mouse. 
  Misc: 
    Source made compatible with LibGRX 2.4.3. 
March 2002. Version 0.25
  Flight data logging to text file can be toggled by key "SHIFT-l" 
  Vertical keypad panning reversed when in cockpit 
  Keypad 5 restores forward view 
  Source made compatible with Allegro 4.0 
Latest version: April 2002. Version 0.26
  First functional release for the Linux environment. 
    Runs in window under X11 or full screen in console 
    Joystick input is missing, though. 
  Using Allegro for graphics and input. LibGRX is abandoned. 
  Using CGUI for menues. MGUI is abandoned. 
  Easier program installation in DOS/Windows. 
  Trim keys moved. 
    Use SHIFT plus arrow keys for elevator and aileron trim. 
    Use ALT plus left/right arrow keys for rudder trim. 
  Bugfixes: 
    Corrected throttle position when swapping planes and starting. 
    No more flameout when swapping from prop to jet plane. 
    And more... 



Known bugs
Some of these are:
* The joystick calibration routine messes up timing - better to exit the program 
after calibrating. * Panning inside cockpit while displaying internal cockpit 
graphics triggers a bug in the graphics engine. This especially happens if 
smooth panning is enabled and the "viewing distance" in the graphics menu is 
large.
* Some parts of the HUD does not scale correctly to the screen dimension data 
you enter. 
* Occasional overflow or divide by zero halts, especially when you are 
stationary on the ground.
* Objects that are supposed to be hidden behind a hill are often drawn.

Many more bugs are suspected. De-bugging is slow and pain-staking, partly due to 
my messy programming. Also, adding new features (and bugs!) is much more fun, so 
expect many bugs to appear. Bug reports are always welcome. Make them as 
detailed as possible. 



Updating
The most recent version can be fetched via WWW at 
http://www.astro.ku.dk/~norup/vertigo/vertigo.html. 
Deadline for next update:
I have no idea. Don't hold your breath for it! 
When you upgrade, you may just as well delete the entire old vertigo directory, 
to avoid unused files and a conflict with the old configuration file. 



Distribution
The Vertigo binaries are distributed as freeware.
This means that the program is distributed free of charge. It may not be sold in 
any form. Vertigo may only be distributed as the original zipped archive 
containing the files listed in the installation section. 
The source code for Vertigo is available for downloading. These sources are 
distributed under the GNU General Public License for free software. Read the 
license file included in the source package for further details. 



Troubleshooting
If Vertigo halts because of an error before you are able to go to the main menu, 
you can force Vertigo to re-configure by deleting the VER_CNF.GCC file manually.
Further instructions are found in INSTALL.TXT 


Home-built flight simulators
Please visit my on-line listing of these. 


About the author
I have been hooked on flight as long as I can remember, and spent a significant 
part of my childhood tossing paper planes and the like. 
In 1986, I entered the Royal Danish Air Force in an attempt to become a fighter 
pilot. After ten months of training, including 18 hours in the Saab T-17 
Supporter, the instructors and I agreed, that I did not have the "magic touch". 
Afterwards I started studying physics and computer science, specializing in 
astronomy, and have now got my MSc degree at the University of Aarhus, Denmark. 
Currently, I am at the Copenhagen University Observatory, working on 
instrumentation for astronomical telescopes. 
I have crashed a couple radio-controlled model aircraft beyond worthwhile 
repair, and still have a semi-scale model of the Saab Supporter, that flies all 
too rare. Now I am mostly playing with electrically powered flying wings, which 
are great fun. 
In the spring of 1997, I have joined a soaring club, the Flyvestation Værløse 
Svæveflyveklub. If you think, the Vertigo releases are occurring less frequently 
now, you got the reason here. The real thing is more fun than tampering with a 
simulation. 



Why is the simulator called "Vertigo"?
Several companies use the name "Vertigo" for a product, so why don't I choose a 
more original name that fits the simulator better? 
Well, I like the name for two reasons:
The spatial disorientation experienced by pilots under IFR conditions is even 
more pronounced in simulators, due to the extremely limited field of view and 
lack of feed-back from e.g. accelerations.
The name also is a good description of the confusion that characterizes the 
creation of the simulator. I have just put in what ever I felt like doing, and 
there is no real theme. 



How can YOU help making Vertigo better?
Making a complete flight simulator is a big job, and I am happy to get any help 
you can offer. As of version 0.24, all of the source code has been released, 
making it possible for you to make modifications and extensions to the program. 
Download the source code and read the accompanying documentation for more 
details. Here are some suggestions for areas where you can help: 
  You could: 
  Design some nice graphic objects to be included in the simulator, by adding to 
  the distributed source code. For instance, you could make aircraft, ships, 
  buildings, cars,... 
  Make an object designer program that is easier to use than putting the numbers 
  directly into the source code. 
  Make a converter from your favourite 3D editor format to my format. 
  Provide sound samples replacing the current ones, as some of these may be 
  violating copyrights. Or provide nice samples for future extensions of the 
  sound. 
  Provide documentation on aircraft performance, aerodynamics, engines, carrier 
  operations, and other details that could help make the simulator more 
  accurate. 
Please note, that whatever you contribute, I have no obligation to include it in 
the official release of the simulator. 


Credits
The joystick reading routine has been copied and modified from Eyal Lebedinsky's 
FLY8 simulator. 
From version 0.16, the DJGPP compiler is used. DJGPP is a MS-DOS port of the GNU 
gcc compiler. The port is done by DJ Delorie and friends. It is distributed from 
http://www.delorie.com. 
Shawn Hargreaves' "Allegro" library is used for graphics, sound, key/mouse input 
and timing. Allegro has great cross-platform support. It is distributed from 
http://www.talula.demon.co.uk/allegro/ 
In version 0.26, the graphical user interface "CGUI" by Christer Sandberg is 
used. It can be found at http://www.idt.mdh.se/~csg/cgui/ 
MGUI by Vincenzo Morello, was used from version 0.20 to 0.25. The code is still 
present in Vertigo, but it is not updated for later versions. Get it at 
http://web.tiscali.it/morello/MGui/index.html. 
Some lift and drag coefficients are derived from wind tunnel data provided by L. 
Lazauskas. 
I got a lot of neat data on the F4U from Jerry "Zman" Zollman and Greg 
O'Sullivan. "Zeno" also have put some goodies on his page: 
http://www.zenoswarbirdvideos.com/. 
LSO samples are made by Edward G. Kinateder with assistance from Mac McAuley. 
Thanks to Jouni Raitamaki for providing jet engine data. 
Thanks to H. Frik for making the beautiful graphics for the Lunar Module descent 
stage. He also provided lots of data and sound files for the LM simulation. 
Thanks to A. Lamprou for bug reports. 



Feedback
Comments on Vertigo are appreciated. Send them to: 
Anton Norup Sørensen
e-mail: a_norup@post.tele.dk
http://www.astro.ku.dk/~norup/ 