PC Based Flight Simulators

Russ Erb

Originally published December 1992

Microsoft Flight Simulator
Azuresoft ELITE
ELITE Description
ELITE System Requirements
And In Conclusion...

With the rapid growth in computing power of desktop PCs over the last 11 years, it's not surprising that someone would harness this power to make a flight simulator accessible to folks like us. Many programs have been written, with varying objectives from games to flight training/simulation of a "real" airplane. Two programs that fall at the latter end of the spectrum are Microsoft Flight Simulator and Azuresoft ELITE (ELectronic IFR Training Environment). Even though both of these programs attempt to simulate actual flight, their underlying objectives result in two very different programs. For those of you looking for a way to get that IFR simulator time cheap, keep looking. The FAA has not approved any PC based simulators for logging time. Azuresoft hopes to convince the FAA sometime in the future to certify ELITE for logging time, but has not done so yet.

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Microsoft Flight Simulator

Microsoft Flight Simulator is a rather old program. The oldest version I ever saw was in 1983. The apparent objective of this program was to create a low-cost program that would simulate the basic principles of flight for the non-pilot. In the interest of low-cost, the program was written to run on bare-bones machines. The original program I saw was running on a 4.77 MHz 8088 IBM PC.

The program is capable of extensive scenery, for a pseudo-VFR flying environment. As the program comes, it only has scenery for about five small but detailed areas. Scenery disks are available from Sublogic (or at least use to be) that cover much larger areas with less scenery, primarily VORs and runways. While Sublogic advertising implies that scenery disks are available for the entire country, Europe, and Japan, many of the disks have never been released. It almost seems as though the flight simulator program and the technology available are changing too fast for them to keep up. I have not followed this closely for the last several years, for reasons you will see later. As a different approach to the problem, Microsoft released the Aircraft & Scenery Designer, which purports to allow you to design your own scenery and model different airplanes. I found the interface for this program to be very clumsy. The greatest fault I found with this program was the poor implementation of spatial coordinates. Flight Simulator uses a grid coordinate system that has little or no relationship with the real world. The Scenery Designer claims to be able to use either this grid or lat/longs, however, the conversion is flawed. For instance, I tried putting a piece of scenery at Fox Field, using the latitude and longitude for Fox Field. This piece of scenery ended up several miles from the preexisting runway for Fox Field. Placing items by VOR radial and DME seemed to work well. The biggest benefit of the scenery database is that you can "fly" cross-country to anywhere covered by existing scenery.

In its latest version, Flight Simulator allows you to choose from several different types of aircraft. The main program comes with a Cessna 182RG and a Learjet. The Aircraft & Scenery Designer adds a 747-400, plus the ability to "design" your own aircraft. For those of you trained in flight mechanics, some of the parameters used in defining the aircraft are similar to stability derivatives, but some seem to be in purely arbitrary units.

Situational awareness is difficult with this or any other PC based simulator. Consider the field of view of your monitor, or better yet, imagine trying to fly your airplane with all of the windows blacked out, except for a one foot square area right in front of your face. Flight Simulator does allow you to change the view on the monitor to any of eight viewing angles (every 45 degrees of azimuth). Still, it takes some significant mental gymnastics to imagine you are looking back over your left shoulder while looking straight in front of you. There is a map or "God's eye" view available, which does help keep track of where you are, but this seems like cheating and unrealistic unless you happen to have a moving map display in your cockpit. The program also has a limited capability to play back a graph of your trajectory, but only if you remember to turn it on ahead of time.

Probably the biggest positive factor for Flight Simulator is its price: $39 from PC Connection. The Aircraft & Scenery Designer is similarly priced.

Even with all of these features, Microsoft Flight Simulator has enough shortcomings that finally drove me to stop using it altogether. The first shortcoming is that the aircraft math model is lacking in several areas, primarily in the area of coupling between axes, such as using the rudder to bank the aircraft. It is also difficult to do normal aerobatic maneuvers, which I only mention because the program claims to be able to do aerobatics. Anyway, the result is that the airplane does not fly like a pilot would expect it to.

The critical shortcoming is in the slow update rate of the screen. As a result, the screen is always lagging behind what the pilot is commanding. This destabilizes the control loop, and tends to promote PIO. This problem became apparent to me when I tried landing Flight Simulator about a month after I had soloed the Piper Traumahawk. Figuring this would be easy, since I had been able to land a real airplane, I was quite surprised to find that I could not land the simulator using the same technique I used for the real airplane. The last time I had used Flight Simulator prior to beginning flight training, I had been able to land the simulator, but only by using a different technique. A flight simulator is not much good as a flight simulator if it does not fly using the same techniques as used in a real aircraft. Anyway, back to the slow update rate. I was running Flight Simulator on my IBM PS/2 Model 80, with a 16 MHz 80386 processor and a CH Flightstick and MAXX Pedal rudder pedals. 16 MHz is not a slow machine by any standard, but the update calculations are still too slow. Calculations of aircraft equations of motion involve a large number of floating point (numbers with decimal point values, such as 4.23534) calculations. The Intel x86 series of microprocessors (8086, 8088, 80286, and 80386) are only capable of doing integer calculations. Floating point operations are implemented through software, either in microcode or the operating system. The result of this is that floating point operations are much slower than integer operations on the native processor. The coprocessor (8087, 80287, 80387, internal to the 80487DX) is built to handle floating point operations significantly faster than the native processor. I have seen a speed improvement of as much as 28 times, depending on the software in use. The catch is the coprocessor will not be used unless the software is written specifically to use it, otherwise it will be ignored and make no difference. Herein lies the rub. Microsoft Flight Simulator is not written to use the coprocessor.

Not only do the aircraft equations of motion calculations slow down the program, the scenery only makes it worse. Flight Simulator advertises dynamic scenery, such as other airplanes moving around, but these really slow down the system. Even so, with dynamic scenery turned off and minimal static scenery, the update rate (at least at 16 MHz or less) is unacceptable.

One more destabilizing factor is that Flight Simulator uses joystick input through a game port. IBM Joysticks are nothing more than a linear potentiometer on each axis from 0 to 100K ohms. This is unlike the mouse, which uses a digital encoder. The game port is a fairly coarse A/D converter, and this coarseness adds to the jerky behaviour of the slow updates.

The turbulence simulation is pretty poor, being essentially a constant shaking of the aircraft. As we know, turbulence is much more random.

To be complete, it should be said that none of the scenery packages contain any military or private airfields. They are limited to public use fields, but not all of those are available. For instance, Rosamond Skypark (L00) is not represented.

None of the simulator programs have any significant communications simulation. As we know, this can be a significant workload in the cockpit, especially in the terminal environment. Flight Simulator has a pseudo-communications capability, which is limited to hitting a key to request takeoff or landing clearance--hardly a workload increase.

Lest you think I'm unique in not caring for Microsoft Flight Simulator, talk to our esteemed president Bob. He doesn't like it either.

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Azuresoft ELITE

If you think this is an unbiased evaluation of these two programs, I'll say right up front that I like ELITE and recommend it as a reasonable flight simulator. The objective of the program is listed in the introduction to the manual as "ELITE is not a computer game to give non-pilots the illusion of flying an airplane; it is an advanced computer-based training tool for licensed pilots."

The programmers went to great lengths to accurately model fully coupled, six degree-of-freedom flight dynamics. They did a reasonably good job of this. ELITE accurately simulates the short-term and long-term dynamic motions such as the phugoid and spiral divergence modes. Using the separate rudder control allows flying slips, skids, and rolling with rudder. The control response and stability of ELITE/Advanced is modeled after the Cessna 172.

The update rate of the screen is significantly better, with no noticeable jumps in the movement. The primary factor behind this is the program uses the numeric coprocessor; in fact, a coprocessor is required on DOS machines and some Macs. The result is a much more realistic response. I was able to land the aircraft on the runway successfully on the first try, using the same technique I use in the real aircraft. The update rate is further improved by the small amount of scenery to calculate, which is essentially limited to the runway and runway lights. Even this is not calculated while the aircraft is "in the clouds."

In a further evaluation, Mike Pelletier said that ELITE was easier to fly than the FAA certified simulator at the Edwards AFB Aero Club. One of the primary reasons he stated was the ability to trim easily. Mike did not like the trim on the Aero Club simulator because it was unlike the feel of the real aircraft. The ELITE uses the trigger and button on the CH Flightstick as the down and up switches for "electric" trim, which simulates the "coolie hat" trim reasonably well.

The control of ELITE is further enhanced by the "Universal Controls Interface," a small box which comes with ELITE. The joystick and rudder pedals plug into the UCI, which contains a much finer A/D converter than found in the game port. The UCI is connected to the computer through the serial port.

Like Flight Simulator, ELITE has a map view which can be used to enhance situational awareness. However, it cannot be displayed simultaneously with the instrument panel. ELITE will automatically record your flight path for play back. It will play back the last 40 minutes on a DOS machine and the last 60 minutes on a Mac.

Of course, all is not wonderful with ELITE. The aircraft has low stability in roll, such that it will roll off on one wing or the other if your instrument scan breaks down and you ignore it too long. A point could be made that this is good for training, but it is less stable in roll than any real aircraft I have flown.

As mentioned earlier, there is very little scenery, limited basically to the runways and runway lights. Then again, this is a purpose built IFR trainer, and there is little scenery inside of clouds. Of course, you can put the ceiling as high as 5000 MSL and simulate VMC, with the requisite slight performance hit.

This limited scenery is available only in limited areas, basically areas around TCAs. The navigation databases that are available are: Atlanta, Baltimore, Boston, Charlotte, Chicago, Cleveland, Dallas-Ft. Worth, Denver, Detroit, Houston, Kansas City, Las Vegas, Los Angeles (which covers our area), Memphis, Miami, Minneapolis, New Orleans, New York, Orlando, Phoenix, Philadelphia, Pittsburgh, Salt Lake City, San Diego, San Francisco, Seattle, St. Louis, Tampa, and Washington D.C.

With all of these areas covered, you still can't fly from someplace in one navigation database to somewhere else in another. The only way to change databases is to quit the program and restart it with a different database. Thus, you can't fly from Fox to San Francisco and simulate the whole trip. While you could record your heading, airspeed, and altitude and restart the program, you're left with a big gap between areas. The navaids do go out of range at realistic distances as you fly away from the area covered by the database. Thus, you are pretty much limited to short flights and terminal operations.

The view out the window is limited to a small field of view straight ahead, which is fine for straight in approaches, but almost useless for circling approaches, such as those at Fox.

As with Flight Simulator, there are no military fields and no communications. Of course, your flight time is not legally loggable.

You are limited to one type of aircraft per program. The ELITE/Basic and ELITE/Advanced both simulate a single-engine, fixed-gear, fixed-prop airplane such as the Cessna 172. ELITE/Basic is written for 286 machines, and goes for $349 (ouch!). ELITE/Advanced is for 386/486 machines or a Mac II, and claims increased realism and enhanced graphics over ELITE/Basic. ELITE/Advanced goes for $499.

If you wish to try something bigger, ELITE/High Performance simulates a single-engine, retractable gear, controllable pitch prop airplane, such as a Mooney or Cessna 210. It goes for $699. This is the screen that I have seen in all of the ads. If this isn't enough, try ELITE/Jet, which simulates a MD-10. I don't have a price, but it's more than $699. Each program comes with your choice of navigation database. Additional databases cost $49.95.

If the prices scare you off, you can get a demo version for $50. This is the full program without the UCI, so you have to fly it with the mouse on the trim wheels. The flight is limited to three minutes at a time. However, Azuresoft offers a 30 day money back guarantee, which gets you the whole thing. Don't bother trying to pirate the software--without the UCI it reverts to the demo mode. For those of us in Chapter 1000, your best bet is to call me, and I will be glad to let you try mine out.

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ELITE Description

ELITE presents you with a standard IFR panel. The Airspeed Indicator has the standard colored arcs. The attitude indicator is in the center of the T layout. The altimeter is a three-pointer model, with an adjustable Kollsman window. The DG has a heading bug which is moved by a mouse. Pressing one button runs it around clockwise, the other counter-clockwise. The longer the button is held, the faster the bug moves. Other flight instruments are the Vertical Speed Indicator, Turn Coordinator, and magnetic compass. The magnetic compass accurately models magnetic dip and the anomalies it causes.

For general control, a throttle can be moved by the mouse or a joystick, and is topped by a digital tachometer. The mixture control is topped by a EGT gauge, and moving it causes the expected variations in RPM. Carb heat is available, and reduces RPM accordingly. The flaps can be set in 10 degree increments from 0 to 40 degrees. A digital stop watch is also provided for timing anything. The trim wheels (pitch and yaw) can be moved with the mouse. The pitch trim wheel can also be moved by the buttons on the CH Flightstick. A two-axis autopilot is available with heading and altitude hold. A useful function of the autopilot is temporarily engaging it will properly trim the aircraft for straight and level flight. Control wheel steering is also provided.

For navigation, two NAV radios, DME, ADF, and marker beacons are provided. No, they're not King radios, but they work. The NAV and ADF radios have flip-flop tuning. NAV1 also has glideslope for ILS approaches. Pressing a button on the NAV radios will show the radial of the selected VOR that you are currently on (lots easier than spinning OBSs). Pressing another button plays the station ID (morse code) through the PC speaker. The DME can be tuned separately or remotely to the station set in NAV1. The ground speed in knots can be shown in place of the DME frequency (with DME still showing!). Two OBSs are displayed, unlike the screen shown in all of the ads. Azuresoft rearranged the panel to allow use of two OBSs. The OBS will show digitally the setting at the top of the dial.

The map screen allows you to set your position, heading, altitude, and airspeed. You can point and click on airports or navaids for information. The LAX database extends from Fox Field to Oceanside, and from the coast in to Rialto.

The simulation is controlled from the controls screen. Turbulence can be set to none, light, moderate, or severe. The simulation of turbulence is much better, with more randomness. You may find you don't need it, as the airplane is skittish enough in roll without it. Turbulence diminishes below 1000 feet AGL to zero at the ground. Wind direction and speed can be set, and will change realistically near the ground due to surface friction and coriolis. The ceiling can be set to a hard altitude, or to a variable altitude. If set to variable, it will vary +/- 50% around the set altitude. If the ceiling is variable and set to the minimum decision altitude (MDA), you may or may not see the runway environment by the time you reach minimums. Visibility is set in nautical miles or meters, and the field altimeter setting can be set.

Yaw control (separate rudders) can be set. If turned off, flight will always be coordinated. Instrument failures can be specifically set, or armed to fail randomly. If armed, there is a 20% chance of a malfunction every minute. In this mode, only one instrument will fail at a time. The ADF can be set for imprecision, where it will oscillate realistically when far from the station. It will also read high in right turns and low in left turns.

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ELITE System Requirements

ELITE/Advanced will run on DOS machines or Macs. For DOS machines, a 80386 (SX or DX) or 80486 (SX or DX) processor is required. (ELITE/Basic will run on 80286 machines.) Some of the literature says at least 16 MHz is required, other literature says 20 MHz. I run it at 16 MHz and it works fine. Besides, 80386s don't run any slower than 16 MHz anyway. As mentioned before, a coprocessor is required (except with the 80486DX). Minimum memory is 2 Meg (2048K). VGA graphics with 256K memory is required. For control, a mouse and a serial port to connect the UCI to are required.

For DOS users, this is important to note, since IT IS NOT MENTIONED ANYWHERE IN THE DOCUMENTATION. Some form of memory manager, such as QEMM, is required to turn your 2 Meg of RAM into expanded memory (EMS). The closest the manual comes to mentioning this is in an obscure comment in the troubleshooting tips. And don't try to run it under Windows. It don't work.

For Mac users, you'll need a Mac-II, IIx, IIcx, IIci, IIfx, Quadra 700, or Quadra 900. A Mac SI, LC, and LC/2 will work with an optional math coprocessor. RAM is the same at 2 Meg available to the program. The display must be a 640 by 480 (or bigger), 4 Bit/pixel (or deeper) color display plus video card. The 12" Apple Color Monitor won't work.

For controls, the best recommended is the CH Flightstick. Of course, any joystick will do. The Maxx yoke will work, and would seem the best way to simulate a lot of the aircraft we fly. However, the centering in roll is very weak on the Maxx Yoke, which only adds to the tendency for the aircraft to roll off uncommanded. On the other hand, the Maxx Pedal is an excellent set of rudder pedals. Having a realistic throttle control is another matter. I have not seen any advertised, so I had to design my own. Watch a later newsletter for plans for that.

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And In Conclusion...

The manual for the program is rather skimpy, but sufficient. The manual does specifically state that is solely a reference for the program, and "in no respect a tutorial in instrument navigation." For charts and approach plates, use the same pubs you fly with.

Hopefully I have accomplished my goal in writing this article, which was to answer for you all of the questions I had before I bought ELITE.

If you want to order ELITE, write Azuresoft at 1250 Aviation Avenue, San Jose, CA 95110, call them at 800-282-6675, or fax at 408-947-8595.

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(Update note: ELITE is now sold by Aviation Teachware Technologies)

Related Articles:

PC Based Flight Simulators, Part II - How to build a throttle control

PC Based Flight Simulators, Part III - Review of a newer version of ELITE


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Contents of The Leading Edge and these web pages are the viewpoints of the authors. No claim is made and no liability is assumed, expressed or implied as to the technical accuracy or safety of the material presented. The viewpoints expressed are not necessarily those of Chapter 1000 or the Experimental Aircraft Association.
Revised -- 27 March 1999