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Simulating IMC failures: flying your desktop PC is fine way to keep those IFR skills from getting too rusty, but doing it partial-panel might save your life.

Instrument failures are responsible for a small fraction of air craft accidents. Instrument failures do happen, though, and proper handling of the event can save your life. Simulated failures in the real airplane, however, often lacks realism. The instrument is covered rather than giving false information and the failure is rarely a surprise.

A Big Deal?

Dead instruments are obviously more critical in IFR flying than in VFR. Party this is because all these instruments are really a backup to your eyes, ears, and seat-of-the-pants. When the failed attitude indicator disagrees with the real horizon, there's no issue in identifying the failure. When you're on the gauges, though, the instruments are primary and backup to each other and some of your senses can't be trusted. Less information and conflicting information makes for delayed or incorrect responses.

A good simulator addresses this problem nicely. It doesn't need to be a fancy aviation training device, either. Desktop simulator games can maintain the skills you need to stay shinny side up. The keys to surviving are recognizing the problem and responding appropriately.

Exact statistics are hard to come by because it is difficult for the NTSB to determine the exact circumstances if the pilot is no longer with us.

In one study involving over 2500 air carrier events from 1983 to 1999, only one was determined to be due to vacuum system failure, 10 involved spatial disorientation, and 42 were caused by continuing flight from VFR into IMC. In 2001, 1750 GA accidents had five vacuum failures, 22 disorientations, and six pilots going from VFR into IMC. From 1983 to 2004 out of more than 45,000 GA reports there were 42 disasters involving vacuum systems (38 fatal), 29 spatial disorientations, 28 autopilot failures, and 1500 VFR into IMC incidents.

You can't say how much blame should fall on the shoulders of equipment and how much is simply the failure of the pilot to properly respond. We learn full-panel and partial-panel instrument scanning in training, but it's one of those skills that rusts quickly. The pilots involved in the emergencies described above might have benefited from more practice.

Behind the Screens

Two of the most popular "game" flight simulators are Flight Simulator X (FSX) from Microsoft and X-Plane from Laminar Research. Both have the capability to simulate certain types of failures, including any of the basic six: airspeed, artificial horizon, altitude, turn coordinator, heading indicator (or directional gyro), and vertical speed. (There are other computer-based aircraft simulators out there, too--On Top, Elite, etc.--but we'll keep our discussion to just these two popular ones.)

Microsoft's simulators have a nice feature that allows the program to select which items will fail and when. Under each tab you can select how many randomly selected items from each category will fail at randomly selected times bounded by time limits you specify. For instance, you can ask for two instruments to fail between four and five minutes and then another system to go out between one and three minutes. This might result in the pilot tube failing at 2.1 minutes, losing the airspeed indicator at 4.2, the altimeter at 4.8, and the VSI at 4.9. Using this process, you would never know just which item would go bad nor at what time. This also creates the kind of slow cascade of failures that might occur when trapped water freezing slowly took out the pitot tube and then static port, as happened to a Comanche owner we know.

High-end versions of X-Plane are being used to control several FAA-approved training devices and have the ability to simulate more than 300 potential causes of accidents. An instructor at a separate computer can set up failure events without the knowledge of the student. These features are carried over to the public version of X-Plane. Instruments, as well as other parts of the plane, can be set to stop working when the airplane reaches a certain speed, altitude, elapsed time, at random times, or when the user pushes or clicks a button.

One thing to keep in mind when using either of these systems is that they model flight quite differently. Most game simulators, including Microsoft's, rely primarily on tables of empirical data gathered from actual flights. There are ways that the data so gathered can be modified to allow an approximation of the performance of one plane to be obtained from a different ship.

X-Plane, on the other hand is an application of pure physics. The model of the airplane is divided into hundreds of small areas and the aerodynamic forces on each are calculated 50 to 100 times per second. The aero-forces of each are calculated and then summed up. Isaac Newton takes over at this point with the old, familiar F = ma (or, rather, a = F/m). The accelerations (both linear and rotational) in three directions are used to modify the current velocity components. The result is a virtual wind tunnel, with the model of the plane moving through a virtual atmosphere. Because of this, X-Plane arguably does a better job of handling situations near the edges of the flight envelope, which is where you might find yourself in a spatial disorientation situation.

Another difference is the ease with which new planes, panels, and instruments may be created. I find that the Plane-Maker program that comes with X-Plane is easier to use than the System Developers Kit (SDK) that is available for FSX. So if you want to manufacture a simulation of one of your own aircraft when the make and model isn't available or the instruments just need to be rearranged to match what you see on your panel, X-Plane is worth a close look.

Both FSX and X-Plane come with airports and scenery as well as NAVAIDs for the whole world. The airplane and scenery graphics are better in FSX (although they can be quite processor-intensive to display) in that they show more detail with many large cities represented quite accurately. Both systems can provide convincing visual transitions from IMC to extremely marginal visibilities at the end of an approach. Both display nighttime conditions realistically for practicing dangerous night circling approaches.

The panels and instruments are quite comparable and terrain elevations are based upon nearly identical, accurate databases. FSX also offers a Garmin G1000 representation and third-party software offers a full-glass Avidyne Cirrus cockpit. The simulation doesn't have all the modes of the real thing, but it's close enough for some quality practice. FSX comes with a few more airplanes than X-Plane, but you can find others for free or for fee for both products from various online sources.

Making Stuff Break

The first step in creating a failure in either system is usually to select your plane and place it at an airport. Failures can be specified after you are in the air, however.

In X-Plane, you'd then move the mouse to the top of the screen to make the menu bar appear. Next, choose Settings > Equipment Failures. To create the pitot-tube failure we mentioned earlier, select the Equipment 1 tab and the Pitot tube 1 blockage. You can then select from the various failure modes, including a specific time, altitude, and airspeed if you want.

In FSX, you'd press the alt key on the keyboard to expose the menu bar at the top of the screen. Choose Air craft > Failures. Select the Systems tab and scroll down to Pitot Tube. Now you can check "failed" to have the instrument failed as soon as you return to play, or check "Armed." If the failure is armed, you can set the range of times during which the failure will occur.

After the failures, both panels show zero airspeed, leaving you to survive the approach using what information you have left at your disposal.

You can find information about FSX at www.microsoft.com/games/ flightsimulatorx/ and you can down load a free demonstration version. The demo has a few planes, 12 airports in the West Indies, and no failure capability. The full product sells in stores or from Internet vendors for $40 to $70 and requires Windows.

A free, fully-functioning download X-Plane is available at www .x-plane.com. The joystick control cuts out after six minutes if you have not purchased the product. The cost of X-Plane is $39 if you want scenery for only one part of the world or $49 for the full set of seven DVDs that cover the whole earth. X-Plane runs on Windows, Macintosh, or Linux operating systems. Both FSX and X-Plane now require DVD capability on your computer.

Neither system is legal for logging flight time or IFR currency, but the angels don't care what your log book says. Time spent playing these games is time well spent toward real-world proficiency.

Chuck Bodeen is an aeronautical engineer and flight simulation enthusiast.

WONDERING HOW TO TRAIN WITH YOUR PC? READ THE BOOK

There are at least two books out there specifically on training with the "game" Microsoft Flight Simulator.

Microsoft Flight Simulator X for Pilots (Wiley Publishing, ISBN 0764588222) is by Kevin Lane-Cummings and some guy who edits a flying mag you might know. The book is geared toward flight students, either pursuing real-world flight training or just looking for the most realistic virtual training experience. It's organized into sections for Sport Pilot through ATP. Every chapter contains sample flights for the reader to try out on their own Flight Sim and some contain demo movies of the authors flying maneuvers. The files for these flights and movies must be downloaded from the Wiley web site.

Bruce William's Microsoft Flight Simulator as a Training Aid (ASA Publishing, ISBN 1560276703) is organized by how Flight Sim might be used by pilots, virtual pilots, and CFIs. This makes the book much shorter and to the point than FSX for Pilots, but not quite so step-by-step. William's book includes a CD-ROM with over 150 sample flights and supporting documents that let the reader practice each specific area where Flight Sim makes a good training tool.

One thing both books do is give practical uses for Flight Sim, with tips like flying to an unfamiliar airport virtually as a dry run for flying there in the real world. The visual representation of terrain and towns is so accurate it actually helps you find the real airport and anticipate issues before you blunder into them in flight.

--Jeff Van West
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Title Annotation:TRAINING
Author:Bodeen, Chuck
Publication:IFR
Geographic Code:1USA
Date:Aug 1, 2007
Words:1738
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