The Story

In 2000, I became a partner in a Piper PA-235 aircraft. Shortly afterward, the artificial horizon tumbled. It had been replace a few months before. When asked how long these units usually worked before a failure, we were told about 500 hours. As it turned out, the problem was caused by a leaky windshield, which dripped the corrosive Cape Cod rain onto the air intake filter of the unit.

But that number of 500 hours stuck in my mind. Any pilot will tell you that the artificial horizon is a critical instrument when flying IFR and an important one when flying VFR. We are taught how to fly IFR without it, but it is more difficult and requires combining information from several other instruments. The key to good IFR flight is practice and I wondered how many pilots' practice IFR without the attitude indicator. There have certainly been a number of stories in the news of aircraft that went down after the pilot reported trouble with the attitude indicator.

The problem was that the attitude indicator is a sensitive mechanical device. The best solution would be one that used no moving parts and was not dependent of delicate hardware. Well, the advent of GPS (Global Position Satellite) made such a system possible. The accuracy improvements provided by DGPS (Differential GPS) along the coast and the FAA's new WAAS (Wide Area Augmented System) which covers the entire United States made such a solution even better. With a simple WAAS, a processor, and a display, the attitude indicator could be replaced with virtually no moving parts (we still have cooling fans in the processor, but it is possible to build a unit without them).

From conception of the idea to flight of a working unit (using a portable PC and a GPS) took only 3 weeks. (This unit and the one being manufactured were limited to about 85 degrees of pitch or bank. The full sphere solution is more complicated and more expensive.)

But it didn't stop there. Once you have an accurate position sensor, that same system could also do the work of many of the aircraft instruments. I once added up the "used equipment" value of the instruments in our aircraft and it came to more than $20,000. By just adding more software to attitude indicator hardware, I would provide more capability than currently existed in that PA-235.

But what was needed? So I got to work on my wish list. I am a retired engineer. And I have to admit that, at my age, scanning the instruments during IFR flight is tiring work. So first on my list was to see how much information could be put on a single display without confusing the pilot. Many aircraft today (including the PA-235) combine a single navigation display with a direction indicator. But the attitude indicator is generally separate. Those went together very simply since we no longer had the mechanical problems associated with the combination.

Additional navigation indicators are generally separate, also because of the mechanical problems. With an electronic display, combining them was easy. Of course, VOR indicators required an indication of to-from and the pilot needed to know which navaid it referred to. No problem. Simply put the arrow right on the indicator line. A VOR indicator also needed a flag to indicate whether the signal was valid. Also not a problem here. If the WAAS is working, the signal is always valid. No hiding behind mountains or being out of range.

To provide other navigation locations, the PA-235 had an RNAV. Fine, that is a simple software task. But wait, we also know the position of fixes, airports, and non-direction beacons. Might as well let the pilot select these locations the same way as VORs are selected. For that matter, any of those locations can be used as either VORs (if you want to fly a radial to-from it) or as ADFs (if you just want to know which direction it is in relative to the aircraft).

Implementing the marker beacons required software to tell, each second, if the aircraft was in range of a marker. That meant a clever algorithm so that most of the beacon tests are excluded from such frequent testing. Of course, once the algorithm was there, it was a simple matter to also apply it to the 5,000 airports (only the public airports) in the system. Knowing which airport is nearest allows the system to, with a simple push of a button, lead you to land at that airport.

This brings me to the next item on my wish list. One problem that still plagues flying is that of disorientation. The FAA has been aggressively attacking the problem. The approach seen most often is a graphical presentation of the aircraft's position relative to the desired flight path. That works for me. And it probably works for more than 90% of pilots. But there are pilots who have difficulty with spatial relations. In the confusion of disorientation, such a pilot can't work out the steps. All such a pilot wants is to know which way to move the controls in order to get back to straight and level flight while the pilot regains his/her wits.

We solve that with a simple, diamond shaped, figure - the AIM figure. If the pilot presses the "Panic" button, the diamond will appear on the screen with the letter "P" in it. The pilot proceeds to push that diamond toward the middle of the screen with his yoke. If more power is needed an extended portion of the diamond also appears above the diamond, if less power, below. Following this simple set of instructions, the aircraft will be brought back to straight and level flight at an altitude at least 2,000 feet above the nearest airport.

As with all things, we did not stop there. As long as we have a way to direct the pilot, we might as well use it for other things. If he presses the GOTO button, the figure will lead him to the selected navaid. If that navaid is an airport, the pilot is shown all runways for that airport, listed in the order based on the current wind conditions. Each line item shows the direction, length, width, type of approach, and standard pattern for a runway. The pilot can simply press GOTO again for directions to approach and land on the preferred runway. Or the pilot may select one of the other runways, standard left, right, direct, or IFR-published approaches. While directing these approaches, five seconds before each maneuver change, a small circle appears at the appropriate corner of the diamond and a second-by-second countdown is started within the diamond. This allows the pilot to anticipate moves.

Where does all this data come from? The FAA publishes an update to all the navaid data every 56 days. The cost (last time we checked) was about $36 for the CD. This data is not copyrighted. We intend to extract the data needed for this unit (about 5 megabytes) and post that data on the web for download. We do not intend to charge for this service, but are hoping users will chip in about $5 per year to defray the expense.

The next logical step is to apply this AIM figure to an entire flight plan. This has also been done. The pilot lays in a point to point flight plan including altitude and the AIM figure does the rest. The system also provides simple ways to describe standard coast-guard search patterns and the AIM figure is a very easy way to maintain such patterns without any visual reference.

Finally, the first version of the VIP is directed toward the renter pilot. In general, the renter pilot has the least control over what equipment is available to him. The renter pilot is also forced to learn the equipment that happens to be in the aircraft that is available. There is much more functionality in this system than will be found in most rented aircraft. So an attempt was made to make this available and affordable to the renter pilot first.

As with any system, there had to be a number of compromises. In general, those compromises have only been made in the hardware. In this day and age, the unit should really be much smaller. We found that the hardware for such compact units was hard to find and significantly more expensive. During the design phase, we were able to cut about $1,000 off the sell price by using a standard desktop processor board.

The system contains an uninterrupted power supply. Computers are very finicky when it comes to power interruptions and cigarette lighter plugs are notorious for coming loose and causing an interrupt. The unit can be supplied with a small battery (saving 2.7 lbs. and about $15). That will keep things going for about 6 minutes. The large battery to provide about 3/4 hour of instrumentation in case of a full electrical failure (if you unplug it so the rest of the avionics does not drain the battery).

The unit draws about 5 amps from a 12-volt system. That could be reduced to about 3 amps if we chose to use a more efficient DC-to-DC power supply. That option is being made available, and will also reduce the weight in the full UPS version by about 4 lbs. because of the smaller battery and elimination of the inverter. But it will require a DC supply for use when running the unit at home (for updates of planning a trip). The high efficiency supply will increase the cost by about $300.

While we think the unit is better in many ways than the equipment currently on the market, it is not TSOed and must be considered supplementary equipment. It is clear that much of our focus has been on reducing cost, and we are not in the position to accept any liability for the equipment's use or misuse. How heavily you rely on the equipment is up to you.

We think the flying community needs this technology. We are targeting those pilots most likely to gain a big advantage. But we would be happy to license the technology and help others who have higher quality hardware incorporate this technology in their system.

Return to Virtual Instrument Pilot: