Eye of Experience #62: What's Wrong with Attitude Instrument Flying?
Are pilots learning the safest way to fly on instruments? Or are they missing a piece that long ago was the standard -- how to fly WITHOUT the attitude indicator? AVweb's Howard Fried has seen many students come and go, and he says partial-panel training is only part of the story.
My two previous columns on the subject of attitude dealt with the hazardous attitudes within ourselves that have been identified by the friendly feds. This time we'll be discussing the attitude of the flying machine itself as it makes its way through the air.
What's wrong with attitude instrument flying? In a word, nothing! That is, if it is done right. This column was inspired by one of Peter Garrison's fine features, Aftermath. In the September, 2002, issue of FLYING magazine, the feature was titled, "Spatial Disorientation," and dealt with the accident in which the governor of Missouri, his son and one of his aides lost their lives. Although Garrison's analysis is excellent, as I see it he missed the most important point. The governor's son, acting as pilot in command, had come to depend entirely on the attitude gyro when operating in IMC (instrument meteorological conditions), as so many other modern instrument pilots are prone to do.
I learned to fly on the gages by the Stark system -- 1,2,3 -- needle, ball, and airspeed. We used the needle in what was then called the turn and bank instrument (now the slip and skid, or turn coordinator) to control skid with the rudder, and the stick (or yoke) to keep the ball centered. First you centered the needle with the rudder, then the ball with the stick. How's that for the modern "step on the ball" theory? We then controlled pitch by the airspeed indicator. If you were going too fast, you raised the nose a bit, and if too slow, you pitched a bit down. In those days, when airplanes weren't nearly as inherently stable as they are today, it was quite a task just to keep the airplane upright. Meanwhile, your total attention was focused on listening to the aural radio range for navigation, listening to the signal put out by the old four-course Adcock Radio Range Stations. One could easily lose a pound or so of sweat just flying a two- or three-hour cross-country in instrument conditions. If the radio put out a steady tone due to the overlapping of the A (dit dah) and the N (dah dit) you were on course (flying the beam), but if you wandered off course the A or N would bleed through. What a wonderful thing was the VOR! Now it is being replaced with GPS.
A Better System
Meanwhile along came Attitude Instrument Flying, and life became infinitely easier. The old needle, ball, and airspeed system worked, but there are some flight conditions in which it doesn't. The modern Attitude Instrument Flying system always works under any flight conditions, but only if it is done right. The sky is full of instrument-rated pilots who ignore everything else and fly happily around using the artificial horizon (attitude gyro) to the exclusion of all else, and for the most part they can get away with this kind of activity; but among other faults, this procedure is inefficient. It produces slightly sloppy results. It is much easier to accurately sight a rifle than a pistol, and this kind of flying is like sighting a pistol. If one uses the heading indicator as the primary instrument for roll (bank) it is more like sighting a rifle. The Artificial Horizon, or Attitude Gyro, is a performance instrument. It should only be used when the pilot wants to do something, and should not be included in the ordinary cross-check (scan). If the pilot wants to climb, he or she should pop the little airplane in the attitude gyro up one bar width, and after the climb is established, go to the vertical speed indicator to determine the rate of climb. (Unless it is an instant Variometer -- a glider-type instrument -- the vertical speed indicator has quite a lag and is only useful after the climb or descent is well-established.) In establishing a turn, the attitude gyro is used to initiate the turn and determine the degree of bank desired, and the amount of back pressure on the stick or yoke to compensate for the loss of vertical lift caused by banking the airplane. The turn coordinator is used to determine the quality of the turn. But in straight and level flight, the attitude indicator shouldn't even be included in the scan. This may sound like heresy since, as I mentioned, the sky is full of instrument-rated pilots who use the attitude indicator to the exclusion of all else when flying on the gages, but, honest folks, it is not the recommended way of doing it and is infinitely less efficient. And if you lose the attitude indicator, unlike the governor's son, you won't become spatially disoriented, enter a "graveyard spiral" and die!
Nowadays in flying a desired heading, we "step on the ball," and use the heading indicator (gyroscopic compass) to keep the wings level. Remember, if that thing's turning, you're banked! And a corollary of this is simply that the numbers get bigger on the right! So, in effecting a change in heading, the pilot should establish a bank with the performance instrument (attitude gyro), then go to the heading indicator, and when the appropriate number starts to come up, go back to the attitude gyro and level off. Then go back to scanning the heading indicator and altimeter, and occasionally including the engine instruments.
I don't know if vertigo and spatial disorientation is the same thing, or if vertigo leads to special disorientation, but I do know this: I have experienced vertigo once (and only once) and I found it to be an extremely interesting phenomenon. On a good VFR day I fell in on final behind a heavy transport-category airplane, a classic set-up for wingtip vortex (he was low and slow in landing configuration). I was driving a Cherokee Six, and in the right seat beside me was a highly qualified pilot. Sure enough, we got tossed around by the wake turbulence from the big bird ahead of us. After I got the airplane straightened up and perfectly level, I had an absolutely overwhelming feeling that we were in a steep left turn. It took all my willpower to force myself to ignore this false impression and concentrate on the gages, which told me that we were in a wings-level attitude, descending on final just as we were supposed to be. My companion told me he had the same uncanny experience. Weird. Had I acted instinctively and followed my feeling, no doubt we would have ended up in a classic graveyard spiral.
Doing it right -- the way the FAA recommends -- is not only infinitely more efficient, but it is actually easier. I'm confident that had Roger Carnahan, the pilot of the accident airplane about which Peter Garrison wrote, had been using his directional gyro (heading indicator) as the primary source for bank information, the fatal accident might well have never occurred.
Of course, the primary instruments are supported as follows:
- For pitch, the altimeter is supported by the airspeed indicator and (after the climb or descent is established), the vertical speed or rate-of-climb indicator.
- For bank (roll), the Heading Indicator (Gyro Compass) is supported by the turn and bank (turn coordinator).
- And, finally, for yaw (controlled nowadays by the rudder), the spirit level (ball in the turn coordinator) is supported mainly by an educated ass.
The Deadly "Graveyard Spiral"
The following scenario has been repeated again and again. When a non-qualified pilot blunders into IMC (or an instrument-rated pilot becomes distracted while in IMC), just the weight of the hand on the yoke causes the airplane to bank slightly to the left. At this point, cumulative causation comes into effect. The bank causes the nose to pitch slightly down, which in turn causes the bank to steepen, which causes the pitch down (and speed) to increase, which causes a greater increase in the bank, causing a greater increase in downward pitch (and speed). If unchecked, this process will take the airplane right into mother earth, nose first.
By actual test it takes only 22 seconds of this process for the pilot to be involved in a diving, grinding spiral. About now the pilot sees the airspeed indicator and says, "My God! Look how fast I'm going." The pilot then gives a good healthy tug on the yoke (all the way to the stop). This action, of course, overstresses the airplane, and pieces of metal with bodies included come falling from the sky. When they find the wreckage the next day, it is invariably scattered over a substantial amount of geography.
A pilot who flys in IMC by properly applying the attitude instrument flying method can expect a long, happy life flying in IMC, so long as you stay away from thunderstorms and keep out of icing.