Monday, August 22, 2005

Reading Between the Lines

Flew with Joe again, finally. We were both concerned that he would have a repeat of his previous terrible flights. We had great visibility today, unlike the entire previous month. Around here, July is absolutely the worst month for haze. We chatted away during the preflight, as if there was no issue, but we both knew that today would signal whether or not he might be able to get his license anytime in the next couple months.

His struggles have been a little bit on the unusual side. Most student difficulties tend to fall into several neat little categories, which the FAA-required study material for CFI applicants tends to cover. But there are always the occasional troubles which standard instructor methodology doesn't really help. Sometimes you can't simply tell the student what to do, you have to read between the lines and figure out why he's making mistakes, when he knows perfectly well what he ought to be doing.

I've noticed something in him that I've seen before, but never really put to words: he tends to get off his assigned altitude and heading in between maneuvers. Not terribly uncommon there, but it always involved getting slow. I thought at first that perhaps he was compensating with the trim for a perceived difficulty holding altitude. But that theory went out the window today.

Then it occurred to me. His mistakes there were a result of having learned a certain lesson too well, and applied it in the wrong place. Slow flight is one of the more troublesome maneuvers for many students (and experienced pilots- but they'll never admit it). The thinking is perhaps a bit counter-intuitive. In the very beginning stages of flight training, while a student is trying to master straight and level flight both at the same time, the primary instrument for pitch information is the altimeter. Rather intuitive. If you are descending and don't want to be, pull back on the stick, and the descent will stop.

That method is fine for normal flight speeds, but in slow flight, when the wings are right on the edge of stall, pulling up won't help. This is one of the areas that I fear too many instructors don't understand as well as they ought to. An understanding of slow flight is critical for every level of flying a pilot will ever do. A pilot that doesn't truly understand it, doesn't know how to fly. He only thinks he does. Poor understanding of slow flight results in bad landings, inability to consistently do spot-landings, and many other minor flaws that may go unnoticed. Not to mention all the stall-spin accidents that happen year after year.

The important thing to remember about slow flight is that your control of the pitch affects airspeed, not altitude. Controlling altitude requires power. For that reason, books often refer to slow flight as a flight regime of "reversed command." The truth is, that is how airplanes fly. Always. The pilot's ability to cheat on control inputs during faster flight, is what tricks so many into believing otherwise. But factually, no matter what speed you fly, adding power is what makes you climb, and reducing it makes you descend. The elevator is only there to let you control the airspeed.

At this point, I would be remiss not to strongly recommend the old classic book Stick & Rudder. It is perhaps one of the poorest examples of writing I've ever seen, but the subject matter is indispensable.

Now, something to remember about the basic control in slow flight: while it may apply to all flight regimes, it is not always the easiest thing to do. Joe's steep turns have been a struggle, partly because he was using the wrong instruments to try to fix it when the attempts went wrong. In a bit of frustration with him today, I covered up the entire instrument panel for the maneuver, and he completed the steep turn well within the standards. He gained only 30 of an allowed 100 feet. Why? Because he was forced to rely on the more important things in that maneuver: the sensory, seat-of-your-pants assessment of angle of attack and bank. I didn't know at the time what exactly he was focusing on, but I knew it was the wrong thing. During the debriefing, he said he was using the artificial horizon for most of it, which I explained, distracts him from the more important parts.

Now, back to his post-maneuver tendency to climb. I've hammered into his head the basic control of slow flight, and got him taking it too far. Rolling out of a steep turn, he was climbing. At that point, he was relying on airspeed for pitch information, just like in slow flight. But airspeed is only an approximation of angle of attack, and it isn't accurate in banked flight. So right when he should have been pitching the nose down, he was distracted with the desire to keep his airspeed constant. By doing that, the excess power needed during the turn started us climbing. All he really needed to do- in lieu of quick, seat-of-the-pants evaluation, was to control the pitch with reference to the altimeter.

The solution: remember that sometimes, it is better to cheat.

Wait, maybe that didn't come out right. The right instrument to use is situationally-dependent. Joe knows all about slow flight, being an aerospace engineer. Sometimes that can be a hindrance to the learning process.

He has other struggles, as does everyone, but I think addressing this one will make the difference.

Tomorrow morning we get back to work on it in earnest. I'm really happy, because he has been one of my two most active students, and both of them were on vacation/business trip at the same time. It was making for some slow days. I know he is more comfortable now that we are not dealing with a heavy hazy every single day. Frankly, I'm glad for it too. Maybe we can overcome this particular struggle.


At 8:07 PM, Blogger brewsmith said...

Excellent post, very descriptive, almost felt like I was in the plane with you guys, thanks for the ride!!


Post a Comment

<< Home