Monday, January 28, 2013

Most Dangerous Time for a Pilot

Pilots are more likely to have an accident when landing than any other time. Skids off the runway, collapsed landing gear, wing tip strikes, ground-loops… all are rooted in three fundamental mistakes. How these mistakes cause such horrendous problems is not always obvious.

Flying with my friends in a pretty red, white, and blue Cessna 172, we were going for lunch at a small country airport in Northern California’s Central Valley. When I landed I thought that I had performed like a thousand-hour pilot. I felt great.

My second landing (just a moment later) was not as smooth; a gust picked me up and put me down – on the taxiway. I will never forget the smirk on the face of the pilot taxiing in the opposite direction as he held short for me to exit onto the ramp. I will always remember the half-smile and shaking head of the other pilot as he waited for me to taxi clear. I mumbled some stupid excuse to my passengers. In just one landing I had made the three most common accident-producing mistakes in aviation.

I could not think about much of anything else until I understood what I had done wrong and what I had to do differently to keep it from happening a second time. I found out that the National Transportation Safety Board writes that forty five percent of the weather related accidents are caused by wind gusts and crosswinds. Much more than 45% seemed reasonable to me then. I want to tell everyone who will listen about some techniques that will keep a pilot from getting into trouble in the first place. To understand the techniques that I am about to describe, I would like to explain the major causes of landing accidents as well.

If you have an angle of attack (airplane nose high enough or low enough) that produces no lift, no gust can pick your airplane up. My mistake was that the nose was neither high enough nor low enough. When the wind gusted, the wing’s lift put us back in the air.

There are two different orientations relative to a wind gust that prevent a wing from producing lift. A wing that is not pitched up at all produces no lift. A wing that it really pitched very high, above its stalling angle, produces no lift in a strong wind. So the technique, I am sure your instructor told you this, is to keep the airplane flying as long as you can; putting the angle of attack high enough to ignore even the strongest gust. With the plane in a level attitude after landing, a strong gust will not pick it up. This does not address the problem of a crosswind.

As long as the pilot is slipping sideways as fast as the wind but against it or as long as the landing gear has enough traction, a crosswind cannot blow the plane off the runway.

That is why I have always landed using crosswind landing techniques. Keep the plane over the center of the runway with ailerons and pointed down the runway with rudder pedals. This ensures that the plane stays in the center after landing. I have just described cross controlling.

Landing too fast or too far down the runway is always caused by the same mistake: failing to control the approach glide. Mastering the approach glide can prevent more problems than I can count.

 It is very easy to control an approach glide. Just remember two important points and keep them in mind as you approach the runway. Changes in pitch attitude impact airspeed almost immediately. Second is that the path an airplane follows through space can be changed very quickly with a change in power.

You have no hope of flying repeatable, precise approaches if you do not maintain constant airspeed by changing pitch and power at the same time. Just remember, “Power up, Pitch up” to maintain constant airspeed.

Once you have found the combination of power and pitch that gives you the desired approach indicated airspeed, adjust your glide path until it projects to the right place on the runway.

I would like to talk you through an approach. Suppose that after configuring your plane to land, you want to fly your approach at sixty knots. Looking out the window (as I know you do 99% of the time during an approach) you notice that the point on the ground that appears to be staying in the same spot on your windshield is one of the approach lights about 500 feet short of the runway. You know that the best place to glide toward is the base of the runway numbers. You add 200 RPM to the engine and make a corresponding pitch up to maintain 60 knots. You are dismayed when you realize that you are now gliding too far down the runway. So you reduce your power by 100 RPM and make a slight pitch down correction. This process of continuous corrections is repeated until you are ready to raise your nose as you flare from the approach glide to slow flight over the runway. You will arrive at the right place, in the right configuration and airspeed to make landing to brag about.

So the three things that you need to do are to control your approach glide precisely, cross control before and after landing, and keep her flying as long as you can after you flare.

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