September 1, 2012
By Barry Schiff
Last month in this column ( “Proficient Pilot: Look, Ma, No Rudder!” August 2012 AOPA Pilot), I described an embarrassing situation in 1975 during which I had made several flights in a factory-new Aerostar 601 without realizing that the rudder had never been connected to its cables. Although nothing serious came of it, the potential had existed for tragedy. Fortunately, problems associated with the primary flight controls are rare—but not so rare that they can be ignored.
Some years ago, a private pilot getting checked out in a Cessna 182 was asked by his flight instructor to roll into a steep turn. While the pilot was maintaining altitude during the turn by applying back-pressure to the control wheel, the wheel fell limp in his hand. Pulling back had no effect because of a failed elevator cable.
Given that dramatic situation, what would you have done to restore and maintain control of aircraft attitude?
A typical response would be something such as, “Well, I’d use elevator trim to control pitch.”
That’s a valid answer until you take the question one step further and ask, “How would you land?”
Those same pilots probably would say something such as, “I’d control my attitude and descent profile with trim and power.”
The answer seems logical but implies that they likely have never tried it. Flaring and touching down using only power and trim is far more challenging than you might imagine. Yes, you can use power and trim to make a stabilized approach toward the touchdown zone of a runway, but only to a certain point. Then comes the big surprise. As the airplane descends into ground effect (at a height above touchdown equal to the wingspan of the airplane), the nose will begin to pitch downward. Unless a pilot anticipates the direction and magnitude of this pitching moment, he likely will land nosewheel first and eventually break something. It takes a deft and timely combination of trim and power to make a safe landing without an elevator. This nose-down pitching moment is the result of changing airflow that occurs as the influence of ground effect increases. Similarly, an airplane tends to pitch nose-up as it leaves ground effect after takeoff, although a pilot adjusting climb attitude after liftoff tends to camouflage this effect.
There is, however, a safer and easier way to land an airplane following the failure of an elevator cable.
Although you cannot raise the elevator by applying back-pressure to the control wheel (in this case), this does not mean that you cannot lower the elevator. There are two cables connecting the control wheel (or stick) to the elevator that control pitch; one cable raises the elevator, and the other lowers it.
A clever way to restore pitch control, therefore, would be to apply substantial nose-up trim, much more than you would ordinarily need. You could then apply nose-down elevator to prevent the nose from rising excessively. From then on, you could modulate forward pressure on the control wheel to maintain the desired attitude. In other words, you would ease forward pressure to allow the nose to rise and push a bit more mightily to lower the nose. The point is that you can maintain any reasonable pitch attitude by varying forward pressure on the control wheel.
Flaring for landing could be made by gradually releasing forward pressure on the yoke.
If the cable used to lower the elevator were to fail, you could restore pitch control by applying substantial nose-down trim and modulating back-pressure on the control wheel to maintain the desired attitude. In other words, you would release some back-pressure to allow the nose to go down and pull harder to raise the nose.
Unless both elevator cables were to fail or become disconnected (a virtual impossibility), a pilot experiencing a single-cable failure has the capability to make a safe landing as long as he has previously thought about how he would handle such an emergency. A pilot confronted with this problem should consider making a no-flap landing. Extending flaps creates strong pitching moments that can be difficult to arrest when only limited pitch authority is available. Landing with flaps up also places the airplane in a relatively nose-high attitude that reduces the amount of pitch authority needed to flare. Finally, try especially hard to avoid a go-around. The pitching moments at such a time can be particularly difficult to overcome with limited pitch control.
The nature of this emergency and the increased landing distance associated with a no-flap landing suggest that the pilot should attempt landing at an airport with a long runway.
Although one can practice landing using the described procedure, I urge that no one do so unless under the watchful eye of a competent instructor who has himself performed this maneuver.
Visit the author’s website.
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