by Philip Greenspun, ATP, CFII, September 2009
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Ask a typical helicopter instructor "Why can't Johnny hover?" and the answer will be "Johnny doesn't realize how sensitive the controls are or what, exactly, they do."
This explanation is plainly wrong, given that a competent instructor can always teach a proficient instrument airplane pilot to hover within one hour. The airplane pilot has no idea how sensitive the controls are. He or she may have been recently flying a heavy airplane with a heavy yoke and a lot of inertia. Nor does the airplane pilot have a good feel for what each control does in the helicopter or the consequence of a 20mm displacement of the cyclic. Yet Johnny Instrument Airplane Pilot can hover and Johnny Never Flown cannot.
As an instructor, my best student ever was a U.S. Navy S3 pilot. I gave him the pedals, then the collective, then the cyclic in cruise flight. I took the controls over for landing back at Hanscom Field and gave him the pedals, the collective, and the cyclic in the hover. I never had to take a control back. He never lost control of the aircraft. After 20 minutes he could do virtually everything in the helicopter except manage an emergency such as engine failure. I took the controls away from him prior to the final landing only because it was on uneven grass.
What skill do these airplane instrument pilots have that a person who has never flown does not have? The ability to notice a change in attitude. The average person is taught to ignore attitude changes. Lean back 15 degrees in your desk chair. Are you now doing a completely different job? Your 350 lb. friend sits down in the passenger seat of your Toyota Echo and says "I need a Slurpee". Do you now have to take a different route to the 7-11 because the car is banked 3 degrees to the right? It does not make sense to pay attention to attitude in day to day life because it is irrelevant whether one is pitched up or down or banked left or right.
Aviation is a little different. Point the nose of a helicopter up 15 degrees and the machine will begin to fly backwards. Bank the machine 3 degrees and wait a couple of minutes; the helicopter will have completed a 180-degree turn.
As an instructor, it is your job to teach the things that are non-obvious. After 10 seconds it is obvious to any student that the helicopter controls are very sensitive and have a dramatic effect on aircraft attitude. You don't need to teach that.
Hovering a helicopter is as simple as holding the helicopter in a level attitude. What you need to teach the student is to notice a 1-degree change in pitch or bank and take action against the change. If left uncorrected, a 1-degree pitch or bank will result in the helicopter hurtling towards the other side of the airport. For a student who can notice a 1-degree change, at first his or her control inputs will be either too large or too small. However, within a few minutes, the student who can recognize the correct hover attitude will figure out how much cyclic is necessary to bring the helicopter back to where it was.
The typical instructor teaches the way he or she was taught. Put the student into the right seat and give him the controls. The helicopter nose will drop 5 degrees before he notices and 7 degrees before he pulls back on the cyclic. The control input will be too large, resulting in the helicopter going 10-degrees nose up. The same thing will be happening in bank. Now the helicopter is swinging through 40 degrees of attitude like a pendulum. At some point the helicopter gets near the ground and the heroic instructor jumps on the controls to save the machine from crashing. 9999 times out of 10,000 the instructor does save the machine, but that other time ends up costing an insurance company the price of a Robinson R22 (an R44 is a lot easier to save because there is so much reserve power with only two people on board a 4-seat ship).
Ask the instructor who wrecked the helicopter why he was letting the student swing like crazy and he will say "I didn't want to cheat the student by taking the controls away too soon. He needs to get a feel for how the helicopter responds."
Does he? Let's ask ourselves who needs to be able to take a helicopter that is swinging like crazy and put it back into a stable hover attitude. A CFI needs that skill. Why would we be trying to teach a guy on his second lesson how to be a CFI? If the student needs to learn to recognize a 1-degree change in attitude, how is it helpful for him to see a 40-degree change?
To teach a student what the correct hover attitude looks like, I want to spend as much time as possible with the helicopter in the correct hover attitude. As soon as the attitude is off by more than 5 degrees, I take the controls, put the helicopter back where it should be, and return the controls to the student. The result is more frequent exchanges of flight controls, but much less swinging, quicker learning, and, incidentally, less risk of crashing the helicopter.
The reduction of risk is incidental. I teach this way because the student learns faster, not because I am afraid of crashing a swinging helicopter (mostly I teach in the Robinson R44, which is much less prone to hover-teaching accidents).
A student's first hover lesson is typically towards the end of his or her first helicopter flight. We've been up in the air at 60 knots practicing attitude flying, maintaing airspeed, altitude, and heading. In the preflight briefing and before returning to the airport to commence the hover lesson, I tell the student that the challenge of hovering is no different than the challenge of flying in mid-air at 60 knots. The difference is that sloppiness is alarming when near the ground. In mid-air, changes in attitude will have the helicopter flying at 20 knots or 100 knots instead of the desired 60. Given that the helicopter is perfectly happy to fly at 20 knots or 100 knots, an inability to hold a constant attitude has little consequence. In the hover, however, the same changes in attitude will result in the helicopter swinging wildly or translating to the other side of the airport at a frightening pace over the ground. Reminding the student that the task and goal of hovering are the same as the task and goal of flying 60 knots enables them to use the skills that they developed in mid-air and makes them more relaxed when starting to hover.
At Hanscom Field the airplanes are usually using Runway 11-29. I ask the Tower for permission to land on the 1000' markers of Runway 5. Hovering over a smooth paved runway improves the efficiency of the machine, reduces the chance of a dynamic rollover should a skid contact the ground, and reduces the risk of hitting an obstacle. We now have a space 150' wide by about 2000' long in which to do whatever we want. Before giving the student any control, I ask him to look carefully at a runway stripe close to the helicopter. I then push the helicopter through some pitch and bank changes. I ask him to look at a tree or antenna at a far end of the airport and then do similar pitch and bank changes. I then ask "Do you get a stronger attitude reference by looking close or looking far away?" [almost invariably the answer is "better to look far away."]
Students typically work way too hard on the collective. This results in alarming height oscillations, but what's worse is the extra workload it imposes on the student. Every collective change requires a pedal change and the pilot in this case has only about 30 minutes of helicopter experience. I think the collective overworking stems from a fear of ground contact, so I give them a short demo of why ground contact is extremely unlikely if the collective is left more or less where it is. I tell them that each position of the collective corresponds to a hover height and that, especially in gusty winds, it is natural for helicopter to move up and down but that on average it will stay at whatever height is represented by that collective pitch. I have them follow with me on the collective in a 2', 5', and 10' hover. This shows them that if the helicopter is rising it is not going to climb to the stars and that if it is falling it will probably settle in at a new height rather than hit the ground. Finally I intentionally put the collective down to just about exactly the manifold pressure necessary for hovering. The helicopter sinks at an alarming (to the student) rate. I show them how the sink rate slows dramatically in the last foot or so due to ground cushion and that the helicopter either won't hit the ground or will hit gently. If the helicopter does plunk down, that's okay. The student should learn that the helicopter is reasonably robust if there is no side- or rearward drift on the skids.
Now it is time to give the students the controls. I give them the pedals first, reminding them that they will need to return the pedals to neutral prior to the helicopter completing a turn. Always start with teaching left pedal turns due to primacy and explain that right pedal turns are best avoided in American helicopters.
After they've got the pedals under control, I give them the collective and tell them to do nothing with it, accepting small changes in hover height that are due to wind gusts or power being diverted to the tail rotor.
Finally it is time to teach the cyclic. I take back the pedals and collective so that they can concentrate on (1) bracing their forearm on their thigh, (2) developing a kinesthetic feel for the neutral position of the cyclic, and (3) returning the cyclic to neutral after every input. I note that even the smallest cyclic input, if held, will have the helicopter translated to the other side of the airport.
At this point it is often time to go back to the hangar. If the student has been doing well, I'll give him or her all three controls and say "Don't worry about our position over the ground. We have half a mile of runway to ourselves. Just try to hold the helicopter in a level attitude."
There is no pedagogical value in letting a student swing wildly in a helicopter. To the extent that a student has trouble hovering it is because he or she cannot recognize small changes in attitude. Your job as an instructor is to help the student become sensitive to those small changes. The student learns nothing by swinging through huge attitude changes, except possibly how to terrify himself, spectactors, and the insurance company. You probably have good stick and rudder skills or you wouldn't have passed your CFI checkride. However, nobody can be a hero all day every day. Especially if you teach hovering on warm days with heavy students in two-seat helicopters, there will come a time when you can't save the ship. It doesn't make sense to wreck a $200,000 helicopter in service of a flawed teaching philosophy.
The author is a senior flight instructor for East Coast Aero Club's helicopter program.
Want to start training in Boston with East Coast Aero Club? Call 781-274-6322 to enroll, or email philg@mit.edu
Copyright 2009 Philip Greenspun.