Avoid this Auto Pilot Tragic Mistake

Having an autopilot in your aircraft has several advantages, including reduce pilot workload, and flying ATC assigned routes and approaches easier. However, if a pilot doesn't fully understand how to operate the autopilot in his or her aircraft, the auto-pilot can put the aircraft in an uncontrolled situation very easily if the pilot is not paying attention, and when this happens, the results are often tragic.

In this video I show, using a Redbird Simulator, how by forgetting to increase the power back to a cruise power setting, after descending with reduced power, the autopilot puts the aircraft into a stall condition and how it becomes very difficult to recover and control.

[justricardo]

you are right .. in GA aircraft you have to be very aware of your power settings .. you should be proficient at knowing whether you are at the wrong power setting by hearing alone. and stay ahead of the aircraft by anticipating the power changes as you descend / level off.

[CanardBoulevard]

This is why I a) have my GFC 500 autopilot configured to not allow my airplane to go below 90 kts (it will CAS alert and descend in order to maintain airspeed) and b) do not have my trim connected to the autopilot. I prefer adjusting trim myself, so I'm not surprised if the autopilot should disconnect for any reason, and I'm suddenly left with a hugely out of trim aircraft.

[ExpansionYZ]

Thank you for sharing. I wonder if this could explain the recent loss-of-control Pilatus in-flight breakup crashes.

[libertine]

It appears that more and more people are relying on autopilots. With this, more and more people are not scanning their instruments like they used to. People are busting altitudes because they are not monitoring their altitudes and counting on the A/P to do it. I know that I would forget sometimes that I had the autopilot on and would try to turn or climb. Once I felt the resistance I would turn the A/P off. No big deal because I knew what was going on. If I would have tried to overpower the A/P the trim would have tried to "correct" for my actions and the trim would have kept fighting me. That is until it ran out of trim and then would have disconnected. Very bad news!

The next thing that could happen is a "runaway trim". This is when the electric trim motor malfunctions. It could put trim in a maximum trim situation and try to keep it there. It may even not disconnect. So it is important that the pilot knows ALL the ways to shut off the A/P AND the trim motor. This may mean pulling the circuit breakers. So you need to know the emergency procedures for all eventualities of using the A/P AND where and which C/B are and what they control.

The next very dangerous situation is in icing. If there is any possibility or indication of icing the A/P should be TURNED OFF! Icing will change the flight characteristics of the aircraft. Stall speed could increase and the A/P may compensate until it can't anymore and disconnect. You will have a out of trim plane, with unusual flight characteristics, and possibly be on the edge of a stall. Two recent fatal incidents were likely due to ice with indications of A/P use.

The first was a Aero Commander. The pilot was told to descend then got off course and said that the A/P disconnected "due to turbulence". Probably icing also. He then reported icing still while descending. Then reported that the A/P was "acting up". He went into a spin right after that. This would lead me to believe that he was still using the autopilot while in icing conditions. Again relying on the A/P when he should have been hand flying.

The second was a PC-12. The pilot was going through a front in Wyoming. During the last portion of the flight, the pilot reported to the Salt Lake City Air Route Traffic Control Center controller the loss of the autopilot and declared an emergency. The controller queried the pilot on where he would like to land, however, received no initial response. The pilot then responded that he was trying to get control of the airplane to which the controller advised the pilot to let them know if he required additional assistance. The controller then advised the pilot of the minimum instrument flight rules (IFR) altitude and current altimeter with no further response from the pilot.

Why a loss of a A/P by itself would be a emergency hints at a over reliance on the A/P. Turbulence can make a A/P disconnect but icing could too. Icing would be worse because you now have a out of trim plane, closer to it's stall speed, and with unfamiliar flight characteristics.

Autopilots are great but they can't take the place of competent pilots.

[warren]

Thank you. You would think that since this is a basic step in cars after driving down a hill to a leveling of the road, done thousands of times, that it just couldn't happen in an airplane. But this error is what started a deadly chain of events in the Colgan accident.