Old habits die hard

Flying Safety, June, 2002 by Bruce "FM" Edwards

The old adage says "train the way you fight." This sounds like a good idea, but it means that your training had better be squared away and it should be reflective of the way you want to perform in a crisis situation.

This article examines the way some design and training practices may have contributed to loss of aircraft. The shutdown or pullback of the wrong engine in twin engine aircraft during an emergency procedure can be corrected in some instances, but can lead to total loss of the aircraft under other circumstances.

The story about how we set ourselves up for this human factors problem is a three-part one: design, training and interference.

The design issue is one that we have recognized for many years. The throttle quadrant on twin-engine USAF aircraft is pretty standard and has not changed despite many different jets and many different missions. This design is found on the A-10, A-37, AT-38, FB-111, F-4, F-5, F-15, F-22, F-101, F-111, OV-10, T-37, T-38 and SR-71. The issues relate to the placement of the microphone button and speedbrake switch. The buttons are found on the right throttle only--this means single-engine flight and approaches are much easier with the left engine shut down or in idle and the right engine being manipulated for flight. The difficulty arises when you shut down the right engine. You now have to adjust the throttle with the left control and move to the right throttle for radio calls and speedbrake usage. Pilots are generally quick to figure out that one method, flying with the left engine shut down, is much easier than the other. This leads directly into the training aspect.

The way that we currently train and stay proficient in single-engine operations is to log events for currency purposes. Being the intelligent type, we tend to do most of our single engine ops in the way that makes sense--the easy way. We typically simulate the left engine as failed and conduct a flawless single-engine approach and landing. We go back to the squadron and log sim single-engine on the event tracker, and everyone is happy. Here is where the interference plays a part.

Habit pattern interference is where habit patterns interfere with some procedure. "Sounds simple enough," you say, "What does this have to do with emergency engine shutdown?" If you have been paying attention, you can answer the question yourself. If not, here you go. The critical actions that must be quickly accomplished under times of severe stress tend to revert back to learned behaviors--habits. These habits can be very helpful because they require little conscious thought and can be quickly carried out. They can be deadly if applied to the wrong situation. This is habit pattern interference.

When a pilot sees a fire light during low level flight ops, multiple actions must occur almost simultaneously to safely recover the aircraft. Ground avoidance and flight path deconfliction are just two, but the proper boldface procedure must also be applied to the affected engine. When under stress, many aviators revert to habits; in this case they have practiced pulling the left engine to idle / off and also pushing or pulling fire buttons / agent discharge, firewall shutoff, etc., to accomplish the boldface. When you have an engine on fire and you shut the other engine off, you don't produce a lot of thrust, and you don't keep flying very long. If you have enough altitude or smash, you might be able to fix the problem before resorting to the silk descent. If you are out of thrust and options, you may have to give the jet back to the taxpayers in its primitive form--molten metal.

Now that you know how you can be set up to make this mistake, you might want to know why and how I know about it. Well, I saw some mishap data and I also noticed that sim single-engine approaches were almost always flown with the left engine in idle. I began to wonder (and I needed a research topic), so I went to the Safety Center and looked at the database. My hypothesis was that if this never occurred, the improper engine shutdown would show an equal amount of left and right engines accidentally shut down, leading to loss of the aircraft. There was no data on the times when pilots recognized the problem and shut down the correct engine, or the times when they figured out the mistake in time to recover the good engine and shutdown the bad one, because these events are not tracked. I looked at 2095 USAF class A mishaps from 1971 to 3 April 2001. Of the 994 mishaps which met the aircraft criteria, 99 were engine-related. Out of the 99, three were found as "definitely" and three were found as "probably" having the wrong engine shut down. So this was a rare occurrence, but it still caused the loss of life and six USAF aircraft.

Now here is where it gets interesting. All six airplanes had the left engine shut down or pulled back when the right engine was the one that was affected. So this means that perhaps there is a link between the design, training and habit pattern interference.