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"Undetermined Power Loss"  by Gene Benson

Published: May 1, 2012

Well-maintained Continental and Lycoming aircraft engines installed in certificated airplanes are very reliable. Though ancient when compared to the high-tech automotive engines in use today, they are proven designs that have been perfected to achieve superb reliability. Yet sometimes power is lost. Yes, I prefer the term “power loss” to “engine failure.” We should not accuse the engine of failure when an error not related to the engine manufacture or design is made.

Poet Thomas Carlyle, translating from the German, wrote, “Silence is golden.” That is certainly not true when it comes to our engines. I am seeing more and more NTSB accident reports with a probable cause finding that includes the phrase, “Loss of engine power for undetermined reasons.” That is disturbing for two reasons. First, we seem to be having more incidents of power loss than in the past. Second, if we do not learn why an engine stopped producing power, we cannot take steps to prevent the same thing from happening again. I believe that the NTSB and the engine manufacturers make a good-faith effort to determine the cause of the power loss. But if the engine is put on a test stand, fuel is added and it starts right up, it is difficult to know what went wrong. Even in the case of damaged engines, the investigators go to great lengths to find the failure but sometimes everything checks out.

Some of those accident reports hint at a possible reason for the power loss but the evidence is not conclusive so the cause cannot be stated. For example, undetermined power loss will be included in the probable cause finding but the body of the report will include information relating to how the airplane was operating in conditions likely to produce carburetor ice. Since the ice would have melted before any accident investigators arrive, the evidence is gone. That reminds me of a TV show I saw many years ago. A man killed his wife by stabbing her with an icicle and the murder weapon simply melted, removing the key piece of evidence. But I digress.

I suppose that there are cases in which the pilot made a fuel management error, got the selector back in the correct position but not in time to restart the engine. Then the pilot either took that information to the grave or kept mum about it if he or she survived.

But I suspect that in most cases the surviving pilots do not know why the engine stopped producing power. One thing that has recently come to my attention is a concern about old fuel. Anyone with a lawn mower knows that old gasoline can be a problem. So we make sure that our airplane has fresh fuel after it has been sitting unused for the winter, right? Well, not always. It is hard to discard expensive aviation fuel. But even if “new” fuel is purchased, is it fresh? It seems that GA flying is down, especially over the winter months in the cold regions of the country. FBOs are also not likely to discard expensive fuel and there is no requirement for them to do so. But the pilot who conscientiously buys fresh fuel may actually be buying fuel that has been in the FBO’s fuel farm for a year. Does the old fuel cause a problem? Some people think so and are taking a closer look. In the meantime, it might be a good idea to purchase fuel from a facility that has a lot of traffic and moves fuel through their system fairly rapidly.

But in any case, we always must be prepared for that loss of power and the ensuing forced landing. We should periodically review the airspeed for best glide and any information the aircraft manufacturer provides about power loss and forced landings. It is essential that we have a plan for power loss immediately after takeoff. That plan must take the specific airport and its surrounding environment into consideration. For power loss at cruise altitude we should have at least the first steps of an engine failure checklist memorized and have ready access to a hard copy for reference. Also readily available and frequently reviewed should be a forced landing checklist that specifies how we want the airplane configured and whether or not cabin doors should be unlatched. If we fly over water, we should make sure that we have flotation gear and that it is in good order. Twenty year old vests with inflation cartridges might not cooperate. Being in the water would be a really bad time to find that out. We should also be familiar with the operation of the flotation equipment and in turn, brief our passengers. Of course, flying over water requires knowledge of ditching procedures which will be different from procedures for a forced landing on the land.

And we must make sure shoulder harnesses are fastened. Don’t have shoulder harnesses? Spend the money and get them. In my opinion, that is an investment that simply must be made. The NTSB states that the risk of serious or fatal injury in a crash is reduced by 50% if shoulder harnesses are used as opposed to a lap belt only.

And, we must think about what happens in the hours after a successful forced landing. Help might not arrive quickly so we should always fly with the idea that we might be spending the night in the terrain over which we are flying. If it is not practical to wear clothing consistent with a night in the woods or a hike out of the woods, we should pack a small duffel bag with, at a minimum, some appropriate clothing, snacks, water, and a small first aid kit. We should wear or have available shoes appropriate to walking out of the kind of terrain we are flying over.

Even though loss of engine power is still quite rare in general aviation airplanes, it happens. Of course we must take all steps possible to reduce the probability of having a power loss event. A good pilot plans ahead. Let’s make sure we have planned ahead for a power loss just in case. The only thing worse than a noisy cockpit is a silent cockpit.

 

Gene Benson

Gene Benson is a well respected FAA Aviation Safety Counselor with over 14,000 total hours under his belt. Through CNYAviation.com and his own website, genebenson.com, he hopes to spread the word about what we as pilots can do to keep ourselves and our passengers safe. He has been writing articles for CNYAviation.com's Flight Safety section since 2007.

 

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