A Review of Old Wives Tales

Tale Number One—"The most likely time for an engine failure to occur is at the first power reduction after takeoff." Every individual who pilots an aircraft has probably heard this statement at some time. Is it a true statement? We will venture a guess and say that perhaps it may have been at some time in the distant past.

Several years ago this question was asked of me and it led to questioning some FAA employees and a number of other pilots about where the justification for this statement might be found. After several weeks of poking into this subject, it was finally necessary to conclude that we could find no justification - that it was simply an "Old Wives Tale."

A letter which recently came from a Flyer reader takes this one step further. First it appears that there are many who continue to repeat this tale. This caused our reader to delve into the subject a little deeper - perhaps a little more scientifically than I did. Our reader studied a computer readout which had data on incidents of engine failure over a recent three year period. Based on the material in that report, this reader concluded that engine failures during takeoff are quite rare, and that failures during cruise are far more common. This does seem logical since the engines of fixed wing aircraft run a majority of their operating life in the cruise power range.

Our reader also had a very believable theory about how this tale may have gotten started. He wrote, "It seems likely to me that this idea got started when twin engine flight instructors would simulate an engine out during takeoff - right about the time that the student put his hand on the prop control to reduce power.... Gradually the idea was propagated that this was the most likely time for an engine failure, when in reality it was a likely time for an instructor to simulate a failure."

From these two searches for justification - with none being found in either case, I believe it is fair to conclude that "the idea of an engine failure being most likely to occur at the first power reduction after takeoff" is in fact an old wives tale. For the sake of safety, lets stop repeating this false tale and start promoting the idea that we should be ready to deal with power failure at any time.

A second old wives tale is still being promoted by some individuals. This tale involves the constant speed propeller and goes like this: "The RPM in hundreds should not be exceeded by the manifold pressure in inches of mercury." Referred to as a "squared power setting" (i.e. 2400 RPM x 24 inches of MP), it appears that this tale may be the result of a carry-over from some models of the old radial engines which were vulnerable to bearing wear at high power settings. Changes in engine design along with improved metals and lubricants permit changes in the operation of modern flat, opposed cylinder power plants.

Any pilot who believes that squared power settings continue to be necessary should be urged to read and understand the information in the Pilot’s Operating Handbook (POH). While there are limits to the power which should be taken from most engines, particularly those which are turbocharged, the combinations of RPM and MP listed in the power charts of the POH have been flight tested and approved by the airframe and powerplant engineers. For example, if the POH chart lists 2200 RPM and 26 inches of MP as an approved power setting, pilots should not be apprehensive about using that setting if it meets their needs.

Isn’t it strange that some bits of information come to be believed by large segments of a population even when they are untrue? The two issues discussed above are good examples. Will it ever be possible to get all of our fellow pilots to reject the two false ideas outlined here? Let’s keep trying.