This concern arises nearly every time we discuss operating and/or flying large airplanes with piston engines.  I've heard it – and so have many others – during various seminars, ground schools, forums, impromptu conversations, etc.  It appears to me that some pilots or mechanics are letting their good sense be overridden by something they’d heard.  It’s based upon good intentions – but part of their conclusion somehow went completely awry.

If I remember correctly, this “day’s work for a day’s pay” philosophy was applied on the airline.  Meaning that our chief pilot (Art Hinke) asked the pilots to make an honest effort to operate our aircraft engines by the “one inch of  manifold pressure for every hundred RPM” rule of thumb all day long. This effort was how the airline attempted to deal with the “reciprocating loading” problem.  However, he also recognized that it was also a matter of both practicality and necessity to operate at less than this on base leg and final approach.  In other words, “don’t put yourself, the passengers and the airplane in a dangerous situation by mindlessly following a rule”. 

To write yet:

Bad low approaches

Trees waving in front of the runway lights at night?

At low airspeeds, is the R/L 1”/100 RPM valid? Concept of prop driving the engine?

An everyday, normal approach should look just like an ILS glide-slope to you, (2½ or 3 degrees on average). This is where your perception should be at its sharpest, after all this is the same approach that you fly everyday so your judgment should tell you very accurately if it isn’t according to this, things just won’t look right.  Right?

R. Sohn   © 2002

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