Originally Posted by
flyinkiwi
It was a nil wind day, I had given the engine a thorough runup and there was nothing suspicious detected. We had just taken off and at about 100' the engine coughed. At 250' it coughed again, and then one of the magneto's failed. The engine cowling started vibrating quite badly so I smoothly reduced power and the shaking stopped at about 75% throttle. Even on one mag and partial throttle the plane was still climbing so I chose to return to the field instead of landing ahead. Had the engine quit at any time during the reversal turn I was well within gliding distance of a runway (thank goodness I was in a 172M and not the Arrow) and in the end I circled and put her down on a crossing runway.
I realize I didn't exactly do things by the book, so please, follow the advice of the vastly more experienced pilots and instructors lurking around rather than me.
I am a bit confused by your comment that "I didn't do everything according to the book". If the aircraft has enough power to maintain level flight or in your case still manage to climb then it by definition has not suffered an "engine failure" and so the "turn back" in the context of this thread does not apply.
Your decision to immediately return to the field and to do so in such away as to maximize your chance of landing back on the runway in case the engine suffered any further loss of power, strikes me as exactly "doing it by the book".
All the heated arguments of exactly what bank angle to use for a turn back and lengthy dissertations on changes in AOA, accelerating vs non accelerating turns, variations in the vertical component of lift etc etc, obscure the fact that what happened to you is a lot more common than the sudden complete engine failure at low altitude and that every partial engine failure will have different consequences and so ultimately making sure you fly the aircraft first and then picking a conservative course of action that will give you options should the situation deteriorate further is the best one can do....but I guess that is not as sexy as discussing hero pilot moves......
As an aside one thing that never seems to get talked about in flight training is knowing the minimum power setting to maintain level flight. In the average Cessna it is around 1900 RPM. In the event of a partial engine failure this is a good number to know. If the power winds back but you are still getting a solid
1900 RPM you will stay in the air, at least for now. Less than that and you had better be planning your forced approach.