However the engine malfunctions that the average PPL is much more likely to actually encounter is a rough running engine and/or a loss of some engine power. What to do about this often does not get covered in a systematic way in flight training. This IMO, is particularly true during PPL training where students will not have a base of experience to draw on and need some guidance on how to deal with in air engine problems.
I recently helped redo the emergency checklist for a local flight school and I addressed this issue in the non memory recall section of the emergency checklist (C172). The intent is a "check" for the pilot to use if he/she encounters an engine problem to ensure they have not forgotten any actions. It goes as follows:
Engine Roughness/Reduction in Engine Power
-Carb heat.........................................Full On for at least 30 sec
-Engine gauges...................................Check
(Note if severe carb ice exists engine will initially run very rough until ice has cleared)
If problem persists
-Carb heat........................................Cold
-Mixture ...........................................Full rich then lean to max RPM
If problem persists
- Mags............................................Select right and left mag individually
(Note if engine roughness is more pronounced on one mag select the other mag or both, whichever gives smoothest operation)
----------------Land at nearest suitable airport------------------------
If problem persists
- Fuel selector.................................Left tank for 2 mins
If problem persists
- Fuel selector................................Right tank for 2 mins
---------------Land at nearest suitable airport-------------------------
In addition to to this I have emphasized the importance monitoring the engine instruments in flight. Instructors should periodically and without warning cover the oil temp/press gauges and make sure the students know where the needle is actually pointing. (In the green is not a good enough answer
).Internal mechanical failures resulting in a total engine failure are the least likely cause of an engine failure but they do happen. The good news is there will almost always be some warning. Any internal misalignment or failure will almost always result in metal rubbing. This will cause a rapid rise in oil temperature with the oil temp gauge pegging at its maximum value. A dramatic drop in oil pressure will quickly follow. Any engine showing these signs should be presumed to be in danger of imminent total failure and appropriate actions to land ASAP should be taken. The only caveat is an open circuit in the oil temp wiring will cause the oil temp needle to peg at the highest temp. However in this case the oil pressure will be normal so it is likely just the gauge. However a landing at the nearest suitable airport would be prudent
The oil temp gauge failing is more likely then the engine actually suffering a catastrophic internal failure. It would be a pity if a student on seeing a failed gauge, wrote off an airplane on an unnecessary precautionary landing, an event I know has happened. If the oil pressure is normal there is essentially no way you can have an above redline oil temp. Obviously you still land at the nearest suitable airport though.
This does beg the question of what is "normal" oil pressure and temperature. Another area that usually isn't addressed in flight training. Oil temp and oil pressure effect each other. If you have just started your engine on a cold morning it would be normal to have the oil pressure every high, probably close to the upper redline limit with the oil temp at the bottom of the gauge. As the oil warms up the oil pressure will slowly reduce to a more normal mid gauge (ie 75 ish PSI) indication. However if you restart the engine after a short break on a 30 C day, you will see a high oil temp and the oil pressure will probably be in the yellow arc at low RPMs. Therefore a low oil press and/or high oil temp at start up on a cold day; or very low oil temp and/or high oil pressure after a short shut down on a hot day should be of concern.
A related issue is how "partial" is your partial power loss. As an initial guideline to new pilots I tell them for the C 172 a loss of RPM to below 1900 should be treated as an "engine failure" and a planned controlled forced approach should be carried out using what power is available to help control the aircraft. Above 1900 RPM level flight can be maintained, the aircraft can be manoevered and now some pilot decision making is required as to the best course of action and will obviously be situationally dependent.
