Originally Posted by
Big Pistons Forever
With not much flying going on I have been giving some of my X students scenario’s to keep the grey matter exercised.
The latest is the following scenario which happened to me exactly as described
I was flying along at 3000 ft AGL in cruise in a C 172. Suddenly with no warning the engine started running very roughly with the engine RPM varying up and down by 500 RPM and a sufficient loss of power it was doubtful level flight could be maintained. T & P were indicated in the normal range.
What would you do?
Had exactly that in a carb'ed C172 cruising at 4,000ft.
I just pulled the logs and audio to recall the timings.
0. engine starts to run rough (01:31 in flight)
1. transfer remaining excess speed into altitude and trim for 70-80 MPH max Glide (gained about 350ft)
2. orient for terrain, check for time available for actions (01:32h in flight, engine partially running)
3. try Carb heat hot, observe
4. try Mixture full rich, play throttle, observe
5. airfield behind in gliding distance identified, initiate turn to field (01:33h in flight)
5. check Magnets right, left, both, observe
6. check fuel valve on, do right, left, both, observe
7. engine still running rough, a bit smoother on optimized carb heat (01:35h in flight)
8. radio call to airfield with no luck, no answer
9. radio call flight information, squawk 7700, inform going down to airfield
10. nice chat with information on the weather, why neither I nor they get contact to the field and that they'll follow me down
11. landing with rough engine (01:43h in flight)
12. inform information by radio of landing fine and am going to investigate and come back later
13. parking, opening cowling, checking engine status
14. nice police couple arrives to check for me, also guys from the field arrive
15. called shop mechanic and discussed options on field fixes
16. tried to fix, but could not find real cause, engine now running almost fine
17. called shop mechanic and discuss findings
18. decided to leave the aircraft at the field, phone flight information and inform
19. tied down with beautiful help of the airfields guys
20. was driven by flying club member by car to the next railway station
21. couple of days later shop mechanic drove to field and flew aircraft to shop
Cause identified: bad cylinder at 120 SMOH.
Looks like this:
