Steve6443 wrote:
Read what Mike Busch wrote.
Let me rephrase by question then. How do you get pre-ignition after a few seconds of incorrect leaning? As far as I know, pre-ignition happens when some part of the cylinder or piston head gets so hot that it ignites the fuel/air mixture before the spark. How does this happen so fast?
This was not caused by detonation etc.
Something just broke…
Suspects might be an undeclared prop strike (those are often blamed for crankcase cracks), a conrod bolt not done up correctly or an old one re-used, etc.
The mixture thing is a complete red herring – he moved the mixture back using the vernier (turning the knob) so it wouldn’t have leaned it much at all. The first turn or two probably did nothing. These engines aren’t that fragile otherwise these aircraft would be falling out the sky all the time.
I would put money on that the bottom end was incorrectly assembled – perhaps an incorrect torque value used when fitting the rods, or perhaps a nut not torqued up at all.
Some debriefing and analysis by him.
Quite good to hear his side of why he did what he did. Well, it ended well. Just very expensive I guess.
I suppose who ever did that IRAN repair will answer to this.
’Luckily there was runway 08 right there off his left hand nose down turn."
He knew that runway was there.
Interesting analysis
It appears to me that he was given quite doubtful advice. The question will be, what caused the engine to fail in the end and who is responsible.
In any case, his engine woes should be at an end, as now he needs a new engine.
Airborne_Again wrote:
As far as I know, pre-ignition happens when some part of the cylinder or piston head gets so hot that it ignites the fuel/air mixture before the spark. How does this happen so fast?
Yes I’m with that opinion. This doesn’t happen seconds after start, more so as he didn’t lean far. This was maybe just until you would have noticed a drop in fuel flow, but not much. There are aircraft departing constantly with a too low takeoff fuelflow and they don’t explode like that. Of course takeoff power – or at least a lot of power – is one condition for pre-ignition. This was not related to him leaning that small bit.
In any case, that’s a horror.
Mooney_Driver wrote:
It appears to me that he was given quite doubtful advice
It seems he was driven by his need wish to be back in the air soon, which was not going to happen with Western Skyways or Continental with their current terrible backlogs. Someone offered a quick low-end rebuild and he took it. Too bad.
I am worried by the ownership experience story as this is a big deterrent.
He was ill advised to procure an aircraft like this without a proper pre-buy: I doubt his lifters were destroyed in the last 100hrs. Oil filter and borescope inspection in the pre-buy should have shown enough to drive a credit for a low-end OH from the seller. I shied away from a TSIO-520 engined 210 years ago exactly for that reason. The owner offered to lower the price $15k…I would easily have been that guy had I not run.
Also, his mechanic did not know how to properly troubleshoot the gear system on his aircraft and I am under the impression he busted the gear pump during ground checks, judging by this series of videos. The advise to continue flying after the last metal debris finding was also questionable and this story explains why mechanics shy away from on-condition maintenance and prefer component replacement.
The advice to replace oil every 50 hrs on a newly purchased TSIO-520 was also a bad-one, 25 with analysis and filter inspection is much more prudent.
The evident good piece of advice was that the first bad set of lifters had to be replaced before further flight.
