Steve6443 wrote:
From experience of people flying in the local club, there have been numerous failures of Rotax because of a loss of coolant
Really? I would think after one such failure, the logic is to check that coolant level before each flight, and refit all flexible tubes after Rotax recommendation. Or at least tighten the clamps…
That “unknown” is a bit peculiar. Obviously an engine won’t quit without a reason. The most likely reason is perhaps mismanagement by the pilot? Maintenance causes 16% of failures, but how many failures does maintenance prevent?
There is a variety of failure modes in the fuel system. With a carb you can get various things e.g. a failure of the float valve. With a fuel servo you get others e.g. a failure of the diaphragm, and some servos have a separate altitude compensator which is another diaphragm which, if it perforates, gives you a rich cut and if you are at any decent altitude it stops the engine making power (you have to correctly identify that and pull the mixture lever back, but most pilots won’t know about that).
Throw in poor or nonexistent fuel status information (how many have a fuel totaliser and use it?*) I would have expected way more than half of in-flight shutdowns to be fuel related.
Bad maintenance is not likely to cause an engine failure on the Lyco/Conti types, unless you simply don’t put in any oil. You certainly don’t need to perform the 50hr service between Annuals; except for the oil change that is almost entirely precautionary.
When I ended up in a field after a stoppage, they never found out what it was. The engine, on its second flight out of maintenance and after refuelling, simply turned into a windmill, but restarted nicely later. After maintenance rummaged under the cowling for an hour or so I flew the aircraft back to the airfield (staying nicely in gliding range of emergency landing areas). With the head of the maintenance organisation on board…
Possible failures included
– Carb Icing (but highly unlikely, given the spread on the day and given carb heat was on)
– Fuel contamination (some debris found in the fuel line downstream of filter, but nothing conclusive)
– Pilot error (mixture pulled instead of carb heat applied? Again highly unlikely given the checks performed after the engine failed, which also included a tank switch)
– Some temporary induction blockage or other maintenance issue.
After lots of head scratching, the aircraft was put back into service “dual only” for 10 hours. Nothing ever happened again.
I got fuel servo icing twice. Once in 2014 and once in 2015. Not using alt air in -15C. A DA42 gets a dual engine stoppage too in those conditions, despite having a very different engine. And still some people deny this exists. This SR22 stoppage at FL230 is another one; that plane was sold instantly afterwards and no info ever came out on what (if anything) was found. So it isn’t surprising that a large % of stoppages remain unexplained.
Peter wrote:
Bad maintenance is not likely to cause an engine failure on the Lyco/Conti types, unless you simply don’t put in any oil.
That depends on what you mean by “bad maintenance”. A few years ago in Sweden, a Lyco on a PA28 threw a rod through the crankshaft because some bolt had not been tightened enough after recent maintenance.
(To make things more interesting, this happened over the Baltic Sea. The pilot managed to make a perfect deadstick landing in a field close to the shoreline without incurring further damage.)
But there are no “bolts” to tighten on these engines.
Only when they are opened up…
Also you do not re-tighten externally accessible bolts, because that results in over-torquing. A quick hand check with a spanner is ok but you never apply the full original torque.
Yes; if you start to talk about bad engine shops, that’s a whole new can of worms. It’s not aircraft maintenance though.
Peter wrote:
Yes; if you start to talk about bad engine shops, that’s a whole new can of worms. It’s not aircraft maintenance though.
I don’t agree on that, because this is exactly where statistics get the data from (and which is the topic debated widely). If it is bad maintenance, it may be from a bad engine shop :-)
I’ve heard from a lot of engine quits during my flying career, but luckily I didn’t have a single one myself. I go with the “how it is sounding group”. If it sounds weird, I won’t go and check what’s up. And if engine sound should alter during flight I’m very alert about that – but so far I never had any issue. It’s funny, for example, how you note whenever anybody moves in the cabin. I still need some time to relax after an unexpected change of CoG, because this feels like a change of power of the engine. AoA changes slightly.
But honestly, I think that it must be some sort of luck that I did not have to go through this so far. For example, on a day when I was flying a colleague landed in a field with carburetor icing (perfect landing, no damage). I really wasn’t aware that this could have been an issue that day, and I did not encounter any problem although flying a similar engine type and similar altitudes (but not at the same time). You need a lot of situational awareness to anticipate possible engine issues (like, in particular, icing, but also fuel states and so on).
Peter wrote:
Yes; if you start to talk about bad engine shops, that’s a whole new can of worms. It’s not aircraft maintenance though.
This was not an engine shop. It was regular maintenance. Unfortunately, no accident investigation was made (probably because of the successful emergency landing) so it don’t have any details readily available. (This happened in 2017.)
Peter wrote:
Not using alt air in -15C. A DA42 gets a dual engine stoppage too in those conditions, despite having a very different engine.
This simply isn’t true – claiming “gets” would mean that it happens always, often or at least sometimes. If it happened once to someone under some conditions, it can’t be described as “gets”. I regularly fly DA42 in temperature range below -10C (down to -30C) with opening alt air only in visible moist conditions and I have never noticed any engine problem.
It is in IMC. Probably takes quite some time to happen; took some tens of mins on the TB20.
It was regular maintenance
How is that possible? No externally accessible items which could cause a conrod breakage.
