AcroGimp
EAA 14, IAC 36
- Joined
- May 8, 2012
- Messages
- 212
- Reaction score
- 43
I was leading a 3-ship formation aerobatic flight in the Yak on Saturday, we had been out for about 45 minutes, when I noted a prop surge on the downline of a Quarter-Clover Down figure. We were about 3/4 mile offshore and about 15 miles over the ground away from our home airport.
I reported the surge to my wingmen and called knock-it-off and turned towards the coast. I gave the lead to one of my wingmen so I could focus on flying/troubleshooting and have him navigate us under the Class B and back to our home field. I noted that CHT's were on the low end of the green arc and I know that my engine does not like to be on either end of the green arc and suspected this was my issue.
1/3 of the way back I started to get oil on the windscreen, a light film in the beginning but quickly it went fully opaque, I told Lead I need a straight in and Tower was helpful. I was now getting a little smoke in the cockpit, clearly heated/burning oil.
I made it to short final, gear and flaps down, rolled wings level and set it down, got off the runway and taxied back to hangar and shutdown uneventfully.
Watching the cockpit cam, it was 11.5 minutes from the prop surge to shutdown outside my hangar. The oil on the windscreen appeared 3 minutes after the prop surge - and in 8 minutes approximately 10 of a total of 12 quarts of oil was lost overboard.
The after action report is that while we did most things right I made a few critical errors too - we had an alternate airport available that is a pain to get in and out of (controllers are not helpful) but it would have put me on the ground fully 3 minutes earlier.
Standard practice for formations is the distressed aircraft is lead so that the wingmen can provide support as needed, including nav or comms; had we followed this one or both wingmen would have noticed the oil on the plane and we would have figured out how substantial the leak was - I did not know how bad it was until I pulled of the runway and saw the wings.
I was focused on the low CHT and never really focused on Oil Temp/Px, even after the oil on the windscreen. I believe this is because they were normal, through shutdown as it turns out, but I did not really focus on them.
After I had the smoke/smell in the cockpit and I had the airport in sight I descended from 2,000' towards TPA of 1,600' - although I was still nearly 3 miles out - we don't glide well in the Yaks and I am the most vocal proponent of altitude when in the pattern - I suspect it was because I really wanted to get the plane on the ground but I gave up some of the altitude I had which equates to time/options.
When we tore the hub open we found a 2.5" failure in the apex of the chevron seal, suspect a manufacturing defect - but there was also some fretting/gouging in the dome bore 180 degrees opposite the tear/failure that had lightly chewed into the outer edge of the seal on that side, also roughly 2.5" across - after 6 hours of operation.
M-14P engine oil system nominal pressure is 71-85 psi - if you give the oil a path of least resistance, it is going to take it.
We are going to swap out a spare piston and dome from his project with new seals and see how things behave - will ask vendor to warranty the seal, since the failure looked like it could have been a defect.
Mechanic may try to mic the bore and see if it is out of round.
Not sure what drove that contact or how it happened, could be the seal doubled up when it failed and pushed the piston offcenter on the opposite side, but it was pretty substantial - no wear noticed on the oil delivery tube that the piston rides on so kind of confused. My mechanic is going to swing by our area Russian mechanic and see if he has any thoughts/has seen anything like it.
In hindsight, I did not feel like it was serious enough to consider declaring until the last 2-3 minutes and by that time I was on approach - my wingman who was leading informed tower that I needed to get in expeditiously, fortunately traffic was low for a Saturday and I was able to just drive in.
I have cockpit video but my audio cable disconnected from my headmounted GoPro early in the flight so no comms, I'd be really interested in hearing that.
Again, in hindsight, I really made a couple bad decisions at critical phases - passed up an alternate airport (before it was obvious how critical the situation was), if we had declared I could gotten a clearance through the Bravo and made a straight in on the crosswind runway at our airport, either option (other airport/our crosswind runway) would have had me on the ground 2-3 minutes earlier but again, the critical nature of the situation wasn't obvious until the last 5-7 minutes of the flight and by that time I was over heavily populated unfriendly terrain with only a golf course and a highway as an out.
Basic airmanship was fine, support from the wingman was pretty good although we have a lot of discipline when on ATC frequencies so I had to be pretty directive that I was not up for an overhead and needed a straight in, I also made a call when I started getting oil smoke in the cockpit - in terms of ADM the decision for immediate RTB is the saving grace, the rest is a series of learning opportunities that we will rotate into our training/briefing process.
My survival/the planes survival was really only possible because I called the knock-it-off and RTB on the initial prop surge - had we pressed for even one more sequence the engine would have seized well short of the airport since each sequence takes about 4 minutes.
It's pretty sobering alltogether.
'Gimp
I reported the surge to my wingmen and called knock-it-off and turned towards the coast. I gave the lead to one of my wingmen so I could focus on flying/troubleshooting and have him navigate us under the Class B and back to our home field. I noted that CHT's were on the low end of the green arc and I know that my engine does not like to be on either end of the green arc and suspected this was my issue.
1/3 of the way back I started to get oil on the windscreen, a light film in the beginning but quickly it went fully opaque, I told Lead I need a straight in and Tower was helpful. I was now getting a little smoke in the cockpit, clearly heated/burning oil.
I made it to short final, gear and flaps down, rolled wings level and set it down, got off the runway and taxied back to hangar and shutdown uneventfully.
Watching the cockpit cam, it was 11.5 minutes from the prop surge to shutdown outside my hangar. The oil on the windscreen appeared 3 minutes after the prop surge - and in 8 minutes approximately 10 of a total of 12 quarts of oil was lost overboard.
The after action report is that while we did most things right I made a few critical errors too - we had an alternate airport available that is a pain to get in and out of (controllers are not helpful) but it would have put me on the ground fully 3 minutes earlier.
Standard practice for formations is the distressed aircraft is lead so that the wingmen can provide support as needed, including nav or comms; had we followed this one or both wingmen would have noticed the oil on the plane and we would have figured out how substantial the leak was - I did not know how bad it was until I pulled of the runway and saw the wings.
I was focused on the low CHT and never really focused on Oil Temp/Px, even after the oil on the windscreen. I believe this is because they were normal, through shutdown as it turns out, but I did not really focus on them.
After I had the smoke/smell in the cockpit and I had the airport in sight I descended from 2,000' towards TPA of 1,600' - although I was still nearly 3 miles out - we don't glide well in the Yaks and I am the most vocal proponent of altitude when in the pattern - I suspect it was because I really wanted to get the plane on the ground but I gave up some of the altitude I had which equates to time/options.
When we tore the hub open we found a 2.5" failure in the apex of the chevron seal, suspect a manufacturing defect - but there was also some fretting/gouging in the dome bore 180 degrees opposite the tear/failure that had lightly chewed into the outer edge of the seal on that side, also roughly 2.5" across - after 6 hours of operation.
M-14P engine oil system nominal pressure is 71-85 psi - if you give the oil a path of least resistance, it is going to take it.
We are going to swap out a spare piston and dome from his project with new seals and see how things behave - will ask vendor to warranty the seal, since the failure looked like it could have been a defect.
Mechanic may try to mic the bore and see if it is out of round.
Not sure what drove that contact or how it happened, could be the seal doubled up when it failed and pushed the piston offcenter on the opposite side, but it was pretty substantial - no wear noticed on the oil delivery tube that the piston rides on so kind of confused. My mechanic is going to swing by our area Russian mechanic and see if he has any thoughts/has seen anything like it.
In hindsight, I did not feel like it was serious enough to consider declaring until the last 2-3 minutes and by that time I was on approach - my wingman who was leading informed tower that I needed to get in expeditiously, fortunately traffic was low for a Saturday and I was able to just drive in.
I have cockpit video but my audio cable disconnected from my headmounted GoPro early in the flight so no comms, I'd be really interested in hearing that.
Again, in hindsight, I really made a couple bad decisions at critical phases - passed up an alternate airport (before it was obvious how critical the situation was), if we had declared I could gotten a clearance through the Bravo and made a straight in on the crosswind runway at our airport, either option (other airport/our crosswind runway) would have had me on the ground 2-3 minutes earlier but again, the critical nature of the situation wasn't obvious until the last 5-7 minutes of the flight and by that time I was over heavily populated unfriendly terrain with only a golf course and a highway as an out.
Basic airmanship was fine, support from the wingman was pretty good although we have a lot of discipline when on ATC frequencies so I had to be pretty directive that I was not up for an overhead and needed a straight in, I also made a call when I started getting oil smoke in the cockpit - in terms of ADM the decision for immediate RTB is the saving grace, the rest is a series of learning opportunities that we will rotate into our training/briefing process.
My survival/the planes survival was really only possible because I called the knock-it-off and RTB on the initial prop surge - had we pressed for even one more sequence the engine would have seized well short of the airport since each sequence takes about 4 minutes.
It's pretty sobering alltogether.
'Gimp
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