treyizy

I flew the shuttle sim at the shuttle avionics integration lab just before the final shuttle flight when they had extra time in the sim as the astronauts were past their prep phase and the sim was scheduled to be shut down the following month. We did a RTLS abort after loosing the left main engine, flying to 330,000 ft. at Mach 6. Doing a powered pitch over and returning to land at Kennedy Space Center. It was truly amazing! ...though my landing was a little hard and I apparently collapsed the gear

Thanks everyone for the great suggestions. I'll be sharing the lot with my mechanics and get back with the results. I'll be flying today and try several of the descent profile changes to see how it goes.

I'm at about 2500 rpm. I haven't tried recreating it on the ground after a long flight. Good suggestion.

I'll definitely try to listen for the tap of the valve sticking open. Thanks for the suggestion.

It is noticeable, I never miss it, the only reason I say subtle is that my passenger wouldn't have noticed. It is not nearly as bad as a fouled mag test.

I also suspect that at this phase of flight because the power is so low that the propeller may actually be pushing the engine rather than the other way around.

I wish this were an indicator problem. I really do. The first few times it was the feeling of the airplane that caused me to look over at the EGT.

Additionally you'll notice I point to the indicator before you notice the indicator drop as I can feel when it happens and the indicator lags by a sec or so.

I can feel the issue in the plane, there is a noticeable vibration. Additionally you see the manifold pressure increase. I'm certain its not a sensor error.

We considered that as well, though from what I've heard a valve sticking will make for quite a rough ride and this is not noticible to a passenger. Additionally we did the valve wobble test to check the valve tollerances and they were in range. That said it may be some slight sticking that we aren't able to pinpoint. Thanks for the thoughts. T

So my engine has recently developed a very concerning issue that two different mechanics (one a mooney service center) are having a hard time diagnosing. I regularly fly between the Bay Area and Los Angeles. On this flight my engine works perfectly for 2 hours and 14 minutes of a 2 hour and 15 minute flight. The behavoir that is observed is: I can feel a subtle vibration that accompanies my #1 clyinder droping massively. The issue resolves itself in under an minute and seems impossible to recreate on the ground. This always happens in the final decent at low power with the gear down. I had my passenger video my instrument panel for the final 4 minutes of the flight which you can see below. (issue starts at 1:19, continues until 2:15). Ignore the voltage warning light (this is unrelated and I believe it is triggering errantly becuase the left fuel light was illuminated) Configuration in which the issue appears: Long Flight Gear Down Descent greater than 500 fpm (though not above 1000) Manifold pressure < 15" (in the case on the video just under 14") RPM ~ 2500 Altitude between 2500' & 1000' Fuel pressure normal Oil pressure normal Temps in normal range Ram Air closed As the issue occurs the #1 Cylinder EGT drops over 600 degrees I also notice in the video the manifold pressure increases over an inch as the cyclinder drops (unfortunately my passenger didn't keep the manifold pressure in frame much longer to see more coorelation) The cylinder recovers and then this cylce repeats about 4-5 times over the next 45 seconds After this the issue resolves itself During this time I didn't adjust the throttle, mixture or prop. Things that have been investigated: Inspected the Mag and did a 500 hour overhaul Cleaned the injectors and swapped injector nozzles with cylinder 3 Checked and flow tested the spider valve (passed) Checked the induction system and replaced all the gaskets (nothing looked odd) Replaced the spark plugs (even though they looked good) Borescoped the cylinder (nothing looked off) Performed a wobble test on the valve (it passed) The issue has occured about 5 times, each time after performing one of the above listed maintenance procedures. I'm not thrilled about flying with this outstanding issue so I'd welcome any suggestions anyone has about potential causes. We are at a loss and about to replace the entire cylinder. Obviously I'd rather not throw $2500 away if that isn't the problem but noone has come up with a reasonable explanation. One other interesting note, my approach into Oakland is much shallower than my approach into Santa Monica and it seems to happen less frequently on that approach. The engine performs wonderfully during run-up and for the entire rest of the flight. That said I'm concerned about this leading to a total power loss. Being that I'm at a relatively low altitude over a congested area, I'd rather not be looking for a nonexistant safe landing spot short of the field. As you all have seen a whole host of things I thought maybe one of you had experienced or heard of something similar and might provide some ideas. I'm happy to answer any additional questiosn. A bit about me: J model owner for 10 years >1200 hour IFR pilot Thanks for your thoughts, Trey