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New Kid Flying Question

GrinchF16

Well Known Member
Sometimes you just have to risk looking like a chuckle-head…..

30+ years flying but almost exclusively jets. New to the prop world. Here’s the situation:

RV7A, 180hp, carbureted Lycoming, one mag, one electronic ignition

AWOS - Clear skies, 50+ miles vis, calm winds, no visible moisture (for 100 miles), temp/dew pt (78/50)

5’500’, leaned just ROP (archaic panel so “just ROP” is as detailed as I can get), 2400 RPM, 148 KTAS, CHT’s high as 430 in the climb (I’m working on that) but now all under 400, oil temp 195, oil pressure 80, life is good. Airplane shudders, engine instruments remain same, I turn to nearest divert, carb heat on, switch fuel tanks, A/C continues with odd vibration. I figure if I’m going to lose the motor I’ll do it on my terms, add power and climb for range. As I get within glide range of my divert field, A/C smooths out. 3-4 minutes total elapsed time. At this point I can turn toward home and stay within glide range of divert airport until within glide range of home field. Check mag/electronic ignition, nothing unusual. Stay within gliding parameters and land uneventfully.

Post flight inspection I find blood/snarge on the prop.

As I said, new to the prop world. Is it possible I whacked a bird and the remains effected the balance of the prop until they were spun off, kinda like I think liberating ice might work? Not a rhetorical question, I know there are some brilliant aero types here as well as a wealth of experience.

Standing by for spears but hoping for some good input.

Thanks
 
Last edited:
Great detail! Greater story!!

Would think bird remnants would clear faster, but maybe it was just a particularly sticky mess.
 
Inspect or have the prop inspected. You didn't say (or I didn't notice) what type of prop. Your scenario is possible but you also want to be sure the tracking, etc. was not affected. That it smoothed back out lends credence to your idea, but still... Lycoming says any prop strike requires at least pulling the rear case and inspecting. It doesn't say the prop has to strike the ground. As I recall, even touching grass can potentially create enough force to damage a crank.

By the way, impressive incident management and decision-making.
 
It would be incredibly bad luck but you may want to inspect the induction and air cleaner for remains, feathers, etc.. Stranger things have happened.
 
Sticky valve?

If the goo on the prop turns out to have been a red herring (pun intended), I would next consider the possibility of a sticking exhaust valve. These can come and go and produce very rough operation intermittently. Doesn’t sound like the classic “morning sickness” scenario, but worth considering.

Peter
 
Hmm

Patrick, "impressive" would be a pretty strong word ;)

Peter, what is this classic morning sickness you speak of?
 
Fuel flow issue perhaps?

I am no engine expert, but I agree with looking into a possible fuel/mixture flow disruption or combustion disruption as suggested. If it was carb ice it's long gone, but you should have seen reduced RPMs to go along with the roughness. Another thought is fuel contamination. Did you find any water when you sumped the tanks and gascolator if you have one? Is there any debris in the carb or gascolator?

It would be incredibly bad luck but you may want to inspect the induction and air cleaner for remains, feathers, etc.. Stranger things have happened.
 
Peter, what is this classic morning sickness you speak of?
Lycoming engines use sodium filled valve stems to transfer heat the the valve guides. If this heat cokes oil in the guide, the clearance goes to zero and the valve can stick open, especially when cold. Thus a stuck valve leads to morning sickness - a rough running engine on the first cold start. Might also bend a pushrod. There is a Lycoming SB to check valve to guide clearance every 500 hours, iirc. This is called ‘the wobble test’ because that’s what you measure.
 
Hi Brian, do you have an engine monitor? Even some of the older ones store/log data. That might give some hints. You can upload your data to savvyaviation.com and they draw pretty graphs, and if you pay them, they will look at the results and provide an expert analysis. I've done it a few times and it gave me some piece of mind. For this incident, looking at fuel flow and EGT would tell you a lot. Good luck with your investigation.
 
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