Unsolicited Advice Number 462

xsbank · Post by **xsbank** » Mon Nov 14, 2005 6:40 pm

Should you be driving along in your piston a/c and everything seems normal, no other unusual indications, and you notice an oil pressure drop but it stops at about half of the normal pressure (e.g: normal pressure 85, drops and maintains 49) this means that something in the engine has failed (bearing, rings etc.), the oil screen is blocked by crud; the oil is bypassing the filter, the crud is circulating with the oil supply and very soon you will see an oil temperature rise and the engine will fail.

desksgo · Post by **desksgo** » Mon Nov 14, 2005 6:49 pm

Or I could just take some good advice...

You must, however feel for those of us that have always flown with the jumpy needles...a good lesson about the ignoring the needles though!

DG

Mitch Cronin · Post by **Mitch Cronin** » Mon Nov 14, 2005 6:50 pm

Yep.
.... so how'd it go?

Mitch Cronin · Post by **Mitch Cronin** » Mon Nov 14, 2005 6:58 pm

In fact.... for a bit of unsolicited advice of my own.... I'd suggest that in just such an event, the driver ought to consider his powerplant as good as toast right away.... reduce power to a nice cool down setting while descending with the purposes of landing now... the engine might help you make a runway, or it might not, so get to the nearest - won't-break-you-and-your-airplane-field right now, and take it. Explaining your choices later to an owner/boss/cop/golf course operator will be a lot better than not getting the opportunity.

or so I reckon....

xsbank · Post by **xsbank** » Mon Nov 14, 2005 7:09 pm

I left the conclusions to you - Mitch is correct. Mine made it back to the ground throttled back, and ended up as scrap. When it cooled, you could not turn the prop at all.

This is particularly true of a Beav, gang (a Junior is where most pilots will likely encounter a radial these days).

Hedley · Post by **Hedley** » Tue Nov 15, 2005 8:02 am

Ever notice how engines (not just piston) make different sounds and vibrations, and give different indications when it's dark or you're flying over water?

marktheone · Post by **marktheone** » Tue Nov 15, 2005 9:55 am

This is a touchy topic but I'll bite. In the transition from piston to turbine, for myself, I was taught not too overreact. That's not to say you shouldn't do anything. A lot of times it is something electrical. Say for example (apples to oranges, I know) you see on a PT6 prop fluctuations but no fuel flow of torque changes. That could be an FCU (fuel control unit) packing it in or it could be the torque transducer. One is really serious one is not as serious.

In a piston engine if you see an oil pressure drop and no change in any other parameters I may be inclined to think that it is something electrical. It's a touchy thing for sure but it is always best to step back for a minute rather than shut down and feather an engine that had a gauge problem and nothing else.

Right Seat Captain · Post by **Right Seat Captain** » Tue Nov 15, 2005 12:53 pm

marktheone wrote: In a piston engine if you see an oil pressure drop and no change in any other parameters I may be inclined to think that it is something electrical.

Generally in piston engines, oil pressure gauges are not electrical. In a Cessna 172, the POH states that the oil pressure gauge is operated by oil pressure from a direct pressure oil line from the engine. The Temperature gauge on the other hand is operated by an electrical resistance type temperature sensor.

So if you notice a decrease in oil pressure, it could be the gauge itself, but not an electrical issue. Or it could be that you're in for a bad day. I'd rather err on the side of safety in a single. Reduce power, keep enough altitude to keep my options open and fly to the nearest landing strip and keep my eyes peeled for somewhere to glide to.

xsbank · Post by **xsbank** » Tue Nov 15, 2005 6:06 pm

"It's a touchy thing for sure but it is always best to step back for a minute rather than shut down and feather an engine that had a gauge problem and nothing else."

Excuse me, I never said anything about shut down and feather. There is some prudent procedures to follow, but you should never s.d.and f. unless its no longer any use to you, and besides, its been a while since I flew a single, but it seems to me that you don't do that with the only one you've got anyway...

We were talking about engine failures a while ago and all I wanted to do was to pass on something that happened to me in the dim sands of time, that might happen to one of you, and to suggest what might be happening - pre-armed is pre-warned? Pre-warned is pre-armed?
One of those.

It actually happened twice, once on an R1820, which was the one that siezed, and once on a 985, when it didn't, cause it was caught early enough and it was overhauled. Except for blowing tanks

the only time a 985 ever cakked on me.