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What Would You Do ? (2)

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What Would You Do ? (2)

Old 3rd Jul 2020, 04:15
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What Would You Do ? (2)

I was on an aerobatic training trip in a C 150 Aerobat. The runway in use meant basically a straight line after take off to the aerobatic box about 12 miles from the airport.

Unfortunately this airplane had those crappy Cessna oil temp and oil pressure gauges with no numbers just a green arc and redlines. The only help to the pilot was the oil pressure gauge had a white line in the green arc which indicated the ideal oil pressure of 80 psi. In previous flights I had noticed that on this airplane the oil pressure needle was always sitting right on the white line every time I looked at it

After takeoff we were climbing through 2000 ft when I did a routine scan of the engine gauges. The oil temp was mid range but the oil pressure was a needle width below the white line but still well in the green. I kept an eye on the oil pressure and about 30 seconds later the needle gave a tiny wiggle and seemed to make an almost imperceptible drop.

What would you do ?

Last edited by Big Pistons Forever; 3rd Jul 2020 at 05:15.
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Old 3rd Jul 2020, 08:08
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I'd immediately level out and reduce power.
I'd create a mental picture of my plan to make an immediate return to the airfield and fly that plan.
I'd think back to my walk around. Did I check?
If I'm sure I did and all was well;
It could be so many things; oil pump going on the blink, oil line blockage, pressure relief valve. Either way the aerobatics will have to wait.
I'd rather beat a hasty retreat from the air and find out exactly on the ground.
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Old 3rd Jul 2020, 08:23
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We are in the initial phase of a flight, so oil is not on full temp and pressure is supposed to be on the high side with the Aerobats engine.

Level out, reduce power, return to base.

Wiggle at the gauges in an Aerobat can be the gauge itself, but more likely a problem building up in the oil circuit. It can be either the sensor part and the oil pressure line from the engine to the cockpit having an issue, or the oil circulation starts to degrade. If the pressure line from the engine to the gauge breaks you have oil dripping in the cockpit (don't ask why I know). The trouble in oil circulation can build up over a long time, with the option of breaking down oil pressure all together suddenly. The risk of something terribly wrong it too high - especially when talking Aerobatics -, so back to the airfield and to the mechanic to check, is my option here.

Last edited by ChickenHouse; 3rd Jul 2020 at 11:05.
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Old 3rd Jul 2020, 09:24
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Climbing out, full power? Oil gets hotter, pressure reduces, I would suggest probably normal. Level out reduce power and see if oil temp reduces or pressure increases.
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Old 3rd Jul 2020, 10:48
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Speaking with brutal honesty as a low hours newbie:

I would tell myself that the wiggle was probably just a twitch in the sender, I would keep climbing on the grounds that I have no idea if easing off will be better or worse for the engine, and temperature is OK, and if something is going to fail it might as well do it while I am ready for it and staring at the dials, so I might as well claim every foot while I can. I would watch T and P's like a hawk and be ready to immediately head for home if I saw something abnormal. I would keep climbing to get as much spare in the bag, but not start any aerobatics until I was sure everything was stable and normal for that a/c.

I am fully aware that may not be what I should do.


(But I would also suggest that leveling off does not make a lot of sense to me. If you have concerns, go home. But by leveling off you guarantee that home will soon be out of gliding range)

Last edited by double_barrel; 3rd Jul 2020 at 11:22.
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Old 4th Jul 2020, 11:29
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First thing I would do is check there are any sizeable landing fields within gliding distance of the aerobatic box, before flying your manoeuvres.
It must be a club aircraft, as no-one would own a C150 who is interested in aerobatics, there are Extras and Pitts available.
Most aircraft instruments have some sticktion, and can move in jerks. Gliders are especially prone to it, as there is no engine vibration.. To get a reading you sometimes need to tap the instrument panel.
.
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Old 4th Jul 2020, 13:09
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It's still in the green - continue - but monitor it (it's only a single indication) - and especially oil temp carefully. A correspondng variation in temp is reason to return.
I very much doubt any school or engineer would intervene on an indication on an old knocker of a 150 that's allegedly changed but still in the green. After all, what can/could they do?

Last edited by meleagertoo; 5th Jul 2020 at 13:10.
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Old 4th Jul 2020, 19:27
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Play safe. Return and check on ground. Anything different in an aircraft I'm familiar with is worth investigating.
If far from home or alternate airfield, return.
A loose starter warning light wire, flapping against earths, caused oil pressure drops on an electric meter with no wiring near that loose wire. But the combined pressure/temperature gauge showed a steady, normal, temp.

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Old 5th Jul 2020, 16:45
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Originally Posted by meleagertoo View Post
It's still in the green - continue - but monitor it (it's only a single indication) - and especially oil temp carefully. A correspondng variation in temp is reason to return.
I very much doubt any school or engineer would intervene on an indication on an old knocker of a 150 that's allegedly changed but still in the green. After all, what can/could they do?
Check oil?
.
.
.
Oil pressure will stay in the green very long until little seconds before the engine will block on missing oil, it is designed that way. Very seldom does oil pressure degrades over time, if it drops you have only a very, very short time to switch the engine off. Especially since we talk Aerobat here, which has aerobatics capability.
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Old 5th Jul 2020, 16:54
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Originally Posted by meleagertoo View Post
It's still in the green - continue - but monitor it (it's only a single indication) - and especially oil temp carefully. A correspondng variation in temp is reason to return.
I very much doubt any school or engineer would intervene on an indication on an old knocker of a 150 that's allegedly changed but still in the green. After all, what can/could they do?
I think that's what I'd do.

Years ago, while building time for my PPL I was doing circuits in a "well used" C-150 at a nearby country (it did service as the local drag strip on Friday and Saturday nights) airfield when I noticed the oil pressure dropping to nearly zero as I throttled back to idle at top of descent. I was already turning base, so keeping my altitude somewhat on the high side and throttle at idle, I completed my landing. As I exited the runway, I shut the engine down and coasted to a stop on the ramp. Surprised at my quick return for a full stop, the proprieter and local CFI, came out of his office and asked what was wrong. After I explained about the disappearing oil pressure, he shrugged his shoulders, saying: "It has always done that". Realizing that I would not get a full refund on my paid for hour's flying time, I foolishly fired up my (un)trusty steed and continued doing circuits for the balance of the hour's time. Of course, I kept my circuits " high and tight". These days, I'm older, not much wiser, but fully aware of my mortality, and I would've left the sorry C-150 in the chocks and have been much more forceful in demanding a refund.

Cheers,
Grog
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Old 5th Jul 2020, 17:11
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Originally Posted by Maoraigh1 View Post
Play safe. Return and check on ground. Anything different in an aircraft I'm familiar with is worth investigating.
If far from home or alternate airfield, return.
A loose starter warning light wire, flapping against earths, caused oil pressure drops on an electric meter with no wiring near that loose wire. But the combined pressure/temperature gauge showed a steady, normal, temp.
That is what I did. As soon as I saw the needle wiggle I told the student to turn around and head back to the airport which was about 4 miles behind us. After the turn the oil pressure needle gave another wiggle and settled still in the green but noticeably lower. At that point I made a mayday call and told the tower we were going to land straight in downwind rather than join the circuit. By the time we were on short final the oil pressure was indicating zero psi so I shut down the engine and we made an uneventful landing keeping up enough speed we were able to coast to a stop off the runway on the taxiway next to the flying school.

After confirming no oil pressure with a shop gauge mounted directly to the engine the oil filter was removed and had a significant amount of metal inside, The engine was sent to an engine shop and it was determined that a tooth on the oil drive gear had broken off. This caused the gear to skip which eventually broke all the other teeth so the engine oil pump was no longer driven. As the engine was near TBO it was decided to just overhaul it rather than do a full tear down inspection and repair.

As a very new instructor I occasionally flew with an elderly gentleman who's family insisted he fly with a safety pilot. He was the poster child for been there done that and was a fount of knowledge. I asked him for pointers and one of them was where he made a point of suddenly covering the engine instrument cluster with a map and asking me where each needle was. My lame "UMM in the green" was met with a sigh. He told exactly what each gauge was reading without looking and noted that by doing that he was more likely to catch the often subtle changes in gauge readings that are the first indication something bad is happening. It was directly because of his advice that I stared monitoring engine gauges in a systematic manner and meant I caught the failing oil pump in time to return to the airport with the engine still running,
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Old 6th Jul 2020, 11:32
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Originally Posted by meleagertoo View Post
It's still in the green - continue - but monitor it (it's only a single indication) - and especially oil temp carefully. A correspondng variation in temp is reason to return.
I very much doubt any school or engineer would intervene on an indication on an old knocker of a 150 that's allegedly changed but still in the green. After all, what can/could they do?
I agree, if I spot it, I'll monitor it. It's still in the green..

If things start swinging back and forth, then I have a problem, until then....no.

Another interresting note, sometimes when flying into another airmass/over water, have you ever noticed that the engine may suddently start sounding different? I'm always listening when flying, and the first couple of times it almost scared the living .... out of me. Now I know, but it still raises my alertness a bit.
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Old 6th Jul 2020, 17:04
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Originally Posted by jmmoric View Post
Another interresting note, sometimes when flying into another airmass/over water, have you ever noticed that the engine may suddently start sounding different? I'm always listening when flying, and the first couple of times it almost scared the living .... out of me. Now I know, but it still raises my alertness a bit.
Although I've done quite a bit of flying around the Bahamas and Eastern Caribbean, I haven't done enough that I'm immune to the above-described phenomenon. Heading off shore, the engine note always seems to change ...

Cheers,
Grog
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Old 16th Jul 2020, 10:28
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Having once had the pleasure of maintaining a group-owned Aerobat, any variation of oil pressure -- or anything else -- would have scared the pants off me. On one occasion (probably more, but I caught this one red-handed) they ran it low on oil because the group member using it that day didn't want to pay for the Shell W80 topup. They finally ran the bearings by over-revving during aerobatics. Another group had a similar problem with regard to purchasing fuel, running the tanks dry on returning the aircraft as if it was a hire car. The result was inevitable, while nearing home the pilot became disorientated over cloud and his body was recovered from the sea a few days later. I don't like groups ...
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Old 18th Jul 2020, 10:24
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Originally Posted by Big Pistons Forever View Post
What would you do ?
I like what you did with this thread, good thought provoking stuff!
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