Aircraft without a loss of oil pressure procedure
 

A while ago I flew for a company that flew small turboprops and I suddenly realised one day that nowhere in the QRH was there a procedure for dealing with loss of engine oil.
I've never seen or heard anything like that on any other aeroplane, has anyone else?

I'm familiar with your level of experience 18-Wheeler, but would it not be an obvious procedure, or no? Or am I missing something?

believe it or not, the 744 had no procedure either, There we were, getting ready to coast out over Gander, and the low oil warning came up. Surely there must be a checklist!!??
Nope, we let it get down to 4 Qts and said, "I ain't trashin a 10 million dollar engine" and we shut it down.
I thought that kinda wierd also.

Hmm, I agree with Brian, its pretty obvious - yet there should be a procedure telling you to shut it down like there is usually a procedure for all other more or less obvious problems you could get into...

Some aircraft don't have a procedure for low oil quantity, because there's no indication of low oil quantity. There may be indications for oil pressure and temperature, and in the case of turboprops, torque (also actually an indication of oil pressure, directly or indirectly). Often there's no indication of oil quantity, however, which somewhat negates any inclusion of a procedure for oil loss or decreasing supply.

In the event of an oil loss, sometimes there is an increase in oil temperature (not always), and one may have an indication of loss of oil pressure (not always). If either of those two situations occur, then one addresses the signs and symptoms, rather than the root cause of the problem.

Several years ago I experienced an engine failure in a single engine airplane using a TPE-331-10 turboprop engine. The failure occurred at a difficult and less than ideal time, with no forewarning until I lost torque. The engine parameters were good; oil pressure didn't give an indication of a problem up until the power loss, and oil temperature didn't climb. I didn't have any change in EGT or other operating parameters. The engine ran like a top, but without torque. Given that the failure occurred inside a narrow canyon that was very actively on fire, and it occurred at 150' AGL, I didn't have time or inclination to look up a checklist; the obvious problem at the time was loss of torque.

I put the airplane on a mountainside. Subsequent investigation showed that very little oil remained in the engine, and the cause of loss was a failed turbine bearing seal. Discussions with Honeywell revealed that the engine has been shown to run up to a half-hour with no oil. Indeed, the engine ran just fine...but without any oil to actuate the propeller, I had no torque available, and therefore no thrust. Given that the engine ran normally, with normal response to power lever movement (EGT and RPM responded proportionately to power lever movement as expected, except little or no torque), the use of a loss-of-oil checklist would have been irrelevant. Loss of torque, perhaps, but there wasn't an oil quantity indication available, nor was there any reason to suspect oil loss given no increase in oil temperature or decrease in oil pressure indications, and no other annunciations.

The airplane I currently fly, not a turboprop, has procedures for loss of oil, low oil quantity indication, and of course, low oil pressure. I think that to suggest that what one should do would be obvious, however, overlooks the differences in design and procedure that exist between different manufacturers. In the case of this airplane, a loss of oil isn't cause for shutdown until the quantity reaches .5 gallons. In that event, the engine may be restarted for the approach and landing. In other airplanes, I wouldn't consider restarting the engine, or waiting until such a low oil quantity, before shutting down.

On some turboprop engines, such as the PT6, the oil pressure is sampled at the same location as the torque indication. On some engines, oil is pumped from the same drive as fuel, and so forth. Loss of one indication, or a poor indication from one source, doesn't necessarily indicate a loss of pressure; so long as one has the sister indication (torque, on a PT6, for example), one still has the oil pressure, even though cockpit direct indications (oil pressure, for example) seem to indicate otherwise. What works for one system or aircraft may not apply in another.

Hi Guppy.

For my love of turboprops, my inexperienced mind is curious to know a bit more about this. I recall the torque-meter on the PT6 works on oil pressure exercised by an internal mechanism I don't remember very well at the time. So what you're saying is that losing oil pressure would cause a low torque indication? Or is there something else about this?

Thanks in advance :)

One night taking off from Aspen (KASE) we lost oil pressure in the left engine, as we were still below 100 Kts IAS we aborted. The aircraft was a Sabre 65 with the TFE 731 engines.

The engine was still running when we turned off the runway and I told the PF to shut it down. When we parked I went out and looked at the left engine and it was covered in oil* along with the left side of the aft fuselage behind the engine. I tried to move the fan and it was firmly locked.

When asked what we would have done if we had lost oil pressure after V-1 i replied that we would have done nothing and continued the takeoff. I also said that I would have not shut the engine down until we were back on the ground.

The reason for this reply was I had been told that a Sabre 65 had lost oil pressure inbound to LAX from PHNL (Hawaii) about 800 mile out over the Pacific. The crew did not shut the engine down until they landed. In fact I had met the crew of this 65 during recurrency training a year earlier.

So as far as I am concerned, if you still need the engine and it is still running after the loss of oil pressure, use it. Most likely the engine is mostly shot anyway.

However, in the case of turbo-prop engines, as with Guppy's story, I've never heard of one running and producing usable power after the loss of oil pressure. Such as I experienced in a MU-2, the engine immediately NTS (kind of like auto-feather) when the oil pressure was lost.


* When we opened the cowling, a bunch of parts fell out on to the ramp. It took six months before the engine was returned to us. Thank God for MSP Gold.

On the PT6 there's a torque bar which operates off oil pressure. The torque indication is actually an oil pressure indication. Separate pickups deliver oil pressure to cockpit indications, from the torque indications, and the way in which they're interpreted in the cockpit is different, both by the pilot and by the instruments themselves, but they come from the same location in the engine and use the same oil under the same pressure.

Torque, while a measure of the torsion on the driveshaft to the propeller, is actually an indication in that engine of oil pressure which represents the torsion on the driveshaft. The oil pressure variance is supposed to be proportional to the torque, and therefore usable as an indication of torque as converted by the torque gauge (first converted to an electrical signal, then to an instrument indication).

More importantly than the actual indication, however, is the result of a loss of oil pressure to the propeller assembly. Without a means of governing the propeller (given a loss of oil quantity), one loses torque. Just as I experienced in a different type of engine, while the engine ran like a top, no torque was available from the propeller. The mechanism by which this happens, and by which the engine is driven and thus operates between the gas generator and the propeller are entirely different when considering the PT6 and the TPE-331, but the results to the pilot can be the same: no or low thrust.

The point I was making is that while the indication is certainly of interest, one can get a number of different indications. With loss of oil, the most telling may be that no matter how well the engine is running (and indicated to be running), the actual loss of power may be the most glaring indication of what must be done (or can't be done). Even in the absence of other indications of trouble (no oil quantity indication, installed or otherwise, for example), one has other more basic, obvious manifestations of the problem.

It's also why I say that what to do about low oil quantity isn't necessarily an obvious thing. What one does about it in one airplane may be entirely different than in another.

In the case of the single engine airplane oil loss and forced landing that I previously described, the failure occurred during a steep descent in a burning canyon. I didn't have any indication of the problem until I reached the bottom of the canyon and pushed the power lever up. The engine instrumentation responded normally, all save for torque. I had very low torque (about 15%, where I expected about 85% at the time, given the power setting). I jettisoned the load, and the airplane pitched up. As it did, the remaining oil flowed back to the pickup, and I got a brief increase in torque; for about three seconds I had 50% torque and actually considered being able to limp 10 miles to a nearby airfield. As soon as that oil was gone, the torque indication dropped to zero, which is certainly how it felt, as well.

Interestingly, the propeller didn't feather, and the engine continued to operate until the airplane came to rest on the hillside, and I fuel chopped the motor. Had it been a PT6, I think the propeller would have feathered. Given the direct drive of the TPE-331, the propeller rotated, but didn't feather; it didn't provide significant drag, either, but waffled in a fairly useless state far out in front of me.

What you see with oil loss may vary from engine to engine, depending on exactly what has happened, as well as the type of engine in use, and the circumstance in which the failure occurs.

Noticing oil loss is most cases a big deal on a turbojet/fan, if needed run it w/o question.

If not needed can shut down and save some oil for a restart on approach if the leak is slow enough, or would advise to shut down on a loss of oil pressure to prevent further damage.

Friend of mine was on a 741 or 2 with JT9's, noticed a loss of quantity and took the above mentioned option A and landed without event or a need to divert.. later found out the technitions provided to them in I think Gambia serviced the engine with skydrol. Just lucky it was not all 4 up over the Atlantic.

It's a pretty big deal in a single engine airplane, too.

Given that the engine ran normally, with normal response to power lever movement (EGT and RPM responded proportionately to power lever movement as expected, except little or no torque)

having logged several hours on a c441 in the past- can you tell me what you expect from a tpe331 to respond proportionally in rpm when you move the power lever inflight ?

If one is familiar with a particular airplane, then one generally knows how much power one should expect from the powerplant, with a given amount of travel by the power or thrust lever or throttle. That is, one if one knows that travel three quarters of the way forward to the mechanical stops normally produces takeoff thrust, one knows that given slight variances in day to day conditions, that's how far one can expect to move the levers on any given day to produce approximately that amount of thrust.

In the case of the TPE-331 failure previously described, the EGT response and engine parameters were exactly proportional to what one would expect if the engine were operating normally. Setting the power lever in that case to the position which should have corresponded to takeoff or go around power, the engine indications moved exactly as one would expect in every respect, save for torque. In that particular airplane, because all operations were very low to the ground and it was very much a heads-up operation, the most prominent engine instrument was EGT, a large gauge right smack in the middle of the panel in the single seat, single engine airplane, where it couldn't be missed. Power settings were easiest by EGT, with a follow up to torque to confirm.

When I initially moved the power up to go around in the smoky and burning canyon, the EGT corresponded exactly to what I'd have expected; it was proportional to power lever movement. All other engine parameters were in proportion; nothing stood out. No annunciations, no high temperatures, no excessive oil temps, no low oil warnings or indications; just a very obvious lack of torque. The engine responded, it sounded normal, the vibration was normal, but the airplane was clearly losing energy, and a brief heads-down look in the cockpit confirmed that while everything else looked good, torque did not.

well... you wrote much without saying anything ... on the tpe331 you look primary ( especially at low altitude) into the torque- the egt is just the limiting factor, not a setting device at low altitudes.

so again-

what you expect from a tpe331 to respond proportionally in rpm when you move the power lever forward inflight ?

what TQ , EGT an fuel flow readings ????

the tpe331-10 was exactly the engine mounted on the conquest II i have flown.

when you did not looked at the instrument in this emergency conditons- what happened? you pushed the lever forward an what?

what ac type?

I've got an old B744 QRH here and it gives a procedure for loss of engine oil pressure, (at or below the red line shut engine down), and rising oil temperature. In this copy they are at page 07.09 but that has probably changed by now?

And then there are some engines that will 'hide' oil quantity...so much so that one might presume all the oil has disappeared (from 20 to 3 quarts indication), however upon landing, the quantity immediately once again shows normally.
RB.211-22B's are 'famous' for this, especially after long storage.

In thse cases, if oil pressure and temperature are otherwise normal...press on regardless.

I noticed that even the CFM56-7B does this, even if the mechs topped up the engines pre-flight the indication might go down to 12 or 11 which normally means its time for a refill. Back on terra firma the oil indication is normal again...

Oil "gulp" is normal, full oil quantiy by design is usually only correct 5-30 minutes after shutdown for most types. Not just with engines running at different phases of operation but can be observed during rapid throttle advancement. It only means a re-distribution of oil to where it is needed. Just about all jet engines do it to a different degree.

It would appear that you're not pleased until you hear whatever it is that you want to hear. Why don't you go ahead and tell me the words that you'd like to hear and perhaps you can get me to say them. Will that make your day?

EGT is only a limiting factor? Not on the airplane I was flying, where most of the working operation takes place between 5' and 50' above the surface, and nearly all of it in very mountainous terrain, and nearly all of that working vertically in the terrain. Limiting, yes, but the operation was temp limited, and it's a very important limit. So no, not "only" a limiting factor, but a very critical limiting factor, and one that was often reached, or risked being reached, before torque limits came into play.

As you're aware, turbopropeller airplanes can be torque-limited at low elevations, and temperature limited at higher elevations. The base elevation of the departure field was about five thousand feet. On a hot summer day, the density altitude for departure was about 8,500'. The fire I was fighting was on a mountainside at a higher density altitude, and the primary power setting instrument, as designed by modifier of the aircraft when it was converted to a turbine airplane, was the EGT. The EGT was a large instrument, set to the pilot couldn't miss it. Get the power in there, then fine tune with torque if one likes. Keeping within limits was of greater interest than setting fine power. It wasn't a conquest, and it wasn't middle-of-the-box kind of flying. One set power using the power lever to a known position while looking outside the airplane to keep away from rocks and trees, and glanced briefly at EGT to ensure one wasn't hurting anything, and occasionally at torque. Power was up and down so much throughout the flight, constantly changing, that trying to watch torque would be a futile exercise, to say nothing of it being a small instrument on a side panel which held little prominence other than confirmation that things were going according to plan. On the day in question, a glance at torque confirmed that indeed things were not.

I don't recall specific numbers for the torque or other settings, off-hand. That was several years ago, and I've operated 10 other types of aircraft in the intervening time. As I recall, I was able to pull about 85% torque when approaching the takeoff temp limits in that airplane, with the speed lever in high. The installation was temp limited in those operating conditions, not torque limited. In that installation, I believe we used a percentage or torque indication, as opposed to many airplanes which used a calibration in foot-pounds, or horsepower, psi, or other methods of indication.

If you don't like the installation, you should speak to the STC holders who modified the aircraft. I didn't design it or make the installation; I only flew it.

I have no idea what you're trying to say, or ask, but you appear to have it wrong, whatever it might be. I did look at the engine instrumentation; that's really the point. Low oil quantity didn't produce discernable changes in engine operation, and according to Garrett/Honeywell, the manufacturer, one shouldn't necessarily expect it to do so, either.

The aircraft type was a PZL M-18T-331-10.

SNS3Guppy
 

Thank you very much for the enlightening. Didn't know about that useful tip when the :mad: hits the fan

SNS3Guppy

it is not an offend against you, but indeed some of you comments sound very strange to me - especially this:

EGT and RPM responded proportionately to power lever movement as expected, except little or no torque

doubting if you have ever operated an airframe with a tpe331 powerplant.

on the single shaft direct drive tpe331 the rpm change is exactly ZERO when you push the power lever forward . on the split shaft pt6 the prop rpm would stay the same but the Ng would indeed change.

the other point is that at least installed on the C441 the engines were always torque and not EGT limited at take off and lower altitudes.

but here we may have the difference that on a C441 the engines were rated at just 636HP each side and especially the 331-10 laughed about putting 636 horses to the gearbox.

on the mighty dromedar the engine has to push mush more horses and here indeed it may temp out earlier, i do not know this installation.

ok, you surely did not just wrote this story but it really happened to you so i am wondering what happened and why.

one guess: the 331-10 is equipped with a fuel computer which limits both TQ and EGT. you cannot overshoot the max values.

maybe one of the issue in fire fighting missions was that you flew very low in an area of very hot air from the fire below you and the fuel computer lowered power output to nearly zero to prevent an sudden EGT overshoot?

is it confirmed that an oil loss was the only reason for running the engine normally but producing no thrust ( torque) ?