Purposely cutting an engine in flight???

[UnAnswerd]

Here's the scenario:

You're on a X-country flight with a single-engine aircraft, and you suddenly get the feeling that you're having an engine problem. For the moment, the engine sounds different, it feels like it has less power, you might be able to determine that it is knocking. You look at the gauges and discover that you have zero indicated oil pressure. Oil temperature is also in the red. Based on the gauges, and coupled with the bad engine sounds, you have a gut feeling that the engine is about to take a dive. Here's the question:

Would it perhaps be better to purposely shut the engine off in flight??? Maybe at this point you haven't destroyed the rod-bearings yet. Maybe you can eliminate thousands of dollars worth of repairs by simply shutting the engine off before it destroys itself. The mentality here is that even if you don't shut it off, it's likely going to die anyway, only with much greater damage to the engine. Would it be wise to shut the engine off, or should a pilot always wait untill that engine is definitely gone, and never ever shut an engine off in flight???

 

[Gulfstream 200]

shut it off?...um no.

You did say single engine aircraft right?

Worry more about your dead burnt carcass in that mangled tin $hitcan than about a thousand dollars worth of rod bearings...

.

that last minute sputter might just get you over the last row of trees before that open field.

 

[DX Rick]

Screw that engine, use its last leg to get you on the ground in one piece, then shut it down.

 

[Yellow Snow]

If you look down (for the first time) and see guages in the red and zero oil pressure you need to work on your scan. You should be looking at the engine guages regularly looking for trends to give you an idea of the health of the engine.

Its hard to say in an actual emergency what you would do until you are there. In a twin with a full feather its a little easier to decide what to do because you need oil pressure and rpms to feather the prop so you have to get to it before its too late. Most light twins have so little single engine climb that a windmilling prop could be what kills you.

In a single I would think I'd be reluctant to shut down any engine that is still making power until I was certain I had a suitable place to land.

 

[UnAnswerd]

I see what you guys are saying. Justed wanted to get some input on this subject. Thank you.

 

[mattpilot]

Actually... i'd shut it down before it quit.

If the engine is sputtering/knocking whatever..... and oil pressure is zero AND oil temp is rising/high, your engine will probably die within the next minute.

Assuming a field/road/whatever is within gliding distance, i'd secure the engine. No need to use extra power to 'get over the fence'. Either you've established a proper descent to your landing field or you haven't.

Now assuming i'm close to an airport, then yes, i'd use that available power to try to make it back to the field - but those situations are unlikely.


The reason i say i would shut it down is because i don't need more stuff going wrong. A overheated engine could start blowing off engine parts, cause fires, spray oil all over your windshield and do other wierd shat.

 

[Huggyu2]

If I can glide to an airfield, I'd give serious consideration to shutting it down. If you're not real confident in your ability to glide it into an airport and land, then you need to practice that scenario more.

 

[FN FAL]

Actually... i'd shut it down before it quit.

If the engine is sputtering/knocking whatever..... and oil pressure is zero AND oil temp is rising/high, your engine will probably die within the next minute.

Assuming a field/road/whatever is within gliding distance, i'd secure the engine. No need to use extra power to 'get over the fence'. Either you've established a proper descent to your landing field or you haven't.

Now assuming i'm close to an airport, then yes, i'd use that available power to try to make it back to the field - but those situations are unlikely.


The reason i say i would shut it down is because i don't need more stuff going wrong. A overheated engine could start blowing off engine parts, cause fires, spray oil all over your windshield and do other wierd shat.

Yea, toss something out the cowling and you could be trying to find that golf course looking out the side window...good point.

I landed a PT-6 powered Caravan at mins on an ILS and taxied up to the hanger...the rampies had a funny look on their faces. I got out and saw what they saw...the bottom half of the Caravan looked like it had been dipped in oil...streaming all the way back from the cowling and covering everyting.

Out of 14 quarts, I had 4 left...after a two hour flight. A couple of turns around a holding fix and I would have finally seen an "oil press" low light.

The leak was caused by an improperly replaced or defective "o" ring in the return line of the scavenge system. No oil pressure reading to indicate the loss, no CWS warning and oil temp was in the green.

Yea, I know piston planes and turbine planes use oil in a different way to get things done, but you'll only know oil pressure loss if it happens where the guage will see it...and the corresponding temp rise? When would that happen? Plane mechs?

 

[TrafficInSight]

If it's shaking around a lot shut it down. It can tear itself right off the mounts then you will have a real problem.

 

[Thedude]

If it's shaking around a lot shut it down. It can tear itself right off the mounts then you will have a real problem.

I really think it would sieze beofre it got to that point.

 

[A Squared]

Its hard to say in an actual emergency what you would do until you are there. In a twin with a full feather its a little easier to decide what to do because you need oil pressure and rpms to feather the prop so you have to get to it before its too late.

Actually in most light twins, the prop is feathered by springs and/or nitrogen pressure. The oil pressure is typically *preventing* it from feathering.

 

[TurboS7]

Back when I was trying to be best flight instructor on the planet I would shut the engine down and stop the prop at 3000' AGL and make the student dead stick the airplane into a little 3000' grass strip. I was crazy but it was fun.

 

[USMCmech]

Never shut down a running engine in a single engine aircraft.

Trying to save the engine by cutting the fuel or ignition, will not stop the prop from turning. Since the engine is still turning, the bearings are still being worn. Now you have a destroyed engine, and you have to deal with gliding to a safe landing site.

you pay the insurance company all that money for a reason.

 

[EagleRJ]

I've had numerous hangar discussions about the effects of a loss of oil pressure, and what would happen if the engine continued to run. I think the general consensus is that the oil temperature wouldn't necessarily rise, since oil would stop flowing past the sensor and the additional heat wouldn't reach it.
There's no question that running the engine after a loss of oil pressure will eventually result in loss of power, but it would probably be gradual. As the bearings and rings begin to gall and melt, the friction will rise so high that the engine will grind to a stop. Some think the engine would sieze instantly, and there would be a danger of it twisting itself right off the Lord mounts. That's a possibility, but I don't think it would be turning fast enough for that to happen.

Yea, I know piston planes and turbine planes use oil in a different way to get things done, but you'll only know oil pressure loss if it happens where the guage will see it...and the corresponding temp rise? When would that happen? Plane mechs?

Not a mech, but ISIAHIELN....
There's a lot of inertia in a rotating assembly that's turning 60,000 RPM. The only difference is we're talking roller bearings, not just oil-film bearings. Who knows how the engine would react after loss of oil flow. I just know I wouldn't want to be anywhere near it if those bearings welded the rotating assembly to the case!

 

[Flyin Tony]

I had a guy turn the fuel off on me in a 172 in flight. Lots of time to go through everything. But im not going to be doing that to any of my students.

 

[FracCapt]

Would it perhaps be better to purposely shut the engine off in flight???

No. Don't shut the engine down in flight. Use the engine until it's dead....or it may be YOUR death instead of the engines. If you feel you must shut it down, do it once you're OVER the runway, about to start the flare, with lots of runway left.

The only time I shut an engine down in flight in a single(or would ever consider doing it) was after loss of oil pressure in a Porter. I saw a drop in pressure, and the prop started to drive itself to feather. That engine was doing me no good swinging a prop that was feathered(actually it was creating more drag), so I shut it down. It helped that I was at 12,000' right over the airport I took off from.

 

[UnAnswerd]

I saw a drop in pressure, and the prop started to drive itself to feather. That engine was doing me no good swinging a prop that was feathered(actually it was creating more drag), so I shut it down.

Sorry. I'm unfamiliar with the "feather" term. I'm interetsed in knowing what it is...

 

[FracCapt]

Sorry. I'm unfamiliar with the "feather" term. I'm interetsed in knowing what it is...

The Porter is a turboprop. It has a Pratt PT-6 engine. Also known as a Free Air Turbine. The prop will go to feather(straight forward and back, rather than left to right) when you lose oil pressure. It's the same thing that happens on multi engine airplanes when you "feather" the prop. The prop essentially aligns itself with the relative wind to greatly reduce drag. When a prop is feathered, it produces NO thrust. If it's feathered and spinning(a feathered prop on a shut down engine will stand still, creating extremely little drag), it's creating more drag than if it's feathered and sitting still.

Can anybody else better explain to him what it means to feather a prop? I'm kind of at a loss here....haven't heard this question in years!

 

[UnAnswerd]

The prop will go to feather(straight forward and back, rather than left to right) when you lose oil pressure.

Okay, so it's an issue with constant-speed/variable pitch propellers? You're saying when you lose oil pressure the prop governor is effected, and the blades simply align with the relative wind?

Also, what does "windmilling" mean? I guess it means the prop is just spinning freely on it's own, but can it really happen in reciprocating engines??? I find it hard to believe that relative wind can overcome engine compression and spin freely.....

 

[FracCapt]

Okay, so it's an issue with constant-speed/variable pitch propellers? You're saying when you lose oil pressure the prop governor is effected, and the blades simply align with the relative wind?

Different types of engine/prop combos will do different things. Turbine engines generally go to feather with a loss of oil pressure, but single engine pistons with constant speed(controllable pitch, in other words) props normally will go to low pitch/high RPM with oil pressure loss. In other words, they will go to the same setting used for takeoff, developing the most power possible out of the engine.

Also, what does "windmilling" mean? I guess it means the prop is just spinning freely on it's own, but can it really happen in reciprocating engines??? I find it hard to believe that relative wind can overcome engine compression and spin freely.....

You got it. It just means that the wind is driving the prop, rather than the prop being spun by the engine. Yes, piston engines do windmill. If the engine fails, the prop will likely continue to turn unless you slow down to a VERY slow speed. On the flip side, if the prop is stopped, it takes a tremendous amount of speed to overcome the compression of the engine and allow it to windmill.

 

[Oakum_Boy]

That happened to me on upwind in the pattern. That sucka really lost it about midfield and sprayed oil all over the windscreen. Left that sucka wide open. It wouldn't produce but idle power, but we landed safely not even thinking about the motor. Barely taxied to the ramp with full throttle. Never did find out what the bill was....

 

[mattpilot]

Barely taxied to the ramp with full throttle. Never did find out what the bill was....

So..... why would you do that?


After landing pull the mixture. Get a tug.

 

[Oakum_Boy]

So..... why would you do that?


After landing pull the mixture. Get a tug.

It was about 50 feet. Not goin' through the hassle.

 

[DaveJ]

Inspired by Bob Hoover

In my youth, I used to take a J3 cub up to about 5000 ft over the airport and kill the engine. I'd also slow it down to stop the prop from windmilling (it gretly reduces drag if it's not windmilling), and then dead stick the J3 to a landing. I got good enough to keep enough energy to get it all the way to it's tie down spot before stopping. Of course, I'm also a glider pilot and the J3 just turned into a crappy glider without the engine running.

 

[Mysteryofflight]

Actually in most light twins, the prop is feathered by springs and/or nitrogen pressure. The oil pressure is typically *preventing* it from feathering.

Not sure which twins you are referring to, however in my experience, most light twins require at least 1000 rpm in order to feather. This results in just enough oil pressure to keep the manual stop pins from coming out and stopping the prop from feathering. The nitrogen charged cylinders are to be used to take the prop out of feather, same thing with an accumulator, in the case that you get the engine restarted.

 

[funky]

shut it off?...um no.

You did say single engine aircraft right?

Worry more about your dead burnt carcass in that mangled tin $hitcan than about a thousand dollars worth of rod bearings...

.

that last minute sputter might just get you over the last row of trees before that open field.

i'm laughing my ass off!! good one....

 

[A Squared]

Not sure which twins you are referring to,

Most of them built in the last half a century or so with reciprocating engines. A few, like the Beech 18 have Hamilton Standard Hydromatics which feather on a different system.

however in my experience, most light twins require at least 1000 rpm in order to feather. This results in just enough oil pressure to keep the manual stop pins from coming out and stopping the prop from feathering.

No this is not true, the stop pins are actuated by centrifugal force, not oil pressure, they are merely there to stop the prop from feathering when you shut down on the ground at idle.

The nitrogen charged cylinders are to be used to take the prop out of feather, same thing with an accumulator, in the case that you get the engine restarted.

No, you are confusing this whith the unfeathering accumulator, which is a completely different thing. Yes the unfeathering accumulator is, like it's name suggests, for unfeathering the prop, generally on training aircraft where you can expect to have a fair amount of feathering and unfeathering on a regular basis. What I was referring to when I mentioned compressed nitrogen is this: Some props (Hartzells, but not all Hartzells) have a charge of compressed nitrogen in the prop dome. This compressed nitrogen acts against a piston and together with a spring, drives the blades into feather.

You ever seen a prop on a light twin with the spinner off and noticed a thing which looks like a tire valve sticking out? That's for charging the dome with compressed nitrogen

 

[TrafficInSight]

I really think it would sieze beofre it got to that point.

It has happened.