Purposely cutting an engine in flight???

[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.