manifold pressure guage becomes an altimeter

[sleepingsquirrel]

There I was , cold dense winter air, full power after take off , level off and adjust for 2300 RPM and 23 inches of manifold pressure. Manifold pressure indicates 29 inches and not responding to reduction of throttle.

What would you do?

[bd32322]

I would vary the throttle and see if airspeed changes, so at least i have throttle control and its not stuck in WOT. Just land at an airport and get the gauge fixed. If airspeed does not change, the throttle is stuck in WOT. That will be a bit more troubling when coming in to land. As to why i would let a mechanic determine that I know that when the throttle cable breaks the default position will be WOT.

[sleepingsquirrel]

Yep! That is true. You're makin me feel like a real aviator!

[jetdriven]

I would set the throttle at 3/4 full and then proceed normally, and probably run well ROP because there is now a vacuum leak on one cylinder.  Then fix the broken manifold pressure line.

[bd32322]

I havent thought about exactly how i would land with a WOT

Could just go to a long runway and kill the power half mile out .. Kind of like landing at some class bravo airport where they tell you to keep the speed up.

Or could run an extremely lean mixture so that i am not developing a lot of power as i come in to land - dont care if its running rough a bit on final approach, i can always get it back with the mixture.

[sleepingsquirrel]

I havent thought about exactly how i would land with a WOT

Could just go to a long runway and kill the power half mile out .. Kind of like landing at some class bravo airport where they tell you to keep the speed up.

Or could run an extremely lean mixture so that i am not developing a lot of power as i come in to land - dont care if its running rough a bit on final approach, i can always get it back with the mixture.

There is a thread here with that failure. Believe it or not , I remembered reading the thread and was already planning a broken throttle cable landing ,until I reduced power and watched airspeed respond.

[BigTex]

I would set the throttle at 3/4 full and then proceed normally, and probably run well ROP because there is now a vacuum leak on one cylinder. Then fix the broken manifold pressure line.

This exact thing happened to me a few weeks ago when my manifold gauge came disconnected from my #1 cylinder. As Byron said, I had to keep it at least 3/4 throttle to keep the engine running smoothly. Then pulling back the throttle, expect the engine to run like crap until you can get on the ground.

[SheryLoewen]

Well  there is a leak between the gauge and the cylinder usually a 1/8" copper or aluminum line, now sucking ambient atmospheric pressure.

 Paul

[sleepingsquirrel]

I have rationallized that leaning to rough then enrichen to smooth takes care of the leanest cylinder.

[carusoam]

One of our members with a long body in Canada had a stuck throttle a while back...

That's my memory.

Better to be open throttle, then closed. ...

-a-

[wrbix]

Interesting, I just read about power management with magneto control in Rich Stowell's excellent book Emergency Maneuver Training (chapter 11, p175) where he describes power management by switching on and off the magnetos in the event of loss of throttle control.. Describes a technique of Stepped Descent on final using the mags.

This is a great read BTW

[bd32322]

Interesting, I just read about power management with magneto control in Rich Stowell's excellent book Emergency Maneuver Training (chapter 11, p175) where he describes power management by switching on and off the magnetos in the event of loss of throttle control.. Describes a technique of Stepped Descent on final using the mags. This is a great read BTW

Interesting ... Hadnt thought about that at all

[bumper]

Interesting, I just read about power management with magneto control in Rich Stowell's excellent book Emergency Maneuver Training (chapter 11, p175) where he describes power management by switching on and off the magnetos in the event of loss of throttle control.. Describes a technique of Stepped Descent on final using the mags.

This is a great read BTW

 

I reckon in an "emergency", you do what you need to, but I'd think switching the mags on and off would result in major backfiring in the exhaust, with the risk of damage. How about instead pulling mixture to idle cut-off? The engine will still be windmilling, so is going to start up again as soon as you push mixture back in enough. Should be easy to control descent that way.

[wrbix]

I reckon in an "emergency", you do what you need to, but I'd think switching the mags on and off would result in major backfiring in the exhaust, with the risk of damage. How about instead pulling mixture to idle cut-off? The engine will still be windmilling, so is going to start up again as soon as you push mixture back in enough. Should be easy to control descent that way.

This reference does discuss other means of power control in event of stuck throttle: carb heat on, magnetos, mixture lean,increase prop pitch, electrical switches on (?); his opinion is that cycling mags in landing approach results in better control and that mag on can more readily give a momentary boost of power late in final or if go around needed....he does say to anticipate the backfire and not to let it distract you. As my CFI tells me: at this point the insurance company likely owns the plane anyway, do what you need to do.

A historical side note from Stowell: "Before airplane engines were equipped with throttles and mixtures, power was controlled by turning magnetos off and on". Anyone confirm this?

[Hank]

I found an interesting read called "Learning to Fly" by Claude Grahame-White and Harry Harper. They went through the whole experience of being a student pilot in the era of advanced aircraft, less than a decade after the Wrights. Engines were routinely switched off to land. Look in the Apple Book Store, it was free. "We've come a long way, baby"!!

[1964-M20E]

Yes. It's true. Here is some text about he old Le Rhone rotary as an example.

Jim

The 80 hp Le Rhone was a very dependable engine. It was used on many early World War I aircraft. The Le Rhone design is one of the few rotary engines that have any amount of throttle control. As in all rotary engines, the engine crankshaft is bolted to the airplane and the propeller is bolted to the engine, where the whole combination spins around as one unit.

All rotaries utilize a blip switch, which is generally mounted on the top of the control stick. With it, the pilot can control the engine power by turning the electricity from the magnetos to the spark plugs on and off. The Le Rhone design is one of the few rotaries that have any degree of throttle ability. There are 2 levers in the cockpit to control the engine. One controls a tapered needle valve that regulates how much fuel the engine receives. The other operates a slide valve located in an air box, mounted on the rear of the fixed crankshaft. The slide valve opens and closes, which determines how much air the engine is allowed to take in. When the air and the fuel enter the hollow, fixed crankshaft and are sucked into the engine crankcase. Maximum engine speed is 1200 rpm. With the 2 levers, he can throttle the engine down to a speed around 800 rpm. Below that point, the engine just quits. Since 800 rpm is too fast for taxiing and landing, the blip switch on the control stick is utilized to kill the engine and keep the aircraft slowed down. With the 2 levers to control the fuel and the air, the pilot is the carburetor.

Do not forget the castor oil mixed in the gas for lubrication it also lubricated the pilot as well.  Very interesting and we talk about engine managment.

[sleepingsquirrel]

Do not forget the castor oil mixed in the gas for lubrication it also lubricated the pilot as well.  Very interesting and we talk about engine managment.

A great deal of cheese in a WWI pilot's diet for that reason.

 

Another post on Pilots of America of a partial leak on manifold pressure guage. Worth reading as it caused pilot to set less power than the guage indicated and LOW airspeed. I can see how that could cause confusion and possibly lead to an accident.

http://www.pilotsofamerica.com/forum/showthread.php?t=56247

[N201MKTurbo]

I see a few of you are apprehansive about power off landings. This is a private pilot skill and should be demonstrated at each BFR. I have told countless passengers to reach over to the throttle and pull it back to idle at some random time, so I could truly practice engine failure landings, but after thirty years no one has done it! It is not good practice if you know it is going to happen.

[sleepingsquirrel]

So what happens when your passenger pulls the throttle back and hands it to you? Your Mooney is now traveling near the speed of light and will never land

until it runs out of fuel. I don't think any of us are fearful of landing with no power . I think we are deathly afraid of a Mooney WOT on short final. 

[moodychief]

Is the passenger your wife?

[wrbix]

Is the passenger your wife?

Murder/suicide?

[N201MKTurbo]

I don't get it, you say that you are afraid of WOT on short final, so what? You are just doing a go around, maybe not by choice, but a go around none the less. We should all be proficient at that. The logical end to this scenerio is a dead stick landing, isn't that the hard part?

[sleepingsquirrel]

I don't get it, you say that you are afraid of WOT on short final, so what? You are just doing a go around, maybe not by choice, but a go around none the less. We should all be proficient at that. The logical end to this scenerio is a dead stick landing, isn't that the hard part?

This is why the discussion. What do you do besides fly in the pattern until running out of fuel? Mixture, carb heat , blipping the mags, Personally I'd leave the prop forward.

 

 The thread I remember was that on reducing throttle to land the whole throttle cable and all came loose from the throttle and it was spring loaded for WOT. Sure you have to go around, can't land a Cesne 150 at WOT, but wait until running out of fuel? Not me.

[N201MKTurbo]

I would pull the mixture to idle cutoff, it would stop the engine, wouldn't keep pumping fuel through the engine and you could restart by just pushing the mixture back in any time you wanted. Turning off the mags would stop the engine, but if you turn them back on there is a slim but real chance you could blow a cylinder off your engine if it happens to fire at exactly the wrong time.

[bd32322]

I would pull the mixture to idle cutoff, it would stop the engine, wouldn't keep pumping fuel through the engine and you could restart by just pushing the mixture back in any time you wanted. Turning off the mags would stop the engine, but if you turn them back on there is a slim but real chance you could blow a cylinder off your engine if it happens to fire at exactly the wrong time.

Just nitpicking .. If you get slow enough you can get the prop to stop windmilling and then you will not be able to restart by just pushing in the mixture, unless you crank and then its not so quick. But agreed its all you have in this situation!