Throttle stuck at full power?

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skipone

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skipone
I've heard of the scenario happening to a couple of pilots where they tried to climb over mountains (10,000 feet ) and as they started to make their descent the throttle got stuck at full power as they tried to reduce power. The cable snapped, or the screw came loose. They had no other option than to cut the mixture, kill the engine, and glide down.

1. Is that the only option available?

2. Does that mean you could continue flying at whatever RPM it was stuck at until you reached your destination and then cut the power and make your descent? Or do you have to bring it down immediately?
 
Probably one of the better in-flight emergencies you could have.
skipone said:
Does that mean you could continue flying at whatever RPM it was stuck at until you reached your destination and then cut the power and make your descent? Or do you have to bring it down immediately?
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I can’t imagine why you’d have to bring it down immediately, if all else is functional. Keep the power at whatever it’s stuck at and then overfly your destination, glide down and land.
 
What Tom said. Another thing if the engine is at or above red line might be to try running on one mag.
 
skipone said:
1. Is that the only option available?
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You could always jump, I guess.

There is a video on YT and other places by now of a guy and gal who had this problem; they had a camera running in the back seat of all things.'
 
RyanB said:
Probably one of the better in-flight emergencies you could have.

I can’t imagine why you’d have to bring it down immediately, if all else is functional. Keep the power at whatever it’s stuck at and then overfly your destination, glide down and land.
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My thoughts exactly. No need to land immediately.
 
At 10.000 ft I would not cut the power with mixture. If a constant speed prop plane it won't care about the power setting when you descend. In a fixed pitch airplane you are not going to be near red line until you descend to about 8000 ft. 200 FPM would work just fine.
 
Above 8,000 ft behind a NA engine with a CS prop, I fly with open throttle whether I'm climbing, cruising, or descending. Altitude, blue knob, and red knob give you plenty of control over engine power to get to a safe place to spiral down and look for a mechanic. If it's a fixed pitch prop, it's the same story and just one less knob to worry about. A turbo would change things and I don't know what I'd do in that situation. But in the planes I fly, I would probably keep the engine running at full power until I was in the pattern at my destination. Even if I needed to slow down earlier, I definitely wouldn't try to kill the engine until I was certain I could land on a runway.
 
Nobody every crashed into the sky. You can fly for a while.

The mixture is not either one or off. You can lean it carefully to reduce RPMs. With large altitude changes, you need to adjust it again.

A club member, now an A&P was returning a 152 from a remote maintenance shop for carb work. The throttle jammed and in trying harder to pull it back, he actually pulled the entire thing out of the panel. Using the mixture, he was able to land normally at home. I never heard why the throttle stuck, but I do know we didn't go back to that shop again.
 
What everybody else said. If the power was OK at altitude it's probably going to be OK on descent. Descent speed might be an issue. Still, you can remain at the altitude where the power was OK until until you reach your destination, kill the mill and glide down. No emergency is good, but if I have to have an emergency, that's the one I'd want.
 
Ever watch a WW-1 flying movie? One thing they got right - At least some of the engines had really primitive air / fuel control. Instead of a carburetor where you control the throttle and just tweak the mixture, they had one lever for air, one for fuel - change one, you have to change the other - and get it reasonably close if you want the engine to stay running. Not good for sudden power changes. So, solution- back to the movies - recall how airplanes sounded when they came in for landings? brAP quiet brAP quiet... They had a button to blip the magneto and control the power. The problem back then was that the rotaries ran a total loss oil system with the oil that lubed the main/ rod bearings being burned like many two stroke engines today - so too long on the blip button and you would foul the plugs and not have power when you let go. WOO HOO! Fun times! Now, in a "modern" engine, if you cut the ignition, you get a combustible mixture in the muffler which can go BANG when you turn the ignition back on. But, push come to shove, it may be worth risking the muffler. Or, you could "blip" with the mixture control - pull it right on out for a couple seconds, push it back in for a couple - no spark plug fouling, no extra fuel in the muffler, control of the power - life is good.
 
I had my T-Craft throttle at 2000 rpm once when the clevis bolt at the throttle arm fell out, had to shut off the ignition to land... prop kept windmilling so I could work it like an old time rotary engine. Found the bolt still laying in the bottom cowl, nut and cotter pin nowhere to be found, found a scrap of safety wire to hold it together for the flight home.
 
steingar said:
I would somewhat tremulously remind you that lots of guys died in non-combat related accidents in those things, but training and flying in them. Average life expectancy for a pilot in WWI was two weeks.
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Yup.
Bad airplanes with (very) bad aerodynamic behavior.
Primitive engines without modern carburetors. (as mentioned - too much blip and you kill the engine on final. Oops.)
Minimal training.
etc.
But, still, understanding what they did with what they had is a way to add one more potential tool to ones inventory that could be used if brown stuff ever hits the fan.
 
This happened to me while borrowing a buddie's Pitts for an acro flight above the airport. Throttle cable broke at WOT. No big deal, just high speed steep spiral down to pattern altitude, enter the pattern and pull the mixture midfield downwind and land, but the interesting thing is that the prop did not come to a complete stop until after I'd turned off the runway onto the intersection at nearly walking speed - meaning I could have pushed the mixture back in at any point and gone around. Metal prop, Lyc. IO-360.
 
Bolts falling out. Cables breaking. The stories go on. A clear lack of smart maintenance and inspections. Engine controls don't last forever and they're not that expensive. We always changed them when the engine was overhauled or changed out. Every inspection, even 50-hour oil changes, we looked at the connections, both at the lever and at the cable housings, to make sure everything was secure and the hardware wasn't worn out or improperly locked and the systems were rigged properly. It takes a whole two minutes to do this.
 
Had a throttle cable break as I was reducing power on final once. Not nearly as exciting as the time one flap blew up at about 400 feet on final, thank God they were stick flaps! You do not have enough aileron function in a Cessna 140 to compensate for one flap up and one down. You guys with Cessna 140's check the flap bracket on the inboard edge of the flaps. When the birds are tied down and the tails are facing the wind the flaps can bang down and damage the bracket. Flaps on 140's should always be down when left unattended.
 
It's my understanding that power on many WW-I airplanes was always max throttle so power was controlled by a button on the stick which would cut the ignition when pressed. Of course cycling the mixture would do the same thing.
 
Tom-D said:
some pilots use wide open throttle for flight. and manage power by mixture.
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That’s often referred to as WOTLOP.

Wide Open Throttle Lean Of Peak.

A partially closed throttle plate has been compared to a dirty air filter - why would you choose to restrict the flow of air to the engine?

As an aside, the carbs on a ROTAX are spring loaded to go to full throttle if a cable breaks. There are two cables, so a single cable breaking will mean very rough running at partial throttle. Full throttle will smooth things out, then proceed to a landing as others have suggested.
 
skipone said:
I've heard of the scenario happening to a couple of pilots where they tried to climb over mountains (10,000 feet ) and as they started to make their descent the throttle got stuck at full power as they tried to reduce power. The cable snapped, or the screw came loose. They had no other option than to cut the mixture, kill the engine, and glide down.

1. Is that the only option available?

2. Does that mean you could continue flying at whatever RPM it was stuck at until you reached your destination and then cut the power and make your descent? Or do you have to bring it down immediately?
Click to expand...
I've heard stories like that before. We must be doing something seriously wrong in training, when so many pilots fail to realise that it's the mixture and throttle together that control power, not just the throttle. Yes, you'll probably want to move the mixture to cutoff on final, when the runway's assured, but why do it before that? The engine might vibrate a lot when you pull the mixture really far back (if your fuel-air distribution is uneven), but it won't stop working.

As someone else mentioned, many of us leave the throttle wide open for most of the flight, and use the mixture as the primary power control.
 
FastEddieB said:
Wide Open Throttle Lean Of Peak..
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Is not advised for all aircraft or all engines.
This is why mixture may managed differently according to equipment requirements.
My Warner had a plenum chamber, and will distribute fuel much better than my 0-300.
 
Dan Thomas said:
Bolts falling out. Cables breaking. The stories go on. A clear lack of smart maintenance and inspections. Engine controls don't last forever and they're not that expensive. We always changed them when the engine was overhauled or changed out. Every inspection, even 50-hour oil changes, we looked at the connections, both at the lever and at the cable housings, to make sure everything was secure and the hardware wasn't worn out or improperly locked and the systems were rigged properly. It takes a whole two minutes to do this.
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I'm a big proponent of careful, regular inspections. But they can't catch everything...I did have a mixture cable seize up at about 300 hrs TTSN. No warning whatsoever in terms of change in stiffness, free play or feel beforehand. It was certainly an anomaly, but threads like this are good to think through the response if the unexpected happens.
 
Tom-D said:
Is not advised for all aircraft or all engines.
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Yup. The POH has things to say about such operation. Lycoming says, for its naturally-aspirated engines, that you can do whatever you want with the mixture when at 75% power or less. At lower altitudes a wide-open throttle will deliver more than 75% and you could risk damaging the engine by leaning it aggressively to reduce power.
 
SoCal RV Flyer said:
I'm a big proponent of careful, regular inspections. But they can't catch everything...I did have a mixture cable seize up at about 300 hrs TTSN. No warning whatsoever in terms of change in stiffness, free play or feel beforehand. It was certainly an anomaly, but threads like this are good to think through the response if the unexpected happens.
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It would be interesting to know why it seized up. There were some problems with cables that had nylon liners in them, and if the cable was routed close to the exhaust that nylon could melt and seize the cable.

I've seen a carb heat cable break due to misrigging. The wire wasn't clamped properly by the clamp bolt, which had an extra washer under its head, so that once the wire was secure the bolt wouldn't turn in the lever as the cable moved it back and forth, and the wire fatigued and failed. Another carb heat control failed when its wire got so deeply grooved as it vibrated inside the housing (which is a tightly coiled wire) and it broke at one of the grooves. Takes many hours to do that, more than a TBO. I've found carb heat cable clamp bolts worn three-quarters of the way through, and the hole in the lever nearly worn right through the edge of the lever. A carb heat failure in the right sort of engine on a day when the carb ice risk is high could be fatal.

A throttle cable failed due to old age when the student yanked it back as the airplane went into an intentional spin, and the engine went to idle; the instructor took control and set up for a forced approach, and in the glide he told the student to stick the throttle knob and shaft back in the hole (the wire had broken right at the end of the shaft) and it pushed the wire and the engine went to full power so they flew home. That sort of luck would be rare indeed.

Some carb throttle levers have a spring to take the throttle wide open if the cable fails. I've only seen a few carbs with that, and no injection servos. Never seen a mixture control that's sprung to full rich, either. Cable failures can have serious and expensive consequences.

Flap failures? Fraying or corroded cables. A friend had one flap suddenly retract from 20° to full-up right after takeoff in a 185 floatplane; the airplane rolled and hit the water. The pilot and single passenger got out and swam to shore. Could have been a lot worse. The down-cable on that flap had failed. Those cables run under the floor and up the rear doorposts and are hard to inspect without taking the interior out. It costs money to do that, so it often ain't done. I used to find lots of interesting and scary stuff.
 
Dan Thomas said:
Yup. The POH has things to say about such operation. Lycoming says, for its naturally-aspirated engines, that you can do whatever you want with the mixture when at 75% power or less. At lower altitudes a wide-open throttle will deliver more than 75% and you could risk damaging the engine by leaning it aggressively to reduce power.
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The power is also reduced as you lean, so you'll soon be below 75% even with the throttle wide open.

"Aggressively" is the only way you should lean with the throttle wide open. Leaning just a little bit makes the CHT run hotter; leaning a lot makes it cooler again, and brings the engine safely below 75% power.
 
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Related, I was at the Bonanza service clinic and they found the throttle return spring(probably a way fancier name for it) missing on my plane. Thats the spring that would hold the throttle wide open if the throttle cable broke. So the plane is designed to fail in WOT.
 
charheep said:
Related, I was at the Bonanza service clinic and they found the throttle return spring(probably a way fancier name for it) missing on my plane. Thats the spring that would hold the throttle wide open if the throttle cable broke. So the plane is designed to fail in WOT.
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Not likely missing. Just never had one. Not many carbs do anymore.
 
charheep said:
Related, I was at the Bonanza service clinic and they found the throttle return spring(probably a way fancier name for it) missing on my plane. Thats the spring that would hold the throttle wide open if the throttle cable broke. So the plane is designed to fail in WOT.
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Just like the H-34 helicopter. A VNAF pilot told me of his experience when his throttle cable was shot away. He got home OK and just autorotated to parking. (he said).

I had a failure to WOT in my Luscombe 8A some years ago. More irritating than scary. I was near my airport, at 1500', traffic low. I had checked everything under the cowl on preflight. You do have to open up the cowl just to check the oil. I did the mag thing and used carb heat. The A-65 doesn't have a mixture control. Yes, I had concerns. But on the upside, not my first emergency, I had altitude and airspeed, was near the field and had a Comm glider cert in my pocket. The 8A has low wing loading like a glider. The landing did not cause panic and was uneventful. I even taxied to parking blipping the throttle. Found the clamp holding the throttle cable had loosened in flight.
 
Shepherd said:
Fly it like a WWI fighter. Switch the mags on and off to control the speed.
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Too hard on the exhaust system. It causes big explosions in there and cracks stuff. Pulling the mixture is safer.
 
David Megginson said:
The power is also reduced as you lean, so you'll soon be below 75% even with the throttle wide open.

"Aggressively" is the only way you should lean with the throttle wide open. Leaning just a little bit makes the CHT run hotter; leaning a lot makes it cooler again, and brings the engine safely below 75% power.
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I like to watch for the CHTs to drop a bit when leaning...of course this lags EGT drop by a bit, so you have to be patient. My technique above 8000' DA is WOT, the "big pull" to lean mixture to where rpm drops, then adjust mixture to get desired fuel burn. I like 7.5-8.0 gph and let the airspeed land wherever it may.
 
Dana said:
Maxnr said: ↑
The A-65 doesn't have a mixture control.
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Some did. It was available. The Stromberg carb has the location for it, and it's just capped off if it's not installed. I have a carb here with all the stuff there in it. I also machined the parts to make my own for the Jodel.

A-65s also usually have straight stacks, and turning the ignition off and on again is much less likely to crack something. Mufflers not only resist noise, they resist that big concussive pressure wave an afterfire makes, and so they crack. I had mufflers in the flight school airplanes crack when the students would inadvertently turn the mags to "off" then on again in the runup. I had to keep training them to let the engine die if they did that, then restart at idle to avoid it. I even found intake gaskets blown out by the concussion traveling back through an open exhaust valve and out the intake during the valve overlap.
 
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