Broken Throttle Cable

[comancherookie]

I just had a throttle cable break on engine start. There was very little warning, just a little sticky the previous engine start and once the engine started, it worked perfectly. This brought me to thinking, "What if this had happened while I was flying?"

I'm thinking that modulating the propeller rpm to bring the plane down would be a good solution, another pilot suggested turning the mags on and off. Does anybody have some experience with this or another solution? I also don't know if the throttle would default to full open or full closed if a cable broke, so tech input on this subject would also be helpful.

This also shows that we need to think that these critical moving parts are 45 years old and wear/stress don't necessarily show themselves on examination. Perhaps replacing them occasionally, even without evidence of wear, is a reasonable procedure.

[Zach Grant L1011jock]

It is a common recommendation to change the control cables at engine change. Many don't but to have an original in a plane at this point is pretty rare, and probably long overdue for a change. As for the other questions, I would suggest using mixture to modulate power, not turning off the mags as fuel in the muffler will do lots of damage when it goes boom. As for spring loaded, no not normally, though I have seen some that have been modified to spring open. What broke on the cable? Was it the inner cable wire, or the outer sheath?

Zach

[comancherookie]

The inner wire broke at the push-pull. The airplane has a factory new O540. Interestingly, Lycoming had to go with a new supplier for their carb, and my mechanic says the cable mounts to the opposite side of the throttle body. Apparently that isn't a problem. This new carb has proven to be very difficult to lean, in that small adjustments go in the opposite direction briefly before going in the intended direction. This makes using the EGT/CHT and JPI fuel flow difficult to use for leaning. It takes much more time to lean once level flight is achieved than the previous engine.
Jon

[Charlie Tripp]

Right after I bought the twin Comanche 21 years ago the nut came off the attachment point of the throttle cable to the servo. I did not know anything was wrong until while in the decent the right engine would not reduce power. I used the mixture to “milk” the power while descending and did not kill the engine and feather the prop until landing was assured. The servo is spring loaded to wide open.

[Stephen Flaherty]

I had this happen a number of years ago. I was a student pilot in a Piper Cherokee getting ready to start about my 2nd solo cross country when all of a sudden I had full power on the taxiway. I failed the test (ie what to do next) and crashed the plane while still on the ground. It flipped over on its back and I was hanging upside down from the seatbelts. I unclipped, pulled out fragments of the windscreen, dug a hole in the dirt and then twisted my way out. It was an uncontrolled field.

Later the CFIs all got together to discuss "what if this happens in the air" and came to the conclusion that controlled leaning of the mixture is one option. They took a plane up and flew final approach with the throttle wide open and controlled rate of descent by intermittently pulling back the mixture. They said it worked, though I wasnt with them to experience it first-hand. Another thought was to fly to an airport with a long runway, cut the power and do a power off landing.

[comancherookie]

Technically, since you never left the ground, your successful take off to landing ratio is still intact