Instructor not concerned about engine failure, restarted, and continued lesson.

[erj-145mech]

I took an internship at a state facility which has a small cessna and I couild not believe the incompetence in regard to the maintenance practices. This guy was an ex military crew leader and he didn't know that a carb needed a spring on it in case the cable was pulled out; which, by the way happened to me and my best friend. FYI, my buddy was on his private checkride when the throttle pulled all the way out into the cabin and the engine went full throtle. He was lucky his mechanic was not a moron and knew to put a spring on the carb fly valve.

.

What are you talking about? I've been working on GA airplanes since 1975, and have yet seen a spring on the throttle. I'm calling Ca CA on this one. Automobiles have springs to take the throttle to idle, but there hasn't been a certificated airplane yet have a spring to take the throttle to full. Think about it, how are you going to get the power back to land?

 

[hotwings402]

I have never seen a carb heat, mixture or throttle with a spring on it, and if you do that and its not a originally part of the airplane don't you need a 337? It would be a good idea to have it on the mixture or throttle. The mixture cable on my a/c is clamped to the carb control by a allen wrench screw, not very safe if you ask me, lets just say I check that for tightness every oil change. lol

 

[minitour]

im almost certain that the idle carb heat check is a POH checklist item. but then again i was doing a check out in a 172P and when i did that the guy looked at me and asked what the hell i was doing. so i guess it is not practiced everywhere

The first time I saw that was during my CFII training. My instructor did it every time. Well, it never stuck and a week and a half ago (or so) I had an engine fail on me ON THE RUNWAY at night as the student was doing stop and goes...Tower wasn't too happy...and I don't think the jet behind me was thrilled either, but we got it started and taxi'd off the runway rather quickly

I guarantee it will be part of every run-up I do now...every single time! If the engine had quit another 45 seconds later...we could've been in a world of hurt.

-mini

 

[BoilerUP]

happened to me before in an SP, this plane did it to a couple of different pilots. Well it was supposed to be fixed and all was well, then in flight I showed a power off stall to a student, pulled the power to idle, and the engine quit. We tried to restart it many times but to no avail. Ended up crashing in a field and destroying the airplane but me and my student were ok (he had a laceration on his leg). This is a problem with many piston engines and one of the many reasons I hate flying piston singles now.

An SP is fuel injected and should not have been a major PITA to get restarted with a windmilling prop unless it was flooded.

A school I used to instruct at had a 98 R model and it would try to quit during the idle check. Once quit on a buddy of mine when we were going to do some approaches. We said "hmmm", restarted the thing, the runup checked good, and we went flying with no problem. It was written up that the idle was set too low, and was fixed during the next 100 hour inspection.

Now I know another guy that went flying in a Bonanza and didn't know you kept the electric fuel pump OFF for landing...he learned real fast when the IO-550 quit on short final! Fortunately he was a bit high and fast and made the runway no problem. Guess it pays to be familiar with your airplane...

 

[erj-145mech]

The mixture cable on my a/c is clamped to the carb control by a allen wrench screw, not very safe if you ask me, lets just say I check that for tightness every oil change. lol

Has it ever come loose? Didn't think so. The magnetos are only held on with a couple of 5/16 nuts holding a clamp onto the base, they don't come loose either. Go to the NTSB or FAA databases and find how many have come loose. Think about this, you're fat dumb and happy cruising at 9500 feet, majically your cable comes loose and the spring takes the mixture to full rich. Bingo, now you have a real problem. You have to find a landing spot because your engine got too rich to run.

I don't think that you'll find a mechanic willing to do the installation, or an FAA inspector willing to buy it off.

I'm a disciple of the KISS principle, Keep It Simple Stupid! If is ain't broke, don't fix it.

 

[VNugget]

Think about it, how are you going to get the power back to land?

I thought about it long and hard, and couldn't think of a single way to cut the power on a piston engine. HELP, is this a trick question??

 

[RogerPodacter]

Full Cut-off valve....

 

[MDAutry]

I will simply say that if you are unfamiliar with the carburetor spring and its location then I would not tell others it does not exist. I will find you a good MX parts index and let you see when I have time. Also, the mixture does not have this spring it is only the carb buterfly valve that has the spring. The springs whole purpose in life is to give you full power when the throttle cable becomes disconnected or broken due to vibration etc. This is very logical by the way, a manufacturer would rather you have full throttle than no throttle... esp. in a single.

 

[A Squared]

but there hasn't been a certificated airplane yet have a spring to take the throttle to full.

Really? the Stromberg Carburetor on the DC-6's R-2800 goes to about 3/4 throttle (aproximately METO power) when the cable breaks. I've had it happen to me personally. I'm fairly certain the DC-6 is certificated.

Think about it, how are you going to get the power back to land?

When the time came, we were able to shut the engine down without much difficulty.

Has it ever come loose? Didn't think so.

OK let me get this straight, you're a mechanic and you don't think that throttle controls ever fail? I've got news for you In addition to it happening to me, I have two friends who it happened to. One in a Citabria and one in a 185. Here's an accident where a throttle control failed. There are also a few accidents around which resulted from throttle control failure. In fact there's an AD out for the IO-520 which addresses the way the cable is secured to the throttle arm.

 

[erj-145mech]

First off, I didn't say that throttle control failures were not going to happen. I said that a properly installed mixture control on a general aviation airplane wasn't likely to come loose.

You're going to have to show me in an IPC or a Stromberg PT series carburetor maintenance manual about this METO auto opening proceedure. I've installed and rigged many carbs on all sorts of R-2800's from Corsairs, to Harpoons to Thunderbolts with all different series 2800's from -17's to CB-16's, and I sure don't remember any springs installed to open the throttles. There's a dashpot interconnect linkage to an enrichment valve, but thats not the same. Thats gotta be a real bitch to rig those carbs. Idle position times four, full open position times four, and cable control cable break/METO postion times four, and keeping the knobs together too.

I'd like to know how you control an engine that has a cable break, with a spring that takes the engine to max power? The only control that you have is the mixture and the mags. If you turn off the mags and turn them back on again, you're going to get one hell of an afterfire, and possible blow the exhaust system apart, if you lean the engine with manual lean to control the power, then your CHT's and EGT's are going to go ape.

Aircraft components do fail, and a chronic situation will result in an airworthiness directive being issued. The typical throttle cable in a vintage aircraft will also fail if it has not been maintained properly. Those 1/16 dia steel cables will fray and they will corrode, then they will fail. If you have an aircraft that has frayed and corroded cables, then they are not being maintained properly.

The AD that you're referring to was issued in January 1987 and it was to install a castellated nut with cotter pin on the throttle cable rod end bearing. Cessna requested this AD ( via a service letter) because they screwed up and didn't have a proper safety device installed at the factory. There were no failures, only potential failures. When you come to think of it, anything in an airplane is a potential failure.