Scottish Information .. Pan Pan

[fisbangwollop]

Hey thaks to all you guys on my frequency earlier that remained quiet whilst I dealt with the Pan call............:ok:.....Pa28 over lowther Hill announced that throttle was stuck on max and engine RPM red line...thankfully instructor aboard and despite some grotty weather over the hills he managed eventually to get back to Prestwick and land safely.....to anyone that called me and never got an instant response sorry but i was a wee bit busy!! :cool::cool::cool:

[liam548]

blimey, throttle stuck on max! wonder how he sorted that one? well done

[Gertrude the Wombat]

Well, there's a floatpane trick for when idle gives you too much power - turn one mag off ...

(I had "throttle stuck open" on a car once. I turned the ignition off, put it in neutral, put on all lights and hooter, and forced my way to the hard shoulder. Can't do quite the same thing in an aircraft, unless it happens to you overhead an airfield.)

[BackPacker]

A single engine aircrafts throttle system is normally designed so that it fails to fully open (as opposed to fully closed like in cars). In case of a failure, you let the engine run until within safe gliding distance of your chosen field, then cut the fuel and glide to safety.

If the engine is redlining, in addition to the trick of Gertrude, you can also pull the mixture to reduce the RPMs.

In fact, the POH of the PA-28 Cadet has this as the recommended leaning procedure: Mixture and throttle both full forward. Reduce mixture - RPMs will climb initially then reduce. Set desired cruise RPMs with the mixture, leave throttle wide open. Do not operate above 75% power with a lean mixture for more than 15 seconds.

Oh, and you can also put the aircraft in a climb attitude to prevent redlining. But that's perhaps too obvious...:ok:

[Shunter]

trick for when idle gives you too much power - turn one mag offObvious now you say it, but duly filed for future reference. The fuel-off and glide would have been my default reaction I think.

[sapperkenno]

What have leaning procedures got to do with anything?! You wouldn't be leaning as per the POH (in order to get best power/economy etc)... you're just leaning to a level where the power drops sufficiently. Would make for some interesting pops, bangs and the like, but would get the job done.

A single engine aircrafts throttle system is normally designed so that it fails to fully open Does it? I've never heard of this, so how does it work? Are you suggesting that, in carbureted engines, there is a set position to which the throttle valve will go? Or are you saying that they never fully open? I'm not trying to be smart, just after some clarification, as I never knew about such things. What about on fuel-injected engines?

In all the PA28 POH's I've seen, it says to refer to the engine manufacturer's handbook for leaning procedures.

Thanks

[Gertrude the Wombat]

Obvious now you say it, but duly filed for future reference.
Hey! - I don't want people taking that as serious advice!

It's a recognised trick when taxying a floatplane to the dock, and on idle with both mags on it's moving faster than you feel comfortable with. I haven't a clue whether it makes sense with the throttle stuck open in the air!

[fisbangwollop]

Backpacker....Oh, and you can also put the aircraft in a climb attitude to prevent redlining. But that's perhaps too obvious...


Well I reckon the instructor on board ( Dr in Aeronautical Engineering ) knew that as well as when at first Prestwick radar told me they could not see him on radar i aked him if he could climb and he said yes as he would probably have to do that anyway to keep the rpm below red line!!!...:cool::cool:

[Shunter]

I don't want people taking that as serious advice!And I don't ever want to have a throttle stuck open, but if I do I'd like to think I might recall some chap on pprune reminding everyone that there is a choice between everything and nothing.

[dublinpilot]

Could you not just put the mixture leaver to starve the engine of enough fuel? I don't mean cut it totally, but you'll get to a point where there's not enough fuel to burn, and the RPM will come back.

So long as you'd pulled it far enough back to be below 75% power (which should be obvious from your resultant straight and level speed) everything should be all right.

I seem to remember Deakon advocating this as best normal operating practice some time back.

Have I got this wrong? Would it not work so simply?

[Fuji Abound]

Flaps, mixture, mag.

[Genghis the Engineer]

Well done to those who left ATC and the urgency aeroplane to sort their problem out.

Regarding a stuck full throttle, presumably in a fixed prop aeroplane - the obvious thing (to me) to do is climb to somewhere in comfortable gliding range of a useable runway, then shut the engine down and glide to land.

Assuming that you can do it without climbing into cloud! - which is where having an instructor with an IR on board is helpful, but I can't imagine any sane pilot then shutting the engine off without sight of the surface.

Failing that - accept probably damaging the engine, stick the nose down and overspeed it; there are safety margins in everything, including RPM limits.

G

['India-Mike]

Mechanical jam following full-power climb. And I mean jam - absolutely rigid. Further climb to >4000' brought rpm onto red line in cruise, but speed in yellow arc in slightly turbulent conditions. Weather precluded direct track to PIK hence lengthy divert. Little in the way of forced-landing options in the NGY area.

Student did very well indeed. I just helped with R/T and analysis to decide what he could and couldn't do. Throttle unstuck south of PIK. But that's a worry too - did the stuck throttle indicate a linkage problem that would become apparent when throttle was advanced? Again, I didn't touch the controls once. Student managed it all, right up to landing.

Apologies fisbang for pan pan as initial call. As always, a nice warm feeling in this part of the country when on R/T!

A really nice problem for de-brief what-if scenarios:ok:

[BackPacker]

What have leaning procedures got to do with anything?!

All I'm saying is that in the Cadet POH it's accepted procedure to lean with Wide Open Throttle until the desired cruise RPM is set (which is below 75%). So if your throttle is stuck wide open and you're overspeeding the engine it's perfectly OK (in the PA28-161 Cadet) to bring the RPMs down with the mixture. (Section 4.29 of the 1988 POH)

I've never heard of this, so how does it work?

The throttle cable, AFAIK, is spring loaded at the carburetor side so that if the throttle cable breaks, the springs pull the carburetors to their fully open position.

I don't know about fuel injected engines. But I would assume the same design principles apply.

[fisbangwollop]

India-Mike...Apologies fisbang for pan pan as initial call. As always, a nice warm feeling in this part of the country when on R/T!


Hey thats no problem thanks for the call thats what were here for....sorry for asking you if it was actually a practice as you just sounded too dam cool..!!:cool::cool::cool:

Anyway glad all turned out well in the end....speak again soon...:cool::cool::cool:

Paul.

[angels one five]

Applying full carb. heat should help too.

[tarnish26]

Sounds like a good job done by all concerned..student, Instructor and ATC....I guess each and everyone will have their own tale to tell...well done guys..:D:D:D

[The Fenland Flyer]

Student did very well indeed. I just helped with R/T and analysis to decide what he could and couldn't do. Throttle unstuck south of PIK. But that's a worry too - did the stuck throttle indicate a linkage problem that would become apparent when throttle was advanced? Again, I didn't touch the controls once. Student managed it all, right up to landing.Well done that student! hope I would be able to do the same in that situation, I would be worried about having to do a go around; opening the throttle and getting the thing stuck again!

[Graham Borland]

Was it OM or OJ?

[fisbangwollop]

GATOJ :cool::cool:

[Knight Paladin]

Is dealing with stuck throttles and similar emergencies (ie other then just complete engine failures) not on the PPL syllabus?

[C42]

A hefty side slip will load the motor below red line, but you would have to change sides often to stop the lactic acid building.

[stickandrudderman]

I've driven plenty of cars and bikes with throttle stuck wide open (some would say it's normal the way I drive!)
I've always used the ign switch to control rpm in such circumstances.
I understand that early aircraft had no throttle, only the mag switch with which to control speed.
I think I'd be tempted to do the same in this situation.

[BackPacker]

only the mag switch with which to control speed.
I think I'd be tempted to do the same in this situation.

You might want to be careful with switching the engine on and off with the mag switch. In-flight your engine will keep windmilling and if you do nothing to the mixture/fuel cutoff, will suck a combustible air/fuel mixture into the cylinders anyway. Since this is not ignited, the combustible mixture will then exit the engine via the (hot) exhaust. Sounds pretty dangerous to me.

IMHO if you want a sort of on/off switch for your engine it's far safer to shut the engine down in flight by pulling the mixture. Leave throttle and mags alone. The engine will windmill all the same, and as soon as you put the mixture back to full rich the engine will produce power again.

[Chequeredflag]

During the final landing of my Skills test (PA28), the examiner showed me how to control an engine with the throttle stuck fully open. Simply pulling the mixture control back and forth as necessary, controlled the revs to set manageable power settings for landing. After touch down, fully closing the mixture as normal shut down the engine. Not sure how much good it did the engine, but it certainly worked and I've never forgotten the process.

[Piper.Classique]

I had a slight variant on this, with a throttle that would move towards closed no problem at all, but would not then go back to where it had been; I found this out when I reduced power in lift to avoid climbing into the pretty cumulus cloud that was not all that far above me. As I hadn't reduced power all that much (from 2200 rpm to 1800 rpm) I could still maintain level, though at a significantly reduced speed and had plenty of time to think through my options, which were a) continue to destination b) land at the nearest suitable airfield or c) go back home. As I was at this point about halfway through a planned four hour leg, with four hours fuel (at 2200 rpm) remaining I elected to return home, on the principle that that was where the hangar and my car were, and I wouldn't upset anyone by doing a deadstick landing. The planned intermediate destination being Caen, prior to fuel and over the wet to the UK midlands, I didn't think it would amuse them to have a supercub stuck in the middle of the runway. Same for nearest suitable airfield, really, with the additional disadvantage of being stuck in the middle of nowhere. Of course, the nice five knot tailwind immediately reduced still further my already pathetic cruising speed once I had done my 180, which resulted in severe bladder discomfort at the end of the flight due to one cup of coffee too many before departure :). It's really economical on fuel at those revs, though! Anyway, I got back, did a deadstick landing and rolled off the runway (grass) onto the adjacent taxiway, before going to call Caen to cancel customs, etc. After returning to the aircraft I tried the throttle, which had miraculously freed itself once the engine had cooled. BTW, this was a brand new engine with ten hours running and a new carb and throttle cable. So I taxied in as normal. It didn't actually occur to me to declare any sort of urgency. Not that it would have done me any good at base, as no-one else was flying or sitting around in the bar at the time. We never did find out what the problem was, as I refused to put the problem carb back on unless I got a fault diagnosis and no-one seemed inclined to give me one. Anyone got any ideas? I incline to the thought that when thoroughly warm all the tolerances changed enough to make the butterfly stick, but why would this only work one way?

[BackPacker]

I incline to the thought that when thoroughly warm all the tolerances changed enough to make the butterfly stick, but why would this only work one way?

Was the throttle cable a spring-loaded Bowden cable by any chance? If so, you may have been strong enough to overcome the friction when you pulled the throttle shut, but the carb-side spring might not have been strong enough to open it again.

[Piper.Classique]

Yes, spring loaded bowden, but this was SOLID when I tried to open the throttle, and easy to close. I could feel the lever flexing when I tried to push, so I don't think it was a lack of strength.