Poor Mixture Control = Fire? I Think So

[Desert185]

While attending a fly-in this weekend, a number of us witnessed a Piper Warrior taxi out, do a rather long runup (with some backfiring during the mag check by selecting OFF). Whether it was a bad mag or leaded/fouled plugs, I don't know, but I suspect fouled plugs.

Rather than takeoff, the pilot, with instructor in the right seat, taxies back, shuts down and confers with someone rather experienced to determine what to do. The pilot and instructor re-enter the Warrior and attempt a hot start (Lycoming, carbureted four-banger). A fire in the cowling ensues after repeated cranking. Even though I am 100 yds away, I am the first to arrive with a fire extinguisher and successfully extinguish the fire after running by zombie on lookers.

You can imagine all the why's and how's like me, but I feel it all started by taxiing out with mixture full rich, causing the plugs to foul, which resulted in the excessive mag drop and the taxi back. The CFI didn't know to lean during taxi, how to clear the plugs during the runup, nor how to do a successful hot start. shame all around.

Learn from this...and carry a fire extinguisher.

FYI...

[mad_jock]

I would say they didn't follow the hot start procedure.

Over Primed it and managed to get fuel into the air filter.

More than likely 5 squirts with full mixture then waggle the throttle while cranking it.

The initial taxi will have been other issues.

But your right clueless instructor that doesn't have a clue what they are teaching or how to operate the aircraft. The won't be an airline op for starting a piston engine any more.

[huv]

Exactly what is the link between mixture control and the engine fire that seems to be caused by overpriming? Other than that both can be classified as some sort of engine mismanagement?

So the pilot did not try to stop the fire by simply keep on cranking to pull the carb-fire back into the engine (with the throttle fully open and the fuel cut off)? That is the procedure for all carburetted PA-28s I know.

[grafity]

Originally Posted by Desert185

Even though I am 100 yds away, I am the first to arrive with a fire extinguisher and successfully extinguish the fire after running by zombie on lookers.

Was this playing in the back of your mind as you ran to save the day?



Fair play to you for stepping up to the mark, but do you really have to come on here and snipe at the misgivings of the CFI? I'm pretty sure you were that experience level at one stage.

Thanks for sharing the incident, as we can all learn from it I'm sure, but a little more modesty would make you a much more like hero.

[mad_jock]

It does show the lack of understanding of operating the machinery which is quite common out there.

[cockney steve]

Well, they say "Ignorance is bliss" ! I'd expect ANY person professing to be a tutor, to have a PROFESSIONAL level of understanding of their subject.

Unfortunately, it seems too easy ,nowadays , for some halfwit to jump through a few hoops and become "qualified"

I'm buggered if I'd trust my life to someone who didn't understand the fundamentals of operating an internal-combustion engine on which our continued good health depended.

[ShyTorque]

Seems to me that the aviation industry is all back to front.

The folks with the knowledge won't teach because the pay is rubbish.

Those with no experience are more or less obliged to teach because it's just about the only way to build their own experience.

So when something like this happens it's easy to say "Ah, but they should have known!"

But they obviously don't and in many cases it's hardly their fault. Why did no-one else teach them?

But in any case, "Lessons will have been learned", no doubt.

[Unusual Attitude]

From what I'm seeing nowadays its pretty much as you've already observed.

Little Johnny gets his PPL then CPL/ IR and comes out with just over 200hrs having spent all his flying life in a supervised 'school' environment. If an aircraft has an issue, he signs it tech and goes off and flys another.

Unable to get an airline job, he then goes on and gets an FI ticket to build hours out of necessity rather than a deisre to instruct. He then starts teaching the next 'Little Johnny' still having never left the supervised school environment himself and so the cycle continues.

I personally learned a heck of a lot about 'operating' an aircraft from the older more experienced members when I first joined a group and flew with them. Some of these chaps had 30years+ flying with well over 1000 GA hours behind them and knew all sorts of practical tips and tricks you'll never get from a 200hr FI.

I then learned a whole load more once I went on to own my own aircaft and had to start maintaining it myself!

In principle I think LAA pilot coaches could have a lot to offer a freshly qualified PPL but with only 2 in the whole of Scotland I'm not surprised not many people use their services!

Regards

UA

[Desert185]

Grafity

Quote:
Originally Posted by Desert185
Even though I am 100 yds away, I am the first to arrive with a fire extinguisher and successfully extinguish the fire after running by zombie on lookers.
Was this playing in the back of your mind as you ran to save the day?

Since you ask...I was thinking why are all those pilots just standing around doing nothing? Why doesn't someone grab an extinguisher? Something had to be done and no one was doing anything.

Fair play to you for stepping up to the mark, but do you really have to come on here and snipe at the misgivings of the CFI? I'm pretty sure you were that experience level at one stage.

How else would you describe the incident? By not mentioning the CFI in the airplane? I published this as a learning experience for those on this forum who might not now have the knowledge and might have a CFI who needs a bit more vetting before being paid to do his job...and I get criticized for doing it.

An interesting side story is that another CFI ground-looped her aircraft, which is why she was in a Warrior at this fly-in.

BTW, I never had that experience as a CFI or as a small aircraft operator. Must have had good instruction and paid attention. Now that we have computers and the internet, the acquisition of knowledge should be easier...provided one isn't concerned about criticism for contributing to that knowledge. [/quote]

Thanks for sharing the incident, as we can all learn from it I'm sure, but a little more modesty would make you a much more like hero.

Hero status is overrated and over-applied these days. I'm no hero. It was just part of relaying the story, and the point is that no one was doing anything. Do people have to be taught to be resourceful and assist others these days, or do people just not want to lend assistance for whatever reason?

[Desert185]

huv

Exactly what is the link between mixture control and the engine fire that seems to be caused by overpriming? Other than that both can be classified as some sort of engine mismanagement?

Perhaps I should have outlined the details more clearly.

They apparently taxi with the mixture full rich causing the plugs to foul (mixture error one). During the runup there was the resulting out of limit mag drop. The pilot and CFI, also apparently, didn't know how to clear the plugs by leaning the mixture at a higher RPM (mixture error two). It was a 2100' MSL airport, but leaning during taxi should also be done at sea level.

One could argue that if they had adjusted the mixture properly during the taxi out, they wouldn't have had to do a hot start, which resulted in an unresolved induction fire.

So the pilot did not try to stop the fire by simply keep on cranking to pull the carb-fire back into the engine (with the throttle fully open and the fuel cut off)? That is the procedure for all carburetted PA-28s I know.

No.

Control of mixture during hot start (mixture error three). No induction fire resolution attempt (mixture error four).

[Cows getting bigger]

If the instructor had worked for me I would have fired him for wasting fuel.

[172driver]

grafity, you have just been added to my 'ignore' list.

Desert185, thanks for sharing. I does show stunning ignorance on the part of the CFI.

[Desert185]

Cows...etc

Every place I worked as a CFI in the early days of my career, I can't remember when the Chief Flight Instructor would sit down with new CFI's and talk shop on how to manage engines and airplanes. I did learn a lot from a crusty, old airplane salesman who took me under his wing. I was a CFI and he wasn't, but thankfully I was smart enough to listen and absorb his experience and wisdom. He was my go-to guy.

RIP, John. You did good.

[BackPacker]

They apparently taxi with the mixture full rich causing the plugs to foul (mixture error one).

I just checked. There is no recommendation or instruction to lean the mixture during taxi in the 1988 PA28-161 Cadet POH. The only thing regarding this is "avoid prolonged idling at low RPM to prevent plug fouling".

The pilot and CFI, also apparently, didn't know how to clear the plugs by leaning the mixture at a higher RPM (mixture error two).

Again not a procedure that's listed in the POH.

Control of mixture during hot start (mixture error three).

POH has a hot start procedure. All it specifies is "mixture full rich".

I agree with Mad Jock that the cause is most likely overpriming, NOT incorrect use of the mixture - at least not "incorrect" according to the POH. Furthermore you don't give sufficient evidence that they executed the "induction fire" emergency procedure incorrectly. So I wouldn't be so quick to pile all the blame on the CFI or the education system that he/she grew up in. I'd rather wait for the results of a formal investigation of this incident - one that gives the CFI and the pilot a chance to comment as well, and incorporates the results of a technical survey of the aircraft.

[Cows getting bigger]

Desert, agreed. That's why I would have fired him for wasting fuel despite being taught how not to! I suppose there is a possibility that a fuel line let go resulting in the incident but my betting is on the over priming theory.

I also had an instructor who managed to flatten three batteries in a week, again not learning despite extended briefings and demonstrations. I don't believe he instructs any more.

[Desert185]

Backpacker

As you expand your experience, you will realize there is more to flying than what is described in the POH.

It wasn't a fuel line and there will be no formal investigation.

It is accepted practice to lean during taxi to prevent plug fouling, particularly at high density altitudes in the mountains. There is more to life than flying from sea level airports, and pilot-induced plug fouling is avoidable...sea level or otherwise.

Live by the POH; die by the POH.

[grafity]

Originally Posted by Desert185

The CFI didn't know to lean during taxi, how to clear the plugs during the runup, nor how to do a successful hot start. shame all around.

This is the quote that made me want to write the post I wrote. The point I was getting at, is that you could have easily discussed the event without heaping "shame" on the individual.

I agree with a previous poster, the whole flight school industry is back to front. I also find it irritating when those with decades of experience seem to revel in newbies screwing up. This is neither the first, nor last instructor, to not have a clue about the workings of an engine. With that many of them out there, it's not the individuals fault, but a problem with the system.

I do respect the fact that you helped in the situation, the song was only meant as a joke. Sorry if you took it to heart, but your whole post came across to me as; I'm a hero and I share the world with idiots.

Originally Posted by Desert185

Every place I worked as a CFI in the early days of my career, I can't remember when the Chief Flight Instructor would sit down with new CFI's and talk shop on how to manage engines and airplanes. I did learn a lot from a crusty, old airplane salesman who took me under his wing. I was a CFI and he wasn't, but thankfully I was smart enough to listen and absorb his experience and wisdom. He was my go-to guy.

RIP, John. You did good.

So you understand exactly the situation this young CFI was in then? Do you think it was possible that this could have happened to you, just as easily, before John took you under his wing?

Maybe a better way you could have remembered his legacy, would have been to pull the CFI aside and try to impart some of your experience and knowledge on them, as he did for you. Rather than assume them an idiot, due to their lack of experience.

Sorry to hear that 172driver. Have a nice life none the less.

[BackPacker]

As you expand your experience, you will realize there is more to flying than what is described in the POH.

Absolutely. But you seem to think that instructors are supposed to teach the students all there is to know about flying, in any kind of condition or airplane, well above and beyond the POH. I simply don't agree with that. And in fact, if you don't fly the airplane in accordance with the approved flight manual, you might even fail your exam.

It is accepted practice to lean during taxi to prevent plug fouling, particularly at high density altitudes in the mountains.

Well, I don't exactly call 2100' MSL an altiport, so I would personally not apply "high density altitude" procedures to a take-off from there. If the engine doesn't run rough with full power, I would take off with full rich mixture. Which is - not coincidentally - what's described in the POH about these situations.

The same applies to taxi. Depending on the length of the taxi, the ambient temperature, the altitude, the RPM required to taxi and a few other factors, I might or I might not lean the mixture. And if I do, how much I lean is done purely by gut feeling - it's usually about 1/4 to 1/5th of the full mixture travel. At the very least what you call "accepted practice" is ambiguous (how much do you lean in the first place?) and not universally applicable. And not prescribed in this particular POH.

Live by the POH; die by the POH.

If there is information/instructions in the POH, or omitted from the POH, that you feel is life threatening, why not file a formal ASR/MOR or something like that, instead of making an anonymous post on a public forum which is neither read by the authorities (at least not officially) nor by the engine or airframe manufacturer?

I've said it earlier, and I'll say it again: Based on the limited information given, I feel that the cause of the fire was overpriming. And that's something that the POH warns against indeed.

When the runup failed due to rough running during the magneto check, the occupants did exactly what they were supposed to do, according to the POH: Abort the flight. But the plug fouling, not leaning the mixture during taxi, and not knowing the procedure for clearing fouled plugs - most of which is not described in the POH - did not cause the fire.

The fact that a few things happened at the same time does not mean that there is a direct causal relationship between them.

[Big Pistons Forever]

Originally Posted by BackPacker

But the plug fouling, not leaning the mixture during taxi, and not knowing the procedure for clearing fouled plugs - most of which is not described in the POH - did not cause the fire.
.

Assuming the details of the incident as presented are correct, then two facts stand out.

1) The instructor allowed the engine to be grossly overprimed

2) The POH procedure for an engine fire at start up was not followed

Fact 1 speaks to a poor appreciation of good practices in the operation of a pretty simple piston engine which is pretty sad, but fact 2 speaks to a wholly unacceptable lack of skill and knowledge by the instructor.

[Desert185]

Backpacker

You're misconstruing what I said. Read it again. I think I made the chain of events and the causal factors pretty clear.

There much more to leaning and mixture control than what the POH outlines. I would guess that you aren't an advocate of flying lean of peak.