PFL with mixture set to lean

[FlyingLapinou]

Just interested to know if anyone can see a (good) reason why an instructor would want me to do a PFL from 2000' with the mixture pulled? :confused:

This was getting rechecked out in an SEP that was 20 minutes out of its 50 h service, flying at a non-ATC airfield, no one else in the circuit. After one PFL from the circuit at 1000' and two EFATOs - one at 1200' for a 180° back to the r/way with the benefit of a strongish wind - this was the last one he delivered to me.

Is there any overwhelming benefit to be gained from creating a realistic engine-out scenario, or was this just plain daft?

[Crash one]

A PFL is just that, a practice, trying such a thing with a modified engine control which would not be available in the real thing in my opinion is daft/dangerous.

[Grob Queen]

As someone who is currently learning PFLs, I am taught to pull the throttle back at Hi Key at about 2000ft to start the glide. This is the only requirement to change engine settings which I am taught.

In a real emergency of course the Emergency cockpit drills for an engine fire or failure are different! The mixture is then leaned for an engine fire and as a SA for an engine failure

[jxc]

That instructor sounds like hell :eek:
unless he expecting you put the mixture back in and not need to do PFL ?

[Halfbaked_Boy]

Even at idle the prop will still produce a little thrust, and you will have the comfort of knowing it is there.

It's a good way of demonstrating the environment you will find yourself in, in the event of a real engine failure. It sounds and feels different than simply pulling the throttle.

One of my instructors routinely pulled the mixture overhead the field at 2,000', and it was left that way until roll-out on the runway. After the initial nervousness, it is a very satisfying feeling to do it.

Just my experience, of course ;)

p.s. I knew 'of' an instructor who would position the aircraft on a high final, give control to the student, pull the mixture then turn the ignition off and throw the keys over his shoulder into the back. Now THAT is daft!!

[Crash one]

p.s. I knew 'of' an instructor who would position the aircraft on a high final, give control to the student, pull the mixture then turn the ignition off and throw the keys over his shoulder into the back. Now THAT is daft!!

I know a few glider pilots who do that regularly

[peterh337]

I think that is highly dodgy, though not unknown.

One instructor I used to fly with used to stop the prop as well; he used to do it on pleasure flights at 2000ft. Did it to me once... I let him fly it :)

A friend of mine once got an EFATO with the mixture pulled, which is worse. Luckily the engine restarted OK before they hit the ground.

http://trustedadvisor.com/public/cowboy.JPG

Some are bound to end up in aviation :)

[Erwin Schroedinger]

Seems to me that the most essential PFL precaution is to ensure that an engine will respond when the exercise is over. I'm not convinced that pulling the mixture is the safest option.

Why not ask the guy?

[4_blues]

I am taught to pull the throttle back at Hi Key at about 2000ft to start the glide. This is the only requirement to change engine settings which I am taught.

Carb Heat!!!

[Mark1234]

Actually, I'm a little bemused by the question:

This was getting rechecked out in an SEP that was 20 minutes out of its 50 h service, flying at a non-ATC airfield, no one else in the circuit. After one PFL from the circuit at 1000' and two EFATOs - one at 1200' for a 180° back to the r/way with the benefit of a strongish wind - this was the last one he delivered to me.

To me a PFL is a practice forced landing. It's not done anywhere near a circuit of any kind - the major 'skill' part of a (P)FL is identifying, and putting yourself in a position to land into some field/area where you don't have the usual cues, nor (accurately) know the field elevation; also to ensure you don't loose track of flying the plane while you're doing that.

In these circumstances pulling the mixture, or doing anything that increases the chances of you actually finishing up in said field is a bit silly IMHO.

A 'PFL' into a known airfield is simply a glide approach, presuming you can land off it, not sure it's a big deal. I guess you're adding a bit more risk that you can't go around, but landing engine out shouldn't be much of an issue either.

[Moli]

4Blues

By the fact that the poster you are referring is titled Grob Queen and refers to High Key I am guessing she (or perhaps he:eek:) is flying with a RAF VGS unit in a Vigilant motor gilder.......and i think they have carb heat applied throughout as SOP.

Am I right GQ?

Hmm then again, vigilants don't have a mixture control so i am probably wide of the mark?
Moli

Edited to add having wracked my brains, Mil Grobs do have carb heat and it is applied at all times other than when at full power. I believe that some civil Grobs don't have carb heat.

[blagger]

Moli - we also do engine stopped rejoins and landings!

ps - any instructor actually stopping the engine for PFL training to the field in your average SEP training type doesn't deserve to hold an FI rating.

[englishal]

I think it is nuts in a SEP unless you are assured of landing on a runway (or your name is Bob Hoover).

[Big Pistons Forever]

When I first started working as a flying instructor, pulling the mixture was the way the CFI wanted us to "fail" the engine for a forced approach. One day early in my instructing career, I was out with a new student and we ended up doing 2 full forced approached exercises. I felt that one more would be a good way to solidify the lesson but we were out of time so we went back home. After parking the aircraft the student went to shut down. He pulled out the mixture control and the engine died, but the knob did not stop at the usual spot and the student ended up pulling 6 inches of loose cable out. :uhoh:. The cable had failed at the carburetor rod end and it was only very good luck that it had not failed when we were doing the forced approach exercises.....

The next day a memorandum form the CFI required engine failures only be initiated by closing the throttle...........

[FlyingLapinou]

Ok, hands up and red-faced :\ I might have unintentionally misled some of you good guys and gals with my use of "PFL". (I hope you'll forgive me, I didn't do either my flight training or ground school in English).

We were over the airfield at 2000', positioning for an "encadrement", in which the pilot is required to close the throttle and hopefully land on the runway. Highly unusual to pull the mixture as well, though, at least in our club.

Reading your replies (thanks :)), I'm a little surprised that for some of you at least, landing onto a runway with engine stopped is not unusual? It seems a risk too far imho. What if the engine doesn't restart in some unexpected situation? Are you ever 100% guaranteed to make a runway, even in the most benign conditions? What if you misjudge the wind, what if the runway is unexpectedly occupied? What if you overshoot?

[FlyingGoat]

FL, just to be clear, you're discussing a total engine shut-down starting at 2000' overhead?

The 180 return to the runway is just as worrying I would have thought - apart from anyone else using the runway (maybe non-radio?). When you say a favourable wind, how strong was it?

[M-ONGO]

CHIRP? :ugh::ugh::ugh::ugh:

[Genghis the Engineer]

I can't help feel that there's a lot of "it depends" here.

I've had the ignition turned off on me by an instructor in a microlight at about 1000 ft - overhead a 4 mile x 1 mile landable beach. It was an enjoyable exercise.

I can't say I'd be particularly worried at an instructor turning the engine off in a motor glider - such as a Grob 109b, at 2000ft most places. Many people will do that themselves, because it is both "motor" and "glider".

I would be somewhat disturbed at somebody turning the mixture to ICO on me in an Arrow at 2000ft overhead a narrow short runway. If I was in, say, a Pegasus XL-R I'd be altogether more relaxed about it.

Also at 2000ft perhaps the correct thing to do is to re-start the engine, and the instructor was expecting that and just assuming that if there was a failure to re-start, then HE would land on the airfield? With that much height, I'd certainly expect if I was the checkee to be attempting a re-start (or at-least touch drills), and as an instructor I'd expect them to do that.

I'm not sure if they still do, but microlight flying competitions used to routinely include spot landings from an engine stop at (1000ft?) in the overhead.

It all depends !

G

[mad_jock]

to be honest i ain't that bother at the thought.

My main concern would be the cooling of the engine and any potential damage to it.

If the gingers said thats fine and there was some where to plant it why not but there ain't going to be that much difference to flight idle

[Jan Olieslagers]

The one time I was worried: when the examiner cut both magneto's just after take-off, perhaps 3 feet off the ground... scary scary scary, and as I was on my exam there was no shortage of adrenaline anyway.

It has happened to me since, on renewal test and the like, overhead at 1000' or so, and it never really worried me. The shorter the runway, the better one must be at side-slipping, just as much as required. But the sound of the wind is eerie. Suppose glider pilots are better used to that.

[Luddite aviator]

Up untill a few days back I would have thought putting the mixture to idle cut off when doing a PFL was unwise.

But I now have to consider if there is a good reason for this or is the student telling the whole truth so I will leave comment to Those who have far more wisdom, insight and qualification.

[Mark1234]

I think it is unusual, but not unheard of. As Genghis says, there's a lot of 'it depends'.

With respect to (ever) being assured of the landing, gliders do it all the time. Essentially you're staying higher than a best glide profile for the whole approach and throwing away the energy late on.

Gliders do it by flying half airbrake (or spoiler), and having the option to open more to descend, or close to essentially 'climb' on the profile.

I've only flown a stopped prop approach once (instructor request) and a lot of idle approaches. The technique is similar - stay high (but not too high) throughout to keep a margin, slip, take flap (or in extremes, S turn) on final to kill energy and (assuming plenty of runway) aim 1/3 into the field, NOT for the numbers. That way a little unplanned sink means taking the flap later, or maybe landing short of your aim point, rather than in the hedge.

If the trees are getting a bit too big you can always cut the corner, and if it's looking really bad land on any available bit of grass, even crosswind. Few a/c in private use are going to fall apart if presented with grass, the runway is not an absolute requirement, and airfields are usually more likely to be obstruction free than the surrounding fields. Rather dramatic for an exercise mind you!

[Pilot DAR]

My own opinion is that the risk outweighs the benefit of actually stopping the engine of a single at any point. The very small additional "experience" is really not worth the chance of something going wrong, and needing a stopped engine you can't get going again. If it must be done, it should be at altitude, and with a briefing. The affect is the same far form the ground, and close to it. I am required to stop and feather engines on twins during flight testing sometimes, it gives me the willys, and I orbit high over the airport.

There's no real need for instructor drama during training. Accidents happen then too, and it's nice to be able to explain to the insurance company that you were doing everything to mitigate the chance of an accident. Deliberately stopping an engine would not be that!

[abgd]

There are quite a few reports of people who practice forced landings regularly being caught out when they have to do one for real, and find that their glide angle is rather steeper than they expected when the engine is completely stopped, so I can see some rationale. I leave other people to decide how sensible the idea is - near a big runway I can see it might be arguable.

We call them 'glide approaches' as in 'downwind for glide approach' and not 'downwind for forced landing :O'.

My favourite apocryphal story I've heard is of the student who has been doing lots of procedural training on the ground. When doing a pfl, and before the instructor can stop him, he deftly turns off the fuel, switches the switches, then pulls out the keys and throws them to the floor.

[4_blues]

In the case of PFLs I find it good practice to turn off course 10° right/left when 'warming the engine' to allow for the extra lift generated. By the time you are back on track I like to think the effect is cancelled out. However, having been fortunate enough to not experience all going quiet Im not sure that this is of any real benefit... but I do like a challenge! :p

When doing a pfl, and before the instructor can stop him, he deftly turns off the fuel, switches the switches, then pulls out the keys and throws them to the floor.
Was the instructor sleeping at the time? :=

p.s. I knew 'of' an instructor who would position the aircraft on a high final, give control to the student, pull the mixture then turn the ignition off and throw the keys over his shoulder into the back. Now THAT is daft!!
I too know a similar chap!

4B

[bookworm]

My own opinion is that the risk outweighs the benefit of actually stopping the engine of a single at any point.

But we're not talking about "actually stopping the engine", are we? We're talking about pulling the mixture to ICO. The prop won't stop, unless you slow the aircraft down to a speed that allows it to do so. The engine is still turning.

Why is there a better chance of the engine producing power again after the throttle is pulled and restored than after the mixture is pulled and restored? One line of thought says that induction icing is far more likely if you use the throttle to simulate zero thrust than the mixture.

[peterh337]

I would think that ICO would deplete the fuel piping of fuel, so it would take longer to get the engine delivering power, than if one closed the throttle.

That is why one does ICO to shut down: to make sure there is supposedly no fuel left anywhere near the engine (but you obviously know that).

[S-Works]

I seem to recall that one of the certification requirements for a CofA aircraft is that it must restart following the mixture being pulled in flight?

Not that I would condone such an action which frankly is stupid. Why increase the risk when simulating it serves the same purpose?

[peterh337]

Yes but the required maximum restart times require balls of steel if you are actually going to do it.

Cue the other debate about running one tank to empty, to be sure all one's fuel (well, for 99% of people, all the fuel they think they still have, plus or minus about 20% ;) ) is in one tank and thus all usable.... I never agreed with that either, especially when flying in the very places where you might actually need to do that.

[Mark1234]

I'm inclined to suggest that perception of risk is rather a personal thing. Why do we do anything, when often doing nothing is less risky - be that flying, rock climbing, crossing the road... or changing fuel tanks in flight? Presumably because we think the value outweighs the (additional) risk.

Assume it won't restart. *Personally* I'm of the opinion that a permanent loss of power *over a decent airfield* ought to be a complete non-event - which was why I wanted to clarify we weren't talking about a simulated off field landing. Frankly, I'm probably more worried that the fuel selector will fall off in my hand changing tanks at an inopportune moment. I'm also very glad I've experienced a true power out approach and landing, (right down to the roll out) - I found it a markedly different experience to a 'simulated' one, though I suspect that might be 90% psychological. I was surprised how much time I had to fluff around early on at height, and how quickly it all came up after turning final.

I wouldn't make it standard procedure, but for me there was definitely a value. Not sure it would have been as worthwhile if we'd re-lit and gone around.

[FlyingLapinou]

Thanks all for your thoughts and detailed replies: interestingly, it looks as though posters are divided on this one?

As Genghis said, there are a lot of "it depends". To clarify, I was getting re-checked out on a 120 hp Robin DR400, we were the only ones in the circuit at the time, the wind was about 15kts on the ground, maybe 20kts+ in the air, no crosswind to speak of, paved runway is 1100 m x 20 m with a shorter but wider grass strip adjacent to that, separated by a shallow ditch. We took the paved runway.

There was definitely no expectation I would attempt to restart the engine and the controls were firmly with me. This was a power-out approach and landing through to roll-out.

Well, I just wanted to see what other folk think about this, and get a feel for whether it's common practice. Seems like it's an exercise that's not done frequently, but done all the same.

Mad Jock: yes, I was wondering about engine considerations. What are gingers, btw?

Mark1234: I can see how useful glider experience would be, it's on my "to do" list :ok:

[Genghis the Engineer]

As described, whilst it's not an exercise I'd make a habit of, it's not a bad one and from 2000ft I think acceptable.

I would however probably (if an instructor did this to me) in the first instance on my touch drills say "oh gosh, the mixture has been accidentally set to ICO, I'll increase it to rich and see if the engine will restart")

G

[bookworm]

I would think that ICO would deplete the fuel piping of fuel, so it would take longer to get the engine delivering power, than if one closed the throttle.

I don't think so. The mixture control cuts off the fuel pretty close to the injectors/carb, so I doubt there's a time issue.

interestingly, it looks as though posters are divided on this one?

I don't think there's much division on the practice. While I'm happy to examine the pros and cons in the spirit of debate, I can't find much support for using the mixture control on an SEP.

MEP debate (http://www.pprune.org/flying-instructors-examiners/54429-mixture-cuts-simulate-engine-failure-take-off.html) and another (http://www.pprune.org/tech-log/10351-simulated-engine-failure-throttle-mixture.html).

Schiff's view (http://www.barryschiff.com/sam_pp3.htm)

FAA advice (http://fsims.faa.gov/WDocs/8900.1/V05%20Airman%20Cert/Chapter%2002/05_002_002Rev1.htm)

SEP Accident (http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20001211X10189&ntsbno=SEA98LA068&akey=1) and MEP accident (http://www.atsb.gov.au/publications/investigation_reports/2010/aair/ao-2010-111.aspx)

[B4aeros]

The problem with those examples, Bookworm, is that none of them pertain to FL's situation, ie a glide approach to a full stop landing.

Questions as to whether the engine will restart before touchdown, or whether the student will shut down the other engine are irrelevant when the intention is to land a SE aircraft with the engine shut down.

I would argue that an experienced instructor in a simple aircraft should be able to perform an engine off landing onto a reasonably sized airfield with a 100% success rate. Students who have been taught to do the same will be a lot more confident & capable of coping with a real engine failure.

I learnt at a reasonably busy airfield, all my 'glide' approaches were with the engine running. It would have been nice to do a few engine off glide approaches.

[peterh337]

The problem is there is no such thing as a 100% success rate in this game.

Not when landing on a normal GA sized runway.

The student might do something daft like drop the gear or the flaps, and then where has your glide ratio gone?

One should simply not take risks like this. It is pointless. In the extremely rare chance of a real engine failure, most pilots who can fly can put it down into some field - IF there is a field.

[BackPacker]

I don't agree.

IF the student has shown to be able to do multiple PFLs with good success (like normal, with the throttle closed/mixture rich) and IF you have a nice wide, long and quiet runway available, I can certainly imagine that the instructor would pull the mixture to ICO and let the student perform a proper glide landing. For instance as the capstone landing after a training session on PFLs.

Provided that the instructor watches the student like a hawk and doesn't let something silly happen, like dropping full flaps too early, this can be done safely, IMHO.

And it's a great confidence booster. We all know that with the throttle closed the engine still delivers a bit of power, and if things go bad, you can always go around. But to pull off a successful PFL with the mixture closed, you really have only one shot. Plus, the flight characteristics of the aircraft are for real - there is no idle thrust. In a sense it can have the same confidence booster value as sending someone first solo.

And hey, gliders do this all the time, safely. You just have to know proper heights, glide angles and so forth.

But I agree that PFL training by default should be done with the throttle closed. Using the mixture to stop the engine should be an exception, and only under the conditions described above.

[Pilot DAR]

I'm not so concerned that the engine would restart - it will.... unless the not so robust mixture control cable breaks when someone pulls too hard on it, then you're not going to get it to rich again. This has happened - is it worth the risk? Not for me.....

[Big Pistons Forever]

I don't agree.

IF the student has shown to be able to do multiple PFLs with good success (like normal, with the throttle closed/mixture rich) and IF you have a nice wide, long and quiet runway available, I can certainly imagine that the instructor would pull the mixture to ICO and let the student perform a proper glide landing. For instance as the capstone landing after a training session on PFLs.


At the risk of sounding like a broken record I will again point out that roughly 80 % of all engine failures are directly caused by the actions or inactions of the pilot. I personally think that instead of concentrating on what happens after the engine fails, flight schools should put much more emphasis on teaching the students to not let the engine fail in the first place.

Also for every total engine failure accident statistics suggest there are 2 partial engine failures, another scenario which is often totally ignored in PPL training and where PFL's with the engine actually shut down do nothing to prepare the students

The reality is that the least likely scenario for an actual real world engine failure is when a aircraft with sufficient uncontaminated and properly selected fuel, no carb ice and which had a normal runup and developed full power on takeoff; suddenly has the engine completely stop with no warning.......yet this is the exact scenario that is exclusively taught in flight training to prepare students for an "engine failure".

[BackPacker]

True. Not to mention the subtle clues that engines may give you before they fail altogether. Who was ever taught to do an airborne magneto check? What if the oil temperature rises without explanation? Has anyone ever run a tank dry during training, simply to see what happens and how long it takes for the fuel lines to fill themselves from the other tank after selecting it?