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-   -   Low altitude mixture cuts in twin training still occuring despite CASA warnings (https://www.pprune.org/pacific-general-aviation-questions/463536-low-altitude-mixture-cuts-twin-training-still-occuring-despite-casa-warnings.html)

A37575 13th Sep 2011 09:35

Low altitude mixture cuts in twin training still occuring despite CASA warnings
 
The latest ATSB Aviation Short Investigation report has just been published. Issue 6 AB-2011-077. On page 35 is the ATSB report on a Twin Commanche crash at Camden on 23/12/2010.

Aviation Short Investigation Bulletin: Second Quarter, Issue 6

The highly experienced instructor cut the No 2 Mixture control just after take off to "simulate" an engine failure. Control was lost when the student mis-identified the engine failure and the aircraft went into an incipient spin. The instructor did a sterling job of recovering from the spin but the aircraft hit the deck wings level and no one was hurt.

There was a similar scenario at Camden several years earlier where the 35,000 hour instructor died of his burns after control was lost and the aircraft (a Duchess) belly landed. In that accident the instructor also cut the mixture shortly after take off and the aircraft clipped trees and landed ahead wheels up. Fire broke out instantly

I thought CASA had banned mixture cuts on take off following the earlier Duchess crash? Either way, that technique is fraught with danger of mishandling by either the instructor, the student or both. These two crashes and others before them prove that instructors should not risk the lives of their students with dangerous practices in attempts at realism.

Kharon 13th Sep 2011 10:16

Seems to me I remember this
 
Merged: The multi engine debate.
Quote:-

One well informed gentleman in other posts has mentioned both CAAP 5.23-2 (0) and the FAA Airman's Handbook as valid multi engine training references.


The question "do they read their own material? " was asked. (Good one). I have been fairly reliably informed that certain operators have been told (nothing written) to remove briefing notes (FAA manual and CAAP) relating to safe OEI operations from operations/ training manuals?.

Seems the FAA have no idea about OEI and the associated methods of teaching same.

The on going PA 31 saga would clearly indicate they do not read their own material; but this gets better. Apparently, this was the third go around of training these blokes have gone through. Seems that there was no "evidence" that "correct" asymmetric training was given during both the first and second lot of training. This is despite about a dozen blokes being recalled to ensure that asymmetric training was conducted and completed "to the satisfaction of" the instructor pilot, after the first training sessions were declared invalid.
It is rumored that the final instructor pilot asked for directions on exactly what was meant, then politely but firmly declined the invitation to conduct mixture induced engine cuts at low speed and height. Bravo that man or woman.

It seems that the use of a humble "Elite AT11 – I" was deemed as satisfactory for this exercise. There is nothing wrong with the Elite, neither the manufacturer or operator make claims that this device is any thing else except a very good, valuable training aid within it's certified limits.

The idea that it can accurately represent a PA 31 at MTOW weight with OEI is beyond a joke.

The notion that this exercise was any thing else but "negative training" borders on both reckless and negligent. IMHO I doubt that the exercise could even be legally claimed toward a type rating. Would they knock back a type rating conducted in this manner. You could just about bet the house on it.

My bold - Fair dinkum. I ask you

thorn bird 13th Sep 2011 11:19

Low altitude mixture cuts in twin training still occuring despite CASA warnings?????.
Mate its CASA FOI's insisting on this sh...t, not discouraging it!!, and worse..ie full shutdowns in the circuit in turbine aircraft!!!. sorry I dont get paid enough....

PA39 13th Sep 2011 11:42

Well to incite an argument....over 35 years I always used the mixture for engine cuts.....but i will reiterate, low level cuts using either method is fraught with danger and the instructor MUST be proficient and prepared for the unexpected, and, after the student has continuously demonstrated a high proficiency standard of handling such emergencies at altitude. That particular TC in question was one of my previous birds and it was fitted with a contra rotated engine after the original owner suffered an EFATO !

john_tullamarine 13th Sep 2011 12:08

I don't think that the problem is so much whether one can physically do a simulated faillure in a lightie.

Rather, as with all exercises, the real concern is whether the IP can rescue the situation from whatever foul up eventuates - whether that be due to the aircraft's lack of performance or the student/pilot under test's error.

ICO simulation at low level just trims your risk fat down to nothing.

Why not do the exercise at 1000 or 1500ft ? When it all goes pear shaped (as it will from time to time) you get a bit more time to catch it and fix the problem before you hit the hard bits. No guarantees .. but the odds improve greatly.

I got around the problem for all tests etc simply by making it VERY clear to the testing officer that a simulated failure below (state a height for the situation that I chose to nominate) WOULD result in both throttles being closed and the aircraft landed ahead.

Strange .. was never put to the test .. and they knew that I wasn't about to muck about.

Stupid stuff ends up, sooner or later, with embarrassment or worse.

Two very experienced test officers I knew well and with whom I periodically flew (including the one cited by A37575 who died of burns after the Camden prang) both were very skilled but ran out of steam when they simultaneously ran out of height, speed, and ideas.

The ADF materially changed a lot of ways it did business following a few very visible prangs, including the dreadful B707 crash off the Victorian coast.

Hero stuff is for simulators .. generally the worst that can happen is that the other guys get to have a good belly laugh at the pilot's errors.

The only folk who have to tread into the boundaries are the certification TPs and they tend to do things very conservatively these days.

Two areas are stupid if travelled without great care .. low level OEI operations and Vmca simulations.

On the latter matter, I recall the way a good colleague would handle the excesses of GA instructors when forced to do an endorsement, say, to complete an IR renewal ... he just applied a counter load on the rudder so that the obtained static Vmc was some considerable margin above the value for full rudder .. had a number of instructors scratching their heads .. "it went a lot slower than this last time ... ?

Having known A37575 for many years I can attest that he is both a very competent and conservative instructor. One would do well to heed his greybeard observations.

A37575 13th Sep 2011 12:13


and, after the student has continuously demonstrated a high proficiency standard of handling such emergencies at altitude.
Could you give more detail to the words "continuously demonstrated". How many practice engine failures at `altitude` would you say were needed in order to demonstrate ` a high proficiency` Maybe five, ten, fifteen or even twenty? In fact there is no figure, is there? If the student does a good job of it two or three times then he is competent and has demonstrated high proficiency.

If he then shows the same proficiency when conducting a practice engine failure shortly after take off then there is no point in thrashing him time and again with practice engine failures after take off. You are wasting his time and money. There are those instructors who simply love cutting engines after take off until such times the student makes one cock-up on identification or procedure and the instructor says "GOTCHA BY THE BALLS THAT TIME MATE" And that is the excuse he needed to do more and more engine failures until the next mistake and so on.

As one Ppruner replied the sequence of engine failure after take off is fraught with danger (unless it is in a flight simulator). If the sequence is conducted with the usual precaution against mis-handling it is not `fraught`with danger anymore than crosswind landings are fraught with danger. Having said that I agree that cutting the mixture to simulate engine failure after take off is indeed fraught with danger since a real engine failure has been deliberately induced rather than a simulated failure caused by throttle closure. Big difference and one which has caused loss of lives.

PA39 14th Sep 2011 01:24

It all depends on each individual. We are not knocked out like sausages and each studend should be judged on his merits and ability. A GOOD experienced M/E instructor (not a 200hr pop out) would have the expertise to determine when the student has reached a SAFE standard. Yep some "guns" don't need much repetition and some not so gun need more training.

I have been there, EFATO at night at 250' with a 300' hill straight ahead with beacon flashing. I thank God that I had been taught by the likes of Jim H, Treva W and Ray B on how to maintain the 3C's (cool, calm, and collected). When it happens for real, unexpected it could all go to putty real quick.

Getting back to our case study where the student misidentified the failed engine.....where was the verification? Personally I think that students rush through their drill and phases in an emergency.......the MOST IMPORTANT thing is to FLY the AIRCRAFT. Lets face it most light twins have a near zero or - ROC on one donk at AUW and the numbers preached in the FM are/were for certification purposes only, on a new aircraft with new engines flown by a factory test pilot. The cemetries are full of highly competent pilots who did everything by the book and still ended up a hole in the ground. Students had to explain to me thoroughly what they are going to do in the case of EFATO, not just parrot talk..... choices, close it down and land straight ahead, clean up and continue on, do a left or right circuit, box or oval (over a built up area?)...what altitude? If they can't explain exactly without hesitation on the ground, then they will struggle if it happens once airborne.

Di_Vosh 14th Sep 2011 02:19

Where are you going with this thread?
 
A37575 I'm not sure what you're getting at.

You've titled the thread

Low altitude mixture cuts in twin training still occuring despite CASA warnings
and then quote


Control was lost when the student mis-identified the engine failure and the aircraft went into an incipient spin.
So which is it? Did the aircraft lose control because of the method in which the instructor simulated engine failure, or did the aircraft lose control because the student mis-identified which engine failed?

Or did the accident happen simply because the simluated engine failure (regardless of how it was simulated) was conducted below a safe height?


These two crashes and others before them prove that instructors should not risk the lives of their students with dangerous practices in attempts at realism.
Agree totally. I've been told that there are more deaths from simulated EFATO's in light twins than there have been in actual EFATO's in light twins.

As others have said, I think that the practice of simulated engine failures in light twins shouldn't be allowed AT ALL below a certain height.

DIVOSH!

A37575 14th Sep 2011 15:32


So which is it? Did the aircraft lose control because of the method in which the instructor simulated engine failure, or did the aircraft lose control because the student mis-identified which engine failed?
Apologies - not very well worded. Suggest a good read of the two ATSB Camden reports - both of which are indicated by links in the initial recent ATSB publication I referred to. Mis-identification can occur whichever simulated engine failure technique an instructor decides to use. The danger lies in the mixture cut at low level since not only has the instructor have to swiftly juggle a closed mixture and a closed throttle and then re-open the ` failed` engine but he also has to take over in case the student has made a major cock-up.

If the `failed` engine does not pick up when the mixture is moved from cut-off to rich then the situation becomes grim indeed as that engine is now dead and the prop windmilling. if you think the chances of that happening (engine not picking up) is just about zero in real life, then look at it this way. When training on single engine aircraft on practice engine failures on climb out after take off, why don't instructors cut the mixture control on those single engine types to `simulate` engine failure? After all the engine types are usually similar.

No instructor in his right mind would seriously consider cutting a mixture in a single engine trainer after take off. Well, why not? The answer is simply because the aircraft would be left with no power if the mixture was moved from cut-off to rich and nothing happened for whatever technical reason. Down goes the aircraft... Same principle applies to cutting the mixture on a twin and the engine may not always start when the mixture is moved back to rich. It is always a gamble.

Unhinged 14th Sep 2011 19:44


If the `failed` engine does not pick up when the mixture is moved from cut-off to rich then the situation becomes grim indeed as that engine is now dead and the prop windmilling.

the aircraft would be left with no power if the mixture was moved from cut-off to rich and nothing happened for whatever technical reason
Sorry A37575, your argument is not specific to mixture cuts. If you use throttle to simulate engine failure and the engine doesn't pick up when you move the lever back up, then you still have no useful power. The mechanics of the throttle linkage and the mixture linkage are very similar, and neither is any more likely to fail than the other. Power is returned just as quickly whether you use throttle or mixture in the simulated failure. The gamble (as you put it) is exactly the same one, with exactly the same odds of losing.

There are two things that do give me the heebees in asymmetric training - Simulated failures at low level, and using fuel shut-off valves to do the failure. Low level failures have been thoroughly thrashed here and elsewhere, and using fuel valves to stop the fuel means an extended and indeterminate delay once fuel is turned back on before fuel will be returned to the engine: That is the really bad choice in all of this.

Avgas172 14th Sep 2011 21:03


Sorry A37575, your argument is not specific to mixture cuts. If you use throttle to simulate engine failure and the engine doesn't pick up when you move the lever back up, then you still have no useful power. The mechanics of the throttle linkage and the mixture linkage are very similar, and neither is any more likely to fail than the other. Power is returned just as quickly whether you use throttle or mixture in the simulated failure. The gamble (as you put it) is exactly the same one, with exactly the same odds of losing.

There is in fact a considerable difference, in one case the engine is completely shut down & requires a restart & windmilling only assists the restart, in the other the engine is simply idling under no thrust power & will return to full power on application of the throttle.

PA39 14th Sep 2011 22:22

Well said CM :ok:

Unhinged 14th Sep 2011 23:59


a considerable difference
The two approaches intuitively feel different, but they are not - The result is the same when you consider them objectively; The engine is producing minimal or zero power, because one of the necessities for combustion has been substantially reduced or removed. The engine continues rotating, and the restoration of sufficient air, fuel and spark will see it accelerate to normal speed.


the engine ... will return to full power on application of the throttle.
Anyone who believes that statement as a certainty, and operates aircraft that way, will eventually find out just how hard an aircraft can bite, unfortunately.

If you use the throttle to simulate the failure, a tired throttle accelerator pump may allow the engine to stumble when you push the throttle open, or very low power settings on a running engine may allow plug fouling. Where's the full power at a critical moment now ? Neither of those problems would have occurred if the mixture had been used to simulate engine failure.

There is no perfect answer, but we need more light and less heat in the discussion. Here's a couple of quotes from Lycoming. I suggest reading the whole article.(http://www.lycoming.textron.com/supp...Operations.pdf)

Big radial piston engines with short, stubby crankshafts could tolerate the abrupt technique. However, flat-opposed piston engines with their long crankshafts and attached counterweights could not as readily take the abuse of suddenly snapping a throttle shut, particularly at takeoff or climb power. Use of the latter technique would tend to detune crankshaft counterweights and could possibly result in a nasty engine failure.
...
Since it was common technique by flight instructors to terminate power abruptly to simulate an engine power loss, we had to protect the engine. As a result, we published in our Engine Operator’s Manual and in Service Bulletin No. 245, the recommendation that if the power was abruptly terminated, it must be accomplished with the mixture control. Of course, this was intended for the higher altitudes where a complete engine shut-down could be conducted safely.
...
In our publications, we then explained the reason for using the mixture to abruptly terminate power. By putting the mixture control in idle cutoff position with the throttle in a normal open or operating position, the pilot merely cut off the fuel, but allowed the air to continue to fill the cylinders with resulting normal compression forces that are sufficient to cushion the deceleration of the engine and prevent the detuning of the crankshaft counterweights.

However, any practice of simulated engine-out condition at low altitudes should be best accomplished by a slow retardation of the throttle in accordance with the NTSB recommendation.
Lastly, there are important instructional principles involved in using mixture rather than throttle to simulate the failure. When I slide a map between throttle and mixture levers, I'm signalling that this is a practice engine failure; The student doesn't know when the failure will occur or which engine it will be, and they get normal cues about the engine failing. Nothing has changed in what they are required to do, or when, or what should trigger their actions. If I use throttle, they immediately know exactly what's happened, but even more importantly, they know it from non-normal cues - The gear warning horn and the throttle lever position. I've taught them a falsehood.

In accordance with the Lycoming and NTSB documents, I do use smooth throttle retardation where appropriate, but I rarely practice asymmetric engine failures at heights where that is applicable anyway.

Old Akro 15th Sep 2011 00:16

My main argument against mixture cuts is that (especially for turbocharged engines) its not a very kind thing for the engine. There is no need for the simulated power loss to be total & sudden. Its unlikely to occur in a black & white sense like that in real life. A gradual power reduction using throttle then simulating zero thrust instead of feathering is much more kind to the cylinder heads.

As for low level training - one of the best learning experiences I've had was a simulated engine failure at about 50 ft. I don't think it needs to be part of the recurrent training regime, but as a one off experience as part of the multi endorsement it was gold. However, the caveat is that it was a country airport with no traffic and flat paddocks in front of us. It has no place in any other environment. I couldn't tell you how the instructor did the cut. I was fully absorbed with other activities. And he never restored the power. We climbed up to circuit height at about 100 fpm. The flying precision required is indelibly etched in my mind. I don't think you'd learn the lesson any other way.

Each month when I do a sim session I cut an engine (I use mixture here!). Typically midway in an instrument procedure. But here I think the main point of the training is memory reinforcement of the checks and making the initial actions automatic. Whatever SIM the club has does a reasonable job of simulating asymmetric trust.

BrokenConrod 15th Sep 2011 00:29


My main argument against mixture cuts is that (especially for turbocharged engines) its not a very kind thing for the engine. There is no need for the simulated power loss to be total & sudden. Its unlikely to occur in a black & white sense like that in real life.
It isn't ??

I have had engines quit on two occassions on singles and three occassions on twins when the loss of power was both total.........and sudden !

BC :cool:

VH-FTS 15th Sep 2011 01:19

Old Akro,

That's a strange way of thinking. You don't like being unkind to the engine by cutting the mixture, but you think a simulated engine failure at 50ft is gold. Sorry mate, that's not gold but bloody stupid. You'll end up being more unkind to the engines when you end up as a smoking hole in your flat paddock. Level terrain means nothing when you lose control.

Unhinged's post debunks the theory many hold about being unkind for many engines. Regarding your turbocharged engine, pulling the throttle would have to be done gradually over many many seconds anyway not to cause damage. However, that could be your strategy if you're trying to simulate a gradual failure rather than an instant one.


There is in fact a considerable difference, in one case the engine is completely shut down & requires a restart & windmilling only assists the restart, in the other the engine is simply idling under no thrust power & will return to full power on application of the throttle.
Avgas, hopefully you've read through some of the posts after yours, which included advice from the engine manufacturer. Pulling the mixture, in most training aircraft since about 1960, does not shut down the engine at all. If the prop stops spinning, which will prevent the reapplication of fuel creating power due to no spark, there's a good chance you've lost control anyway as the speed has dropped below Vmc.

I was a member of the 'cut-the-mixture' club and would most likely do so again if I went back to multi-engine instructing. However, I armed myself with info from the manufacturers, engineers and experienced pilots about the type I was flying and didn't go into it blindly. Together with a risk vs reward strategy when it came to student training, I was never put in a dangerous situation. Maybe one day it could have come, but I significantly reduced the risks. I never simulated an engine failure below 400ft, I considered the effect of crosswinds on OEI landings (and therefore which engine to 'fail'), and never shutdown (feathered) an engine below 2500ft. Plus all failures were in day VMC.

One CASA source said to me the CAAP's claim about using the throttle was misleading and the author had spent too much time in turbine engines, forgetting what really occurred in piston engines. Before the rotten tomatoes come, this source had 5000 hours conducting such training and knew his stuff.

A37575 15th Sep 2011 07:32


Pulling the mixture, in most training aircraft since about 1960, does not shut down the engine at all.
I am getting a bit slow in my dotage and for that reason could you run that by me again? if you cut the mixture the EGT and CHT drop sharply (CHT more slowly of course). The aircraft yaws sharply depending on the power being applied to the second engine. The `dead engine propeller windmills at a rotation rate caused by the indicated airspeed at the time and for all intents and purposes the engine is dead. And now you are staying the engine is operating? :ugh: Try as I may I cannot understand your statement that the mixture cut does not shut down the engine.

27/09 15th Sep 2011 08:44

A37575


No instructor in his right mind would seriously consider cutting a mixture in a single engine trainer after take off. Well, why not? The answer is simply because the aircraft would be left with no power if the mixture was moved from cut-off to rich and nothing happened for whatever technical reason.
I'm not sure I agree entirely. I cannot answer why engine failures are done this way in singles, except for the fact that Cessna singles like the 152 and 172 have a dirty habit of breaking mixture cables at times.

To me there is a lot of sense to simulate engine failures on singles by "Pulling the mixture". So often when the engine is asked to respond at the end of the exercise, even with normal engine warming/clearing procedures, it can be slow to respond or run rough usually due to plug fouling, something that cannot happen with a lean mixture. Also the chance of carb icing is reduced because there can be no evaporative cooling taking place.

So long as the engine is windmilling all that is needed to restart is advance the mixture.

There will be exceptions but I don't think there is any more risk in using the mixture in a light twin than the throttle to simulate engine failure. One big thing for me in multi engine training is, as has been stated by others, that the mixture cut most closely simulates a real failure and confirmation cannot be obtained from the MP or RPM guages. EGT and fuel flow need to be checked.

P.S.
I agree entirely with you about the stupidity of simulated engine failures at low level.

Kharon 15th Sep 2011 08:53

One last effort.
 
Neither the ATSB report or any of the real issues here have bugger all to do with how 'you' as a professional elect to simulate an EFATO in a FAR 23 certified aircraft.

There is requirement, under the CAO to conduct the procedure, like it or lump it.

The real point is, in the past (mixture or throttle) the engine failure occurred at height and speed which ensured (at instructor discretion) that Bloggs did not plough it into the bricks. Good sense, good airmanship and COMMAND discretion from the instructor ensured that 'Bloggs' and his sorry arse arrived back on the ramp, in one piece.

This is not the current argument being flogged around the GAAP airports, 'to the letter of the law' says the resident 'type specialist', do them, or use the Elite, or your brief will be pulled.

'The PIC must be satisfied' etc. (CAO 40.1 - God luv it) part is no longer applicable according to the 'experts' from the bastion of all things irrelevant to aviation safety.

Forget the bloody endless, pointless puerile mixture/ bloody throttle argument. Look at the 'real' cause of the Camden prang, and praise the very experienced man who saved 'em. Both.

Selah.

VH-FTS 15th Sep 2011 10:02


Try as I may I cannot understand your statement that the mixture cut does not shut down the engine.
The propeller has not been feathered, there is still a source of ignition. Enrichen the mixture on your standard twin trainer, i.e. the Duchess, and power will be restored in less than a second. Doesn't sound shut down to me.

Due to there being no risk in using the mixture to simulate the engine failure, lets consider the other benefits of using this technique. The trainee now gets the benefit of using the throttle to verify the failed engine (i.e. check that changing the throttle setting doesn't cause any yaw). They also get to practice closing the 'failed' throttle and using it as a flag when shutting down other systems. You can't get those training benefits if the instructor closes the throttle.


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