Mixture cuts to simulate engine failure on take off.

[Centaurus]

In Australia it seems that many flying instructors on multi-engine aircraft cut the mixture control to simulate engine failure shortly after take off.

The reasoning is that it gives the student a harder job of identification because both throttles are wide open for take off - whereas a throttle closure to simulate failure makes it more obvious which engine has failed.

I understand that in UK, simulating engine failure after takeoff by mixture cut is frowned upon by the UK CAA because of the risk of mis-handling?

The engine manufacturer Lycoming state that a mixture cut is kinder to the engine due to a cushioning by air pressure of the pistons - providing the throttle is open.

But the offending throttle is normally pulled back fairly early in the identification process which rather negates the aim of the Lycoming advice which applies to full throttle. Lycoming add that despite the good engine handling that applies to a mixture cut, they advise it is "safer" to not use the mixture cut as a means of simulating engine stoppage, but to use the throttle as it has the advantage of being able to reintroduce instant power if a stuff up occurs. The US NTSB concur.

Nevertheless, experience has shown that flying schools around Australia still prefer to use the mixture cut to simulate engine failure after takeoff in a twin. Australian CASA apparently takes no position on the subject judging by their lack of interest.

Now comes the interesting bit. I wonder how many instructors use the mixture cut on a single engine aircraft to simulate engine failure after takeoff - rather than close the throttle? Well, why not? After all, it is "good" for the engine - according to Textron Lycoming.

Having said, that it is a good bet that no instructors in their right mind would cut the mixture to simulate an engine failure on a single engine aircraft at 500 ft agl after take off. And if asked why they would not use the mixture, they may give several good reasons including:

The engine may not start again.
The mixture cable might break.
Not enough time to save the situation if something drastic happens.

- and the aircraft would be up the creek without a paddle, wouldn't it?

If you agree so far that a mixture cut in a single would be potentially dangerous - then why would should a mixture cut be any less dangerous on take off in a twin?

After all, if the engine wouldn't start when the instructor tried to set up zero thrust, then in very quick time there will be a rapid speed bleed off with a windmilling no power propeller. And we all know that light twins have a lousy rate of climb with one feathered let alone with one windmilling.

And if the possibility of a mixture cable breaking in a single is a good reason for only doing a throttle cut when simulating engine failure after take off - then surely the same principle applies to a mixture cut in a twin on take off. After all, it will be the same result - which is a dead engine and a windmilling prop and down goes the aircraft. Unless feathering action is taken by the instructor real quickly after he realises that the engine won't start with a busted mixture cable. And you can just imagine the hands flying in all directions if that happens with the student wondering what the hell is happening. A recipe for utter confusion!

Would you agree therefore, that mixture cuts after take off in a twin in order to simulate engine failure - is poor risk management, compared to that of using the throttle to simulate failure. What's good for the single engine aircraft in this case surely holds good for a twin.

Think it over carefully and imagine the lawyers having your guts for garters if you killed someone while cutting the mixture after take off during training.

[englishal]

I would disagree. When learning to fly a twin, most emphasis is placed on dealing with an engine failure, and asymetric flight. In a single if you lose your engine you have no alternative but to go down, a twin gives choices, and choices kill. I would say that it is worth the risk to use the mixture to cut an engine, in order to make the situation as real as possible. Besides, the correct procedure for an engine failure at low altitude is basically mixtures forward, throttles forward, props forward, identify, verify, feather with no attemp at re-start etc all the while pitching for the blue line. IF the mixture cable was to break in the short time that it is pulled back / pushed forward then it should be possible to feather the prop and save the situation, most ME aircraft will maintain level flight and possibly climb if not fully loaded. In a single however if the engine was to quit then you really would be up s**t creek without a paddle, so no, using the mixture in a single is a bad idea. Another difference in a single is you do not have to identify a dead engine, if the right throttle is pulled back on a twin, it takes some of the realism out of it. On my ME flight test the examiner pulled the mixture on the take-off roll, no prior warning, to see how I'd react and whether the pre-take off brief "...if I lose an engine before we're airborne, I'll close both throttles and stop straight ahead...." was actually just going in one ear and out the other, or whether I was taking note of what I was saying. It all went ok, so I must have been taking it in...

You could also argue whether it is 'worth the risk' actually stopping an engine in flight during training and the flight test, or whether it is worth doing the 'Vmc demo', just in case an engine fails at the wrong moment, or doesn't re-start. I believe that these risks are worth taking, and indeed nescessary to breed a competent ME pilot.

Cheers
EA

[Wee Weasley Welshman]

An engine shutdown in flight is an essential element of a ME course.

I cannot condone the practice of using mixture to simulate (create!) an engine failure after take off. It is simply too risky.

Even if the conditions and aircraft perf state that an aircraft will climb on one with the anticipated load it is a bad idea to go there. For one, you are inviting in the exercise the student to swiftly operate the main engine controls in a state of high arousal.

He/she is quite entitled as a student to pull the wrong levers and then miss-handle the flying controls.

At 500ft?!?

You'd never get me to teach that way.

WWW

[big pistons forever]

Interesting thread. When I was instructing I went out one day to do the Forced Approach lesson in a C152. We did a total of six PFL's to a field each starting with me pulling the mixture at 2000 ft AGL. By the end of the lesson the students was doing well and we were both happy. So back to the airport for an uneventfull landing and I am allready thinking about my next student as he does the shutdown check and pulls the mixture control right out of the panel :eek: He did not pull any harder than normal and the mixture went to ICO before the cable failed. In 24 years of flying that was the only time I ever had a mixture control fail. Since then the only time I bring the mixture control to ICO is when the airplane is in its final parking spot.:)

BTW in Canada a full in flight engine shutdown feather, unfeather and restart is a requirement for the ME rating. Personnally I don't like doing them as I have found aircraft without unfeathering accumulators hard to restart in the air and I don't think the advantages of deliberatly creating an unsafe condition outways the training value

[StrateandLevel]

Closing the Mixture does not "Simulate" an engine failure, it is an actual engine shutdown.

If the aircraft were to crash as the result of such an action, the person initiating the failure if stiill alive, would probably face a charge of endangerment under Articles 63 and 64. That is one reason why it is not permitted in the UK.

I recall the RAF loosing two C130s (Fairford and Colerne) by conducting actual engine shut downs shortly after take off. They subsequently amended the drills to throttling back the simulated failed engine.

Engine shutdown in flight is also a UK ME requirement, but it is done at a safe height where there is sufficient time to restart should the other engine fail. The purpose of EFATO is to teach aeroplane control, in as safe a manner as possible. Shutting engines down unnecessarily, at a critical stage of flight is irresponsible.

[DesiPilot]

Englishal,

Ever tried engine failure with mixture ICO in FL summer when density altitude can reach 2500'. If something goes wrong and you were able to feather the propeller in time, you wont be able to get any climb performance at all.
In our school we have a policy, no engine failure using either mixture or fuel control below 3000'. Below 3000' we use throttle only. FAA also recommends using throttle to simulate engine failure below three thousand feet.
Personally I don't think I would be able to explain the controlled crash landing to either FAA, NTSB or the lawyer if i were to go down with perfectly good engine not working because of something I did. I guess living in the land of law suits makes one more cautious.

[Sweet Surrender]

C finishes off his post by saying “…imagine the lawyers having your guts for garters…” now he doesn’t actually say why they would want to do that, (apart from money) but leaving that aside I would prefer to start my reply by saying how would you feel if one of your students killed themselves because you did not train them to the best of your ability.

In my mind it all boils down to what is the most realistic way of failing an engine for a multi engine student so that they get the most benefit with a reasonable level of safety.
Now reasonable to me is possibly not reasonable to you, but we should all make our own decision based on knowledge, not on anonymous posts (including mine) on the internet

C introduces a few bogey-men in his post so we might start off by shining a bit of light on them.

C understands that the UK CAA frown upon mixture cuts, perhaps he should read R.D. Campbell’s Multi Engine book again or some of Alan Branson’s multi engine articles and see what they do.(Both UK authors)

C talks about the Lycoming article, re simulating engine failures in training, which recommends using the mixture control rather than the throttle. He states they say it is safer to use the throttle as you can reintroduce power if a stuff up occurs and that the US NTSB concur. A wonderful piece of selective quoting.

Lycoming say that simulated engine failures “must be accomplished with the mixture control” but because of a NTSB recommendation you should use throttle (slowly and carefully to avoid engine damage and failure) to fail an engine at traffic pattern altitudes in case the trainee makes an error.

Part of the thrust of C’s argument is that you don’t do it in a single so why do it in a twin. Well the reason is you have different objective’s. In a single you don’t have to identify which engine has failed. In a single you can slowly close the throttle without losing any training benefits. In a twin this is not the case, you are trying to teach a trainee to cope with a sudden swing after take off.

C talks about a mixture cable breaking, do they have a higher failure rate than throttle cable’s ?. Would you be in a better situation if the throttle cable broke ?

C introduces a number of other emotive issue’s without any substantiation but it really comes down to my opening paragraph. What is the best way of teaching a trainee to handle an engine failure after take off with reasonable safety.

These are facts not supposition:
Lycoming say that the engine would be happier if you pulled the mixture.
The student will be happier (and safer in the long run) if the training is realistic
The instructor must be aware that one (or more) of his trainees is one day going to try and kill him.

The instructor must be aware of these facts as well as his own knowledge, his experience level, his knowledge of and experience with the aircraft he is flying and the ambient conditions prevailing and make a decision that will give the most benefit to his student with a reasonable level of safety.

[GoneWest]

Heard of a (CAA) flight examiner - here in Florida - that had his ME test candidates do single engine circuits, at 1000' agl, with one engine fully feathered.

That seems to be pushing your luck a bit too far.

[I Fly]

I'm not sure what other lands require. In Australia that must be covered in the Operations Manual. I use throttle below 1000'agl and mixture above. The Ops. Manual says 500' just in case some Lawer wants to argue about a few feet. I think it is better training not to be consistend with the failing method you use. Near the airport and above 3000' I also secretly turn of the fuel. Nearly everyone looks at me with utter disbelieve, does nothing, and asks "how did you do tha". A lot of students get the idea that the engine ill only fail 'when the instructor does something'. I'm worried that we are training students that are proficient in 'simulated failures' and not proficient in real ones.
Some time ago I did an instrument renewal for an instructor. Turning inbound on the NDB I failed an engine. He handled it perfectly. A bit later we did some unusual attitudes. He was in the process of loosing control of the aircraft when he asks me "what are you doing". We had a real failure and he was lost. (turned out the needle valve in the carby got stuck). I aggree with sweet surrender "how would you feel if one of your students killed themselves because you did not train them to the best of your ability." How would you explain that to the Lawers and insurance company.

[englishal]

Desi,

Never tried it in FLA, but have in Cali in the summer. Depends on aircraft, Seneca II is quite happy to climb on one engine, two up, even at 10000' on a warm summers day. If you're not going to get any climb, then there is a good arguement for not flying that particular twin, especially if you're going to be landing at a high altitude airport.

cheers
EA

[Centaurus]

Englishal.

Because each of us have differing personal lines in the sand on what is realistic and what is safe, it is difficult to say what technique is right and what is wrong.

I noticed with regret that hardly had I originated this subject than someone starts sniping and accusing me of "selective" paragraphing. Obviously Pprune pages are not the place to repeat word for word whole chapters from technical manuals on engine failure techniques - hence my obviously inadequate attempt to reduce things to essential meanings.

So please chaps - accept this subject as a thoroughly absorbing one for flying instructors to discuss, and try not to let it degenerate into carping and heavy criticism. This latter point is not aimed at you Englishal - but those who have taken the time to add their bit.

Re pulling the mixture on a twin during the takeoff run in order to test competence at an abort. There is significant danger of mishandling if this is done - which is why it was rarely if ever done in the early jets before simulators came into being.

Unless the student reacts instantly to snap both throttles back then the aircraft can suffer severe side loads on the gear as the aircraft veers to one side at high speed (say 10 knots before lift off speed). The slightest hesitation in getting both throttles back will require swift intervention by the instructor with brakes and rudder.

If it is accepted that some students are slow to react correctly to a simulated engine failure after takeoff - whether a mixture cut - or a throttle closure - then some students may have the same problem when it comes to pulling an engine in the middle of the take off run. No point in testing a students reflexes in that manner if less than one second after failing the engine on the runway the instructor has to take control less the gear is wiped off. There is no point in practicing bleeding. Someone might get hurt! I leave the risky stuff to the bold instructors. Better still leave it to the simulator.

[Tinstaafl]

Prior to doing any failures that involve an engine shutdown & feather I checked to see if the a/c would at climb with one idling.

If it would climb with a windmilling prop then I had some reassurance that it would do so with it feathered.

When I've been instructing I've also seen (& experienced myself) the "The instructor's hand moved - here comes/there is the engine failure" syndrome. At altitude I also used the fuel selectors.

Amazing how many students during their troubleshooting talk about & touch the fuel selectors but don't effect a change in the selector's position - even when the fuel selector is the cause of the stoppage.

I had one bloke go straight to feather because his 'checks' didn't restore power. It was in the cruise & had planned to give him shutdown anyway. It was only while securing the engine he noticed the fuel selector.

Another fellow did something similar. He chose to feather as well then afterwards decided to to his troubleshoot checks. His initial procedures were more appropriate to an after t/o failure.

In both cases during the flight the students had previously correctly handled a failure using throttle. I put their less successful efforts down to a lack of the 'prewarning' that is gained when the student sees the instructors hand move to the throttle quadrant.

As for using mixture for cuts, I do above 500'. The engine is still windmilling, there is still spark & air occuring. Mixture can be advanced to restore power.

I can hide both mixtures so the student must use something other than throttle position to determine the failure, and can also test his/her initial determination by closing the suspect throttle.

After doing the drills I set zero thrust. The time period during which the mixture is closed is rather small.

I've never had trouble with with mixture failing to restore power but have had many times when the plugs foul at full rich & idle power.

As an aside, in the UK it's done on throttle and the student is expected to use yaw (& gauges if circumstances permit) then go straight to feather (after t/o situation). No testing of the initial assumption.

I found it quite awkward getting used to that when I converted to the local bit of paper.

[cessnababe]

Some other points to add to this discussion:
1 my understanding is that some aircraft mixture cables are significantly less thick than throttle cables as they are not designed to be used in the same way. Thus the risk of snapping the mixture cable is greater than with a throttle cable.
2 in discussions with a two CAAFU examiners and the CFE on this very topic last year, it appeared that the CAA did not condone the practice of using the mixture to simulate an emergency because of the very real chance of that practice becoming "for real". In the same way you would not give the student an "engine failure" in a single by removing the magneto keys.
3 regardless of the desirability of giving the student a "realistic" emergency, it is necessary to be aware of your responsibilities as an instructor. IF there was an accident as a result of mishandling, not only would you be in the firing line for a CAA prosecution under articles 63 and 64 for endangering, but if the student was injured you would very likely be the target for a civil action for negligence. Electing to carry out a non-approved procedure which leads to injury would be likely to invalidate your insurance policy and that of the school. I am aware of several cases where prosecutions have been successful and these have been followed by claims against instructors or pilots, which cost them large sums of money in legal fees not to say the wards made by the courts.

In these increasingly litigious times it is best to stick to what the book says and not take any unnecessary risks.

Safe flying!!

[DesiPilot]

A geniune question to you all fellow flight instructors out there. What are the chances of getting a full engine failure (of course other than fuel starvation)? Statatics shows that most of the time its partial power loss rather than full loss. How would one simulate partial power loss with mixture control (safely)?
And if one is using mixture controls at low altitude, how would you rectify a vapour lock?

[john_tullamarine]

Cessnababe,

Your comment on the keys recalls a DCA examiner whose party trick on instructor renewals around 30 years ago was just that .... throw the keys into the boot for a forced landing routine ... but I guess he would pick his mark with some degree of circumspect consideration ....

[Citation500]

When talking about failing an engine right after takeoff by cutting the mixture in say 400ft AGL, ever thought about the other engine failing because of a real problem? You would have how many operating engines than? :( ZERO! Thats why e.g. Swissair Flight Academy never fully feathers a prop below 5000ft AGL. Training how to identify which engine is faulty can be done way up in the sky as well, you don´t need close proximity to the ground for that.

[dragchute]

All very well to pull the throttle back on a small piston engine but try that on a larger type such as a TSIO 520, or better yet a GTSIO 520. Closing the throttle deprives the cylinders of air and reduces compression. The piston then travels the limit of the con-rod and is smartly pulled back by the mechanical components of gudgeon pin, con-rod, crankshaft and main bearings. Huge stress!

Using the mixture leaves the throttle valve wide open and allows the inducted air (minus fuel) to at least cushion the upwards travel of the piston without loading the mechanical components.

Sure, the engine may not fail in that sortie, but may fail during a subsequent flight when an unsuspecting pilot (without the benefit of an instructor on board) and passengers are faced with a catastrophic engine failure.

[Centaurus]

Drag chute. I may be wrong but if the throttle closure as a means of simulating failure was potentially dangerous, surely the manufacturer would be legally bound to advise of this in the POH? I know that the heading Caution or the heading Warning is placed in Boeing manuals if a certain action can cause loss of life etc. Do these headings appear in the POH for the aircraft you refer to?


My understanding (although I know little of these bigger GA engines) is that immediately after the engine failure is simulated by cutting the mixture on take off, within a second of applying corrective rudder the pilot closes the throttle to confirm that the correct engine has been identified. In that case the so called cushioning effect is immediately thrown out of the window because it only occurs if the throttle is wide open (as you said?)

I would doubt therefore that any regulatory authority would certify that type of engine if it could not withstand the closure of throttle from high power. It would automatically mean that any rapid throttle closure in an abort could maybe damage the engine? I thought these engines were reliable??

[Sweet Surrender]

C. I do apologise if my original reply was a bit abrupt but I honestly thought you were giving us a wind up.

You say in your reply to dragchute, what is the point in using mixture if several seconds later you close the throttle.

The point is what happens in those few seconds. You start with an engine turning at say 2600 rpm developing full power. You close the mixture which "puts out the fire". The cylinder is still full of air and while being compressed
a) prevents a sudden reversal of load on the piston/conrod/crankshaft assembly and
b)starts the engine slowing down (no power stroke and work done compressing the air)
Now when the throttle is closed the engine is no longer doing 2600 rpm (I have never looked closely but I would imagine around 1600 rpm or less). The reversal in loads will now only be a very small fraction of what they were.

You again talk about what the manufacturer states about operation of his engine. If you read Lycoming Service Bulletin 245 you will see that Lycoming are unequivocal in stating that the way to fail one of their engines is to use mixture "... if the power was abruptly terminated, it must be accomplished with the mixture control."
Because the NTSB later came out and said that "... such procedures at traffic pattern altitudes may not permit instructors enough time to overcome possible errors on the part of the applicant" Lycoming (most likely in regard to possible legal issues) softened their position and said "... simulated engine-out operation at the lower altitudes should be accomplished by retarding the throttle, and this should be done slowly and carefully to avoid engine damage or failure. " This does not sound like the statement of someone who feels that failure with the throttle is the best method for his engine.

As I just renewed my instructor rating yesterday after a break of several years, I am really enjoying this discussion and look forward to continuing it in an amicable fashion.

[dragchute]

Centaurus,

Training with such engines was always a disciplined process. The check pilot would fail the engine using the mixture. The pilot would confirm by retarding the throttle knob one knob width and doing the same with the pitch lever. The check pilot would then slowly close the throttle, enrichen the mixture and set zero thrust.

The only failure I suffered in a GTSIO was shortly after take-off with the gear retracting. The cause was a snapped gudgeon pin. Myself and seven pax had a near death experience avoiding a number of obstructions around the circuit. That aircraft had been used a few days previously by a DCA examiner who insisted on your technique during an instrument renewal!

Textron Lycoming Mandatory Service Bulletin No 245D

“Rapid opening or closing of the throttle can cause counterweight detuning…To avoid detuning during simulated engine failure, use the mixture control to shut off the engine and leave the throttle in normal open position until the engine has slowed down because of lack of fuel. Then, close the throttle to an idle condition. The throttle being open allows the cylinder to fill with air, maintaining the normal compression forces which are sufficient to cushion the deceleration of the engine. Another result of rapid throttle movement is severe strain on the supercharger gears and associated gears because of the inertia force of the high speed impeller.”

Source
http://www.prime-mover.org/Aviation/Manuf_Page/sb245d-1.html

[Centaurus]

Engine handling aside, it's all about risk management (God - I love those long words).

Because there is obviously a risk of mishandling when playing with simulated engine failures at relatively low altitude (and believe me I have had several situations where the pilot being trained/tested has caught me off guard by applying full wrong rudder during a simulated engine failure after take off) - it is safer to use the throttle method. But that is only my opinion - so it is a wise man that reads what the aircraft manufacturer has to say.

From the PA44 POH, Section 3, under Safety Tips:

Section 10 Report: VB-860
Quote:
"Experience has shown that the training advantage gained by pulling a mixture control or turning off the fuel to simulate engine failure at low altitude is not worth the risk assumed, therefore it is recommended that instead of using either of these procedures to simulate loss of power at low altitude, the throttle be retarded slowly to idle position. Fast reduction of power may be harmful to the engine. A power setting of 2000RPM and 11.5 in Hg MAP is recommended for simulated one engine operation.
Unquote.

As far as I am concerned, that is good enough for me.

One other point. Part of the asymmetric training includes practice at identification. That will normally be done in the upper air where any mis-handling by the student is quickly rectified while at a safe height.

Only when the student is considered consistently competent at the identification process would one normally proceed to the engine failure on take off practice. This too, should be done initially upper air until the student is competent.

Once that is OK then part of circuit training will be the occasional simulated engine failure after take off. This is primarily a handling exercise as the identification process has already been thoroughly covered earlier.

The argument that pulling the throttle after take off makes it obvious which engine has failed, is valid - but does it matter? Not really, because the student has already demonstrated his identification competence earlier on.

The mixture cut is certainly realistic - but as the Piper people say " it is not worth the risk assumed" - and it is hard to argue otherwise. The ever waiting litigation eagle would presumably quote from the POH.

[dragchute]

Centaurus,

A risk management poser if I may sir.

You are the chief pilot of an RPT service involved in day/night operations from your aerodrome to an island community some 150 nm away. You have a fleet of six Queen Airs, a group of average but experienced pilots and a check captain.

One of your lads returns with a feathered engine, six frightened punters and a fire truck. Metallurgy tests suggest detonation. You decide to re-write your operations manual for the type and stipulate leaning procedures. In the course of your research you stumble upon Lycoming Mandatory Service Bulletin No 245-D. So whilst you are at it you decide to address the training situation with regard to simulated engine failures.

Your dilemma: do you continue using the throttle to simulate engine failures or do you opt for the mixture control as advised in the SB?

The former will ensure the safety of the crew during training but may jeopardise the safety of a planeload of passengers during a scheduled service. So how do you address the risk?

Although your PA44 may cope with throttle closures the technique is not necessarily upward compatible with more sophisticated large piston engines!

[Centaurus]

I think it boils down to the definition of "rapid" throttle movement.
Obviously a snapped close throttle is detrimental to the good health of the engine. I do not see a measured throttle closure of (say) 3-4 seconds as "Rapid". Have you ever watched the auto-throttles go from idle to full power on a CFM 56? Now I call that pretty fast throttle opening by what I was used to on other engines - but that rate of throttle movement is normal, otherwise the engine manufacturer would not design the autothrottle system that way if it was going to compromise the engine operation.

What has that to do with a piston engine throttle movement you may ask?

The answer lies in the perception of the operator (pilot). A steady measured closure of the throttle should be perfectly acceptable engine handling for a simulated failure. If not, it is doubtful that the engine would be certified. After all aero-engines go through unbelievably rigorous testing during the certification process.

It also drawing a very long bow to accuse a testing officer of stuffing an engine in the future by his decision to close the throttle rather than the mixture. Did the engine tear down positively confirm this as the reason for the engine to fall apart?
What was his rate of throttle closure? Was this rate of closure conveyed to the engine manufacturer and their opinion recorded?

It is all too easy to blame the last pilot for a perceived wrong action when there could be other factors present beyond his control.

Interestingly some years ago in Australia the chief pilot of a C402 operation was killed along with six haplees pax when his aircraft suffered an apparent engine failure shortly after lift off. He failed to get around to feathering the dead prop and soon after flipped inverted due Vmca.

It transpired that he and all his pilots had only ever carried out their proficiency checks - which included simulated engine failures after take off - in a PA44. The engine failure procedures and associated handling were entirely different. It was all to save costs of course - but proved in the end to be false economy...

[dragchute]

Centaurus,

I have never seen rapid throttle movement defined. Certainly most operators of big pistons would consider three or four seconds excessively fast and constituting abuse of the engine! Normally the throttles are ‘walked’ up and down the quadrant by side-to-side wrist movement.

Power was always reduced gradually. From cruise at 31 inches to descent at 25 inches took several minutes of throttle walking. The next reduction was to 21 inches at 5 miles and 18-21 on base to 50 ft. When landing was assured further reduction occurred during the round-out and landing roll. The technique was not only to prevent detuning of the engine but also to avoid shock cooling.

For some handling insights on these engines try this thread: http://www.pprune.org/forums/showthread.php?s=&threadid=53550&highlight=GTSIO


Any mishandling of such engines will reduce engine life in a cumulative form, some actions more so than others. Sure I can’t unequivocally pin the failure in my instance back to the previous IRT but the consensus of opinion at the time was that the technique might not have helped. The metallurgy report found fatigue cracks in the gudgeon pin but obviously could not pinpoint the events that caused such cracks.

In arguing for throttle over mixture with such engines I think that courts would be swayed by the documentation at hand and the accepted code of practice implemented by the majority of operators. Try convincing counsel for the plaintiff that ‘on the balance of probabilities’ such a technique would not compromise ones duty of care particularly in the light of a mandatory SB to the contrary. Try arguing what constitutes rapid throttle movement when most operators think as in the thread above.

[Centaurus]

Dragchute.

Could I refer you to an excellent technical article by Kas Thomas, an aeronautical engineer and publisher of many papers on aero engine maintenance. In the March 1996 issue of TBO Advisor (USA) he wrote "Shock Cooling - Myth or Reality". His article examined the physics and metallurgy of "shock cooling" and concluded that contrary to the conventional wisdom, it is not a major contributor to cylinder head cracking.

He said there was no scientific proof that cooling plays a significant role in cylinder damage in aviation. He explained that every pilot flies through rain occasionally and rain should make a very effective coolant (more so than mere air, certainly). Yet know one ascribes cylinder damage to flying through too much rain.

If shock cooling were a definate hazard, your engine should fall apart when you bring the mixture into idle cut-off at the end of a flight because CHT's fall off at a rate of 100 degF per minute or more, in the first few seconds of shut down - triple the rate that starts the typical shock cooling annunciator blinking. Does anyone complain that repeated shut downs are causing head cracking? Of course not.
Then why are we worried about pulling the throttle back?

And in another article- this time by John Deakin who writes in Avweb - the excellent US aviation website.
Deakin writes: "I know of no real data, old or new, that supports any of the theories about "shock cooling" being particularly harmful. I thinks it's a load ofpoppycock, invented to give pilots something to sound knowledgeable about, when talking to the less experienced, and it gives flying instructors yet another procedure with which to hammer on trainees.
He goes on to say:

"On the contrary there seems to be considerable evidence that "shock cooling" is not particularly harmful. Airplanes flown regularly (and hard) seem to be the ones that regularly go to TBO and beyond. Some of these are flown in the harshest conditions found on earth such as the jungles, the artic and the desert. Above all, training aircraft are subjected to the very operations that cause the most severe shock cooling on virtually every flight, with constant simulated engine failures, aborted take offs, long power-off glides and sudden application of full power.

Aircrft that tow gliders routinely go to TBO and they are doing constant full-power climbs at low airspeeds followed by steep power off descents.
How about aerobatic aircraft which go from wide open to power off in all attitudes, at all airspeeds, show after show, sometimes multiple shows per day.
Bob Hoover goes from a full power setting into instant feather at very high speeds (probably beyond red-line), flies for several minutes that way doing his wonderful act, then fires them up and within seconds, goes to full power again. He reports that he routinely goes to TBO!
Even if there is something to the various "shock cooling" theories, I don't think it's the major factor many make it out to be. On the otherhand, if we are to worry so much about shock cooling, what about "shock heating" ? Every take off involves going from near idle power to full power within a few seconds". .................


I was fascinated by your technique of "walking the throttles" as perceived good engine handling. I believe you may be victim of a myth here. "Walking the throttles" was a technique often used in the DC3 which sometimes had a sticking throttle friction nut. Pilots would tighten the friction nut on line up and it would be damnably difficult to open up both throttles equally and smoothly because the friction nut may not clamp on each throttle with equal pressure - or simply one throttle cable might be stiff and the other OK. By "walking" the throttles until reaching full power the technique supposedly prevented one throttle from bursting forward before the other and causing the aircraft to swing.

Pratt and Whitney warned against this technique (which was very wide-spread) because it meant that the power was being introduced in jerks - instead of one smooth power application.

It seems that this myth has lasted all these years! It really is not sound engine handling to "walk the throttles" for the reason given and I would suggest that the manufacturer does not have that technique in your aircraft POH. Nor does the faintly ridiculous dribbling off of power from top of descent that you mention in your post. Some of these myths are quite tiresome and so unnecessary.

While I don't have that much experience on the small light aircraft engines of the type you operate, I do have fairly extensive experience on the large 2500 HP radials. Interestingly, we didn't "walk the throttles" and shock cooling was not a problem - if it existed - even though these engines had a huge frontal area.

It seems that in the interests of perceived good engine handling , you may be doing an awful lot of throttle fiddling for little effect on TBO times. Time to read the engine manufacturer's pilot operating manual, perhaps?

Finally back to the original point of this post - which was throttle or mixture closure to simulate engine failure on take off.

I guess we must agree to disagree. A slow closure of three to four seconds using the throttle is quite safe. A rapid movement of the mixture control to idle-cut off shortly after take off is not...

[Gen Ties]

I'm in the group that cut the mixture control to simulate engine failure shortly after take off.

My reasoning is not that it gives the student a harder job of identification (as suggested by Cenaurus) but rather I believe it gives a more REALISTIC simulation of what will happen.

It seems to me that many of the arguements against this practice fail to allow for the fact that the check pilot/instructor is also in the aircraft monitering what the pilot under check is doing.

IMO the first action after an EFATO, and what I always briefed, was to maintain control of the aircraft and and seek to achieve nominated S/E climb sped. With the aircraft in control the old "pitch up, pwr up, gear up, flap up, dead leg, dead engine, confirm with throttle, feather". The feather being a touch drill only and once correctly indicated by Bloggs, zero thrust was set with the mx and throttle being set appropriately.

During all of this I did not sit there fat dumb and happy but actually listended to and closely monitered Bloggs calls and actions to make sure he did not do the wrong thing.

To those who worry about mis identification and the wrong throttle being retarded, well isn't that why you are on board and if the worst did happen, well at least it will be on the safe side of the most dangerous situation of VMCA.

Never once in the many initals and endosements I carried out did the mx cable break and I put that in the same category as if the throttle cable broke. IE: there is not much you can do about it and the reality is that the throttle cable has an equal chance to that of the mx cable breaking.

Never once did the engine ever fail to start instantly once the mx was slid forward

To those who have mention concerns about the climb performance in this configeration, bear in mind that there is generally only two POB so in all probability the aircraft would be many kgs well below MTOW.

I can't see what the fuss is about, not one post on this subject has convinced me of any danger and in fact Centaurus post re the C402 crash which killed 7 persons convices me that realistic training has more merit than not.

As for lawers having your guts for garters if it all goes wrong, tell me what justification there is for that occur, or does that classify as a emotive throwaway comment made in order to add weight to the arguement for the against. :)

Regards

[AltHold]

Very much enjoying this discussion. However if by using the mixture you do have an incedent and the the infamous CAA get involved I think that they may quote AIC 52/1999 at the board of enquiry.

6.3 Piston Engines
6.3.1 Generally the throttle may initially be moved smoothly to the closed position; the mixture control or Idle Cut-Off should not be used to simulate engine failure. Reference to the engine manufacturer's recommendations should clarify the technique in particular cases. When the trainee has identified the 'failed' engine and completed his 'touch only' feathering drill the throttle should be advanced to the zero thrust position.

I throw this in to continue what is a lively and interesting discussion

[dragchute]

AltHold

A debate that will always harbour two camps. On the one hand are those who subscribe to the immediate concerns associated with training accidents and opt for throttle. Alternatively are those who prefer mixture as the safest course of action. In the latter technique two schools of thought sway trainers; a more realistic demonstration and consideration for the next guy to fly or travel in the aircraft.

Centaurus has suggested that the PA44 manual prefers the former method and if the manual states such, one cannot diverge. Sweet Surrender raised the issue of Lycoming bulletin 245D and that must certainly have some weight on the larger GA piston engines.

I think your CAA is having an each way bet on AIC 52/1999. A government approach to risk management. There are two ‘outs’ in the AIC, the first is the word ‘generally’ and the second deals with ‘engine manufacturer’s recommendations should clarify the technique in particular cases’.

In either case risk management issues must prevail. The trainer must consider the possibility of the student to incorrectly identify a failed engine and be in a position to restore power to the opposite side. As Centaurus so correctly pointed out, much of initial asymmetric training is conducted at a safe altitude, then the student is introduced to asymmetric go-rounds before dealing with the final stages shortly after take-off. This in itself is a form of risk management.

In training and checking line pilots it is incumbent upon the operator to prescribe a method that will both safeguard his pilots during training and not lead to possible damage that may occur at some later stage of flight. Training and checking organisations are normally attached to a transport type operation and therefore the AOC holder has a greater responsibility towards the travelling public.

I have some further issues to take up with Centaurus in relation to his last post but at this stage I choose not to cloud the debate.

[Centaurus]

Selected words from that immortal Frank Sinatra ballad:

"There were times I'm sure you knew-
When I bit off more than I could chew-

Regrets I've had a few - but then again too few to mention
I did what I had to do - and saw it through ......

"I did it my way".

That seems to neatly sum up the whole discussion, n'est ce pas?