Reducing the risks in engine out training

[Hudson]

The syllabus of training of a local flying school requires the instructors to simulate engine failures after take off (on twins), by cutting a mixture when above blue line speed.
Practice asymmetric landings are made with the prop feathered.

Is it not safer to simulate engine failure at these low altitudes by closing the throttle to idle - then set zero thrust? And for an asymmetric approach and landing to be made with zero thrust rather than fully feathered?

Are mixture cuts on take-off and feathered landings placing realism ahead of flight safety considerations?

Hypothetically, if an accident occurred which could have been prevented if throttle closure had been used rather than mixture cuts and feathered landings, would the student have grounds to litigate against the instructor and the school for using a training technique that carried with it a significantly higher risk factor than with throttle closure to simulate engine failure?

[GT]

I most certainly DO NOT shut down an engine in the take-off or climb-out phases of flight. As you suggested, I retard the throttle of one engine to idle and give back zero thrust once touch checks to feather have been carried out correctly. I'd be interested to hear what anyone else thinks on the subject.

[Bear Cub]

An operations manual I read for a school said "mixture may be closed ON THE GROUND at a speed of NOT GREATER than 50knots".

I find the idea of deliberately closing a mixture, airborne below 3,000', stupid in the extreme - and in direct contravention of the CAA guidelines.

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[JuicyLucy]

I cannot believe that anyone still does this - it has caused umpteen accidents over the years.
The UK CAA recommend using the throttle for all simulated engine failures in the air.
I base train commercial pilots on piston twins and would never shut down a donk below 4-5000 agl.

[Noggin]

Hudson,

The UK syllabus certainly does not call for an engine failure actioned by closing the mixture control.

In order to gain an approval to conduct M/E class rating training you have to submit an Operations/Training Manual. In this, the FTO must state the method of simulating an engine failure, to ensure that the method you described is not used.

Have a look in their Training Manual to see what it says.

[Luftwaffle]

How about you do your 'simulated engine failure on takeoff' well above the ground. That's how I learned procedures for engine failure in the overshoot. If I wasn't quick or accurate enough in my control I'd crash into the "ground" at 4000'. Perhaps you could simulate the take-off by having the student do slow flight in take-off configuration, at a given altitude and then at rotation speed "climb out", following the same profile of power reduction as a takeoff. Then you can fail one ten feet above the "ground" and still have plenty of room to recover.

[Code Blue]

Luftwaffle's technique is by far the safest - read the NTSB Accident reports.

Brief for 'landing' with approach configuration and a simulated field at 4000'agl. You can even line up on a geographic feature for the 'runway' to make the student's life easier. Practice a low and over then, when clean and climbing, use throttle to simulate failure. Set zero thrust when student indicates feathering.

If I'd tried the mixture technique on a real climb out I wouldn't be posting today.

In Canada there is a requirement for a shutdown and air start for the rating. This is done within easy range of the runway at or above 3000'agl.
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edited for appalling typing

[This message has been edited by Code Blue (edited 04 February 2001).]

[Highbypass]

During all my initial multi the donks were failed using mix. It concerned me but I didn't say anything. When I did my Multi Night VFR, I was told that engine failures during CCT training were not practiced but failures EN route were. Then on my MENVFR test my ATO didn't give me a failure in the cruise but failed it just after T/O. And as the rwy in use was right on the coast, it was over water too. He actualy used throttle though. I told my instructor and he said "that might be how it's done at night".

Having said that, during my RPPL training (as it was known then) I was given an engine failure using the mixture.....in a 172!!!....at 1500' AGL!!!.....seven miles from the AD traking away!!!.... http://www.pprune.org/ubb/NonCGI/eek.gif

[This message has been edited by Highbypass (edited 05 February 2001).]

[Hudson]

Thank you for comments to date. Within Australia there appears to be no official guidance notes to flying schools on the why's and wherefores of mixture cuts to simulate engine failures on take-off, or for feathered landings. In short, you pays yer money and you takes yer chance. From experience, I would say that the majority of flying schools in Australia engaged in training on piston engine twins, use mixture cuts as the norm for simulating engine failure after take-off training. There is no record, however, of the close shaves that inevitably occur. Where accidents have occurred, unless there has been property damage or significant injuries, the air safety investigation is usually minimal - in fact safety investigators may not even attend. If it is a GA accident, shoulders are shrugged. If it is RPT - now that is different!

The CASA reply to concerns raised by an instructor about the dangers of mixture cuts immediately take off, contained some interesting observations, however.

Edited reply from CASA: "There are some risks with the procedures which you have identified. However, CASA must weigh these risks against the potential benefits of the training for overall flight safety. The risk may also be mitigated to an extent by the requirement that these procedures are carried out under strictly controlled training conditions by experienced and competent instructors.

Simulating engine failure with the mixture control. The Australian accident record does not appear to indicate that this procedure is a problem, despite it being a common practice for many years. However I am aware that the procedure is precluded by some other aviation authorities and we will investigate the reasons....with a view to to reviewing the situation in this country". End of edited quote.

In other words - Don't hold your breath, chum.

[This message has been edited by Hudson (edited 05 February 2001).]

[Noggin]

Hadn't realised you were in OZ. In the UK we practice engine failures after take-off at a sensible height before doing it close to the ground. The failure is always simulated by retarding the throttle, which after the student completes the feathering touch drill, is reset to give zero thrust.

[Highbypass]

Noggin.

Very similar here (Australia) but the safe height practice is not done with a "hard deck" in mind. It is intended for en route engine failure practice. A few normal CCTS are carried out first, then the instructor usualy demonstrates the first EFATO using Mixture. From what I can see, the mixture is used because the instructor is able to cover the mix levers by sliding a map between the right pitch controller and the left mix. Therefore the student is able to make a diagnosis in a realistic situation. ie. without acutally "SEEING" which donk has been failed. Part of the checks is to advance and retard the suspected throttle, which confirms to the student that the correct engine has been diagnosed. This would not be possible if throttle was used. But, having said all that.....is it realy worth it.....?...H. http://www.pprune.org/ubb/NonCGI/cool.gif



[This message has been edited by Highbypass (edited 06 February 2001).]

[Tinstaafl]

Lycoming, in their 'Lycoming Flyer' recommend engine failures in twins be simulated using mixture.

They state it causes much less stress on the engine by still allowing air into the cylinders to provide a more normal pressurised environment in the cylinders. This gives a different loading against the piston/conrod/bearing/mating surfaces than closing the throttle from high power settings.

I take slight issue to Hudson's comment re "...no record of the close shaves that inevitably occur...". If there is no record of these incidents, then it is only an assumption that they occurred.

The counterpoint to that argument is to say that there is no record of all the safe times that this method was used. It is only when the rate of incidents is different that one can say one method is, or is not, more risky.

I suspect that there have been incidents from closing the mixture - but I also suspect that there have been incidents from closing the throttle. Without data to compare the rate then it is only supposition to state one that one or other is more, or less, dangerous.

Personally, I suspect I've had more trouble with restoring power quickly after a period simulating an engine failure due to fouled plugs at idle than when using mixture. This has varied from a/c type to a/c type & also with temp/altitude etc. In one type it was necessary to retard the mixture to restore smooth running while the throttle was at idle. On the other hand in another it was a cow to start after being shutdown.

I would like to see a properly researched trial between the two methods. I doubt that it will happen though.

[GRpr]

In my initial multi-training, the first few ‘engine failures’ were carried out by closing the throttle; thereafter routinely by using the mixture (and the piece of paper to hide the mixture controls). EFATO using mixture cuts was carried out both between 300’ - 500’ , and above 500’. Failing between 300’ - 500’ meant that after correct identification (by ‘actually’ closing the throttle slowly - I only started to turn the aircraft into a glider once, and learnt not to rush things!), a decision to feather (by touch drill) could be made quickly, and this is what the instructor was after: no faffing about!. The mind is really focused below 500’, but taken calmly, there is ample time and the aircraft flies quite happily. Of course, it does depend on aircraft type, weight, temperature, altitude etc, but the pre-flight check of single-engine rate of climb for the day gives some idea of the likely performance when the engine quits. I think it should be borne in mind that training is rarely carried out at MTOW, but in real life that is just what we are likely to have when the engine quits after take-off. Do mixture cuts really pose that much of a problem when there is a reasonable single engine rate of climb?

In the cruise, down to 1000’ AGL, an engine was routinely (and secretively!) shut down by turning the fuel off (that troublesome five year old in the back seat!). This enabled a full sequence of vital actions to be carried out including the ‘fix’ - check of fuel pressure, fuel pump on, check - change tanks etc. From previous posts, I feel this will be viewed with horror, but I felt quite happy with it. All, in all, I became confident in dealing with the various scenarios and flying around with one engine, even when the houses were rather closer than I would have liked! It seems to be a balance between safety and realism, but I never felt at all uncomfortable.

I also had to do an engine shut-down (and subsequent air start) for my twin rating, at about 5000’ AGL. The instructor shouted “left (or right) engine on fire”, and woe betide me if the engine wasn’t shut down in seconds. I could now do this in my sleep - which is the aim of it all, I suppose.

I think I have waffled on enough, and apologies if I have digressed from the original post, but two points:

1) Landing with a feathered prop means a go-around is impractical (and therefore there is a huge added risk). I would favour the zero thrust method.

2) Why is the mixture cut method a problem? Why, precisely, do so many people view it as dangerous? Can someone enlighten me?

[Hudson]

GRPR. From the Piper PA-44-180 Seminole Information Manual - Section 10 Safety Tips Report VB-860 issued March 23 1978.

Paragraph (l): "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 of 2000rpm and 11.5 Hg MAP is recommended for simulated one engine operation". End of quote.

The first few words "Experience has shown" says it all.

Now put yourself in the Coroners Court with a cold eyed barrister asking you why you pulled the mixture which caused the aircraft to yaw badly due to slow reaction by your unfortunately maimed student now in hospital.

"Because it is good for the engine, Sir" you reply.

" Oh really, Mr Grade One Instructor - how interesting. Do you not accept the Piper recommendation at Para (l) of the PA44 Information manual that pulling the mixture etc is not worth the risk assumed?" says the barrister, who has the manual in front of him and knows he has you by the short and curly.

"No Sir, I do not accept the Piper recommendation because I am a good instructor with lots of confidence that I can get out of trouble if the student cocks up. I have done this many times, therefore it must be safe. The student just stuffed up, that's all. It wasn't my fault".


Do you get the message? I do, because I have been to a Coroners Court and I have seen a chief pilot torn to shreds by counsel for the dead. The aircraft flight manual was used to hang the instructor, and quite rightly so.

Pulling the mixture is foolhardy, and not worth the risk to your student.

[GRpr]

At the risk of appearing naieve, could someone who has posted that pulling the mixture is more dangerous than closing the throttle to idle (and there have been several), explain - in detail - why. No-one has. I am not looking for minor details - but the real warts and all danger that is going to kill me. I hope to be doing my twin instructor's rating later this year!

[Hudson]

GRpr. The fundamental reason why mixture cuts to simulate engine failure after take-off are risky, is that you have actually failed the engine. In order to restart it, the throttle has first to be closed. Then the mixture has to be moved from cut-off to rich. Finally, to restore full power you have to advance the throttle. With six levers all in a row, that is two pitch levers, two mixture levers and two throttle levers, there is a danger of confusion between instructor and student as the student carries out touch drills and the instructor resets the mixture control and throttle lever.

The possibility of confusion is reduced if only one lever (the throttle) is used. Also in event of gross mis-handling by the student resulting in the instructor hastily taking over control of the aircraft, there is instant power available from the throttle.

Make no mistake about it, if you intend to take up multi-engine training as an instructor, sooner or later you will get the fright of your life caused by gross mis-handling by a student. You may not have time to recover the situation at very low altitudes.

It is not uncommon for the student to apply full wrong rudder to prevent yaw as the engine fails. Things happen alarmingly quickly then, and you will have your hands full - especially if you have cut the mixture for "realism" and you do not have enough hands to fly the aircraft while at the same time trying to get the engine started.

When you called "Taking over control" to the student, he would have relinquished all control pressures including the rudders. As his instructor, you are now all on your own trying to salvage the critical situation of your own making.

There was a fatal accident in a Partenavia when the instructor cut the mixture at 100 ft agl after lift-off. The student was caught by surprise and the propeller windmilled. The aircraft lost airspeed and the instructor attempted to re-start the engine at the same time he took over control.

It was all too much for him and the aircraft clipped power lines 100 metres from the departure end of the runway before crashing into a house. The crew of the Partenavia survived, but the 3 people in the house died in the conflagration.

Some Regulators have banned mixture cuts at low altitude. Others such as the Australian CASA leave operational decisions to the instructor. Regarding practice feathered landings, the Royal Australian Air Force banned those 40 years ago following a spate of training accidents which wiped off several aircraft.