View Full Version : Partial loss of power

Genghis the Engineer
16th Jun 2022, 14:45
So this month we have two AAIB reports where there was a partial loss of power, leading to loss of an aircraft (one with fatalities). AAIB in the second one recommend that there's formal guidance and incorporation of partial loss of power in the PPL syllabus.



I agree, having had a few partials, and far less total loss of power events. I think it really should be a significant part of PPL training.

Whilst I would not right now advocate actually teaching the manoeuvre, I'd also advocate (see the AA5 report) that PPLs should be taught more than they are presently about the risks of attempting a turnback / impossible turn.

Thoughts from anybody else?


16th Jun 2022, 15:25
Hi Genghis

If I recall the Air Cadets came to the same conclusion operating the Vigilant (Grob 109B). Partial Power Loss After Take Off was taught and it was a good thing too. The original philosophy was to teach EFATOs but it became apparent that partial PLATOs were far more common. I suppose that was because an engine failure was thought of as being equivalent to a cable break so the same mind set prevailed.

I don’t have my old FRCs to hand but I think if you were above 400 feet or were able to attain it then flying a mini circuit was the procedure. If not then you could what power you had left to get to the best possible landing area. Of course on a instructor renewal (recat in VGS speak) it was not uncommon for the trapper to clse the throttle entirely and plan B would have to be flown sharpish! Happy days.

Genghis the Engineer
16th Jun 2022, 15:49
Interesting, particularly your suggestion that a lot of present thinking starts possibly at gliding cable breaks.


16th Jun 2022, 15:59
The risk is not in the turn, the risk is in not recognizing the conditions under which an stall will occur including accelerated stalls.
Lots of instructors treat stall training like a nuisance exercise during a lesson that will be marked “completed” rather then a dynamic exercise that should continue during the entire syllabus.

16th Jun 2022, 17:14
I was always taught as both a PPL and an Instructor that it was safer to treat a partial loss of power as a total power failure and assume nothing about the engine. Any power that does remain should be regarded as a bonus that might just get you over the hege if you misjudge things. And were the accidents the result of placing too much faith in an already dubious power source?

16th Jun 2022, 23:47
My experience has been the same as whopity and this is still the training that remains my view. EFATO is an issue that I've debated more than any other, and particularly since some loud voices have begun arguing that the turn back can/should always be considered.

The Australian study must be taken extremely seriously: zero fatalities for those landing ahead but nine for those turning back. I also believe that preparing the aircraft for a forced landing without a fire is primary; fuel off, mags off and the master off asap. If the pilot has completed all the pre-flight checks thoroughly and correctly then there can be nothing new to discover in the short highly pressured time available. All effort and concentration should then be to achieve the safest landing possible. The pilot of the report found himself distracted and overloaded with all the issues and complexities arising when it is decided to turn back.

17th Jun 2022, 00:16
I agree, having had a few partials, and far less total loss of power events. I think it really should be a significant part of PPL training.

Whilst I would not right now advocate actually teaching the manoeuvre, I'd also advocate (see the AA5 report) that PPLs should be taught more than they are presently about the risks of attempting a turnback / impossible turn.

Thoughts from anybody else?


I have never believed that the impossible turn was appropriately named. Perhaps that's because I have done many turn backs from glider tow with a simulated rope breaks at 200 ft AGL. I practiced turn-backs in my PA-28 and also used them in flight reviews in aircraft with similar performance.

When I got my FX-3 Carbon Cub I explored turn-backs in that aircraft. It was quite a shock to find the Carbon Cub needed about 200 feet more to have any chance of making a successful turn-back.

The lesson I take from this is - know your aircraft. What works in one may kill you in another. Glider 200 ft, PA-28 300 ft, FX-3 500 feet minimum altitude for turn-back if you react immediately and do it right.

Big Pistons Forever
17th Jun 2022, 01:05
The fundamental problem is the way engine failures are taught. The PFL always seems exercise starts with a sudden and total engine failure. In the real world having a perfectly running engine suddenly totally stop without warning is the least likely scenario. You are much more likely to either have a rough running engine or a partial loss of power, or some warning the engine will fail soon if you are paying attention.

IMO the cause check is the most neglected part of force landing training. At least 2/3rds of all power losses are directly caused by the actions or inactions of the pilot. Making sure all students has an organized procedure to restore power would IMO significantly reduce the number of wrecked airplanes. Unfortunately the restoration of power is usually glossed over because you get all the points for flying the power off forced landing procedure. This is negative training because the student knows they will never get power back when the instructor pulls back the throttle and so they just do a quick mumble through the checks and then concentrate on flying the airplane

When I teach the forced landing exercise I always do a couple as partial power exercises. The first I will pull the power back to just enough to maintain level flight at a safe airspeed. After the cause check this then becomes a pilot decision making exercise. I deliberately set it up that so the airplane can safely return to base with a route that will always ensure a suitable field is in range. The next one will be a power reduction below the power required for level flight. Again after the cause check the pilot decision making becomes how do I use the residual power to improve the odds for the forced approach.

17th Jun 2022, 12:04
Completely agree. Here in the UK there is a resistance to scenario training. Whenever I've sought to introduce the idea I'm met with what you may describe as passive aggression - silence. The universal tradition is one of handling skill training. Do as I say and "you will always be safe": the Australian data seems to bear this out e.g. for the landing ahead following EFATO and, as you mention it, forced landings en route (I don't have figures to hand). My background is that there is no such thing as a partial engine failure to consider. the 'partial bit' is a phase on the way to a total. Particularly for EFATO a partial should not be a consideration - don't believe it: 'mermaid on the rocks' so shut the engine down and concentrate on a safe landing

Before we can introduce turn back training we must first accept that it is realistic. We are a long way from this, I can't see it fitting in to a basic training concept because it requires complex decision making (i.e. scenario training) in addition to simple handling skills.

Big Pistons Forever
17th Jun 2022, 17:49
I think an element of the problem is what constitutes an “engine failure”. Obviously if the engine stops producing any power it has failed. But what if it is producing power but running rough, or running but at reduced power, or running but occasionally stumbling. I have had all three scenarios happen to me, but have never had a engine totally fail in a SEP.

I don’t see much of any discussion of these scenarios in flight training, yet IMO they are much more likely to be experienced by the average GA pilot than a sudden total engine failure. For example if the engine is occasionally stumbling I don’t think the pilot should immediately close the throttle and land on what ever field is in gliding distance. They should certainly plan for the engine to fail at any time but that will still often allow them to still safety divert to the nearest airport.

18th Jun 2022, 07:20
I've stolen Genghis' pre-takeoff brief (hope you don't mind!) that the student (and PPL on check) read out to me.'This is my take-off' etc, then the bit about 'if there is a problem on the ground, I will pull everything back and stop ahead'.' That could be ANY kind of problem and we discuss as many of the different types of problem you might have, from external issues, deer on the runway to internal, airspeed not as expected to oil on the windscreen. The next bit says 'if there is a problem in the air I will land ahead, turning no more than 30 deg either side of the centreline'.
There's NO WAY I'm teaching students to try and turn back - they lack the skills to make it work. I had a good friend and instructor who had 2 EFATOs. The 2nd was in his own Jodel and was a partial. He describes the 60 deg AOB turn he made at 500' and just scraped a downwind landing on the airfield. Any lesser pilot wouldn't have made it. I've tried turnbacks myself at various heights in a Cessna150 and at 45 deg AOB it only worked above 500'.

When I first start the long brief about PFLs we discuss the partial case, then practice it before moving on to the sudden, catastrophic failure. The question I ask is 'what is the first sign of partial engine failure?' The answer of course is a loss of altitude. You notice you've lost 500' and it's only when you go to apply more power you find out you can't. We then discuss options - 'land at the nearest suitable airfield'. One of the scenarios we discuss for the sudden total loss is your pax, wonders 'what's this big red knob for?' and is too embarrassed to admit they've pulled it back. Another is a recent AAIB report where the pilot admitted knocking off the mags with his knee. So, yes, the 'reason for failure' drills are very important. I teach work across the cockpit, touching each element as you go.Then it doesn't matter what type you are flying, you should cover all the essentials.

I've had one partial, on a go-around from a practice baulked landing. The throttle stuck at 2,000 RPM and wouldn't move either way. Fortunately, the pilot being checked out was very skilled so he flew while I analysed and planned. We had about 100' steady height and about 5kt above the stall. The plan was to fly a very careful circuit, then chop the mags on short final. As it happened, a massive tug on the throttle over the threshold released the corroded mechanism and we landed normally.

One last thing - below 1,000' AGL and not having restored normal power, if you've chosen a landing site don't even consider using the engine again, shut it down. That sudden burst of power on short final might just carry you into the housing estate instead of your nice short grass level field.


18th Jun 2022, 07:47
I've stolen Genghis' pre-takeoff brief

Any chance of re-posting or pointing to where it can be found?

Big Pistons Forever
18th Jun 2022, 16:42
Re pre-takeoff brief: My brief for students is the same. The only difference is I emphasized that the first action if power is reduced or loss is to immediately lower the nose to the gliding attitude. While verbally delivering the brief I get the student to physically push the wheel/stick forward so as to reinforce the muscle memory. Sadly there have been numerous EFATO accidents where the pilot froze did not lower the nose and the airplane stalled.

18th Jun 2022, 18:42
I've tried turnbacks myself at various heights in a Cessna150 and at 45 deg AOB it only worked above 500'.

What airspeed did you use in the turn? I find it surprising that a C-150 would need so much more altitude than a PA-28-180 or AA-5A.

18th Jun 2022, 23:26
Try flying at min. sink speed (roughly 75% of range speed) with partial power, rather than 'normal' gliding speed? You might just be able to maintain height with reduced power? That was certainly the experience of a colleague whose AA-5A lost power a while ago.....

EASA is proposing to mandate partial power training - and very wise too!

Genghis the Engineer
19th Jun 2022, 00:47
I've stolen Genghis' pre-takeoff brief

Any chance of re-posting or pointing to where it can be found?

I don't remember where I posted it either, but it's generally along these lines.

"This will be my take-off on runway 24. I will rotate at A knots, aim to establish a climb at B knots, and raise the flaps once I have a positive rate of climb confirmed from at least two sources. In the event of a problem on the runway, I'll pull everything back and stop on the runway. In the event of an engine failure after take-off, I'll be establishing C knots, and landing ahead turning no more than 30° left or right (at specific airfields I may describe the direction I actually would take). Should we make an emergency landing at any point in the flight, please do [type specific actions] then once all the bits have stopped moving, get out, go sideways away from the aircraft and don't come back unless it's clearly safe to do so AND you're coming to rescue me. If anything concerns you about the safety of the flight at any time, including other aircraft you don't think that I've seen, please tell me immediately and clearly."

In a multi-engine, obviously add in reference to Vyse. With retractable gear, also when that will be raised.

Mine's always out loud if there's anybody else in the aeroplane, perhaps a bit more dumbed down if everybody else is a non-pilot, perhaps a but quicker and less clear (but probably still out loud) if I'm flying solo. I ask my students to do something similar before entering the runway.


Genghis the Engineer
19th Jun 2022, 00:51
I've stolen Genghis' pre-takeoff brief (hope you don't mind!)

On the contrary, absolutely delighted.


19th Jun 2022, 10:46
For what it's worth:

About 22 years ago, I was climbing through 3000 in a 152 out of Lydd, with a student on his second or third lesson. He was also one of my first students. Very suddenly, when almost 4 miles from the field, the power reduced to 1850/1900rpm despite a wide open throttle. Since I had control at the time, I lowered the nose and turned towards the field, re-assuring the student that we could easily glide to the field whatever happened. No adjustment of anything gained me anymore rpm. An easy controlled descent to a tight base join got us in without any issue. Once parked, accompanied by the rescue boys, we got the engineer out. One of the two plain bearings (bronze I think) in the alternator had partially seized and, because the alternator belt has to go round the large circumference of the starter ring, it had become an engine brake!

I often simulate this when conducting LPCs and LSTs.

19th Jun 2022, 21:43
Any power setting above endurance RPM might keep you airborne or climb, all be it say 100fpm. Time to make gentle turn back to circuit or alternate runway. Had to do it a few times because of cracked cylinders. I had a dropped valve, put that one down in a field. Another partial power from 5000 feet managed to get back to airfield on 2100 rpm maximum i could get..that was a carb. flooding fault.

Dan Winterland
20th Jun 2022, 12:47
In the Training Com of Autumn 2019, the CAA gave instructors guidance on what to include in the Refresher Flight Training for the revalidation of the SEP rating TrainingComUpdateAutumn2019(CAP1860).pdf (caa.co.uk) (https://publicapps.caa.co.uk/docs/33/TrainingComUpdateAutumn2019(CAP1860).pdf) They quote CASA data that a partial failure it three times more likely that a complete failure https://www.atsb.gov.au/publications/2010/avoidable-3-ar-2010-055 and suggest this is covered in the RFT. And in my experience of two engine failures in single engine aircraft both being partial, confirms this to me. I have always included the partial failure in PPL instruction training and I make all the simulated failures for my currently/revalidations partial ones. I get interesting responses, even if they were pre-briefed. Most PPLs haven't been trained for this, only knowing the complete failure scenario and most haven't even considered it having being only exposed to any engine problem leading to a PFL. Mandatory inclusion of this in the syllabus is long overdue in my opinion.

20th Jun 2022, 22:29
The current training emphasis is that we should not mess about trying to make a dog's dinner into an unlikely successful outcome. Better to make full use of your height and time identifying a safe place to land and planning how to do so. An engine giving some power will help to maintain height or at least flatten the descent so extending the time available to plan and provide more options. Having identified the landing place then commit to that and carry out the plan.

The syllabus doesn't state at this point that the aircraft should be shut down but rather thorough and comprehensive checks are to be undertaken with the plan underway. So, if you discover that the: mags are switched off by knees, your passenger has pulled out the mixture control or the fuel selector is miss-aligned then obviously correct things. Having corrected these unambiguous faults and the engine now runs as normal then continue with your plan while still checking that things are indeed good before going on your way. If the recovery is temporary then you will still be in your plan to land. Should you be forced to land statistics are that the outcome will be good. The aircraft may be wrecked on landing but the pilot and passengers will likely survive.

Messing about without a plan in the hope that you will find an obvious fault but continuing to lose height or by leaving behind a good landing with the wind now against you surely doesn't make sense. The statistics for this idea are not good.