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Engine Failure

Old 15th Aug 2010, 22:20
  #141 (permalink)  
 
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If you are flying over somewhere with tons of fields that all look alike (like S UK) and you are not particularly high, you can set yourself up for a long base and at the right altitude, turn final.
The East Anglia technique.

As taught by instructors in East Anglia ... but they, and examiners, get all precious if you fly PFLs that way, they seem to insist on being told which field you're going for long before you get to 500'.
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Old 16th Aug 2010, 06:12
  #142 (permalink)  

 
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The motor won't stop turning all the time you are flying well above Vs. Too much airflow
Yes good point thanks for reminding me, I should have thought about that. Worth remembering so that if the prop stops, don't bother wasting time with fuel tanks etc...

The usual restart procedure on a twin is to unfeather and let the wind flow windmill the prop to restart....or in a DA42, just switch the engine master back on
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Old 16th Aug 2010, 07:16
  #143 (permalink)  
 
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Does anyone think Mr Guppy has run into problems with the small arms fire? I do hope not.
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Old 16th Aug 2010, 08:14
  #144 (permalink)  
 
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Fuji the deisel engine as you more than likely know uses compression to ignite the mixture so no spark plugs.

The additional speed required is nothing to do with the internal friction of the beast which will be the same as a petrol.

It just requires more oomf to get it chuging away again. Its the same with bump starting cars drop the clutch on a deisel and its like hitting a wall as you fight against the compression. On a petrol you will get it going through a couple of compression cycles then it will fire up. Good thing about a deisel is that it usually goes when your through the first compression so you can start them in under a meter with the applance of brute force and sweat.

I have never flown one of these deisel suck squeeze bang blows but years driving lorrys etc I suspect thats the reason
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Old 17th Aug 2010, 01:27
  #145 (permalink)  
 
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I do not think flight schools do pilots a favour by teaching "cookbook" forced approach procedures ( ie apply one part glide angle with a half part of bank wait precisely 30 sec, perform a complicated mental calculation and then turn for another half part etc etc ). This works great as long as there is no wind, you are expecting the failure, you know the height of the terrain, the engine has infact totally failed and is not producing some residual thrust etc etc.

IMO the key to sucess in a for real forced landing is having the skill to be able to judge the gliding flight path and adjust it as required to get to the desired touchdown point. As long as the aircraft touches down in a wings level level flight attitude on a piece of reasonably flat ground, the chance of everyone walking away is very high. The length of that piece is not really that important. Your typical Cessna/Piper is designed so that the seats, seatbelts, and cabin structure will withstand a 9 Gee deacceleration. Assuming a steady rate of deacceleration (an over symplification I acknowledge) then it will need about 25 feet to go from 60 kts to stopped. Fatal accidents arising from engine failures usually result from gross mishandling resulting in a low altitude stall/spin or hitting a solid object at flying speed due to an inabilty to judge the aircraft flight path. IMO the most usefull exercise to prepare for a engine failure is to fly a circuit and when abeam the runway end close the throttle and manage the glide so that the aircraft touches down in the first 300 feet of the the runway.

But the bottom line for engine failures is in the accident statistics. At least 80% of all engine failures are a direct result of the actions or inactions of the pilot. So if you are standing next to the undamaged aircraft sitting in the field after the engine failed, you can congratulate yourself on your piloting skills......but there is a 4 out 5 chance that the reason the engine stopped in the first place was because you were stupid....
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Old 17th Aug 2010, 06:54
  #146 (permalink)  
 
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I think most people who fly different kinds of approaches to a normal runway (not just a standard circuit but straight-in, with shallow or very steep glideslopes, tight base approaches, etc) should be able to pull off an acceptable field landing.
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Old 17th Aug 2010, 14:53
  #147 (permalink)  
 
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Statistics can be interesting when offered to support a belief system.

At least 80% of all engine failures are a direct result of the actions or inactions of the pilot.
Thinking back on my career I can recall having at least eight engine failures, non of which would fall into the above statistic.

Two were fuel controller failures on PT6's.

Three were catastrophic break up of the engine on P&W 1830's.

Three were fuel lines becoming blocked resulting in engines quitting........in one case I lost both engines on a Navajo IFR at night and lucked in by finding a hole in the cloud deck with an airport in sight, allowing me to land on a runway and wait to get towed to a hangar.

I have had to do several other precautionary engine shut downs due to problems such as failed cylinders etc. to prevent the engines from possibly failing due to metal contamination from the failed cylinders.

Try as I may I can not recall ever having an engine failure that resulted in an emergency landing due to my inaction's or lack thereof.

So would the above experiences be worthy of starting another statistics record to quote?

Or was I just lucky?
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Old 17th Aug 2010, 15:00
  #148 (permalink)  
 
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More than likely, Chuck, your experience is the result of flying a huge number of hours but, through being a good pilot, you have not made any c0ckups, so your engine failures were caused by factors beyond your control.

The average UK PPL flies ~ 30hrs/year. Setting aside the fact that most of them pack it in for good within a year or two, those that remain for the long term probably accumulate below 1000hrs before they give up (due to old age / loss of medical etc). The long-time pilots I know are in that category, with 1 or 2 in the 2000hr range.

With such low hours being flown, I would not expect PPLs to see a lot of engine failures, in certified engines whose MTBF is believed to be of the order of 50k hrs.
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Old 17th Aug 2010, 15:38
  #149 (permalink)  
 
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I0540, what I was questioning is the use of statistics to back up a belief system without any reference to where said statistics were found and the accuracy of same.

Looking at this from another angle if statistics are to be believed then why do a lot of pilots fall outside of said statistics?

Based on the numbers presented in the quote I posted then I should have had at least 64 other engine failures caused by lack of attention to what I was doing......but I can't even recall one, so what real value is there in using statistics to support a belief system without having a statistic for those who fall outside of the statistic used?

I do not want to start a big argument here I am only pointing out another side of this discussion.

It is allowable for anyone to question these issues is it not?
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Old 17th Aug 2010, 15:40
  #150 (permalink)  
 
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Chuck

The PT6 has a mean time between failures of less than 1 failure for every 100,000 hrs flown. If you have had 2 failures of this type of engine than my thought is the engines were not properly maintained. An engine failure because the engine is not properly looked after IMO falls into the preventable enginr failure catagory. As for your comment regarding engine failures in large radial engines...... well I have also shut down big piston engines on numerous occasions due to internal mechanical failures but than it is a different case when you have three other engines still runnning and perfectly able to get you home However since this is the private aircraft forum I took it as a given that readers would understand that the 80% statistic applies to light aircraft accidents.

However you are correct in that I was insufficently precise in defining where the statistic came from. I got the 80% statistic from Richard Collins (the former editor of flying magazine). He arrived at the statistic after an extensive study of the light aircraftaccident database in the USA. To be counted in the 80% an aircraft had to have suffered an engine failure and either made an off airfield landing or sustained major damage at touchdown at an airport (mostly EFATO's). Unsurprisingly fuel exhaustion and mismanagement were the most common cause of engine failures and was in virtually every case 100% preventable. Carb ice which had been allowed to develop untill the engine stopped was also a leading cause of light aircraft engine failures. Also included were engines that failed due to a mechanical malfunction but where the fault was evident on the ground and yet the pilot took off anyway. The bottom line was that the majority of engine failures could have been prevented by the pilot.

It would seem that the least likely scenario for an engine failure in a typical Cessna/Piper light trainer/tourer would be where the a properly maintained engine that had a normal runup, has sufficent uncontaminated fuel, is not icing up and shows normal engine guage indications......suddenly and without warning suffers a total failure. Or in other words the common flight training scenario. This does not mean that the forced approach procedure should not be taught and practiced, just that this scenario is only one possibility among many others and that IMO the best defense against the engine failure emergency is to mimimize the probability of the engine failing in the first place by conducting good runups, carry extra fuel, be vigilient about the formation of carb ice etc etc.
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Old 17th Aug 2010, 15:53
  #151 (permalink)  
 
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The PT6 has a mean time between failures of less than 1 failure for every 100,000 hrs flown. If you have had 2 failures of this type of engine than my thought is the engines were not properly maintained. An engine failure because the engine is not properly looked after IMO falls into the preventable enginr failure catagory.
Once again we have statistics that only point out an average.

Both of my engine failures on the PT6's had nothing to do with not being properly looked after.

Here again is why they failed.


Two were fuel controller failures on PT6's.
The engines were PT6-20's.

The company I was flying for had a lot of these engines in their Twin Otters and their Turbine Goose's.

Mind you that was some years ago though and it is possible you were not flying for a living then so you may not be familiar with the problems we had with fuel controllers then, in those engines.
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Old 17th Aug 2010, 15:55
  #152 (permalink)  
 
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why do a lot of pilots fall outside of said statistics?
If one sticks to certified engines, I think it must be down to the broad spectrum of "maintenance" (quotes fully intended) standards in GA.

Also, it is natural for rare events to show clustering, so finding one pilot who has had several is to be expected.
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Old 17th Aug 2010, 16:12
  #153 (permalink)  
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I'm with Chuck on the PT6 issue. Excellent engines, but not perfect, neither is P&W. My total flying of PT6's (-27, and -28) is about 120 hours. During that time, I personally shut one down preventatively, when the fuel control unit failed within 10 hours after a P&W repair/overhaul (I don't know which). This maintenance had been required because the same engine had been overtemped because the previous FCU had failed weeks earlier. Pilot action/inaction had not at all been a factor in the failure in either case.

Not statistics, just my experience.
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Old 17th Aug 2010, 16:22
  #154 (permalink)  
 
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Interesting thread. Well, it just happens I've been done quite a few PFL's in the past 3 weeks as part of my PPL revalidation (I passed the check!). For what they're worth, here are my thoughts:

1. In this part of the world, many fields are of the tennis court sized variety (definitely not East Anglian sized prairie!) with big stone walls round the boundaries, often with a diagonal or side slope and a hummocky surface as well. This somewhat limits your choice of landing site. I accept that once the aircraft is on the ground, the deceleration is going to be quite rapid on the rough ground, but I would prefer it wasn't caused by a block of granite. So, a search for a reasonably long flattish field is always a good idea. Of course I accept that in a real forced landing you may not have this luxury.

2. Long straight-in glide approaches are hard to get right, even with a slip or S-turns. The "high key, low key" method, with a tight base leg is much better. The aspect of the base leg can be varied to lose height if you are too high, ie too high, then turn away from the field sufficient to lose height. If you are really high, by all means orbit on base leg.

This is invariably the way I practice glide approaches when landing at my home airfield, and it works every time.

3. By all means slip the a/c to lose height on final, but be careful with the flap limiting speed. On one PFL I had flap 40 selected on a C172, tried a quite aggresive slip and quickly found the speed was 10 kts above the flap limiting speed -quickly corrected before the instructor noticed! In fact accurate speed control is vital to the exercise - try diving for the field in this part of the world and you will end up building up excess speed and probably going into the stone wall at the far end.

4. Most engine failures are caused by carb.heat or fuel problems so your first actions after pitching for best glide speed should always be to pull the carb heat knob and check/switch the fuel selector, and switch on the electric fuel pump if one is fitted. Fly the aircraft right down to the ground, send a mayday and don't bother with the transponder.

5. In most of my practice PFL's, being too high was far more common than being too low.

6. Try and pick a field that roughly aligns with the into-wind direction. Be aware of the wind strength and direction at all times, especially when turning from base onto final.
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Old 17th Aug 2010, 16:49
  #155 (permalink)  
 
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I think we are going over old ground.

First and foremost Mr Guppy is correct – engines do fail, and just because the statistics predict an engine will fail every 2,000 hours or whatever doesn’t mean that your particular failure will not be in the first 50 hours and you will not have a second failure in the next 5 hours. Obvious, I think we would all agree.

However, the stats do suggest that engine failures are rare, and become a great deal rarer if they are not pilot or mechanic induced in some way.

The FAA have produced stats that I believe are reasonably reliable and on which I base this statement. However, I recognise that far from all engine failures are reported so inevitably the stats are only as good as the reliability of the raw data.

I also agree with IO540’s point in that with any statistical analysis there will be hot spots. We all know there are aircraft that for one reason or another suffer higher engine failure rates than others. Dare I say there are also pilots who seem predisposed to engine failures!

How we cope with an engine failure is down to luck and skill – an issue on which I know I and Mr Guppy will part company. I agree with the recent poster – fly anytime soon over parts of Devon and Cornwall and with all the skill in the world you will do very well indeed to stop before a dry stone wall does the stopping for you. How well the landing turns out will probably depend on how hard the stone wall is and how quickly it does the job for you!

The reality is many pilots fly very few hours a year. They are struggling to remain substantially competent never mind being forced landing Sky Gods. I gave an analogy previously about sailing because I felt it was relevant. Yachties are no different – the majority would struggle to do a reasonable job of recovering a MOB simply because they do not sail enough. The RYA recognised this problem some while back so we teach a method of recovery which gives the most ham fisted of skippers the best chance of recovering the person. In the same way pilots who don’t fly many hours a year must either spend all the time they are flying rehearsing FLs, give up flying, or use a technique which gives them the best chance of a successful FLing.

You may feel my point of view is complacent, but I think it is realistic because for many if they spend their whole time worrying about the engines failing, where and how they were going to land, not only would they give up flying, but they would probably may a mess of all the other equally important management tasks like changing tanks so the engine doesn’t run out of fuel due to fuel starvation.

For those who fly more often by all means stake your claim as a Sky God – spend more time rehearsing these skills and developing the best possible technique and you may increase your chances of success should the worst happen.

For the rest of us operate a Cirrus whenever you can; I shall be pulling the chute so hopefully it is pretty much academic.
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Old 17th Aug 2010, 16:59
  #156 (permalink)  
 
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For those who fly more often by all means stake your claim as a Sky God – s.
What is a Sky God?
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Old 17th Aug 2010, 17:01
  #157 (permalink)  
 
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If one is going to compare statistics than you have to compare comparable numbers.

With respect to the PT6, all of the failures mentioned above would not have been counted in the 80% figure because

1) they were not in light aircraft (FAA definition is less than 6000lbs GTOW)

2) they did not result in an off airport landing or a crashed aircraft

Like most statistics the experience of one particular indivdual is likely to vary from the average of a large group. I pointed out this particular statistic (80% of all light aircraft engine failure accidents were caused by the actions/inactions of the pilot) because it reflects the facts of a large number of actual aircraft accidents over many years. How any particular pilot chooses to use this statistic.... or not, is of course up to them. I posted the information because my experience has been that most PPL's are not aware of the accident statistics and may find the information usefull.

Chuck:

in an earlier post you posted that you had a double engine failure in a Piper Navajo, due to the fuel lines being blocked. What casued the blockage ?
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Old 17th Aug 2010, 17:16
  #158 (permalink)  
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For the rest of us operate a Cirrus whenever you can; I shall be pulling the chute so hopefully it is pretty much academic
Is deploying the parachute in the case of an engine failure in a Cirrus a recommended procedure? The Cirrus SR20 flight manual I have does not leave me with that impression, indeed, somewhat to the contrary...

As the manual refers to "expected ... loss of the airframe" in the case of parachute deployment, is it appropriate to turn a possibly good forced landing into a lost airframe situation?

Would not deploying a parachute attached to an otherwise flyable aircraft make it much more difficult to guide it to a suitable touchdown area? At the very least, in a populated place, does not the pilot maintain the moral responsibility to guide the the striken aircraft to an area where the least possible injury and damage to those on the ground, would be the result?
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Old 17th Aug 2010, 18:39
  #159 (permalink)  
 
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Looking at this from another angle if statistics are to be believed then why do a lot of pilots fall outside of said statistics?
Almost certainly because the sample sizes are too low.
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Old 17th Aug 2010, 19:38
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Looking at this from another angle if statistics are to be believed then why do a lot of pilots fall outside of said statistics?
The usual error of trying to draw conclusions from statistics using only mean values. One needs higher order moments as well in order to draw any kind of meaningful conclusions from the data itself (at the very least some variance measurement). If one were to do that, I guess one would find that the variation among pilots is so high that the mean values are quite pointless.

The other big problem is that the sample sizes are too large. People try to create large sample sizes by grouping together all sorts of pilots undertaking all sorts of operations in some belief that large sample sizes make the statistics better. What one ends up with is a fairly accurate value of something nobody is interested in measuring. If I want to know, say, my probabilities of having an engine failure, I want a sample consisting of pilots similar to me doing similar things in similar planes. The proper sample size is one individual, and the result will not be available until my career is over!

The third rather obvious point is that engine failures are not random events. An engine fails for a reason. If one has a perfectly good, healthy engine that is handled properly, the chances of it failing is close to zero. If there is a fatigue crack in a rod with a remaining life of some 3000 cycles, the chances of the engine failing in the next five minutes is about 100%. Since one does not know if one belongs to the former or the latter cathegory, one fundamentally has no idea of the probability of having an engine failure during that flight. Statistics is useful for all sorts of things, but not for making predictions of individual events.
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