Helis, I gather from a heli pilot I know, suffer a lot more because the engines are worked very hard but get inadequate cooling air.

OTOH they can land with autorotation almost anywhere.

And helis have hundreds of life-critical parts.

Indeed, and that is what saved them both, despite the non-ideal landing sites.

High Key and Low Key
 

Jan Olieslagers

As to "High Key" and "Low Key"

I've had the privilege and honor in my life to both fly civilian and military. In my early civilian flying days when being taught the emergency procedure for engine failure it was always....Land in a field. More of a TLAR (that looks about right) approach. Now yes you pitched for the best glide and basically picked out a field and orbited above it until you landed. That that sounds like a good plan, but where exactly should you be in that orbit above the field?

In military training I've learn a specific ELP(Emergency Landing pattern).Think of "High Key" as and an actual point you fly through in the sky. Like a huge ring in the sky that you are trying to fly through directly abeam your intended point of landing. If you're in the right seat that would be to the left of your intended point of landing if in the left seat to the right of the intended point of landing. This way you can always keep in sight where you're landing. Now this may be different for every aircraft, but what worked great for the C-172 at 2200lbs is 2,000'

"Low Key" is like a base leg to final, which is approximately 1000' feet for a C-172 at 2200lbs.

You are then looking to be approximately 500' rolling out on final and then you S turn or slip the aircraft to lose any extra altitude if you have any.

The issue with TLAR and just orbiting over the field is what if you're too high or what if you're too low? Will you know if you are? If there are 150' trees you have to miss (which I had) will you make it?

Knowing exactly where to be and what altitude to be at will let you know that you're on a good glide profile and will help increase your chances for a safe landing.

Here is a blank ELP (emergency landing pattern) diagram. I recommend taking what ever aircraft you will be flying and climb up above your home airport to about 4,000' AGL and orbit at best glide to see what your actual numbers will be for an entire 360 orbit and then add a bit of altitude to that for safe measure. This will be your "High key" and "Low Key" numbers.

http://www.tpub.com/content/aviation...wch50154im.jpg

Hope this helps.

God bless,
Tony<><

P.S. 4 days after my engine failure my wife and I found out we are going to be parents!!!! Super excited!!!

englishal,

1) I believe the FAA ruled it as carb ice....I'm still learning, but I just don't understand yet how you could get carb ice at 2400RPM in a climb at 3800'.

2) As to the beautiful girl. She was a friend in town and had never been up in a small aircraft before. Needless to say she wouldn't go up after that. However, her husband was ready to go up that night and wants to be a military aviator.

God bless,
Tony<><

Presumably you fell on top of her some time during the landing...

Tony,
Thanks for the extensive description - and congratulations with your upcoming parentship!
I think I understand your explanation, and will certainly try to take the exercise whenever I can again afford to go flying.
One thing still unclear, though: all the altitudes you describe are indeed altitudes, they are read on the altimeter. However we need to know heights AGL - but in an out landing we can only estimate the elevation.

Thanks Tony, good job :ok:

As to the exact AGL altitudes you're correct in saying that this is what they are and what you need. However, when flying anywhere in the world you should always know the elevation of what's below you. You are correct in using your altimeter, which means you'll have to do some public math to change MSL to AGL. A great tool to help is a VFR chart. You can always look at a airport near you and get the elevation of that airport. You can also find a tower on the VFR chart and subtract the Height above the ground from the Height in MSL and this will give you the elevation. Hence public math yet again. This is where your altitude plays a huge key. If you are low on altitude channelizing your attention on things like this has caused a lot of accidents. I feel like what helped save our lives was after analyzing the problem and not being able to remedy the situation I then shifted my focus to saving my crew. My mind shifted to how can I get this aircraft on the ground safely. Mosts part of the country don't change in altitude drastically over a small distance. Not including mountainous terrain. A GPS is also a great tool the Garmin 430 will tell you the elevation of locations near you. I hope this helps.

God bless,
Tony<><

IMHO, I don't think the above is practical.

Upon an engine failure in a SE, one is going to get awfully busy awfully quickly - unless at FL150 above Lydd :) You will pick a provisional course of action, then set 7700, make a radio call, then - unless you have a conrod sticking up through the cowling - try to sort out what caused the failure (electric fuel pump ON, etc).

There are basically two approaches: one is to orbit until at what appears to be the right height / aspect ratio and then fly the part-circuit to land, and the other is to turn into the wind, pick a site straight ahead, and try to put the plane down in a field there.

The advantage of the former one is that you get a better chance to inspect it before you go in.

The advantage of the latter one is that anybody can do it - well anybody who can fly a long final, perhaps a very steep long final, with s-turns to lose height.

I think I would go for the latter method, if there were fields all over the place (which is the case most of the time when over the UK and most other "flat" places) and the rest of the time one would have to be more imaginative...

I dont necessarily disagree with you (especially if already on glideslope on an into wind final towards the proverbial billiard table) but my instructor always maintained that the best initial manoeuvre was to turn downwind since you covered more ground which gave you an increased number of landing alternatives. Of course every case will be different depending on what is below you and its relative bearing to the aircraft and the wind, but I suspect that if the fateful day ever came, my natural inclination would be to "hug" any good looking field and go for the spiral descent option.

Reverting to my long distant gliding training I NEVER lose sight of the field I have chosen. Having turned downwind, as I too was trained to do, I choose a field and then, if necessary, do S turns up and down the downwind leg until going downwind at 1000' and level with the touchdown point. (Low point?).

Orbiting could lead to losing sight of the field. Straight in approaches sound extremely dangerous to me unless you know the field and you KNOW that you are have height in hand. You ever see a glider pilot doing either of these things?

Straight in is OK if you can see a sequence of green fields lined up "vertically" ahead of you.

Anybody can glide on an azimuth; it is judging the glide distance which is hard.

I think that at least 90% of the time (UK) one would meet the requirement.

Io you are right about getting busy.
Real engine falures are nothing like PFL's.
With the engine quiet and the prop stopped its nothing like coming down with the prop windmilling.
From the average height of a cross country in this country ( allegedly 2500ft) there is precious little time to get down safely.The only time I bent the plane was the only time I tried to put out a may day.
I tried to retune the radio and in my haste overshot the frequency, by the time I had retuned and put out the mayday, and then concentrated what was going on outside the window I was down to 500ft( approx) which just about gave me time to brief my son for the impact and take what was in front of me.
My ONLY advice to anyone faced with an engine failure is forget everything else and FLY THE BLOODY PLANE.
A friend of mine had an engine failure and trashed the plane and nearly killed his passenger.His comment to me after the accident was that he had remenbered to do everything "by the book" and was proud of that and the only bit that went wrong was the last few minutes!THEY ARE WHAT COUNT!!

The glide ratio with a stopped prop is better than with a windmilling prop, BTW.

At least with a stopped prop you know the engine is f*&^%$d and don't need to waste any time on restarting it.

In the southern UK I assume that all the ground below me is 500' MSL unless I know otherwise! If I were to come in high, it is easy enough to shed a few 00 feet. If I am low.....oops. But one instructor used to teach me the long base, short final technique. 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.
Fuel?

The motor won't stop turning all the time you are flying well above Vs. Too much airflow.

To stop an engine (that is not mechanically broken) you have to pitch up aggressively (maybe 30 degrees up) and switch off the ignition / close the mixture.

I was in a C150 with an instructor who did it for fun. I also know somebody who flew with the same instructor who did it at 2000ft :)

IMHO if an engine stops turning, in any kind of normal flight, it is gone.

englishal, I think IO540 meant that if the engine stops turning and the airspeed is normal (so there is persistant and adequate airflow over the prop blades), there must be something terribly wrong with the engine, i.e. mechanical damage (and not lack of fuel, spark or air) and its restart and further operation is likely to be beyond pilot's capabilities to do so from the cockpit.

For general purposes, it is correct that if the propeller (metal) has stopped turning through no action of the pilot to stop it, don't concentrate on a restart, look for a place to land. I have stopped my C150 prop, but it was not easy. If metal has come adrift inside the engine, the starter is not going to be of any use!

That said, while doing un-feathering/restart evaulations of the Lycoming engine with the MT prop, in the DA 42 L360, I can tell you, that it was fairly easy to stop the prop (feathered or not), and un feathering did not cause it to windmill. A high speed dive did get it windmilling. Similarly, my evaluation of a Hoffmann 4 blade wood prop on the Scout suggested similar characteristics. On such installations, if I had let the engine stop, and thought that I had corrected the problem, I would be trying a restart.

A clip for you (and yes, I know it is feathered), but even with the outboard portions of the blades with a very favourable angle of incidence to encourage a windmill start, it was not a sure thing. The starter motor method worked very well!

Jims DAR Testing :: DA 42 L360 restart video by PilotDAR - Photobucket

With the popularity of the MT props (which is well desreved, in my opinion), it may more be the case where a stopped engine is worthy of an attempt to restart by starter motor.

As for setting up a gliding circuit, my practice, particularly after reading John Farley's excellent book, is to tend toward picking a landing sight nearer, and more straight ahead, and if possible flying a high, straight in approach, with lots of drag. I would much rather concentrate on configuration, drag management (side slipping), and glide path control, knowing I have good reserve, than to try to fly the perfectly configured glide, with half the circuit worried if I will really make the landing sight.

I do realize that this may conflict with convention methods, and I do not seek to challenge those time tested thecniques, but it works for me!

"Once you get away from the certified engine scene, there is a huge variation in engine reliability."

May add my few pence worth? I've clocked up almost 1200 hrs in the last 19 years, all bar an hour or so in the same flexwing I learned to fly in (which is possibly a record in itself?). The only time the engine has stopped in flight is on the few occasions when I have turned it off.

I have experienced 2 instances of fuel starvation, due on both occasions to water condensation mixing with the oil in the fuel (50:1 premix for the Rotax 447) and partially blocking the fuel filter. The first time was during my GFT, and we managed to limp back to the airfield. The second time I happened to be passing a suitable strip, and immediately turned round and landed safely.

More recently I have suffered several misfires during climbout - on all occasions the engine recovered after throttling back. This took me some time to resolve, and eventually turned out to be the original engine wiring harness. Since replacing, it's run perfectly.

When I hear the experiences of some other pilots who regard engine failures as a regular occurrence, I have to wonder why... Maybe years of motorcycling taught me to take care of 2 strokes? I only use good branded Mogas from the same garage, and buy my oil in bulk. I don't take off without allowing the CHT to reach 200F, and I never throttle right back on approach until I'm assured of a landing - no fuel = no oil... My machine has a simple permanent warm air induction system which seems to be enough to prevent carb ice from forming, without noticeably affecting performance, another reason for keeping some power on during descent.

This goes against how I was taught, but I'm of the opinion that glide approaches are asking for trouble on older 2 stroke powered machines like mine. I do all my own engine servicing and rebuilding, and keep to the recommended decoke intervals, so I know I won't have any problems undoing bolts or removing gummed piston rings, etc.

Harking back to some of the earlier comments I'm not constantly looking for somewhere to land - if I really was that unsure of things, I would have quit long ago. I'm supposedly flying for enjoyment, and I take the view expressed by others of trying to minimise the likely hood of engine failure in the first place.

Feathering will of course stop windmilling. Unfeathering the prop should mean that at speeds a margin above the stall speed the prop should windmill but that depends on how much internal friction first needs to be overcome. I have no experience of the Lycoming version of the 42 but it is surprising how much speed is required to windmill the prop on the diesel version presumably attributable to higher levels of friction in diesel engines. It is interesting that the Lycoming version appears to require such a high speed to start windmilling. Have you any idea why this should be so?

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'.

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 ;)

Does anyone think Mr Guppy has run into problems with the small arms fire? I do hope not.

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

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....

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.

Statistics can be interesting when offered to support a belief system.
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?

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.

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?

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 :cool: 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.

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.

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.

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.

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.

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.

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.

What is a Sky God?

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 ?

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?

Almost certainly because the sample sizes are too low.

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.