Go-around after engine failure in light twin

[Flight Safety]

Sorry if this topic has been covered, but a recent accident in my area is bothering me, and I have some questions.

To summarize, the aircraft was a Piper PA-34-220T Seneca, with optional 3 blade props. It departed a North Texas airfield in route to Missouri. An hour out, the left engine failed, and the pilot requested a landing at an Oklahoma airfield, but did not declare an emergency. A witness noted the left prop not turning when the aircraft made what seemed to him to be a fast approach. The witness then noted that about halfway down the 5600 ft. runway at an altitude of 5-10 feet, the pilot applied power to the right engine for a go-around. This aircraft has a max landing roll of 1400ft.

The witness observed the pilot retract the gear and start a shallow climb to about 200agl, but he observed the flaps were still extended. Then the pilot banked and turned left to start a go-around circuit. The witness said that almost immediately after the pilot started the left turn, the aircraft rolled completely to the left, and nose dived right into the ground behind a line of trees, killing all 5 aboard including the pilot's entire family. All 3 props of the left engine were found in the fully feathered position by the accident investigators. The main landing gear was found fully down and locked, and the flaps were found to be fully retracted (???).

So here are my questions. Why did the pilot try a go around at this runway's midspan at 5 ft altitude, when the rollout distance of his aircraft was only 1400ft max? Why did the pilot not declare an emergency? Why did the pilot try a left hand circuit with a dead left engine, instead of a right hand circuit?

There seems to be several things wrong here, but what's bothering me the most is the low and slow left hand turn into a dead left engine. Won't this kill you in a light piston twin? Wouldn't you rather want to turn right instead? Also, what should you do, if you absolutely have to perform a go-around under these circumstances?

What do you guys think?

PS - I forget, the weather was clear afternoon, 10 miles vis, winds 3kts and variable. The temp was 6C, dew point -6C, altimeter 30.35, airfield altitude of 770ft.

(edited to add additional weather data)

[foghorn]

I am struggling to think of a situation that would cause me to try a go around, if I were in the flare on a long runway after an engine failure.

Even in the case of suspected gear failure, with a dead donkey surely it's better to be on the deck with a bent aircraft than struggling to go around and clean up from 5 feet on a single engine.

[A and C]

A light twin will not climb unless all the conditions are right , the aircraft has to have the prop on the dead engine feathered ,the gear UP, 5 degrees of bank into the live engine , flaps up , cooling flaps in the correct position and the WAT conditions also have to be met ,above all blue line speed must be maintained to climb or reduce the rate of descent to a mimimum.

After a go-around as been decided apon it will take time before the aircraft can be re-configered for the climb and during this time the aircraft will be going DOWN.

It is therefore important that a single engine commital height be decided apon taking into account all the above factors and the objects around the airfield that may have to be avoided.

A typical commital height for a low time pilot would be 600ft AGL ,the aircraft should be flown at blue line speed untill this height is reached , from that point on the aircraft MUST land should be slowed to Vref and the landing flap deployed.

It is quite simple once below the commital height the aircraft has NOT got the performance to go around and so must land even if this means going off the far end of the runway at a slow speed or putting the aircraft on a part of the airfield not normaly used for landing aircraft.

To go around below the commital height will mean that the aircraft will be unable to climb clear of some close in object and hit it or the pilot will pull the nose up to try to avoid the object , the speed will bleed off untill the aircraft reaches Vmca and yaw control is lost the aircraft will then yaw and roll towards the dead engine very rapidly and will usualy hit the ground inverted.

I can only speculate that the left turn in this case was the pilot starting to lose control in yaw as to try to turn would have further reduced the allready very small ,if any rate of climb.

[Flight Safety]

Thank you foghorn and A&C, very sobering stuff. This pilot had 10 years experience, but I'm not sure of his accumulated hours, he was a businessman pilot.

It seems to me a pilot who buys a light twin has to be aware of the performance limitations of his/her aircraft on one engine, including the parameters A&C discussed. Buying a light twin is not a decision to be made lightly, especially by a low time pilot. I, like many, also feel that light twins were certified to an inferior standard.

The really sad thing, is this pilot seems to have done everything right (except for not declaring an emergency), with a good showing of piloting skills, up until the point where he decided to perform a go-around. If he had just flown the a/c to touchdown and stood on the brakes, everything would have been just fine, to the joy off all.

At certain times you are just one bad decision away...

[Tinstaafl]

A turn towards the dead engine isn't a problem in itself, as long as the usual caveats are observed such as above Vmc etc.

Sounds like a fast approach, speed not bleeding off in the flare as fast as the end of the strip seems to be approaching so a go-around started.

As has been said, without the correct configuration the only altitude gain will be by trading off airspeed. If persisted then a Vmc departure is the likely outcome.

[eyeinthesky]

And having said all of the above, an overrun off the far end of the runway at 20 kts is far preferable to a stall/spin fatality on a failed go-around!!

[AC-DC]

During my ME training my instructor took me through some go around on a single engine, I was not aloud to use trim. The alt where I was told that the r/w was blocked was about 400’, with one engine shut and the other at full power it was very hard on the leg, after one circuit and one go around the leg started to shake. Hard to say why the pilot did what he did but he made one bad mistake, he has tried to go around.

[Chuck Ellsworth]

AC-DC:

When you were given the single engine go around were you using simulated zero thrust on the "failed" engine?

The engine wasen't actually feathered was it?

Cat Driver:

[ETOPS773]

Would it not make more sense to make a very shallow climb,gain alot of airspeed (more aerodynamic stability=easier to control) and get out of the circuit..trim out..them go and land your plane?Then I`d make sure I have the altitude (when you eventually reach the airfield again),come in fast with the throttle closed an the live engine and it will handle alot better will it not??

ME training scares me as they seem teach you howto fly the aircraft like a turboprop,and drum it into you that you must chase the blue line speed all the time..when there are better options?

[formationfoto]

Always easy to speculate and criticise a decision after the event. When things go wrong it is often difficult to make the right decisions and this is why minor problems turn into catastrophic disasters. Despite having loads of runway ahead I guess he just felt he had got it wrong and wanted to give it another go. In the cool clear air of sitting in front of a computer screen I would opt to land and take an overrun unless there was a sheer cliff ahead of me (or a major highway).

Only flown Cessna 310 and 340 and Seneca. Had one engine failure to date and flew on to next airfield to land declaring dead engine but not calling mayday.

The Cessna 310 would want me to put it on the ground ASAP in the case of failure of one power unit. In feathered condition the climb is very S L O W.

Did an airtest on it once and the feathering linkage stuck so had to fly around for an hour trying to get it right (assumed it was iced up). In the end went for feathered engine approach into our 800 mtr strip. Not much room to get it wrong and I don't think a low go around would have been good news.

I would rather take the certainty of almost right and safe than maybe better or maybe worse but the voice inside your head says "I can do it better next time".

[BEagle]

I was astonished recently to learn that a light twin loses something like 80% of its performance with a single engine failure. But I was even more surprised to learn that there is apparently no published POH engine out allowance for the Seneca even at sea level and ISA. Is that really true? If so, I wouldn't go near one with a barge pole.

Why is there no twin PT6 centreline thrust aeroplane with contra rotating, independent props? Darn sight safer than these 'conventional' twins, I'd have thought?

[Need4Speed23]

I would agree with EtOPS that a shallow climb all the way upto a safe altitude would be a must prior to turning. However, being that I fly a senecca all the time I would not recommend a single engine go around feathered por not, especially with 5 people on board. That aircraft was probably pretty close to gross wt. What is a huge factor missing is what was the density altitude. If it was a hot day then we can expect relly bad performance.

As to why would he go around. That would be second guessing, but I would rather belly up down a runway into the grass and even knock into a fence/trees at the end of the runway at 10kts than try and climb in one of them. Yes you can, and I simulate feather for my students during a Single engine ILS and make them Go-around from the DH. If they don't clean up quickly that rate of decent doesn't reduce much. I think the left turn if intentional may have been a bad idea as you further lose climb performance due to increased Drag. What I see a lot of here in the US is that people own there own plane and fly around 10years, but when do you think was the last time they practiced a lot of engine failures. I see this when I give people the required two year flight review.

Beagle, most light twins lose about 80% of its climb performance when they lose an engine. The senecca is 83%. The FAA only requires aircrafts over 6000lbs to have a single engine climb performance. It is published in the POH on seperate tables what the multi and single engine performance should be at different altitudes.

[QDMQDMQDM]

At least with a single you know you're always going down when the engine quits. With a light twin, the possibility of remaining in the air on one is definitely a double-edged sword. And, of course, you have twice the chance of an engine failure.

We had a good thread on this a while back in which I vented similar prejudices. (Jeez, I've turned into a pprune old bore.)

QDM

[sycamore]

N4S23,
I assume you are using an artificially high DH (or simulated committal height) for your s/e ILS,as you are putting yourself right into the scenario of the subject crash. Your DH on an ILS must reflect the fact that you may have to go-around ,and most normal DH`s on ILS`S are around 2-300 agl; you must descend whilst cleaning -up and getting power on and controlling the a/c first. That should never be taught at 2-300 ft -never..

Formationfoto,
Why did you try to get into an 800m strip when there are lots of civil/mil airfields around the UK, AND not declaring a Mayday either? I would hope that you would not repeat that again..:rolleyes: :rolleyes:

[Flight Safety]

N4S23, the temp was 6C, dew point -6C, altimeter 30.35, airfield altitude of 770ft.

[Rumbo de Pista]

I can't help thinking that a little knowledge is a dangerous thijng, (and a multi-engine rating on a PPL is certainly 'a little knowledge').

A few FACTS about flying light twins:

1. Most of the flying done in light twins is at low AUWs - even an old Seneca 1 will climb on one engine with only 2POB and a light fuel load. In this condition, they're quite safe.

2. If you've any brains at all, you will declare a single-engine committal height prior to any approach, below which you will land or crash, but not attempt a go-around. How low you set that height is largely down to the aircraft. It should be about 500-600ft for a competent pilot in a good aircraft.

3. What sort of airfield you will land at with an engine out is down to you - I wouldn't go into an 800m strip with an engine out, but then I've only got half-a-dozen thousand hours or so.

4. The comments above about 'not declaring a Mayday' demonstrate a weak understanding of the big picture. What do you think this will achieve? Calling Mayday doesn't get you any more thrust, height, or speed - and those are the things you need! Yes, the little red land rover might come out to meet you at a small airfield. At a larger airport, the fact that you're on one engine (assuming that you bother to mention it to ATC at all - and you should, because you're not going to be able to taxi far after landing!) will prompt the controller to get the AFS out.

The main point, I think, is that a Performance E aircraft is not a performance A aircraft. that's why you don't buy a ticket from an airline and find yourself on a Seneca. I believe that pilots of light twins know far too little about the real performance of their aircraft. Yes, you can go-around on one engine in a light twin, provided you start at the right height and do the drills correctly whilst flying accurately. No, you can't do it lower than that, or if you get those things wrong.

[CaptAirProx]

Rumbo,

By calling a Mayday or Pan gives you free airspace and therefore extra brain cells to fly the aircraft.

Its called load shedding. I would rather tell air tragic so that I know I will have the runway for me and everyone will get out my way. Also the R/t drops dramatically.

This has to be a good thing for low houred pilots in particular. They need all the brain power to fly the aircraft.

Something I see very frequently in Multi Training (Senecas) is that pilots come in high and fast on a simulated single engine approach. They are frightened to get "low" and "slow" on the approach (a good thing) but fail to achieve the correct approach angle. They then find themselves over the grass strip going at warp factor ten. If they had made a definate decision at commital they would have the option of go-around. But they very rarely do. They are hell bent on salvaging a balls-up approach.

[A and C]

I dont think that you understand the lack of performance that you can expect from a light twin with only one engine working.

The climb will be very shallow when the aircraft is flown at "blue line " speed , above that speed and the aircraft will not climb and below that speed the aircraft will not climb and you run the risk of the speed decaying towards Vmca , on a good day dont expect more than 2-300ft/min ROC.

Light twins require far more in the way of stick and rudder skills than larger aircraft and a deep understanding of aircraft performance (or rather the lack of ) it is clear from some of the posts above that people expect far more in the terms of performance from a light twin than it can give.

[Keef]

The rule of thumb I was given, by a very wise and experienced instructor, was that in a light twin the failure of one engine means that the other engine will take you all the way to the crash.

Some will climb on one engine, some won't, he said. Persuaded me to go for high-peformance singles rather than twins. I have no regrets on that score.

I've had my engine failure (are we only allowed one each under JAA?) in mid-channel - made it to land. That was in a single.

[Rumbo de Pista]

Airprox,

You're absolutely right, if we're talking about CAS. Outside CAS, calling Mayday may help, but it's certainly not a priority. How often, when instructing, do you see the stude get the RTF call out in near-perfect style whilst forgetting to fly the aircraft? This is something that really used to worry me - studes forget that we survive by 'aviating, navigating, and communicating', in that order, whatever aircraft we're in.

[rustle]

Flight Safety,

This aircraft has a max landing roll of 1400ft.

Don't know what this means. Did you mean MIN landing roll?

Engine failure is a mayday situation.

Sounds like he had time to make the call (failure whilst en-route) - and this may or may not have changed the outcome, depending on what balked him into trying to go-around from such a low height

sycamore,

Your DH on an ILS must reflect the fact that you may have to go-around ,and most normal DH`s on ILS`S are around 2-300 agl; you must descend whilst cleaning -up and getting power on and controlling the a/c first. That should never be taught at 2-300 ft -never..

The CAAFU will expect you to do an ILS to height 250' simulated assymetric (assuming a normal cat1 ILS with 200' DH and having explained to them that ACH would be 350')

You learn that way, and you're examined that way for IR.

CaptAirProx,

Something I see very frequently in Multi Training (Senecas) is that pilots come in high and fast on a simulated single engine approach

Do you have an ILS they could use for the approach (even in VMC) so they can see that engine-out 3 degrees is still do-able?

Keef,

...light twin the failure of one engine means that the other engine will take you all the way to the crash.

Surely the first part of that sentence is: "An improperly handled..."?

Handled appropriately could mean accepting a forced-landing cf an SEP, descending to engine-out ceiling (and planning that's above MSA) - or it may not mean either of these things...

[slim_slag]

Hi Rustle,

The CAAFU will expect you to do an ILS to height 250' simulated assymetric (assuming a normal cat3 ILS with 200' DH and having explained to them that ACH would be 350')

You learn that way, and you're examined that way for IR.

In the perfect world everybody would learn this in a decent simulator. Problem is, it's expensive, but then so is flying a twin, and so are funerals :( When flying on a moonless night over mountains or the desert in a single, or being low and slow in a twin with only one engine producing power - you are really betting on engines being as reliable as they are.

You are correct in saying that if properly handled a twin should be safe. Recurrent sim training is the only real way to ensure you can properly handle a twin, you cannot practice dangerous situations in a real light twin because they are too dangerous!! Especially if the person training only has a few more hours than the student which was very common when airlines would hire instructors with only 100 hours multi time.

If you are engine out in a twin and ceilings are low at your destination, a properly handled engine out trip to your alternate might be better airmanship.

regards

[Rumbo de Pista]

Again, I'm worried by all the talk about ILS DHs and one-engine-out flying. The two are completely separate!

There is nothing wrong with flying the ILS to DH with one engine simulated failed. There is a lot wrong with thinking you can go around with an engine genuinely failed at 200ft. I'm not a CAAFU man, so I won't comment on their procedures, but when I do ILS training and testing in light twins I always have in the back of my mind that if an engine fails for real below about 600ft, then it's straight into the single-engine approach configuration, attitude, and power setting, and with the intention of landing on whatever is available when we see the runway. It's no trouble provided you've got Cat 1 conditions or better.

Similarly, there's nothing to stop you carrying on to your destination if the weather is good enough to carry out an approach and landing. You simply fly the approach with the decision to land already made. This is where a Mayday will get you a sterile runway etc. (at most places).

It's the big picture, guys and girls!

[rustle]

Rumbo de Pista

Don't worry, no confusion between DH and ACH here :)

Merely highlighting the expectation from CAAFU - simulated (read zero thrust) assymetric, go-around at "normal" DH.

and thanks for not correcting my deliberate cat 3 error...
(now edited and corrected :))
I meant cat 1 :rolleyes: DOH!

[A and C]

Rumbo
Most of the people here just have not got the pictue yet and it is simple......A light twin will NOT go around from ILS minimums on one engine if you try you will crash if you are lucky it will be a soft crash onto the flat ground near the runway if not it will be an object that you cant clear because you cant clean up the aircraft and pick up speed or as you try to climb the speed drops off and you go below Vmca roll on your back and hit the ground inverted.

So this having been said you have to pick a height at which you can clean the aircraft up while trading height for speed and then climb away at blue line speed this height is not likley to be much below 600ft AGL (for pilots new to twins) now that is about 350 ft above an ILS DH so if you have a cloud base below 600ft then you are landing at the wrong airfield.

Think about this hard guys with an engine not working you lose about 80% of the aircrafts performance.
I am sure that the CAA dont expect you to go around from ILS DH with one engine (simulated ) out because they know the aircraft wont do it and they value there lives to much ,the CAA may seem daft some times but they are not stupid !.

From my IR test I remember that the engine was failed on the go around from an ILS and once the aircraft was clean ,the single engine approach was an NDB with a MDH of about 450 ft ,not a lot of room to play with but workable for those of you who are in practice.

[AC-DC]

Chuck Ellsworth

That is correct.

[rustle]

A and C,

Trust me on this one.

IRT wasn't that long ago that I have forgotten, nor was the renewal :)

Simulated EFATO after NDB approach - handle it, then back to two engines...

Then, simulated assymetric before RV for the ILS, assymetric ILS to DH (having explained to examiner that ACH was 350'), go around from 250' (plus 50 minus nothing - usual tolerance) into the visual circuit for assymetric bad-weather circuit to land.

[bookworm]

A light twin will NOT go around from ILS minimums on one engine if you try you will crash if you are lucky it will be a soft crash onto the flat ground near the runway if not it will be an object that you cant clear because you cant clean up the aircraft and pick up speed or as you try to climb the speed drops off and you go below Vmca roll on your back and hit the ground inverted.

This is daft as a blanket statement.

There are many light twins that, at some or all weights, will go around quite capably from ILS DH on one engine -- some do so with rather more alacrity than a single doing a go around. To rule out the idea of a go around in all circumstances may turn a perfectly manageable situation into a an accident.

It's also undoubtedly the case that many light twins at or close to max weight cannot safely carry out a go around from ILS DH.

The pilot needs to know the performance that can be expected from the aircraft in the prevailing conditions and at the actual weight. Ignorance of that can lead to some poor risk management in either direction. Perhaps it did so in Oklahoma.

[fluxgate]

it depends on the a/c load, wx, pilot´s skills etc.
I often fly on C303 and C421. The C421 makes a se-go around, the C303 not. I beleive with a Seneca it is the same problem..!?
Even our KingAir C90 doesn´t like ga´s at full load... ;-)

[joe2002]

What about the rudder trim?

As the engine failure happened a long time before the approach could he have trimmed out the rudder force, and then not removed it – combine this (maybe) with a high approach speed and stress maybe resulting in confusion just above the runway (what’s it doing?) “forcing” him into applying full power?

Or

If he didn’t trim out the rudder holding it could cause tiredness and associated judgement error

Or

He may have trimmed it then removed the trim before starting the approach

I know my leg killed me after doing a join, hold and NDB approach on one engine (IRT)

[Tinstaafl]

The problem is not just whether it will/will not go around.

The available climb gradient capability will often not be sufficient to meet the missed approach min. obstacle clearance gradient.

You may be climbing, but not steeply enough to follow the charted missed approach.

Ok at some airfields eg Sumburgh & others that have lots of ocean over which to climb. Not so good at others that have nasty mountains around.

[Flyin'Dutch']

Hi Beagle

Not sure what you mean by your statement:

But I was even more surprised to learn that there is apparently no published POH engine out allowance for the Seneca even at sea level and ISA

May be you can elaborate a bit and I will have a look and see if I can find what you are looking for.

Formationfoto I can only echo Sycamore's sentiments:

Why did you try to get into an 800m strip when there are lots of civil/mil airfields around the UK, AND not declaring a Mayday either? I would hope that you would not repeat that again..

If things would have gone wrong that would have made interesting reading in the AAIB report.

'The experienced pilot encountered a problem with the feathering mechanism which he tried to sort out by flying on one engine for an hour.

Version 1. He then suffered an engine failure on the live engine and had to make a forced landing in a field the aircraft was a write off in the subsequent landing.

Version 2. After he established that the problem could not be sorted out in the air he flew back to the home base a 800 meter grass strip............................

BTW what is the accelerate-stop distance for a 310?

MHO of course

FD

[rustle]

Flyin'Dutch'

BTW what is the accelerate-stop distance for a 310?

There's a page of gubbins about this in the POH depending upon weight and temp, but here's one example of a 310R Turbo (with assumptions):

2700rpm/32" MP
Full power before brakes released
Nil headwind/tailwind
Flaps up
Level hard surface
Engine fails at Vr
Live to Idle and heavy braking at Vr ;)

5500lbs AUW (= MAUW)
10 degrees C ambient
Sea level
Vr (this weight) 92KIAS

Accel/Stop distance is 3150 feet.

Not a list of variables you want to figure "on the fly" so to speak...

[Flyin'Dutch']

Hi Rustle,

Thanks for your reply.

Accel/Stop distance is 3150 feet

IIRC the CAA advice a factor of 1.3 for short dry grass which takes this number to 4200ft which if my maths is correct is only 502 meters or 1600 more than available at that strip. :eek:

Interesting to see how people are happy to paint themselves in corners.

FD

[foghorn]

I concur with rustle regarding the IRT - I know that at least certain examiners in the Leeds CAAFU require the assymetric approach to be down to minima for the respective approach followed by an assymetric go around from DA/MDA.

Ditto on the renewal test with an IRRE.

[A and C]

So Bookworm a daft statment by me ?.

I see little point in writing about what a lightly loaded aircraft will do on a day when the pressue is high and the temp is low.

This is a thread about aircraft performance at the legal maximum weight at an airfield that has the temp and pressue at the WAT limit.

I think that most of us have worked out that if an aircraft is light it will climb better than if it is at its MTOW.

The fact is that a light twin at a with a typical load on an average english summers day with a low time pilot is unlikly to make a safe go around from less that about 600ft.

Yes bookworm you can pick perdantic holes in some of my statments but you look at the performance graphs and you will see that these aircraft will make 150-200ft/min while crossing the ground at 95ish KT when the aircraft is clean , its not a lot of up for a lot of distance across the ground.

Now will you please tell me how you clean the aircraft up and increase the speed from the final approach speed to blue line from an ILS DH of aprox 250 ft without going down and trading height for speed ?.

I have had to do a single engine go around in a light twin for real fortunatly I had nominated a very conservative committal height of 500ft AGL and it was not to much of a drama but if I had nominated 250ft AGL I would be dead it is as simple as that .

A and C may well be daft, but stupid ? no , and very much alive !.

[englishal]

The SE rate of climb of a PA34-200T (don't have the data for a 220T) at sea level is in the region of 200' per minute, at 4570 lbs (max T/O weight), gear up, flaps up, inop engine feathered. At 10,000' this is in the region of 140' per min at standard temp. SE ceiling is around 14,000'.

So its not always the case that a light twin won't climb on one engine, though the POH for the 200T states that a SE go-around "should be avoided if at all possible" and that under "some conditions of loading and density altitude a go-around may be impossible"....

I was always taught to commit myself to landing when at the FAF of a precision approach and the gear goes down, whether it is on a runway, taxyway or midfield, rather than go around. There is nothing wong with practicing asymetric landings all the way down so long as the 'simulated' engine failure is carried out with the throttle, and that if a go-around becomes nescessary then both throttles are used.

Cheers
EA

[formationfoto]

Sycamore and Dutch
The 800 mtr strip is my home base and one which I have regularly practiced single engine approach to land, and on singles engine off to land (simulated). So I knew what to expect as I had practiced it many times. The time spent trying to free the feathering mechanism (to get to unfeather and to restart the engine) was all spent at 2000 ft overhead the field from which a full engine out glide could be achieved.

Oh yes forgot to mention that I also had a test pilot with me so my confidence in achieving the landing safely (which incidentally I did with around 200 mtrs of paved runway to spare - an a day with a helpful 15 kts of head wind) was not entirely the result of blind faith in my own abilities.

Had I regarded this as beyond my experience or close to the margin for the conditions / aircraft I would indeed have elected for a lengthier runway and more options.

One of the advantages of a relatively short runway for regular operations is that you get used to handling the aircrast in those conditions.

[rustle]

A and C

Now will you please tell me how you clean the aircraft up and increase the speed from the final approach speed to blue line from an ILS DH of aprox 250 ft without going down and trading height for speed ?.

The approach to DH was flown at (min) Blue Line.

Normally you're at blue line to ACH, so during the IRT/renewal you're at blue line to DH.

Remember that Vat in a GA7 is 75KIAS and Blue Line is 85KIAS, losing 10 knots in a Cougar in 200-odd feet (or 3/4 mile) isn't hard ;)

PS, check your PMs

[bookworm]

A and C

I apologise for my use of the word "daft". It was unnecessarily emotive.

Nevertheless, I disagree with you.

I see little point in writing about what a lightly loaded aircraft will do on a day when the pressue is high and the temp is low.

This is a thread about aircraft performance at the legal maximum weight at an airfield that has the temp and pressue at the WAT limit.

But it's not. Neither in the thread leading up to your statement nor in the statement itself do you qualify your "a light twin will NOT go around from ILS minimums on one engine" line. You make it sound as if it applies at any weight.

To take an example, my own aircraft manages a lamentable 150 fpm at MTWA, even at ISA sea level. I wouldn't dream of attempting a go around below 600 ft. With just me on board at the end of a journey, I get at least three times that. To "crash" in preference to a go around in an aircraft capable of more than 400 fpm may be your call, but it's not mine.

In answer to your question, I aim to reach ILS DH at no less than blue line speed (91 kt) anyway. It's not hard to lose the extra few knots required in the half mile from there to the threshold. Flying a single engine ILS, I'd probably fly at 100 kt to DH anyway. Though it's not ideal, most ILS-equipped runways are long enough for that to be fine.

[sycamore]

Formationfoto

I`m not sure you are getting the message.
You are operating a multi,out of a strip that is shorter than the recommended,adding all the factors,or even not! I think you have a rather large bag of "presson-itis".
What may have happened if you had been able to unfeather,but not able to restart the engine- would you still have tried to make it home?
If the engine fails ( and it`s not a pilot digital induced fault)
then shut it down and leave it alone--- except if you are somewhere you really need it,ie mountainous and as a last resort--see reason above!-I hope you were not out to impress your t/p friend- who incidentally should have strongly suggested you go elsewhere as he should know better!


:rolleyes: :rolleyes:

[Rumbo de Pista]

A and C,

You wrote:

So this having been said you have to pick a height at which you can clean the aircraft up while trading height for speed and then climb away at blue line speed this height is not likley to be much below 600ft AGL (for pilots new to twins) now that is about 350 ft above an ILS DH so if you have a cloud base below 600ft then you are landing at the wrong airfield.

and I'm sorry but you're wrong.

First, you won't, I hope, trade height for speed. You will dissipate your energy differently, perhaps, but to say you're trading one for the other gives the wrong impression.

Second, and more importantly, aviation safety relies upon statistical analysis of risk, and the probability of an engine failure occurring during the approach between 600ft and 250ft is so low, that it may be disregarded. Put it another way, if we addressed hazards at similar risk levels, we would never fly.

So what to do if you are on the approach into Cat 1 conditions and an engine fails at less than ACH but above DH? Well, depending upon the aircraft, you're certainly going to use lots of power, and rudder, you might retract some flap, but what you MUST do is continue to fly the approach accurately, whilst forgetting about DH. If Cat 1 RVR existed at the approach ban position, I am happy to guarantee that you will see the runway and lights in good time to land on it. I generally teach this drill in VMC, using the screens, and withdrawing them at 100ft or so. Everyone I've trained in this manner has landed safely.

So, there is nothing wrong, legally or practically, in operating a light twin into a destination on Cat 1 limits. (Indeed, I used to operate a light single to those limits, but do so no more alas - I wouldn't feel bad about doing so again!).

On accelerate-stop distances, I'm not certain that these need be specifically considered for a private operation? Again, an 'operator' might choose to acept that he cannot prove the accelerate-stop case (and that he will crash in these unlikely circumstances), but does so in order to derive safety benefits from flying a twin-engine aircraft. There would be no requirement to prove accelerate-stop in a single, after all...

[A and C]

I will reply to your post but I,v just had a very good lunch with a few glasses of red wine and i think that you deserve a much better reply than you will get out of me right now !

Regards A and C hic !

[Flyin'Dutch']

Rumbo,

You are absolutely correct when you state that there is no requirement to take the accelerate stop distance into account when operating as a private person.

However they do demonstrate something (IMHO of course)

Legal does not always equate to best practice. Or does it?

:D

FF

'fraid I have to side with Sycamore on this one, you are obviously quite happy to operate with what some would consider to be tight margins.

Nothing wrong with that as long as you only expose yourself to the resulting risks.

As always, MHO of course.

FD

[Rumbo de Pista]

A and C,

Looking forward to your reply. Next time, set a place for me too, and I'll bring a little something from my cellars!!

Dutch,

No it doesn't, and in fact, I have 'issues' with 'best practice' anyhow (if it's good enough to be 'best practice', it should be mandatory, if not, we shouldn't do it).

By extension of your other argument, I gather that you only ever fly Performance A aircraft, and only off dry runways...?

[Flyin'Dutch']

Rumbo,

If postings like the one from FF appear I think it is not unreasonable to point out that there could have been different options.

One of the functions that these forums have is to have some substance to them so that folk can not only entertain themselves but also (if so desired) learn something about aviation.

Not necessarily those that contribute but I think a fair few lurkers (nowt wrong with that) may also benefit.

As you can gather from my posting I have no problem with people narrowing their margins, be it at their peril.

So I dont see how you conclude that I would only be happy to fly perfomance A aircraft from dry paved runways.

Anyway on both counts your assumptions were wrong.

Pass over that bottle!

;)

FD

[Gin Slinger]

Just as an anecdote, I was Stateside doing my MEP Rating last month.

During our last touch and go of the day at the training airfield, we decided to do a simulated single engine go around at 500' - and see how far it took to reach 1000' whilst enroute to our home airport - this was in a PA-44, set at zero thrust, at blue line speed, 2 POB and with less than 1/2 tank of 100LL, cowl flaps closed, clean configuration, 5 deg of bank towards the live engine and the rubber trimmed out. It took 10.5 nm!

Thankfully, this was a simulation, over the Florida swamps, not a real engine failure in Colorado! Or Surrey! Sobering stuff.

[A and C]

To answer your post , A committal height is a very personal thing and should consider things such as pilot skill , WAT limit , aircraft weight , which engine has failed , runway avalable , local Geography (ref gin slinnger above) WX conditions, and I,m sure that we could think of some more but I wont go on.
I would think that a low time pilot who had just got a multi engine rating would be looking at around 600ft AGL some one who is just about to do a CPL/IR should be able to bring that down and depending on conditions 350 ft AGL might work but I dont think that I would go below 400ft.

I think that a lot of the posts here are relying on flying the aircraft at blue line right down to the ILS DH this is just fine if you have the runway to stop on but you wont meet the flight manual landing distances , If the aircraft is at ILS DH at Vref with the gear and flaps down then it will not climb away while you clean it up , If you are flying the aircraft at blue line then yes you have a fighting chance of doing so but this also may change your approach cat from A to B.

As to the engine failure between SE committle height and ILS DH i agree it is very remote but you just have to land , you have no choice in the matter after all that is what a committal height is all about.

[formationfoto]

Sycamore
Thank you for your advice and deep criticism of my flying decisions. This is part of the benefit of participating in this forum.
Had I been able to operate the unfeather mechanism but not restart the engine my decision would have been just the same... to land at the nearest airfield which was 2000 ft below me. The flight conditions would have been just the same - a single engine approach to land. Had the engine started then stopped with the prop unfeathered I might have taken a different decision as I had not extensively practiced landing on a relatively short strip with the additional drag of one unfeathered prop.

This was a positive decision to shut down the engine, feather, and restart, to pre test prior to a full test flight for C of A issue.

This was not pushonitis nor was it attempting to impress the test pilot with whom, I fly frequently and would not see a wrong decision as something to impress him, and he would certainly have intervened if he felt anything was being done wrong (given that he intervenes on a lunch trip to Le Touquet if the ball ever moves more than half a ball width on the slip indicator!).

I accept that I will have an 'irresponsible pilot' mark in your index of aviators but there was no other traffic in the circuit, the wind was known, the visual cues to the approach were known, this was a manouvre I had practiced many times, and I have not yet had to perform a go round from not getting the speed / height correct.

Of course there was a greater risk than opting for a runway twice as long but I would also have been increasing the risk of the second engine failing in the cruise en route to the diversion field. How do these two risks play against each other and any other risk factors - probably leaving only a small margin either way. In any event I took an informed decision which given the circumstances I regarded as appropriate as did the other occupant of the aircraft. If we had got it wrong we would have damaged / injured / killed only ourselves (not that this justifies bad decisions!).

I am prepared to accept advice. I am prepared to have it suggested to me that with all the circumstances known a decision might have been better had it been different - after all this is how we learn and all pilots still have something to learn.

[FlyingForFun]

What an excellent thread! Keep it up, guys!

With my incredible 5 hours of multi-engine time, I'm not in much of a position to be able to add to a superb debate. However, I would like to add one thing: from the (relatively small) selection of types that I've flown, I have learnt that you can never make general statements that apply to all aircraft in all cases.

From what I've read, and from my limited experience, multi-engine aircraft don't climb well on a single engine. And if you're at anything other than blue-line speed, they won't climb at all. This is the general case, but I certainly wouldn't go so far as to apply it to a particular aircraft on a particular day, because I don't know the aircraft concerned. If I regularly flew a multi-engined aircraft, I'd make sure that I knew what kind of single-engine performance I can expect from that aircraft, in the forecast weather conditions, and at the expected weight, on the day I was flying it.

To say that light twins can't go around from two hundred feet, or that they can go around from two hundred feet, on one engine is very brave..... to make such a statement about a specific type is a little more sensible, but it only really makes sense to make a comment like that about a specific aircraft, and even then only on a specific day.

FFF
-----------

[Flight Safety]

Guys, thanks for an outstanding thread, I've learned a great deal.

I can see that a marginal situation can get very complicated in regards to the decision making, when you have to fly at or near the margin. SE performance on a light twin certainly qualifies as "marginal" in regards to available power and climb performance.

I just hate the fact that the authorities allowed light twins to be certified with marginal power on one engine. These aircraft are often used by part time pilots with skills that usually aren't as sharp as full time pilots, yet they're required to deal with the complex marginal situations of committed landings and possible go-arounds on a single engine.

In my opinion, this situation should never have been allowed to develop in the first place, from the authority that "promotes" aviation (read FAA). But since it has, all pilots of light twins are left with no option, but to understand this SE performance problem thoroughly, especially in regard to the approach and landing complications.

Once again my thanks for such an outstanding thread.

[Tinstaafl]

I think you're equating light twins and their certification requirements as if they should be the same as transport category a/c.

That's not appropriate. Light twins have never had to demonstrate that level of redundancy.

In terms of redundancy they should be considered to be a single engine a/c but one where the pistons on the 'single engine' are separated, protecting one 'bank' of cylinders from a problem that has affected the other 'bank'.

If you like, think of it as a way of ensuring an engine failure will only be a partial failure. One that still leaves you with some amount of power available, along with services such as hydraulics, electricity, pneumatics etc.

You may have sufficient power to continue flight. Or you may not, depending on WAT, configuration & handling skill.

Just like a real single.

[rustle]

Flight Safety

In my opinion, this situation should never have been allowed to develop in the first place, from the authority that "promotes" aviation (read FAA). But since it has, all pilots of light twins are left with no option, but to understand this SE performance problem thoroughly, especially in regard to the approach and landing complications.

Along with what Tinstaafl has just posted, you must also consider the reasons people fly twins.

Single engine go-arounds and engine failures are things you learn about, practice, and should be regularly re-examined on.

However, the benefits of dual/redundant alternators, suction pumps etc. as well as (typically) greater speed and altitude capabilities (there are notable exceptions :)) cannot be overstated when long water crossings, high altitude MSAs, inhospitable terrain might be in your planned route...

Have a look at this thread:

http://www.pprune.org/forums/showthread.php?s=&threadid=70104

We discussed this in October :)

[CaptAirProx]

With regard to formationfoto's C310 problem. So what if he landed it in an 800m strip. he has done it before so why not under the added stress of an engine out?

I fly and teach multi from 740ms grass. I've known this strip for years. I know the wind effects on approach and the visual clues on approach. A good thing to have when landing into blinding sun!

I would "prefer" to land a stricken aircraft capable of landing in there under those circumstances without shadow of a doubt. However I may want to land elsewhere for a hard runway if the gear is not symmetric or I needed massive emergency cover (unlikely).

I say thumbs up to the man.

Plus it can be commercially better to take the problem home. We have to weigh this up in all emergencies in the commercial world. And I would do to in a light twin. Its risk management. Nothing new there me thinks.

Someone asked me if my students get to see that a twin can fly a 3 degree ILS successfully. Well we don't have ILS. The students do and can fly the approach correctly. But as soon as they are on test or first circuit of the training detail, everytime I sit and watch the power never coming off the good engine until its too late! Maybe its my teaching, but I don't think so as most candidates from here there and everywhere show similar signs.

Regarding another comment re Aviate Navigate Communicate. yes I totally agree. And in most cases I would suggest that informing ATC soonest is low priority, particularly if your not on a published SID. However, all checks and drills completed and plan decided upon - why not tell air traffic so that there should be no reason to go around unless you cock it up yourself. Even at A/G airfields someone declaring their predicament usually gets the red carpet from the typical weekend ex wartime "I've flown for years let me cut you up" lot! Or indeed "I'm important and have a faster plan than you" brigade! Oh I just love weekends at A/G fields! hehe

[bluskis]

55 replies and nobody gives any emphasis to the difference betwen the witness observations and the investigators findings.

The witness stated gear retracted flaps extended, and the investigator stated gear down, flaps retracted.

Many correspondents then lump all light twins together as if they are all Seneca 1's.

Regardless of whether an approach at an airspeed above blue line is sensible or not, and I personally think it is, the question is why did the pilot decide to go round.

I have not seen an answer to this question.

[rustle]

bluskis

55 replies and nobody gives any emphasis to the difference betwen the witness observations and the investigators findings.

Eye witness reports are typically unreliable - we all know that, so it's no real surprise no-one mentioned the discrepancy.

Remember the Airbus crash in Queens? There were as many versions of what happened as there were "witnesses".

Regardless of whether an approach at an airspeed above blue line is sensible or not, and I personally think it is, the question is why did the pilot decide to go round.

I have not seen an answer to this question.

Possibly because no-one can know the answer to this except the pilot, and sadly he's not around to tell us.

Perhaps he was fast, thought he was running out of runway and decided he could go around and do it better;

Perhaps he was distracted on finals, didn't notice he only had two greens until he was just about to land and decided to go around and save the aircraft;

Perhaps a passenger had been quizzing him for the past 30 minutes about single engine performance, so he decided to demonstrate a go around on one engine, but too low.

More often than not the investigators know all the answers (mechanical, weather, other traffic) but can never know the pilot's mind...

[Timothy]

I do think that rather too much emphasis is being placed on some of the lower-end twins.

I went out practicing for my IR/MEP renewal last year in my Aztec E and took four large friends with me. At least three of the five of us were rugby player types, two others were smaller, but adult. We had full tanks, but no baggage. I calculated the weight as being about 140lbs under MTOW.

On a moderately cold day (ISA -5) and everything handled according to the book we climbed at 800fpm from 250ft after a simulated EFATO.

We executed two go-arounds from 250ft and climbed perfectly well. By the time I had burned an hour's fuel and honed my technique, we were closer to 900fpm.

I believe that at least two of the pax are on this forum and can stand witness.

Pilots need to take responsibility for knowing the performance of their aircraft. I agree with everyone that I would be very nervous indeed in a Seneca I, Twin-Comm or Cougar at or near MTOW, and indeed agree that these are singles with their engines split in two, but once you are looking at aircraft with excess power (PA31, C4xx, PA23-250 etc) the whole business of SE operation looks rather more rosy.

There is another factor which no-one seems to have mentioned. Days with 250ft cloudbases on the whole tend to be cold, which is helpful.

So I suppose I am saying let's not generalise with too many sweeping statements, but try to encourage twin pilots to learn about their aircraft, be observant about their immediate circumstances and take the best decision in the prevailing situation.

[Chuck Ellsworth]

Interesting reading, there sure is a lot of confusion about how to fly multi engine airplanes in these replys.

I fail to see anything wrong with formationfoto's decision making.

Is it possible that formationfoto has figured out that it is really quite simple to guide any aircraft down toward a landing versus up to go around?

Last time I landed a twin there was no control problems with both throttles closed. :D

Good reading here though.

Cat Driver:

:D The hardest thing about flying is knowing when to say no.:D

[A and C]

It is a well and documented fact that a light twin will lose about 80% of its performance with an engine properly shut down and if it is flown in the correct manor ,that means that you Aztec E must make over 3000 f/m on two engines , this has got me thinking and I,m of to look at the Aztec flight manual after the new year as the Aztec my well be a much better aircraft than I had first thought.

I would also like to ask what effect you think having to pump the gear up by hand might have on the ROC during a single engine go around ?

[Flight Safety]

Perhaps the following facts MIGHT (and I repeat "might") shed a little light on why this pilot made the decision to go around.

When the pilot started flying 10 years ago, his wife made him promise that he would never fly at night, and never fly in bad weather. To my knowledge he kept this promise, even though he was IR rated. His wife also had a very bad car accident last year, and only recently recovered from it. The plane was occupied by his entire family, including his wife and 3 children.

My wife and I have spoken at length about this accident. She thinks that maybe the engine failure terrified the wife, because she was afraid of her husband's flying in the first place, and had also recently experienced a bad traffic accident with a very painful recovery. My wife thinks that maybe she was panicked by the emergency, and maybe thought they were going to crash at the end of the runway as he neared touchdown, and maybe she frantically talked her husband into a go-around.

Anyway that's my wife's opinion, and of course this is pure speculation. Fear in the cockpit couldn't be a good thing, but again, pure speculation on my part.

[Chuck Ellsworth]

Flight Safety:

By posting this tragic accident it will hopefully reinforce the need for pilots to show currency through ongoing check rides.

The cost of recurrent training pales when we see the cost of this accident.

Cat Driver:

[sycamore]

A Verry Happy New Year To You All:)

ffto
Haven`t written you out at all-yet,
remember- if it ain`t broke - don`t fix it!
if it is broke- don`t try to fix it in flight(unless you are an engineer ,and can do so!)
Why fly around for an hour trying to unfeather a prop?you could have probably flown to an airfield,found an engineer and fixed the problem and flown home in that time!
Why did you suspect it had iced -up? were you in icing conditions with the engine shut -down?
As I said earlier ,you may have compounded the problem by playing about trying to fix it in flight, and may have ended up with a prop unfeathered,windmilling, poss. overspeeding,and found yourself in a bigger can of worms than you thought possible. You had also wasted an hours flying,and you may have found that ,perhaps a little short on fuel ,you then had a gear problem,etc,etc. As you were on finals ,some fool decided to walk across the runway to hug a tree ,perhaps, and you had to go around,-- below committal height-- wind -milling prop, etc etc!

I could ,of course thow in a few more " gotcha`s", but I HOPE the threads have given you, and possibly a few inexperienced twin pilots a few thoughts for the New Year..:cool:

Capt Airprox
On your first post you are in favour of declaring an emergency,as it will probably minimise ATC,etc, and allow a low-time pilot breathing space to sort it all out without duress ,and with probable assistance-- couldn`t agree more!!
Because ,if you don`t declare an emergency ,you may get cut up,and may have to go-around, and may possibly screw it up!

So, if you are instructing, I presume the a/c is PT,what is the accel/stop distance rqd. for a Seneca,on your strip at mtow/rtow?
Why do you want students to get " low and slow" on apps? Even s/e apps should be flown to a nominal 3 deg G/p,at the correct app,speed and configuration; anything else can lead to a lot of trouble.-- or are you an old ex-Meteor/Canberra QFI ?

Syc

[Timothy]

A and C

Maybe the 80% is an average, I don't know. The point is to know what your own aircraft will do. To my shame I don't know what the Aztec will do at full power and blue line on two engines (because I normally climb at 25/25 and 130kt, which gives about 1,200fpm with 2 POB and full fuel). As a matter of interest I will try next time it's convenient.

Incidentally, my personal rule is that if I have an engine failure on takeoff with the gear down, I am going down regardless. The red lever is there for adjusting the flaps on the ground and nothing else!

I leave the gear down to a point where I can no longer land back, then raise it, that point being the decision point for continuing. I will adjust the point I raise the gear depending upon runway length, the state of the terrain after the end of the runway and the met conditions. I also adjust rotate speed and climb speed depending on conditions - rotate and climb fast to favour continuing, rotate slow and climb steeply (blue line) to favour landing back.

On landing, if I had lost the left I would continue to land regardless; let's face it, I wouldn't have started the approach if a landing were not possible. The decision what to do if I had lost the right would be more marginal, but I would probably still bust minima and land.

I think the trick is to find a runway where (with a full mayday, incidentally) you can be 99% certain to land but I am confident that I could walk away from a landing in zero/zero, even if the aircraft were damaged. I was trained to do this as part of my IR by Dai Heather-Hayes.

[CaptAirProx]

Chuck, I couldn't agree more. At least JAR has started something worthwhile and thats the yearly Prof Check on a Multi Rated Pilot. It was about time. When teaching multi to PPL's I always ram home the need to start approaching flying twins in a very professional and considered manner. More so than the days of your PPL initial.

Sycamore,

Regarding ASDA/EMDA. At Rtow which it isn't normally then it would be the full length of the strip.

If it was max well depends. But here is were we delve into dodgy ground. If you use the published CAA approved take-off performance figures one cannot operate a Seneca out of such a strip. Simply because there is no approved perf data for using the short field technique with 25 degrees of flap.

Piper have produced charts for these configurations but were never formally added to the Piper Approved Manual. So if operating to Public Transport Pax Carrying etc then it is illegal. But my understanding is as it is Aerial Work, we can operate to Non Public Transport rules, despite the aircraft having mandatory Public Transport CofA!

Therefore using 25 degrees at max weight and wet grass with calm winds on a warm day it is legal according to Pipers Handbook. Yes it is tight, when an engine fails. That is why the takeoff brief is quite explicit. One has to be aware of the fact that rotation happens below Vmca. Therefore students/pilots are taught that one should close both throttles land back on and prepare for slow impact with fence etc or into farmers field as is the case of a single engined aircraft. ALso until blue line and 300 feet is achieved after T/o, a forced landing with the good engine is required. This also involves a shallow turn to avoid housing.

Remember, some Senecas are certainly classified as Perf E - They will force land in any event. That is why we also use the Perf E take-off perfomance check of noting that 80% of unstick speed is achieved in 40% of TODR. I may be incorrect here as it might be TORR. I would need to check in our ops manual as I can't remember off hand now! Haven't flown it for a couple of months, and don't teach often enough to have it all lodged in the brain! And I can't be bothered to work it out logically whilst typing! It was a heavy night last night!

Regarding the low and slow bit. What I meant was that pilots are taught to fly the single engined approach to the same aspect (angle) as a twin approach and obviously not below blue line until commited. Ie 3 degrees/91 knots. But students tend to feel when underpressure that this is low and slow, so consequently end up high and fast! I was trying to put in words what I believe the student often believes, not what they are taught.

As to the Canberra/Meteor QFI bit. Well as much as I was taught by an ex RAF pilot of similar type experience, I was never alive when they flew operationally! No offence taken ;)

[Rumbo de Pista]

WCollins,

Regarding your engine-out performance, how did you evaluate the power setting for simulating engine-out on that day, and what was it, please?

Your remarks about retracting the gear late in your Aztec are way off the mark. The technique you describe has benefits for single-engined aircraft, but you're being unnecessarily pessimistic in your aircraft.

Flight Safety,

Speculation such as yours seldon achieves anything more than upset of those close to the deceased and injured. How much training in air safety investigation has your wife had?

[Flight Safety]

Rumbo, I appreciate your comments. I was torn about whether to post the personal information at all, but in this case decided to anyway.

I can only think of one logical reason to post such information, and that is the influence a strongly motivated passenger can have over a pilot's decision making, during a critical moment in a flight.

I recall the Gulfstream G-III crash at Aspen in March 2001, when a charter customer sitting in the cockpit, pressed the pilot into attempting a landing in very bad weather, when his judgement should have told him otherwise. The pilot was pressured by the charter customer into a must land "press-on-itis" that got all aboard killed, when the pilot continued the approach below the MDH and still didn't have the runway in site, and when all other indications were telling him that a legal safe landing was a low probability in the prevailing conditions.

All I know is that the decision of the Seneca pilot to attempt a go-around at 5ft altitude, when all other indications should have been telling him that a safe landing was very to extremely likely, is baffling to say the least. Again, I'm still torn about whether to leave the personal information in the post or to delete it, however it might be possible that he was influenced by a passenger to attempt the go-around.

I've noticed that undue influence by a passenger, that causes a pilot to make a bad decision leading to an accident, is rare, but is a factor in a certain number of accidents. In the end as we all know, the accident investigators are in the absolute best position to make a determination as to the probable cause of this accident. However we're all here just trying to learn something from this tragic accident, and like the investigators, we learn by looking at it from a variety of different angles.

[bluskis]

If nothing else has been gained from this thread, there must be a caveat to anybody thinking of aquiring a twin for the added safety a real twin can give over a single.

This caveat is that a thorough understanding of what exactly a given aircraft offers in the way of performance is the primarliy important factor to be considered.

Few pilots want to know what a marginal aircraft might do in the hands of a test pilot operating out of a high level short strip he has used for the last 'n' years when he is considering parting with real dollops of cash..

[Timothy]

Rumbo

I usually add about three inches to the MP at throttle back, which is probably a little pessimistic.

I can't go along with my conservative position on leaving the gear down as being "way off the mark".

Firstly remember that I only have one hydraulic pump, so, as A and C pointed out, I am stuffed if I lose that engine and want to land back.

Secondly, I would like to remind you of the tragic C404 accident at Glasgow, where a top-hole pilot took the decision to continue rather than force land, with disastrous consequences (8 dead, 3 injured).

Thirdly, I refer you to the article in the current "Pilot" by the guy who decided to land back in a Perf A a/c (748 IIRC) at Stansted.

Landing back is not for whimps, is is a valuable option in our armoury, and is made much easier if you leave the gear down 'til you can't use it no more.

If you consider leaving the gear down "pessimistic" then I am honoured. I am a pessimistic pilot, and that pessimism has kept me alive through the 32 years I have been flying:)

[john_tullamarine]

If the book doesn't give you much to go on, a useful way to determine an approximate zero thrust setting for the conditions is

(a) feather the engine and trim out for the desired speed
(b) restart and adjust the "failed" engine until the same flight handling and performance is achieved at the same density height.
(c) do this for a few test points and you have your zero thrust schedule nailed.

Needless to say, this exercise needs to be done on a nice day with no turbulence ...

[A and C]

FLIGHT SAFETY

Please leave the posts just as they are I think that it is a good insight into what MIGHT have been the reason for the pilot attempting the impossable.

W COLLINS

Like me you have a very pessimistic view of light twin SE performance.

With regard to the BAe 748 land back at Stansted some years back I was able to talk to the captain of that aircraft ( i was flying another RR dart powerd type at the time and wanted to know why it failed) Performance was not an issue in this case , the fire was ! and the "land back" would have left the aircraft with no further damage had there not been a drainage ditch just off the end of the runway.
This was a superb piece of airmanship and undoubtidly saved the lives of all aboard as the fire would soon have destroyed the wing.
This also leaves me to speculate if the air france Concorde would have been better to have landed stright ahead in a field after all it was in the same performance situation as a light twin ,50% of its power missing and too much drag , with the landing gear stuck down.

This is of course sbject for discussion and not a critisisum of the crew involved i doubt that I would have done any thing different as the "land back " option is one that is not at the top of your mind in a perf A aircraft.

[Timothy]

A and C

With regard to the BAe 748 land back at Stansted some years back I was able to talk to the captain of that aircraft ( i was flying another RR dart powerd type at the time and wanted to know why it failed) Performance was not an issue in this case , the fire was ! and the "land back" would have left the aircraft with no further damage had there not been a drainage ditch just off the end of the runway.

Absolutely true in this case (from my reading of the article in "Pilot") but I don't think that in any way devalues my argument.

There are many potential reasons for wanting to land back quickly, regardless of performance (I personally have had smoke in the cockpit (x2), total electrical failure at night and severe vibration on rotate, but these are only examples) and if you are taking off from a long runway (I typically use IFR fields) it is simply good sense to leave the odds in your favour by leaving the wheels down.

If I cannot reasonably expect to land back (fog, water, town, mountain, cliff for example) I whip the gear up very quickly.

[A and C]

I was not trying to de-value your comments just pointing out that aircraft preformance may not be the only reason for a land back , and that even in a perf A aircraft a land back may be the best option.

[Rumbo de Pista]

Very disappointing. Lots of utter rubbish now being talked here by people who haven't done their homework.

Re the 748, a serious fire does not present the commander with the problems that a straightforward loss of thrust does. (He was lucky to get away with it, by the way, though I also agree that they did a sterling job of preserving life. I simply wouldn't travel on a Budgie, nor would my employer ask me to).

WCollins, your method of setting zero thrust is as far off the mark as your thoughts on retracting the gear late. Statistically, the loss of engine versus loss of hydraulic pump case is at about 10powerminus11 and thus irrelevant.

The most power and height and the least drag will save your bacon. You'll achieve that by taking the gear up on positive rate being achieved.

John Tullamarine,

Thanks for injecting some logic - you're spot on, as usual, with the caveat that you need to plot the values graphically, assess for atmosphere, and extrapolate. I expect you knew that and left it our with regard to the 'target audience'.

Broad-brush arguments about 'landing back' in 'a Perf A aircraft' are balderdash too. How do you think I would get by, landing back in my Boeing? An only-just-perf-A-when-they-built-it-turboprop and a 60ton plus jet are two very different aircraft.

Sad, really, as there had been some (not a lot, but some) good discussion until the last crop.

And now I'll have to ask Senora de Pista for my tablets and scotch...

[Timothy]

Rumbo

Shame this had to get abusive...that really is a way of wrecking a decent thread.

I trust that you don't influence anyone to try and keep flying when they should put it back down.

[Chuck Ellsworth]

John and Rumbo:

Exactly, I sometimes wonder how such important subjects as aerodynamics and aircraft performance limitations get so skewed by voodoo theorys that result in incorrect procedures being used in flying these things.

Maybe , just maybe these discussions here will benefit some of our slightly confused colleauges.

PS.

John:

Now that I have been granted CASA approval for issuing type ratings to Australian pilots I have an even better chance of visiting your country. :) Not to mention I really want to fly HARS Super Connie... :) :)

Cat Driver:

:D The hardest thing about flying is knowing when to say no.:D

[CaptAirProx]

Rumbo, please remind me why you won't fly on a Budgie?

I am surprised a chap of your type experience could have such views?

[Rumbo de Pista]

AirProx,

Because they're old and often a bit knackered. No offense to those who do, but I did my bit in FK27s a while ago and have no desire to repeat the historic flight experience.

And sorry, but what do you mean by my 'type experience'? how come you know so much about it?

WCollins,

Not abusive, just a statement of fact.

I can understand you're a bit sore, but God forbid anyone takes too much note of your ideas. I'm sorry, but they're wrong, and part of being a good aviator is accepting when you're wrong. Another part is saying 'you're wrong' to someone who is wrong, and backing it up with sound info.

Your ideas about retracting gear are wrong, your method of calculating zero thrust power settings, your critique of the 748 accident, your criticism of a dead professional pilot (God Rest His Soul), your remarks about your hydraulic pump, and that dreadful story about your amazing Aztec, all demonstrate that you don't know what you're talking about.

Rumbo

[sycamore]

So , Rumbo,
Now we`ve all had our wrists slapped( except John), for all sorts of " RUBBISH, BALDERDASH,POPPYCOCK,etc etc;

Next time you are in the sim.; give yourself a Fire , on rotate ,; it doesn`t go out, so you fire all the shots and it still doesn`t go out------What are you going to do?
PA--" Dont worry folks, this is your Captain speaking; we are in a Perf A aircraft and we will carry on as normal, as my employer would think I`m a Prat if I tried to get this Boeing back on the ground safely, without harming you "

Even if your employer is the well-known Australian Cultural Attache, Sir Les Patterson, who is known to spit -it-out (literally), and is having an affair with Dame Edna), I`m sure he`d be willing to send you on a CRM course , so you could at least be seen to drop off your perch ,occasionally:cool: :cool:

[john_tullamarine]

Chuck,

Do let me know when you are heading down under and we can schedule a beer or ten .... if I am in country ... otherwise we shall have to meet up in neutral territory somewhere out in the pond ..

[Rumbo de Pista]

Sycamore,

No, we fly a VERY abbreviated circuit or dumb-bell and land. This is, in fact, a VERY good exercise to give, especially on command courses. It provides an excellent way of upping the workload and the succssful outcome depends upon a very high standard of CRM and decision-making. Again, I cannot say clearly enough that such catastrophic fires are extremely rare, largely because the potential for them has been designed out of the aircraft by means of mounting the engines well away from anything nasty and putting lots of isolation valves in. That's why Departure Alternates are allowed to be so far away. If I tried to re-land, I would write the aircraft off and probably all the people in it. Once again, I make the distinction between small turboprops and their bigger jet-powered brethren. Once again, I would remark that events at the end of the probability scale, such as really big engine fires, are so improbable as to be worth excluding from any reasoned and informed debate.

John,

I am sorry if anyone took my tone out of hand. I shan't bother the Private Flying forum any more because (a) I don't feel that there is much top be gained from uninformed debate like this and (b) I don't think any of us do ourselves or the industry a favour by allowing that which is clearly wrong or bad advice to stand unchallenged. I've been flying and instructing long enough and on enough types of aircraft to see the damage that 'bar room chat' on technical matters can do, especially when it's taken in by those insufficiently able to analyse it and see its faults. I think my remark (a longh way above) about 'a little knowledge' may have been prescient.

I didn't say anything here which I wouldn't have said in a meeting of Training Captains or managers. People are used to my challenging style, and I get on very well with colleagues! Now, I sense that I'm not welcome here, so I wish all you private flyers well and bid you adieu.

[john_tullamarine]

Rumbo,

Oops ....

I really should keep track of which forum I am in ... a bit late in the day and after a sim session ... so fatigue might be a reasonable excuse ..... I thought I was in Tech Forum ... largely as the thread was revolving around routine Tech Forum things and some of the participants are regulars in that place.

My comments were out of order in this Forum and have been removed.

Rest assured that I was not directing those comments at anyone in particular.

I concur that the industry is rife with misconception and error .. but I still think that we can all do our bit to move toward the light in a sensitive manner where abruptness is not immediately necessary ..... What might be said with the best intent and good effect in a confidential, behind closed doors, flight standards management forum sometimes reads better if toned down in open forum.

Rest assured that your reasonable and considered observations will be welcomed in Tech Forum.

[A and C]

Uninformed Balder......? aha !.

I have to ask you if a perf A aircraft can still make perf A performance with two engines out on one side ?

I think that it will not and so is no longer a perf A aircraft and should be flown like a perf E aircraft.
I have no wish to fly my Boeing in this manor but I consider it a major dis-service to the pax and the rest of the crew to have not considered the posibility of having to do so and having the option in the back of my mind.

I await your reply with interest.

[BRL]

A&C
I have no wish to fly my Boeing in this manor The emphasis here being on the word MY in the above quote. This from the man who totally flamed me for writing in an e-mail my forum....... ;)

Just to keep this post slightly on topic, I did see the seneca that landed about half a mile away from the runway at EGKA when it ran out of fuel...... :rolleyes:

[CaptAirProx]

Rumbo, I have no idea what your type experience is. However, on the basis you now fly Boeings, I was rather hopeful that you had worked your way up from the filthy ranks of light aircraft through turboprops to jets. Certainly thats the impression you give on here regarding these "outdated types".

I find it a great shame that a man in our profession can be so ready to spit on the very aircraft that he/she probably learnt their trade, and for some are the only aircraft they will fly or indeed WANT to fly. All aircraft have their place in aviation.

I would imagine you are one of these guys that used to fly single engine over the channel without question in your early PPL days. Now it is seen as cras decision making by those that do. Just because you can sit in a warm multi engined aircraft now. I agree I will now try and go twin engine when flying GA across the water for jollies et al. But I will still do it if push comes to shove. It gets the adrenalin going and reminds me of all those exciting flights I did when really new to aviation. Very humbling.

You appear to be very dismissive of others which I would find very challenging if I was your colleague on board. Have you heard of a reasoned non-personal argument? Remember, you may be a professional in your field but this is a Private Pilots Forum that has contributers which may not have the experience and wisdom you have. Lighten up and allow people less experienced than you, to ask you informally any questions they like. Then the unitiated of us my feel inclined to ask and probe at your tales of wisdom. We could then all learn and perhaps work as a team! Flying is about learning from others so don't ignore every comment you hear, please.

I quite enjoy flying my 30 ton diesel powered aircraft. One day I would like to have a go at a Boeing. I just hope that when I do, I will not have forgotten what real flying is all about.

[Timothy]

So, I am in my Aztec at Newcastle, using full length, gin clear day with a 15kt wind straight down the runway.

I rotate at 75kt, 330m of runway behind me, 2000m in front of me. I whip the gear up and I am at 100ft, 85kt when BANG, massive yaw to the left, severe vibration.

Someone tell me what to do. (Remember that no left engine means that if I want the gear down I have to either pump it manually, 40 strokes, or fiddle on the floor between my legs looking for the CO2.)

Come on...someone tell me that I am better off with the gear up than down.

W

[2Donkeys]

Horses for courses don't you think Mr Collins? You have constructed a scenario in which in almost any light twin, there would be every reason to land ahead and sort the problem out on the ground.

This conclusion is underlined all the more strongly when you consider the limitations of the Aztec and its sad old hydraulics, together with the environmental conditions you cite.

By contrast, on a low vis day, where ground contact will be lost as soon as the aircraft lifts off, you would presumably acknowledge the value in cleaning up and climbing away ASAP.

The maths being what it is, even on a pleasant day of the sort you describe, you will rapidly reach a point in the climbout where landing ahead will cease to be an option, even on a long runway, as you approach that point, the gear will not benefit you by dangling down. We are talking about a few seconds delay in raising the gear even on a relatively long runway.


The real danger that this subsection of this often-heated thread reveals is that it is a big mistake to have a fixed view of your plan for engine failure. The plan will need to change, not only to take into account the aircraft concerned, but also the runway, the weather and your load. The GA pilot almost needs to think like a transport pilot before lining up, rehearsing his Engine failure plan for *this particular* departure to his imaginary first officer as part of the checklist.

[Chuck Ellsworth]

Two donkeys:

Good comments especially the last par.

Rumbo and John:

For those with experience and knowledge to not post in the private pilot thread would then leave these people to wallow in ignorance.

Cat Driver:

[Timothy]

2 Donkeys

Thank you. I agree with every word you say, and it is almost exactly what I said in the third paragraph of my posting of 1/1/03 for which I got flamed.

I agree that the more pros on this forum who know what they are talking about the better, but there is nothing more dangerous than the one with all the egg on his shoulders, all the letters after his name and all the hours in his logbook who can convince or browbeat the world that he is always right, and who is dangerously wrong.

[Tinstaafl]

WCollins' scenario is one that can be fairly easily mitigated by leaving the gear down for a little bit longer than usual.

Select gear up once you judge it no longer feasible to land on what's left of the rwy AND you have passed at least Vxse. The act of selecting gear up becomes your 'go / no go' decision.

There are caveats to this method though. It depends on the circumstances of the day.

Is there an obstacle that must be cleared?

Is it a short runway that requires maximum climb angle?

Is D.Alt such that a one-inop climb is not feasable?

[englishal]

330m of runway behind me, 2000m in front of me. I whip the gear up
...doh just been beaten to it!....Well, here's my input anyway....In your scenario, the gear should still be down, and only put away when "out of usable runway". However, if said gear was up, if I couldn't climb or avoid high ground, then no decision to make, I'd put her straight back down, even if it meant no gear. I certianly wouldn't initiate a crash trying to put the gear down as that'd look really stupid in the AAIB report;) Better to land on the runway Gear up, than on a field, house, Dixons, KFC etc..

Cheers
EA:)

[Rumbo de Pista]

My absolutely last and final twopennorth in this forum...

AirProx,

I worked my way up through light singles, twins, helos, glider tugs, gliders, old turboprops, new turboprops, little jets, bigger jets, line flying, teaching, managing... I used to drive a knackered old car. Now I don't have to. I used to fly in old turboprops, now I don't have to. I did say 'no offense', and I meant it.

A and C,

I suggest you go and find out what the definition of a Perf A aircraft is. And are you a cockney? I'll be very happy if you keep your aeroplane out of my MANOR!!

Chuck,

Thanks for that.

WCollins,

I really do believe you need to do a lot more studying and thinking. Good luck.

Happy wallowing all!

[A and C]

Down the goldhawk road it is considered bleedin obvious that whatever the "perf " group of an aircraft if for what ever reason thrust can not overcome drag it will soon be going down.

No matter what the aircraft if the thrust vs drag problem can not be quickly overcome then a controled landing in a field is a much better option that maintaining height with reducing speed untill you stall or reach Vmca.

Regards A and C , the boy from the bush.

[BRL]

I have just written A&C a personal apology and I am apologising here for an earlier comment I made in this thread. A case of mistaken identity and I hope it hasn't caused A&C any embarrassement.

[A and C]

Thank you "L" for the apology I was a little confused by the remark but the mistaken identity explanes all !.

Now all I need is for Rumbo to enlighten me as to how "perf A" aircraft have re writen the thrust vs drag thing.

Regards A and C.

[rustle]

For the record :)

Today (5.1) we took an Aztec "E" through it's paces.

Temp was about 1-2 C or ISA-13/14

2 POB, full fuel

Left EFATO at 270' (approx 870' AMSL)

Blue-line climb was 600fpm indicated, gear up, flaps up.

Later we tried the full power to both, blue-line climb from take-off (approx 300' AMSL) and acheived 1700 fpm.

We were probably an hour lighter (fuel) and 3-4 degrees warmer (so ISA-11/12)

[Timothy]

On the flight to which Rustle refers we failed the critical engine.

Does anyone have any idea what the difference in performance is between critical and non-critical engine (on average and percentagewise) or is this a silly question?

W

[Flight Safety]

WC, I suppose the odds of the critical engine failing are 1 in 2, but I don't know if that answers your question.

I found this interesting link on one engine out procedures for light twins. It has some interesting information on why one engine is referred to as "critical", with specific information on the differing yaw requirements. The whole writeup is dedicated to information on one engine out procedures.

one engine out in light twins (http://www.monmouth.com/~jsd/how/htm/multi.html)

[Timothy]

Flight Safety

I will look at the link, thank you.


I don't think that I phrased the question carefully enough. I meant "Will the performance of the aircraft be significantly different following a critical engine failure as opposed to the other engine failing, and if so, by approximately how much?"

W

[2Donkeys]

WCollins

I think you may be hoping/expecting for too much precision here. The differential in engine-out peformance between the critical and non-critical engine will vary significantly between types.


Less seriously, and in many ways more interestingly though, I do note a slight difference of view on the engine-out performance of an Aztec.

In December you said


I went out practicing for my IR/MEP renewal last year in my Aztec E and took four large friends with me. At least three of the five of us were rugby player types, two others were smaller, but adult. We had full tanks, but no baggage. I calculated the weight as being about 140lbs under MTOW.

On a moderately cold day (ISA -5) and everything handled according to the book we climbed at 800fpm from 250ft after a simulated EFATO.

We executed two go-arounds from 250ft and climbed perfectly well. By the time I had burned an hour's fuel and honed my technique, we were closer to 900fpm.


Rustle tells us that in a very similar aircraft :D 1200 fpm was achieved with both engines with a considerably lighter loading. With that same loading, he was only able to achieve 600 fpm after EFATO on a very cold day.

Do you think that it is simply a question of rustle's technique needing to be brushed up, or is it down to the clapped out aircraft he was flying in? :p

[Timothy]

2

Ah! A rare example of your inability to read.

Put on the right glasses and read what Rustle rote

W

[rustle]

WCollins

Have just been through the perf data for a 310 and there's no mention of performance difference between port or starboard failures.

Logic suggests there may be a slight difference, as critical engine failure should require slightly more rudder input (hence more drag)...

2Donkeys

I think you misquoted me - we achieved 1700fpm both engines full power at Blue line :p


Later we tried the full power to both, blue-line climb from take-off (approx 300' AMSL) and acheived 1700 fpm.

We were probably an hour lighter (fuel) and 3-4 degrees warmer (so ISA-11/12)

[2Donkeys]

W(!)

Its my typing rather than my reading I'm afraid!

1700 fpm is fine full power, it is the 600 fpm on one engine on a colder day, and with a lighter load that I was concerned about. Perhaps rustle could benefit from flying with you, so that he too can benefit from the 800-900 fpm climb rate that you achieve.

Just think about it, if he could show you how to get 1700, and you could show him how to get 900, you would have a marvellous animal, an aircraft that loses less than 50% of its available climb performance when an engine fails.

---- PS: I do know that I am being slightly unfair here! :cool:

[Timothy]

2

Incidentally, I noticed a big, well loaded, Cessna twin departing yesterday on a long runway (though, surprisingly, not using full length) on a clear day, over farmland and whipping the gear up immediately despite apparent land-ahead possibilities.

Any idea what might have been going through the pilot's mind?:D

I have never sought to explain the performance I got on that day, but I do feel that Rumbo and you are casting aspersions.

The fact of the matter is that it happened and I can offer two witnesses to whom I pointed it out in surprise at the time.

Both are well known to you, 2, one being a surprisingly well-fed Buddhist the other being an ex-RAF type with a wife with an unusual name.

The fact that I pointed the VSI out to them demonstrates that I was as surprised as you and Rumbo, but I would rather find an explanation than make vague accusations of lying or exageration (both vices that you know I don't suffer from.)

One sensible explanation I can think of was that the zero-power setting was different. In the first case I set it, in the second it was Rustle, and we may have used different formulae.

Another explanation is that on the first occasion I was much more current than yesterday and may have been paying more attentiuon to getting the ball exactly in the right place and the bank angle exactly right.

W

[A and C]

As I understand it if an aircraft has a critical engine all the performance graphs and Vmca are based on the failure of that engine.

After all if the other one quits it can only be better.

[Timothy]

A and C

That's my understanding too....I just want to know how much better.

W

[2Donkeys]

Do I know you? :D

Its a good question. Let me tell you why I selected the strategy that I did for that take-off.

For the benefit of those not at North Weald (the airfield concerned) yesterday, here are the facts.

The aircraft was a Cessna 421C and the runway in use was 02 which is 6300 feet long give or take.

The aircraft contained three adult males (two big, one average) and two very small children. We had just 2 hours endurance and were therefore very considerably below MTOW. It was a cold day. ISO - 13 on the ground.

The book says that the distance required to clear 50 feet is 2250 feet with those factors taken into account. The ground run is around 2000 feet. Accelerate/Stop is a tad over 4000. If an engine fails at rotate and I elect to carry it into the air, the books suggest a little over 4800 feet to get above 50, but I can sustain a SE rate of climb of around 400-500 fpm at that weight with some considerable comfort. At MTOW, SE climb is a less impressive measured 300 fpm.

All of this assumes a rotate at 106 knots which is already comfortably higher than my Vmc.


So, with the data done, back to the question.

If the engine had quit at or before Rotate, I had ample runway to close the throttles and brake to a halt. Full length was not absolutely necessary, although I only left a 30-50 foot gap at the very end to allow a small aircraft that had backtracked behind me to get around my tail before I rolled.

Once the wheels have left the ground, and you are at 50 feet, you are approaching the halfway point on the runway. If the donkey quits, you have a choice, you could try and put it down in the *rapidly* diminishing runway, or knowing that you are very light, you could carry the problem away, confident of a climb performance that would easily deal with any obstacle, and that would outstrip most of the SELs taking of yesterday. You fly the circuit and land. [*purists read the footnote]

Critical to that climb performance is having the airframe cleaned up. With an engine failed, the 421 gear takes 7 seconds to retract, as opposed to 4 with both engines operating.

All factors considered, once safely climbing I took the gear up, and climbed away. Landing ahead (off runway) was not an option that I was likely to have to consider. Not least because whilst there are fields, there is also the busy A414 within the likely landing zone.


As I wrote earlier, I think it is a big mistake to have a dogmatic view of what you do with the gear. The trick is to have a knowledge of the aircraft, the prevailing conditions and the runway in use, and formulate a plan for that set of circumstances.


[* footnote - Engine failures are not always instantaneous in real life. Surging, yawing and swinging often herald a failure. This is frightening and confusing, but more importantly, in this context, takes valuable seconds and distance. It is a pretty good bet on the 6300 feet of North Weald that once the failure was reacted to, the available runway on which to put down would have gone.]

[Timothy]

2

We may have met :confused: :p

Sorry, obviously a different understanding of what displaced thresholds are for.

Also I miscounted. I thought you had two ATCOs, a sheep farmer, yourself (ie 3 large, one average) and two kids.

W

[2Donkeys]

Now it is time for you to put your glasses on Mr Collins!

The threshold is considerably before (or after) the parallel hard-standing at the side of the 02 runway.

We pulled all the way up passed the displaced threshold, along with an Extra and 1 other, who did their checks on the hard-standing to one side of the runway.

But enough, of this personal chit chat, that is perhaps better in a private message.

I rather hoped that you were going to offer me the benefit of your thoughts now that I had explained in some detail why I

whipped the gear up

yesterday. Do you disagree with the strategy, what is your suggested approach?

[Timothy]

2

Maybe I am a little more pessimistic than you (though I know that you are a very careful and thoughtful pilot.)

If I got an engine failure in the Aztec below 200' I would put it back down if possible. I agree that there are many factors which make it impossible, such as fog, houses and cliffs, but in the N Weald case yesterday I used the full length (including displaced threshold), rotated slow, climbed at blue line and, if I had had an engine failure, would definitely have put it back on the remaining runway, gone over the end, into a ditch at twenty knots, got out, run away, called the wife then the insurance company.

However, I have huge respect for your knowledge and skill, and, in all seriousness do not question that you take the opposite view in what is a very marginal decision!

W

[2Donkeys]

You are right that it is marginal. Sufficiently so that I did the maths on your "put it down below 200 feet" line of thought.

Leaving aside the very different flight characteristics of the Aztec, the calculation to consider first off for the 421C is where you will be over the ground at 200 feet.

So, I roll, and avoiding the anal arguments about book performance versus real life for a moment, let us imagine that at 50 feet AGL I will have moved 2250 feet down the runway.

My climb speed is around 110 knots (best rate all engines) at which with 36" and 1900RPM gives an initial climb leaving the runway of about 1000 fpm (assuming gear left down, which builds as I clean up to 1600-1700 fpm". *Very* roughly, my time to climb from 50 to 200 feet is 9 seconds, during which I will have travelled another 1500 feet.

Total movement along the runway at 200 feet AGL is then 3750 feet. If I abort at that point, I will not trickle off the end of the 6300 foot runway, I will shoot off it at very high speed.

I would accept that a 50 foot abort might just work, but since I reach 50 feet within 3 seconds of leaving the ground, and the gear takes 4 seconds to retract after that, it is something of a moot point in my opinion.

Interesting discussion.

[Timothy]

2

I agree that the 200' case would end up in a field, not on the runway, hence the emphasis on farmland versus town. I raise the gear when I cannot get back on the runway (typically 50-100'). Thereafter, if I had a left failure I would probably land wheels up in a field, with a right failure wheels down, depending on how long it took to get to the scene of the crash.

On another slight digression. I used to fly Perf A a lot, now sadly not at all. You are just starting to do a significant amount of Perf A and Rumbo seems to require Perf A*++. I think that it is important for us all to remember that your 421 and my Aztec are nothing at all like Perf A, and that we must not be suckered into continuing when the book either says we shouldn't or gives us no information.

W

[2Donkeys]

I agree that the 200' case would end up in a field, not on the runway

Perhaps as a closing comment on this thread (for me at least!) I would take you back to my original comments

Whilst neither the Aztec nor the 421 are anything like Perf A aircraft, they are sufficiently different in their flying characteristics and runway requirements not to be able to apply a one-size-fits-all reasoning to them. Whereas in the Aztec, the take-off roll and speeds involved are both relatively low, permitting you to conclude that an abort onto the runway from 200 feet is not life-threatening, the same abort in the faster, heavier 421 will put you into the very same ditch at the end of the runway at speeds that could well prove fatal. If there were to be an abort ahead option in the 421, either the runway has to be proportionately longer than for the Aztec, or the maximum height at which the abort remains possible becomes lower. That much is simply a matter of physics. Given the speeds and lengths involved at North Weald, you probably have with 02 a classic case of a runway which divides the decision between the two types. Were we both sitting on 27L at LHR, I would be right there beside you having aborted at 200 feet (actually I would be 1500 feet or more in front of you, but still on the runway)

As for perf A versus our mere aircraft, you are absolutely right. Handling an engine failure at the critical moment in a light twin is not an "easy" proposition on take-off, and one of the most important things to be equiped with is a clear plan as to what you are going to do. When the donkey goes bang is the not the time to scratch your head and wonder which option to take.

[Chuck Ellsworth]

Hmmm....

This is getting to be quite a discussion.

When we depart any runway or other takeoff surface we very carefully examine the useable rwy and the departure path that is available.

On multi engine airplanes I rotate - accelerate if necessary and once positive rate of climb is identified I retract the gear. If the first officer is flying he will do the same.

To leave the gear hanging in the airflow at such a critical segment of flight as the early stages of the climb is counter productive and can and probably will produce some very demanding flying due to the rapid loss of a/s due to high profile drag of the gear. Should a loss of an engine occur I fly the airplane straight ahead and we identify why the thing quit, we then find a solution to the problem such as feather. Most piston engine twin engine airplanes will have "some " climb ability with an engine feathered and everything cleaned up, most will not be controllable with the gear hanging in the first segment of the climb.

Note:

Should you decide to land on the remaining runway / grass or whatever you have far better braking power with the gear up.

Speaking of North Weald, I had an interesting experience there in July of 2001. On the initial test flight of the PBY with the depth charges mounted and quite a lot of movie gear on board and a vicious x/wind I was quite suprised at the loss of performance caused by the added drag of the depth charges hanging under the wings.

Once we started the filming flights and we were at all up gross weight an engine failure with the depth charges hanging out in the airflow after take off east bound could very well of have had me operating the biggest tree shredding machine on the British isles. :D :D

Cat Driver:

:D The hardest thing about flying is knowing when to say no.:D

[bluskis]

Chuck,

I would always bow to your great experience, but I do believe that while raising the gear on achieving positive rate of climb would be absolutely the correct procedure in instrument conditions, in VMC and with a small twin and a large airport the option to land back on should not be prematurely discarded.



Why do I only see my spelling mistakes after submitting a post?

[Chuck Ellsworth]

Bluskis:

There are few difinitive things in flying, of course there would be sitiuations where one may elect to leave the gear down on very long runways.

Just remember your best friend in an engine failure after take off is inertia, and that goes to hell in a hurry with the gear down.

But I will agree there could be cases where one could wait to select gear up.

It is a very seldom avaliable option for me though. Generally I fly a profile that gives best performance.


Cat Driver:

[bluskis]

In answer to the question about differences in critical and non critical engine performance,

Aztec D handbook : min controllable single engine speed 80mph

Notes from an ancient twin training exercise: two people no baggage, prob half fuel,

Aztec D: min controllable left engine only 72mph
right engine only 68 mph

[Chuck Ellsworth]

Caution:

Caution:

Caution:

When reading performance stats you must bear in mind that there will be many factors that will skew these numbers.

Here is a logical question to mull around in your thoughts.

The performance number is lets say 72 MPH.
Question:

How many MPH is the thickness of your airspeed needle?

Having answered that how many of us can hold the airspeed to the thickness of the needle?

In otherwords always take these numbers with a grain of salt and use common sense.

Cat Driver:



:D The hardest thing about flying is knowing when to say no.:D

[Keef]

Good grief! Reading all this makes me very glad I don't fly a twin. Sounds like they are quite exceptionally dangerous things.

I keep my single-engined aeroplane wheels down until there's no chance of landing back on the runway, and usually until there's time to get them back down again if the engine stops. Then I raise them.

So much easier. For those who fly tens rather than hundreds of hours a year, that seems preferable. If I inherit a fortune and can afford to fly many hours a week, maybe, just maybe...

No, there are other things I'd rather spend it on.

[Timothy]

Keef

It's a bit like the Hare that never overtakes the Tortoise.

Twins are a problem for about 10-15 secs per flight, for the rest of the time they are safer than singles.

The thing is that we tend to dwell on those 15 secs.

But if you feel safer in yer arrer, that's fine!

W

[Keef]

Ain't that the truth! I don't fly enough hours to have much hope of keeping asymmetric skills honed to the level I'd need. The arrer does the job nicely, cheaply, and with minimal fear.

Anyway, like I said, I've had my engine failure already... :)

[slim_slag]

WCollins,

This interesting NTSB Statistical Summary (http://www.ntsb.gov/publictn/2000/ARG0001.pdf) of General Aviation accidents includes accident rates for single and multi piston engine planes.

In 1997 (latest year available) the accident rate per 100,000 aircraft hours flown were

Single: 8.06
Multi: 6.36

So singles had more accidents, but for Fatal accidents the figures were

Single: 1.47
Multi: 1.92

So multis had more fatal accidents. Whether these are significantly different is not stated.

Yep, even if you are well trained you can get into a lot of trouble in those first fifteen seconds of flying a multi. If you are not well trained you can get into a lot more trouble in a multi than a single during the rest of the flight.

[Timothy]

Slim_Slag

These are oft-repeated boring chesnuts, but, as I am sure you know, the mission profile for twins in terms of weather, terrain etc is considerably different from singles.

Most people who consistently fly in poor weather, over sea, at night, over mountains etc are sensible enough to do so in a twin.

If, heaven forbid, it was normal to do these things in SEPs the figures would be much different.

IMHO

W

[2Donkeys]

On that self-same subject of boring old chesnuts, it can only be a matter of time before somebody suggests that engine failures in twins are more common than in singles.

Looking at that "fact", it has to be remembered that the pilot of a MEP is trained to shut an engine down and continue whenever he sees a condition such as low oil pressure or astromical oil temperature. In an SEP, your best option is to press on, and hope that nothing fails before you find somewhere to put down.

[slim_slag]

The problem with "oft repeated boring chestnuts" is that they get repeated so often they pass into folklore, and nobody remembers whether they are based upon fact or just another story told over a case of beer at a hangar party :)

Round here plenty (in fact the vast majority, twins are expensive to run) of people fly SEPs for the missions described above and the figures are what they are. Ok, lets get back to the numbers and look at total/partial engine failures due to mechanical causes - and I assume at the end of the day this is what causes SEPs to be a riskier proposition for flights than MEPs.

Around 6% of accidents are caused by total or partial engine failure of mechanical cause (Chart 8).

More importantly, 2.5% of fatal accidents are caused by total or partial engine failure of mechanical cause (Chart 9). In my opinion that's not much, and given the number of flights that are safely completed every day just goes to show how incredibly reliable engines are. I'd even bet that most of those failures are due to poor maintanance so have a human element.

Of course I'm now making the mistake of using selected figures in the report to back up my hypothesis that piston singles are no more dangerous than piston twins. If we are not careful it won't be long before that become another oft repeated chestnut. :)

[rustle]

For my better understanding, do BFRs for multi-pilots under FAA regs have to be completed in multis?

I am trying to understand if, once I have my FAA MEP rating, I am ever/regularly compelled to be re-examined in a twin.

TIA

[Final 3 Greens]

W Collins/Slim Slag

There are lies, damned lies and statistics!

In risk evaluation, one needs to consider severity and probability as a system.

Thus whilst the probability of a problem may be higher in SEPs, we might also agree that the severity is lower, due for example to lower glide speeds, lower weights and easier diagnosis of cause/effect etc.

I fly as a pax on airliners regularly, knowing full well that severity could be very high, but probability is very low, not least due to the risk avoidance and mitigation embedded in airline SOPs. Does this mean that airliners are potentially more dangerous than light aircraft? (not in the view of the average person in the street I bet!)

So it all depends on how you view severity and probability :D

Until someone does the exercise fully and models the variations of mission, pilot ability etc and then calculates the standard deviation against a normal distribution curve, I suspect the SEP vs MEP safety argument will tend to reflect subjective views!

Interesting thread.

[2Donkeys]

rustle asked:

For my better understanding, do BFRs for multi-pilots under FAA regs have to be completed in multis?

The answer is no. A BFR conducted in a single will cover you for your MEP, unless it is large enough to require a type rating.

Interesting eh?

[rustle]

2Donkeys

The answer is no. A BFR conducted in a single will cover you for your MEP, unless it is large enough to require a type rating

Thanks - I had read that somewhere, but needed clarification.

The story I heard was that, because it's cheaper to hire an SEP than an MEP, non-owners are more likely to (FAA) BFR in an SEP...

We (CAA/JAA) don't have the choice, obviously, with the mandatory 12 month MEP renewal in an MEP.

So, for sake of statistics, we really need to compare CAA/JAA stats against the NTSB ones to see if there's a trend.

[bluskis]

we need to cmpare a lot more than just that.

The figures look very different if you consider the average GS of a single at 110kts and a twin at 160kts.

The accident rates then ratio at .0727 for singles
.0397 for twins

and fatals ratio at .0133 for singles
.012 for twins.

That assumes the fatals are crashes not victims.

Twins fly for distance, singles often fly circuits or very local area, often with mega hour instructors in them.

Singles often break landing gear due to low hour piloting, twins often have undercarriage problems.

In my experience engines are anything but reliable, and it is impossible to eliminate the manufacturers design weaknesses or poor maintenance from GA.

As always it depends what you want to prove with the statistics.

[rustle]

bluskis

As always it depends what you want to prove with the statistics

Exactly :)

I believe that 87% of statistics are utterly unreliable, 47.33% are actually very useful indicators, but 10 well trained monkeys might have a different view :D

My (only) point was that, even in the statistics game, comparing bananas against oranges isn't allowed ;)

[slim_slag]

Bluskis,

I agree totally, what do you want to prove? And I have no idea where you are going with your average groundspeed logic :)

To prove this point, I think engines are incredibly reliable, you don't. How do I prove this.

I say this because I don't know anybody who has had an engine failure recently in a single (I do in a twin, killed three people, but that was maintainace and a stupid pilot who killed a few others with himself). I know a lot crusty old crop sprayers and freight dogs who had one or two engine failures back in the old days, but not recently. I know a few owners of flying schools who put a lot of hours on their planes, and none have had an engine failure. One had a cracked cylinder head once, but that was caught in time. Give me a few beers and I could really make this sound convincing!

But this is all anecdotal and worth nothing, one of these old chestunts.

Lets have a look at the figures from the same report I cited earlier. In Highlights (Page 1) it says that light piston singles have 8.06 accidents per 100,000 hours, and 1.47 fatal accidents per 100,000 hours.

Same doc says 6% of accidents are caused my mechanical failure

So taking accidents:

8.06 x 0.06 = 0.48 which I round to 0.5 accidents per 100,000 hours caused by mech failure. Thats one accident per 200,000 flying hours. At 100 logged hours per year, you would have an accident every 2000 years.

Doc says 2.5% of fatalities are caused by mechanical failure.

So taking fatal accidents

1.47 x 0.025 = 0.036 FATAL accidents per 100,000 hours caused by mech failure. Thats one accident per 2.75 million hours flown. You would need to log 100 hours per year for close to 30,000 years to be killed by your engine.

I think that's reliable! Probably in the same league as flying an airline (but of course engine failures there are even less common).

And as the argument that singles are more dangerous than twins is based upon engine reliability, I think it's a bum argument.

So what do you think flying3greens, lies or statistics? :)

[rustle]

Slim

And I have no idea where you are going with your average groundspeed logic

Guessing here, but I would imagine bluskis has converted the hours into distance, and then created stats based on miles flown, rather than hours flown... "Passenger miles"

[bluskis]

Russ
Good guess, sorry I did not make it clearer.

Slim
I was trying to prove

1. You can prove anything with stastics.
2. If you want anything useful from statistics you need to do a little work.

As far as engine reliability is concerned I have just run thru a list of occurrences 17 Sept01 to 12 Nov01. The dates are old because it is the list I have to hand.

In these two months there were 20 incidents of engine problems on G reg light aircraft. They resulted in safe landings, pan calls, maydays, forced landings, aircraft severely damaged, and a ditching.

In the last incident the pilot told me he did not intend to fly a single over water again.

I personally have experienced engine problems on average at least every 300 hours.

The only point I am trying to make with these statistics is that it is a disservice to those who may not yet have had engine failure to lead them to believe it won't happen.

It is better that they are aware that it can happen and prepare for when it does.

[Final 3 Greens]

Slim Slag

As you asked :D

I think that your logic is based on a confidence level of 100% - i.e. you are 100% confident that you would be killed after logging 100 hrs pa for 30K years (which given the human lifespan is interesting!), but you don't consider the individual engine lifecycle in your argument.

The mean time between failure for a typical engine is not 100 x 30K, so what is a reasonable confidence level for a typical engine?

Let's just assume for a minute that a notional engine has a TBO of 2000 hrs

Let's say, for sake of argument, that the engine is most likely to fail at 2000hrs, but that it might fail at as little as 1000hrs - failure at more than 2000 is also possible.

I just made these numbers up BTW, to illustrate how probability works and in the real world the engine could fail at any point due to the factors that Bluskis mentions and others.

Apply this to a normal distribution curve and we can have 98% confidence that the engine will have failed by 2860 hours (since 98% confidence is represented by 2 standard deviations, or 860 hours)

However, looking the other way, we can also be 98% confident that the engine will not have failed by just under 1200hrs.

So the numbers say that if we don't fly a/c with engines in the 1200-3000 hour range, we are pretty safe (<2% confidence of failure.)

However, this is based on running 40,000 iterations of the model through a 'Monte Carlo' simulation engine, which smooths out the randomness of the event over a very large scale sample.

Also, if you apply a triangular distribution, for example because you have reason to believe that the engine will be likely to fail at the higher, rather than the lower end of the range, you will get different answers.

If you were a fleet manager running 40,000 SEPs, acquired with with brand new engines at the same time and kept until 1200hrs, then likely you wouldn't be much worried about the odd random event when you lost a hull, because over such a big sample, you'd lose 2% of your fleet and insurance would cover that! At 800 hulls lost per 48 million hours flown or 1 engine failure every 60 000 hours, you say that SEPs were pretty safe.

But in the real world, the experience of individuals will be very different because they are a sample of one, not statistically significant and much more vulnerable to the impact of random events (i.e. the '**** happens' experience), thus creating a broad range of different experiences. When a sample of one crashes that's pretty significant to the sample of one.

Bluskis says "I personally have experienced engine problems on average at least every 300 hours."

I flew a Pup one weekend back in the 90s and it suffered catastrophic engine failure on take off a few days after with another pilot who forced landed safely, but in my 220 hrs I have not directly experienced a failure.

Your experience is different again.

So to answer your reasonable question, your statistics are neither lies, nor damned lies, but rather data to consider very carefully. Do you feel lucky today? :D

On balance, it's hard to argue with Bluskis view that "It is better that they are aware that it can happen (engine failure) and prepare for when it does."

One thing for sure, me flying a MEP is much more dangerous than an SEP, due to lack of experience and currency - that is unless the light single kills me first! ;)

[slim_slag]

3greens,

Thankyou for your excellent answer to my question, it certainly demonstrates an understanding of the use of statistics - and my question :)

I don't think statistics can lie except if the data or question being asked is faulty, but you cannot blame stats for that. Statistics will actually tell you if the data being worked on is good enough to answer the question being asked. I think if you have sufficient data, you can explain everything with stats. Quantum mechanics scares me!

Yes, training can turn a fatality into an accident, an accident into an incident, and incidents into a safe flight. The NTSB figures show fatalities due to engine failure are dropping, but don't suggest a cause. One can only surmise that training has a lot to do with it.

As for engines. Make sure you have enough oil and fuel, understand the use of carb heat and mixture and you can save a lot of death from engine failures. There you go, simple eh? For engine failures in multis around take off, make sure you have high quality recurrent training in a sim. Not so simple, but it's what the airlines do. Most engine failures are human caused, engines are very very reliable (as my simple non statistical analysis proved). Not so for humans.

So how does bluskis manage to encounter a problem "on average" every 300 hours. Depends what a "problem" is of course, but are you flying a homebuilt with a subaru conversion? I think a problem "on average" every 300 hours is a problem itself (but stats will answer the question definitively). Actually, if it happened to me "on average", I would be concerned.

I have found fouled plugs on the ground which make me taxi back far more frequently than that, and it is training helps me recognise it. I also don't even elevate that to incident or problem. It's also "probably" training related, the person before needs to understand use of mixture, or a mechanic did something wrong.

From the data I cited, and it is a very large sample from an excellent source, I think you can get a "p" number which will indicate whether singles are more dangerous than a multi. I'd do it, but cannot remember how. Somebody has done this and claims that statistics prove singles are safer.

Aviation Safety Study (http://www.kelner.com/safety.html)

I've emailed a request for the report. Doubtless there are experts here who have already crunched the numbers and already know the answer. Insurance company quotes would appear to suggest high performance singles are safer than twins, and lots of multi time and training in a respected environment is the only thing you can do to get the quote down. Which luckily takes us back to the subject of the thread.

Regards

[Final 3 Greens]

Slim Slag

I'll give you a better reply than this tomorrow, but regarding stats, there are two factors you should consider.... (a) accuracy and (b) validity.

Accuracy is a given - inaccruate stats are of no use to anyone.

However validity is a bit tricky.... accurate numbers can be invalid if used inappropriately, so we must always think carefully about the stats we're using and what they mean.

[Timothy]

2, Rustle

It turns out that there was a third explanation ;)

The Aztec is in for C of A and apparently the left engine had zero compression on two pots!

There is always an answer.

W

[bluskis]

SS

To put your mind at rest as to the accuracy of my personal stats.

Con rod through the crank case over water, engine definitely stopped. Single engine, landed sucessfully on terra firma.

Engine coughing and low on power after flight over 250 miles of sea, ignition system problems. Single.

Engine bleeding massive amount of oil, engine shut down and diversion to nearest field. Twin.

Increase of engine power unobtainable on approach, approach continued on one engine. Throttle cable anchorage bracket adrift following engine overhaul and CofA. Twin.

The figures of engine based occourances you can obtain regularly together with Flight Safety magazine, and the CAA will probably have figures of total hours flown by GA. When you have done the arithmetic I am sure you will come up with a small figure.

I am now not sure what point you are trying to make, but to assert that engines, together with the mandatory maintenance, are reliable does not stand up.

Right now there are considerable numbers of GA aircraft grounded by AN's concerning engine components.

Please note I have not voiced my opinion on this thread of the relative safety of singles and twins, merely tried to correct what I believe to be a dangerously misleading opinion on engine reliability.

The posters who have pointed out the necessity of relating small probability and severity of consequence have it right.

[rustle]

WCollins

"...apparently the left engine had zero compression on two pots"

Um, unless the engineer was referring to "left" when viewed from the pointy end as opposed to the traditional "left", that doesn't aid my understanding.

We failed the (real) left :p

[Timothy]

Rustle

Ah yes...but I misidentified it....doesn't that count?:o

W

[slim_slag]

Hi Bluskis,

I guess our experiences differ, but thats OK. What you and I think due to our individial experiences doesn't matter much.

Google is such a marvellous thing, I found this NASA GA Reliability Report (http://techreports.larc.nasa.gov/ltrs/PDF/2001/cr/NASA-2001-cr210647.pdf) which attempts to give some figures.

Most of this is over my head, but it looks good :D and as long as the source looks authoritative I always go straight to the conclusions anyway.

Page 34 says:



System reliability estimates are based on the probability that a Complex GA Aircraft Airframe System will successfully complete a 700 nautical mile six-hour flight.

The system reliability estimates are determined to be:
Airframe 0.99940
Electrical 0.99997
Powerplant 0.99986
Flight Control 0.98476
Ground Control 0.99598
Cockpit Instrumentation 0.976


So my understanding - which may be wrong, I am no stats whizz kid - is that you have a 99.986% probability of completing the 6 hour flight without an engine failure. I call that reliable, you don't. No problemo! What I did find surprising is the engine is more reliable than the airframe, I would never have got that - see how my individual experience is not worth much.

For a 100 hour a year pilot, 0.99986 ^ 16 = 99.77% of completing a year without an engine failure. That's a risk I am prepared to take.

What chance have you of having a problem after 300 hours, your experience?

0.99986 ^ 50 = 99.35 chance of getting through your 300 hours unscathed. This is extremely unlikely, to have this "on average", which implies more than once, is getting into very small numbers indeed.

You can put the figures in for a 1000 hour a year instructor (98% and I would be prepared to take that risk because I know that only a small percentage of engine failures result in injury due to training). A very busy 20000 hours a year flight school has 63% chance of getting through the year unscathed.

And if my figures don't exactly work out because not all flights are 6 hours long I don't care! It's close enough for me! So now we are getting some real statistically based numbers, let the GA SEP pilot make their own decision.

Regards

[Final 3 Greens]

Slim

The posters who have pointed out the necessity of relating small probability and severity of consequence have it right.

This is the key. I live next door to an 18,000 hour plus ATPL who has never had an engine failure.

Bluskis has had some hairy moments.

You are looking at numbers across a huge sample and all you are seeing is the result of a normal distribution - 98% of the variance will be contained in 2 standard deviations.

If the other 2% doesn't concern you, then you have established a persoanl risk tolerance that is usable.

But it doesn't alter the probability/severity relationship :)

[slim_slag]

F3G,

I think we all agree that at the end of the day life is all about risk/reward ratios, and it would be nice for these decisions to be based upon fact.

So given the "real" statistics from the NASA report, do you think piston engines are reliable?

[bluskis]

SS

As I said in a previous post, if you want to make good use of statistics you have to be prepared to do some work.

The statisics you refer to from NASA do not include the following, but when you fly your aeroplane they are surely included:

Human induced failures
Failure due to mechanics poor skills/procedures
Failure due to improper parts.

There are many other exclusions in the data as specified on page 11 of the document.

I am quite happy for you to make your own risk appraisal, as you are for me. The problem is others may make a risk analysis of their own based on this thread.

[slim_slag]

The problem is others may make a risk analysis of their own based on this thread.

Well bluskis, I don't think I would take much notice of what you and I have said, but I'd certainly take notice of what NASA and NTSB say. I think the best thing to do in this situation is cite authoritative sources and let them make their own minds up.

Regards

[Final 3 Greens]

Slim Slag

There are no 'definitive' facts about engine reliability as applying to an individual, just a set of stats that allow a post hoc analysis and some regression analysis. You will find that probability will work over a big sample, but to the individual the severity of impact will be as critical and the decision will revolve around one's view on that.

Bottom line, risk/reward decisions are made on perception of the upside/downside equations, e.g. look at the FTSE 100 everyday. As the disclaimers say, past performance is no guarantee of future performance.

That's as good as it gets and trying to fit the stats to this discussions is the equivalent of using Procrustes' bed in Greek antiquarian literature - you will get the answer you seek, but it doesn't mean that it's valid.

I think you're barking up the wrong tree here - there is not a definitive answer to your question, too may qualitative variables are involved.

If you think that piston engines are reliable and that singles are safer for twins, then for you they are.

[slim_slag]

F3G,

Unfortunately I have to sit inside and monitor some systems today, the bad side is I cannot fly, the good side is I get to monitor PPRune :D

I admit to being confused. Are you saying the statement "Flying in light aircraft is safer than flying in public transport wide bodied jets" is correct? I know it is if you get killed in a 737 crash, but lets talk in general terms that the general public (i.e. me) understands.

Edited

Hey you know what F3G, you don't need to answer that. I've got a lot out of this thread, I am glad to have found that NASA report, and am happy with the fact I now have numeric figures which quantify the risks involved in flying SEP. That's more that I knew yesterday.

So cheers

Slag

[rustle]

bluskis

The problem is others may make a risk analysis of their own based on this thread.
Not if they followed the thread to the end, and share this philosophy (thanks slim_slag :)):

"I've got a lot out of this thread,... That's more that I knew yesterday"

[Final 3 Greens]

Slim Slag

I will answer...

Flying in light aircraft is safer than flying in public transport wide bodied jets [Is this true]

No it is not - flying in public transport wide bodied jets is statistically much safer than flying in GA aircraft.

The reasons for this include Airline SOPS, two crew ops, higher standards of crew performance attained through training and recurrent training, more capable aircraft, more systems redundancy, more % of the flight spent in the cruise (a phase statistically less likely to experience serious incidents), operating in and out of airports with better approach aids, very high standards of maintenance funded by mega budgets, scrutiny by regulatory authorities, etc.

However, comparing the sample known as "public transport wide bodied jets" which has highly defined and controlled parameters, with the sample known as "GA aircraft" is a skewed comparison that will favout the jets sample.

The GA sample has broader, less defined parameters since it incorporates a far wider range of activities - e.g. private flying of many different missions, air taxi, corporate aircraft, crop spraying, missionary work etc.

For this reason, the 'public transport wide bodied jet' sample will provide less volatile data and the probability will say that it is safer. (Smaller standard deviation being the indicator.)

The point I made earlier about the linkage between very low probability and serverity is more about one's personal (qualitative) view of risks, so let me explain it again as you seem to be confused.

If you fly on a public transport wide bodied jet, the probability of a serious incident is very, very, very (etc) low. If you do have a serious incident leading to a crash or forced landing, the potential severity is very high. (Even this is not a 100% certainty though, as the A330 that made a forced landing without power in the Azores with only minor consequences demonstrates.)

It is this linkage that determines whether you think that flying is safe. The general public seem to think that the risks are acceptable if you look at the numbers who take flights, you even get some nervious pax who are scared by the potential consequences, but think it is very unlikely to happen to them - so travel.

Risk versus reward must be a subjective view when you think about it, since risks are always in the future and can only be quantitatively analysed once they have developed into historical record.

If you would like to understand statistics better, I recommend my clients to read 'Statistics for the utterly confused', by Lloyd Jaisingh which can be found at Amazon. (Note to BRL, I'm not advertising, have no personal interest :) )

[slim_slag]

i really shouldn't but.. F3G my intelligent friend, I admit to being confused. And seeing as I know how many standard deviations my IQ is from the mean, I suspect others are too (please don't tell me how IQ means nothing, but by all means tell me I am an arrogant git :) ).

Let me suggest that at the end of the day, when faced with a problem like this, all us general public want to know are simple numbers we can get our heads around. We don't care about regression and standard deviations and the like. If you can put a simple figure on a problem then you have got us cracked. I found a figure - I did not make it up myself, I got it from a NASA paper entitled "General Aviation Aircraft Reliability Study". Well, that sounds pretty much like what I am looking for and I trust that source. I am open mined though, and will accept the result even if I don't like it.

The NASA paper said you have a 0.9999 (rounded) chance of completing a 6 hour SEP flight with your engine intact. For the statisticians amongst you, there was even a statistical analysis with all sorts of long terms and Greek characters in it. This number was good enough for NASA to publish it.

I ignored the Greek characters and looked at the number in the summary. The number has a lot of nines in it, one hell of a lot of nines in it, and that's good enough for me. That many nines sounds really good, it gives me a warm and fuzzy feeling (something you are going to have trouble quantifying with your stats, but I know what it means) Sure, it doesn't take into account the fact you may be hit by a meteorite which will rip your engine off its mount, but for me as a simple member of the public that doesn't matter. I call that an act of God, it is so unlikely I exclude it. OK, so you don't and you argue against the whole result because of that - but for the sake of my argument lets take a nine off the end of the NASA figure. What do we have left? One hell of a lot of nines.

So let the user read the reports and decide for themselves. I was out talking with members of the public last night and gave them the number with a lot of nines in it. All were very impressed and surprised how reliable SEP engines are. I suspect (and that is a wooly term but I throw it in anyway, I just love to live on the edge :) ) that most others will be impressed too.

Regards

Slag

While I am on this rant, let me throw out another simple number which may help put things in perspective for non statisticians.

When you go see your GP for a medicine, or your cardiologist for a surgical intervention, the medicine or procedure SHOULD be better than sugar pills or doing nothing. How is this known? A question is asked, research is done and statistics applied to the data. To get a drug/procedure approved, you need to show it is effective, but the cut off point that it is due to chance is 5%. I.e only being 95% certain it works is good enough for medicine.

Therefore when you take your drug (with side effects, possibly fatal) or have a surgical procedure (with side effects, possibly fatal), this is done to you with only one nine!

NASA give you four nines, and remember these nines are harder to get the more you have. So those of you who are happy to have a surgeon hack at you, just HAVE to be happy with flying SEP.

And I await the incoming missiles for that! :D

[bluskis]

SS

I had not intended to add any more to this diverted thread, however I would ask you to look again at page 11 of the NASA report you are putting so much faith in, and there you will find what they actually measured, or rather did not measure.

I think you will find the report is somewhat more restricted than you apparently believe.

How these restrictions would change the figures of the report I am unable to guess, but change them they will.

[slim_slag]

Bluskis,

You are repeating yourself! If you were to read what I said on this engine failure related thread you would see I have always talked about "mechanical" engine failures. Pilots are the sort of people who happily take responsibility for themselves, and through training can minimise human engine failures. It's the mechanical things, like crank shafts snapping, that we cannot directly control. When you talk to pilots that is what is perceived to be the risk.

There is something you have totally missed here. If you claim to see "engine problems on average every 300 hours" the NASA report should be ringing alarm bells in your head. The NASA report shows (to my satisfaction if not yours) that non human induced engine failures (which is what it is measuring as you like to point out) are infrequent. According to NASA figures, there is a 99.35% chance that you will routinely complete 300 hours of flying SEPs on 6 hour legs, yet you seem to see problems regularly.

What does that tell you? The only explantion I can come up with (apart from you are making it up) is that you are seeing a serious problem with human induced engine failures. Some people need training, in fact from what you are saying the whole system is falling apart.

Personally I doubt that is the case, there is another more obvious explanation.

Cheers

Slag

[Timothy]

I have to add my name to he who who posted earlier that he had experienced shedloads of failures.

I have had eight or nine power failures (depending on what you count, the ninth was a fuel pump failure and was rectified by changing tank and switching on the electric)

These eight have included two on jets (both fracture failures of a turbine discs) one of oil being shed everywhere, one CSU failure, three mag/ignition failures and one fuel to engine failure (either carb or injection, I forget which it is on the TB10).

I have additionally had two instances where engine indications have led me to (1) abort take-off (2) shut down an engine and land, but both turned out to be indicator failures.

The irony is that the only two which entailed mechanical breaking of a moving part were both jets (my hours are roughly 30% on jets the rest on pistons.) The oil one turned out to be a ground engineer not replacing the oil filler cap on turnaround, the rest are all failures of ancilliaries; but the effect was the same: either total or near total loss of power.

So I wonder if this is the nub of the differences being expressed here. Maybe pots only break out from crankcases, or crankshafts fail, once in in a thousand lifetimes, but maybe engines stop for other, non-pilot-error, reasons far more often?

My planning for engine failure would cover all cases, hence my personal decision to fly only with a spare!

W

[Final 3 Greens]

WCollins

A point well made.

I once had a couple of spark plugs fail in a light single climbing out of Southend on a night sortie.

Not even an engine 'failure' as such, but it altered the way I thought about night flying, due to the realisation that it could happen to me.

Slim Slag

A litte question for you to ponder about your NASA survey.

How many SEPs can manage 6 hour sectors with legal reserves?

[bluskis]

SS has finally seen the point.

The NASA report was concerned only with design and manufacture reliability.

The figures would be somewhat different now with the recent Lycombing related fatalities, and grounding fiasco.

Like WC, these three problems I had were 'mechanics skill/procedure' related.

Definitely not covered by the report.

The fourth was magneto related, so could have been in either the manufacture/ design camp or the mechanics camp.

W C

Could you post how many hours per failure your experiences would average.

[Timothy]

Bluskis
Two jet failures in approximately 1000 hours of jets

Six piston failures in approximately 2000 hours of piston, of which half SEP half MEP, so you could say in 3000 hours of piston engine operation.

But, as we keep saying, that's just one set of anecdotal experience; we have just heard of the 18,000 hour guy who's never had an engine failure. I imagine that both his and my experiences are in the tails of the normal distribution.

I used to think that people flew singles until they had their first engine failure, then they moved to twins, but I now know this to be rubbish. Keef still flies his Arrer despite his near-death experience (though I do acknowledge that near-death isn't so worrying for a deeply religious person :D ) and I recently was talking to someone who flies old stuff (Moths and Percivals) who considers engine failures normal operation to be dealt with as they arise.

Also one cannot say too often that the SEP failure is a different beastie from the MEP shutdown. Often the MEP pilot will shut down an engine that an SEP pilot will struggle along with.

W

[Final 3 Greens]

WCollins

I imagine that both his and my experiences are in the tails of the normal distribution

I imagine that you are right in your assertion.

Of course when evaluating the probability of severe risks on an individual basis the wisest assumption is that you will be at the downside tail, unless you feel very lucky.

In consequence I agree with your earlier comment about planning broadly and Bluskis earlier comment about the value of being trained and current.

Slim Slag

I have just re-read your last posting - you should train as a sophist mate - you have the potential to become a modern day Protagoras :D

[Timothy]

F3G

I have just read some of that famous report.

The whole thing is an exercise in sophistry and obfuscation.

It is a fine example of how to lie with statistics. The size of sample is pathetically small and the conditions which are excluded make the whole exercise a waste of time from the point of view of estimating flight safety. :rolleyes:


I reckon that it is something to do with trying to reduce Product Liability cases.

At any rate I wouldn't base anything actuarial on it!

W

[Final 3 Greens]

WC

So you didn't like the report much :D

There seemed to be an itsy bitsy over representation of Mooneys (9 from a small sample of 33) and a desire (that I did not understand) to relate the numbers to a 6 hour mission, which strikes me as unusually long for an SEP, even in the States where some people do use them for business trips. In fact, I wonder how many of the types listed could legally file a 6 hour IFR (or even VFR) flight with a full pax load or even at gross weight with pax offloaded for fuel? I'd be very surprised if this list included the 152 and the 172 - some of the others might just do it with long range tanks, but not with me as P1! (not just for safety reasons either - how ling can the average middle aged bladder hold out for? :D)

I'd guess that the average sector for a single is about 1hr, maybe 90 mins. I haven't read the report methodology properly, but in the real world I'd expect less stress and strain on an engine flying 6 hour sectors (with a long cruise segment at stable air temperatures and power settings) - especially the turbo variety and this would impact on the reliability in itself, although to what degree I don't profess to have a view.

At the end of the day, I prepare for engine failure every time I fly and just hope I never have to demonstrate my 'superior' skills!