American Airlines Flight 742 "flight control system" problems

[Clandestino]

Originally Posted by DozyWannabe

True

False, DC-9 engines are not behind the wing, they are above and behind it. That any civil turbofan engine needs access to clear, undisturbed air to work properly and therefore cannot be protected from any flying FOD is hard scientific fact that cannot be altered by surrealist, dadaist or any similar art movement. Perhaps if we use cubist perspective, then indeed they are shielded by wing or fuselage or whatever but while cubist paintings brought fame and money to certain Spaniard, no draftsman that has drawn cubist blueprints has ever landed a job anywhere.

Seemingly in the race to air most implausible theory in this thread someone has conveniently overlooked that I have already mentioned catastrophic failure of western built low bypass engine following ingestion of geese but then I don't expect folks with very chivalrous attitude towards reality would know what Yukla27 was or would look it up.

Interestingly, for all the fuss about birdies here ASN lists only 56 events severe enough to be mentioned, most of them non-fatal, if we count only humans, that is.

[DozyWannabe]

@Clandestino:

You're right, but seeing as we're dealing with hypotheticals here, strictly speaking the difference in engine placement may make a difference, and I'm happy to give sevenstrokeroll the benefit of the doubt. That said, we're way outside the original topic and I'm beginning to wonder just what the point of this meandering is!

[bubbers44]

No, sully had a very good brain to put it down as professionaly as he dd.

[bubbers44]

Probably missed some but over 90% we saw by looking out the window.

[Capn Bloggs]

Originally Posted by Dozy

podded, wing-mounted engines...crucially in today's all-hydraulic airliners allow a greater degree of control through differential thrust than their tail-mounted counterparts.

"Crucially"? You're pulling my leg, surely! Are you seriously saying that this was a consideration in the placement of engines on the wings? Quite apart from the over-sensitive reaction to a tiny bit of asymmetric power, the pitching moment of underwing engines makes them far worse in a control-by-thrust scenario than tailmounts. Desk-jockey nonsense.

Originally Posted by Dozy

we're way outside the original topic and I'm beginning to wonder just what the point of this meandering is!

You can say that again!

[DozyWannabe]

Originally Posted by Capn Bloggs

"Crucially"? You're pulling my leg, surely! Are you seriously saying that this was a consideration in the placement of engines on the wings? Quite apart from the over-sensitive reaction to a tiny bit of asymmetric power, the pitching moment of underwing engines makes them far worse in a control-by-thrust scenario than tailmounts. Desk-jockey nonsense.

Think what you like, but I'm sure it was at least one of the considerations involved. Yes, podded engines mounted under the wing give a pitch-up moment, but there's no denying that as long as that is compensated for, one can get a greater effect on the yaw axis from engines mounted in that manner - it's just basic physics.

Of course, the main reason T-tails with fuselage-mounted engines went out of fashion was the inherent problems with deep stall in that design configuration, but other considerations were undoubtedly involved.

[Capn Bloggs]

Originally Posted by Dozy

Yes, podded engines mounted under the wing give a pitch-up moment, but there's no denying that as long as that is compensated for, one can get a greater effect on the yaw axis from engines mounted in that manner - it's just basic physics.

This is getting more ridiculous as time goes on. Why do you think you're using thrust vectoring? Because the normal flight controls don't work! You can't "compensate" for the pitchup if don't have any other means of pitch control. Oh hang on, we've got a totally jammed roll/rudder system but a controllable stab/elevator. OK, now I understand...

Originally Posted by Dozy

the main reason T-tails with fuselage-mounted engines went out of fashion was the inherent problems with deep stall in that design configuration, but other considerations were undoubtedly involved.

Designed right, it won't. The real reason was/is weight and balance.

[Clandestino]

Much of aviation has adopted the "Just Culture" so, as you say, it's about looking at the causes and lessons to be learnt

Correct. It useful too keep in mind that reason for applying just culture is purely pragmatic: it helps us to learn from others' mistakes that would be swept under rug in punitive culture and so makes flying safer. It is not there to cater for someone's increased sensibility and is definitively not get-out-of-jail-free card.

I'm not entirely sure that the recent trend of recruiting inexperienced crew has disproved the need for experience or, to be more accurate, a balanced recruitment policy.

I am afraid current aviation policies (not just recruitment) will eventually end up in disaster and when it happens, there will be plenty of old hands whose battle cry "More experience in cockpit!" will be picked up by politicians. IMHO it would be wrong.

The myth experience=quality comes from general aviation. As it is usual with myths, it begins with something substantially true but eventually a bit of embellishment and misapplication here and there gives us something useless for all practical purposes yet considered to be holy writ (e.g. stalling when turning downwind). In general aviation, unfortunately, experience is often the only way of acquiring skills and knowledge. It is not so in structured training environments where there is ample opportunity to teach pilot everything he needs to know and verify whether he is able to apply the learnt but what is extremely important and often overlooked, even before the training starts, air force or airline have the opportunity to select those brightest, aptest and the most motivated to eventually fill the seats. I think shrinking the candidates' pool is that's the area that will hurt us most in the long term. Western airlines are more and more laying training costs on individuals while offering pretty unattractive T&C so those most suited to become a pilots will be far better off in some other walk of life. Whether those who beat financial besides training obstacles and get installed into front seats will be good enough remains to be seen.

Aircraft are so reliable now that they can mask many of the pilots failings and its only when the unexpected happens that that lack of experience coupled with inadequate training comes home to roost.

'Tis an old cliche that flying is 99% of boredom punctuated by 1% of sheer terror and pilots are paid for coping with that 1%. Problem with idea that lack of experience causes accidents is that very old hands have flown their aeroplanes into mountains or were unable to perform simple task such as: if ASI doesn't work, reject takeoff. Also some pretty new pilots coped with emergencies successfully. While experience does make a better pilot, it is not always so and it isn't only way of making a good pilot. When proverbial hits the fan, pilot quickly needs to know what happened, what he needs to to and to perform it as perfectly as possible. With todays aeroplanes most failures are now not once-in-a-lifetime but once-in-20-lifetimes events so one has to learn from others' experience. Capt Sullenberger was very inexperienced in A320 ditching, which didn't prevent him from pulling it successfully the very first time he made it.

The lack of RHS experience also puts great pressure on the LHS occupant who flies with them day in day out.

Again, it is competence, not experience and I'd say enthusiasm towards work and flying is better indicator of one's capability than hours in logbook.

It's interesting to note that one LCC is changing its recruitment policy from one of cadets only to a cross section of backgrounds.

Being jaded cynic, I'd suggest it's because they couldn't find enough bodies to fill the seats.

Of course I'm wrong. They are fully committed to safety and all their policies and actions reflect so.

Of course in the old days we had much more opportunity to handle aircraft manually but we also tended to stuff it up,every now and then, and crash. So they increased automation and safety systems to address this

With idea we won't get tired of constantly fling and so will be fresh to takeover when George packs up so we can work longer and weirder hours. Also I blame the unions of yesteryear for not redirecting the pay of F/Es that were made redundant to pilots - after all we are now doing their job when all the automatic systems niceties fall apart.

That was okish because we had a background in the forces or came through the self improver route so we had a base of experience to fall back on.

Peacetime forces pilot is very desirable and very rare post so forces can be picky and choose those best suited for the job. It is oft the quality of raw material, not the experience that makes the difference. As for the self improvers, while they are mixed lot I admit most of them are maintaining strict self-discipline while having the holy grail of airline seat in sight. There are some things applicable to Pawnee that are useful in 320, there are some that are not. As long as one can tell which is which, he'll be fine.

The way LCCs have used the cadet system has changed that so its a double whammy

Exactly. Cadet scheme is generic term, we have to be careful to avoid painting everything with same brush.

We can only hope that the politicking stops and they address it properly. A naive hope I fear.

I am afraid that politicians of today have only two modes: passivity and panic reaction and I can't tell which one is worse.

[sevenstrokeroll]

WOW

first, why did I write "DIALS"? I wrote it because it rhymed with SKYLES, the copilot's name. What I meant is that there is more button pushing and head down time in a an airbus than older types.

And mounting engines on wings in pods...now I had more laughs out of this one than just about anything. Its more a structures thing than to use assymetric thrust for yaw or pitching. Oh and by the way, if you have engines on the wings you need more of a vertical fin/rudder.

And deep stalls have been mitigated by easy aerodynamic fixes like vortilons.

and once again clandestino does not understand an air molecule is different than a goose.

consider the goose, flying along thinking gooselike thoughts...hmm, look at the empenage on that gander and bam, gets sucked into an engine.

or

what is that big silver thing coming at me...bam hits the fuselage, or even better yet...oh, I'll dive below that big silver thing.

sorry clandestino, you are not accounting for other things than airflow....oh and I asked a question about airspeed/pitch at time of bird strike...still waiting for an answer on that one.
clandestino, the engine is not fully protected in a rear mounted plane...but even you, the master quoter must acknowledge that if the engine has nothing in front of it like on the 'bus there is NO chance of anything getting in the way of the bird, except the engine

and putting the engines on the tail at least gives a chance for a bird to hit something else than the engine first.

and that bit about a once in a lifetime event ...what skills did sully use in ditching the jet? wings level, maintain flying speed, touchdown ...oh yeah, we do that on most landings, don't we? sure if there is a X wind, we throw in some crab and maybe even wing low, tut, tut, the basic skills of any ditching are practiced on every flight.


as far as ''sucking ice'' and the JT8d. It wasn't ICE it was HAIL (although hail is frozen too). And I recall a TACA 737 with cfm's having to land on a levee and it only SUCKED RAIN.

The HAIL oblitered the windscreen too,making an off airport landing more difficult.

Sucking HAIL can be avoided by adjusting wx radar and knowing a possibility of hail exists.

[sevenstrokeroll]

oh, and the devotion to the DC9 is respect. After seeing the way the airbus has done, I have even more respect for the 9 than ever before...KISS.

oh and for those who don't know what KISS means, its Keep It Simple, Stupid.

[Owain Glyndwr]

Interestingly, for all the fuss about birdies here ASN lists only 56 events severe enough to be mentioned, most of them non-fatal, if we count only humans, that is

Just for the record, 21% of these were jet/turbofans on the wing, 34% rear engines and 45% propeller driven. Not much evidence there that rear engines are less susceptible to bird strike.

[Ashling]

Clandestino, a couple of thoughts

You are of course quite right, experience does not always equal quality just as inexperience does not always equal incompetence.

I was always amazed at just how quickly the RAF turned me from zero to hero (well perhaps not quite).

However as you also say they had their pick and it was/is a highly supervised environment even after you exit formal training which means that if you put the effort in you develop rapidly. If you don't put the effort in you tend to get binned or sidelined until you mend your ways.

Its about selecting the right people and giving them the right training and the right development and supervision when they are qualified. Sadly it would seem that some organisations may be more interested in ability to pay than they are in aptitude. This is especially true when the Loco's are demanding more pilots, the quality of the product gets diluted. I've certainly feel that I've seen a reduction in standard over the last 10 years or so. Certainly line training is much more stressfull as is sitting in the LHS.

In my view airlines training systems are not set up to develop large numbers of low hours pilots effectively. You can do it, just not with the current set up. It works ok for restricted numbers of high ability individuals though and thats why a balanced recruitment policy is still best in my view. It also good to have a variety of backgrounds as the whole thing tends to get a bit incestuous otherwise. The airline I referred to that is changing recruitment policy isn't doing it because there aren't enough cadets banging at the doors, far from it, its for other reasons but I'm not in the know so can only guess at why.

Experience doesn't solve everything but it helps and you are quite right to observe that the attitude of the individual is key. That is true at any stage. Much better an able, keen, hard working pup than someone with thousands of hours who does the minimum. However most do put the effort in.

Sully coped, in my view, because he was an able indidual who had a wealth of experience to fall back on. In the crucial seconds after they hit the birds he got all the big calls right and that set them up for a successfull outcome. I can only hope I could have done the same but equaly pray I never have to find out. I also believe that a number of the relatively inexperienced commanders we have would have coped just as well, some better. But for me if you had a 100 Sully's v 100 new ex cadet commanders in the same scenario the Sully's would have a significantly higher success rate. Sadly Sully's are a dying breed.

Whichever way we slice it, and I'm not pretending my view is the only/right one, we have a problem and have had for some time.

[bubbers44]

Clandestino, I don't think any airline has sop's on avoiding birds, they assume you will not run into other airplanes and birds when they hire you. You avoid other airplanes by looking out the window, just as missing birds and mountains. When you drive your car do you just stare ahead at your lane or do you check to make sure cross traffic isn't running a red light? I use the same techniques in an airplane to try not to hit anything. Remember that idiot in LA that tied balloons to his lawn chair and took to the skies? Now I even look for flying lawn chairs.

[sevenstrokeroll]

owain...how many of the rear mounted (western) jets had to ditch?

how many wing mounted had to ditch?


oh and clandestino, by your own statement, the engines on a 9 are above and behind the wing...wouldn't that be more bird resistant to birds approaching from the underwing angle vs wing mounted eng?and wouldn't that be more protective in a plane that is climbing and birds that are level?

[sevenstrokeroll]

I found the ASN report very interesting indeed...NONE of the incidents/accidents included DC9s. none.

[con-pilot]

owain...how many of the rear mounted (western) jets had to ditch?

I know of only one, had nothing to do with bird ingestion; ran out of fuel.

ASN Aircraft accident McDonnell Douglas DC-9-33CF N935F St. Croix, Virgin Islands [Caribbean Sea]

[bubbers44]

One of our MD80's had a dual deer strike one night resulting in a high speed abort. Someone put two deer decals on the nose section. One of our pilots had a fish strike at 100 ft landing at OAK when a seagull dropped it when it saw the plane about to hit him. Fish and deer are harder to avoid than big birds.

[Owain Glyndwr]

owain...how many of the rear mounted (western) jets had to ditch?

how many wing mounted had to ditch?

What has that to do with the relevant vulnerability of rear and wing mounted engines to bird strike? Nothing that I can see;surely the association of bird strikes with no ditching just reflects the fact that you (generally) meet more flocks of birds overland than over the sea? And of course if the Hudson river hadn't been conveniently close it wouldn't have been a ditching.

BTW, because of the upwash produced by the wing on the flow ahead of the LE, a noticeable proportion of the air going over the wing and towards the rear mounted engines starts below the wing.

[sevenstrokeroll]

con pilot..I know about that ditching...and thanks for publishing it...but I meant due to birds. I know you did too!

and its not that the HUDSON was close...there were other places to go, but with a higher hazard to those on the real brown earth

owain...I have no proof, but the most birds I've seen seem to hang out at the meeting of the land and the water.

[Ashling]

I think listening to ATC + looking at your ND, or equivelant, might also be helpfull in avoiding collisons with other aircraft. It builds SA and helps to avoid TA's and RA's crucial if you have a limited view which you do from the flight deck of an airliner. But, yes, clearly looking out the window is important too, more important at low altitude if GA traffic is around, less important at FL390. Unfortunately the one that is going to hit you tends to be on a constant relative bearing so there is little or no relative movement which of course makes it tricky for the eye as does a low sun and a myriad of other things.

Its a desterate feeling in air combat when the other aircraft has tally on you but you can't see him/her.

Hit plenty of birds too, but still got hired, guess they only assumed I'd avoid other aircraft and mountains which so far I have, still failing on the bird front every now and then. Ho hum.