From: jbates31@tiscali.co.uk
"David T. Ashley" wrote in message
news:jN6dnclYAtQCGQ_anZ2dnUVZ_jCdnZ2d@giganews.com...
> "john bates" wrote in message
> news:47921f43$1_3@mk-nntp-2.news.uk.tiscali.com...
>>
>> Please could an expert here tell me. If with a total loss
>> of electric power would all control of a/c be the result?
>>
>> If (as a few ground observers have stated) the high nose
>> attitude and apparent stall from 100/200 foot is true and
>> the pilot had had control would he not have pushed the
>> stick forward to increase the glide distance/ Or choose to
>> pancake onto the grass and avoid all the resultant sparks?
>> Many thanks.
>> John
>
> Just a few notes based on the posts here, some of which are erroneous:
>
> a)Control of the aircraft ... can't find easy information about the
> mechanical backup of the 777, but various information on the web hints
> that it does exist and that it involves only rudder and elevator trim.
***Hi David, My take for what it's worth.
Trims only, very inifectual at the low speed.
> If this is true, and if all the control systems failed, it may very well
> be that the flying pilot had only rudder control but didn't realize it.
> Using the rudder will also affect the aircraft bank angle, as it causes
> the outside wing to generate more lift.
I agree and one of the eyewitnesses did say that at approx half a mile
away a wing went down and soon corrected to level flight, he said 40
degrees which is a lot
> The flying pilot may have been moving the ailerons and rudder together,
> and it all happened so fast and so near the ground that he didn't realize
> the ailerons weren't working. He may have perceived the sluggish bank
> effects of the rudder to be ineffective aileron action.
for me this is of no relavance.
> b)Pitch up, stall ... if the flying pilot had only rudder control and the
> engines ceased delivering power, a sharp stall isn't the normal result.
> The plane will slow up and normally the nose will drop because the wings
> are producing less lift. With no control input, a plane that was trimmed
> before loss of power will normal slow and pitch down (slower than you want
> to be flying it on final approach, but not a stall).
I heard three different eye witnesses say the nose was high when a/c was
100/ 200 feet, from that hight to the ground the nose would only be part way
down when stalling, with very little forward speed, otherwise the port
undercarrige would not have been driven through the wing as it did.
The torn off set were only 50 foot from the a/c.Much more downward force
than forward. hitting with level attitude the a/c would have run on much
much futher, the grass though very wet was flat, people were walkin normally
on it.
>
The flying pilot may have had no elevator control and not realized it. The
> plane may have just glided itself in with rudder control only. The
> observer
reports of pitch up may have been just the normal glide plus ground
effects.
No, the speed would then have been app 100mph at least (What's the stall
speed / I bet not less than 130mph. How long are the scrape marks in the
grass, at most 200/300 yards, with engine mount/s digging into the soft
grass only for a very few yards. I agree with your glide remarks B4 stall.
> The accident investigation will sort that out.
>
> c)Glide distance ... If the problem occurred at 600 feet, there isn't very
> much in the world that will affect glide distance noticeably, except maybe
> retracting flaps a notch or two. If the plane is traveling too slow,
> pitching down to gain a bit of speed will consume altitude (tradeoff of
> potential energy). If the plane is traveling too fast, this means it will
> be traveling too fast near the ground, too, and pitching up near the
> ground will stretch the glide and bleed off the airspeed so as to delay
> contact with the ground. 600 feet is too low for any control actions to
> make that much of a difference in glide distance.
as the problem happened at 6,000 feet, the correct speeds and settings
would
> make a noticeable difference. But not at 600 feet.
>
> d)Dual engine failure ... that is going to be the million dollar question,
> and I'll be watching the accident investigation to find out what happened
> there.
>
> In airliner design, they typically go to ENORMOUS lengths to be sure that
> there aren't single points of failure that affect multiple engines. As
> they set up for landing, the fuel system is typically configured per
> checklist so that the #1 engine feeds from a different tank than the #2
> engine. The engines use separate fuel tanks, separate fuel pumps, and
> separate electrical systems to be sure that nothing can knock out both at
> the same time.
>
> It is sounding like a fly-by-wire throttle control problem ... and that is
> very frightening.
>
> I'm very curious to know what happened.
>
> I agree with other posters who pointed out that even with fuel
> contamination or exhaustion, simultaneous failure wouldn't normallly
> occur.
>
> e)Landing gear damage ... somebody said the plane must have hit hard (high
> vertical velocity). Not necessarily true. The plane came down in muck
> and grassy terrain. The vertical speed could have been normal but the
> plane didn't react well to imperfections in the ground (little hills and
> so forth). The black box will tell the story.
>
> f)Luck ... I agree that those people were _very_ lucky. Just a couple
> seconds earlier with the problem and the outcome would have been a
> catastrophe. It was a miracle that they made it onto airport property.
I couldn't agree more. I'm out of time now until tomorrow.
Many thanks,very interesting.
John.
>
> --
> David T. Ashley (dta@e3ft.com)
> http://www.e3ft.com (Consulting Home Page)
> http://www.dtashley.com (Personal Home Page)
> http://gpl.e3ft.com (GPL Publications and Projects)
>
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