PolAir
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'Pilotless Jumbo Seconds From Disaster" At VHHH

Mon Mar 14, 2005 10:26 am

I am not sure when that happened, but article is dated today, so must be fairly new.

http://www.telegraph.co.uk/news/main...t=/portal/2004/10/14/ixportal.html


I don't get it. So all pilots left the cockpit after go around? If not, why nobody answered ATC? Can 747, even relatively light, sustain 120 knots (130mph) or is it just pure media imagination? What do you guys think?
 
DLKAPA
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Mon Mar 14, 2005 10:29 am

Show me a 747 doing 120 knots and I will show you a hole in the ground.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
doug_or
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Mon Mar 14, 2005 10:32 am

Did you read the article? The autopilot disconnected and the pilots didn't know it.
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PolAir
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Mon Mar 14, 2005 10:33 am

Did not read this closely. Crew was in the cockpit. However, didnt they feel steep climb/loss of speed? I assume visibility was poor.
 
ozglobal
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Mon Mar 14, 2005 10:34 am

This happened four months ago from memory. The article is dated, if you look carefully, 14/10/2004. Today's date is being automatically displayed on the webpage.

[Edited 2005-03-14 02:36:11]
When all's said and done, there'll be more said than done.
 
DLKAPA
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Mon Mar 14, 2005 10:36 am

The article also said that the aircraft was doing 120 knots (130mph) in a 30* Roll and because of the roll AVOIDED the stall. That's physically impossible, the roll would cause the wing to be less efficient in lifting the plane (hence why when you turn an aircraft in flight you also pull back on the yoke to give it a slightly noze-high angle of attack), thus the airplane would have fallen to the ground in a nice sliding corkscrew action.

Ok, so maybe it's possible for an empty 747 to be doing 120kts in flight, provided it's the phase of flight known as "Flare" and the thing is inches above a runway, but comeon, a 747 loaded with 350 pax doing a 30* bank at 120kts, no way!

[Edited 2005-03-14 02:37:11]
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
doug_or
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Mon Mar 14, 2005 10:41 am

DLKAPA, Chill! My response was written when there were no replies. I was reacting to the question about the crew not being in the cockpit.

However, if you enter a roll , like you say, you need to apply an up elevator input. Otherwise the nose drops. Since the pilots didn't apply any backpreasure, the nose did drop and so the angle of attack was reduced.
When in doubt, one B pump off
 
DLKAPA
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Mon Mar 14, 2005 11:40 am

Quoting Doug_Or (Reply 6):
However, if you enter a roll , like you say, you need to apply an up elevator input. Otherwise the nose drops. Since the pilots didn't apply any backpreasure, the nose did drop and so the angle of attack was reduced.

True, but according to the article, the noze didn't drop until at or near 120kts airspeed. I'm pretty sure a 747 flying with a decent pax load will stall well before that.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
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HAWK21M
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Mon Mar 14, 2005 12:49 pm

How did the News reach this "Aviation Correspondent" BTW.
regds
MEL
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727EMflyer
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Mon Mar 14, 2005 1:00 pm

Keep in mind this story is coming to us via the media... the most often flamed contributor at a.net. I would guess the 130 MPH quoted speed was groundspeed. Given all the variables like wind and angle of climb, the aircraft could have been in much better shape airspeed wise. Either way if the course the plane took is anywhere close to that shown in the articles graphic, shame shame shame on the flightcrew. When did crew stop being pilots and start being mere "airplane operators?"
 
FriendlySkies
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Mon Mar 14, 2005 1:15 pm

Quoting 727EMflyer (Reply 9):
I would guess the 130 MPH quoted speed was groundspeed.

Not to be nit-picky, but isn't groundspeed usually HIGHER than airspeed?
 
DLKAPA
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Mon Mar 14, 2005 1:46 pm

Quoting FriendlySkies (Reply 10):
Not to be nit-picky, but isn't groundspeed usually HIGHER than airspeed?

Depends on the winds. Airspeed is really a measurement of Ram Air Pressure into the aircraft's Pitot tubes, so if there is a strong headwind, the measurement of the rate at which the aircraft cuts through the air will be higher. The airspeed will always be higher than the groundspeed in the event of a headwind.

Generally, one way to think about a headwind is "Free Airspeed." If you are rolling down a runway with a 30kt headwind, you can lift off the runway going 30kts slower than your normal takeoff speed with no headwind. The same works for landing, as it's much easier to make a soft touchdown with the same 30kt headwind (provided it's an almost direct headwind), because you are again travelling 30kts slower than normal touchdown speed.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
PhilSquares
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Mon Mar 14, 2005 1:58 pm

Sorry to be a nay sayer, but airspeed really doesn't have a lot to do with stalls. What is relevant is the angle of attack. I can have 0 angle of attack on an airplane and 0 airspeed and I am not in a stalled condition.

I can assure you depending on the flap configuration, with full thrust and 130 mph (kias more likely) the airplane probably flying fine.

Remember this incident is really very old news. It was on PPRUNE for a while and I am sure if you want search the archives on there you will probably get a better idea of what happened.
Fly fast, live slow
 
DLKAPA
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Mon Mar 14, 2005 2:04 pm

Quoting PhilSquares (Reply 12):
I can have 0 angle of attack on an airplane and 0 airspeed and I am not in a stalled condition.

When you're sitting on the ground parked, yes. I find it very hard to believe that any airplane in flight could be at 0 angle of attack and have 0 airspeed while not being in a stalled condition.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
doug_or
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Mon Mar 14, 2005 2:19 pm

Quoting DLKAPA (Reply 13):
I find it very hard to believe that any airplane in flight could be at 0 angle of attack and have 0 airspeed while not being in a stalled condition

Well you'll just have to work on that. Stall is caused by one thing- angle of attack. In normal 1 g flight, angle of attack needs to increased as airspeed decreases, just as AoA must be increased when weight is increased. However, when in less than 1 G flight- like, I don't know- when the nose is coming down, the AoA @ a given airspeed will be lower, and therefore further from stalling.

RE: Airspeed vs ground speed, there are two basic kinds of airspeed indicated (IAS, the ram preasure you talked about) and true airspeed (TAS, the actaul speed of the aircraft moving through the air). Statisticaly, TAS will on average be average be faster that ground speed, becasue more than half of the potential wind vecotors result in a reduction in groundspeed. However, as altitude increases, IAS goes down @ a given TAS, and therefore will most likely be less than GS.
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goboeing
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Mon Mar 14, 2005 2:20 pm

Quoting DLKAPA (Reply 13):
I find it very hard to believe that any airplane in flight could be at 0 angle of attack and have 0 airspeed while not being in a stalled condition.

Try this, you might like it:


View Large View Medium
Click here for bigger photo!

Photo © Jean



Nick
 
PhilSquares
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Mon Mar 14, 2005 2:23 pm

DKKAPA,

What happens when you "unload" an airplane?

The angle of attack approaches 0. The wings are producing no lift, so you have no induced drag. All your thrust is being converted to potential energy.

When I flew fighters you tried to do all your maneuvering in the vertical. It's the best way to conserve/make energy. It was not uncommon to go vertical, unload and have your airspeed bleed down to 0. When I was a T-38 instructor, you tried to teach energy management and that was a great demo to go to mil power and unload and watch the airspeed go to 0 and the angle of attack go to 0.
Fly fast, live slow
 
DLKAPA
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Mon Mar 14, 2005 3:28 pm

Ahh... I'm LEARNDING!!! Big grin

One more question though

Quoting PhilSquares (Reply 16):
The angle of attack approaches 0. The wings are producing no lift

I'm probably missing something here, but isn't the plane technically in a "stall" if the wings are producing no lift?
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
707437
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Mon Mar 14, 2005 3:50 pm

No load means you need no lift to maintain altitude so no problem right?

So as long as your momentum is holding the airplane up who even needs a wing anyway. . .

But realistically when the lift is slightly less than the weight of the aircraft you've got a controlled mild descent.

But when these numbers diverge seriously. . . Then the flow separates across the airfoil and game over.

That's my take on it. . .
 
PhilSquares
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Mon Mar 14, 2005 4:17 pm

The reason the wings are producing no lift is you are in a 0G, or close to it, environment. So as the g-load approaches 0 the demand for lift on the wings decreases (read angle of attack). Conversely, a 60 degree bank level turn, will give you a 2 G load. Now you have to have back pressure on the stick (yoke) to increase your angle of attack. If you add no power, you will lose airspeed, and have a greater need for back pressure. Now you are increasing the angle of attack to produce the same amount of lift at a lower airspeed. I have felt buffet on the airframe at over 500 KIAS while maneuvering. Why? Because I was approaching the Max AOA. Now you have an accelerated stall.

Hope that helps. If not just ask here or send me an email.
Fly fast, live slow
 
DLKAPA
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Mon Mar 14, 2005 4:59 pm

That is all my fragile little mind can handle tonight...

Thanks dude!
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
oly720man
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Mon Mar 14, 2005 6:36 pm

Interesting caption on the little graphic..... "Near miss for Britons on Cathay Pacific flight to Hong Kong."

Were the other nationalities perfectly safe then??
wheat and dairy can screw up your brain
 
MEA-707
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Mon Mar 14, 2005 10:06 pm

Yeah, that's a hilarious caption, typically the UK tabloid, like that the Britons on board make the story connect more to their reader base, they presume the reader might otherwise raised his shoulder "who cares about some shaded eyed people in some bamboo airplane"
nobody has ever died from hard work, but why take the risk?
 
DAYflyer
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'Pilotless Jumbo Seconds From Disaster" At VHHH

Mon Mar 14, 2005 11:55 pm

Quoting DLKAPA (Reply 5):
The article also said that the aircraft was doing 120 knots (130mph) in a 30* Roll and because of the roll AVOIDED the stall. That's physically impossible, the roll would cause the wing to be less efficient in lifting the plane (hence why when you turn an aircraft in flight you also pull back on the yoke to give it a slightly noze-high angle of attack), thus the airplane would have fallen to the ground in a nice sliding corkscrew action.

Ok, so maybe it's possible for an empty 747 to be doing 120kts in flight, provided it's the phase of flight known as "Flare" and the thing is inches above a runway, but comeon, a 747 loaded with 350 pax doing a 30* bank at 120kts, no way!

I believe in a dirty configuration it must maintain a minimum of 140 knots to remain airborne.
One Nation Under God
 
PhilSquares
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Mon Mar 14, 2005 11:59 pm

Quoting DAYflyer (Reply 23):
I believe in a dirty configuration it must maintain a minimum of 140 knots to remain airborne.

Believe me, it will continue to fly well below the 140 Knots you mention!!!! Again, it's not speed, but angle of attack.
Fly fast, live slow
 
DLKAPA
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Tue Mar 15, 2005 12:52 am

Quoting DAYflyer (Reply 23):
I believe in a dirty configuration it must maintain a minimum of 140 knots to remain airborne.

Nope! Big grin

Last night after reading this thread I decided to test this theory in a fully loaded 744 in flightsim. I did a touch and go and pulled the plane up into a 15* Climb with the flaps set to 30*, at approximately 2500 AGL I put the plane into the 30* right bank and pulled the power back to zero. Oddly enough, the plane nosed over on it's own and began to pickup airspeed. No stall occurred.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
B742
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'Pilotless Jumbo Seconds From Disaster" At VHHH

Tue Mar 15, 2005 1:00 am

Lucky escape there!

I was at Kai Tak when the China Airlines 747 overran the runway, not a pretty sight! Good job we didn't have another HKG disaster!


Rob!
 
powerofpi
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 1:25 am

I wonder if they retracted the flaps like they were supposed to. Once I was on a 737 and we did a go-around. I know it's not a 747, but I was pretty amazed at how quickly the flaps were fully retracted. If they didn't retract the flaps then i guess 120-130 knots is a possibility. This makes me really wonder what the hell the pilots were doing up there because obviously you don't leave full flaps in on a go around. Who was responsible for retracting the gear and the flaps?? Did they all just completely forget how to fly an airplane? Obviously the flaps HAD to be deployed because no airliner will stay airborne at even 150 knots with no flaps.
 
doug_or
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 1:48 am

It might be possible they had partialy retracted the flaps. I don't know anything about 747 automation (or lack there of), but in the Boeing I'm familiar with, the pilot retracts the flaps as the airspeed accelerates (which allows the plane to continue accelerating). After the go around you immdiantly retract the landing flaps (or at least some of them), and then get the t.o flaps as you accelerate. This is important, becasue, the t/o flps produce a lot of extra lift, while the landing flaps produce a little extra lift and a lot more drag.
When in doubt, one B pump off
 
rootsgirl
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 3:09 am

Did you read the post? Start your own post about rolls etc and someone answer the question. It involves the crew in the flight deck. Ignoring the question and continuing your own debate is not very polite.
 
DLKAPA
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 4:00 am

Quoting Rootsgirl (Reply 29):
Did you read the post? Start your own post about rolls etc and someone answer the question. It involves the crew in the flight deck. Ignoring the question and continuing your own debate is not very polite.

Neither is coming into a thread 30 replies in and trying to tell us what the topic should be.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
stealthpilot
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 4:30 am

The article also mentioned that the aircraft had a pitch (not bank) of 28 degrees. That seems scarier than a 30 bank!!

Does anyone know the critical angle of the 744? (PhilSquares?) because 28 degrees is very high isnt it?
-Nikhil
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buckfifty
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 4:58 am

This makes me really wonder what the hell the pilots were doing up there because obviously you don't leave full flaps in on a go around. Who was responsible for retracting the gear and the flaps?? Did they all just completely forget how to fly an airplane? Obviously the flaps HAD to be deployed because no airliner will stay airborne at even 150 knots with no flaps.

Oh dear. Months on, we still get this nice idiotic drivel. Knob on, eh.
 
VEEREF
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 5:54 am

Actually we'll be seeing this headline again on a regular basis some time in the future when pilots are removed from aviation...........
Airplanes are cool. Aviation sucks.
 
VEEREF
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 6:08 am

The scary part of this event, assuming the numbers are correct, is the degree to which the crew lost situational awareness of what mode they were operating the aircraft in. Autopilots don't just disconnect themselves without giving the crew some sort of warning.
To let a situation like that deteriorate into a 180 degree course deviation indicates a lapse in procedure and awareness. The leading cause of CFIT accidents.
Airplanes are cool. Aviation sucks.
 
lapa_saab340
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 6:32 am

Hi Stealth
One detail you have to be careful about is that angle of attack is not the same thing as pitch angle - it is not affected by where the nose is with respect to the horizon.

Looking at this case, the fact that the nose was up 30 degrees above the horizon tells you nothing about the angle of attack. Given enough thrust, the angle of attack could be quite small even with that nose-up attitude. As an example, a fighter jet going straight up will have a zero angle of attack! And the same fighter can also exceed its critical angle of attack and stall while pulling out of a dive, with the nose well below the horizon.

A simple way to visualize angle of attack is to compare the "direction the nose is pointed at" to the direction in which the plane is actually moving (flight path). You know that the oncoming airflow (or relative wind) is opposite to the flight path of the plane, so if you know which way your plane is "pointed" you know at which angle the wings meet the oncoming airflow.

Of course looking out your window with the nose pointed 30 degrees up is still unnerving for the passenger, no matter that the angle of attack may still be quite low  Smile
 
stealthpilot
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 1:35 pm

LAPA_SAAB = Correct you are, the angle of attack is the angle to the relative wind  Smile Nevertheless, what is the critical angle?
-Nikhil
eP007
 
PhilSquares
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 1:48 pm

There is no angle of attack indicator on the 744. In addition, it would depend on other factors such as gross wight and g loading (bank angle).

However, at stick shaker you are approaching the critical angle of attack.
Fly fast, live slow
 
airlinelover
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 1:53 pm

Most passengers disembarked without realising they had been so near to disaster.

Until now..

That's crazy.. Pilots must have been wasted or something.. OR just ignorant.

Chris
Lets do some sexy math. We add you, subtract your clothes, divide your legs and multiply
 
PhilSquares
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 2:01 pm

I am amazed at all the experts on this forum. If there are so many experts, why has no one suggested an autopilot malfunction? No, that couldn't happen. Instead we find people starting new topics asking if CX drug tests pilots, or asking in this thread if the pilots left the cockpit, or best of all if they were "wasted".

I don't know why all the world's airlines don't look here when they need pilots!!!!
Fly fast, live slow
 
DLKAPA
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 2:15 pm

Quoting PhilSquares (Reply 39):

I don't know why all the world's airlines don't look here when they need pilots!!!!

They did, hence very few members of this forum will ever find their way into a cockpit Big grin
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
doug_or
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RE: 'Pilotless Jumbo Seconds From Disaster" At Vhhh

Tue Mar 15, 2005 2:29 pm

Quoting PhilSquares (Reply 39):
No, that couldn't happen. Instead we find people starting new topics asking if CX drug tests pilots, or asking in this thread if the pilots left the cockpit, or best of all if they were "wasted".

"but I can land in MSFS9, so anytime anything goes wrong anywhere its becuause they are incometpant and should be fired"
When in doubt, one B pump off