Jackbr
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UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 8:24 am

http://www.youtube.com/watch?v=w74JQcabVTc


found this video of a UA 747 landing on 34L, note spoilers not deployed until very late in the roll.

Any idea as to why they weren't deployed, and if this is a regular occurance?
 
swiftski
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 11:28 am

Quoting Jackbr (Thread starter):
found this video of a UA 747 landing on 34L, note spoilers not deployed until very late in the roll.

Any idea as to why they weren't deployed, and if this is a regular occurance?


On the ground spoilers are used (together) to dump lift and increase effectiveness of the (wheel) brakes. This isn't always required.

Ground detent and Up detent offer a greater deployment than flight detent.

Primary purpose of spoilers in flight is assisting in roll.
 
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CCA
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 12:47 pm

Possible reasons are.

Speedbrake actuator failed, crew realised and deployed them manually.

Forgot to arm them, however selecting reverse thrust will move the speedbrake lever into the arm position which will then instantly command deployment as the A/C is 'on ground', in this instance though the crew would also have had to delay selection of reverse thrust to make them deploy so late.

The second option requires two things though, 1 forgetting to arm them and 2 deliberately delaying reverse thrust. So I find this unlikely.

There is a third option, the crew deliberately didn't arm them and delayed selection of reverse thrust due to the long runway length, I'm sure this is not SOPs though.
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Transpac787
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 12:49 pm

Quoting Jackbr (Thread starter):
Any idea as to why they weren't deployed, and if this is a regular occurance?

It's possible they didn't get the spoilers handle into the 'armed' position during the final check. Either that or just incorrectly set it, and during the rollout they just realized that the speed brakes didn't automatically deploy so the crew did it themselves.

Quoting swiftski (Reply 1):
Primary purpose of spoilers in flight is assisting in roll.

No.

The 747-400 only uses spoilers at slow speeds. I'd have to go dig out the manual but the spoilers no longer assist with roll at relatively slow speeds - it is just a function of the inboard and outboard ailerons.
 
474218
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 6:32 pm

Quoting Transpac787 (Reply 3):
No.

The 747-400 only uses spoilers at slow speeds. I'd have to go dig out the manual but the spoilers no longer assist with roll at relatively slow speeds - it is just a function of the inboard and outboard ailerons.


Not true! If you would look at the video (between 50-55 seconds), you can see the spoilers assisting the ailerons with roll control, ie, extending with the up aileron.
 
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 7:49 pm

Quoting 474218 (Reply 4):
Not true! If you would look at the video (between 50-55 seconds), you can see the spoilers assisting the ailerons with roll control, ie, extending with the up aileron.

Considering at 50-55 seconds, the airplane has Flaps 20 (or possibly Flaps 25) deployed, they are obviously *very* slow at that point, and is exactly why the spoilers are assisting.

Like I said, the 747-400 *only* uses spoilers at slow speeds. As the aircraft accelerates after takeoff, the spoilers stop actuating to assist in roll, and as the aircraft further accelerates the outboard ailerons also stop actuating. The reverse is true as the aircraft descends and decelerates.

[Edited 2010-05-12 12:58:25]
 
xero9
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 10:13 pm

Slightly off topic, but what is the use little panel that flaps around between the two sets of flaps? And what is its name if anyone knows.

Thanks!
 
boeing767mech
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 10:51 pm

Quoting xero9 (Reply 6):
Slightly off topic, but what is the use little panel that flaps around between the two sets of flaps? And what is its name if anyone knows.

Inboard Aileron. Or High Speed Aileron, this aileron is operating during all phases of flight to turn the aircraft. The outboard aileron is locked out during flight above approx. 278kts. (B767-300) to prevent over control of the airplane during high speed flight

David

[Edited 2010-05-12 16:17:14]
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CCA
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 12, 2010 11:38 pm

Quoting Transpac787 (Reply 5):
Like I said, the 747-400 *only* uses spoilers at slow speeds. As the aircraft accelerates after takeoff, the spoilers stop actuating to assist in roll, and as the aircraft further accelerates the outboard ailerons also stop actuating. The reverse is true as the aircraft descends and decelerates.

Sorry, this is not correct, spoiler roll control comes from the spoiler mixer it's a mechanical unit that has no idea what speed the aircraft is doing.

Spoilers are rarely seen during high speed flight as the roll input is not usually enough to activate the spoilers.
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peterpuck
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RE: UA 747 Landing SYD, No Spoilers - Video

Thu May 13, 2010 12:57 am

Quoting xero9 (Reply 6):
Quoting xero9 (Reply 6):
Slightly off topic, but what is the use little panel that flaps around between the two sets of flaps? And what is its name if anyone knows.

Thanks!

Inboard ailerons.
 
71Zulu
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RE: UA 747 Landing SYD, No Spoilers - Video

Thu May 13, 2010 1:34 am

Quoting CCA (Reply 8):
spoiler roll control comes from the spoiler mixer it's a mechanical unit that has no idea what speed the aircraft is doing.

Cool, thanks.

So I guess in this video

http://www.youtube.com/watch?v=i9IhQxmt08U

he was holding full left aileron?
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mcdu
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RE: UA 747 Landing SYD, No Spoilers - Video

Thu May 13, 2010 11:49 am

The function of the spoilers deploying upon landing is referred to as "AUTO SPEED BRAKE". This is armed on the approach by the crew and is activated by wheel spin up, weight on wheels and a few other arming items, ie handle in the detent. The auto speedbrake can be deferred and it allows for the crew to deploy the speedbrake themselves. There is a significant allowable weight penalty associated with it being manually deployed.

However, there are some pilots that will hold the speedbrake down when making a very smooth landing and slowly release the handle intentionally. This is to prevent the abrupt unloading of the wing and the resulting sink of the airplane. Without the autospeedbrake a smooth landing feels even nicer. This is not SOP. It would only occur on a very long runway where the additional stopping distance can be accounted for.

To summarize, in this instance the autospeedbrake could have been either; 1. inoperative or 2. intentionally held down for a smooth landing.
 
murchmo
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RE: UA 747 Landing SYD, No Spoilers - Video

Fri May 14, 2010 6:14 am

Quoting 71Zulu (Reply 10):

Yep. That video has been discussed before. There was a strong crosswind.
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tom355uk
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RE: UA 747 Landing SYD, No Spoilers - Video

Sat May 15, 2010 11:45 am

If you watch the angle of the wing closely, it actually seems as though the PF applies a slower than usual derotation, to provide for a smooth touchdown. The TR's cannot be selected until the nosewheel is down, ergo the spoilers would not extend until then. As somebody mentioned above, if the spoilers had automatically deployed when the MG touched down, the derotation would have been more rapid and made for a much firmer landing.
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DocLightning
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RE: UA 747 Landing SYD, No Spoilers - Video

Sun May 16, 2010 6:40 am

Quoting CCA (Reply 8):

Sorry, this is not correct, spoiler roll control comes from the spoiler mixer it's a mechanical unit that has no idea what speed the aircraft is doing.

How does this unit work? I'm assuming that on the 787 the eqivalent device would be an electronic unit that would have access to any information about the aircraft environment that it needed.
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AJ
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RE: UA 747 Landing SYD, No Spoilers - Video

Sun May 16, 2010 9:33 am

Quoting tom355uk (Reply 13):
The TR's cannot be selected until the nosewheel is down, ergo the spoilers would not extend until then. As somebody mentioned above, if the spoilers had automatically deployed when the MG touched down, the derotation would have been more rapid and made for a much firmer landing.

That is not correct for a 747-400. Both spoilers and reversers can be selected after main gear touchdown.
In this shot it can be seen that the reversers have been selected:

View Large View Medium
Click here for bigger photo!

Photo © Anthony Jackson

 
tom355uk
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RE: UA 747 Landing SYD, No Spoilers - Video

Mon May 17, 2010 4:03 pm

Quoting AJ (Reply 15):
That is not correct for a 747-400. Both spoilers and reversers can be selected after main gear touchdown.
In this shot it can be seen that the reversers have been selected:

Of course - I should have phrased it differently! What I meant to say was that they 'generally shouldn't' be 'normally' selected until after derotation is complete, unless field performance requires it.

Is that more accurate?  
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AJ
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RE: UA 747 Landing SYD, No Spoilers - Video

Tue May 18, 2010 9:36 am

Quoting tom355uk (Reply 16):
Of course - I should have phrased it differently! What I meant to say was that they 'generally shouldn't' be 'normally' selected until after derotation is complete, unless field performance requires it.

Is that more accurate?

It is normal operation to select reverse thrust prior to nose gear touchdown.
Boeing states:

Quoting Boeing 747-400 FCTM:
After touchdown, with the thrust levers at idle, rapidly raise the reverse thrust
levers up and aft to the interlock position, then apply reverse thrust as required.
 
tom355uk
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RE: UA 747 Landing SYD, No Spoilers - Video

Tue May 18, 2010 11:05 am

I'll shut up and go to the back of the class then ...

  

I'll stick to Airbus threads in future, at least I know a little about them!
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CCA
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RE: UA 747 Landing SYD, No Spoilers - Video

Tue May 18, 2010 4:44 pm

Quoting DocLightning (Reply 14):
How does this unit work? I'm assuming that on the 787 the eqivalent device would be an electronic unit that would have access to any information about the aircraft environment that it needed.

I'll try and remember to take a pic of it tomorrow, but the spoiler mixer takes mechanical inputs from the control wheel in roll and the speedbrake lever, it will mechanically (via cables) cause spoiler movement, it's called a mixer as it mixes both commands when required.

The 787 and 777 etc use fly by wire electrical signals like you said that are tied in with the ADIRUs and others computers so speed and A/C configuration can lead to a multitude of outputs depending on the hardware.

This is why we see so many differing questions here on airliners such as when we see the FBW A/C flight controls do so called strange things, the 777 I/B aileron is a good example it functions as a aileron, flap and spoiler plus unloads itself during takeoff when high thrust is applied, all thanks to FBW.

The 748 due to it's newish wing will use new FBW spoilers and O/B aileron which will be programmed / tweaked during flight testing to make it fly like a 744 in roll.

There's an article in ATW May issue that also mentions this, tried to find it but couldn't on the net.
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413X3
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RE: UA 747 Landing SYD, No Spoilers - Video

Wed May 19, 2010 9:27 pm

Just another example of an uneducated person (the cameraman) making a claim about something they don't know. Spoilers did deploy, when the nose wheel touched the ground... obviously they had the nose up in the air on main gear touchdown and just settled down slowly. Non-event. Sensational title... and a.netters get mad at the media for the same thing. oh irony

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