Speedbrakes: ermmmm

[VNAVSPD]

Can anyone explain what happened in this vid? The speedbrakes didn't deploy immediately on touch down (ok, maybe they weren't armed) and then spoiler panels 11&12 stay retracted until the aircraft has nearly stopped?
http://www.flightlevel350.com/video_streaming.php?id=6186

[Rainboe]

In a nutshell, 6 spoilers on each wing, . The 4 inboards on each wing act as flight spoilers, on the ground, all 6 act as ground spoilers. The auto spoilers would be armed for landing if serviceable- it's part of the checklist. When the speedbrake lever motored from the ARM position to the initial detent, the inboard 4 extended, and as the lever carried on aft when the main gear touched down and engines 1 & 3 thrust levers are near the closed position, the ground spoilers (the 2 outers) extended. It may be remotely possible the spoilers were left in manual for landing- very rare. I see nothing very unusual. They were nowhere near 'nearly stopped', trust me. A 747 takes a lot more stopping than that!
Why are people so convinced they have seen a 'cock-up' when they observe something they don't understand? We recently had someone seeing a 737 taxi around on itself, and the assumption automatically was 'the pilot got lost!' (must be Ryan again)

[VNAVSPD]

Who said anything about a 'cock-up'?

and as the lever carried on aft when the main gear touched down and engines 1 & 3 thrust levers are near the closed position, the ground spoilers (the 2 outers) extended

If you look closely, almost immediately upon touch down, you can see the thrust reverser sleve move aft. It's then 12 seconds until spoilers 11&12 extend. This tells me that the thrust levers were closed, and I assume that they would not have been able to select R/T unless the main gear were on the deck.

[Hand Solo]

Its quite possible that if they greased the landing the spoilers failed to deploy automatically and had to be deployed manually. It's happened to me twice (and no, it wasn't my landing). You generally spot it after you've selected reverse and noticed the speedbrake arm in the wrong position which could account for the delay.

[Rainboe]

Who said anything about a 'cock-up'?

Your title to this thread was 'Speedbrakes: ermmmm' implying perhaps they were forgotten initially and some sort of embarrassment? I think that's how most people would read that title- 'errmmm' is usually taken as 'I've/you've forgotten something!'. I would have titled it '747 Speedbrake query' if I simply wanted to find out why they took so long.

I have told you the parameters for their operation. Not many pilots will be aware of this gap in their operation- I wasn't. There is no indication on the flight deck. It takes an extra movement of the speedbrake lever to deploy those outer ground spoilers. Their effect will not be significant. I would suggest that they took just over 10 seconds from initial contact. The 747 if landed smoothly can take a long time to settle onto it's 4 undercarriage legs and make the weight switches adequately, so really nothing exceptional. HS's explanation I agree with, it is not unknown to have to deploy them manually in that circumstance. No 'errmmmm' needed.

[VNAVSPD]

It was to signify the pause, as in: erm, where are they? Sorry, I didn't realise that my title would come under such scrutiny.

I would have titled it 747 speedbrake query

Thanks for the advice.

I have told you the parameters for their operation.

Yes, and thank you.

Sorry Rainboe, but I really don't understand your hostility, or your obsession in trying to point out that I am digging for something other than a technical explanation.

I am a very curious person, if there's something that I don't understand, or that doesn't seem to make sense, then I will endeavor to find out.

no errrrmmm needed

Not anymore :ok:

[Capt Fathom]

Did those flaps look like they were fully extended? When I follow a jumbo onto the runway, F20 looks like a lot of flap, that video didn't look like 25/30 .. Maybe just the angle.

[VNAVSPD]

I think it's the angle. They must have extended past 20deg because the 3rd flap panel (not sure of the correct term, is it the tab?) is slightly extended.

Something tells me that BA SOP's dictate a preference of F25 over F30. Not sure of the reason, or where I heard it, could be a load of rubbish. :bored:

[gas path]

Flap 25 was a classic limit, introduced to take the load off of the flap track fwd. fuse pins that had the odd habit of breaking.:ooh: IIRC Pan-Am were the first to introduce it, and later a Boeing recommendation due to the failures, and yes, we had a couple of failures too:ooh:
Must admit I would have expected to see more of the slot between the mid flap and aft flap which only begins to open up as the flaps translate from 20 to 25 units. Must be the angle it's viewed from.:suspect:

[Rainboe]

We used to operate the Classic to F30 and there was a spate of flap failures. F25 were landings were made standard, and that is what the 747-400 uses as standard, with F30 for special requirements.

[VNAVSPD]

Does the -400 suffer with the same problem as the classics?

[Rainboe]

No, not at all. It has a redesigned wing. The word going around on the Classic at the time was that we should not have been doing standard F30s. Boeing intended long term use to be F25 with 30 available if needed occasionally. After increasing the stress, failures were occuring. Indeed, one Classic, circuit bashing empty at Prestwick had the rear inboard flap unit detach at one end, swing around and burst through door 4R like a spear and go through a few rows of seats. The photos were shocking.
The 747-400 does not have problems- if Harrods sold widebodies, it would be a 747-400. 411A bangs on about 1011s because he never flew 747-400s.

[chrisbl]

As far as I recall, BA ask people to switch off all electronic equipment before landing.

Why did you not chose to comply?

[mcgoo]

he never said he shot the video!

[Hand Solo]

Up until about 6 months ago BA flew the 747-400 like it was a Classic 'cos thats the way it was always done and thou shalt not question it. Changing the arcane procedures on the senior fleet must be like wading through treacle.Some of the trainers visibly blanch, then tremble with rage if you dare to suggest that parts of another fleets SOPs might be superior.:}

[VNAVSPD]

Is there much of a difference in Vref between a F25 landing and a F30 landing, assuming same weight etc?

After increasing the stress, failures were occuring. Indeed, one Classic, circuit bashing empty at Prestwick had the rear inboard flap unit detach at one end, swing around and burst through door 4R like a spear and go through a few rows of seats. The photos were shocking.

Thank god it was empty!

[gas path]

Ahhh! that bought back memories. The old 74 classic had a tendancy to shed the odd foreflap as well until new beefed up fittings and inspection regime were introduced :suspect:
:hmm: thread drift......sorry

[VNAVSPD]

It's pretty amazing how they manage to get a set of tripple slotted flaps to extend and droop so far and still remain sturdy, even with the huge air loads they must encounter. The 747 certainly does have a very impressive wing!

[Rainboe]

The old VC10 ('God Bless the Queen!') started shedding flap units at one stage. It had 5 big units each side, they must have been like single garage doors. Dropped a few of those around the world.

The difference between F25 and F30 was about 3 knots, and not a great deal less on landing roll. I always preferred sticking with what you know and doing F25 even if limiting- that way you can put it down more precisely which is more important than an unfamiliar attitude landing-IMO.

[VNAVSPD]

I seem to recall an executive aircraft that had rather large flaps compared to it's size. It also had a lift-dump system where the flaps swing almost vertically down on landing. I think it may have been the HS125 or a variant of.