Virgin landing gear incident LGW!

[NSEU]

With ALTN selected and gear lever up, then restoration of hydraulics would cause the gear to go up; doors would be powered to open. System would be in its normal mechanical state therefore when the gear uplock operates to the lock position then the gear doors will close. The ALTN circuit is latched until the switch is positioned to normal (off).

Thanks, MrPeabody.

Would the ALTN circuit be latched and ineffective (until cycled off/on)? In this condition, with the gear up, switch still selected and then the gear lever put to OFF (normal flight position) would the gear and doors stay up?

Lube cover? I'm picturing all kinds of things in the right wing gear wheel well (pack plumbing, L autopilot actuator, Left CLCP, spoiler differential, aileron programmer, fuel pumps, cargo heat plumbing, etc).

Thanks.

[woodpecker]

Well VS69, you suggested

No cable run for the alternate extend system on a jumbo each uplock has an elec motor.

There are a few others, including myself who would suggest there are cables and motors...

The motor obviously worked, but the sequencing including the cables most certainly didn't.

Perhaps you were just suggesting there were no cables from the flight deck.

[NSEU]

Well VS69, you suggested

He acknowledged his mistake in a following message

[vs69]

Cheers nseu, you are both right,I meant from the flt deck yes. Problem with doing stuff from memory, when tired,at home!

[MrPeabody]

NSEU,

Would the ALTN circuit be latched and ineffective (until cycled off/on)?
Yes.

In this condition, with the gear up, switch still selected and then the gear lever put to OFF (normal flight position) would the gear and doors stay up?
Yes; the system is back to it's mechanical state.

I was thinking the lube cover around the aileron programmer but I don't think it's that big; it's nearest thing to the gear that I can think of that could get dragged down by a burst tyre (if that was the cause of system 4 loss).

[NSEU]

Thanks, MrPeabody!

I was thinking the lube cover around the aileron programmer but I don't think it's that big; it's nearest thing to the gear that I can think of that could get dragged down by a burst tyre (if that was the cause of system 4 loss).

and perhaps the wrong colour

Here's a photo I found in my archives...



Someone suggested the door inner skin (?).

[SMOC]

The gear has contacted the outer wing gear folding door and basically ripped/folded it over into view. You can see the dimpling in the gear door that suggests it's deformed.

This suggests the gear dropped out of sequence or too fast (restrictor problem/sequence issue).

[bloom]

I love how everyone describes the landing as so smooth. But really, the aircraft was designed to land on four trucks of tires. With only three available, they had to flex more than four. It's like if I punched you in the chest three times simultaneously instead of four at the same time. If the aircraft had say ten trucks of tires how would anyone ever survive the initial impact?

Like the old ad for using prunes vs. a laxative went: "is one enough? Six too many?"

[MrPeabody]

SMOC,

My screen resolution has been a bit off so post #168 was a heavily pixelated and I couldn't definitively see the bend or much else. Either several reds, or the shedding of my crap multifocal lenses, or the computer coming good (not sure which one) I can see what you are referring to.

The restrictor check valve is meant to slow the gear primarily at the bottom of the cycle; so the momentum doesn't tear it out when the downlock engages. So I'd rule that out given the gear has only fallen a small distance. However that amount of damage is indicative of hydraulics being powered, I would suggest on the retraction cycle.

The gear has tripped the uplock which then powers the doors closed; the doors have hit something on the way in. I saw the dimpling you are referring to and guessed peppering from tyre fragments possibly.

The only other scenario for the doors to be that bent that I can think of is if the gear was hydraulically powered down into them. Can't get my head around the failures or selections to do it though.

NSEU,

I have had the misfortune of seeing all the items you have shown painted white (including the fire blanket on the aircon duct). However you are correct; this should have a yellowy tinge (if it were white) from all the hydraulic leakage.



Bloom,


I have not seen the ads you are referring to; however would suggest to you that 1 prune is not enough and 6 laxatives is far too many!

[SMOC]

When Wing Gear Alternate Extension (free fall) mode is used, there is no hydraulic pressure to dampen the movement, sequence the operation or lock the gear in the down position.

Therefore the Wing Gear pressure operated restrictor check valve remains in the limited flow (closed) position for the initial 3 to 4 seconds of extension so the Wing Gear extends slowly initially, primarily to prevent the gear falling at an excessive rate and damaging the trunnion supports, due to the large moment arm of the strut, and secondly to ensure the gear clears the free falling gear doors.

Having done gear swings I can assure you, the gear drops like a rock and actually bounces until it's allowed to fall gracefully to extend fully we actually used to push gear at the end of travel just to help it along and lock down.

[Oakape]

I would suggest on the retraction cycle

I'm thinking retraction cycle as well. Didn't the crew report a problem with the gear after departure & that was the reason for the return?

The door could have been closing before the gear was fully retracted, leading to it being powered into the gear, jamming everything. Then, when the alternate gear extension was done for the wing gear, it didn't move.

The other thing that got my attention in the photo is the absence of the aft, outboard wheel. It is on the same fore/aft axis as the forward, outboard wheel, which is the one that is visible. So shouldn't it be at least partly visible in the photo? Has this wheel separated from the aircraft & is damage from the loss of this wheel the reason for the gear jamming?

[geezah1984]

It is just visible here, just.

[SMOC]

In this video you can see how the gear bounces during an extension when there is insufficient fluid flow, it's similar to an alternate extension.

If the gear door is in the way it'll look very similar to the incident aircraft.

http://youtu.be/TIyKSu7fXN8

(The extension starts at 0:54)

[Oakape]

Thanks geezah1984, that will be it. The tilt is obviously greater than I thought.

[giggitygiggity]

I keep seeing bits in the news/online about the re-balancing of the aircraft's fuel to lighten the load on the wing above the damaged gear. Is this a realistic thing to do or have the journo's read between the lines when simply the aircraft jettisoned fuel to get down below MLW?

Edit: I see that on the bus the QRH suggests considering opening the crossfeed and turning the pumps off but cant see this realistically having a massive impact on a gear that is stuck up.

[Volume]

Do all the stains on the LH body aft of the body landing gear indicate a fresh major hydraulic leak ? Which hydraulic systems are installed in the left BLG bay ?

[NSEU]

Fresh leaks wouldn't be black, and should look wet.

Which hydraulic systems are installed in the left BLG bay ?

Probably all of them.

There are a number of things in that left body gear wheel well, including....

Servicing point for all 4 hydraulic systems.

Gear (#1)

Body Gear Steering (#1)

Inboard flap drive motor (#1 Hydraulics)

Brakes and antiskid (possibly 3 hydraulic systems, depending on the location of shuttle valves).

etc...

Stains can also be caused by grease, oil and rainwater (plus contaminants, such as brake dust).

[JammedStab]

Originally Posted by NSEU

There are a number of things in that left body gear wheel well, including....

Servicing point for all 4 hydraulic systems.

Discovered this the other day as on the walkaround, I found a hydraulic line soaked in fluid and called maintenance over. It was just the top of refill line. Made sure to wash my hands twice prior to rubbing my eyes or using the lavatory.

[onehitwonder]

Half a brain put all fuel in opposite wing

[ACMS]

Well it's been 12 years since I flew the 400 but I cannot remember the procedure for landing on 3 main gears saying to "put all the fuel in one wing...."

That isn't necessary and may just lead to an accidental fuel starvation thus giving you a whole new set of problems to work through.

Landing on 3 mains ( and even 2 ) was not a big deal in the Sim.

That's why it's called the Queen of the Skies...