Landing Gear Off?

[Jet II]

Flight Detent

On 777 and 757 in 'Normal' operation, hydraulic system pressure is not supplied to the retract actuator during extension - purely weight of the gear and airstream assistance.

Have a look at the Maintenance Manual Ch 32-32-00

[Just More Crap]

As I understand, the 767-400 can be congiured depending on the customer, so presumably a customer could choose the "UP,OFF, DOWN" if they already operated -200's/-300's, or the "UP,DOWN" if they operated 777's. Feel free to correct me. If I am correct, what would happened if you operated the 767-300's and the 777's, such as Delta?

[PAXboy]

Silly question. Noting that the gear will respond to the lever with no interlock of IAS ... if in level flight would it disrupt things much? Other than the folks at front possibly having forms to fill in when they get home?!

If the gear is extended accidentally (highly unlikly) can you just reverse the lever, or must you allow the gear to complete the extend cycle before retracting again?

thanks.

[Lump Jockey]

Pretty sure the 764 has just the up and down settings.

[Max Angle]

The reason for the difference is that on 777 and 767-400 the gear is electrically signalled rather than by a big cable attached to the back of the lever. No need to have an off position as the electronics take care of it and no need for huge great lever, a little tiny one (or just a button for that matter) will do just nicely.

[stanley]

on the A300 you can not select down by accident as you need to pull the lever as well as going down.
yes you off load the hyds to save wear and problems,

[A4]

On the A320/1, the hydraulics to the gear are inhibited above 250 knots. So even if the lever is selected down nothing will (should ) happen.

******************

Yes there would be forms to fill in but that would probably be to do with trying to locate the gear doors which would more than likely detach if the gear extended in the cruise. Of course the other big worry there is what damage they would do as they departed (and landed).

******************

I've always understood gear extention to be freefall, but damped but the fluid in the retraction cylinders. The only pressure applied is to the overcentre lock to lock the gear in place.

A4

[Tight Slot]

Jet II re 757's

Boeing Operations Manual (Landing gear - system description)

"The gear are hydraulically powered to the down and locked position. The downlocks are powered to the locked position, all hydraulically actuated gear doors close, and the main gear trucks hydraulically tilt to the flight position."

Just a quote....

[Jet II]

Tight Slot

Thanks for the correction - having read properly this time the Maint Manual, only the nose gear free falls - main gears are powered down

MM 32-34-00 page 1

Hydraulic
pressure is supplied to the retract actuator only during landing
gear retraction.

[Notso Fantastic]

A4- all very well disengaging the gear from operating above a certain speed, but many will remember the 727 that 'departed' at altitude and fell into a freefall dive. Apart from extending the speedbrakes, the Captain extended the gear (at enormous speed) to do anything to increase drag. Sure enough, the gear doors were torn off and bits of the aeroplane bent, but they survived, and I suspect maybe owe it to the gear. Airbuses are obviously great aeroplanes, but I wonder sometimes at an aeroplane that knows better than a pilot what to allow!
And I didn't even get around to the Habsheim incident!
http://www.chez.com/crashdehabsheim/ (video du crash)

[Lee]

The landing gear lever in the 747-400 has 3 positions. UP, OFF and DOWN.

When the landing gear lever is in the OFF position, the landing gear hydraulic system depressurizes.

[Pegasus912]

Paxboy

Interesting discussion a while back on accidentally selecting DOWN, when aiming for OFF!:

http://www.pprune.org/forums/showthr...&threadid=9281

[swish266]

Kestrel

It`s not a "nudge" it is a "good" pull on all 757/767. N d pull is d safety measure in flt. Some guys though still manage to go through the "off" pos when under stress at the sim.
N to close the thread B767/757 have a performance chart in the QRH "flight with Landing Gear Down". Means dat if u could not pick it up, u can at least fly it with d gear down, meaning unrestricted flight with hyd press at 3000 psi. As long as u dont run out of fuel like d poor sods from LTU at Vienna in 1999999999...
Enough guys?

[Bomber Harris]

Cornish Jack, I think you hit the nail on the head. The main reason is because there is no need to have it pressurised. Like all systems on this generation of aircrat...they are complicated. The aircraft is reauired to have an alternate extension system for certification purposes. The cheapest and most reliable alternate gear extension system is a freefall system. In order to have a freefall system you must have uplocks which can be released by a handle (or switch for the more modern boeings). So...if you have an uplock why bother to pressurise the wntire retraction system in the cruise. If it springs a leak you could dump your whole hydraulic sytsem fluid overboard in order to keep the gear in the up position...when there are uplocks to do the job. It simply makes no sense to pressurise the gear retraction system for a variety of reasons when you have a mechanical uplock system.

[Centaurus]

Kestrel. And if the gear did go down after inadvertent going through the OFF position into the down (even just a little bit down), and the IAS was above 235 knots when it happened, you cannot raise the gear again until you get below max raising the gear speed of 235 Knots. Happens in the sim a lot due pilots too quickly selecting gear off from up and not being careful of feeling for the slot (as the actress said to the bishop).