"Gear UP and OFF"
 

I have noticed in older Boeing A/C that the gear is raised by moving the level fully up, as you'd expect. But later in the climb, it is moved to the centre OFF position, turning off the hydraulics to the now retracted gear.

All that makes sense, but I'm slightly concerned by the fact that the lever is being moved downwards towards the gear down position.

Would it be possible to actually lower the gear if you made a mistake and didn't stop the lever in the centre?
This could damage the gear and prob rip the doors off as well. http://www.pprune.org/ubb/NonCGI/eek.gif

Or is there a system that prevents this?

On the Airbus and newer Boeings its just down or up......

------------------
Live long and Prosper.....

Thats never going to happen [moving from Up to Down & not Off]under normal circumstances thats why Indication lights are present.
The Doors & Landing gears are syncronized mechanically in most Aircrafts too.
regds
HAWK.

Swashplate

How can lowering the gear damage the doors?

Placing the lever in the OFF position off-loads the hydraulic system. Further acceleration does not take place until the the gear is verified as 'up and off'. But if the gear was accidently lowered nothing would happen except that the gear would go down.

I was thinking of them being ripped away by windblast.

I just wanted to know if you could inadvertently lower the gear if you accidentally went past the OFF position to DOWN. Or is there some mechanical device to stop this? Similar to the system that prevents gear up on ground?

Not having a pop at anyone, just interested.

------------------
Live long and Prosper.....

Yes.

On the B737 at least, when moving from Up to Off, it is possible to overcook it slightly and go past the off position into the realms of gear down. Trust me - my friend did it.

As for damage, it wouldn't hopefully be a problem as the max speed for lowering the gear is 270Kts or 0.82M. You should have been unloading the hydraulics by moving from "up to off" well before acceleration up to this speed after take off. Normally in the region of 210 - 250 Kts at that stage so plenty of mnargin.

Trouble comes as max retraction speed is 235Knots, so you may well have to slow down before you can bring the Dunlops back in again!

Hope this clears it up!

SR

Yeh Swash it is easy to go through the OFF to the "DOWN" area if your not careful with the gear handle. Sink Rat is right.
Most 737 drivers will ensure the gear is in the OFF detent before passing 270 knots.

Thanks chaps! V informative.

Good to see you are all on the case wrt this!

I was imagining a nightmare scenario where one of the crew made this mistake, the nose doors were torn off by windblast, and sucked into engines........... http://www.pprune.org/ubb/NonCGI/eek.gif

scary!!

Perhaps if would have been better to have:

OFF

UP

DOWN

Or is this too much like common sense...?? :) :)



------------------
Live long and Prosper.....

Swashplate:-
The problem with your suggestion would be inadvertantly switching the gear "OFF" when trying to retract! That would cause the hydraulics to be turned off, and the gear to stick in its present position. http://www.pprune.org/ubb/NonCGI/redface.gif (I assume.)
I can honestly say that the situation has never presented itself, to my knowledge, on my type. (B757/767.) There is a detent at ;

UP.
OFF.
DOWN.

You have to lift the lever into it, so it would have to be a definate move to put it from UP to DOWN, bypassing OFF! Perhaps its slightly easier to do on the B737. Also I believe that the only "NEW" Boeings that doesn't have this setup is the B777 and the B767-400.
Eff Oh.

Thanks eff oh!!

I din't know you had to 'lift it in', that must be the system I was asking about. I thought it was just moving a lever to a detent.

Perhaps you have a point about my system. Maybe the older aircraft should have had the OFF system on a separate lever??

IMHO, the modern up/down is best.....

------------------
Live long and Prosper.....

Swashplate
You're quite right - there is a possibility that moving the lever past OFF from UP COULD damage the doors, if it was done at too high a speed. It's taken care of by my present company and the previous one (both 744) by making the move at the Flap 5 selection. That way you are guaranteed to be below door speed.

On the 777 the gear handle has only "down" and "up". And it's a tiny little thing!

On mixed fleets 757/767-400 this can become a problem. As the -400 doesn't have an OFF the ingrained habit is to pull the handle back down after retraction. The sim instructor warned of this problem, but sure enough. "Gear up, off, oops! up again." The instructor said that in the case of an inadvertent extension it is kosher to snap the handle back up.

A common problem when converting to the 737. On every course, several pilots (often most) will inadvertently go past the off position once or twice - just a tad is enough to cause an expletive of frustration by the pilot concerned.

Initial training emphasises holding around the flap up speed plus a little until PNF has had time to ensure flaps up, lights out, and the handle back to off before PF accelerates to the initial clean climb speed.

The only problem is, as indicated by others above, if the speed is above the retraction limit when the gear handle is moved beyond off. This will require the aircraft to be slowed while the problem is rectified.

After a few sessions everyone seems to get the hang of it and the clean up and acceleration is done in a steady smooth progression.

On line operations, the problem occurs rarely, but is always good for the occasional humbling experience .....

[ 08 July 2001: Message edited by: john_tullamarine ]

Swashplate,
Its not just the older Boeings that have an 'OFF' position for the gear. I'm flying a brand new 737NG and its got the off position. :D

Been there done that! :)

You only do it once!

Our company just changed the SOPs for the Gear Off-Position. Up to no we had do switch the gearlever to the off position while doing the after take-off checklist (gearlever as a reminder). Now we have to switch the gearlevere to the off-position at the command flaps up (737). It was changed to prevent an unintendet lowering of the gear above 270 kts.

Denti

If inadvertently extending gear and heavy, you might have to extend flaps so that you are able to slow down enough to meet retaction limit of 200kts (B727)

seupp

Yeah I`ve done it once in a 733 too. Makes a lot of noise but not a problem as long as you don`t retract it again until decreasing speed.

It will occur, when doing the after take-off checklist, if the microswitch is set too close to the neutral position and makes contact if the lever goes only a mm past. That was my excuse anyway and that particular aircraft did actually have an history of the gear re-appearing.

Like someone else said, you only do it once!

My A300-605r has up than off as well.

But virtually all aircraft have a slower retract speed than extension speed.

Cheers
WIno

I make a real point of very slowly selecting the gear to off, particularly in turbulent conditions. Some of the guys I have flown with just fling it to the off position, and it always $h!t$ me up!