Which airline keeps the gear lever up until landing?

[Hardy Heinlin]

Hi,

as far as I recall, I heard of at least one airline that keeps the gear lever up until landing in order to keep it under hydraulic pressure (maybe for safety reasons). I can't remember whether it was the 744 though.

Does anyone remember?

I'm asking because the autobrakes are typically armed when descending through 15000. I've learned that on the BA sim the autobrakes cannot be armed while the lever is up. Perhaps this is airline specific?


Regards,

|-|ardy

[John H Watson]

KLM did this for a while. I don't know if it was a temporary measure. I believe it was to do with maintenance issues regarding alternate gear extension checks. It's probably mentioned on one of the PS1/PSX forums.

Cheers
JHW

[John H Watson]

It may relate to gear doors drooping in flight (again a maintenance issue)....

From another forum..

Incidents like this happened to my airline and several other 744 operators causing some serious damage to gear doors. Obviously it's not the crew who deliberately puts the gear handle in the DOWN position during cruise. It's the incorrectly adjusted cables for the landing gear control and/or alternate extend cables. Remember, the previous revisions of 744 AOM and checklist used to call for gear handle to OFF position at a certain point into the flight. Years ago that step was deleted from the manuals and checklists. No more GEAR HANDLE...OFF. Simply they leave the handle in the UP position for the entire flight. The only reason to dump pressure (GEAR HANDLE to OFF) from the gear extension and retraction system is purely for alternate extend only, (plus a bunch more for maintenance). Yes...the pilots keep those internal locks of the gear door actuators pressurized for the entire flight. No more ripped off doors, no more surprises in your backyard. 

As we know, this is airline specific.

Cheers
JHW

[Hardy Heinlin]

Thanks!

I conclude: When KLM did this (perhaps they don't do it anymore) they put the lever to OFF at 15000 to be able to arm the autobrakes, or they armed the autobrakes on approach after gear extension.


Cheers,

|-|ardy

[Britjet]

You wouldn't arm autobrakes on approach - far too late, and would have to have been armed previously to comply with the descent checklist.
Peter.

[Britjet]

Out of interest - the 777 does not have an OFF position as you will probably know - just UP or DN - the hydraulics are automatically depressurised after the gear is up and door uplocks have engaged.
To be honest I'm still struggling to see why anyone would want to keep the 747 system pressurized. It goes against 747 system operation and checklist logic, and invites a hydraulic leak over time.
(It is actually quite easy, by the way, to have a gear door droop after retraction if you are too quick to move the lever to OFF - I've done it myself several times - that is why the Boeing checklist (now) leaves the OFF selection to the end of the after-take-off checklist) - but that is really a carelessness issue rather than paranoia about a door droop.)
Once the door uplocks have engaged - why should the gear droop? I've never heard of it happening with my previous airline, unless there was an uplock fault which would have been dealt with by QRH or subsequently the MEL, once the fault manifested itself.
Peter.

[John H Watson]

(EDIT: The big sim may be wrong)

Sensed brake hydraulic pressure from pedal input will inhibit arming. However, looking at my manuals, the metered brake pressure seems to be sensed only in the Normal brake hydraulic system. Autobrakes do not work with the alternate braking system (which is used for despin after takeoff). Despin occurs with the gear lever up (and hydraulics are available)

Cheers

Hardy: Ref Airframe Book 2/p661 for hydraulic system schematic.

[John H Watson]

P.S. If it is real, it must be a mechanically or hydraulically induced thing. Electrically, the landing gear lever only produces a "Down" and "Not Down" signal. No electrical system can tell the difference between UP and OFF.

[John H Watson]

I asked the question on the PRuNe forum... BA Sim #3 does not behave the same way as the one tried earlier. #3 is a GE sim. Which one was tried earlier?

[Hardy Heinlin]

So is this incorrectly modelled in that other BA sims, and PSX was correct?

[John H Watson]

and PSX was correct?

That would seem to be the case (Of course, a third sim could cast the deciding vote... or Peter could go to the same sim (first one) and try it again... Perhaps it's been fixed?)

There is simply nothing on the aircraft which could tell the Autobrake system that the gear is specifically in OFF or UP.

Cheers
JHW

[John H Watson]

Also, a KLM guy just responded saying that they no longer use that procedure (and that he never had any problems in the past arming the Autobrakes with the gear lever up.

Cheers
JHW

[Britjet]

We weren't using BA sim 3 for the reason you mention - it has a lot of non-BA mods on it.
I'm in the BA sim again at the weekend and will happily test it again.
Peter

[Gary Oliver]

<disregard>

[John H Watson]

Thanks Peter.

By the way, I just heard that Sim #4 also behaves the same way as Sim #3 (no problems with Autobrake with gear up). Is that a Roller?

Cheers

[Hardy Heinlin]

In some sims the engine models can be changed by a switch during the session; as the landing gear model is probably not related to the engine model, it would also be nice to know which sim was built by which sim company (CAE, Thales, Thomson, etc.). Perhaps such differences in certain system parts also occur in the sim parks of other airlines. E.g. Lufthansa has three 744 sims; two are from CAE and one from Thomson or Thales, I think.


Cheers,

|-|ardy


Edit:

Here's a short summary of the BA sims:
https://www.britishairways.com/en-gb/baft/airline-training/flight-simulators/747-400-flight-simulators

Are there any publications by BA that show some more details?

Here are some publications by Lufthansa:
https://www.lufthansa-flight-training.com/documents/10156/18501/Boeing+747-400+FRA+%28FT14%29
https://www.lufthansa-flight-training.com/documents/10156/18501/Boeing+747-400+FRA+%28FT16%29
https://www.lufthansa-flight-training.com/documents/10156/18501/Boeing+747-400+FRA+%28FT48%29

There is an official table somewhere in the Internet that lists all current sims worldwide with manufacturer names etc., but I can't remember the link.

[Gary Oliver]

We were in Sim 4....

[John H Watson]

We were in Sim 4....

Then it would appear some other factor was in play here. Temporary glitch? Were there any malfunctions set?

[Gary Oliver]

A anonymous source from pprune?  Go with that then...

[John H Watson]

A(n) anonymous source from pprune?  Go with that then...

I hope all my posts on PPRuNe and the PSX forum are anonymous, too. The guy who said Sim #3 didn't do what you saw, was also anonymous. The guy who said he worked on KLM and had no problems with the A/B was also anonymous.

When something really doesn't sound right to me, I keep asking questions. If you can explain, technically, why it does it, then I will change my mind on the subject. I can find no technical reason for the behaviour you saw, and I know for sure that big sims break and have their programming shortcomings. All sims do. Jon posted a video a few months ago in a big sim which showed unrealistic ECS synoptic pack behaviour.