Questions on 787 Undercarriage Doors and Humidity
Thread Starter
Join Date: Dec 2000
Location: Canada
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Questions on 787 Undercarriage Doors and Humidity
Recent took my first pax trip in 787 and was lucky enough to chat with captain, a very approachable guy, in rear galley.
In the conversation he mentioned that the U/C doors automatically open after lift off and stay open for 60 seconds ready for gear retraction. I understood him to say that although there was a slight drag penalty, this is a performance requirement which I did not understand, but did not want to belabour. Could somebody please explain?
Also when discussing the cabin altitude he seemed to be saying that the aircraft carried water to raise the humidity in the cabin, did I understand this correctly?
In the conversation he mentioned that the U/C doors automatically open after lift off and stay open for 60 seconds ready for gear retraction. I understood him to say that although there was a slight drag penalty, this is a performance requirement which I did not understand, but did not want to belabour. Could somebody please explain?
Also when discussing the cabin altitude he seemed to be saying that the aircraft carried water to raise the humidity in the cabin, did I understand this correctly?
Join Date: Jun 2014
Location: Village of Santo Poco
Posts: 870
Likes: 0
Received 0 Likes
on
0 Posts
The 787-9 MLG doors open at lift-off and close after gear retraction or 30 seconds (?) whichever is first. It's a way of reducing the time taken for the gear to retract in the event of EFTO, the thereby reducing the time spent in the 'first segment'.
The 787-10 has the same design. You can see this in the numerous videos of the -10's recent first flight. The doors open immediately and then close again after a few seconds (I think it's 30, not 60). As it's a first flight, the crew deliberately leave the gear down.
The 787-8 does not have this feature.
Some of the benefits of a composite structure include:
Lighter, so lower fuel burn;
Stronger for the same weight, so bigger windows possible;
Similarly, higher diff pressure possible;
No corrosion problems so more moisture possible (higher humidity)
The 787-10 has the same design. You can see this in the numerous videos of the -10's recent first flight. The doors open immediately and then close again after a few seconds (I think it's 30, not 60). As it's a first flight, the crew deliberately leave the gear down.
The 787-8 does not have this feature.
Some of the benefits of a composite structure include:
Lighter, so lower fuel burn;
Stronger for the same weight, so bigger windows possible;
Similarly, higher diff pressure possible;
No corrosion problems so more moisture possible (higher humidity)
I wonder what the Captain was doing in the rear galley...
I certainly sometimes head there on the 777 if if I'm on a break, good for the circulation and also to see how it's going with the rear galley crew.
Last edited by wiggy; 8th Apr 2017 at 07:11.
Join Date: Mar 2017
Location: London
Posts: 170
Likes: 0
Received 0 Likes
on
0 Posts
What about wind shear after takeoff? The whole reason you don't raise the gear in windshear (even though it's creating a load of drag) is because first of all the gear doors have to open temporarily increasing drag. So I guess their procedure is different. Might as well raise the gear as the doors are already open?
The whole reason you don't raise the gear in windshear (even though it's creating a load of drag) is because first of all the gear doors have to open temporarily increasing drag.
Considering that in a windshear encounter you’ll have TOGA power on all engines, a little bit of extra drag is probably not that relevant...
