Boeing 767 Hydraulic/Electrical Question
Thread Starter
Join Date: Jun 2005
Location: Western Hemisphere
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Boeing 767 Hydraulic/Electrical Question
Hiya, I am looking for some clarification with the 767.
I understand that the ADP pump supplies hydraulic power to the center system as long as there is bleed air pressure available. This hydraulic pressure then in turn provides pressure to drive the HDG which provides electrical power to the system. The RAT only provides hydraulic pressure to the flight controls. My question is, suppose you are having a real lousy day and you lose both engines and have no apu. Since you no longer have bleed air, you now have no hydraulics and the only source of electrics other is your battery. You only have flight controls. Is this correct?
Alta
I understand that the ADP pump supplies hydraulic power to the center system as long as there is bleed air pressure available. This hydraulic pressure then in turn provides pressure to drive the HDG which provides electrical power to the system. The RAT only provides hydraulic pressure to the flight controls. My question is, suppose you are having a real lousy day and you lose both engines and have no apu. Since you no longer have bleed air, you now have no hydraulics and the only source of electrics other is your battery. You only have flight controls. Is this correct?
Alta
Join Date: Oct 2002
Location: Heathrow
Posts: 291
Likes: 0
Received 0 Likes
on
0 Posts
Yes it is, but its late and I may have forgotten something.
Just to add some discussion into the mix:
If you have an U/S APU and have a generator failure on takeoff during in low visibility procedures - you may well stop where in other situations you wouldn't.
The reason being that you wouldn't have two sources of electrical power (excluding the battery), so you couldn't autoland.
If the APU is U/S and a genny fails, then you have to land ASAP (only 1 source). If you have a genny failure and can use the APU as a second generator, you can continue.
It would have to be really bad day for both the gennys and the APU to be broken.
Just to add some discussion into the mix:
If you have an U/S APU and have a generator failure on takeoff during in low visibility procedures - you may well stop where in other situations you wouldn't.
The reason being that you wouldn't have two sources of electrical power (excluding the battery), so you couldn't autoland.
If the APU is U/S and a genny fails, then you have to land ASAP (only 1 source). If you have a genny failure and can use the APU as a second generator, you can continue.
It would have to be really bad day for both the gennys and the APU to be broken.
Join Date: Mar 2006
Location: Australia
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Jetstream Rider
It would have to be really bad day for both the gennys and the APU to be broken.
Just to theorize a little further (and stray into the never could happen zone)
With the loss of both engines and a failure of the Rat to extend and/ or function correctly would the windmilling engines provide any, or adequate pressure to operate the flight controls?
With the loss of both engines and a failure of the Rat to extend and/ or function correctly would the windmilling engines provide any, or adequate pressure to operate the flight controls?
Join Date: Jun 2001
Location: Surrounded by aluminum, and the great outdoors
Posts: 3,780
Likes: 0
Received 0 Likes
on
0 Posts
If u lose both engines, and now the RAT malfunctions, you are indeed having a bad day, if airspeed is high enough, you might have enough windmilling energy to power the eng-driven hyd pumps, but not too sure of that either
Join Date: Aug 2003
Location: US
Posts: 24
Likes: 0
Received 0 Likes
on
0 Posts
There is also a min speed for the RAT. It is 135kts. There was an aircraft that was hijacked and they ran it out of gas. It crashed into the ocean just off a beach. There was a video of it and as it slowed it lost control and entered the water with one wing low. They figured it was because they got below 135kts and could no longer control the ac.
Join Date: Oct 2002
Location: Heathrow
Posts: 291
Likes: 0
Received 0 Likes
on
0 Posts
I define the Gimli Glider as a "bad day"! Hence I stand by my previous comment.
A few RAT's have been tested and found to stick in the up position, so no RAT is not beyond belief.
A few RAT's have been tested and found to stick in the up position, so no RAT is not beyond belief.
