Hyd A Press 737-ng
Thread Starter
Joined: Sep 2003
Posts: 16
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From: Miami
Hyd A Press 737-ng
Hi,
Take a look at this picture:
http://!!!!!!!!!!!!!!/open.file/294127/M/
Upper EICAS. HYD A P is indicating 0 although the HYD Q is 94%.
What can be the cause of this? Are the pilots taxing with the HYD A System OFF?
I am confused...
Thank you
Bruno Francescoli.
Take a look at this picture:
http://!!!!!!!!!!!!!!/open.file/294127/M/
Upper EICAS. HYD A P is indicating 0 although the HYD Q is 94%.
What can be the cause of this? Are the pilots taxing with the HYD A System OFF?
I am confused...
Thank you
Bruno Francescoli.
Joined: Aug 2003
Posts: 69
Likes: 0
From: New York
Unless the flightcrew is taxiing with both Engine Driven and Electric Pumps OFF (unlikely), then I suspect that the most likely cause is an MEL'd System A Hydraulic Pressure Indication System.
Very observant
Very observant
Joined: May 2002
Posts: 93
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From: Australia
Boeing procedures recommend that if pushback is conducted without the use of the nose wheel steering bypass pin, system A hydraulic pumps should be off. If they have just completed the pushback, maybe they are using this procedure.
My company uses the bypass pin so both systems are pressurised during pushback.
Are there companies out there that DO NOT use the bypass pin for pushback?
AA
My company uses the bypass pin so both systems are pressurised during pushback.
Are there companies out there that DO NOT use the bypass pin for pushback?
AA
Joined: Oct 2002
Posts: 166
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From: uk
AA,
I agree,I was also going to suggest the picture was taken during/shortly after a pushback without the steering pin.The nosewheel steering is supplied with A sys px so the pumps would need to be off during push to stop the wheels centering and shearing the towbar.
I agree,I was also going to suggest the picture was taken during/shortly after a pushback without the steering pin.The nosewheel steering is supplied with A sys px so the pumps would need to be off during push to stop the wheels centering and shearing the towbar.
Joined: May 2002
Posts: 132
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From: USA
I don't know of any companies not using the bypass pin but there are companies that take the added step of pushing with A system depressurized.
There are operaters out there with all three types of 737 and it would make sense to keep from popping towbars since the older -200's didn't have a bypass.
There are operaters out there with all three types of 737 and it would make sense to keep from popping towbars since the older -200's didn't have a bypass.
Thread Starter
Joined: Sep 2003
Posts: 16
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From: Miami
Thanks a lot 7p3i7lot, so basically what the Nosewheel steering bypass pin does is that it prevents hydraulic presure to reach the Nosewheel so that Ground Crew may push, turn and do whatever they need to without problems, right?
If this system is not installed (Like in the picture) HYD SYS A should be Turn Off so that no hydraulic presure reaches the Nosewheel since the bypass pin is not installed, correct?
Hope I got it!
Once again, thank you all.
Bruno Francescoli.
If this system is not installed (Like in the picture) HYD SYS A should be Turn Off so that no hydraulic presure reaches the Nosewheel since the bypass pin is not installed, correct?
Hope I got it!
Once again, thank you all.
Bruno Francescoli.
Joined: Jul 2002
Posts: 368
Likes: 0
From: brisbane, Australia
Sorry If I sounded sarcastic Eng123,didn't mean too,but A/C ops requires it to be operated occasionly (how often I don't know..any-one ??).After viewing the Piccy suspected it was the case..If it hasn't been operated recently it can make a racket and give erronous feel for a few seconds (Air in plumbing ??)
cheers
cheers
Last question, I swear! :p
Joined: May 2002
Posts: 132
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From: USA
The nose strut mounted bypass valve was an option on the -200's.
To muddy the waters a bit more, the pin actually holds a handle in position. The handle actuates a valve which causes the steering control fluid to bypass the steering actuators thus allowing the nose strut to be rotated freely. There's a couple of different valve types so the handle and valve are mounted in different positions on the strut depending on the series of aircraft.
To muddy the waters a bit more, the pin actually holds a handle in position. The handle actuates a valve which causes the steering control fluid to bypass the steering actuators thus allowing the nose strut to be rotated freely. There's a couple of different valve types so the handle and valve are mounted in different positions on the strut depending on the series of aircraft.
Joined: Aug 2001
Posts: 755
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From: Europe-the sunshine side
on that pic ,the plane is stationary (gs=0),just after push and engine start. (engines are at idle thrust,and also flaps=0 ) ,and both sys A hyd pomps off.
Many ops recomand sys A off for pushback,as a suppllementary protective meassure.
You don't want to meet some smart guy who'll forget to install the pin.I'd met one who forgot to remove it
so,why not the opposite?
Many ops recomand sys A off for pushback,as a suppllementary protective meassure.
You don't want to meet some smart guy who'll forget to install the pin.I'd met one who forgot to remove it
so,why not the opposite?
