Max Q
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Joined: Wed May 09, 2001 12:40 pm

B747 Pushback and towing

Wed Feb 14, 2018 10:03 am

When pushing back or towing the 747 is the body gear steering activated ?


I believe this system is hydraulically powered, how is it pressurized before an engine is started, electric hydraulic pumps ?


If it’s normal to use body gear steering for push back and towing Is there a reason where you would not use it ?
The best contribution to safety is a competent Pilot.
 
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fr8mech
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Joined: Mon Sep 26, 2005 9:00 am

Re: B747 Pushback and towing

Wed Feb 14, 2018 10:25 am

Yes it is. Body gear steering (along with the nose) operates off the #1 hydraulic system. The #1 hydraulic system can be powered by the Engine Driven Pump (EDP) or the Air Driven Pump (ADP). Additionally, the -8 has a AC Motor Pump (ACMP) installed in the #1 system.

The -100/200's were essentially the same as the -400, though some did have the additional ACMP in the #1 system.

If you're towing a dead airplane, there is no body gear steering available.
When seconds count...the police are minutes away.
 
Max Q
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Re: B747 Pushback and towing

Wed Feb 14, 2018 10:49 am

Thanks for that, with engines off does this ADP receive bleed air from the APU ?


I assume if you have to tow a dead aircraft you have to make fairly wide turns with no body gear steering or you could get tire scrubbing?
The best contribution to safety is a competent Pilot.
 
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fr8mech
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Re: B747 Pushback and towing

Wed Feb 14, 2018 10:54 am

Max Q wrote:
Thanks for that, with engines off does this ADP receive bleed air from the APU ?


I assume if you have to tow a dead aircraft you have to make fairly wide turns with no body gear steering or you could get tire scrubbing?


Yes, the APU can supply the ADP's. On the -400 and -8, they are installed in systems 1 & 4. On the -100/200, they are installed in all 4 systems.


Yup, slow, wide turns. You can turn tight, but you will get scrubbing...the lighter the aircraft, the better. Same thing if you're taxiing the aircraft with an inop BGS system. Slow, wide turns. The way we park aircraft here, an inop BGS system is a tow in and tow out of the parking spot.
When seconds count...the police are minutes away.
 
Max Q
Topic Author
Posts: 6064
Joined: Wed May 09, 2001 12:40 pm

Re: B747 Pushback and towing

Wed Feb 14, 2018 11:04 pm

Thanks for the information
The best contribution to safety is a competent Pilot.

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