A question about 747 body gear steering
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A question about 747 body gear steering
I'm just wondering, why is the body gear steering armed for taxi and dis-armed for take-off? The way I understand the system, it's the nosewheel steering that makes the body gear steer, so on take-off, if you don't touch the tiller, the body gear should remain centered.
Or am I screwed up.
Ray
Or am I screwed up.
Ray
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On the 744 the body gear steering is automatically activated when the nosewheel steering is greater than 20 degrees and the airplane speed decreases below 15 knots.
As ground speed increases through 20 knots, the body gear are automatically centered and body gear steering is deactivated.
As ground speed increases through 20 knots, the body gear are automatically centered and body gear steering is deactivated.
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Yes, the Nosewheel hyd is deactivated by a pin, but how about the boddy gear steering?
The pushback can allso make tight turns, and as far as I can see, the boddy gear steering allso turns, or is it me imagine things...??
[This message has been edited by Roger Turbojet (edited 26 December 2000).]
The pushback can allso make tight turns, and as far as I can see, the boddy gear steering allso turns, or is it me imagine things...??
[This message has been edited by Roger Turbojet (edited 26 December 2000).]
Guest
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Yep as long as sys 1 is pressurized and BGS armed the Body gear will still operate during push back, I've seen it done with the switch in disarm once and left some very nice scrub marks.
[This message has been edited by CCA (edited 26 December 2000).]
[This message has been edited by CCA (edited 26 December 2000).]
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The steering tiller is back driven, it moves as the pushback tug pushes you round a corner, as stated a pin is inserted in the NWS metering valve to purely deactivate the hyd input to the NWS actuators. As soon as the nose wheels go past 21 deg the body gear starts to turn and is progressively incresad as the nose is turned further, can't remember the amount the BLG turns at the moment.
Guest
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Thanks for the info, guys. Still, it makes you wonder, if the body gear needs to be disarmed for takeoff, then why is not there a warning light on the pilots annun. panel that the thing is armed(at least on the 200, I was not trained on the 400)?
Happy new year,
Ray
Happy new year,
Ray
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On the 747-200s I flew the take-off warning horn (Unsafe T/O configuration warning) would sound if take-off was attempted with the body gear steering not centered. The book did not actually state that the warning system monitored the body gear arming switch position, it just said the horn sounded if the gear was not centered. Pity we grounded the 200s or I could have experimented for you!
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Guest
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Received this email so am doing a favour and posting here.
<font face="Verdana, Arial, Helvetica" size="2">I am not a registered user but have the answer to the above item.
The original 747's had no Body Gear Steering Disarm switch; it as operative all the time with gear down. A Northwest 747 went off the runway during TO at Tokyo Haneda in the very early 70's when the nose gear skidded on a wet and slippery runway (Haneda was notorious) probably due to applying power before being completely lined up on a rolling TO. Steering tiller inputs to correct the slide resulted in the body gear steering assisting the departure from the runway as the body gear had a lot more grip and say over which way the ship went than the nose gear.
As a result of the NTSB investigation the Disarm switch was mandated by an AD. Until the switch was fitted I think the steering had to be turned off by tripping the control circuit breaker on the overhead panel prior to take off (Can any old time 747 drivers or F/E's confirm??). The NTSB chap who headed the investigation sat in on some L1011 training I was doing at Lockheed in 74 or 75 so it must have happened in 72 or 73.
Cheers</font>
The original 747's had no Body Gear Steering Disarm switch; it as operative all the time with gear down. A Northwest 747 went off the runway during TO at Tokyo Haneda in the very early 70's when the nose gear skidded on a wet and slippery runway (Haneda was notorious) probably due to applying power before being completely lined up on a rolling TO. Steering tiller inputs to correct the slide resulted in the body gear steering assisting the departure from the runway as the body gear had a lot more grip and say over which way the ship went than the nose gear.
As a result of the NTSB investigation the Disarm switch was mandated by an AD. Until the switch was fitted I think the steering had to be turned off by tripping the control circuit breaker on the overhead panel prior to take off (Can any old time 747 drivers or F/E's confirm??). The NTSB chap who headed the investigation sat in on some L1011 training I was doing at Lockheed in 74 or 75 so it must have happened in 72 or 73.
Cheers</font>
Guest
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All right, I'll buy the ad note. It still seems kind of odd that there is no warning light that the system is armed.
Thanks for the info everyone. I am sure as my over-whelming career in air frieght continues, I'll have some more 747 questions.
dc8 "more type ratings than you can shake a stick at" Ray
Thanks for the info everyone. I am sure as my over-whelming career in air frieght continues, I'll have some more 747 questions.
dc8 "more type ratings than you can shake a stick at" Ray
