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B737 TECHNICAL QUESTIONS

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B737 TECHNICAL QUESTIONS

Old 25th Oct 2015, 11:01
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B737 TECHNICAL QUESTIONS

Hi guys,

Some questions about the 737:

1: Can somebody tell me why shimmy dampers have been installed? Is that why the aircraft is "crabing" when it is on te ground?

2: In the event of a Fire detector fault, how can you define which engine loops are faulty?

Thank you
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Old 25th Oct 2015, 15:46
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Raptor - I suggest you get your hands on FCOM 2 technical manual to answer your questions.
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Old 25th Oct 2015, 20:09
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1. To stop the nose wheel trying to break itself by going to the disco as you try to keep the a/c on the black stuff.
1a. asked an answered years ago; so click on 'search'.
2. Review Fire Test in SP's.
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Old 25th Oct 2015, 20:10
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There is a step-by-step procedure to determine the inoperative fire detection loop in FCOM.
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Old 25th Oct 2015, 21:51
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737s CRABBING ON GROUND

After 13 years on 737s various, NO FCOM which I ever read, explained the taxy crabbing.

1 day, when I was awake, doing the walkaround, I noticed the dampers on the torque links and limited castoring ability of the MLGs and realised this was how the 'frame could accept a touchdown in autoland 15kts X-wind without "squeezing"the drift off.

NONE of the TRIs/TREs of any of the UK regulated companies for whom I worked could answer the question and when l pointed it out to them subsequently, they looked suitably sheepish and surprised a G O F like me had reasoned it out.

Not one single Boeing/Company publication mentioned this mechanism on the 737 MLGs.

Hence the ability to taxy whilst pointing in a different direction!

Try pushing a supermarket trolley at speed and you'll soon realise the need for dampers on the NLG?
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Old 25th Oct 2015, 22:45
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BM: I read your thoughts, but....I've always noticed B737's seem to be pointing right and taxying straight. X-winds come from both sides on an autoland, so I'm missing something in making the same connection; assuming yours is a technically serious solution.
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Old 25th Oct 2015, 23:23
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BM
dampers on the NLG?
I assume you mean the internal
modulating valve ??
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Old 26th Oct 2015, 00:26
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Shimmy dampers on the NG are there to stop MLG shimmy. MLG shimmy is bad. We are talking ceiling panels falling down bad. After a lot of those events when the NG came (look mummy, no dampers!), Boeing decided to put the dampers back on the aircraft.
Fire loops? A and B. Test each one. The one that fails is faulty.
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Old 26th Oct 2015, 07:15
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Fire loops? A and B. Test each one. The one that fails is faulty.
priceless
clue:the nose points left in the southern hemisphere.
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Old 26th Oct 2015, 09:49
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The guy who designed the undercarriage obviously had a labrador. They too crab walk nose to the right. It made him feel at home with his new pet.
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Old 26th Oct 2015, 11:35
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The NG does't crab much. The classics do.
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Old 26th Oct 2015, 12:07
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And crabs even more...regardless of wind.
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Old 26th Oct 2015, 21:23
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MLG shimmy is bad. We are talking ceiling panels falling down bad.
Yeah. Once had the upper torque link go bonkers during rollout.
It was violent, and the cabin was a mess.
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Old 29th Oct 2015, 22:50
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AYE IT WAS A SERIOUS ANSWER!

Have a lateral pull/push at the torque links on the NLG as you do the walkround. Any play, either at the "knee" joint or at the upper and/or lower phosphor bronze bushes will warn you your classic and NG is going to rattle on taxy, start to finish. Very often manifests itself as loud vibration just after liftoff, only ceasing when the NLG tyes rub the snubbers in the bay and stop rotation.

Take a look at the MLG "knee" joints. They are not bolted tightly together as per the NLG links (wear excepted) but you may see the efisculated (shiny) section of the NLG shimmy damper, depending on where it came to rest on parking.

Then look hard in the Boeing FCOM and waste some time looking for a reference to the MLG dampers. Unless of course they've since decided to inform their pilots of this since I hung my headset up.................

However, as I said in a previous posting, your F/O will be happier to know that the 'frame will take care of the first 15kts of the landing crosswind and he/she/it only has to cope with the remainder of the X-wind component?!

I promise to get out more............
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Old 29th Oct 2015, 23:42
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Had to google efisculated and it came up with emasculated.

Fescalised is what you meant
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Old 30th Oct 2015, 18:22
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"Had to google efisculated and it came up with emasculated.

Fescalised is what you meant "

Serves me right for using big words!!

I should have said "the shiny bit which looks like a hydraulic ram".

After a few years in airline world maybe that's how we end up, emasculated??
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Old 30th Oct 2015, 18:48
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You might also wish to consider uneven tyre wear and / or incorrect nose wheel px with regard to shimmy, not simply worn bushes, relevant though they are.
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Old 31st Oct 2015, 00:25
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Boeing Aero

Download Boeing AERO 2013 Q3, theres a nice article about MLG shimmy.
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Old 13th Jan 2016, 08:57
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About the partial or all gear up landing, why is the use of speed brakes not recommended?
Also, why in the event of Hyd Sys B failure, a flaps 15 landing is recommended? ( too much stress on the electric motor extending the flaps if going for flaps 30?)

Thank you
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Old 13th Jan 2016, 10:45
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1. I think the friction coefficient between fuselage, engine nacelle and runway surface is sufficient to stop the aircraft within a normal runway's length without speedbrakes.

2. The alternate flaps system is VERY slow (0-40 is about 2 mins 30 sec). Not really nice if you get an engine failure somewhere along...
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