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737 autoland nose up

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737 autoland nose up

Old 4th Feb 2021, 00:07
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737 autoland nose up

Anyone know for how many units is aircraft aiming when trimming at 400' during autoland? I couldn't find this information in the fcom. Only states it nose up trim.
Regards
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Old 8th Feb 2021, 10:00
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It likely variable, depending on the FMC current MAC
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Old 8th Feb 2021, 10:15
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I wouldn’t know, but on the 737 the FMC isn’t anywhere near as fundamental as more modern types so my gut instinct is that it wouldn’t be involved in pitch trim. But I don’t have al the manuals and haven't flown one for 15 years so I could well be talking bollocks (why change the habit of a lifetime!).
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Old 8th Feb 2021, 10:22
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goeasy

ah negative, you give aircraft too much credit for information transfer, we talking about shit heap from the 60s at heart, pretty sure you can do auto land with double FMC failure
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Old 8th Feb 2021, 10:26
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Anyone know for how many units is aircraft aiming when trimming at 400' during autoland?
The amount of flare spring bias is not fixed. It is calculated by the FCCs based on the stabilizer position and flap setting.

depending on the FMC current MAC
FMC on the 737 has nothing to do with the autoland. You can dispatch without both of them and still retain full Cat III capability.
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Old 8th Feb 2021, 13:29
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Originally Posted by Dzosefs View Post
Anyone know for how many units is aircraft aiming when trimming at 400' during autoland? I couldn't find this information in the fcom. Only states it nose up trim.
Regards
On average the trim wheel is wound 13 times. I think you have to wind the trim wheel 10 times and 15 times respectively on the CL and NG for one unit of trim.

I am going by memory. I don't claim this to be exact information and I don't know how relevant this would be.
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Old 8th Feb 2021, 14:48
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Interesting question, it does but the amount I cannot recall. The B747 classic in. dual-channel used to add 2 units ANU, and that predated the 737 ALAND capability, would think it would be close to that, which is around the incessant whirring that Banana Joe indicates.
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Old 8th Feb 2021, 21:43
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The Autopilot is flying the aircraft. The FMC provides mach trim and speed trim, hence the comment about performing CAT III autoland W/O FMC is valid. (as long as the AP is fully functional)
The pilot will have to manually trim the ac if the FMC's are inop. and can still perform a CAT III autoland procedure.

Is the question how to manually trim the ac below 400' on final???
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Old 8th Feb 2021, 22:05
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FMC provides speed and mach trim on the 737? Are you sure​​​​​​?
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Old 8th Feb 2021, 22:12
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Well, the 737s without FMCs could still do autolands and had mach trim, so...
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Old 8th Feb 2021, 23:05
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Originally Posted by turbidus View Post
The Autopilot is flying the aircraft. The FMC provides mach trim and speed trim, hence the comment about performing CAT III autoland W/O FMC is valid. (as long as the AP is fully functional)
The pilot will have to manually trim the ac if the FMC's are inop. and can still perform a CAT III autoland procedure.

Is the question how to manually trim the ac below 400' on final???

Ah you got some bogus info in there. Yes, you can do an auto land with no FMCs. That part is correct. However, the FMC has nothing to do with trimming for an auto land, so the trim will work just fine without the FMCs. Not sure where you are getting this info. The proof of the pudding is in the “auto land limitation summary” in the QRH. It lists all the equipment requirements, nowhere does it mention an FMC.
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Old 9th Feb 2021, 01:51
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Originally Posted by turbidus View Post
The Autopilot is flying the aircraft. The FMC provides mach trim and speed trim, hence the comment about performing CAT III autoland W/O FMC is valid. (as long as the AP is fully functional)
The pilot will have to manually trim the ac if the FMC's are inop. and can still perform a CAT III autoland procedure.

Is the question how to manually trim the ac below 400' on final???
F *C* C, perhaps?
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Old 9th Feb 2021, 11:02
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Originally Posted by turbidus View Post
The Autopilot is flying the aircraft. The FMC provides mach trim and speed trim, hence the comment about performing CAT III autoland W/O FMC is valid. (as long as the AP is fully functional)
The pilot will have to manually trim the ac if the FMC's are inop. and can still perform a CAT III autoland procedure.

Is the question how to manually trim the ac below 400' on final???
Manual trim with AP(s) engaged on a 737?

Last edited by BraceBrace; 9th Feb 2021 at 13:25.
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