B-737NG Auto LAND
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Join Date: Jan 2001
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B-737NG Auto LAND
Gentlemen,
For some reason, the B-737-800 (NG) will not have the additional nose up trim input at 50 feet AGL as the classic series did. Most of the autolands I have experienced in the NG have been rather firm as compared to the somewhat smooth touchdown we had in the B-737 classics (-3,4,500). I asked an expert (Somebody who knows more and more about something less and less) and he told me that the NG-series takes into consideration the "geometry of the airport runways" in the FMS DATABASE for its flare and therefore the secondary nose up trim input at 50 feet AGL was not necessary anymore. Anybody out there with some more info on this?
For some reason, the B-737-800 (NG) will not have the additional nose up trim input at 50 feet AGL as the classic series did. Most of the autolands I have experienced in the NG have been rather firm as compared to the somewhat smooth touchdown we had in the B-737 classics (-3,4,500). I asked an expert (Somebody who knows more and more about something less and less) and he told me that the NG-series takes into consideration the "geometry of the airport runways" in the FMS DATABASE for its flare and therefore the secondary nose up trim input at 50 feet AGL was not necessary anymore. Anybody out there with some more info on this?
Join Date: Aug 2002
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For some reason, the B-737-800 (NG) will not have the additional nose up trim input at 50 feet AGL as the classic series did. Most of the autolands I have experienced in the NG have been rather firm as compared to the somewhat smooth touchdown we had in the B-737 classics (-3,4,500). I asked an expert (Somebody who knows more and more about something less and less) and he told me that the NG-series takes into consideration the "geometry of the airport runways" in the FMS DATABASE for its flare and therefore the secondary nose up trim input at 50 feet AGL was not necessary anymore. Anybody out there with some more info on this?
Did it ever occur to that sometimes the "obvious" is smacking you in the face because it is the "detailed explanation" you seek??
The B737NG and Classic have the same flare inputs (or additional nose up trim you call it). The autotrim command for the B737-800/900s have been redcued because of the size in comparision to the shorther versions...hence the rougher landing. There is no consideration for "geometry of the airport runways" . The Autopilot doesn't care about that. It doesn't not dwelve into the FMC database and determine that one runway might be shorter than another.
So to answer your question, the secondary nose trim command hasn't been taken away, but has been reduced.
Did it ever occur to that sometimes the "obvious" is smacking you in the face because it is the "detailed explanation" you seek??
The B737NG and Classic have the same flare inputs (or additional nose up trim you call it). The autotrim command for the B737-800/900s have been redcued because of the size in comparision to the shorther versions...hence the rougher landing. There is no consideration for "geometry of the airport runways" . The Autopilot doesn't care about that. It doesn't not dwelve into the FMC database and determine that one runway might be shorter than another.
So to answer your question, the secondary nose trim command hasn't been taken away, but has been reduced.
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Sometimes in these forums, you can get some very useful information about the workings of a system or various procedural dealings with a problem but then again, you may not. Anyhow, thank you for your reply.
