B737 "LAND ALT" selector
Thread Starter
Joined: Dec 1999
Posts: 2,584
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From: UK
B737 "LAND ALT" selector
A question for anyone who flies 700 - 900 series 737s.
When setting the LAND ALT before departure do you round up or round down the arrival rwy altitude? Does it matter - after all, only 50 feet is involved. What is Boeing Standard, and why?
My feeling is that as the cabin lands "slightly pressurised" ( Boeing OM Vol II) rounding it down could result in a landing pressure equivalent to up to 50 ft below the surface, plus the "slightly pressurised" element, plus any barometric variable, ie QNH about to change) which could cause a pressure bump in the cabin, whereas rounding up would minimise this. Previous company insisted vehemently that rounding up was essential, present one doesn't seem to have much of a view. Our trainers tell different stories.
Ideas?
When setting the LAND ALT before departure do you round up or round down the arrival rwy altitude? Does it matter - after all, only 50 feet is involved. What is Boeing Standard, and why?
My feeling is that as the cabin lands "slightly pressurised" ( Boeing OM Vol II) rounding it down could result in a landing pressure equivalent to up to 50 ft below the surface, plus the "slightly pressurised" element, plus any barometric variable, ie QNH about to change) which could cause a pressure bump in the cabin, whereas rounding up would minimise this. Previous company insisted vehemently that rounding up was essential, present one doesn't seem to have much of a view. Our trainers tell different stories.
Ideas?
Joined: Aug 2001
Posts: 755
Likes: 0
From: Europe-the sunshine side
No problem whatsoever, otherwise Boeing would have specified which way to set it. The cabin will be 200' bellow land alt ,and 50' plus or minus won't make such a difference. It is not a pressure bump,it's a controlled depressurize of the cabin. So,if you add 50' ,it will take a 'bit' longer.
