B737 "LAND ALT" selector
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Join Date: Dec 1999
Location: UK
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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?
Join Date: Aug 2001
Location: Europe-the sunshine side
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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.
