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Old 7th Jul 2019, 18:15
  #30 (permalink)  
QuarterInchSocket
 
Join Date: Sep 2016
Location: Amongst the Gum Tree's
Posts: 80
Originally Posted by CV880 View Post
B2N2 is clearly referring to 747 operations.
I did consider the 747CL along with the 737CL both of which share similar characteristics with respect to issues relating to starting reliability. My rubbish talk is geared toward the modern machines and despite etops apu controls not applying to the heavies as is the case with some of the lighter twins, the learnings relating to apu performance from the more stringent controls of an etops program I would reasonably assume to apply to apu’s more broadly. Airlines, apu manufacturers and airplane manufacturers do monitor many metrics including MTBF of components on an apu both on-wing and as a result of overhaul etc. They’re watching! If there was a trend, they’d react... or at least, that is the expectation from historical occurrences and experience.

to op - apologies if my prev post has caused offence. I see many people try to reinvent the wheel, some of the suggested shapes that get churned out aren’t very well thought out. The latest rediculous one came from a chap who saw nothing wrong with leaving the apu bleed on with packs switched off on the ground (737NG). I can’t recall if there is mechanical risk to apu health in this config, but I do know that it results in approx 40% loss of efficiency, half that (20%) if only one pack is used for the 131-9b on 737ng, (off the top of my head); I can’t remember where I read it so I wouldn’t be able to produce evidence even if I tried! Hah.
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