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A20N Engine Start

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A20N Engine Start

Old 16th Sep 2020, 18:23
  #21 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
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Originally Posted by Bus Driver Man View Post
Only dual cooling/cranking. The actual start is still one by one.
(On the A380, 2 engines are started simultaneously. But the APU is more powerful to be able to do that. No idea about the A340 and B747.)
One the 747-400 (with autostart) and the 747-8 you can start two engines at a time - although if you're at higher altitudes you probably don't want to.
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Old 17th Sep 2020, 07:02
  #22 (permalink)  
 
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Originally Posted by tdracer View Post
One the 747-400 (with autostart) and the 747-8 you can start two engines at a time - although if you're at higher altitudes you probably don't want to.

Curious to know what happens when there isn’t enough ‘puff’ to start two engines simultaneously in that scenario


Will the auto start / FADEC abandon the start(s) if adequate rotation is not achieved within a specific time period, close to starter duty cycle limits ?


Assuming it would not allow fuel on in this circumstance ?
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Old 17th Sep 2020, 17:27
  #23 (permalink)  
 
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Originally Posted by stilton View Post
Curious to know what happens when there isn’t enough ‘puff’ to start two engines simultaneously in that scenario


Will the auto start / FADEC abandon the start(s) if adequate rotation is not achieved within a specific time period, close to starter duty cycle limits ?


Assuming it would not allow fuel on in this circumstance ?
That's basically correct - the autostart measures how long it takes of N2 (or N3) to accelerate - if it's too slow it aborts and puts up the ENG X AUTOSTART message on EICAS (and sets a CMC message as to the cause).
Apparently that's happened during single engine starts on the Large Cargo Freighter 747-400 (aka the Dream Lifter). As part of the mod, they removed the APU (running the fuel and pneumatic lines through where the fuselage swings open would have been problematic) so they need a ground cart. Turns out not all ground carts are up to the task...
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Old 17th Sep 2020, 23:14
  #24 (permalink)  
 
Join Date: Sep 2007
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LEAP

Originally Posted by Fursty Ferret View Post
Simultaneous engine starts?
My shop is all LEAPS. I think we're up to 75 or so neos now.
The P&W have an extra bus start option I understand, where one engine can be in its start cycle when the other is cranking.
Interestingly, there is no documented limitation on a serial start on the LEAP, and I've been told dual starts are the norm on pre delivery flights. I'd try it in the Sim, but my knuckles are going to be rapped enough...
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