320: manual engine start during hot weather
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320: manual engine start during hot weather
My company has recently issued a instruction that during extremely high OAT a manual engine start should be performed in order to avoid possible excessive EGT during start. Could anyone here enlighten me as to how our why a manual engine start would result in lower EGTs over an automatic start conducted entirely by FADEC?
Personally I would prefer just to leave the FADEC to look after the whole process. In my opinion high OAT is NOT a reason for a manual start. I can't see any mechanical reason why this woiuld result in a lower start temp??
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Well, it would be because of pressure - or rather air density caused by the high temps. there is an increase in EGT which is proportional to an increase in OAT - I forgot what the ratio is -
What does the air pressure tend to do when the OAT goes up . . . that might have something to do with it.
What does the air pressure tend to do when the OAT goes up . . . that might have something to do with it.
Last edited by Natstrackalpha; 22nd Jul 2014 at 06:16. Reason: W
Have to agree with Ollie. For the life of me I can't see any difference between a normal or manual start irrespective of OAT's. Of course you would run the engine at max motoring until you got the EGT BELOW 100c BEFORE introducing fuel.
Can only think of one scenario, where, if the engineer on the ground closed the valve early after lightoff and thereby creating a hung/hot start
Can only think of one scenario, where, if the engineer on the ground closed the valve early after lightoff and thereby creating a hung/hot start
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FCOM PRO-SUP-70 Power Plant, Manual Engine Start,
"However, manual starting is recommended in the following cases:
• ......
• When expecting a start abort, because of:
• Degraded bleed performance, due to hot conditions, or at a high-altitude airfields.
@McHale, We are talking about choosing (at max motoring N2) when to select the Master switch on our selves whilst using the ENG MAN START pb-sw to open the start valve.
"However, manual starting is recommended in the following cases:
• ......
• When expecting a start abort, because of:
• Degraded bleed performance, due to hot conditions, or at a high-altitude airfields.
@McHale, We are talking about choosing (at max motoring N2) when to select the Master switch on our selves whilst using the ENG MAN START pb-sw to open the start valve.
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Airmann
There are two advantages in manual start. First FADEC uses both igniters that helps if one set is not working efficiently and also better combustion. Second you can exercise direct control over abort. In my opinion it only increases chances of successful start in adverse circumstances but may not help in achieving lower EGT.
There are two advantages in manual start. First FADEC uses both igniters that helps if one set is not working efficiently and also better combustion. Second you can exercise direct control over abort. In my opinion it only increases chances of successful start in adverse circumstances but may not help in achieving lower EGT.
