737NG anti ice /Emergency Descent
Thread Starter
737NG anti ice /Emergency Descent
Hi,
The memory items for an Emergency descent include the sentence
"Reduce thrust to minimum or as needed for anti-ice"
I can't find a reference in the FCOM or anywhere stating what the minimum N1 is with either Engine or wing anti-ice on.
Can anyone point me in the right direction?
Thank you
The memory items for an Emergency descent include the sentence
"Reduce thrust to minimum or as needed for anti-ice"
I can't find a reference in the FCOM or anywhere stating what the minimum N1 is with either Engine or wing anti-ice on.
Can anyone point me in the right direction?
Thank you
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I believe Some MEL procedures require higher minimum thrust settings(N1) for anti icing operations.
If you operate with said MEL restrictions in icing conditions then you would have to comply with the higher minimum thrust setting, even in emergency descent.
If you operate with said MEL restrictions in icing conditions then you would have to comply with the higher minimum thrust setting, even in emergency descent.
Framer, no specific knowledge about the 737NG, but on the current Boeing wide-body airplanes, selecting engine anti-ice will automatically give you "approach idle", which will provide sufficient bleed pressure for engine and wing anti-ice.
I "believe" the 737NG works the same way, but I don't "know" that it works the same way.
I "believe" the 737NG works the same way, but I don't "know" that it works the same way.
As mentioned for the classic, the NG retains the requirement for 60%N1 in icing conditions with the 9th Stage INOP'd.
I took an aircraft with this fault a week or two back. Also limits the Aircraft to CAT I as the A/T is inop.
I took an aircraft with this fault a week or two back. Also limits the Aircraft to CAT I as the A/T is inop.
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Low Idle produces the bright blue lights, you mainly see it for Wing Anti Ice on the ground with low power settings. So im guessing its enough N1, so you dont see the bright blue lights (Anti-Ice Valve operation is pnuematic from memory) Try turning on the Anti-Ice on ground with out the engines operating and youll see what I mean
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Wing Anti Ice on the ground turns on or off depending on temperature though, not depending on N1. Idle is normally sufficient on the ground to keep both engine anti ice and wing anti ice operating. The cowl anti ice valves are electrically controlled but pneumatically operated (simply by bleed pressure). Wing anti ice valves are however AC operated.
As Jwscud mentioned any requirement for more than approach idle in flight with anti ice on is triggered by operating according to a MEL item as far as i know.
As Jwscud mentioned any requirement for more than approach idle in flight with anti ice on is triggered by operating according to a MEL item as far as i know.
Thread Starter
Note: The wing anti-ice VALVE OPEN lights may cycle bright/dim due to the control valves cycling closed/open in response to thrust setting and duct temperature logic.
I always thought it was just from temperature but the above statement seems to back up Wang's statement.
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But Denti, if you increased N1 on ground, The bright blue lights for Wing Anti Ice go dim! So it is somewhat dependant on N1
The switch/light logic is:
light off-switch off and valve is closed
light dim- switch is on and valve is open
light bright-switch and valve position disagree or valve is in transit.
The wing anti ice valves are electrically activated/driven (as Denti pointed out). When on the ground there are two things that will automatically shutoff the wing anti ice.
Overheat protection via overheat thermal switches in the L/R leading edges. If either switch is triggered at 257°F the valves in both wings will close.
If the thrust levers are advanced, switches in the autothrottle switch pack close and send a signal to close the anti ice valves. This is done to conserve engine power for takeoff.
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The wing antice bright disagreement lights appear when on the ground(EAI/WAI selected ON but valves closed) if wai duct temp get above 125 C despite max ground cooling and /or if thrust lever angle above 35 degrees.