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Pilot53

anti ice valves

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In the pmdg ngx if you switch the anti ice on without a bleed source or just apu bleeds, the lights go bright but not dim indicating the valve doesnt open fully. is this correct behavior? I thought the anti ice valves were electrically controlled.  Also it is part of the pre-flight to check the operation of these valves if icing is anticipated during flight.

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Hi Mike,

I hope this answers your question/s:

 

COWL VALVE OPEN:- BRIGHT : related cowl anti-ice valve is in transit, or,
cowl anti-ice valve position disagrees with related
ENGINE ANTI-ICE switch position.
- DIM : related cowl anti-ice valve open (switch ON)
- EXTINGUISHED : related cowl anti-ice valve closed
(switch OFF)

 

LEFT AND RIGHT VALVE OPEN LIGHT:- - BRIGHT : related WAI control in transit, or, related
WAI control valve position disagrees with WAI switch
- DIM : related WAI control valve is open (switch ON)
- EXT : related WAI control valve is closed (switch OFF)

 

WAI- Wing Anti ice

 

the anti ice switches are usually turned on when it is supplied with bleed air either from the engine or APU,it is not normal to turn it on the ground without bleed air.

And would be hazardous if turned on during the preflight.I dont think i need to explain why.

 

Ground-inhibited Wing Anti-ice:
 The air/ground sensor prevents the wing anti-ice control valves from opening on the ground except
during ground test. A ground overheat thermal switch in each wing closes the wing anti-ice control
valves in case of overheat during ground test. Activation of either thermal switch closes both valves.

 

EDIT: as an answer to your question:

 

PWR TEST :
- Provides a confidence test (Window Heat Switches must be ON).
- Controller is forced to full power, bypassing normal temperature control. Overheat protection is still
available.
NOTE : Do not PWR TEST when all green ON lights are illuminated.

 

warm regards,

H.Mahesh

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The short answer is that the anti-ice valves are pneumatic and need bleed pressure to open. If there is no pressure available you get a disagreement indication of you try to open them.

 

Engine A/I uses engine bleed pressure only so duct pressure from the APU will not open those valves.

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The engine A/I valves are correctly simulated in the ngx.

The wing A/I valves are not correctly simulated. The wing

A/I valves on the real 737 do not require bleed air pressure to open. During preflight the engine A/I lights will be bright during the engine A/I check. The wing A/I lights should go bright then dim regardless of available air pressure during the wing A/I preflight check.

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The wing A/I valves are not correctly simulated. The wing
A/I valves on the real 737 do not require bleed air pressure to open.

Yes, my mistake, you are correct. Wing A/I valves are operated by an AC electric motor. The logic in the NGX is as if they are powered by a pneumatic motor. If they are open and you remove duct pressure they stay open. Pneumatic valves are usually spring loaded to close without pressure. So it looks as if the wing A/I valves are simulated as motor driven (correctly) but with the wrong power source.

 

Someone should open a support ticket.

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Yes, my mistake, you are correct. Wing A/I valves are operated by an AC electric motor. The logic in the NGX is as if they are powered by a pneumatic motor. If they are open and you remove duct pressure they stay open. Pneumatic valves are usually spring loaded to close without pressure. So it looks as if the wing A/I valves are simulated as motor driven (correctly) but with the wrong power source.

 

Ok this is what I thought as well. 

 

 

 

Someone should open a support ticket.

Done.

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