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Driver170

ENG COWL VALVE OPEN

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I checked the manual

 

Anti-Ice Systems:

• During ground turns in areas with high temperatures, you may notice the window heaters cycling off/on to maintain window heat target temperature. You may also notice that the windows require no heat at all to maintain the target surface temperature. This requires you to use the WINDOW HEAT TEST switch as a confidence test that the heaters are actually working.

• An engine anti-ice OVERPRESSURE warning lets you know that the pressure inside the ring cowl on the respective engine is too high. Follow the QRH to resolve the problem, but also take a look at the engine in the external view as the high pressure blow-out duct will be visible, allowing excess pressure to vent overboard.

 

But can't find anywhere why on the ground, ENGINES OFF and i switch on the Engine anti ice and the light remains bright blue?

 

Also checked the QRH

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Out of interest, why are you turning on the anti-ice before you start the engine? My understanding is that AI comes in after engine start

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But can't find anywhere why on the ground, ENGINES OFF and i switch on the Engine anti ice and the light remains bright blue?

 

It would probably help to dig a little deeper into why this might be the case. The logic is BRIGHT BLUE / DIM BLUE. Bright blue means that the position of the valve and the position of the switch are not in agreement. When they are in agreement again, the light will dim again. Since the valves are pneumatically operated, and there's no pressure driving them to change position, moving the knob out of the position of agreement will, logically, cause what you're seeing.

 

A lot of the time, it isn't so much that you need to look to the manual for a specific answer, as much as you need to read the section to come to an understanding. It also helps to supplement by searching other sources: http://www.b737.org.uk/iceandrain.htm


Out of interest, why are you turning on the anti-ice before you start the engine? My understanding is that AI comes in after engine start

 

Very valid point.

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Yeh thats what i read on that site, but is the APU enough?

 

I seen SWA on youtube and the Capt does his flows switching on the switches and observing the blue lights going from bright to dim. So i decided to try it but got this lol

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Odd, every flow and checklist that I have read always states AI is set after starting engines, before taxi. However, different airlines, different SOP's, and I'm not a real pilot so can only go on what I read on the internet

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The SWA pilot switched it on and off and made sure the lights dimmed when on which it did? So thats why it got me thinking

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Oh I see, maybe a specific flow they have. Makes me wonder what airlines SOP the new FS2Crew NGX reboot will use, since there is a choice of 3, apparently

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Yeh thats what i read on that site, but is the APU enough?

 

If it takes moving the throttle levers on running engines over the idle point in some cases, what might you think?

 

I don't believe the APU bleed air is routable to the TAI.


The SWA pilot switched it on and off and made sure the lights dimmed when on which it did? So thats why it got me thinking

 

Have a watch again. The WAI dims. The TAI does not.

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The wing anti ice goes dim! There has to be some sort of logic that between the 2 that i haven't properly learned yet.

 

If it takes moving the throttle levers on running engines over the idle point in some cases, what might you think?

[/quote

 

Sufficient pressure?

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The wing anti ice goes dim! There has to be some sort of logic that between the 2 that i haven't properly learned yet.

 

http://www.b737.org.uk/pneumatics.htm

 

Scroll to the bottom. Note the WAI has an entirely different route than the TAI. Your original post, however, references only TAI, so the WAI going dim is of no consequence.

 

 

 


Sufficient pressure?

 

If it occasionally takes an engine above idle power to actuate the valve, my bet would be no, even if it were routable (which I'm unsure of).

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The engine A/I valve takes pressure from the engine HP bleed offtake but it can also get pressure from the pneumatic duct if the engine bleed valve is open. So if the engine is not running the A/I valve can still open (light goes dim) if the bleed valve is open and there is pressure in the duct, for example from the APU.

 

While on ground the wing A/I closes if either thrust lever is above the Takeoff config warning point. This is where the thrust lever position plays a part. The wing A/I is opened electrically so bleed pressure is not important.

 

All this is described in the FCOM.

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So why did the SWA video blue light for engine AI go dim ?

 

In the video I saw, it was WAI on, TAI on, WAI bright>dim, TAI bright, WAI off, TAI off, WAI bright>dim, TAI dim. The TAI only went dim because the valve position (that never changed) was back in agreement after the switch was turned back off.

 

WAI

Switch || Valve

 

OFF || OFF - Dim (agreement)

Pilot changes switch position

ON || OFF - Bright (disagreement)

Valve moves open

ON || ON - Dim (agreement)

Pilot changes switch position

OFF || ON - Bright (disagreement)

Valve closes

OFF || OFF - Dim (agreement)

 

TAI

Switch || Valve

 

OFF || OFF - Dim (agreement)

Pilot changes switch position

ON || OFF - Bright (disagreement)

Valve does not move

Pilot changes switch position

OFF || OFF - Dim (agreement)

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In the video I saw, it was WAI on, TAI on, WAI bright>dim, TAI bright, WAI off, TAI off, WAI bright>dim, TAI dim. The TAI only went dim because the valve position (that never changed) was back in agreement after the switch was turned back off.

If the COWL light is dim it means the valve is open and the switch is ON. Valve closed and switch OFF would be light OFF.

 

On the SWA video I saw the Cowl lights are only bright.

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If the COWL light is dim it means the valve is open and the switch is ON. Valve closed and switch OFF would be light OFF.

 

On the SWA video I saw the Cowl lights are only bright.

 

I'll concede that, but the point remains that the video does not support that TAI was available on the ground. The bright TAI lights in the video supports my point that the switch and valve position were not in agreement (because the valve wasn't moving).

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Ahh i see it now! It remained bright blue then the guy switched it off

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Ahh i see it now! It remained bright blue then the guy switched it off

Bingo. You have a knack for picking up oddities in the most random places. Just try to stretch it into picking up those specifics when you're looking into other sources.

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Bingo. You have a knack for picking up oddities in the most random places. Just try to stretch it into picking up those specifics when you're looking into other sources.

 

I was fooled into thinking it went dim lol

 

Have to say it took that guy less than a minute to sweep that overhead.

 

Looks good doing it.

 

I visited 738 cockpit 3 weeks ago for the first time. Next time i'll get a pict with me on the RHS

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