WAI

[Hardy Heinlin]

Just to be sure. Is it correct that the hot WAI air in the left and right wing isn't connected by a tube in the aircraft center? The hot WAI air in one wing cannot move into the other wing and vice versa?

Please note: I don't mean the bleed duct that connects both WAI valves via the left and right isolation valves, which is shown on the EICAS synoptic. I mean the air on the other side of the WAI valve: the air that heats the LE.

Thank you!


Cheers,

|-|ardy

[Hardy Heinlin]

OK. It's confirmed :-) No connection.

I learn from this: Should one of the two ISLN valves fail to open with two engines out on one wing, forced to fly at low humid altitudes, say, over the ocean for some hours, ice may build up on one wing, asymmetrically.

The wing on the bad engines may decrease its lift even more ...

Rising instability ... interesting scenario.


Ahoi,

|-|ardy

[Jeroen D]

Rising instability ... interesting scenario

Should be! I've never seen any reference anywhere to this happening, so if and when it does, be interested to see how you need to deal with it.

I've not been able to find an abnormal procedure/checklist for this one!

Jeroen

[dutch57]

Hardy goodmorning,

Nice scenario,,,

But easy to resolve, checking the Non-normal checklist and FCOM.

Avoid operating in icing conditions, simply divert to a better enviroment.

sincerly Bob

Ps icing conditions are usually set in the TMA of an airport , en-route at a cruising level temp and humidity are beyond ice forming conditions.

[Hardy Heinlin]

Good morning Bob,

two engines out after takeoff with 400 tons, now dumping fuel below FL80 for an hour in icing conditions ...


|-|

[dutch57]

Hardy up-date checking the ECL for the msg WAI VALVE LEFT(RIGHT) procedure is ,

WAI VALVE LEFT (RIGHT)
Condition: Wing anti--ice valve not in commanded position.
 *WING ANTI-ICE Switch AUTO
– WING ANTI-ICE Switch . . . . . . . . . . . . . . . . . . . . . . . . ON
* WAI VALVE remains displayed
– WING ANTI-ICE Switch . . . . . . . . . . . . . . . . . . . . . OFF
* Do not use wing anti--ice to prevent asymmetrical
ice buildup.
Procedure completed.
* WAI VALVE no longer displayed
AFTER LANDING
– ENGINE BLEED P/Bs (Affected side) . . . . . . . . . OFF
– ISOLATION VALVE P/B (Affected side) . . . . . . . OFF
– Disregard FLAPS PRIMARY and HYD PRESS DEM
alerts during flap operation.
S LE flaps will retract in secondary mode.
Procedure completed.
* WING ANTI-ICE Switch ON
– WING ANTI-ICE Switch . . . . . . . . . . . . . . . . . . . . . . . . OFF
* Do not use wing anti-ice to prevent asymmetrical
ice buildup.
Procedure completed.
* WING ANTI-ICE Switch OFF
– WING ANTI-ICE Switch . . . . . . . . . . . . . . . . . . . . . . . . ON
AFTER LANDING
– ENGINE BLEED P/Bs (Affected side) . . . . . . . . . . . . OFF
– ISOLATION VALVE P/B (Affected side) . . . . . . . . . . . OFF
– Disregard FLAPS PRIMARY and HYD PRESS DEM
alerts during flap operation.
* LE flaps will retract in secondary mode.
Procedure completed.

Bob

[Hardy Heinlin]

Does anybody familiar with Auto-WAI know if the auto control closes the WAI valves every few minutes to let ice accumulate and then break it? This way no melted water would run behind the LE and refreeze at unprotected places.

Or can this on-off de-icing method (de- not anti-) be performed only manually?


Cheers,

|-|ardy

[Hardy Heinlin]

Just learned something new. The ice detector uses a probe that vibrates at 40 kHz. When ice builds up on the probe, the probe gets heavier and its vibration slows down accordingly. This frequency is sensed. Then a heater is activated that melts the ice on the probe. This may take ca. 10 seconds. This is one cycle. If the melting takes longer or occurs repeatedly, the cycle count increases. At 2 cycles, nacelle icing level is sent to EICAS. At 10 cycles, wing icing level is sent to EICAS.

I conclude, wing anti-ice seems to activate 1 to 2 minutes later than nacelle anti-ice. The system lets the wing accumulate some ice before it starts the de-icing.

However, I still don't know if WAI stays on once it has started. It probably stays on until the aircraft is off the icing area.


|-|

[Jeroen Hoppenbrouwers]

How much time does need to pass without a thawing cycle in order to cancel the nacelle and wing icing events?

[MEade]

I can't answer for the Queen, but in the E190 the system will activate automatically upon detecting an ice condition, and will continue to operate until no icing condition is detected for a duration of 5 minutes.

[Hardy Heinlin]

In the E190, when WAI has activated automatically, do you sometimes deactivate it manually after a few minutes in order to avoid water running back?

[MEade]

Under normal circumstances, no. However once the system has detected ice, we get a STALL PROT ICE SPEED message that latches until 30 seconds (could be 10 seconds depending on which manual read) after WOW. The message indicates a change to the activation threshold for the stall warning system. I think, in part, Embraer do this is because, as you suggest, ice formation could occur due to the water running back, and also to deal with ice possibly forming on other parts of the aircraft that aren't protected, such as the fuselage.