Leading edge de-icing question

[perkin]

Any suitably qualified pro's able to tell me what kind of temperature the leading edges of the wing and fan cowls get up to when anti-ice is operating? They're supplied directly with bleed air, correct? Just curious as last time I flew in a 737 (couple of weeks ago) I was sitting just ahead of the wing looking down the leading edge, and descending through what appeared to be heavy rain or hail, no idea if it was icing conditions, whatever liquid that came into contact with the leading edges appeared to be evaporating - it could of course just be an aerodynamic effect, but I was curious if the anti-ice systems could reach a temp sufficient to evaporate water. Thanks in advance for any sensible replies :)

[TightSlot]

Will move thread to Tech Forum

[Nepotisim]

Air from engines regulated to approx 180 degrees celcius. (Approx as all aircraft are going to differ somewhat)

So therefore the air temp would be that or lower depending on the distance from the engine. Enough to boil water I guess.

[Short_Circuit]

Can't answer for 737 but for 747 RR,

Ref Boeing 747-400 Maint Manual 30-11-00

3 . Wing Anti-Ice Control Valves

A.
The flow of air into the wing anti-ice ducts from the engine pneumatic
system is controlled by a 3-1/2-inch shutoff valve in each wing. The
butterfly type valve is driven open and closed by an internal electric
motor. The valve has limit switches to prevent overtravel and valve
position switches for fault indication. The valve has an external
position indicator which shows the position of the valve, and a handle
which allows the valve to be operated manually.
B.
The wing anti-ice valve opens and closes in less than 3 seconds. The
valve operates under a normal bleed air pressure of 45 psi at a
temperature of approximately 350°F - (177°C), and is designed to operate in
external ambient temperatures of -65 to +300°F and with ducted air
temperatures of -65 to 490°F. The valve will operate in altitudes to
45,100 feet.

S_cct

Sorry nepotisim for the non type answer but your post was not visible when I posted mine.

[Blacksheep]

Some types I've worked on were wired through the air/ground system to prevent activation unless the aircraft had airflow over the wing. Structural damage can occur through prolonged use on the ground.

[displaced gangster]

B717-200
Wing & Tail leading edge.
Manifold temperatures (downstream from the precooler) & regulated by the Pneumatic system controller (PSC).

Airframe ice protection off < FL200---177c.
" " " " > FL200---210c
" " " on all levels---249c

Level 2 alert Bld Air Temp Hi/Lo 280c/200c respectively.

Engine nacelle.
Unable to find nacelle values.:8

[FE Hoppy]

On the E-Jets with Wing anti ice on the leading edge monitor will signal low temp below about 45C and over heat at 110C.
The bleed duct temp will control around 232C.

[perkin]

Thanks for the answers people! So refreshing not to be flamed for being a curious pax on PPRuNe!!

I guess its highly possible that the leading edges were indeed evaporating the water...wasnt sure if it was just an odd visual effect of the water streaming off at high speed...Wouldve asked the flight crew post flight, but, as usual, in a bit of a hurry to get home...! Cheers :)

[Mad (Flt) Scientist]

Our (Bombardier) L/E AI are generally designed to be "evaporative" rather than "running wet" and the temperatures are similar to those quoted above. I'm pretty sure what you were seeing was evaporation.

Evaporative is desirable from an aerodynamic point of view because it means you don't have to worry about ice/water running back and then refreezing once it gets to the cold/unprotected part of the wing.