Anti ice with flaps up or down ?
 

Question as title, what does your operation do, thinking mainly jet ops ie airbus Boeing but I imagine its similar for most types.

Eg1. on stand with flaps up and it starts snowing ? Apply anti ice ( de ice first) but what about the flaps ? They go down after engine start but they also extend so what about the unprotected sections ?


Eg2 landing in snow. Taxy in with flaps out for an inspection, de ice and anti ice before start but do the flaps go up after de ice or remain out for anti ice ? Does that remove some of the fluid from the surface ?

Be interested to read thoughts or ops.

Good questions and there will be many different answers I'm sure...

Prior to takeoff:

If the aircraft's surfaces are contaminated (except for flaps because they were retracted at the time) but there is no more precipitation falling, then I would de-ice with Type I and leave the slat/flaps in the retracted position.

If the precipitation is still falling then after Type I, I would request Type IV anti icing fluid and I would set the slat/flap setting to my takeoff configuration of that day. Once anti iced and prior to taxi I would retract the slat/flaps to avoid contamination while taxiing.

After landing:

If I suspected moderate to heavy icing, I would not retract the slat/flaps fully until a visual inspection was accomplished. In any case if you were to do a turnaround they would have to be selected down to de-ice them.

JJA4 is right - there will be many answers.


On the Dash 8, we typically de-ice with Flap 15, then reposition to the takeoff flap setting (0, 5, 10, 15 - depending on conditions & supplement applicability) once the spray is complete.


Now, considering the Dash is a high-wing aircraft, there is not the need to worry too much about spray from the wheels hitting the flaps during taxi, but on low wing aircraft I too would consider raising the flaps once the spray was complete (assuming there was no restriction in the AFM).


After landing, I think JJA4 has it spot on - if landing in moderate to heavy icing, leave them where they are until you can inspect the airplane.

Interesting - we use a different procedure here than +TSRA. Before departure, we are required to leave the flaps at 0 for deicing (DH8-400). The reasoning behind this is that a heavy crust of ice may or may not break before the flap system gets damaged if one tries to move them. So the flaps stay up and are only set into the takeoff position after treatment.

After landing, there are no considerations with regards to the flap system on the book. As has been mentioned, the spray from the main wheels will pass well below the flaps. The problem lies with the nose gear though: the radio altimeter antennas right behind the nose gear can and will accumulate much slush in some conditions, so the taxi speed is restricted in these conditions and a check for contamination in this position is required before departure (usually, quickly washing the mud off during deicing is appropriate). After an approach in severe ice, a check before retraction may of course be well advisable.

On the F70/100, it was different due to the low wing. After landing on a slushy runway, the flaps were not to be retracted above 25° during taxi. On the parking stand, one would then quickly wipe the leading edge clean, switch on the electric hyd pumps and wind the flaps in. Failure to do so could firstly lead to the flaps icing up in a position where no glycol could ever get and getting damaged and secondly win the culprit a free ticket to a one-way briefing sans tea or biscuits.

For the 747 Boeing says to de-ice/anti-ice with the flaps up and make sure you extend them before takeoff. Leave them out after landing.

In the dim and distant past, the recommendation was to de-ice and/or anti-ice with flaps retracted and deploy them at the holding point when cleared for departure.

One of the reasons quoted was the ground engineers "didn't like it as the fluids removed the lubricant off the screwjacks" and also such an accretion of Type X on the flap mechanism may freeze at cruise temps and cause restriction when trying to deploy for landing.

But that was then, when men were men and had sheep for breakfast........................:)

2013-14 FAA HOT Tables contains the following (on page 3)

That's actually a less committal statement than last year, when I believe they discussed a 50% penalty for HOT with deployed high lift devices.

In the end common sense is required but one should also follow the recommendations of the aircraft manufacturer when de-icing and anti icing.

737NG procedure is to deice with flaps up and then cycle the flaps from Up to 40 and back to Up before taxi to verify freedom of movement (assuming they're not covered with snow and remote de-icing will be conducted) and taxi to the holding point with the flaps up.
Stops contamination being thrown up by the wheels into the flaps, slats and the mechanism which could then lead to an interesting takeoff when retracting them, and it helps with the holdover.
Also taxi in with flaps extended if a contaminated runway and check for contamination in the flaps on arrival before retracting them.

..,SUPPLEMENTARY procedures that is...oh :mad: another manual to open..:E