Type IV fluids

[punkalouver]

""These have additional thickeners, which allows the application of a thicker fluid film and thus have significantly better holdover time performance. These properties do not come without some penalty however. Some type IV fluids have been observed to form a thick jell during dry-out and when re-hydrated form a slippery film on the aircraft. Also, some have exhibited poor "flow-off at colder temperatures"


Has anybody had any of these experiences?

[oldebloke]

The 'original' type4 was disallowed for use on the Turbo prop aircraft(Dash 8's)as the airspeed at liftoff was too slow/low to'blow' the wing clean..The Boeing 737also had to 'bug up' the takeoff speeds for the same reason..
cheers

[max lenz]

according my knowledge holdover time in snow is defined by the time when snow is not melting up anymore in the fluid but adhering to the surface.
type IV has a "dry looking" appearance and will shear off with speed.
does this mean in snowfall snow patches are allowed again due not melting on this "dry coating" and if yes what shall I check for just before departure?

[Flight Detent]

My understanding re the 737NG (27K) is that there is no need to modify any takeoff procedure following de-icing, at least down to minus 20C OAT!

Cheers, FD

[crjlover]

On the BAe 146 fleet has been reported some flight control troubles after re-hydratetion of fluid type 2 and 4.
Our new procedures now are to use fluid type 1 when it's possible (in our network only VRN FRA and MUC have it).
If the type 2 and 4 are used the crew have to inform the MX in order to arrange a "de-icing check"within 1 day from the application on the fluid.

[Swedish Steve]

Here we do a two stage deicing. We use diluted type 1 for deicing and then 100% type 2 for anticing. We used type 4 for the anticing stage for two winters, but found it difficult to get an even coating on the wing. It tended to come out in globs. Neat type 2 will produce a film on the wing quite easily. The type 4 has a better holdover time, but not by much, in fact I think that the quicker application of type 2 evens it out.

[groundog]

In Helsinki all major contractors use Type IV. Past year some SAS pilots asked not to use type IV on stabilizers on MD-80's due some operational limit set by SAS flight operations. Was it handling on critical conditions..

[alexban]

Crjlover...type 1 will give you a very short holdover time,if i'm not mistaken.I remember once using type 1,cause they had nothing else,and doing deiceing at the holding point -around 4 min holdover time in that case.
Type I fluidsare unthickened de-/anti-icing fluids on a glycol basis,and they provide protection ONLY when no precipitations occur.Under continuous precipitation the protection they provide diminishes rapidly because the fluid film on the plane is diluted by the precipitation and eventually washed off.

[alf5071h]

Try a search for deicing fluids, you will find these links amongst several other threads on the subject.

http://pprune.org/forums/showthread....deicing+fluids
http://pprune.org/forums/showthread....deicing+fluids

Also see De-Icing/Anti-Icing of Aircraft on the Ground