Type II/IV fluid question

[punkalouver]

Must type I fluid always be used first before using type II or IV fluid.

[Empty Cruise]

Depends if your company de-icing manual approves 1-step de-icing. If yes, you can choose to both have the contamination removed & the anti-icing added by one application of Type II or IV. However, since rehydration nearly always will be greater if using a one-step procedure, there might be combinations of contamination & moderate/heavy precipitation where you might go for a two-step procedure none the less.

...errr, I think... :O

Brgds
Empty

[punkalouver]

The reason I asked was because in an article in the Nov 2004 Business and Commercial Aviation, it said "It should be noted that unless all surfaces are aerodynamically clean, the aircraft must first be de-iced with type I fluid."
However this is in a paragraph about protecting aircraft parked for extended periods of time. Apparently some operators use fluids if an aircraft is parked.
It also says that "all type II/IV fluid must be removed with Type I fluid before departure if the parking time has exceeded four hours"

Anyone familiar with these practices.

[alf5071h]

punkalouver a search for ‘type 4 fluids’ might help with your question.
Also see AEA Recommendations for De-Icing / Anti-Icing of Aircraft on the Ground Twentieth Edition September 2005 (www.aea.be/AEAWebsite/Presentation_Tier/Pr_GroupMenuItem.aspx?NodeID=rootMenu398)

The specific point about spraying parked aircraft is the problem of using thickened fluids (type 2/4) as an overnight anti frosting agent. These fluids can dry out (glycol content evaporates) leaving a powdery residue of thickening agent, colorant, etc. The thickener can absorb many times its own volume of water and thus freeze in flight.

There have been incidents involving aircraft flying with a dried-out anti frosting layer, which rehydrated in cloud/rain, formed a gel which then flowed/collected in ‘aerodynamically quite areas’ i.e. control gap/hinges, and froze.

Use of a type 1 fluid before flight washes off any dried-out fluid residue, irrespective of de/anti icing being required.