FAA Aviation Mechanic General (AMG)Ground Operations and ServicingMedium
A ground crew applies a two-step deicing/anti-icing treatment before departure in freezing precipitation: Type I fluid to remove existing ice, followed by Type IV fluid. What is the specific purpose of the Type IV application?
- ATo heat the airframe surface and melt any residual frost
- BTo provide a longer holdover time by preventing new ice or frost accumulation before takeoff
- CTo remove any remaining Type I residue from the airframe
- DTo lubricate control surfaces prior to flight
Show answer & explanationAnswer & explanation
Correct answer: B. To provide a longer holdover time by preventing new ice or frost accumulation before takeoff
Type IV fluid is a thickened, unheated anti-icing fluid designed to remain on the aircraft surface and provide extended holdover time, delaying the formation of new ice or frost until takeoff, unlike Type I which is heated and used only to remove existing contamination.
Why the other options are wrong
- A. Type IV is applied unheated and is not intended to melt frost—that is Type I's role.
- C. Type IV is not a rinsing agent; it is applied for its anti-icing protective properties.
- D. Deicing fluids are not used as lubricants for flight control surfaces.
Deicing/Anti-Icing Fluid Types
Fluids used to remove and prevent ice accumulation on aircraft surfaces before flight, categorized by type and holdover time.
- Type I: heated, unthickened, removes ice
- Type IV: thickened, unheated, longest holdover time
- Two-step process common in severe icing conditions
Memory trick: Type IV = Four extra hours of frost-free protection.