FAA Aviation Mechanic Airframe (AMA)Hydraulic and Pneumatic SystemsMedium
A pneumatic wing deicing boot system uses engine bleed air and vacuum to alternately inflate and deflate tube sections along the leading edge in a repeating pattern. Which component controls the timing and sequence of air delivery to the individual inflatable tube sections?
- ARestrictor fitting
- BDistributor valve
- CPressure reducing valve
- DEjector
Show answer & explanationAnswer & explanation
Correct answer: B. Distributor valve
The distributor valve (often a rotary or timer-driven valve) cycles bleed air pressure and vacuum to the different boot tube sections in the proper sequence, producing the characteristic inflate/deflate pattern that sheds accumulated ice from the leading edge.
Why the other options are wrong
- A. A restrictor fitting only limits flow rate in a line; it has no timing function.
- C. A pressure reducing valve lowers bleed air pressure for boot operation but doesn't sequence the tubes.
- D. An ejector uses a venturi effect to create suction (vacuum) for deflating the boots, but it does not control timing/sequence.
Deicing Boot Distributor Valve
A timer-driven valve in a pneumatic deicing system that sequences bleed air pressure and vacuum to inflatable boot tube sections to shed ice.
- Creates the alternating inflate/deflate cycle
- Works with an ejector for vacuum during deflation
- Powered by engine bleed air pressure for inflation
Memory trick: Distributor 'deals the cards' of air to each boot section in order