FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsHard
A technician is troubleshooting a wing leading edge anti-ice system on a turboprop that uses hot bleed air. The pressure regulating and shutoff valve (PRSOV) supplying the piccolo tube fails to close when commanded off. What is the most likely operational consequence?
- ALoss of cabin pressurization due to reduced bleed air supply
- BImmediate activation of the fuel tank inerting system
- CContinuous hot bleed air flow to the wing leading edge, risking overheat damage to the leading edge skin
- DComplete loss of engine bleed air to the pneumatic system
Show answer & explanationAnswer & explanation
Correct answer: C. Continuous hot bleed air flow to the wing leading edge, risking overheat damage to the leading edge skin
The pressure regulating and shutoff valve controls both pressure and on/off flow of hot bleed air to the wing anti-ice piccolo tube system. If it fails to close, hot air continues flowing to the leading edge even when anti-ice is not required, which can overheat and damage the thin leading edge skin.
Why the other options are wrong
- A. Cabin pressurization draws from a separate bleed air path and is not directly caused by this failure.
- B. OBIGGS activation is unrelated to wing anti-ice valve failures.
- D. A failed-open valve does not cause loss of bleed air; it causes continued flow.
Wing Anti-Ice Pressure Regulating/Shutoff Valve (PRSOV)
A valve that regulates bleed air pressure and controls on/off flow to the wing leading edge piccolo tube anti-ice system; failure to close can cause overheat damage.
- Controls both pressure and shutoff of hot bleed air
- Located upstream of the piccolo tube distribution system
- Failure to close risks leading edge skin overheat/damage
Memory trick: Stuck-open valve = leading edge left in a sauna.