Helicopter Instruments and IFR-Specific Aircraft Knowledge
This domain covers the instruments and systems that make IFR flight in a helicopter safe, and the failure modes you must recognise. Candidates must know the pitot/static system, the gyroscopic instruments and their power sources, the attitude and heading reference system, and the specific helicopter systems that affect IFR capability.
Concepts to master
- Pitot/static: blocked pitot (airspeed behaves like an altimeter), blocked static (airspeed and altitude errors, vertical speed frozen), and the alternate static source.
- Gyroscopic instruments: attitude indicator, heading indicator and turn coordinator; the difference between a vacuum-driven and an electrically driven instrument, and the need for redundancy.
- AHRS and glass cockpit: what happens on a display failure and how to revert to standby instruments.
- Helicopter systems: hydraulic and stability augmentation, autopilot modes and their limits, and the effect of a system failure on IFR capability.
- Limitations: the aircraft flight manual IFR limitations, minimum equipment for IFR, and the use of the standby attitude indicator.
Common traps
Questions ask what the airspeed indicator reads with a blocked pitot during a climb (it behaves like an altimeter and increases). Another trap is assuming a glass cockpit removes the need for a standby instrument scan.
Rule of thumb
If the static source is blocked, the airspeed indicator behaves like an altimeter and the vertical speed indicator freezes; use the alternate static source and cross-check with GPS altitude.
Worked example
In a climb with a blocked static port, the airspeed indicator reads higher than actual and the vertical speed indicator stays near zero. The altimeter lags. The response is to select the alternate static source and fly attitude and power.