ODV/HMU

Question 1

ODV functions (HOPS)

Answer 1

1. Hot Start Prevention shuts fuel flow at
   900°C.
2. Over-speed protection (NP) from DEC at
   120+1%
3. Purges main fuel manifold and allows back flow of high-pressure air for purging.
4. Sends fuel through manifold to

Question 2

HMU functions (PM CAN VDTO)

Answer 2

1. Pumps fuel at high pressure
2. Meters fuel to ODV in response to PAS,
   LDS, trq. motor from DEC, & eng. variables.
3. Collective Pitch Compensation through the LDS. When the collective is moved, Ng is reset for immediate Np response.
4. Accel/Decel flow limiting preventing comp. stalls, eng. damage, or flame out.
5. Ng limiting – Limits max torque available under low temp conditions.
6. Variable Geometry Positioning of the inlet
   guide vanes for optimum performance.
7. DEC/EDECU lockout PAS Override& Control with ECU Inoperative. Allows pilot to mechanically bypass torque motor inputs.
8. Torque Motor to Trim Ng Output. To fine tune engine output. Can be overridden in DEC lockout.
9. Opens Vapor Vent for manual HMU priming, to remove air from HMU.