Message Name:

N2 SPEED IS TOO HIGH

The speed of the N2 Rotor is more than the permitted limits. During Engine operation the N2 Rotor speed is continuously monitored by the Full-Authority Digital Engine Controller (FADEC).

None

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Perform the fault isolation for the N2 overspeed condition as follows:

1. On the EICAS display system get access to the engine exceedance profile maintenance pages. Record the exceedance profile for N2 rotor speed as follows:

   • The maximum speed of the N2 rotor
   • The quantity of time that the N2 speed was more than the limit
   • If the N2 overspeed was stable or not

2. Use the exceedance profile data and the N2 overspeed limits graph (Figure 1) to find out if the N2 overspeed was in Zone A or Zone B.

   1. If the N2 overspeed is in Zone B, go to step 11.
   2. If the N2 overspeed is in Zone A, continue with next step.

3. Examine the oil pressure filter element for metal or carbon contamination. Make an analysis of an oil sample for acidity and free carbon content.

   1. If any contamination or damage found, repair as required and do close out.
   2. If no contamination or damage found, continue with next step.

4. Perform the detailed inspection of the front-bearing-chamber magnetic chip-detector.

   1. If any contamination found, repair the damage as required and do close out.
   2. If no contamination found, continue with next step.

5. Perform the detailed inspection of the rear-bearing-chamber magnetic chip-detector.

   1. If any contamination found, repair the damage as required and do close out.
   2. If no contamination found, continue with next step.

6. Perform the detailed inspection of the accessory-gearbox magnetic chip-detector.

   1. If any contamination found, repair the damage as required and do close out.
   2. If no contamination found, continue with next step.

7. To make sure that the HP rotor can turn freely without unusual noises, turn the HP rotor in a counterclockwise direction (when you look from the front of the engine).

   1. If it does not turn freely or there are unusual noises, do not use force to turn the HP rotor. There is possibly internal damage. Go to step 11.
   2. If it turn freely, continue with next step.

8. Examine the HP compressor.

   1. If any damage found, repair the damage as required and do close out.
   2. If no damage found, continue with next step.

9. Examine the HP turbine blades.

   1. If any damage found, repair the damage as required and do close out.
   2. If no damage found, continue with next step.

10. Perform an engine ground run as follows:

    • Start the engine
    • Operate the engine to ground idle, and monitor the engine operation limits
    • Stop the engine
    • Monitor the engine run down time

    1. If the above checks and inspections are satisfactory, put the engine back to usual operation and do close out.
    2. If the above checks and inspections are not satisfactory, refer to your Rolls-Royce representative and do close out.

11. Replace the power plant.
12. Do close out.