POWER ASSURANCE CHECK
The performance check allows to verify the engine condition over a wide
range of ambient temperatures without exceeding any limits. The
performance check should be performed
• after engine installation
• at regular interval as per flight manual
All forms of engine deterioration can cause increased ITT and fuel
consumption at a given power settings. Compressor deterioration causes
increase of Gas generator speed (NG) at given power. Hot section
deterioration causes decreases in NG at given power settings.
The physical aspects considerably influence the performance parameters of
an installed engine. For this reason, the completed hover power checks
procedure is described in Section 4 - Performance Data of the AW139 RFM.
Refer to this section for a detailed description.
In general, the charts establish acceptable engine parameter limits for
different atmospheric conditions. The check is performed at a given power
(normalized torque), in Hover Flight (NR=100%).
Refer to RFM – Section 1 for power margin trend monitoring requirements.
EXAMPLE
Given:
• TQ = 97%
• Pressure Altitude = 3000 ft
• OAT = +10°C
• ITT = 645°C
• NG = 90%
SOLUTION
1 Entering the left of the graph at 97% torque.
2 Drop down to the Pressure Altitude curve for 3000 ft.
3 Move right to the +10°C OAT curve for Maximum Allowable ITT and
Maximum allowable NG.
4 From the +10°C OAT curves move vertically up to an ITT value of
655° C and NG value or 92%.
CONCLUSIONS
The recorded ITT value of 645°C is less than the maximum allowable
(655°C) and the NG value of 90% is less than the maximum allowable (92%)
so the engine is acceptable for flight.