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d. Engine Correlation.
(1)
Understanding the engine correlation factor is critical knowledge that must be fully understood. You will use the correlation factor to identify normal operation of the engine, or to analyze engine malfunctions. Indications observed inside the cockpit such as ENG OIL TEMP/PRESS, TGT, Ng, and %TRQ of both engines will correlate up and down, while the % RPM 1-R-2 will remain constant at 100%. During normal operation, brief transient fluctuations are normal.
*** To insure equal sharing of the main rotor load, a torque matching system keeps the engines within 5% torque of each other. This effectively synchronizes the engine power outputs and the result of torque matching is a relative balance between all No. 1 and No. 2 engine instruments.
(2)
When one engine changes its power output, the other engines governing system, the Electrical Control Unit (ECU), makes an opposing power change to maintain the % RPM R at 100%. Retarding the No. 2 Power Control Lever (PCL) will cause the No. 2 engine instruments to correlate down indicating a power reduction in the No. 2 engine. Automatically, and simultaneously, the No. 1 engines instruments correlate up indicating a power increase to maintain % RPM R at 100%.
(a)
Engine Malfunction Identification. With the UH-60 being a dual engine aircraft, correcting power plant related malfunctions begins with identifying the malfunctioning engine. This skill is critical and must be mastered. After the malfunctioning engine has been positively identified, corrective action is taken on that engine by manipulating the corresponding controls. With this in mind, it should be noted that mishaps have occurred due to the misidentification of the malfunctioning engine, and/or manipulating the wrong engine controls. Take your time and get it right the first time.
(b)
Engine Malfunction Identification General Rules: An accurate method of identifying which engine is malfunctioning is summarized in the following general rules: LO-LO-LO and HI-HI-HI. The first rule mentioned is the LO-LO-LO, which refers to the following indications and symptoms.
The first LO is a low RPM R, or a % RPM R below 100%. This is indicated on the PDU.
The second LO refers to the engine power, specifically, the malfunctioning engine power. This information is verified using the engine correlation factor to properly identify the malfunctioning engine.
The last LO is referring to a low side failure of the ECU (or a power loss), which is most likely the cause, and is pilot correctable. Other causes of a power loss could be the catastrophic failure of an engine or the drivetrain, which is not pilot correctable.
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