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(#1 engine instruments are correlating high as high side failure of #1 ECU trims #1 engine power to maximum. #2 engine governing system (ECU) senses increasing RPM R via it’s increasing power turbine speed, it compensates by decreasing it’s power as far back as idle, MR rpm is driven up solely by the high side #1 engine. Initial action is to adjust collective if required, in this case #1 Eng.’s Np O/S function is limiting %RPM R to 106% so increasing collective to load M/R is not required, and it would dump more fuel into the high side engines combustion chamber. To get M/R rpm back into normal range, retard the #1 PCL to reduce maximum power available of #1 engine allowing the #2 engine to govern the M/R at 100% (high side #1 engine driving rotor no higher than 106% due to Np O/S function)
(#2 engine decoupled from the M/R, with it’s P/T governing at 103% due to load share function)
2. LEARNING STEP 2: Identify abbreviations used in discussing the T-700 engine.
a. The T-700 and its systems function are very similar to other Army turbine engines. The abbreviations listed in this section are common abbreviations used when discussing the operational characteristics of the T-700 engine.
(1)
Nr (Main Rotor Speed): Main Rotor speed (Nr) is the largest power user and must be driven at a constant speed, it normally rotates at 100% (258 rpm). Both engines through a direct mechanical connection of the two power turbines supply power to the main rotor. The power turbines also rotate at 100% (20,900 rpm).
(2)
Np (Power Turbine Speed): Power Turbine Speed (Np) drives the main rotor. Two power turbines are mechanically linked to one main rotor via the drivetrain. Power turbine operational components consist of a two-stage power turbine rotor, a power turbine shaft, a splined adapter, and a highspeed shaft assembly.
(3)
Ng (Gas Generator Speed): The purpose of the Gas Generator speed (Ng) is to drive the Power Turbine's speed (Np). The Ng section generates power in the form of gas pressure by continuously combusting a fuel/air mixture. The Ng sections main parts are a six-stage axial/centrifugal compressor, and a two-stage Gas Generator turbine (GG) rotor assembly.
(4)
AGB (Accessory Gear Box): A gearbox that mechanically drives engine accessory components, every AGB component is driven relative to NG speed via the Power Take Off (PTO).
(5)
PTO (Power Take Off): The Power Take Off (PTO) is a gear that drives a radial drive shaft, which mechanically links the AGB and Ng. Simply, the Ng section powers all of the AGB components through the PTO.
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