SYSTEM FUNCTIONING WITH BOTH POWER PLANT ENGINES OPERATING

Engine control is performed by means of:

- Engine condition levers (ECL), which influence engine control levers located on engine fuel control (suppl. fig. 9.2 point 22). Engine control levers may occupy any position, thus determining power setting idle to maximum;

- Twist-grip throttle control, made integral with pilot’s collective stick. It allows to move simultaneously both engines control levers within the range of 50° according fuel control scale plate without changing MR collective pitch;

- Collective stick, which changes MR collective pitch φ_{MR min} tо φ_{MR max} and moves simultaneously both engines control levers within the range of 70° according fuel control scale plate.

Position of engine control levers (22) causes readjustment of TC RPM governor, because each engine control lever position change changes available power of engines.

Range of possible TC RPM (and available power) with regard to engine control levers position for conditions Н=0, OAT_max=+15°C are shown at fig 9.3.

At idle power setting engine control lever rests on the stop, limiting idle power. In this case power produced by power plant is not enough to make MR rotate with 95% RPM, which is an operational RPM. Even if MR collective pitch is minimum (φ_{MR min}=1°) MR RPM is n_MR≤65%, and engine power setting is determined by БАРК electronic governor (see fig. 9.3, point 1).

If engine control levers are moved to bigger set angles (after throttle is moved to the right) TC RPM increase and as a result MR RPM increase as well. MR collective pitch remains minimum (φ_{MR min}).

If engine control levers position is α~48° TC RPM increase, thus increasing power, produced by helicopter power plant. This power is enough to make MR rotate with operational RPM, provided MR collective pitch is minimum φ_{MR min}. (see fig. 9.3, point 2). This moment onwards MR RPM is maintained the same n_MR=(95±2)% by MR RPM governors. These governors determine engine power setting.

If throttle is moved to full right position, both engines control levers are set to α=50° position. TC RPM governors are adjusted to maintain n_ТC=92%. This power is higher than the power transferred to MR, because MR collective pitch is minimum (see fig. 9.3, point 3).

Excess power is compensated by MR RPM governors (suppl. fig. 9.2, 28), so the actual TC RPM is lower than 92%.

Decrease of TC RPM below adjusted makes the governor valve close and in such a way TC RPM governor is disabled.

Left hand and right hand engine MR RPM governors adjustment cannot be perfectly matched. However free turbines of both engines rotate with identical RPM, determined be MR. That’s why governors influence on both engines differs. The governor, adjusted for lower power setting decreases fuel supply more, thus engines will operate at different power. Power synchronizer (33) was designed to compensate for this problem. It is essentially one of the fuel control governors. It gauges air pressure behind the compressor (Р_C) and changes fuel supply of the engine (tailing engine), which air pressure is lower to increase its power.

This causes slight increase of MR RPM and as a result TC RPM increases. All these changes cause leading engine (the engine with higher pressure Р_C) free turbine RPM increase. To maintain MR RPM stable leading engine governor decreases its power.

Указанный процесс изображен на рис. 9.4. Увеличению режима ведомого двигателя соответствует переход из точки 2 в точку А, изменению режима ведущего двигателя – переход из точки 1 в точку А.

Рис. 9.3. Зависимость параметров силовой установки от угла поворота РУД

nТК	– частота вращения ротора ТК
φ°НВ	– шаг НВ
	– работа регулятора nТК
	– работа регулятора nСТ
­	– работа регулятора nТК (контур турбокомпрессора ЭРД)

Таким образом, происходит встречный процесс выравнивания Р_К с помощью регулятора частоты вращения НВ ведущего двигателя и СМ ведомого двигателя.

Рис. 9.4. Смещение характеристики регулятора

синхронизатором мощности при совместной работе двух двигателей.

This process is represented at figure 9.4. The increase of trailing engine power is represented by interval between points 2 and A. The change of leading engine power is represented by interval between points 1 and A.

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