EMERG FLT HYD Question

[Reflected]

When I start the engines and wait a bit too long before moving the throttle around the horn to idle, I hear the whine of the emergency flight hydraulic motor. Can anyone explain why that is so? Or is it a bug?

 

Thanks in advance!

Edited December 9, 2020 by Reflected

[sLYFa]

Interesting question. In auto mode, the backup flight control system will come online whenever both hydraulic systems drop below 2100psi. However, NATOPS does not mention any mechanism that prevents automatic BFCS engagement on ground with no hydraulic power (i.e. before engine start with ext power connected) but I'm sure there is one (WonW switch?). The way I believe it is modelled in DCS however is that once you exceed a certain pressure in either system (500 psi or something), the BFCS is armed and will start working from that point until you get above 2100psi pressure in either system. As there is probably some activation delay the BFCS might not engage at all if the engine spools up quickly.