FlyDubai incident 30/9

[AviatorInsight]

A 737 does not have a RAT - the backup is pulleys and cables for the control surfaces

The APU does not turn on automatically - it requires manual pilot input.
And I believe the standby electric hydraulic pumps require high current AC power which its small batteries cannot supply.

However there might have been residual hydraulic pressure in the system which may have assisted.

The hydraulics didn’t fail. There’s still fluid in the lines and reservoir. When the engine driven pumps stop running, the electric motor driven pumps kick in. These pumps are 6x weaker than the engine pumps. So things will take longer to do, flaps, gear, spoiler controls, (and to some extent) flight controls on the MAX, etc. The aircraft will still fly normally on the electric pumps.

This is not manual reversion. That is when a complete loss of both engine and electric hydraulic pumps lose power (usually through a loss of hydraulic fluid).

As you correctly stated, the 737 does not have a RAT because it can still be flown on battery power and manual reversion. Think of it like a loss of power steering in the car. Still controllable, just a lot harder.

 

[Quickstatus]

the electric motor driven pumps kick in.

But what provides power to the electric pump?
JB mentioned the windmilling engines and/or residual power in batteries?