737 Classic complete loss of power to Standby ADI
 

Re B737 Classics. With total electrical failure including flat battery, which means no power to the standby ADI, how long approximately does it take before the standby ADI becomes affected so badly that it gives no information. 30 seconds? One minute?

With a suction driven AH total failure of the suction pump means the gyro rapidly loses RPM. So you have about a minute remaining before the AH gyro topples. Does the same characteristic apply to an electrically powered AH as in the standby ADI in a 737 Classic.
Reason for the question was the Garuda 737 that lost all electical power following a double flameout following inadvertent penetration of a CB super cell over Indonesia. They broke clear of cloud but I wondered if with loss of electrics to the standby ADI while still in cloud they must have some usable info from the standby ADI otherwise control would have been lost immediately if the gyro toppled immediately with no electrical power?

That 737 had encountered severe thunderstorm activity during approach to its destination, suffered flameout in both engines, and ditched in a shallow river, resulting in one fatality and several injuries.

I got the OEM.....

Your post appears to have no relevance to the thread? JT

The basic requirement is that the electric standby has its own separate power supply to provide for fhe statutory operating time.

The sim implementation is a bit theatrical in that the device works fine for around 30 minutes whereupon all goes black and all present have a chuckle before we try again with far more effort directed to getting VMC or on the ground before blackness descends once more.

Once the backup power is exhausted it is a case of "all over, Red Rover" unless you are VMC or on the ground. Any function remaining is problematic and will depend on the system design.