Hi Pander216
The one of the reasons for this modification, is that you can now steer the nose wheel after a gravity (free fall) extension.
reason:
On the pre mod. system the steering servo is supplied from the landing gear door closing line (Green HYD)
On the post mod. system the steering servo is supplied from the Cargo door supply line. (Yellow HYD)
Doing a gravity extension the hydraulic supply is isolated and vented to prevent hydraulic locks, the gears and doors uplocks are released.
too Swedish Steve
nose wheel steering is only allowed if the following are met:
- Towing lever in normal position
- one engine in operation "master sw one" (pre mod)
- A/C speed lower then 130kts
- Main gear compressed