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Rob,
You are in a perfect position to test the following "theory":
First, the premises and observations - on initiating the gear down action:
1. The nose gear is driven out by gas "springs" at a fairly great speed and force.
2. The nose gear cylinder acts as a diaphragm pump - creating a low pressure on the "down" side and a high pressure on the up side thus momentarily requiring the movement of a large volume of fluid - more than the pump or lines can fully keep up with.
3. The heavy mains, falling at first from mere gravity, also contribute to the condition noted in 2 above.
4. The main gear doors (even if spring loaded for down as in 320/360s) have little weight and those actuators don't get pressure from the pump for several moments thus leading to a stall long enough to allow the wheels to hit and push the doors open.
If one detaches the gas springs from the nose gear, do the main doors beat the wheels on a gear down action?
What happens on the emergency gear drop?
Theory: Consider the effects of a flow restrictor on the nose gear hydro lines.
Observe the action on the gear up activity - On 320/360s, the following is observable:
1. Mains come up first because nose is held out by gasp spring. (sp err allowed to stand - pun intended)
2. Mains hit door hydro switch and doors begin to close.
3. Pressure builds and overcomes gas spring, nose starts to retract and pressure drops a bit.
4. Mains drop enough to close door hydro sw and the doors drop almost full open as system pressure assumes some "balanced" state while the pump is overcoming the Gasp spring.
5. Nose gear is tucked away, pressure builds and doors close after overcoming their own down spring force.
6. Pressure builds from about 600 psi (used for continous closing action) to 1100-1200 psi to crisply lock everything up and the pressure sw shuts off pump.
See if this is similar to your experience. BTW, half the scratches on my 320 nose gear door may be because the wheel was not quite straight as the nose was retracted, but the other half occurred as the wheel pushed the door out of the way as described in the first section above.
Scott Krueger
N92EX
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