The darn GEAR, darn it!

[Pete Somers]

The main trouble is that these are more than likely original switches and they have springs on them an the springs loose there tension and cause you to have to put the switches a bit nearer to the operating arm so that they can work. Unless they were replaced they are 48 years old and have gone through a lot of abuse in there life with oil, grease, water and ice.
So if you have a problem with these switches it pays to have all the up and downlock switches replaced and rigged.
See what happens when you test fly it.

Regards
Pete

[billsheila]

By the way, how much did a "new" hyd pack cost?
ANSWER: $1500 plus $1000 core

Thanks for the clarification re the pressure, obviously me (and my mechanic!!) are not reading the manual carefully enough. But to save me some reading (manual is up at the shop anyway, so I can't reference it at this moment) and perhaps lots of mis-interpretation which I am prone to..a few more questions if you can be patient with me:

What tells the priority valve to move, and assuming it moves and does something other than load the mains while the handle is still up (ie pump is loaded) where does the pressure go? Does it just come off the mains and reside in the pack waiting until the door solenoid activates the door hydraulics? I believe the only electrical action going on with the pack (on these early models) is the door solenoid.

It seems to me all this stuff happens pretty quickly, so doors open, locks open, gear move up, switches make momentary contact, but then due to the rigging issue already noted move past and re-open (with the light coming on for this split second, this actuates the door solenoid allowing pressure into the door hydraulic circuit), with pressure, the doors close but as soon as they hit the airframe, a bit of pressure builds and slides the door valve to the other side saying "open" because of the solenoid dropped out when the switch was lost, therefore doors immediately reopen. Handle never moves to neutral because this is a function of steady pressure build up with closed doors, and the time delay valve, which we are never getting to in this sequence of events.

If the above description is mostly right, it explains most if not all of what has been observed in flight, with the exception of perhaps a few things or a few remaining questions:

If the main gear are not remaining loaded (ie just residual pressure on the system) why is it when the handle is manually moved to neutral (during an in-flight test) do I get a steady light, but not when the handle is in the up position? NOTE: with the mule or the hand pump on the ground, we do get steady up light (with handle up) once mains go into the locks. So one additionaly theory is that the engine driven pump is putting out more pressure than the mule or the hand pump, forcing mains up a bit further and we thus loose the switch. But this theory only holds if the pressure is somehow remaining on the mains, or perhaps it is just higher residual pressure? But again if it is just higher residual, why in flight do we get a light when the handle is returned to neutral.

The reason for our original confusion and question was to determine if we have some kind of fault in the pack internal hydraulics (which remember is only happening in flight with engine driven pump doing the work) or whether we can isolate the problem to switches and electrical.

Thanks very much for your patience and help with this persistent, frustrating, (and by now quite expensive) problem.

Bill

[Pete Somers]

Bill
The gear up cycle is---
1 Gear handle to the up position which takes the power off the door solenoid and the doors open.
2 HYD pressure is supplied to the downlocks and unlocks the gear and the gear downlock switches open (very important)
3 Gear swings and HYD pressure is supplied to the gear jacks and the gear is lifted into the bays.
4 Gear lifts into the bays and passed the uplocks and pressure takes the gear up to ensure it goes passed the uplocks, the uplock switches should be closed to put on the amber light and pressure should put the handle back to center which takes the HYD pressure off the gear and the it hangs on the uplocks and power off the door soleniod which closes the doors.

Weather you put the gear up or down, power has to be removed from the door solenoid to close the doors, so any open circuit in the uplock circuit will cause the doors to open after retraction, it will also happen with the gear down as any open circuit will cause the doors to open as power is removed from the door solenoid.

As for the handle going to center, if is works in flight on a down cycle but not on the up cycle the time delay valve and priority valve must be ok.

Maybe this power pack being OHC has a better flow through it and the valves operate a little bit better than your old unit, the better flow may mean a higher pressure at the gear actuators which raises the gear a bit faster into the uplocks causing the switch problem.

But I do think you should replace these switches as they will cause you the same problem later on.

Just my views.
Regards
Pete