Terrence,

 

The new information does not change my analysis.  The following would be added to it:

 

If the dump valve is closed (no cross connection between the up-side and the down-side), then any attempt to hand raise the nose would mean that pressure would be placed on the down-side since there is no place for that fluid to go - Indeed, the down-side pressure would be increased on the main gear actuators rather than decreased.  Any fluid needed to fill the up-side would come thru the pump and reservoir since that is the only possible source - assuming everything is as designed.

 

Once you open the dump valve, I stand by my analysis.

 

If you think that your action while the dump valve was closed (pushing on the nose over center link) caused the main over center links to come unlocked, you have a serious problem with your hydraulic system and the springs that hold the main gear over center links in place.

 

Scott Krueger

 

Typo one-=line correction to my last on the gar... line 5... correction underlined.

----- Original Message -----

From: terrence o'neill

To: lml@lancaironline.net

Sent: Thursday, April 30, 2009 18:55

Subject: [LML] LNC2 gear

Here's an interesting quirk of the retract system, I think....

Yesterday, spurred by a helpful LML suggestion to increase the preload in my nose strut, I chocked the mains, weighted the tail, and supported the nose with the nosewheel an inch off the ground, in order to rotate the nosegear up a little in order to get an air chuck on the schroeder valve less than an inch behnd #3 exhaust tube.

So I pushed up the over- -center brace and pushed back the strut which moved back a little... which reisted .... still locked up. So I opened the free-fall valve. Pushed back the nose strut, chucked my new $22. / 300 psi made-in-china strut pump, on, and put in the max. 

Then lowered the nosewheel to over-center lock, lowered the nose, removed the weight on the tail, and observed 3 inches of strut!

So I pulled the plane out to run an engine idle check, and glanced at the right wing, was shocked to see the gear leaning inward about 10 degrees. !

 

I managed to get the jack in place and raise the wing enough to push the gear in place and pull the over-center strut to lock.

Checked the left gear... and found its over-center strut pushed up, unlocked,  too!

Jacked and pulled it down, and then put the plane back in the hangar and ran a retract-extend check -- after putting the free-fall valve back in closed position.

My guess is that with the hydraulic system closed/normal, in pushing the nosegear over-center lock up and pushing back on the nosewheel I also hydraulic-pressured the main cylinders to pull their over-center locks up.

 

So, if this is true, then here's a scenario to consider:

Gear down, no nose green light.

System pump or solenoid CB pops. 

SO, pull the pump CB, gear switch in Down, valve to free-fall.

Still can't get a nose green light. Just the mains.

 

To land, should the free-fall valve be left open,  or moved to closed? 

 

If it is moved to closed, and the nosegear is not locked over-center... will aft pressure on touchdown unlock the mains too, damaging not only the prop/engine but also the gear and fuselage?

 

Terrence

L235/320 N211AL

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