REFLECTOR: Nose gear didn't lock

[Glenn Babcock]

Scott,

The purpose of the gas spring is to help push the gear over center when 
using the dump valve.  Opening the dump valve releases the pressure on the 
hydraulic cylinder and the gas spring will then be able to push the 
overcenter linkage to the limit.

But when the gear is operated by the pump the hydraulic cylinder is pushing 
the overcenter linkage and overpowers the gas spring easily.  So what you 
need to look at is the hydraulic system.  Perform a retract test and using 
the gear pump as usual lower the gear.  Try to reproduce the scenario where 
the gear switch is down, the pump has stopped but the nose gear light is not 
on.  Then check the position of the overcenter linkage and see if it is 
touching the stop inside the keel.

If not, you may have a bad pressure switch, a bad hydraulic cylinder, a 
blocked line, or some other issue causing the gear pump to stop before the 
cylinder reaches the end of its travel.  Try opening the dump valve and see 
if the linkage moves any further.

It's also possible it's just out of rig.  If so, you need to find out why. 
For instance, did the rod end jam nut come loose?

When the system works correctly the cylinder should extend to its limit with 
the overcenter linkage just touching the stop.  It should NOT press against 
the stop, the pressure must be carried by the cylinder.  The linkage should 
be ~1/4" past center.  The gear pump stops when the cylinder reaches it's 
limit and the pressure increases in the system, causing the pressure switch 
to open.

I had a similar issue and it was a bad pressure switch.  Once I replaced it 
the system was back to normal.

Regards,
Glenn
N697RG SERG (flying)
http://lakenormanairpark.org/

--------------------------------------------------
From: "Chuck Jensen" <cjensen at dts9000.com>
Sent: Thursday, October 08, 2009 8:17 AM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Nose gear didn't lock

> Scott,
>
> During the ground retract test, when you didn't get the green light, did 
> you check to see if the assembly was over-center?  If it was, then as 
> Terry suggests, your proximity switch may need to be adjusted.  But if you 
> use your stick and find that you have to nudge it a little to finally go 
> over center, then your light is good but you have a mechanical issue, be 
> it spring or whatever....that's waaaaaay above my pay grade.
>
> Chuck
>
>
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
> Behalf Of Scott Derrick
> Sent: Wednesday, October 07, 2009 9:42 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: REFLECTOR: Nose gear didn't lock
>
>
> On my last flight when I let the gear down I had a unsafe light and the
> nose gear light was not lit, the pump light indicated it had shut off, I
> gave a little jerk on the stick to increase the G force momentarily and
> the green light came on.
>
> later I was performing a gear retraction to test, when I let the gear
> down I got the same indication. I kicked the nose gear tire and the
> light came on.
>
> Is this a symptom of the nose gas strut going soft?
>
> I have previously in the last couple months made 20+ retraction tests
> with all OK.
>
> Scott
>
>
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html



>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.421 / Virus Database: 270.14.7/2422 - Release Date: 10/08/09 
> 06:39:00
>