REFLECTOR: Nose gear didn't lock

Scott Derrick scott at tnstaafl.net
Fri Oct 9 08:07:53 CDT 2009


Bob,

I will get a close eyeball on that area. I have not adjusted the
microswitch yet.  have to remove the elevator push-pull tube  and a few
other items to get that far into the keel.  When I do I will verify all
is in place, not loose and not bent.

thanks,

Scott

Bob Jackson wrote:
> Scott,
>
> I would recommend that you keep a real close eye on that micro switch
> bracket and adjustment.  The microswitch bracket is supposed to limit the
> overcenter travel of the nose gear linkage.  But a hard landing can bend the
> bracket up or push the keel attachment bolts up if the holes are a little
> sloppy.  Are you sure the bracket hasn't been bent a little, or pushed up a
> little in the bolt holes causing the microswitch lever arm to need the
> adjustment?
>
> Bob Jackson
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Scott Derrick
> Sent: Thursday, October 08, 2009 5:07 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Nose gear didn't lock
>
> I checked today and it was the micro switch lever arm.  It needed to be
> bent just a tad more to cause the switch to indicate a down and locked
> position. 
>
> Scott
>
> Glenn Babcock wrote:
>   
>> 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
>>>
>>>
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