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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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 Posted: Sun Sep 10, 2017 1:31 am Post subject: CJ gear comes down nose first, then mains |
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Hi all, looking for a plausible explanation:
We recently replaced MLG uplocks, MLG uplock actuators, lines, shuttle valve (on uplocks), hoses and solid air lines of the MLG. Also one new actuator, the other two were new in the last few years. The NLG uplock actuator is off a 2003 built CJ. The shuttle valves on NLG and MLG actuators are old but seemingly serviceable.
After conducting flight with gear handle in UP position, selecting DOWN has the nose gear releasing first, followed by the mains (more or less together). I'd have to double check but I think the nose gear is locked before the others start - I think the book specifies 2 second delay as ok with this sequence, this would be close but I'd love to know why.
Strange behaviour. This aircraft has always been like this, I guess all this new stuff eliminates a few things, but any ideas on what it could be?
** If flight is conducted with gear handle NEUTRAL, then for gear extension it is selected UP 1-2-3 then DOWN, they all come out perfectly together. This is not how we normally operate, but it may have some bearing on it?***
Our next move is to use Doug's shuttle valve referb kits on the older shuttle valves. Any other thoughts?
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dsavarese0812(at)bellsout
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| Posted: Sun Sep 10, 2017 8:42 am Post subject: CJ gear comes down nose first, then mains |
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Are the restrictors in the pneumatic lines going to the main and nose gear actuators? On the CJ, they're suppose to be on both the up and down side of the actuator.
Dennis
From: JL2A <info(at)flyingwarbirds.com.au>
To: yak-list(at)matronics.com
Sent: Sunday, September 10, 2017 5:32 AM
Subject: CJ gear comes down nose first, then mains
--> Yak-List message posted by: "JL2A" <info(at)flyingwarbirds.com.au (info(at)flyingwarbirds.com.au)>
Hi all, looking for a plausible explanation:
We recently replaced MLG uplocks, MLG uplock actuators, lines, shuttle valve (on uplocks), hoses and solid air lines of the MLG. Also one new actuator, the other two were new in the last few years. The NLG uplock actuator is off a 2003 built CJ. The shuttle valves on NLG and MLG actuators are old but seemingly serviceable.
After conducting flight with gear handle in UP position, selecting DOWN has the nose gear releasing first, followed by the mains (more or less together). I'd have to double check but I think the nose gear is locked before the others start - I think the book specifies 2 second delay as ok with this sequence, this would be close but I'd love to know why.
Strange behaviour. This aircraft has always been like this, I guess all this new stuff eliminates a few things, but any ideas on what it could be?
** If flight is conducted with gear handle NEUTRAL, then for gear extension it is selected UP 1-2-3 then DOWN, they all come out perfectly together. This is not how we normally operate, but it may have some bearing on it?***
Our next move is to use Doug's shuttle valve referb kits on the older shuttle valves. Any other thoughts?
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wlannon(at)shaw.ca
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| Posted: Sun Sep 10, 2017 9:27 am Post subject: CJ gear comes down nose first, then mains |
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Check for presence and size of restrictors ref. pg. 105/106 of Tech. Specs.
Walt
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dougsappllc(at)gmail.com
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| Posted: Sun Sep 10, 2017 6:09 pm Post subject: CJ gear comes down nose first, then mains |
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Go look where you worked on the parts you mention, gotta be there, looks like a little cap, fits on the nipple under the B nut  In the IPB the are called "dampers". You can in fact cause the gear to cone up in any order you wish, by altering the size on hole in these restrictors.
I have them in stock if you have already cleaned the bench and swept the floor. They are tiny little buggers, easy to miss.
Doug
On Sun, Sep 10, 2017 at 10:26 AM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
Check for presence and size of restrictors ref. pg. 105/106 of Tech. Specs.
Walt
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Mon Sep 11, 2017 2:16 am Post subject: Re: CJ gear comes down nose first, then mains |
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thanks all.
I'm not convinced it is simply restrictors - but happy to go with the simplest answer!
My doubts come from:
A) Did not see any. The entire MLG air lines from rear cockpit outwards was replaced. Many small items were dropped (those tiny CJ spring washers!) but all found. Eventually. No restrictors though. The one restrictor found on this aircraft is in flap system. I will double check if they've been left pressed-on to the old air lines though.
B) It is not immediately clear to me why it swings its legs out of bed in strange sequence when flown with gear handle in up, compared to perfect extension when using the (non-normal) NEUTRAL - UP 2 3 4 - DOWN method.
It seems like it is more related to how LONG the pressure resides in the UP system.
Testing reveals that if you try NEUTRAL - UP 2 3 4 5 6 ... 10 - DOWN it starts to go out of sequence ('sequence' meaning all three red lights going out together and red lights coming on together).
It only takes a few seconds to fully pressurise the UP side. The longer the handle is left in UP, the more reluctant the MLGs are to come down at same time as NLG.
Leak?
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