LNC 2 hydraulics

Submitted by Anonymous on

Forums: 

From: Ian B. Crowe <ian.crowe [at] sympatico.ca>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: LNC 2 hydraulics
Date: Sun, 27 Oct 2002 18:31:48 -0500
To: <lml>

I have recently tested my hydraulic system for the gear.  I have installed

two pressure guages on the high and low pressure circuits.I have the new

emergency extension cock, there are no visible external leaks and the

problem is very intermittent.



The gear extends and retracts in 8 to 10 seconds.  On retraction the mains

lead the nose to the extent that the mains are in the well before the nose

starts to retract.



The pressure gauges show only a small increase in pressure on retraction

until the gear is fully up when the pressure rises and the pump shuts down.

The same applies on the extension cycle when the gear is fully down and

locked the low pressure rises to 700 psi and the pump shuts down.  In other

words the system takes very little force to operate until the cylinders

reach their stops.



It is on the extension cycle that a very intermittent problem has surfaced.

The gear goes down and locks.  The pressure builds up to 700 psig and the

pump shuts down.  The low pressure starts to bleed off and it is possible to

see the high pressure gauge move off its zero position as the low pressure

drops..  The pump cuts in restores the pressure, shuts off and the cycle

begins again.



If the gear is retracted and again extended the problem disappears.  It

appears as if the low pressure is leaking across to the high pressure side

but not every time.  If you leave the system off overnight in the morning

there will often be 400 to 500psig left in the circuit.



So what is happening?  The gauges suggest that the low pressure is migrating

to the high pressure side either across the emergency extension cock or

across the piston of one or more of the double acting cylinders.  But why

not all the time?  Could it be air in the system?  How do you trouble shoot

an intermittent fault ?  In theory I should be able to blank off the LP

pressure to the cylinders until the fault disappears but I may not get the

fault to reappear on command!  Perhaps I should start  with the cock.

Another probability is that I have a bubble of air somewhere.



Any ideas anyone?



Ian Crowe

LNC 2 hydraulics

Submitted by Anonymous on

From: <Sky2high [at] aol.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] LNC 2 hydraulics
Date: Sun, 27 Oct 2002 20:40:58 -0500
To: <lml>
Message Header


Undecoded Message

Ian,



Great observations.  I have seen the same myself. 



Try these items:



1. For air bubbles, whilst on jacks, open the dump switch and run the pump for a while to circulate fluid.  Then close the valve, activate the up circuit and release the dump valve again.  Repeat several times.  This should clear any bubbles.



2. The pump itself has a shuttle valve and pressure relief valves.  If you are confident that the actuator piston o-rings and cylinders walls are "perfect" and the dump valve is sealing, perhaps the pump has a problem with leak-back.



3. The door valves are actually check-valves (biased to keep the doors open) that are defeated when the gear is up tight.  Could these be leaking? 



4. Is there any dirt in the system?  The pump has filters on the reservoir draw tubes for both up and down but not all the fluid passes thru the system.  For example, if you have rebuilt a cylinder, you have noted that the cylinder ends contain blackened fluid, discolored by the deterioration of the o-rings and never passed thru the system except locally.  If dirt has gotten in the system, it is possible to reside locally in a cylinder and slowly damage the piston seal.



Good luck!



Scott Krueger

N92EX

LNC 2 hydraulics

Submitted by Anonymous on

From: <edechazal [at] comcast.net>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: LNC 2 hydraulics
Date: Mon, 28 Oct 2002 19:13:41 -0500
To: <lml>
Message Header


Undecoded Message

Hi Ian,



I've got pressure gages on my panel and have seen the same thing regarding

pressure bleed.  I overhauled the cylinders and discovered that several tubes

had scored walls, allowing fluid to seep by.   I got new tubes from the

manufacturer ($50 instead of $150 for all new assemblies) and the problem is

greatly improved.  My theory as to why this is worse in the gear extended

situation is that this is where the gear spends most its time and hence bits

of debris in the system collects at this point in the nose gear.   Repeated

cycling of the gear with debris inside the hydraulics causes scrapes.  Check

your nose gear first.



This is important because what happens in summer is that the fluid leaks

across into the low pressure side, the pump for some reason does not allow

this pressure to vent to the reservoir.  Then, while you taxi to the active,

the system heats up causing pressure in both circuits to rise together.  If

this pressure rises to 800 psi, the switches will not allow you to raise the

landing gear and actuating the dump valve will have no effect.  You will be

stuck until you land and crack the system to let pressure out.  I know because

it has happened to me several times until I started pulling the breaker on the

ground.  With overhauled cylinders, it's no longer a threat.



Good Luck,

Ed de Chazal

LNC 2 hydraulics

Submitted by Anonymous on

From: Larry Henney <LHenney [at] dellepro.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: RE: [LML] Re: LNC 2 hydraulics
Date: Tue, 29 Oct 2002 00:46:41 -0500
To: <lml>
Message Header


Undecoded Message

Ed Writes:



>This is important because what happens in summer is that the fluid

leaks across into the low pressure side, the pump for some reason does

not allow this pressure to vent to the reservoir.  Then, while you taxi

to the active, the system heats up causing pressure in both circuits to

rise together.  If this pressure rises to 800 psi, the switches will not

allow you to raise the landing gear and actuating the dump valve will

have no effect.  You will be stuck until you land and crack the system

to let pressure out.  I know because it has happened to me several times

until I started pulling the breaker on the ground.  With overhauled

cylinders, it's no longer a threat.



Thanks Ed.  That was an absolute Gold Nugget of clarification.  I had

this happen a couple times and wasn't sure why / how I had "fixed" the

lockup.



Larry Henney

N360LH LNC2 IO-360 B1

16XS  Ft Worth, TX

LNC 2 hydraulics

Submitted by Anonymous on

From: Ian B. Crowe <ian.crowe [at] sympatico.ca>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Fw: LNC 2 hydraulics
Date: Sun, 03 Nov 2002 21:44:48 -0500
To: <lml>
Message Header


Undecoded Message

This is the reply I received from Mark at Lancair.  It may help others with

hydraulic problems.



For the moment my system is partially leaking off the down pressure over the

weekend with the pump off.  The residual pressure is 250 psi when I get in

on Monday morning.  The pump shuts off at 700psi.  If that is the worst I

get I am not too worried.



I hope to have the final inspection finished next week and who knows I may

be airborne shortly thereafter.



Ian Crowe.

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

From: "Mark Mahnke" <Markm [at] lancair-kits.com>

To: <ian.crowe [at] sympatico.ca>

Sent: Thursday, October 31, 2002 1:17 PM

Subject: Re: LNC 2 hydraulics





> Ian -- You have a good understanding of the system and that really

> helps.  Unfortunately,  The next step is to isolate the potential leak

> points.  I usually start by capping off the lines that go to the dump

> and the nose gear then test.....etc...  It may not be worth chasing the

> by-pass if it takes a long while to recycle.  If it only happens in the

> down position and not the up it is not important to eliminate a by-pass.

>  Even every few minutes is not a problem.  I would try to correct it if

> the recycle occurs more than every half hour on the up side.  Have a

> good week.

>

>

>

> Mark Mahnke

> Lancair Technical Support

> 541.923.2244

> markm [at] lancair-kits.com

>

> >>> "Ian B. Crowe" <ian.crowe [at] sympatico.ca> 10/27/02 02:04PM >>>

> I have recently tested my hydraulic system for the gear.  I have

> installed

> two pressure guages on the high and low pressure circuits.I have the

> new

> emergency extension cock, there are no visible external leaks and the

> problem is very intermittent.

>

> The gear extends and retracts in 8 to 10 seconds.  On retraction the

> mains

> lead the nose to the extent that the mains are in the well before the

> nose

> starts to retract.

>

> The pressure gauges show only a small increase in pressure on

> retraction

> until the gear is fully up when the pressure rises and the pump shuts

> down.

> The same applies on the extension cycle when the gear is fully down

> and

> locked the low pressure rises to 700 psi and the pump shuts down.  In

> other

> words the system takes very little force to operate until the

> cylinders

> reach their stops.

>

> It is on the extension cycle that a very intermittent problem has

> surfaced.

> The gear goes down and locks.  The pressure builds up to 700 psig and

> the

> pump shuts down.  The low pressure starts to bleed off and it is

> possible to

> see the high pressure gauge move off its zero position as the low

> pressure

> drops..  The pump cuts in restores the pressure, shuts off and the

> cycle

> begins again.

>

> If the gear is retracted and again extended the problem disappears.

> It

> appears as if the low pressure is leaking across to the high pressure

> side

> but not every time.  If you leave the system off overnight in the

> morning

> there will often be 400 to 500psig left in the circuit.

>

> So what is happening?  The gauges suggest that the low pressure is

> migrating

> to the high pressure side either across the emergency extension cock

> or

> across the piston of one or more of the double acting cylinders.  But

> why

> not all the time?  Could it be air in the system?  How do you trouble

> shoot

> an intermittent fault ?  In theory I should be able to blank off the

> LP

> pressure to the cylinders until the fault disappears but I may not get

> the

> fault to reappear on command!  Perhaps I should start  with the cock.

> Another probability is that I have a bubble of air somewhere.

>

> Any ideas anyone?

>

> Ian Crowe

>

>

>

LNC 2 hydraulics

Submitted by Anonymous on

From: Bob <rbelshe [at] attbi.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: [LML] Re: LNC 2 hydraulics
Date: Thu, 07 Nov 2002 19:27:50 -0500
To: <lml>
Message Header


Undecoded Message

I recently went through the same problem,  with the pump "blipping"

about every 4-5 seconds.  In my case it only happened when the gear was

down.



The problem was the dump valve.  In my installation it was very easy to

test by remove the dump valve and closing off the lines with some spare

fittings.  This cured the "blipping".  Lancair sells a valve rated at

higher pressure, but it is slightly larger and a lot heavier.  I chose

to replace mine with the same valve, figuring I can replace it again in

8 years if need be.



Bob Belshe

Moraga, CA

Lancair 235/320  494 hrs.

LNC 2 Hydraulics

Submitted by Anonymous on

From: Ian B. Crowe <ian.crowe [at] sympatico.ca>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: LNC 2 Hydraulics
Date: Tue, 01 Mar 2005 07:52:14 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message
My a/c has been in the hangar for at least two
weeks whilst we worked on an oil cooler problem.
 
When we closed it up and were doing the preflight I
noticed the "Down" pressure gauge was showing zero but the pump refused to
run.  On closer inspection I realised the needle was pegged against the
stop and was registering 1000psi ++
 
I opened the emergency gear extension cock a hair,
bled the pressure down to 400psi and the pump kicked in and brought it back to
550psi.  Pressure switch works ok obviously.  The hangar is heated to
about 55F.
 
We flew the a/c and the gear worked well, no
problem.  Where this pressure comes from beats me as with the gear down the
HP side of the system is at zero and the gear select is in the down
position.  The safety switch I have will not allow the pump to run to
retract the gear.
 
Curiouser and curiouser to quote Alice in
Wonderland.
 
Ian Crowe.

LNC 2 Hydraulics

Submitted by Anonymous on

From: <Sky2high [at] aol.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] LNC 2 Hydraulics
Date: Tue, 01 Mar 2005 10:10:57 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message

In a message dated 3/1/2005 6:52:40 A.M. Central Standard Time,
ian.crowe [at] sympatico.ca writes:

My a/c has been in the hangar for at least two
weeks whilst we worked on an oil cooler problem.
 
When we closed it up and were doing the preflight
I noticed the "Down" pressure gauge was showing zero but the pump refused to
run.  On closer inspection I realised the needle was pegged against the
stop and was registering 1000psi ++
 
I opened the emergency gear extension cock a
hair, bled the pressure down to 400psi and the pump kicked in and brought it
back to 550psi.  Pressure switch works ok obviously.  The hangar is
heated to about 55F.
 
We flew the a/c and the gear worked well, no
problem.  Where this pressure comes from beats me as with the gear down
the HP side of the system is at zero and the gear select is in the down
position.  The safety switch I have will not allow the pump to run to
retract the gear.
 
Curiouser and curiouser to quote Alice in
Wonderland.

Ian,
 
Let's see, 'twas a full moon recently - high sun spot activity also -
Hmmmmmm........
 
Consider this:  Say that the system is leak free, The nose wheel well
is well sealed from the entry of any engine heat, the gear is extended and
locked during approach after a nice cold flight on a cold day
and there is no slop in the linkages (hi pressure is maintained against the
overcenter links rather than the cylinder stops).  The plane is then moved
into a heated hangar.  Now, let's suppose that the fiberglass
structures, hydraulic lines (both hard and flexible), cylinders and fluid all
expand in self-compensating ways such that they don't contribute much to any
change in pressure.  Finally, how much did the three steel
actuator rods expand in their temperature rise?  Was it
enough to push back on the actuator pistons to raise the pressure?
 
This is why I suggest the down stop be set first with the
actuators unattached to the linkages and the system pressurized - then each
securing bolt is snugly fit thru the linkage and rod end.  No slop, but
enough "play" to accept some pressure variance without putting unintended
consequential force on the linkages and attach points.  Of course, then the
up-stops have to be adjusted.
 
Electro-hydraulic systems were designed by the Mad Hatter - We just missed
the party where their operation was described by the Queen of Hearts. 
Curious indeed!
 
Scott Krueger
AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

Fair
and Balanced Opinions at No Charge!
Metaphysical Monologues taken at your own
Risk.

LNC 2 Hydraulics

Submitted by Anonymous on

From: <Tubamanflies [at] aol.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] Re: LNC 2 Hydraulics
Date: Tue, 01 Mar 2005 12:13:16 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message

OFF WITH THERE HEADS

LNC 2 Hydraulics

Submitted by Anonymous on

From: Christopher Zavatson <Christopher.Zavatson [at] udlp.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] LNC 2 Hydraulics
Date: Tue, 01 Mar 2005 13:12:01 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message

Ian,

<<On closer inspection I realised the needle was pegged against the

stop and was registering 1000psi ++>>

Sounds like a classic case of thermal expansion of the hydraulic fluid

and a leak free hydraulic system.

Chris Zavatson

LNC 2 Hydraulics

Submitted by Anonymous on

From: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] LNC 2 Hydraulics
Date: Wed, 02 Mar 2005 14:01:58 -0500
To: <lml>
Message Header


Undecoded Message

Posted for "Randy Snarr" <randy [at] telamerica.com>:



 Scott,

 You bring up an interesting point in how your gear is adjusted. My system is

 adjusted as per the factory

 with the gear against the aluminum sleeve stops on the up side and the down

 side is stopped by the over center links.

 The over center links are not that beefy and there is an enormous amount of

 stress on them with the down pressure at maximum.

 

 I wonder if there has ever been a failure due to this stress.

 Your solution sounds reasonable to me.

 

 I am curious as to what other have done if anything regarding the down side

 adjustment.

 

 Whilst writing this post I called Ross at Lancair and he told me essentially

 the same thing in that the over center link was not designed to handle the

 total down side stress of the system but admitted that there are many

 airplanes flying that are set up that way.

 He recommended the same solution as Scott, and that is to have the hyd cyl

 bottom out about the same time as the over center

 link hits it's limit taking a significant amount of the stress off the over

 center link...

 

 Randy L. Snarr

 235/320

 92% threatening 93% any day now...

 

 

LNC 2 Hydraulics

Submitted by Anonymous on

From: Earl Schroeder <earleschroeder [at] yahoo.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] Re: LNC 2 Hydraulics
Date: Wed, 02 Mar 2005 15:31:22 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message

Hi Randy,

It has been awhile but I believe that my construction manual (1988 model) did mention that the hyd cyl all needed to be bottomed out without any stress on the links.. maybe it was one of the supplements that came along while I was building my 235/320.  I know that I did adjust mine to that recommendation and it took a couple of attempts to get it just right.  Earl


...  I am curious as to what other have done if anything regarding the down side

 adjustment.

 

 Whilst writing this post I called Ross at Lancair and he told me essentially ....









--

No virus found in this outgoing message.

Checked by AVG Anti-Virus.

Version: 7.0.300 / Virus Database: 266.5.5 - Release Date: 3/1/2005

LNC 2 Hydraulics

Submitted by Anonymous on

From: Art Jensen <flycassutts [at] yahoo.com>
Sender: Marvin Kaye <marv [at] lancaironline.net>
Subject: Re: [LML] Re: LNC 2 Hydraulics
Date: Fri, 04 Mar 2005 11:08:38 -0500
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message



>   He recommended the same solution as Scott, and

> that is to have the hyd cyl

>   bottom out about the same time as the over center

>   link hits it's limit taking a significant amount

> of the stress off the over

>   center link...

>  

>   Randy L. Snarr

>   235/320

>   92% threatening 93% any day now...





Randy,



With this information you aquired, how do you adjust

to about the same time as the over center link hits

it's limit?



Art









__________________________________

Celebrate Yahoo!'s 10th Birthday!

Yahoo! Netrospective: 100 Moments of the Web

http://birthday.yahoo.com/netrospective/

LNC 2 Hydraulics

Submitted by Anonymous on

From: Per Kristensen <phk2299 [at] gmail.com>
Sender: <marv [at] lancaironline.net>
Subject: LNC 2 Hydraulics
Date: Fri, 18 Jul 2014 07:56:05 -0400
To: <lml [at] lancaironline.net>
Message Header


Undecoded Message

I’m looking for part no. ref. reparation kit to main gear cylinder, dumpvalve etc.

 

Regards  

FB… OY-JCP

 

Per H. Kristensen 

phk2299 [at] gmail.com