X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 03 Feb 2014 09:40:58 -0500 Message-ID: X-Original-Return-Path: Received: from qmta03.westchester.pa.mail.comcast.net ([76.96.62.32] verified) by logan.com (CommuniGate Pro SMTP 6.0.8) with ESMTP id 6714693 for lml@lancaironline.net; Mon, 03 Feb 2014 07:55:23 -0500 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.32; envelope-from=jmorgan1023@comcast.net Received: from omta16.westchester.pa.mail.comcast.net ([76.96.62.88]) by qmta03.westchester.pa.mail.comcast.net with comcast id MoTa1n0011uE5Es53oup4G; Mon, 03 Feb 2014 12:54:49 +0000 Received: from [192.168.1.100] ([24.11.157.196]) by omta16.westchester.pa.mail.comcast.net with comcast id Mouo1n00E4EXR5U3couoSP; Mon, 03 Feb 2014 12:54:49 +0000 From: Jack Morgan Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: multipart/alternative; boundary="Apple-Mail=_739B0265-090E-4C06-97C7-F1CDEE3696B1" Subject: IV Mains won't retract X-Original-Date: Mon, 3 Feb 2014 07:54:47 -0500 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <05D9DCD3-3FDE-40A2-B2C4-E5C1A277F507@comcast.net> X-Mailer: Apple Mail (2.1283) --Apple-Mail=_739B0265-090E-4C06-97C7-F1CDEE3696B1 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Hi Fred, Haven't seen this one before so can't help much=85=85.. I would consider = looking elsewhere than the main cylinders since both have the problem = together. The odds of both cylinders wearing out together are pretty = long. My guess is an item somewhere is preventing both of them from = getting full hydraulic pressure or allowing free fluid return from both = of them. The nose gear will extend/retract with less pressure while the = mains require more. More pressure is required to unlock the main gear = pins than to retract the nose gear. Is the pressure switch allowing normal pressure? Is the retract valve delivering full pressure or leaking internally? Is the shuttle valve allowing free flow of fluid from the main cylinders = back to the retract valve? (assumes a manual emergency hand pump) Is the retract valve allowing free fluid flow back to the hydraulic pump = return line? A really blind guess is to rebuild the retract valve before turning to = the main cylinders. Hope this gives some clues. Jack Morgan On Feb 3, 2014, at 6:00 AM, Lancair Mailing List wrote: > Lancair Mailing List Digest #4509 >=20 > 1) Lancair IV main landing gear problems > by "frederickemoreno@gmail.com" >=20 > This digest is sent to you because you are subscribed to > the mailing list . > For archives and help click = http://mail.lancaironline.net:81/Lists/lml/List.html > LML website: http://www.lancaironline.net/maillist.html >=20 > From: "frederickemoreno@gmail.com" > Subject: Lancair IV main landing gear problems > Date: February 2, 2014 12:34:09 PM EST > To: lml@lancaironline.net >=20 >=20 > Been scratching my head on this one, a mechanical intermittent problem = that happens occasionally, and happened again this morning. Main = landing gear will not retract. Nose gear goes up, not mains. Recycle = gear, everything retracts like a thing of beauty. Months go by, no = problem, then it happens again. > =20 > Twice we have jacked the airplane up, carefully adjusted the rack and = pinion clearance and cylinder stroke positioning relative to the rack = gear and the plastic down stop, and yesterday it happened on take off. = Grrrrr. Slow flight, 110 knots, cycle down, up, down, up, no problem. = Back to airport for total of 5 landings, no problem. =20 > =20 > This morning filled the cabin with pork, took off for a fly in = breakfast, no problem with gear retraction, landed there with heavy = braking to get off the runway fast with an airplane behind us on short = final, enjoy breakfast, depart a couple of hours later, mains would not = come up. Grrrr. Recycle, no problem, slick as custard in July. =20 > =20 > I have been working this problem with a fellow engineer with much = experience in hydraulics . Current theory: Down lock pistons and pins = constitute assemblies in the hydraulic cylinders that may get jammed in = position after years of wear (estimate about a thousand landing cycles) = and application of larger than normal side loads on the locking pins = from, for example, heavy breaking. Piston/pin assembly jams due to side = load and wear, select gear up, piston does not rise due to jam, no = hydraulic fluid can thus pass to the main gear cylinder. Cycle the = gear, changing forces on the main gear pistons clears the jam with some = wiggles and bangs as you recycle the gear, raise gear, no problem. > =20 > Right now our plan is to order O-rings (requested o-ring kit or list = of part numbers for main gear from Lancair), pull the cylinders and rack = as an assembly out of the airplane, disassemble, inspect, look for = scores, side load wear or whatever we can see. We will deal with = whatever we find. While out in the boondocks of Western Australia, the = area is agricultural with the regional center town nearby having a = surprisingly large number of hydraulics and machine shops due to all the = ag machinery within a 200 mile radius. So we can probably get parts = made, bore cylinders, machine inserts, or whatever.=20 > =20 > But all this assumes we have diagnosed the problem correctly. > =20 > We know you encounter problems waiting to raise gear due to air loads = as the airplane accelerates. That is NOT the problem as it has occurred = even raising the gear handle at 20 feet/95 knots shortly after rotation. = =20 > =20 > Any insights, history, observations, advice or theories would be most = welcome.=20 > =20 > Head Scratching Fred Moreno, going bald > >=20 >=20 --Apple-Mail=_739B0265-090E-4C06-97C7-F1CDEE3696B1 Content-Type: multipart/related; type="text/html"; boundary="Apple-Mail=_48113371-764F-4CE4-9A72-A227CAA87DB7" --Apple-Mail=_48113371-764F-4CE4-9A72-A227CAA87DB7 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Hi = Fred,

Haven't seen this one before so can't help = much=85=85.. I would consider looking elsewhere than the main cylinders = since both have the problem together. The odds of both cylinders wearing = out together are pretty long. My guess is an item somewhere is = preventing both of them from getting full hydraulic pressure or allowing = free fluid return from both of them. The nose gear will extend/retract = with less pressure while the mains require more. More pressure is = required to unlock the main gear pins than to retract the nose = gear.

Is the pressure switch allowing normal = pressure?

Is the retract valve delivering full = pressure or leaking internally?

Is the shuttle = valve allowing free flow of fluid from the main cylinders back to the = retract valve? (assumes a manual emergency hand = pump)

Is the retract valve allowing free fluid = flow back to the hydraulic pump return line?

A = really blind guess is to rebuild the retract valve before turning to the = main cylinders.

Hope this gives some = clues.

Jack Morgan

On = Feb 3, 2014, at 6:00 AM, Lancair Mailing List wrote:

=        Lancair Mailing List Digest = #4509

1) Lancair IV main landing gear problems
=    by "frederickemoreno@gmail.com"= <frederickemoreno@gmail.com&= gt;

This digest is sent to you because you are subscribed to
=  the mailing list <lml@lancaironline.net>.
Fo= r archives and help click http://mail.= lancaironline.net:81/Lists/lml/List.html
LML website: http://www.lancaironli= ne.net/maillist.html

Subject: Lancair IV main landing gear = problems
Date: February 2, 2014 12:34:09 PM EST


Been scratching my head on this one, a mechanical intermittent = problem that happens occasionally, and happened again this = morning.  Main landing gear will not retract.  Nose gear goes = up, not mains.  Recycle gear, everything retracts like a thing of = beauty.  Months go by, no problem, then it happens again.
 
Twice we have jacked the airplane up, carefully adjusted the rack = and pinion clearance and cylinder stroke positioning relative to the = rack gear and the plastic down stop, and yesterday it happened on take = off.  Grrrrr.  Slow flight, 110 knots, cycle down, up, down, = up, no problem.  Back to airport for total of 5 landings, no = problem.  
 
This morning filled the cabin with pork, took off for a fly in = breakfast, no problem with gear retraction, landed there with heavy = braking to get off the runway fast with an airplane behind us on short = final, enjoy breakfast, depart a couple of hours later, mains would not = come up.  Grrrr.  Recycle, no problem, slick as custard in = July.  
 
I have been working this problem with a fellow engineer with much = experience in hydraulics . Current theory: Down lock pistons and pins = constitute assemblies in the hydraulic cylinders that may get jammed in = position after years of wear (estimate about a thousand landing cycles) = and application of larger than normal side loads on the locking = pins from, for example, heavy breaking.  Piston/pin assembly = jams due to side load and wear, select gear up, piston does not rise due = to jam, no hydraulic fluid can thus pass to the main gear = cylinder.  Cycle the gear, changing forces on the main gear pistons = clears the jam with some wiggles and bangs as you recycle the gear, = raise gear, no problem.
 
Right now our plan is to order O-rings (requested o-ring kit or = list of part numbers for main gear from Lancair), pull the cylinders and = rack as an assembly out of the airplane, disassemble, inspect, look for = scores, side load wear or whatever we can see.  We will deal with = whatever we find.  While out in the boondocks of Western  = Australia, the area is agricultural with the regional center town nearby = having a surprisingly large number of hydraulics and machine shops due = to all the ag machinery within a 200 mile radius.  So we can = probably get parts made, bore cylinders, machine inserts, or = whatever. 
 
But all this assumes we have diagnosed the problem correctly. =
 
We know you encounter problems waiting to raise gear due to air = loads as the airplane accelerates.  That is NOT the problem as it = has occurred even raising the gear handle at 20 feet/95 knots shortly = after rotation.  
 
Any insights, history, observations, advice or theories would be = most welcome. 
 
Head Scratching Fred Moreno, going bald
 <image.gif>



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