X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 03 Feb 2014 07:38:18 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 6.0.8) with ESMTP id 6714103 for lml@lancaironline.net; Sun, 02 Feb 2014 15:43:56 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=douglasbrunner@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=mz+M0pETY2nrqRX8FIZf/mLDU3XCZ1E5Z7r6XKyvCIdD1xi0D0d0kZAswGwMuVPj; h=Received:From:To:References:In-Reply-To:Subject:Date:Message-ID:MIME-Version:Content-Type:X-Mailer:Thread-Index:Content-Language:X-ELNK-Trace:X-Originating-IP; Received: from [98.204.78.83] (helo=DougsVAIO) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1WA3sv-0004C3-La for lml@lancaironline.net; Sun, 02 Feb 2014 15:43:22 -0500 From: "Douglas Brunner" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Lancair IV main landing gear problems X-Original-Date: Sun, 2 Feb 2014 15:43:20 -0500 X-Original-Message-ID: <000001cf2057$693888b0$3ba99a10$@net> MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_NextPart_000_0001_01CF202D.806280B0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Ac8gPP/f4rccxsFYRauLVAiwmXOrCwAGZjkg Content-Language: en-us X-ELNK-Trace: ad85a799c4f5de37c2eb1477c196d22294f5150ab1c16ac0b4de374c5ae8ff79d98bb0d2fe5df6333863a497e7c16750350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 98.204.78.83 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01CF202D.806280B0 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0002_01CF202D.806280B0" ------=_NextPart_001_0002_01CF202D.806280B0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit My knowledge and experience with these types of problems is probably a lot less than many others on the list. Plus I have a Legacy. However, I have had intermittent problems with both retraction and extension which appear to be related to hydraulic pressure. Currently, my check list includes a "hydraulic burp" before takeoff. The "burp" is just a on and off of the hydraulic dump valve. Since I have been doing this I have had no problem with the gear not retracting after takeoff. I have also had intermittent problems with the gear not extending and have also solved those with a "hydraulic burp" - on/off of dump valve - when the problem arises. The next time you have a problem suggest you try "burping your baby" and see what happens. D. Brunner From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of frederickemoreno@gmail.com Sent: Sunday, February 02, 2014 12:34 PM To: lml@lancaironline.net Subject: [LML] Lancair IV main landing gear problems 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 ------=_NextPart_001_0002_01CF202D.806280B0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

My knowledge and experience with these types of problems is probably = a lot less than many others on the list.  Plus I have a = Legacy.

 

However, I have had intermittent problems with both retraction and = extension which appear to be related to hydraulic = pressure.

 

Currently, my check list includes a “hydraulic burp” = before takeoff.  The “burp” is just a on and off of the = hydraulic dump valve.  Since I have been doing this I have had no = problem with the gear not retracting after takeoff.  I have also = had intermittent problems with the gear not extending and have also = solved those with a “hydraulic burp” – on/off of dump = valve – when the problem arises.

 

The next time you have a problem suggest you try “burping your = baby” and see what happens.

 

D. Brunner

 

From:= = Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = frederickemoreno@gmail.com
Sent: Sunday, February 02, 2014 = 12:34 PM
To: lml@lancaironline.net
Subject: [LML] = Lancair IV main landing gear = problems

 

 

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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