X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 01 May 2009 16:26:59 -0400 Message-ID: X-Original-Return-Path: Received: from imr-m06.mx.aol.com ([64.12.138.200] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3612838 for lml@lancaironline.net; Fri, 01 May 2009 10:57:01 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.138.200; envelope-from=Sky2high@aol.com Received: from imo-ma03.mx.aol.com (imo-ma03.mx.aol.com [64.12.78.138]) by imr-m06.mx.aol.com (v107.10) with ESMTP id RELAYIN2-349fb0d7532e; Fri, 01 May 2009 10:55:49 -0400 Received: from Sky2high@aol.com by imo-ma03.mx.aol.com (mail_out_v40_r1.5.) id q.ceb.57e60c5d (29679); Fri, 1 May 2009 10:55:27 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Fri, 1 May 2009 10:55:26 EDT Subject: Re: [LML] LNC2 gear X-Original-To: lml@lancaironline.net X-Original-CC: troneill@charter.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1241189726" X-Mailer: AOL 9.1 sub 5006 X-Spam-Flag:NO X-AOL-IP: 64.12.78.138 -------------------------------1241189726 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Terrence, In review: 0. Assuming all plumbing is per Lancair specs. 1. After any normal gear down condition, fluid is everywhere in the system= , all actuators are fully extended and the pump valves are set so that no= fluid can flow back to the reservoir from the down-side, even if the fluid= pressure is not at the down pressure switch range (power not recently switched on). 2. Confirming the above condition, an attempt to unlock the over center = link is unsuccessful because the nose gear actuator fluid has no place to= go. 3. The dump valve is opened so that fluid from the down-side can flow to= the up-side and the nose gear is unlocked with the actuator moving down-s= ide fluid to up-side. 4. Alas, there is not enough fluid to fill the up-side because the volume= requirement is larger since the up-side lacks the space taken up by the = actuator push rod on the down-side. 5. The fluid needed to satiate the up-side can now come from one of two= sources: Either the reservoir thru the pump (up-side valve) or from other= down-side actuators (including door actuators that are spring loaded). = I have never observed your problem and would assume that pump valves should have= allowed flow from the reservoir to the up-side of the nose gear. SO, in= your case, even though all the aircraft weight (including tail weight) on= the mains should have not have allowed them to be drawn in by fluid being sucked from the down-side (I am impressed by the leverage you got thru th= e nose gear). However, that must have happened in order to supply the needed fluid. Note that this is extraordinary because fluid needed to fill the= main actuators up-side has also got to come from somewhere. 6. When you then lowered the nose gear, there would have been excess fluid= and it must have flowed back to the reservoir rather than re-fill the down= side of the main gear. Perhaps this was thru the up-side pump valve because the down-side should still not have allowed fluid to flow back ou= t. Perhaps the pump shuttle valve was not where it was supposed to be. 7. "I managed to get the jack in place and raise the wing enough to push= the gear in place and pull the over-center strut to lock." One should ne= ver have to "pull" the over center links with the dump valve open as when the= y reach a certain position, the spring should snap them in place. Somethin= g does not seem right. 8. Did you do a free fall check after you got all this straightened out?= Did the nose gear snap smartly into place and lock? Did the mains requi= re no more than 3 pounds of side load to get them locked? If any of these= questions are answered with a "no", don't go flying yet. 9. Your scenario failed to mention slowing to 87 KIAS (100 mph) before completing the emergency operation. The free fall situation should succee= d whether or not fluid is in the system. The nose gear gas strut must be= exerting 100 psi to push down, lock and keep locked the nose gear and the= over center link. Whatever spring system is used for the mains, it should be= able to keep the over center link locked once the gear is down and any ya= w maneuver is used to get a sticky main to lock. Note that getting the gear down with the dump valve open requires less fluid transfer that going the other way. I am sure Chris Z can discuss the valve positions more clearly than I can= . Scott Krueger In a message dated 4/30/2009 6:56:21 P.M. Central Daylight Time, troneill@charter.net writes: Here's an interesting quirk of the retract system, I think.... Yesterday, spurred by a helpful LML suggestion to increase the preload in= my nose strut, I chocked the mains, weighted the tail, and supported the= nose with the nosewheel an inch off the ground, in order to rotate the nosegear up a little in order to get an air chuck on the schroeder valve= less than an inch behnd #3 exhaust tube. So I pushed up the over- still locked up. So I opened the free-fall valve. Pushed back the nose strut, chucked my new $22. / 300 psi made-in-= china strut pump, on, and put in the max. Then lowered the nosewheel to over-center lock, lowered the nose, removed= the weight on the tail, and observed 3 inches of strut! So I pulled the plane out to run an engine idle check, and glanced at the= right wing, was shocked to see the gear leaning inward about 10 degrees.= ! I managed to get the jack in place and raise the wing enough to push the= gear in place and pull the over-center strut to lock. Checked the left gear... and found its over-center strut pushed up, unlocked, too! Jacked and pulled it down, and then put the plane back in the hangar and= ran a retract-extend check -- after putting the free-fall valve back in= closed position. My guess is that with the hydraulic system closed/normal, in pushing the= nosegear over-center lock up and pushing back on the nosewheel I also hydraulic-pressured the main cylinders to pull their over-center locks up= . So, if this is true, then here's a scenario to consider: Gear down, no nose green light. System pump or solenoid CB pops. SO, pull the pump CB, gear switch in Down, valve to free-fall. Still can't get a nose green light. Just the mains. To land, should the free-fall valve be left open, or moved to closed? If it is moved to closed, and the nosegear is not locked over-center...= will aft pressure on touchdown unlock the mains too, damaging not only th= e prop/engine but also the gear and fuselage? Terrence L235/320 N211AL No virus found in this outgoing message Checked by PC Tools AntiVirus (5.0.0.22 - 10.100.057). _http://www.pctools.com/free-antivirus/_ (http://www.pctools.com/free-antivirus/) **************Join ChristianMingle.com=AE FREE! Meet Christian Singles in= your area. Start now! (http://pr.atwola.com/promoclk/100126575x1221673648x1201419171/aol?redir= =3Dhttp://www.christianmingle.com/campaign.html%3Fcat%3Dadbuy%26 src%3Dplatforma%26adid%3Dfooter:050109%26newurl%3Dreg_path.html) -------------------------------1241189726 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Terrence,
 
In review:
 
0.  Assuming all plumbing is per Lancair specs.
 
1. After any normal gear down condition, fluid is everywhere in the= system, all actuators are fully extended and the pump valves are set so that= no fluid can flow back to the reservoir from the down-side, even if the fluid= pressure is not at the down pressure switch range (power not rec= ently switched on).
 
2. Confirming the above condition, an attempt to unlock the over cent= er link is unsuccessful because the nose gear actuator fluid has no place to= go.
 
3. The dump valve is opened so that fluid from the down-side can flow= to the up-side and the nose gear is unlocked with the actuator moving down-side fluid to up-side.
 
4. Alas, there is not enough fluid to fill the up-side because the vo= lume requirement is larger since the up-side lacks the space taken up by= the actuator push rod on the down-side.
 
5. The fluid needed to satiate the up-side can now come fro= m one of two sources: Either the reservoir thru the pump (up-side valve) or= from other down-side actuators (including door actuators that are spring loaded).  I have never observed your problem and would assume that pu= mp valves should have allowed flow from the reservoir to the up-side of the= nose gear.  SO, in your case, even though all the aircraft weight (including tail weight) on the mains sh= ould have not have allowed them to be drawn in by fluid being sucked from the= down-side (I am impressed by the leverage you got thru the nose gear). However, that must have happened in order to supply the needed fluid.=   Note that this is extraordinary because fluid needed to fill&nbs= p;the main actuators up-side has also got to come from somewhere.
 
6. When you then lowered the nose gear, there would have been excess= fluid and it must have flowed back to the reservoir rather than re-fill the down= side of the main gear.  Perhaps this was thru the up-side pump valve becau= se the down-side should still not have allowed fluid to flow back out. = Perhaps the pump shuttle valve was not where it was supposed to be.
 
7. "I managed to get= the jack in place and raise the wing enough to push the gear in place and pull the= over-center strut to lock."  One should never have= to "pull" the over center links with the dump valve open as when they reach= a certain position, the spring should snap them in place.  Something do= es not seem right.
 
8.= Did you do a free fall check after you got all this straightened out? = Did the nose gear snap smartly into place and lock?  Did the mains= require no more than 3 pounds of side load to get them locked? = If any of these questions are answered with a "no", don't go flying yet.&nbs= p;
 
9. Your scenario failed to mention slowing to 87 KIAS (100 mph) befor= e completing the emergency operation.  The free fall situation should= succeed whether or not fluid is in the system.  The nose gear gas strut= must be exerting 100 psi to push down, lock and keep locked the nose gear= and the over center link.  Whatever spring system is used for the mains,= it should be able to keep the over center link locked once the gear is down= and any yaw maneuver is used to get a sticky main to lock. 
 
Note that getting the gear down with the dump valve open requires les= s fluid transfer that going the other way.
 
I am sure Chris Z can discuss the valve positions more clearly than= I can.
 
Scott Krueger
 
In a message dated 4/30/2009 6:56:21 P.M. Central Daylight Time, troneill@charter.net writes:
Here's an interesti= ng quirk of the retract system, I think....
Yesterday, spurred= by a helpful LML suggestion to increase the preload in my nose strut, I chock= ed the mains, weighted the tail, and supported the nose with the nosewheel an= inch off the ground, in order to rotate the nosegear up a little in order to= get an air chuck on the schroeder valve less than an inch behnd #3 exhaust= tube.
So I pushed up the= over- still locked= up. So I opened the free-fall valve. Pushed back the nose strut, chucked my= new $22. / 300 psi made-in-china strut pump, on, and put in the max. =
Then lowered the no= sewheel to over-center lock, lowered the nose, removed the weight on the tail, and obs= erved 3 inches of strut!
So I pulled the pla= ne out to run an engine idle check, and glanced at the right wing, was shocked to= see the gear leaning inward about 10 degrees. !
 
I managed to get th= e jack in place and raise the wing enough to push the gear in place and pull the= over-center strut to lock.
Checked the left ge= ar... and found its over-center strut pushed up, unlocked,  too!
Jacked and pulled= it down, and then put the plane back in the hangar and ran a retract-extend check= -- after putting the free-fall valve back in closed position.
My guess is that wi= th the hydraulic system closed/normal, in pushing the nosegear over-ce= nter lock up and pushing back on the nosewheel I also hydraulic-pressured the= main cylinders to pull their over-center locks up.
 
So, if this is= true, then here's a scenario to consider:
Gear down, no nose= green light.
System pump or= solenoid CB pops. 
SO, pull the pump= CB, gear switch in Down, valve to free-fall.
Still can't get a= nose green light. Just the mains.
 
To land, should the= free-fall valve be left open,  or moved to closed? 
 
If it is moved to= closed, and the nosegear is not locked over-center... will aft pr= essure on touchdown unlock the mains too, damaging not only the prop/engine but= also the gear and fuselage?
 
Terrence
L235/320 N211AL


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