X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 16 Apr 2009 14:57:21 -0400 Message-ID: X-Original-Return-Path: Received: from fmmailgate01.web.de ([217.72.192.221] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3583394 for lml@lancaironline.net; Thu, 16 Apr 2009 12:58:48 -0400 Received-SPF: none receiver=logan.com; client-ip=217.72.192.221; envelope-from=jschredl@web.de Received: from smtp07.web.de (fmsmtp07.dlan.cinetic.de [172.20.5.215]) by fmmailgate01.web.de (Postfix) with ESMTP id 291D710012D49 for ; Thu, 16 Apr 2009 18:58:13 +0200 (CEST) Received: from [91.12.87.227] (helo=HANSCore2Duo) by smtp07.web.de with smtp (WEB.DE 4.110 #277) id 1LuUui-0000xc-00 for lml@lancaironline.net; Thu, 16 Apr 2009 18:58:12 +0200 Reply-To: From: "Johannes Schredl" X-Original-To: References: Subject: AW: Gear Free Fall X-Original-Date: Thu, 16 Apr 2009 18:58:04 +0200 Organization: --- X-Original-Message-ID: <65EFB9BB9D4A4F52A8CBBEF6D2A2D461@HANSCore2Duo> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0067_01C9BEC5.45D5E410" X-Mailer: Microsoft Office Outlook 11 Thread-Index: Acm+sE92cgAiZntxRACBkjoKSlcgnAAAcCUw In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Original-Sender: jschredl@web.de X-Sender: jschredl@web.de X-Provags-ID: V01U2FsdGVkX1+O9lniZCAP+byDtmqjLU+5An4TeAaw3Ox0HKEi lyyc64ytZ46zPglAni68Hqw+fMVYOx7DubYht1l/jDwBYBVgBz TAQlnafYg= This is a multi-part message in MIME format. ------=_NextPart_000_0067_01C9BEC5.45D5E410 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dom, =20 I can confirm your observations! Many years ago I dicussed this subject with NEICO and gave them = following explanation: - when hydraulic pump is off it shut off the high and low pressure lines = too - opening the free fall valve create a short way of the two chambers of = the hydraulic actuator - problem is: the chamber capacity of the retracting is smaller than the extending caused by the piston rod - hydraulic fluid is almoust incompressible - now free fall of gear - this cause a vacuum in the pusing sinde of the actuator (too less = fluid for chamber)=20 - the lowering gear has to work against this vacuum - the vacuum gradually disapear because of air leakage through the = o-rings =20 You can do the opposite test: - when gear is down and locked - open the free fall valve - now try to push in the gear -> you won=B4t be able to do so because now you are working against the (incombressibel) hydraulic fluid! =20 Typical design error ... ;-( =20 Johannes D-ESWS LNC2 =20 =20 _____ =20 Von: Dominic V. Crain [mailto:domcrain@tpg.com.au]=20 Gesendet: Mittwoch, 15. April 2009 13:51 An: lml@lancaironline.net Betreff: Gear Free Fall I=92d like to draw on the opinion of listers regarding LNC2 gear free = fall problem. The main gear is slow to free fall, and on the jacks (most likely in the air) the RMG won=92t lock in. Slight pressure on the wheel locks it in, which is handy if one wing = walks upside down. Disconnected the actuator strut and it drops like a beauty and snaps = into position. I doubt the actuator struts are the problem because both main gear have exhibited the same problem at the same time. The LMG does eventually = lock down on the jacks. One thing I=92ve noticed is the NG is slower to lock down under normal extension than it usually does. Until recently, it was always the first, = and quick to lock down. Under free fall the gas strut dives the NG down and locks as it should quite quickly. Wondered if anyone might have a trouble shooting sequence I can draw = upon. Thanks Dom Crain VH-CZJ ------=_NextPart_000_0067_01C9BEC5.45D5E410 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Dom,
 
I can confirm your = observations!
Many years ago I dicussed this subject with = NEICO and gave=20 them following explanation:
- when hydraulic pump is off it shut off the = high and low=20 pressure lines too
- opening the free fall valve create a short = way of the two=20 chambers of the hydraulic actuator
- problem is: the chamber capacity of the = retracting is=20 smaller than the extending caused by the piston rod
- hydraulic fluid is almoust=20 incompressible
- now free fall of gear
- this cause a vacuum in the pusing sinde of = the actuator=20 (too less fluid for chamber) 
- the lowering gear has to work against = this=20 vacuum
- the vacuum gradually disapear because of = air leakage through the o-rings
 
You can  do the opposite test:
- when gear is down and = locked
- open the free fall valve
- now try to push in the = gear
-> you won=B4t be able to do so because now = you are=20 working against the (incombressibel) hydraulic = fluid!
 
Typical design error ... = ;-(
 
Johannes
D-ESWS  LNC2
 
 

Von: Dominic V. Crain=20 [mailto:domcrain@tpg.com.au]
Gesendet: Mittwoch, 15. April = 2009=20 13:51
An: lml@lancaironline.net
Betreff: Gear Free=20 Fall

I=92d like to draw = on the opinion=20 of listers regarding LNC2 gear free fall problem.

The main gear is = slow to free=20 fall, and on the jacks (most likely in the air) the RMG won=92t lock=20 in.

Slight pressure on = the wheel=20 locks it in, which is handy if one wing walks upside = down.

Disconnected the = actuator strut=20 and it drops like a beauty and snaps into = position.

I doubt the = actuator struts are=20 the problem because both main gear have exhibited the same problem at = the same=20 time. The LMG does eventually lock down on the = jacks.

One thing I=92ve = noticed is the=20 NG is slower to lock down under normal extension than it usually does. = Until=20 recently, it was always the first, and quick to lock down. Under free = fall the=20 gas strut dives the NG down and locks as it should quite=20 quickly.

Wondered if anyone = might have a=20 trouble shooting sequence I can draw upon.

Thanks

Dom = Crain

VH-CZJ

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