X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 06 Jul 2006 01:08:32 -0400 Message-ID: X-Original-Return-Path: Received: from bmw.hapgoods.com ([65.40.217.234] verified) by logan.com (CommuniGate Pro SMTP 5.1c.2) with ESMTPS id 1225573 for lml@lancaironline.net; Wed, 05 Jul 2006 22:59:30 -0400 Received-SPF: none receiver=logan.com; client-ip=65.40.217.234; envelope-from=matt.hapgood@alumni.duke.edu Received: from HP780N (HP780N.hapgoods.com [192.168.2.100]) (authenticated bits=0) by bmw.hapgoods.com (8.13.6/8.13.6) with ESMTP id k662wgjS002046 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO) for ; Wed, 5 Jul 2006 22:58:44 -0400 From: "Matt Hapgood" X-Original-To: "'Lancair Mailing List'" Subject: Hydraulic issues... more info after tests X-Original-Date: Wed, 5 Jul 2006 22:58:44 -0400 X-Original-Message-ID: <020201c6a0a8$1953ccb0$6402a8c0@hapgoods.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0203_01C6A086.92422CB0" X-Mailer: Microsoft Office Outlook 11 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 Thread-index: AcagpuX4YYcIePnpTIO5h57A3OlTJQAAHoUQAAAixCA= In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0203_01C6A086.92422CB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Fellow listers (especially Lorn, Pat, Chris, Jack and Vern ) ; I went out and did some gear retract/extension tests and recorded the results: here they are (it's confusing, and doesn't jive with what one would expect, so follow closely): 1. The last time I went out the plane, I took a lap around the pattern. The gear wouldn't retract, so I returned to ground, checked the pressure reading (about 1300 PSI), and went home to research the problem. 2. Returned to the plane today - pressure was down 900 - NOTHING had changed except the temperature was significantly cooler and it was cloudy vs. blazing sun. Here's the sequence of what I did next: 3. Turned on the Master. NO pump blip. 4. Put the plane on jackstands 5. Bypassed the "squat" switch 6. Raised the gear lever - and, as expected, the gear retracted perfectly. 7. Pressure on the gauge read 0 as soon as I raised the handle, and stayed there after the gear was retracted and the pump shut off. This indicates it is reading the low side. 8. Lowered the gear handle. 9. The gauge read about 0 the entire lowering process, then, at the last second before the pump shut off, it went to about 800 PSI. 10. Turned off the master 11. Opened the dump valve, and the pressure dropped - but only to about 400 PSI. 12. Closed the dump valve (pressure stayed the same). 13. Turned on the master - the pump "blipped" and the pressure went to about 900 PSI. 14. Raised the gear (same results as 6 - 7). 15. Pulled the pump CB. 16. Opened the dump valve. Result - IMMEDIATE freefall, gauge read 0 the entire way. 17. Lowered the gear handle. 18. Pushed in the CB. 19. Pressure ran up to about 700 PSI. 20. Master off. 21. Opened the dump valve - pressure dropped to about 300 - 400 PSI. 22. Turned on the master - bump blipped up to about 900 PSI. I repeated this process several times and got virtually identical results. Oh, one more thing. When the gear retracts, it sucks up to the point of the gear doors being almost closed, then the pump cycles off and back on, quickly, usually twice, before the gear doors completely close and the pump stops for good. And again, I've never experienced (or noticed) my pump turning on during flight). I then decided to adjust the low pressure switch (it is the adjustable type). I baced the adjustment screw out 1 turn and then repeated steps 14 - 21. This time, when I turned the master on, the pump didn't blip. This suggests my low pressure set point was now below 400 PSI. I played around with this process several times before getting the pressure to 550 PSI, then turning the screw just until the pump blipped. Before I think the pump was set about 650 - 700 PSI, and now I think it is about 550 PSI. That may help matters, but it's not the real problem. An interesting conclusion is that the low pressure limit may be set to 550 PSI, but the pump can't seem to shut itself off quickly enough, so the pressure can still get as high as 800 or even 900 PSI. Based on what some of you had told me, I've got something funky going on with the dump valve. It drops to zero on free fall tests, but does NOT drop to zero when the gear is already extended. Any thoughts? Can any of you confirm what your planes do in this situation? At this point I am very confused, still, about why my pressure is increasing on those hot days to over 1200 PSI, and why it can also decrease later (as I witnessed today vs. two days ago). I'm also very confused about this whole dump valve thing. Please help! Sincerely, Matt Hapgood 919-933-3295 ps. I haven't removed the spool valve, but it doesn't look that difficult to do - it is accessible without removing the pump. ------=_NextPart_000_0203_01C6A086.92422CB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Fellow listers=20 (especially Lorn, Pat, Chris, Jack and Vern ) ;
 
I went = out and did=20 some gear retract/extension tests and recorded the results: here they = are (it's=20 confusing, and doesn't jive with what one would expect, so follow=20 closely):
 
1.  The last=20 time I went out the plane, I took a lap around the pattern.  The = gear=20 wouldn't retract, so I returned to ground, checked the pressure reading = (about=20 1300 PSI), and went home to research the problem.  =
 
2.  Returned to=20 the plane today - pressure was down 900 - NOTHING had changed except the = temperature was significantly cooler and it was cloudy vs. blazing=20 sun.
 
Here's = the sequence=20 of what I did next:
 
3.  Turned on=20 the Master.  NO pump blip.
 
4.  Put the plane on = jackstands
 
5.  Bypassed the "squat" switch
 
6.  Raised the=20 gear lever - and, as expected, the gear retracted perfectly. =20
 
7.  Pressure on=20 the gauge read 0 as soon as I raised the handle, and stayed there = after the=20 gear was retracted and the pump shut off.  This indicates it is = reading the=20 low side.
 
8.  Lowered the=20 gear handle.
 
9.  The gauge=20 read about 0 the entire lowering process, then, at the last second = before the=20 pump shut off, it went to about 800 PSI.
 
10.  Turned off=20 the master
 
11. Opened the=20 dump valve, and the pressure dropped - but only to about 400=20 PSI.
 
12.  Closed the dump = valve=20 (pressure stayed the same).
 
13.  Turned on the = master - the=20 pump "blipped" and the pressure went to about 900 PSI.
 
14.  Raised the = gear (same=20 results as 6 - 7).
 
15.  Pulled the=20 pump CB.
 
16.  Opened the=20 dump valve.  Result - IMMEDIATE freefall, gauge read 0 the entire=20 way.
 
17.  Lowered=20 the gear handle.
 
18.  Pushed in=20 the CB.
 
19.  Pressure=20 ran up to about 700 PSI.
 
20.  Master=20 off.
 
21.  Opened the=20 dump valve  - pressure dropped to about 300 - 400 = PSI.
 
22.  Turned on=20 the master - bump blipped up to about 900 PSI.
 
I = repeated this=20 process several times and got virtually identical = results.
 
Oh, one more thing.  When the gear retracts, it sucks up = to the=20 point of the gear doors being almost closed, then the pump = cycles off and=20 back on, quickly, usually twice, before the gear doors completely close = and the=20 pump stops for good.  And again, I've never experienced (or = noticed) my=20 pump turning on during flight).
 
I then = decided to=20 adjust the low pressure switch (it is the adjustable type).  I = baced the=20 adjustment screw out 1 turn and then repeated steps 14 - 21.  This = time,=20 when I turned the master on, the pump didn't blip.  This suggests = my low=20 pressure set point was now below 400 PSI.  I played around with = this=20 process several
times = before getting=20 the pressure to 550 PSI, then turning the screw just until the pump=20 blipped.  Before I think the pump was set about 650 - 700 PSI, and = now I=20 think it is about 550 PSI.  That may help matters, but it's not the = real=20 problem.
 
An = interesting=20 conclusion is that the low pressure limit may be set to 550 PSI, but the = pump=20 can't seem to shut itself off quickly enough, so the pressure can still = get as=20 high as 800 or even 900 PSI.
 
Based = on what some=20 of you had told me, I've got something funky going on with the dump = valve. =20 It drops to zero on free fall tests, but does NOT drop to zero when = the=20 gear is already extended.  Any thoughts?  Can any of you = confirm what=20 your planes do in this situation?
 
At = this point I am=20 very confused, still, about why my pressure is increasing on those hot = days to=20 over 1200 PSI, and why it can also decrease later (as I witnessed today = vs. two=20 days ago).  I'm also very confused about this whole dump valve = thing. =20
 
Please = help!
 
Sincerely,
 
Matt=20 Hapgood
919-933-3295
 
ps. I = haven't=20 removed the spool valve, but it doesn't look that difficult to do - it = is=20 accessible without removing the pump. 
 
 
 
 
 
 
 
 
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