X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 17 Sep 2007 10:12:04 -0400 Message-ID: X-Original-Return-Path: Received: from rwcrmhc15.comcast.net ([216.148.227.155] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2335332 for lml@lancaironline.net; Mon, 17 Sep 2007 08:41:03 -0400 Received-SPF: none receiver=logan.com; client-ip=216.148.227.155; envelope-from=rpastusek@htii.com Received: from dlhtpax009 (c-69-143-130-212.hsd1.va.comcast.net[69.143.130.212]) by comcast.net (rwcrmhc15) with SMTP id <20070917124025m1500c99v3e>; Mon, 17 Sep 2007 12:40:25 +0000 From: "Robert Pastusek" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Swedish hydraulic oil problem X-Original-Date: Mon, 17 Sep 2007 08:40:14 -0400 X-Original-Message-ID: <002c01c7f927$e8c9f9a0$ba5dece0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002D_01C7F906.61B859A0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Acf4tVyeTUmvpnELRuqv4JpYhXceggAadiPw Content-Language: en-us This is a multipart message in MIME format. ------=_NextPart_000_002D_01C7F906.61B859A0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Christer Wretlind wrote: .If the hydraulic oil disappears during flight what kind of emergency procedure to you have then? It is good to have a handdriven pump when the mainpump fails but to what use if no oil in the system. Last question: On the pic you see the small red pressure cylinder that is mounted in connection with the hydraulic oil system. Can anybody tell me when you need the function of that little pressure tank. As I understood it the high pressure in the small should be enough to lower and lock the gears if main pump fails. But then you have your manual handle to pump down the gears with. So what is the use for this pressure tank? It should be filled with high pressure nitrogen but there is no info in kit instruction how high. Anybody knows that? Christer, The hydraulic oil tank and pump assembly for the Lancair IV/IV-P is designed so the input for the electric pump is higher in the tank than the input for the hand pump. This allows it to have about one quart of oil in the tank that is available to the hand pump but not to the electric pump. At least in theory, you should have oil available to the hand pump after the electric pump "runs dry." I have looked at and measured these items in the tank, but have not actually tested this operation. I have added a procedure in my checklist, however that says basically, if you sense a hydraulic problem-specifically if the electric pump starts running for any unknown reason, you should immediately slow and lower the gear-while you can do it with the electric system. My rationale for this is that some leaks, including failures within the actuator, can make it difficult or impossible to hand pump the gear all the way to the locked position. Better to let the electric pump give it the first try if you can. This doesn't preclude trying the hand pump as an alternative, but the electric pump is much stronger and has a better chance of success as long as it has oil A long time ago I flew fighters that had a compressed nitrogen bottle that could be applied to "blow down" the landing gear. It works, but is a heavy and complex solution to a very infrequent problem. The red cylinder you ask about is a hydraulic accumulator. In the IV-P it serves mostly as a "shock absorber" for the hydraulic system. You've already noted that it is of insufficient volume to lower the gear even one time, although I can usually get 3-4 flap cycles out of it. A larger one would ideally give you one gear down cycle, but this thing needs to hold fluid and nitrogen at more than 1000 PSI, and the weight goes up exponentially as you increase the size. Don't know why the designer didn't use a larger accumulator, given that he used one at all, but I suspect it was a weight/cost issue. I've read in the LML about servicing this accumulator, but as this would be at least third-hand information, I'll leave it for the experts to respond to this. Hope this helps, Bob Pastusek ------=_NextPart_000_002D_01C7F906.61B859A0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

Christer Wretlind wrote:

…If the hydraulic oil disappears during flight what kind of emergency = procedure to you have then? It is good to have a handdriven pump when the mainpump = fails but to what use if no oil in the system.

 

Last question: On the pic you see the small red pressure cylinder that is = mounted in connection with the hydraulic oil system. Can anybody tell me when you = need the function of that little pressure tank. As I understood it the high pressure in the small should be enough to lower and lock the gears if = main pump fails. But then you have your manual handle to pump down the gears with. = So what is the use for this pressure tank? It should be filled with high = pressure nitrogen but there is no info in kit instruction how high. = Anybody knows that?

 

Christer,

The hydraulic oil tank and pump assembly for the Lancair = IV/IV-P is designed so the input for the electric pump is higher in the tank = than the input for the hand pump. This allows it to have about one quart of oil = in the tank that is available to the hand pump but not to the electric pump. At = least in theory, you should have oil available to the hand pump after the = electric pump “runs dry.” I have looked at and measured these items in the = tank, but have not actually tested this operation. I have added a procedure in = my checklist, however that says basically, if you sense a hydraulic = problem—specifically if the electric pump starts running for any unknown reason, you should immediately slow and lower the gear—while you can do it with the = electric system. My rationale for this is that some leaks, including failures = within the actuator, can make it difficult or impossible to hand pump the gear all = the way to the locked position. Better to let the electric pump give it the = first try if you can. This doesn’t preclude trying the hand pump as an = alternative, but the electric pump is much stronger and has a better chance of = success as long as it has oil A long time ago I flew fighters that had a compressed = nitrogen bottle that could be applied to “blow down” the landing = gear. It works, but is a heavy and complex solution to a very infrequent = problem.

 

The red cylinder you ask about is a hydraulic = accumulator. In the IV-P it serves mostly as a “shock absorber” for the = hydraulic system. You’ve already noted that it is of insufficient volume to lower = the gear even one time, although I can usually get 3-4 flap cycles out of it. A = larger one would ideally give you one gear down cycle, but this thing needs to = hold fluid and nitrogen at more than 1000 PSI, and the weight goes up = exponentially as you increase the size. Don’t know why the designer didn’t = use a larger accumulator, given that he used one at all, but I suspect it was = a weight/cost issue. I’ve read in the LML about servicing this = accumulator, but as this would be at least third-hand information, I’ll leave = it for the experts to respond to this.


Hope this helps,

 

Bob Pastusek

 

 

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