X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 13 Nov 2013 12:17:18 -0500 Message-ID: X-Original-Return-Path: Received: from rc1-smtp.comporium.net ([208.104.2.18] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6588127 for lml@lancaironline.net; Wed, 13 Nov 2013 11:44:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=208.104.2.18; envelope-from=snopercod@comporium.net Received: from rg25.comporium.net ([208.104.244.60]) by rc1-smtp.comporium.net ({6ef86d1c-fcb7-4b71-ab61-5707d6041926}) via TCP (outbound) with ESMTP id 20131113164346643 for ; Wed, 13 Nov 2013 16:43:46 +0000 X-RC-FROM: X-RC-RCPT: Received: from 94.245.235.68.dsl.brvdnc.dynamic.citcom.Net (EHLO _127.0.0.1_) ([68.235.245.94]) by rg24.comporium.net (MOS 4.3.4-GA FastPath queued) with ESMTP id PID26455 (AUTH snopercod); Wed, 13 Nov 2013 11:43:46 -0500 (EST) X-Original-Message-ID: <5283AC3D.70800@comporium.net> X-Original-Date: Wed, 13 Nov 2013 11:43:41 -0500 From: John Cooper User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 X-Original-To: lml@lancaironline.net Subject: Re: N181AM nose gear collapse Content-Type: multipart/alternative; boundary="------------010809050102040201050402" X-MAG-OUTBOUND: comporium.redcondor.net@208.104.244.48/28 This is a multi-part message in MIME format. --------------010809050102040201050402 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Adam-- I'm surprised to learn of this failure and feel badly because I'm the guy who recommended the Bosch relays back in the nineties. The part number installed in my L-235 is 0 332 002 150 with no diodes. Apparently the relays you used (model 0 332 002 156) have diodes to snub the voltage spike when the coil de-energizes, which seems like a good idea. In looking at this data sheet , though, there are some other differences between the -150 and -156 relays. The -150 relays I used have _dual _(Silver Tin Oxide) contacts. They are rated for 40,000 inductive life-cycles and _400A_ inrush. The -156 relays that you used have snubbing diodes across the coil, but only _single _(Silver Nickel) contacts. They, too, are rated for 40,000 inductive life-cycles, but only _250A_ inrush. I can't say that one version is better than the other because the specifications on both of them certainly seem adequate to handle the hydraulic pump. In my installation I installed large ZNRs across the relay contacts to snub the voltage spike from the motor when the contacts open. I also installed smaller ZNRs across the relay coils to (hopefully) protect the pressure switches. You wouldn't need the latter because your relays have the snubbing diodes. (I'll get the ZNR part numbers I used next time I'm at the hangar.) Do you intend to take the relay apart to verify that the contacts are, in fact, welded? Bosch might be interested as well, but I certainly wouldn't mention that you're using their relays in an airplane. --------------010809050102040201050402 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Adam--

I'm surprised to learn of this failure and feel badly because I'm the guy who recommended the Bosch relays back in the nineties. The part number installed in my L-235 is 0 332 002 150 with no diodes. Apparently the relays you used (model 0 332 002 156) have diodes to snub the voltage spike when the coil de-energizes, which seems like a good idea. In looking at this data sheet, though, there are some other differences between the -150 and -156 relays. The -150 relays I used have dual (Silver Tin Oxide) contacts. They are rated for 40,000 inductive life-cycles and 400A inrush. The -156 relays that you used have snubbing diodes across the coil, but only single (Silver Nickel) contacts. They, too, are rated for 40,000 inductive life-cycles, but only 250A inrush. I can't say that one version is better than the other because the specifications on both of them certainly seem adequate to handle the hydraulic pump. In my installation I installed large ZNRs across the relay contacts to snub the voltage spike from the motor when the contacts open. I also installed smaller ZNRs across the relay coils to (hopefully) protect the pressure switches. You wouldn't need the latter because your relays have the snubbing diodes.  (I'll get the ZNR part numbers I used next time I'm at the hangar.)

Do you intend to take the relay apart to verify that the contacts are, in fact, welded? Bosch might be interested as well, but I certainly wouldn't mention that you're using their relays in an airplane.
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