X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 27 Nov 2013 14:15:24 -0500 Message-ID: X-Original-Return-Path: Received: from qmta07.westchester.pa.mail.comcast.net ([76.96.62.64] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6616929 for lml@lancaironline.net; Wed, 27 Nov 2013 14:11:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.64; envelope-from=jmorgan1023@comcast.net Received: from omta13.westchester.pa.mail.comcast.net ([76.96.62.52]) by qmta07.westchester.pa.mail.comcast.net with comcast id uiff1m00417dt5G57jAXN2; Wed, 27 Nov 2013 19:10:31 +0000 Received: from [192.168.1.103] ([24.11.157.196]) by omta13.westchester.pa.mail.comcast.net with comcast id ujAW1m00e4EXR5U3ZjAXex; Wed, 27 Nov 2013 19:10:31 +0000 From: Jack Morgan Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: multipart/alternative; boundary="Apple-Mail=_E06FB5A1-7813-4350-8433-6644F1542BE5" Subject: Sneak paths X-Original-Date: Wed, 27 Nov 2013 14:10:30 -0500 In-Reply-To: X-Original-To: Lancair Mailing List References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1283) --Apple-Mail=_E06FB5A1-7813-4350-8433-6644F1542BE5 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Hi Colyn, The sneak paths that can retract the nose gear occur in the circuitry = that activates the up relay. The conventional relay is activated with = current (ampere turns) so any sneak path needs to be substantial enough = to actually activate the relay. When considering an electronic relay = solution one needs to take into account that the electronic relay is = voltage activated and requires only a very small amount of sneak current = energy for activation. The low energy required to activate the = electronic relay opens up the possibilities for additional problem = sources (noise, RF transmissions, etc.). In any case just dropping an = electronic relay in place of a conventional one should be tested = carefully, particularly with aircraft that have modifications to the = original Lancair wiring. In the case of the 320/Legacy gear pump, an = inadvertent pump activation ruins your whole day as well as draining = your bank account so a through test regime is prudent. I don't see any obvious sneak path problems created by a snap jack = across the relay coil. The usual suspects for sneak paths are, but not = limited to, added indicators for pump operation, gear in transit = circuitry, safety gear interlock circuitry, and such bells and whistles. For those who venture into the electronic relay world, the typical specs = for the transient conditions on the 12 volt main buss are as follows: Normal operating range. 6 to 18 volts Jump start voltage. 24 volts continuous Load dump 80 volts for 1/2 second (comes from the alternator) Reverse battery 12 volts continuous. Temperature range passenger compartment -40 to +85 centigrade Temperature range engine compartment -55 to +125 centigrade (very = location dependent) The reverse battery requirement can be ignored in aircraft equipped with = a reverse protection diode in the master solenoid activation circuitry. It should be noted that many items in the aircraft that are on the the = radio buss won't meet these specs thus underscoring the importance of = not activating that buss until the engine is operating smoothly and any = jump starting facility is disconnected. Components that only meet the 0 = to 70 centigrade industrial temp range should be avoided as temperatures = above and particularly below that range are common in various parts of = the country and at altitude. Since the gear pump operating properly is unforgiving in the 320/Legacy = set up, I add a particular warning to be very thorough with any changes = that one might make to insure new failure modes are not introduced. A = failed or continuously operating pump in a IV is really only = inconvenient assuming you are checked out on proper usage of the back up = hand pump. I suggest that those interested in further comment on this and the relay = snubber issue contact Colin and/or I off line as this is probably of = further interest to a very limited audience. I am always happy to trade = emails with anyone on LML off line. Keep that nose gear extended and be safe if you experiment with this. Jack Morgan On Nov 26, 2013, at 1:27 PM, Lancair Mailing List wrote: > From: Colyn Case > Subject: Re: [LML] A couple Tyco papers on emf reduction in relays > Date: November 26, 2013 9:36:59 AM EST > To: "Lancair Mailing List" >=20 >=20 > Changing the title back so people who sort on subject will see it. >=20 > Jack, interesting points about the sneak paths. ...I need some = education about how a snapjack would cause that. >=20 > I updated the links late last night. > I think the content of the articles is still valid. >=20 >=20 > The tyco Kilovac line is NOT an electronic (e.g. solid state ) device. = It's an old fashioned coil style relay. Just a well-done one. >=20 > I have no objection to mechanical relays. I'm just saying look at the = specs. > I'm not sure what model number you are talking about when you say the = pump relay specification is well out of the usage range. What is the = usage range? I think someone published a chart once that showed current = draw vs. starting pressure of that pump. It gets pretty high if the = pressure is high (and it's working). If it starts to have an internal = fault, current will get very high. Then you want to be able to turn it = off. >=20 >=20 >=20 --Apple-Mail=_E06FB5A1-7813-4350-8433-6644F1542BE5 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 Hi = Colyn,

The sneak paths that can retract the nose gear = occur in the circuitry that activates the up relay. The conventional = relay is activated with current (ampere turns) so any sneak path needs = to be substantial enough to actually activate the relay. When = considering an electronic relay solution one needs to take into account = that the electronic relay is voltage activated and requires only a very = small amount of sneak current energy for activation. The low energy = required to activate the electronic relay opens up the possibilities for = additional problem sources (noise, RF transmissions, etc.). In any case = just dropping an electronic relay in place of a conventional one should = be tested carefully, particularly with aircraft that have modifications = to the original Lancair wiring. In the case of the 320/Legacy gear pump, = an inadvertent pump activation ruins your whole day as well as draining = your bank account so a through test regime is = prudent.

I don't see any obvious sneak path = problems created by a snap jack across the relay coil. The usual = suspects for sneak paths are, but not limited to, added indicators for = pump operation, gear in transit circuitry, safety gear interlock = circuitry, and such bells and whistles.

For = those who venture into the electronic relay world, the typical specs for = the transient conditions on the 12 volt main buss are as = follows:

Normal operating range. 6 to 18 = volts
Jump start voltage. 24 volts continuous
Load = dump 80 volts for 1/2 second (comes from the = alternator)
Reverse battery 12 volts = continuous.
Temperature range passenger compartment -40 to = +85 centigrade
Temperature range engine compartment -55 = to +125 centigrade (very location = dependent)

The reverse battery requirement can = be ignored in aircraft equipped with a reverse protection diode in the = master solenoid activation circuitry.

It should = be noted that many items in the aircraft that are on the the radio buss = won't meet these specs thus underscoring the importance of not = activating that buss until the engine is operating smoothly and any jump = starting facility is disconnected. Components that only meet the 0 to 70 = centigrade industrial temp range should be avoided as temperatures above = and particularly below that range are common in various parts of the = country and at altitude.

Since the gear pump = operating properly is unforgiving in the 320/Legacy set up, I add a = particular warning to be very thorough with any changes that one might = make to insure new failure modes are not introduced. A failed or = continuously operating pump in a IV is really only inconvenient assuming = you are checked out on proper usage of the back up hand = pump.

I suggest that those interested in = further comment on this and the relay snubber issue contact Colin and/or = I off line as this is probably of further interest to a very limited = audience. I am always happy to trade emails with anyone on LML off = line.

Keep that nose gear extended and be safe = if you experiment with this.

Jack = Morgan





=
= --Apple-Mail=_E06FB5A1-7813-4350-8433-6644F1542BE5--