X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 1 [X] Return-Path: Sender: To: lml Date: Mon, 18 Dec 2006 11:55:06 -0500 Message-ID: X-Original-Return-Path: Received: from mx1.pshift.com ([216.57.116.6] verified) by logan.com (CommuniGate Pro SMTP 5.1.3) with ESMTP id 1686417 for lml@lancaironline.net; Mon, 18 Dec 2006 07:59:41 -0500 Received-SPF: none receiver=logan.com; client-ip=216.57.116.6; envelope-from=colyncase@earthlink.net Received: from ccaselt (unverified [216.57.118.129]) by mx1.pshift.com (Vircom SMTPRS 4.35.480.0) with SMTP id for ; Mon, 18 Dec 2006 07:58:51 -0500 Received-SPF: none (mx1.pshift.com: domain of colyncase@earthlink.net does not designate any permitted senders) X-Modus-BlackList: 216.57.118.129=OK;colyncase@earthlink.net=OK X-Modus-RBL: 216.57.118.129=Excluded X-Modus-Trusted: 216.57.118.129=NO X-Original-Message-ID: <11f601c722a4$409388a0$0302a8c0@nvidia.com> From: "colyncase on earthlink" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: electric attitude indicators X-Original-Date: Mon, 18 Dec 2006 04:58:44 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_11F3_01C72261.31E82CE0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 This is a multi-part message in MIME format. ------=_NextPart_000_11F3_01C72261.31E82CE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I guess it is just my naivet=E9 but I am just not familiar enough with = what it takes to get a TSO rating on an instrument except that once it = gets it, the price goes way up Joe, I think the issue is that there is a statistical interaction=20 among a number of variables totally out of your control. =20 Testing tries to capture a larger portion of the statistical=20 population so that you aren't dead because a few of=20 those independent variables aligned one day in a way=20 that will result in malfunction. Is there a vibration in your particular plane=20 that the mechanical isolation the ahrs doesn't=20 damp out sufficiently? Is there electical noise in your airplane=20 that is somehow different enough to affect=20 your unit? How does the unit respond to static=20 discharge? How does the unit behave if there is a large current near by? Is there an attitude excursion that is beyond the capacity of the unit to track? Will you do something in your airplane that=20 will cause the micro-code in the unit to execute=20 a code path that no one else has? Is there a marginal wire connection in the=20 chip that is going to turn into a fuse over time? =20 The problem with these kind of statistics is that=20 even though the failure mode may only occur 1%=20 of the time, when it does occur and you are out of backups, you are having a 100% bad day. It's not like you have a 99% good day every day. I would just note that the cross-bow 425 was built by an experienced company and it failed; not 100% of the time but enough that people=20 eventually walked away. The garmin gmx200 - another piece of digital avionics - is on hold right now because it "sometimes" powers itself down. I bet that unit got more testing than most of these low unit volume ai's. The stec 55x auto-pilot has so much misbehavior in=20 the field that Tom West got 300 replies when he made a post about pitch oscillation problems in a c210. IMO the state of avionics in the field is that certified avionics "almost work", in a statistical sense, leaving anything less well tested somewhere south of that. Is an old vacuum gyro more reliable? maybe not by design but by shear numbers it's been exposed to a much richer set of statistical variables without doing something weird. =20 ------=_NextPart_000_11F3_01C72261.31E82CE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I guess it is just my naivet=E9 but I am just not familiar = enough=20 with what it takes to get a TSO rating on an instrument except that once = it gets=20 it, the price goes way up
 
Joe,
    I think the issue is = that there=20 is a statistical interaction
among a number of variables totally out = of your=20 control.  
Testing tries to capture a larger = portion of the=20 statistical
population so that you aren't dead = because a few of=20
those independent variables aligned one = day in a=20 way
that will result in = malfunction.
 
    Is there a vibration = in your=20 particular plane
that the mechanical isolation the ahrs = doesn't=20
damp out sufficiently?
 
    Is there electical = noise in your=20 airplane
that is somehow different enough to = affect=20
your unit?
 
    How does the unit = respond to=20 static
discharge?
 
    How does the unit = behave if=20 there is a large
current near by?
 
    Is there an attitude = excursion=20 that is beyond
 the capacity of the unit to=20 track?
 
    Will you do = something in your=20 airplane that
will cause the micro-code in the unit = to execute=20
a code path that no one else = has?
 
    Is there a marginal = wire=20 connection in the
chip that is going to turn into a fuse = over=20 time?
   
    The problem with = these kind of=20 statistics is that
even though the failure mode may only = occur 1%=20
of the time, when it does occur and you = are=20 out
of backups,  you are having a 100% = bad=20 day.
It's not like you have a 99% good day = every=20 day.
 
    I would just note = that the=20 cross-bow 425 was
built by an experienced company and it=20 failed;
not 100% of the time but enough that = people=20
eventually walked away.
 
    The garmin gmx200 - = another=20 piece of digital
avionics -  is on hold right now = because it=20 "sometimes"
powers itself down.   I bet = that unit got=20 more
testing than most of these low unit = volume=20 ai's.
 
    The stec 55x = auto-pilot has so=20 much misbehavior in
the field that Tom West got 300 replies = when=20 he
made a post about pitch oscillation = problems in a=20 c210.
 
    IMO the state of = avionics in the=20 field is that
certified avionics "almost work", in a=20 statistical
sense, leaving anything less well = tested=20 somewhere
south of that.
 
    Is an old vacuum = gyro more=20 reliable? maybe not by
design but by shear numbers it's been=20 exposed
to a much richer set of statistical = variables=20 without
doing something weird.
 
 
 
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