X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 04 Oct 2007 20:09:24 -0400 Message-ID: X-Original-Return-Path: Received: from imr-d04.mx.aol.com ([205.188.157.42] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2367352 for lml@lancaironline.net; Wed, 03 Oct 2007 21:22:32 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.42; envelope-from=Sky2high@aol.com Received: from imo-m28.mx.aol.com (imo-m28.mail.aol.com [172.20.107.74]) by imr-d04.mx.aol.com (v107.10) with ESMTP id RELAYIN6-747043fec185; Wed, 03 Oct 2007 21:20:44 -0400 Received: from Sky2high@aol.com by imo-m28.mx.aol.com (mail_out_v38_r9.2.) id q.c2e.1cde1e7b (30738) for ; Wed, 3 Oct 2007 21:05:28 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Wed, 3 Oct 2007 21:05:28 EDT Subject: Re: [LML] Turn Coordinators and Autopilots S-Tec or STEC X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1191459928" X-Mailer: AOL 9.0 VR sub 165 X-Spam-Flag: NO X-AOL-IP: 172.20.107.74 -------------------------------1191459928 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/3/2007 6:02:04 P.M. Central Daylight Time, VTAILJEFF@aol.com writes: For those of you that have STEC autopilot systems please read SAIB 60-21 attached below. The STEC autopilots use the TC for "attitude" reference. Their sales literature tell you how much safer this is over the attitude reference systems other manufacturers use (like King). Unfortunately, STEC does not tell you that if the TC ground wire becomes disconnected or the TC loses the ground signal the AP will still operate by slowly rolling the aircraft one way or another (albeit without an attitude reference). This can pose a big problem in the cockpit if you are IMC (the AP "ready" light is on but the TC is failed) and can cause a pilot to lose control of the aircraft. It is my opinion that this has been the cause of at least two fatal accidents and one serious accident. The survivors of the serious accident -- two instrument rated pilots related how confusing it can be to fly with the AI going one way and the TC going the other way. Unfortunately, STEC is currently fighting one of these cases Federal Court in NJ where I have testified against them and has chosen to not inform its customers of this potentially deadly problem. Jeff, I read it and here is another scenario (I believe I already related this to you)....... S-Tec has failed (an interesting word) to inform the using community of another failure with similar failing results. I have an S-Tec 50 and the pitch control board was messed up during a flight thru a very electrically active cloud in 2001. One of the consequences was damage to a circuit that is the control computer tach test for the TC, a 10 VDC presence on a certain pin - the failure provided a constant 10 VDC on the tach test pin so that even if the TC circuit breaker was pulled (the ultimate power reference signal deletion), the tach test was valid and the AP considered the non-existent lateral management signal from the TC to be valid. S-Tec checked this board twice and confirmed that it was OK (apparently their test procedures do not test very many failure modes) before they finally admitted there was a problem. Activating the AP without a valid signal from the TC results in a slow spiral (or roll if altitude hold is engaged). I have written about this condition before on the LML and REQUIRED PRE-FLIGHT TEST: 0) Before any possible flight in IFR conditions; 1) Pull the TC circuit breaker. 2) Master on, Run the AP thru the test sequence. 3) If the "ready" indicator illuminates - You got a problem baby!!! When my circumstance was finally resolved (replacing the pitch control board) they had already seen a few problems like this. Go ahead, ask how I discovered this failure mode ....................... Note, along with the new pitch control board came a sheet with 38 (?) possible modifications, each involving up to 6 components on the pitch control board to deal with pitch control torque and sensitivity problems - Isn't it nice that Tru-Trak has these critical parameters externally adjustable? Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) Darwinian culling phrase: Watch This! ************************************** See what's new at http://www.aol.com -------------------------------1191459928 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 10/3/2007 6:02:04 P.M. Central Daylight Time,=20 VTAILJEFF@aol.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
For those of you that have STEC autopilot systems please read  S= AIB=20 60-21 attached below. The STEC autopilots use the TC for "attitude" refere= nce.=20 Their sales literature tell you how much safer this is over the attitude=20 reference systems other manufacturers use (like King). Unfortunately, STEC= =20 does not tell you that if the TC ground wire becomes disconnected or the T= C=20 loses the ground signal the AP will still operate by slowly rolling the=20 aircraft one way or another (albeit without an attitude reference). This c= an=20 pose a big problem in the cockpit if you are IMC (the AP "ready" light is=20= on=20 but the TC is failed) and can cause a pilot to lose control of the=20 aircraft. It is my opinion that this has been the cause of at least two fa= tal=20 accidents and one serious accident. The survivors of the serious accident=20= --=20 two instrument rated pilots related how confusing it can be to fly with th= e AI=20 going one way and the TC going the other way.
 
Unfortunately, STEC is currently fighting one of these=20 cases Federal Court in NJ where I have testified against them and has= =20 chosen to not inform its customers of this potentially deadly problem.=20
Jeff,
 
I read it and here is another scenario (I believe I already related thi= s to=20 you)....... 
 
S-Tec has failed (an interesting word) to inform the using community of= =20 another failure with similar failing results. I have an S-Tec 50 a= nd=20 the pitch control board was messed up during a flight thru a very electrical= ly=20 active cloud in 2001.  One of the consequences was damage to a cir= cuit=20 that is the control computer tach test for the TC, a 10 VDC=20 presence on a certain pin - the failure provided a constant 1= 0=20 VDC on the tach test pin so that even if the TC circuit breaker was pulled (= the=20 ultimate power reference signal deletion), the tach test was valid and the A= P=20 considered the non-existent lateral management signal from the TC to be= =20 valid.  S-Tec checked this board twice and confirmed that it was OK=20 (apparently their test procedures do not test very many failure modes)=20 before they finally admitted there was a problem. 
 
Activating the AP without a valid signal from the TC results in a slow=20 spiral (or roll if altitude hold is engaged).  I have written about thi= s=20 condition before on the LML and
 
REQUIRED PRE-FLIGHT TEST:  
 
0) Before any possible flight in IFR conditions;
1) Pull the TC circuit breaker. 
2) Master on, Run the AP thru the test sequence. 
3) If the "ready" indicator illuminates - You got a problem=20 baby!!!  When my circumstance was finally resolved (replacing the=20 pitch control board) they had already seen a few problems like this.
 
Go ahead, ask how I discovered this failure=20 mode ....................... 
 
Note, along with the new pitch control board came a sheet with 38 (?)=20 possible modifications, each involving up to 6 components on the pitch contr= ol=20 board to deal with pitch control torque and sensitivity problems - Isn'= t it=20 nice that Tru-Trak has these critical parameters externally adjustable?= =20
 
Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL=20 (KARR)

Darwinian culling phrase: Watch=20 This!



See wha= t's new at AOL.co= m and Make AOL Your Homepage.
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