X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 16 Jul 2013 06:27:56 -0400 Message-ID: X-Original-Return-Path: Received: from nm37-vm8.bullet.mail.ne1.yahoo.com ([98.138.229.136] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTPS id 6374685 for lml@lancaironline.net; Tue, 16 Jul 2013 03:13:38 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.229.136; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.50] by nm37.bullet.mail.ne1.yahoo.com with NNFMP; 16 Jul 2013 07:13:03 -0000 Received: from [98.138.87.7] by tm3.bullet.mail.ne1.yahoo.com with NNFMP; 16 Jul 2013 07:13:02 -0000 Received: from [127.0.0.1] by omp1007.mail.ne1.yahoo.com with NNFMP; 16 Jul 2013 07:13:02 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 948475.58780.bm@omp1007.mail.ne1.yahoo.com Received: (qmail 54570 invoked by uid 60001); 16 Jul 2013 07:13:02 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=MOOXLuWM4fEtT0RrGm799Hpg+gO7FsXQ/Z6n+QPrdImIuBuEDDMx7iU0xahir0Cw8zYtwok8vXeDEwjW1qM2FPgNAXAyirRLHUtZ7uPtS40H/Uu685BCVZwzmqopwNMAWLr/NXNLCrKDUUNiV/Mageuy9gmAySDMHc4RNfcRNrA= ; X-YMail-OSG: J6_6Ml4VM1mSvsevG2kKNVKo5LYK3JIWhH3SBzNCk3sqFvr jYepU2xmfLOtgHaKmiLbcx4XxB1CysxfpCujM0FYRWtTJK3MHtzjFrtHTKms LHOisfxSJX04zppPANHq_Bk7yMubKM9U4iyzjzLN_Qu4onToz3qXEFOLo3gr jwZlMRphY8YRMtwdM0sQiIPNsraWtDNjXh_C5Oc_cO7hE027ClTyPrTmSqGp Aocsef0B_EfYT1ZyzyB394G4dEPbcSp229wvi9xPkJEAQDVCuh5k30WF8mMA .WjJ1Ihno2fQyEdiyiI0cVUShdUnsmn2KPgalFYwkN418MLQz4rG_VCng9ci zxUVlEXWedzzdqbargWba5WwFcl2x9.tflboTCWO62pXGNDS4PZR_75Pa8nx IUqigxYG6wr6QqRiCwxBdjNh.OGIv7OJYLCct86sjLmqF33V95hc_116pK1c 2GAs4zpSgjS.nN2_KiKFO95G.0dIWyyMJw0h.NRk9a2y1_PF6FKPYE3NmSDS qn4UAWx3A3GT1M8GNNRHqGzacnwOyJ4rAJ9yFTmU5xf6cdy1ftSHo4BxzXYJ 3KXiotM2LLjGd.sl8a.vcOpNbXVM- Received: from [97.92.63.83] by web120102.mail.ne1.yahoo.com via HTTP; Tue, 16 Jul 2013 00:13:02 PDT X-Rocket-MIMEInfo: 002.001,SSdtIG5vdCBhIHRydWUgVHJ1VHJhayBleHBlcnQsIGJ1dCBoZXJlIGlzIGFuIGV4cGxhbmF0aW9uIHRoYXQgbWlnaHQgYWRkIHNvbWV0aGluZyB0byB0aGUgZGlzY3Vzc2lvbjogwqBUaGUgVHJ1VHJhayBzZXJ2b3MgYXJlICJzdGVwcGVyIG1vdG9ycywiIGRpc3RpbmN0bHkgZGlmZmVyZW50IGluIG9wZXJhdGlvbiBmcm9tIHRoZSBzZXJ2byBtb3RvcnMgdXNlZCBpbiBvdGhlciBhdXRvcGlsb3RzLiDCoFRoZSBhcm1hdHVyZSBpcyBlc3NlbnRpYWxseSBhIGNvbGxlY3Rpb24gb2YgcGVybWFuZW50IG1hZ25ldHMBMAEBAQE- X-Mailer: YahooMailWebService/0.8.148.557 References: X-Original-Message-ID: <1373958782.54042.YahooMailNeo@web120102.mail.ne1.yahoo.com> X-Original-Date: Tue, 16 Jul 2013 00:13:02 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Re: AFS Pilot X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-1658718958-1166707487-1373958782=:54042" ---1658718958-1166707487-1373958782=:54042 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable I'm not a true TruTrak expert, but here is an explanation that might add so= mething to the discussion: =A0The TruTrak servos are "stepper motors," dist= inctly different in operation from the servo motors used in other autopilot= s. =A0The armature is essentially a collection of permanent magnets and the= stator creates a magnetic field that attracts the magnets. =A0This field i= s the "stepped" around the armature by energizing different coils in succes= sion, and the armature follows in phase with these steps. =A0That's why the= stick can be observed to move in distinct steps, presumably small enough t= o avoid it being obvious. =A0Instead of providing a slip clutch to allow th= e pilot to overcome the servo (on other autopilots, you do routinely test t= he clutch by overpowering the autopilot don't you? =A0You don't? =A0You sho= uld) TruTrak limited the torque capacity of the motor and this can be progr= ammed. =A0Set the autopilot and then overcome it by moving the stick - you can feel it "pop" loose and then grab again. =A0Set the torque capacity so= that the force to overcome is significant, but not so much that you would = have trouble flying the plane that way, at least until you can reach over a= nd shut off the power to the A/P.=0A=0AIn flight, =A0the servo produces a d= istinct characteristic if it is overloaded and slips. =A0Sort like walking = uphill on ice - it progressively moves in the commanded direction until the= opposing force is too high. =A0When the motor slips out of synchronization= it loses it ability to produce torque (and slides downhill). =A0Then when = the force drops sufficiently it gets back into step and tries again. =A0It = pushes and trips, pushes and trips; a characteristic not at all like simple= "hunting," which is smooth and proportional in both directions. =A0If, set= at the highest torque, it still is overloaded in normal maneuvers, you nee= d a higher torque servo. =A0However, in roll you have no clue as to the for= ce imparted by the trim, and the plane will fly just fine in an out-of-trim= condition - the servo doesn't care how much torque it takes to move until = it is more than its capability. =A0If it won't bank or level off =A0you mig= ht want to first check to make sure it isn't out of trim before blaming the servo.=0A=0AFinally, the shear pin: = =A0It is there to protect against the possibility of a mechanically locked = servo motor. =A0Note that, unlike the "others," the TruTrak servo is never = disconnected. =A0The controller simply turns off power you when hand-flying= and you simply back-drive the servo motor. =A0If the motor physically jams= and won't turn (like from a broken tooth in the gear-train) the fix is to = apply enough force with the stick to shear the pin. =A0The pin was never in= tended to shear in any other circumstance. =A0So if your pin shears without= a jammed servo, something is amiss and needs to be fixed. =A0Replacing it = with a stronger pin isn't what I would recommend, as you may not be able to= shear it if you have to. =A0A jammed control that can't be overcome is THE= worst-case scenario.=0A=0AFor what it's worth=0AGary Casey=0A=0A=A0=0ATodd= , et.al.,=0A=0AI have had lots of servo issues with my IV, but solved them = with =3D=0Asettings and a screw - explanation below.=0A=0AThe "micro activi= ty" setting is key for getting rid of the hunting in =3D=0Athe roll axis (i= n my airplane).=A0 With the torque set at its maximum =3D=0A(255) for both = roll and pitch, and the "activity" for each set at around =3D=0A6-7, its a = very good balance between being harsh and hunting all of the =3D=0Atime.=A0= I recently had a servo refurbished and when the install was =3D=0Acomplete= all of these settings were off, and I had to adjust them back.=A0 =3D=0ABu= t when the mechanic reset everything, he also changed the micro =3D=0Aactiv= ity setting to either zero or the max (can't remember).=A0 It hunted =3D=0A= in roll very annoyingly, and I thought it was FUBAR.=A0 Adjusting this =3D= =0Aalong with the torque got me back into the happy place. =3D20=0A=0AAs fo= r the screw - there is a shear pin that is designed to break if the =3D=0At= orque on the servo is too high, presumably to not let the autopilot =3D=0Ao= ver control or fight emergency pilot input.=A0 The bad news is that this = =3D=0Apin was not designed for the high loads in a IV.=A0 I have broken thi= s pin =3D=0Aseveral times in both roll and pitch, just by letting the autop= ilot fly =3D=0Aan approach.=A0 The fix was a great idea by my mechanic to r= eplace this =3D=0Ashear pin with a steel screw, essentially locking the ser= vo to the =3D=0Acontrols.=A0 I deem this safe because there are still 4 oth= er ways to =3D=0Adisable the autopilot (stick button, control head power, o= n/off switch =3D=0Aon the panel, and circuit breaker).=A0 I wanted to throw= that out for =3D=0Aothers who might be having this same problem since we a= re on the =3D=0Asubject.=0A=0AHope this helps=0A=0ABob R=0A ---1658718958-1166707487-1373958782=:54042 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
I'm not a true= TruTrak expert, but here is an explanation that might add something to the= discussion:  The TruTrak servos are "stepper motors," distinctly diff= erent in operation from the servo motors used in other autopilots.  Th= e armature is essentially a collection of permanent magnets and the stator = creates a magnetic field that attracts the magnets.  This field is the= "stepped" around the armature by energizing different coils in succession,= and the armature follows in phase with these steps.  That's why the s= tick can be observed to move in distinct steps, presumably small enough to = avoid it being obvious.  Instead of providing a slip clutch to allow t= he pilot to overcome the servo (on other autopilots, you do routinely test = the clutch by overpowering the autopilot don't you?  You don't?  You should) TruTrak limited the torque capacity of the motor and thi= s can be programmed.  Set the autopilot and then overcome it by moving= the stick - you can feel it "pop" loose and then grab again.  Set the= torque capacity so that the force to overcome is significant, but not so m= uch that you would have trouble flying the plane that way, at least until y= ou can reach over and shut off the power to the A/P.

In flight,  the servo produces a distinct characteristic = if it is overloaded and slips.  Sort like walking uphill on ice - it p= rogressively moves in the commanded direction until the opposing force is t= oo high.  When the motor slips out of synchronization it loses it abil= ity to produce torque (and slides downhill).  Then when the force drops sufficiently it gets back into step and tries again.  It pushes= and trips, pushes and trips; a characteristic not at all like simple "hunt= ing," which is smooth and proportional in both directions.  If, set at= the highest torque, it still is overloaded in normal maneuvers, you need a= higher torque servo.  However, in roll you have no clue as to the for= ce imparted by the trim, and the plane will fly just fine in an out-of-trim= condition - the servo doesn't care how much torque it takes to move until = it is more than its capability.  If it won't bank or level off  y= ou might want to first check to make sure it isn't out of trim before blami= ng the servo.

Finally= , the shear pin:  It is there to protect against the possibility of a = mechanically locked servo motor.  Note that, unlike the "others," the = TruTrak servo is never disconnected.  The controller simply turns off = power you when hand-flying and you simply back-drive the servo motor.  = ;If the motor physically jams and won't turn (like from a broken tooth in t= he gear-train) the fix is to apply enough force with the stick to shear the= pin.  The pin was never intended to shear in any other circumstance. =  So if your pin shears without a jammed servo, something is amiss and = needs to be fixed.  Replacing it with a stronger pin isn't what I woul= d recommend, as you may not be able to shear it if you have to.  A jam= med control that can't be overcome is THE worst-case scenario.

For what it's worth
Gary Casey

 
Todd, et.al.,

I hav= e had lots of servo issues with my IV, but solved them with =3D
settings and = a screw - explanation below.

The "micro activity" setting is key for= getting rid of the hunting in =3D
the roll axis (in my airplane). = With the torque set at its maximum =3D
(255) for both roll and pitch, a= nd the "activity" for each set at around =3D
6-7, its a very good balanc= e between being harsh and hunting all of the =3D
time.  I recently = had a servo refurbished and when the install was =3D
complete all of the= se settings were off, and I had to adjust them back.  =3D
But when = the mechanic reset everything, he also changed the micro =3D
activity se= tting to either zero or the max (can't remember).  It hunted =3D
in= roll very annoyingly, and I thought it was FUBAR.  Adjusting this =3D=
along with the torque got me back into the happy place. =3D20

As= for the screw - there is a shear pin that is designed to break if the =3D<= br>torque on the servo is too high, presumably to not let the autopilot =3D
over control= or fight emergency pilot input.  The bad news is that this =3D
pin= was not designed for the high loads in a IV.  I have broken this pin = =3D
several times in both roll and pitch, just by letting the autopilot = fly =3D
an approach.  The fix was a great idea by my mechanic to re= place this =3D
shear pin with a steel screw, essentially locking the ser= vo to the =3D
controls.  I deem this safe because there are still 4= other ways to =3D
disable the autopilot (stick button, control head pow= er, on/off switch =3D
on the panel, and circuit breaker).  I wanted= to throw that out for =3D
others who might be having this same problem = since we are on the =3D
subject.

Hope this helps

Bob R
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