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S-TEC 60-2 requires re-trim after altitude hold?
Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is
equipped with this AP. The previous owner demonstrated an idiosyncrasy with the AP that I would like to correct, if possible. Using the AP to hold VSI, the aircraft is in a climb. Upon reaching the assigned altitude, I push the ALT button on the AP. The aircraft, since it overshot the altitude by 100 feet or so, descends and levels off at the altitude where I engaged the ALT hold, then begins a speed increase to cruise speed. Now for the idiosyncrasy: The AP is engaged and the aircraft is holding perfectly at the desired altitude. However, if I disengage the AP, the aircraft immediately begins a climb, suggesting that there is a slight nose-up trim situation that was being held back by the AP. To overcome this, the previous owner suggested that after level-off, disengage the AP, manually re-trim, then re-engage the AP. How can the S-TEC AP be adjusted to hold the altitude after a climb without the nose-up trim problem? It seems to me that, over time, this problem could result in premature wear and tear of the AP control servos, no? -- Peter ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
#2
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In article ,
Peter R. wrote: Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is Now for the idiosyncrasy: The AP is engaged and the aircraft is holding perfectly at the desired altitude. However, if I disengage the AP, the aircraft immediately begins a climb, suggesting that there is a slight nose-up trim situation that was being held back by the AP. I have an S-Tec 50. Mine is not connected to the electric trim (not sure why -- the plane had electric trim as a factory option). The S-Tec will call for trim if it can't hold the elevator itself (annunciator on the AP), but it can hold a significant amount of pressure -- enough to really scare you if you disengage it accidentally or without realizing the trim situation. It's not clear from S-Tec's site whether the 60-2 is always installed in an automatic trim configuration (standard is 'altitude hold with altitude trim' but optional is 'automatic electric pitch trim'). You may be seeing normal behavior. -- Ben Jackson http://www.ben.com/ |
#3
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Call Autopilots Central in Tulsa and make an appointment to get it
fixed correctly. On Mon, 1 Mar 2004 10:07:19 -0500, Peter R. wrote: Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is equipped with this AP. The previous owner demonstrated an idiosyncrasy with the AP that I would like to correct, if possible. Using the AP to hold VSI, the aircraft is in a climb. Upon reaching the assigned altitude, I push the ALT button on the AP. The aircraft, since it overshot the altitude by 100 feet or so, descends and levels off at the altitude where I engaged the ALT hold, then begins a speed increase to cruise speed. Now for the idiosyncrasy: The AP is engaged and the aircraft is holding perfectly at the desired altitude. However, if I disengage the AP, the aircraft immediately begins a climb, suggesting that there is a slight nose-up trim situation that was being held back by the AP. To overcome this, the previous owner suggested that after level-off, disengage the AP, manually re-trim, then re-engage the AP. How can the S-TEC AP be adjusted to hold the altitude after a climb without the nose-up trim problem? It seems to me that, over time, this problem could result in premature wear and tear of the AP control servos, no? |
#4
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On Mon, 1 Mar 2004 10:07:19 -0500, Peter R.
wrote: Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is equipped with this AP. The previous owner demonstrated an idiosyncrasy with the AP that I would like to correct, if possible. I don't think you are going to find any thing wrong with the AP. OTOH my experience is limited to only a couple of planes and mine has an S-Tec 50 with altitude hold. Using the AP to hold VSI, the aircraft is in a climb. Upon reaching the assigned altitude, I push the ALT button on the AP. The aircraft, since it overshot the altitude by 100 feet or so, descends and levels off at the altitude where I engaged the ALT hold, then begins a speed increase to cruise speed. Is the speed exactly the same as it was prior to the climb, or is the power setting the same? If you have climbed and the bo is going faster it will require the trim be reset. Now for the idiosyncrasy: The AP is engaged and the aircraft is holding perfectly at the desired altitude. However, if I disengage the AP, the aircraft immediately begins a climb, suggesting that there is a slight nose-up trim situation that was being held back by the AP. To overcome this, the previous owner suggested that after level-off, disengage the AP, manually re-trim, then re-engage the AP. The Bo is very sensitive to trim and speed. slight differences are going to require retrimming. The AP will correct the situation, but when disconnected the trim will go back to its manual setting resulting in a climb or descent. If very far out of trim the change can be rather abrupt. How can the S-TEC AP be adjusted to hold the altitude after a climb without the nose-up trim problem? It seems to me that, over time, this problem could result in premature wear and tear of the AP control servos, no? As the AP is continually adjusting the trim, it's unlikely it would add any wear due to the out-of-trim situation. Get into some turbulence and that sucker can change so fast it'll do a better job of holding altitude that I can. OTOH that's when I turn it off to reduce stresses. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
#5
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"Ben Jackson" wrote in message news:5tM0c.156461$jk2.597098@attbi_s53... It's not clear from S-Tec's site whether the 60-2 is always installed in an automatic trim configuration (standard is 'altitude hold with altitude trim' but optional is 'automatic electric pitch trim'). You may be seeing normal behavior. It certainly isn't always -- ours isn't connected to the trim. Sounds like the AP isn't talking to the trim system in Peter's case, though that may be because of a problem rather than by choice. Julian |
#6
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Peter R. wrote:
Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is equipped with this AP. The previous owner demonstrated an idiosyncrasy with the AP that I would like to correct, if possible. Using the AP to hold VSI, the aircraft is in a climb. Upon reaching the assigned altitude, I push the ALT button on the AP. The aircraft, since it overshot the altitude by 100 feet or so, descends and levels off at the altitude where I engaged the ALT hold, then begins a speed increase to cruise speed. Now for the idiosyncrasy: The AP is engaged and the aircraft is holding perfectly at the desired altitude. However, if I disengage the AP, the aircraft immediately begins a climb, suggesting that there is a slight nose-up trim situation that was being held back by the AP. To overcome this, the previous owner suggested that after level-off, disengage the AP, manually re-trim, then re-engage the AP. How can the S-TEC AP be adjusted to hold the altitude after a climb without the nose-up trim problem? It seems to me that, over time, this problem could result in premature wear and tear of the AP control servos, no? You don't mention whether your a/p installation includes the *optional* "automatic electric pitch trim" as specified on the STEC web site http://www.s-tec.com/products/ap2rpff.html The behavior you describe is exactly what I see routinely with the System 55 a/p in my plane, and is normal without the automatic electric option, which I plan to have installed soon. Trim setting for climb power and airspeed is not usually where trim will be once you level and set cruise power, and that variance is what's causing the phenomenon you're seeing. The a/p is capable of holding altitude even with some relatively high pitch forces, but I agree with you - what's the sense in asking the pitch servo to work against those pressures? I always disconnect and retrim when I level out for cruise. |
#7
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CriticalMass ) wrote:
You don't mention whether your a/p installation includes the *optional* "automatic electric pitch trim" as specified on the STEC web site http://www.s-tec.com/products/ap2rpff.html I don't know if this AP includes this option. I am still learning a lot about the aircraft and its systems, but I will look into this. -- Peter ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
#8
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Roger Halstead ) wrote:
Is the speed exactly the same as it was prior to the climb, or is the power setting the same? No, the speed is definitely not the same. The aircraft climbs at 110 kts indicated, then cruises at the top of the green arc with wide open throttle (this is a turbonormalized engine), which is about 170 kts indicated. If you have climbed and the bo is going faster it will require the trim be reset. I was spoiled by the Bendix/King KAP140, which had an altitude select and capture that used the electric trim to maintain level flight, no matter if the aircraft were accelerating or decelerating. If I disconnected the AP (resulting in a loud disconnect tone), the aircraft was in perfect elevator trim for the attitude and speed. Of course, the B/K AP did not have GPS steer, which is a nice feature of the 60-2. -- Peter ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
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