s-tec 60 vertical speed

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stapler101

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stapler101
My stec 60 works great except for VS.
I hold the desired vs, (ascending or descending) engage the vs button, and the plane instantly descends at about 1000 fpm regardless of the rate I have set or whether I was climbing or descending.
It is like the vs is hung on -1000.
Any ideas?
 
Try leaving the autopilot on. with heading and altitude hold engaged.
-Disengage Altitude Hold
-Press on the VS button (up ) for a 2 seconds at a time. This should pitch the plane up gently and produce 500 FPM .

If this does not work then something is obviously wrong with a servo, computer ,or instrument.
 
If the altitude hold functions properly, then you have pretty much eliminated the servo and baro input.

On the 60-2, VS mode is an add-on option, so that is a the first logical place to look.
 
stapler101 said:
My stec 60 works great except for VS.
I hold the desired vs, (ascending or descending) engage the vs button, and the plane instantly descends at about 1000 fpm regardless of the rate I have set or whether I was climbing or descending.
It is like the vs is hung on -1000.
Any ideas?
Click to expand...
We have an S-Tec 30 with altitude hold. When it is hot, it works as you mentioned. If the Altitude light does not go out after the initial self-check, we know it will dive as soon as vertical hold is engaged. If it is hot and the light has gone out, we know it may happen. My mechanic has looked into it a few times, but hasn't been able to fix it. We will be trying to find someone around here. I understand that there is someone on Cape Cod who is fabulous with autopilots.
 
Does the Stec 60-2 work in altitude hold mode? If it does, use altitude hold and verify you can use the up-down buttons to change the altitude being held by a small amount. Pressing the up or down button and holding it for about a second should result in an altitude change in the corresponding direction of 20 ft. If you are able to use the buttons to move the altitude up and down small amounts, then the problem is not in the pitch servo and not in a stuck button. Then you probably have a problem in the pitch computer or in the control head. You need to bring the autopilot to an avionics shop that installs and works on Stec autopilots.
 
Thanks for the replies.
John, the altitude hold does work and I can increase/decrease with the up/down buttons.
I suspect a trip to the avionics shop is needed.
One more question. Is there a way to disengage altitude hold once it is set?
The only way I can get it to disengage is by turning the autopilot completely off,
 
Not John, but I have modest troubleshooting skills...

The altitude hold working as described eliminates the servo as a problem; your problem almost certainly lies in the alt pre-select (which is an added unit), or its connections.

Once altitude hold is engaged, you disengage it by selecting a VS mode (up/down) to your new desired altitude and re-engaging alt hold, or disconnecting the autopilot completely.
 
SCCutler said:
Not John, but I have modest troubleshooting skills...

The altitude hold working as described eliminates the servo as a problem; your problem almost certainly lies in the alt pre-select (which is an added unit), or its connections.

Once altitude hold is engaged, you disengage it by selecting a VS mode (up/down) to your new desired altitude and re-engaging alt hold, or disconnecting the autopilot completely.
Click to expand...

I don't think he has altitude preselect.
 
stapler101 said:
Thanks for the replies.
John, the altitude hold does work and I can increase/decrease with the up/down buttons.
I suspect a trip to the avionics shop is needed.
One more question. Is there a way to disengage altitude hold once it is set?
The only way I can get it to disengage is by turning the autopilot completely off,
Click to expand...

You understand it correctly. I think it would be nice to be able to turn off pitch without turning off the entire autopilot, but the 60-2 design point is that if you don't want to hold altitude, then you will use VS or in the case of an ILS, the GS. The Stec 50 and 30 have altitude hold, but don't have a VS mode or GS mode, so they get the on-off switch for altitude hold.
 
We've got a 60-2 in our Aztec and after reading and re-reading the OP, I realize that I've never operated it exactly as was posted. I've only initiated the VS function, either up or down from a state of level flight. I've never initiated it from a climb or decent in an attempt to "hold" a specific VS. I need to take a trip to the operators manual to see if this is mentioned. One question I'll pose is could the absolute pressure transducer be the problem? Water in the static line attached to the transducer? If you dig, S-Tec has some good tech articles in the archives such as this one: http://www.s-tec.com/newsletters/appr797bench.html
 
Jim Burns said:
We've got a 60-2 in our Aztec and after reading and re-reading the OP, I realize that I've never operated it exactly as was posted. I've only initiated the VS function, either up or down from a state of level flight. I've never initiated it from a climb or decent in an attempt to "hold" a specific VS.
Click to expand...

I have with mine. It works great. Once I get flagged when I hit the descent profile on the GPS, enter the VS mode to match. Press altitude hold again when arriving at the destination altitude.

I need to take a trip to the operators manual to see if this is mentioned. One question I'll pose is could the absolute pressure transducer be the problem? Water in the static line attached to the transducer? If you dig, S-Tec has some good tech articles in the archives such as this one: http://www.s-tec.com/newsletters/appr797bench.html
Click to expand...

Sounds like a computer issue or some issue with the baro input to the VS section of the computer since alt hold works.
 
Jim Burns said:
One question I'll pose is could the absolute pressure transducer be the problem? Water in the static line attached to the transducer?
Click to expand...

Jim,

Neither a problem in the pressure transducer or water in the static line would cause the symptoms noted and at the same time not affect altitude hold operation. An avionics shop that knows what they are doing should not need to spend much time troubleshooting to isolate the problem. What ever they find will most likely need to be removed and returned to Stec for repair. My guess is there is a problem in the pitch computer.
 
Sorry Bill, I didn't word that correctly. I use the VS to establish then hold a specific rate of climb or descent, but I normally use the VS button to initiate it rather than as the OP mentioned establishing the rate of climb or descent by hand and then hitting the VS button.
 
Jim Burns said:
Sorry Bill, I didn't word that correctly. I use the VS to establish then hold a specific rate of climb or descent, but I normally use the VS button to initiate it rather than as the OP mentioned establishing the rate of climb or descent by hand and then hitting the VS button.
Click to expand...

That's what I thought you meant. I do both all the time.
 
Jim and Bill,
Help get this through my hard head!
I understand the manual to say that you establish a rate of climb or descent manually (using the yoke) and, once you have the rate you desire, youi then press VS and it "captures" that angle and holds it.
Your post seems to say that you use the VS to establish the rate desired.
How is this done?

PS- on a long cross country today I tried several times to get the VS to hold the rate I had selected (either up or down), and, as I originally posted, the plane immediately pictches downward at a high rate of descent
 
stapler101 said:
Jim and Bill,
Help get this through my hard head!
I understand the manual to say that you establish a rate of climb or descent manually (using the yoke) and, once you have the rate you desire, youi then press VS and it "captures" that angle and holds it.
Your post seems to say that you use the VS to establish the rate desired.
How is this done?

PS- on a long cross country today I tried several times to get the VS to hold the rate I had selected (either up or down), and, as I originally posted, the plane immediately pictches downward at a high rate of descent
Click to expand...

If you don't have a vertical mode selected, but have one of the roll modes selected, you can set a climb or descent rate and then press VS to hold the given rate. This typically might be done in the first climb of the day, although I prefer to not use a vertical mode for the climb. If you already have a vertical mode engaged, for example altitude hold, and you press VS, the vertical speed can be established by pressing and holding either the Up or Down button. For each second you press the up or down button when in VS mode, the autopilot will hold a rate of 160 ft/min in the appropriate direction. So hold it for three seconds and you are around 500 ft/Min.

If you have altitude preselect, you can dial in a climb or decent rate on the preselect unit to set the rate and set an altitude to level off at.
 
John Collins said:
If you don't have a vertical mode selected, but have one of the roll modes selected, you can set a climb or descent rate and then press VS to hold the given rate. This typically might be done in the first climb of the day, although I prefer to not use a vertical mode for the climb. If you already have a vertical mode engaged, for example altitude hold, and you press VS, the vertical speed can be established by pressing and holding either the Up or Down button. For each second you press the up or down button when in VS mode, the autopilot will hold a rate of 160 ft/min in the appropriate direction. So hold it for three seconds and you are around 500 ft/Min.

If you have altitude preselect, you can dial in a climb or decent rate on the preselect unit to set the rate and set an altitude to level off at.
Click to expand...

Agree.

I also prefer not to use it for a climb - too easy to get into a stall if you're forgetful, it's not smart enough to disconnect (and no, I've never done it). I use the VS mode almost exclusively for descent. I find it easier to set the descent rate with the yoke and then turn on VS (use the up/down buttons to "fine tune").

I also use (and really like) the intercept and capture mode when you fly an ILS. Works like a charm. (That would be my other troubleshooting question: can you intercept and hold an ILS, or does the unit drop you into the 1000 fpm descent there, too?)
 
I also rarely use the VS in climb, but normally enter VS mode from a roll steering/altitude hold state. Using the climb/descent buttons after hitting the VS button eliminates the need to (if in altitude hold mode) totally disconnect the autopilot, re-engage the roll steering mode, then trim for desired climb/descent rate, then hit the VS. A simple 1,2,3 count as John mentions is around 500fpm.

Not to confuse the issue, but our only autopilot problem to date was discovered just after we purchased the plane. The pitch servo was wired backwards. We discovered it while reducing power in altitude hold mode and finding the airplane pitch down (rather than up) in a backwards attempt to maintain altitude, when it descended, the autopilot kicked the pitch servo into high speed down trim and we were soon pointed at the ground. I found the fix here http://www.s-tec.com/newsletters/approach0701/approach0701.html in the Tech Bench section. see the link for a link that will lead you to all of the old S-Tec newsletters.
 
My only problem with the 60-2 was a burned out altitude hold servo after I'd owned the plane a few years. It finally gave up on a trip over Arizona riding some gentle mountain currents at 16,000 feet.
 
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