Turn rate on autopilot

[Stratocruiser2]

I would like to ask is there any way to increase the turn rate/bank angle of the Comanche while on autopilot? I cannot seem to get this to turn at more than one degree every two seconds which sometimes can be a bit too wide.

My apologies if this question has already been answered somewhere here but I have been unable to find a solution to this on looking through the topics on the Comanche forum.

[Nick - A2A]

Hello and welcome to the forums!

Which lateral mode of the autopilot are you using? In "HD" (heading) mode, it should perform a standard rate (2 minute) turn, or in other words 3 degrees every second. In "ST" (stabilizer) mode, you can set the turn rate using the steering knob to be as gentle as you wish, or you can use the full knob deflection which, again, should result in a standard rate turn.

If turn performance on autopilot seems to be a bit lacking, it may be worth checking the maintenance hangar (shift + 7) to see if there's an issue with the ailerons themselves. (Do they both deflect fully under manual control for instance?)

One last question: have you downloaded and installed the latest Accu-Sim update?

Cheers,
Nick

[Stratocruiser2]

Hi Nick,

Thank you for the quick reply! I should probably have mentioned that the issue actually arose while I was flying using the autopilot LO TRK mode with the GTN 750, which I have only just purchased. I did use the steering knob in an attempt to improve the roll rate but it did not seem to be achieving a standard rate turn. I will check the ailerons in the hanger next time I am on FSX but when manually flying the Comanche manually in the past, I haven't noticed any problem with the roll rate.

I have now downloaded the Accu-Sim update and will install it later today and run a few test flights.

Many thanks again for your advice and for producing such great aircraft.

Best regards,
Bill

[Nick - A2A]

Hi Bill,

With respect to "LO TRK" and the GTN 750, one thing to bear in mind is that the S-TEC 30 autoilot can't actually follow a flight plan by turning towards new waypoints. Instead, it just follows a course, attempting to keep cross-track error at zero. You'll need to carry out any turns yourself or use "HD" or "ST" mode to fly them.

LO TRK mode will track the course with reduced sensitivity. However, I don't think this means the turn rate is limitied as such; just that it ignores shorter frequency deviations of the CDI.

Let us know how you get on after installing the update and checking the ailerons...

Cheers,
Nick

P.S. I'm not part of A2A by the way - just another customer, but one who hangs out on the forums a bit too much!

[MarcE]

Hi Bill,

the Stec autopilot is completely different to what you are familiar in FSX.

It's a very simplified pilot's right hand but not to let unobserved (as every autopilot actually is).

Here's the manual, found in the comanche's forum at "avionics" =) I'd suggest to make yourself familiar with it to get the full fun out of the comanche (and cherokee)

http://a2asimulations.com/downloads/man ... -30alt.pdf

Greets,
Marc

[SpitfireMelodeon]

I'd suggest to make yourself familiar with it to get the full fun out of the comanche (and cherokee)
Greets,
Marc

I agree and find the Stec much more interesting to use when following flight plans.

Cheers and Beers

Bill

[AKar]

I agree. It is an excellent help but still keeping the game interesting. An old wisdom has been that the most difficult part of flying is going straight and level. This certainly applies in the simulator when one needs to concentrate on the other stuff as well and lacks peripheral vision and ability to look around quickly. The S-TEC gives just the bit of relief that comes handy.

-Esa

[Stratocruiser2]

Thanks all - I have downloaded the manual and will study it this evening. Having been used to autopilots which essentially do everything, I can see that I need to modify my approach to this one as it clearly requires more than mere monitoring. In the past I have always just flown the Cherokee and Comanche manually and this is the first time I have tried their rather unique autopilots but I think I am going to enjoy the more hands-on aspect of the STEC though as it will actually give me a bit more to do during flights.

Nick, I have installed the update and checked the ailerons - they are fine! As you say, the issue was most likely the reduced sensitivity of course tracking in the LO TRK mode as the rate of turn is 'normal' in HDG mode. The situation was probably compounded by a somewhat sharp change in course that I had programmed into the GTN 750, but as other aircraft had followed this without a problem, I thought that the issue was with the roll rate of the Comanche. My apologies, by the way for thinking you were part of A2A!

Bill

[AKar]

Not only does it give you something to do, it also gives you some great features, especially for visual flying - namely the very useful ST-mode and the ability to disconnect the altitude hold regardless of the used lateral mode.

Not sure many people who usually follow the magenta line in NAV-mode find it a bit confusing, but it's not difficult nor restricting in any way... Actually, my tutorial post on the subject is long overdue - I hope to get on to it soon!

-Esa

[Nick - A2A]

Actually, my tutorial post on the subject is long overdue - I hope to get on to it soon!

I'm sure it'll be worth the wait Esa!

In the meantime Bill, there's a short tutorial video on the S-TEC that one of the other forum members made. There's a link to it here.

Cheers,
Nick

[Stratocruiser2]

Thanks Nick! That video plus the STEC manual have allowed me to get to grips with the Comanche (and Cherokee) autopilots and I had a couple of short but very enjoyable flights in both today. I agree with Esa that this autopilot, although pretty vintage technology (like me!) is a pleasure to use once you get the hang of it and it means that you actually have do do something every so often during a flight rather than just sitting watching it or going off to do something else.

My thanks to all who helped me with this query,
Bill

[AKar]

Well, not much more vintage than anything in this kind of airplanes. Actually, I think it is a bit newer. A simple design and robust principles behind gives certain big benefits: for instance, the AP does not depend on any of the flight instruments (except the turn coordinator which is actually a part of the AP unit). That gives a nice dose of extra safety, given how vacuum systems can fail without warning.

-Esa

[William Hughes]

Re: vacuum pump failures without warning. I wanted to add something here: while it is possible for them to fail without warning that is astronomically unlikely. They almost always warn you they are failing. I have seen warning signs several flights in advance of a failure. Low vacuum on run-up, erratic vacuum readings in flight, and the attitude indicator getting the leans at odd times.

Lots of folks have the misapprehension that these things will suddenly cease to exist at random intervals. But sudden failures are due to mechanics leaving oil residue or other junk in the lines after servicing the regulator, distortion of the housing during installation, or other what-not. This will generally occur very soon after the installation.

A wear-type failure is a gradual and very predictable thing as the vanes start to lose their ability to seal against the housing. Lots and lots of warning. If the suction doesn't look right during run-up before an IFR flight in IMC, then do not go.

[AKar]

Well, yes they can and do fail without warning. Most certainly the change is much higher than astronomically unlikely, even if exaggerated in some contexts. Nevertheless, a carbon vane pump is perhaps one of the most unreliable single components on the airplane. But as you say, I could believe a large part of those failures certainly happens on a rather new pump, and most certainly due to mishandling or contaminants - while the first is hard to protect against, the latter is absolutely unacceptable, but of course, still happens from time to time. Another apparent reason for unexpected failures is one I've briefly discussed before: turning them into wrong direction. The thing with vacuum pumps is that they are fragile: any damage in them tends to cascade and cause a failure of the pump as a whole.

Regarding the pump wear, typical pumps I know being installed these days have a wear indicator port through which one can gauge the vane wear. As long as the pump has a healthy amount of vanes remaining, it usually remains fully functional, generally not showing any detectable degradation. Just about only way to 'run out' one is to ignore replacement interval and/or the vane check, the in-service wear of these things does not seem to be fast enough to cause any concern if the intervals are respected.

Edit: A one estimate I remember was that maybe up to 1 in 20 pumps fail in service for reasons other than mistreat or contaminants introduced by maintenance. I don't know, could be.

-Esa

[William Hughes]

The turning them backwards thing depends on the design - some have inclined blades and are susceptible, some have straight blades and are not so affected. Best to be careful if not absolutely sure.