KAP 140 autopilot FAQ
Posted: 04 Sep 2013, 10:54
We have spent great deal of time implementing (and testing) the KAP 140 autopilot, so that it operates just like the real unit. Because of that, it behaves differently than stock FSX autopilot you may be used to. It has some unique "features" that may surprise even real pilots who are not familiar with this system. Here are some most common questions that we've seen:
1. I can't engage Autopilot using the key in the VC.
You have to press it and hold it for at least 250 milliseconds. Safety feature of the real unit.
2. VOR / Localizer tracking does not work correctly
Basically for all modes that involve the use of CDI (NAV/APR/REV) you have to set the HDG bug to match OBS setting (NAV) or ILS course. This is because the HDG bug is the only source of plane heading AND course reference. The autopilot doesn't get that signal from the OBS gauge. The flashing HDG after you arm one of those modes is a reminder for that.
For example if you are following VOR radial 250, but you have your heading bug at 330, the autopilot will think that the desired course is 330, but will still try to match the CDI which is set for radial 250. This will cause completely erratic behavior.
It's a limitation of an KAP autopilot coupled with simple directional gyro. If we had a HSI installed, it would work more like the other autopilots you are used to. But that would be boring, wouldn't it?
3. When I press ALT button the altitude window does not update.
This is just how the real one works.
4. The autopilot does not intercept selected altitude.
If the altitude is not armed (ALT ARM displayed in the lower row), then the autopilot will continue the climb/descend.
5. When I change the selected altitude, the autopilot does not climb/descend.
If you are in the ALT hold mode, you have to exit it first (by pressing the ALT button), then set your desired vertical speed using UP/DOWN buttons. Oh, and don't forget to check, that the new altitude is ARMed.
6. The autopilot has intercepted the altitude, but it's off by couple hundred feet.
The autopilot has separate barometric pressure entry, it's not connected to the altimeter on the main panel. Press the BARO button and set the correct pressure there.
7. I see some vertical oscillations in ALT/VS.
The autopilot does not have vertical gyro, meaning that it does not know the aircraft's pitch. The only source of reference for elevator control is Vertical Speed gauge, which is relatively imprecise and slow to react. You may experience some oscillations, especially with aft cg, although we have tried to minimize those.
8. REV mode does not work.
To follow a backcourse approach, you have to set the HDG bug to the ILS localizer direction, not to the direction you want to fly (reverse). For example if the runway ILS is 120 degrees and you want to fly backcourse (300 degrees) you have to set the HDG bug to 120 degrees.
1. I can't engage Autopilot using the key in the VC.
You have to press it and hold it for at least 250 milliseconds. Safety feature of the real unit.
2. VOR / Localizer tracking does not work correctly
Basically for all modes that involve the use of CDI (NAV/APR/REV) you have to set the HDG bug to match OBS setting (NAV) or ILS course. This is because the HDG bug is the only source of plane heading AND course reference. The autopilot doesn't get that signal from the OBS gauge. The flashing HDG after you arm one of those modes is a reminder for that.
For example if you are following VOR radial 250, but you have your heading bug at 330, the autopilot will think that the desired course is 330, but will still try to match the CDI which is set for radial 250. This will cause completely erratic behavior.
It's a limitation of an KAP autopilot coupled with simple directional gyro. If we had a HSI installed, it would work more like the other autopilots you are used to. But that would be boring, wouldn't it?
3. When I press ALT button the altitude window does not update.
This is just how the real one works.
4. The autopilot does not intercept selected altitude.
If the altitude is not armed (ALT ARM displayed in the lower row), then the autopilot will continue the climb/descend.
5. When I change the selected altitude, the autopilot does not climb/descend.
If you are in the ALT hold mode, you have to exit it first (by pressing the ALT button), then set your desired vertical speed using UP/DOWN buttons. Oh, and don't forget to check, that the new altitude is ARMed.
6. The autopilot has intercepted the altitude, but it's off by couple hundred feet.
The autopilot has separate barometric pressure entry, it's not connected to the altimeter on the main panel. Press the BARO button and set the correct pressure there.
7. I see some vertical oscillations in ALT/VS.
The autopilot does not have vertical gyro, meaning that it does not know the aircraft's pitch. The only source of reference for elevator control is Vertical Speed gauge, which is relatively imprecise and slow to react. You may experience some oscillations, especially with aft cg, although we have tried to minimize those.
8. REV mode does not work.
To follow a backcourse approach, you have to set the HDG bug to the ILS localizer direction, not to the direction you want to fly (reverse). For example if the runway ILS is 120 degrees and you want to fly backcourse (300 degrees) you have to set the HDG bug to 120 degrees.