KAP140 Autopilot

The KAP140 Two Axis system provides both lateral (roll) and vertical modes (pitch / pitch trim) with altitude preselect. It is a capable AP, but certainly not the latest generation. The only possible upgrade path at this time is the GFC700, which requires upgrading the entire G1000 system. Until a more affordable and less time-consuming replacement of just the AP itself is available (which may or may never happen) we will need to live with it.

Please read below noteworthy aspects:

  • Be sure to be familiar with the AFMS; taking a thorough look at the Pilot’s Guide is also strongly recommended. Practice use of the AP in the simulator!
  • AFMS / Page 15: Following the preflight self test [PFT], the red P warning on the face of the autopilot may illuminate indicating that the pitch axis cannot be engaged. This condition should be temporary, lasting approximately 30 seconds. The P will extinguish and normal operation will be available
  • Even if you are not planning on using or even turning on the AP, it‘s important to understand that its Altitude Alerter feature will issue alert tones (approaching target altitude within 1,000’ and leaving target altitude beyond 200’) – those can be quite distracting when you e.g. do pattern work. An easy way to address that is to use the KAP140’s Altitude Select knob and turn it way up to an altitude you‘re unlikely going to be at during your training day, e.g. 10,000‘
  • Lateral guidance (HDG, NAV) is as straight-forward as with any other AP, but vertical operation is a bit quirky due to the unfortunate ALT button toggle functionality on this device and the ARM button (that doesn’t exist on newer APs).
    Since the AP is not as tightly integrated as a GFC700, you will want to make it a habit in the Twin Stars to always
    • Set the altimeter setting in three places – the G1000, the AP’s BARO, and the round backup Altimeter
    • The altitude bug always should be set in two places – the G1000 and the AP
      • The AP is not connected to the G1000’s BARO MIN altimeter bug used for DA/MDA
      • Also, unlike newer digital APs, the KAP140 does not always automatically ARM in vertical modes – make sure your target altitude is not just set, but also armed to avoid missing the target altitude. Use CWS to correct if that happens to you. Speaking of which…
  • CWS is your silent friend – remember you can use it to temporarily take manual control and then pass it back to the AP, e.g. to set a specific climb speed (instead of a climb rate that, if too optimistic, can lead to too low an airspeed) – a good workaround for the lack of an IAS/FLC button –, to quickly fix a targeted altitude or to fly around a cloud on a VFR XC.
    For more insights on using control wheel steering search Diamond’s AP AFMS for CWS; you will find it a very informative document.
  • Always check if the AP is actually engaged (the little encased AP in the screenshot above – it’s easy to spend time programming automation only to find out too late that it was never engaged… ask me how I know that 🙂
  • Even more important than knowing how to use the autopilot before using it is to know how to disconnect / turn it OFF in case it does something you don’t expect so that you have time to figure out what happened before getting into a dangerous attitude.
    • NEVER FIGHT AN AUTOPILOT – THE AP WILL WIN because those servos have a lot of torque. If it’s not doing what you want – especially vertically -, just disengage it and set the airplane up by hand.
    • The most common way to disconnect the autopilot is to press and release the red AP DISC button located on the control stick. An autopilot disconnect tone will sound.
      • Three other ways to disconnect the autopilot include:
        • Pressing the AP key on the KAP140
        • Operating the Electric Pitch Trim switch (located on the control stick)
        • Pulling the AP circuit breaker (know where it is!)

Here is good article talking about APs in general, definitely worth reading.

If the AP does something that doesn’t appear to make sense, don’t start wondering what and why it does that – just press the red AP DISC button (or use CWS) on the stick and hand-fly the plane.

Lastly, keeping INOP stickers away from the AP has high priority as flying XC and IFR without an AP is higher workload. Any squawk can take a long time to get resolved. A little patience and knowledge of the KAP140’s operation, limitations and idiosyncrasies are necessary.
There are a number of external factors and possible operational errors when it comes to APs in general, and this model in particular – please don’t squawk an AP issue before having a discussion with your MEI and/or MX leads.