High Performance Aviation
Hands Off Flying, Part I
By Hank Gibson, CFI, CFII, MEI
How many pilots out there have uttered curses under their breath trying to work the KAP 140 autopilot? The KAP 140 is great when it does what a pilot wants it to do, but sometimes, getting it to cooperate is a pain. Even the most experienced pilots still have gripes with this particular autopilot. It just does not work sometimes. Hopefully, after these next two articles, pilots will not be tempted to tear the autopilot out and drop it out the window from 6,000 feet.
A Bit of History
As far as the author’s knowledge goes, Cessna began using the KAP 140 autopilot in their 172 Skyhawks in 1996 with the introduction of the R model. The 172R was the second fuel injected Skyhawk after the “popular” R172K XP, manufactured in the late ‘70s (www.172guide.com). It has also been used in many other airplanes for years, but the discussion here will just be about Cessnas.
The KAP 140 started in most R models as a single axis autopilot, having only heading control. It still utilized NAV mode and APCH mode, coupling to CDI number 1. Like all KAP 140s, when the autopilot was first activated, it started in ROL mode, basically acting as a wing leveler (sidenote: have any pilots actually ever utilized ROL mode?).
The dual axis autopilot is a little more useful. When set right, it controls altitude, has a built in altimeter, and its own static port. While flying an ILS approach, the autopilot controls everything but the rudder. It captures the glide slope and the localizer and flies the approach all the way down. Important note to all pilots: the autopilot will fly you into the ground, so it is very important to disconnect it before the approach minimums.
With the advent of the G1000, Cessna continued using the KAP 140. A problem arose because the autopilot was rigged to the turn coordinator in the steam gauge Skyhawks. How did Cessna remedy this? A turn coordinator was installed behind one of the Garmin Display Units that gave the autopilot information.
These days, Garmin has developed it’s own autopilot that is fully integrated into the G1000, so KAP 140 autopilots are not that popular anymore in the newer airplanes. There are still quite a few flying around, as well as quite a few pilots who get confused by them, so that is where I come in to help. We will start with the basic modes and next week, discuss some scenarios and what to do with the autopilot in each. One last note to mention: if the autopilot is not doing what it is told, the best thing to do is disconnect it. It becomes dangerous otherwise.
This is the default mode for the KAP 140. Whenever it is activated, it starts in ROL mode and vertical speed mode together (with the dual axis, which is what will be discussed here). ROL mode simply gets wing leveling information from the turn coordinator. It’s purpose is to keep the wings level. Vertical speed mode, just like it sounds, controls any climb or descent of the airplane. Using the UP and DWN buttons, the pilot can select either a climb or descent, and the desired rate.
These two modes can be selected separately from each other, but will be discussed together here. Heading mode (HDG) tracks the heading bug. Whatever the heading bug is set to, the autopilot will turn to fly that heading. It is always prudent for a pilot to make sure the heading bug is set properly before activating this particular mode.
In altitude (ALT) mode, the autopilot will hold the selected altitude. Pilot’s need to make sure the BARO altimeter is set correctly or the altitude the autopilot is holding will not match the altitude in the main altimeter. If everything is set properly and the autopilot is still not on altitude, pressing the UP or DWN buttons will cause the autopilot to adjust twenty feet.
These modes both couple with the HSI. In NAV mode, the autopilot will track whatever the CDI is set to, whether it be GPS, VOR, LOC, or ADF (if the airplane is equipped). In approach mode, the sensitivity of the autopilot is increased, so it holds to tighter tolerances. It also will track the glide slope on an ILS approach in APCH mode (as well as the glide slope on a WAAS approach, if equipped).
These are the basic modes of the KAP 140 autopilot. Next week, a few different scenarios will be presented and proper decisions will be discussed. Plus, we will finish talking about the other buttons on the autopilot and what they do. Remember, if ever the autopilot is not cooperating, disconnect it and hand fly the airplane.
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