An Overview of the KAP 140 Autopilot (Part I)

by HPA · October 24, 2011

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.

KAP 140 Autopilot

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.

ROL/VS Mode

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.

HDG/ALT Modes

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.

NAV/APCH Modes

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.

How it Started

One of my best friends in high school, (Doug Gray) was a private pilot. He offered to take me up for a flight in a 1967 Cessna 150, N6228S. We took off from Calhoun, Georgia, and he took me on a scenic tour of the area, I was hooked. I later found out that my English teacher, (Jan Haluska) was also a flight instructor and the school was offering a ground school course the next year, which he taught, along with flight training with the goal of becoming a private pilot. I managed to talk my dad into funding the training, at the time the total cost was right around $500. Cessna 150 rental rates where $12 an hour, and the 172 we used for cross country was $15 an hour including fuel.

Training Begins

It started August of 1977. The fall semester rolls around, and I am enrolled in ground school, and if memory serves me, we met twice a week. First came the paperwork for my student pilot certificate, which at the time was included with the 3rd class medical. I loved ground school, especially learning navigation, plotting courses on the sectional, again this was before iPads and GPS, so we did a lot of dead reckoning and VOR navigation for cross countries. At the end of the course, I made an 83% on the Private Pilot written exam, remember this was before we had the question-and-answer books that on future test I would consume before taking a written.

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Flying

The fun really began on August 22, 1977, it was my first flight. To my surprise we used the same Cessna 150, N6228S that my friend Doug Gray had taken me for a ride in. The Cessna 150 had a standard VFR instrument panel, with one NAV/COM, and one VOR CDI. No intercom, so no headset, at the time I didn’t know what I was missing. I didn’t get my first headset until I started my instrument training in 2003. I was a big guy, I was 6’ 4” and weighed 245 lbs. but I do not remember being uncomfortable in the 150 even with the instructor in the right seat.

First flight lasted .8 hours, and we accomplished orentation, shallow turns, stability, and effects of flight controls. Over the next few months we added steep 720’s, slow flight, stalls, turns around a point, S-turns, emergencies, landings, (short field, soft field and normal).

Learning

At this point I want to talk about a training experience that still stands out. We were close to solo and were practicing takeoffs and landings. Turning base to final Jan got very upset at the way I was cross controlling the aircraft. Cross control is when you are in, say a left turn, and use opposite rudder to line the nose up with the runway. So, he had me depart the pattern and head east to the practice area, and climbing up to 5500 feet MSL, he had me slow down to just above stalling speed, start a left shallow turn and add right rudder. As the airplane stalled I had the strangest sensation, no roller coaster has ever come close, instead of blue sky in the windscreen I was looking at brown ground, and as far as I could tell we were upside down, through the terror of the moment Jan talked me out of the spin, controls neutral, oposite rudder, pull slowly out of the dive. As we leveled off he asked me what altitude we were at, as I remember it was around 2,800 feet MSL. Then he asked me what would happen if I experenced this on base to final in the traffic pattern. The answer was obvious, I would be a pile of wreckage off the end of the runway with a very short-lived aviation career. Needless to say this cured my cross-control tendencies.

Another training event the sticks out in my mind was the first time we did takeoffs and landings at the High School runway. The runway was 1,500 feet long, not sure of the width, but it seems like we had about 5 feet on each side of the wheels when on the center line of the runway. Landing from the south you also had to go between a cutout in the trees to be able to stop in time on the runway. After getting confortable landing here every runway since seemed huge. I remember landing at Chattanooga (KCHA) on a night cross country and commenting to Jan, that I felt like I could of landed sideways on the runway, it felt that large.

Very soon after this I started wearing old shirts to all my flight lessons, the reason for this occurred on February 8, 1978. The lesson that day was stalls, takeoffs and Landing. As we were taxing back in Jan told me it was time for my first solo. I was very excited, and after some last minute advice from Jan, including watch for floating on landing the plane will be light with him not in the right seat, complete 3 takeoffs and landings to a full stop. It was a blast, and at the end of my shirt was shorter in the back because Jan cut the tail out of it signed and dated my solo [an aviation tradition]. Total flight time accumulated on the day of my solo was 18.1 hours. I was now officially a pilot with solo priveleges.

In my next article I start cross country training, when Jan decided that it would be best accomplished this in the 172. Checking out in N5970R was like moving into a 747, this started a love affair with one of my faviriote planes to date. Since this time I have flown over 900 hours in many different models of the 172 and feel like I am stepping into an old friend every time.

More about Randy here: https://www.flyhpa.com/team/randy-delong/

 

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