The KAP 150 Auto-Pilot is a 2-axis auto-pilot without a flight director that is no longer in production. Manuals for the auto-pilot are available on the Internet (it’s part of the family of KFC 150, KAP 150 and KAP 100 auto-pilots all in the same manual).
It can be connected to a KG107 (DG) and KI 204 (CDI) or a KI525A (HSI). We’re going to assume that the connection is to a KI525A HSI for the rest of these notes.
In some installations the A/P may be attached to a KA 185 mode annunciator – we will assume that such an annunciator is not installed in these notes.
POWER ON AND SELF-TEST
When power is applied to the KAP 150 the TRIM light will be illuminated indicating that the system self-test should be initiated. The test must be completed before the A/P can be engaged. To perform the test momentarily push the TEST button.
You can perform a test of the systems operation on the ground.
- Select AP ENG. The A/P will engage in wings-level, pitch hold mode. Move the control wheel to ensure that you can over-power the A/P control servos.
- Center the HEADING BUG and select HDG mode. Move the HEADING BUG left, ensure the control wheel banks left, move it right, ensure the control wheel banks left.
- Us the DN/UP rocker switch to ensure that the control wheel pitches forward or backwards and that the electric trim runs in the appropriate direction. You can test this with and without ALT selected.
- Disconnect the A/P. You may choose to engage and dis-engage the A/P using as many different methods as you prefer, two common checks are to dis-engage via the A/P DISC button and dis-engage via engaging manual trim.
Note that AP ENG selects the default A/P mode, with no other annunciations the A/P is flying the plane wings-level, pitch hold.
This not a comprehensive A/P tutorial, so most of the normal mode operation is assumed.
In pitch hold mode (no ALT or GS annunciator) the DN/UP rocker switch will alter the pitch mode. You can establish a pitch angle and the A/P will maintain that angle. On long climbs or descents be aware that as performance decreases or increases a pitch angle selected at one altitude may lead to an unsafe airspeed at other altitudes (too slow in climb, too fast in descent).
With ALT annunciated the DN/UP rocker switch can be held in position and will establish up to a 500 fpm climb or descent. When the rocker switch is released the aircraft will hold the current altitude.
Generally speaking the system will react as you expect, you select an intercept heading in HDG mode, select NAV or APR and annunciator will flash and the A/P will follow the HDG guidance until intercept. There is a quirk in the KG107 installation, if the heading bug is set to the required course (OBS) within 5 seconds the A/P will establish it’s own 45 degree intercept. This is rarely what you want.
The A/P will follow a glideslope as long as the glideslope is captured from below and the A/P is in APR mode. This is true for any glideslope annunciation, ILS, VNAV or LPV (to be confirmed).
Control Wheel Steering (CWS) is provided to temporarily disconnect the A/P while the pilot makes adjustments to aircraft attitude directly, when the button is released the A/P re-engages. So CWS can be used to make pitch adjustments in pitch hold mode, heading adjustments in wings level mode and altitude adjustments in ALT mode.
There is generally speaking only one really dangerous active A/P failure, and that is when the A/P sets elevator trim to a significantly out of trim position. This can occur through A/P failure or more commonly by the pilot pushing or pulling the control wheel while the A/P is engaged (or trying to apply manual trim) attempting to control pitch (in ALL cases when the KAP 150 is engaged the A/P is trying to control pitch).
The A/P does not “know” the pilot is manipulating the control wheel, all it knows is that the aircraft is not responding as desired, so the A/P will run the trim AGAINST the pilot’s inputs and, at some point, either the A/P will disconnect or the pilot may disconnect the A/P and the pilot will be left to fly a significantly out-of-trim aircraft. This can be disconcerting in VFR, and downright dangerous in IMC.
DO NOT MANIPULATE THE CONTROL WHEEL WITH THE A/P ENGAGED. Either you are flying the plane or the A/P is flying the plane – but can’t both have a go at the same time.
There are possible scenarios where the A/P could place the aircraft in an out-of-trim situation, but most scenarios are pilot induced.
Because the A/P may fail and you may need to dis-connect it in an emergency be familiar with ALL the ways to disconnect the A/P. These will include:
- A/P DISC on control wheel
- Control Wheel Steering (CWS) on control wheel
- Electric Trim Operation
- AP ENG button on A/P control unit
- A/P Circuit Breaker(s)
- Electric Trim Switch
- Radio Master
- Aircraft Master
AUTO-PILOT CHECKOUT FLIGHT
An A/P checkout flight should consist of the following activities.
- Review of the dis-connect options.
- Power up, self-test and ground test.
- Wings-level and pitch hold mode on climb-out including pitch adjustment using the DN/UP rocker switch and CWS and heading adjustments using the CWS.
- HDG mode and turns.
- ALT hold mode including altitude changes using the DN/UP rocker switch and CWS.
- Intercept and tracking of courses using NAV mode.
- Non-precision approach using ALT mode and A/P commanded altitude changes.
- Precision approach using GS mode.