KAP 150 Altitude Preselect retrofit

[flyboy0681]

I'm having a GI-275 ADI installed in a few weeks and am wondering the following. I've always wanted the KAS-297 altitude preselect feature but knew that it required the King KEA-130A encoded altimeter, so I never pursued it.

So question, does the GI-275 emulate the same output as the KEA-130A, finally allowing me to purchase and have a KAS-297 installed? Better question, is retrofitting to an existing KAP 150 even possible or does the head unit itself require a certain built-in feature allowing the interface to take place?

 

 

[Greg_D]

I have wondered the same thing.  I don't think you'd need the KAS-297 with this setup though.  Isn't the altimeter and altitude pre-select built into the GI-275?

[carusoam]

There are a few displays that have included the altitude logic of the KAS...

hence the popularity of the KAS on the used market...

PP thoughts only, not an instrument guy...

Best regards,

-a-

[flyboy0681]

1 hour ago, Greg_D said:

I have wondered the same thing.  I don't think you'd need the KAS-297 with this setup though.  Isn't the altimeter and altitude pre-select built into the GI-275?

The only material that I can find on the subject states that the preselect only works with the Garmin GFC units.

[kortopates]

I believe the numbers will show it makes zero sense to install the KAS-297 unit when it will greatly subsidize the cost the cost for a new GFC-500 AP.  Not only will you have the acquisition and install cost you'll have to maintain those parts going forward - just move to a modern digital AP and get VNAV too; especially with only the KAP-150 with out flight director.

[Warren]

There are two notes in the installation manual.

1. If the Altitude encoder is replaced by the GI 275 to provide a baro-corrected altitude, the autopilot needs to be recalibrated to the new source.

2.  If the encoding altimeter is removed, and blind encoder is required to create the gray code output for autopilot.

[flyboy0681]

2 hours ago, kortopates said:

I believe the numbers will show it makes zero sense to install the KAS-297 unit when it will greatly subsidize the cost the cost for a new GFC-500 AP.  Not only will you have the acquisition and install cost you'll have to maintain those parts going forward - just move to a modern digital AP and get VNAV too; especially with only the KAP-150 with out flight director.

Your point is well taken, however, used KAS-297 units are dirt cheap now and can be had for less than $500. GFC-500's cost 10x that without installation. If a -297 could be installed then it would seem like a no brainer. The operative word being "if".

[flyboy0681]

2 hours ago, Warren said:

There are two notes in the installation manual.

1. If the Altitude encoder is replaced by the GI 275 to provide a baro-corrected altitude, the autopilot needs to be recalibrated to the new source.

2.  If the encoding altimeter is removed, and blind encoder is required to create the gray code output for autopilot.

Are you referring to the section of the -297 manual "KEA 130A/KAS 297 ALIGNMENT"?

[Warren]

It is outlined in the install manual.  This process involves making a test harness for Autopilot and then making various adjustments to the potentiometers in the autopilot.  It is a bit of a process. 

There is also a configuration table that outlines all the settings for the GI-275 based on the autopilot type.

[flyboy0681]

12 hours ago, Warren said:

It is outlined in the install manual.  This process involves making a test harness for Autopilot and then making various adjustments to the potentiometers in the autopilot.  It is a bit of a process. 

There is also a configuration table that outlines all the settings for the GI-275 based on the autopilot type.

Sounds like those upgrading to a GI-275 who already have a KAS-297 will need to go through these steps, no?

[Warren]

Yes.   Anyone with the king autopilots will need to go through this adjustment when they change guidance source for the autopilot.  This requirement applies to systems with and without the KAS-297.

[PTK]

After the new device driving the autopilot is replaced pitch and roll centering will sometimes need a slight readjustment. Also the installation requires verification of proper functionality of the autopilot prior to doing the upgrade.

[flyboy0681]

Based on what I've read here, it's more complicated than simply adding the control unit and firing it up. Thanks for the input guys.