The Garmin GI275 may become relevant as a KI256 replacement.
The AI can be the root cause for that “Bonanza” effect, i.e. the constant up and down when on Autopilot. There’s a very slow up and down, of +/- 50-200ft, which usually is a worn out trim servo. The shorter up and down, high frequency, can have many reasons.
In our case, it turns out it was the Attitude Indicator. The KFC150’s pitch is connect to it, and if it wears down, it apparently gives changing signals.
Just for info.
It was the AI allright. Worn bearings.
The pitch oscillation issue is complex. Fundamentally the cause is either a dead band (hysteresis) in the control loop, or excessive proportional gain.
The causes can be
Some of the above happen only in certain altitude bands, and only in certain w&b configurations relative to the envelope.
Oh dear – new FAA AD on the KI300
https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/AA5F59E4A5CFCD91862585D3000C5F0C?OpenDocument
Whoops…
I am amazed they sold 54! However this does show how keen people are to replace the KI256.
A google on this topic does find rather a lot of reports in the US.
Uups – so basically it doesn’t work and aircraft equipped with it are grounded for IFR and night operations for an indefinite time.
That’s gonna be expensive for the owners…
Not the first time… the KFD840 (some notes here) also lost its IFR certification. It got dropped soon afterwards. That was ~ 10 years ago. HBK stopped development of own products about 17 years ago; all later stuff was done by outside contractors, or bought-in and rebadged.
Makes the gripes about the Aspen RSM module seem almost petty…
There is a vast difference in numbers sold. Aspen has been a very popular product for years. I haven’t seen their accounts but looking at some of their factory videos I reckon they have been – in the good times – pushing out 100+ EFD boxes per month. The KI300 has sold poorly – same as all HBK products they have brought out since about 2003. So the report of 54 failures is amazing; it could be close to 100% of the number sold.
