Sorry, we're a bit slow responding.
I flew this system 5 days a week for three years in one of the most hostile IFR environments - the LAX Class B - from CCB to HHR and back. While the HHR approach was a localizer, having the GPS map display and DME type information made approaches much safer and less stressful. One 'June Gloom" period resulted in 21 consecutive days of IFR approaches into HHR. CCB has a GSP approach overlaid on the VOR approach and the KLN-89B made getting home much easier and far more accurate than the VOR method. The only reason we removed the KLN-89B was the total restoration of our C150B and the addition of color displays to the panel.
The other posts are correct. The KLN-89B (and all IFR approved GPS units) needs feedback from the CDI to function in the OBS approach modes. The KI-209A has the needed circuits and can switch from GPS to VOR indication with an added switch.
IFR approval needs annunciation of Armed, Active and message which the MD-41 provides. It's a fairly simple unit with numerous input / output pins to switch VOR / GPS functions and provide the necessary status indications.
The package includes a new KLN-89B installation tray, pins and a wiring harness already built up for the MD-41 interface. A CDI connector and interface to the altitude encoder is needed.
It's not quite a "turn-key" installation, but very close.
