Corporate pilot reported that while on an RNAV approach; the universal uns-1E FMA dropped the IAF an...

Narrative:

Enroute from ZZZ to apf; we were cleared direct to ugyow to descend to 2;100 feet; and we were cleared for the RNAV 23 approach at apf. About 4 NM from ugyow; the FMS dropped ugyow from our route completely; and the final approach course with a line to infinity was redrawn on our mfd with ofdoy still in view. The FMS commanded a turn to intercept the final approach course at a 45 degree angle; inside ofdoy.here's what's so strange about this. We had the same anomaly happen to us on the same routing several months ago. I was ready for it today; but the airplane still turned and there was a minute of confusion and discussion because our next fix ugyow was no longer in view; and dropped from the FMS. We had no guidance anymore to ugyow. Having had this happen twice now; I have to say with confidence; there is an issue with the universal uns-1E FMS we have on board to provide this guidance. I realize the turns necessary to get us on the final approach course are significant in this procedure; but the FMS should not drop the IAF fix from view and redraw the final approach course as it is doing. Someone at universal and the FAA need to look into this; and they need to publish that this procedure can't be used when coming from the southwest so that others don't have this bad experience. There was no conflict with traffic; but the controller got a little excited when we first made the turn; and he canceled our approach clearance; and turned out back out to the northeast and he gave us radar vectors to the final approach course; which worked out perfectly. My copilot on this flight had been an instructor on the aircraft X at [the] simulator training center for years; and he agreed the FMS shouldn't have done that and its guidance is wrong when this happens. I will contact universal to discuss it with them; and I plan to try this approach in the simulator when I go back for recurrent training.

Original NASA ASRS Text

Title: Corporate pilot reported that while on an RNAV approach; the Universal UNS-1E FMA dropped the IAF and redrew the final approach course. Reporter stated this had happened previously on the same routing.

Narrative: Enroute from ZZZ to APF; we were cleared direct to UGYOW to descend to 2;100 feet; and we were cleared for the RNAV 23 approach at APF. About 4 NM from UGYOW; the FMS dropped UGYOW from our route completely; and the final approach course with a line to infinity was redrawn on our MFD with OFDOY still in view. The FMS commanded a turn to intercept the final approach course at a 45 degree angle; inside OFDOY.Here's what's so strange about this. We had the same anomaly happen to us on the same routing several months ago. I was ready for it today; but the airplane still turned and there was a minute of confusion and discussion because our next fix UGYOW was no longer in view; and dropped from the FMS. We had no guidance anymore to UGYOW. Having had this happen twice now; I have to say with confidence; there is an issue with the Universal UNS-1E FMS we have on board to provide this guidance. I realize the turns necessary to get us on the final approach course are significant in this procedure; but the FMS should not drop the IAF fix from view and redraw the final approach course as it is doing. Someone at Universal and the FAA need to look into this; and they need to publish that this procedure can't be used when coming from the SW so that others don't have this bad experience. There was no conflict with traffic; but the controller got a little excited when we first made the turn; and he canceled our approach clearance; and turned out back out to the NE and he gave us radar vectors to the final approach course; which worked out perfectly. My copilot on this flight had been an instructor on the Aircraft X at [the] simulator training center for years; and he agreed the FMS shouldn't have done that and its guidance is wrong when this happens. I will contact Universal to discuss it with them; and I plan to try this approach in the simulator when I go back for recurrent training.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1745378
Time
Date	202006
Local Time Of Day	0601-1200
Place
Locale Reference	APF.Airport
State Reference	FL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Light Transport
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Flight Engineer Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 3 Flight Crew Total 17700 Flight Crew Type 240
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Clearance Deviation - Track / Heading All Types

Corporate pilot reported that while on an RNAV approach; the universal uns-1E FMA dropped the IAF and redrew the final approach course. Reporter stated this had happened previously on the same routing.