DIR to RNAV point directs a 90 degree turn when the waypoint is straight ahead?

[Lauramks2]

I was setting up for the RNAV Y Rwy 20R at KSNA (John Wayne).  As I got close I went used the DIR button to HUKEM (a point on the approach) which was basically straight ahead of me. The PFD showed the magenta line on a heading of 197 (the final approach course) but Hukem was straight ahead of me. I flipped it into heading mode based on the MFD plan view and waited until I got close before manually turning to final and then engaging the autopilot. Attached is a screenshot of the aircraft about 5 miles prior to final intercept. For some reason I have the hardest time with the approaches to KSNA. Is this because HUKEM is not an IAF? 

I fly into KPSP all the time and intercept at a midpoint on the approach. It seems to work in other areas. 

 

This is the only airport where the FMS goes bonkers. I flew the ILS Rwy 20R yesterday and when I intercepted final at SNAKE it started into a right 360. Since I wasn't on Pilotedge, I waited to see what it would do and it just kept flying in circles until I manually intercepted final and stepped to the then waypoint HUKEM. 

[Pils]

On 5/4/2025 at 10:26 PM, Lauramks2 said:

As I got close I went used the DIR button to HUKEM (a point on the approach) which was basically straight ahead of me.

What was your flight plan at the time? Looks like it was at least FRETS?

On 5/4/2025 at 10:26 PM, Lauramks2 said:

I flew the ILS Rwy 20R yesterday and when I intercepted final at SNAKE it started into a right 360.

This sounds like a false localizer capture, were you intercepting the approach course from an angle larger than 30 degrees?

[Lauramks2]

FMS 1 on the PFD shows Hukem, the fms controller shows Hukem in pink. I didn't have the ppos showing  as it was on another screen not recorded but on the COPILOT MFD  showed me that Hukem was straight ahead. One of the tricks I have found going from PSP to SNA is that there is a coastal mountain range just before the approach. Going from Frets which is on the TEC route (Deway frets kayoh8) direct to Hukem takes me near the 5808 ft peak on the coastal range. If you look on the FMS is shows a 4.7 degree dive to Hukem which also gives me the "no vpath" warning. After analyzing my recent flights I realize that the most prudent method would be requesting direct SAGER (IAF). That takes me parallel to the coastal mountains and gives me a longer shot getting lined up on the approach. Doing this also takes me down the valley so I can get down to approach altitudes much easier. Not the shortest route but the most prudent. 

You may be correct on the false ILS and the 360 degree turns. The day I was flying, I was not on Pilotedge so I could mess around and see what happened. I was intercepting with about 80 degrees cut and as I got near SAGER it started a turn to the right instead of left toward the airport. I thought maybe it was going to take me into holding to line up but it just started a 360. I went around twice just because I wanted to see if it would give me a warning or some indication of what it was doing. I didn't see anything so I went to HDG mode and lined myself up then engaged the autopilot and all was well. 

If I approach final at greater than 30 degrees, will it turn short, go into a hold, or do nothing? 

 

Thanks for your thoughts. 

[Pils]

13 hours ago, Lauramks2 said:

If I approach final at greater than 30 degrees, will it turn short, go into a hold, or do nothing? 

It'll chase the false localizer, behavior of which is a little unpredictable, but most times I've seen people report it'll do 360s repeatedly, maybe with some course reversals mixed in. It's not a pre-programmed response, it's naturally coming from the plane's simulation of the localizer radio signal propagation. You should guide yourself in HDG or LNAV onto an intercept of 30 degrees or less, or better yet, all the way onto the final approach course. Unlike other aircraft, because ATC says "cleared approach" doesn't mean you must/should arm APPR and/or switch to "green needles" manually. It's ok to use the FMS as long as you've switched to using the localizer passing the FAF (or if ATC explicitly say to use the localizer before that, like they often do at LAX, for example). Some more information from irl Challenger pilot and one of our consultants: