TBM 930 AP in APR mode doesn’t hit RWY center line - but C172 (non G1000) does

There has been quite some discussion here concerning the „ILS approaches don‘t line up with RWY“ issue.

I did some comparison flights with TBM 930 (G3000) and C172 with Bendix AP 140 (non G1000) at different airports. These flights have been performed under identical procedural conditions for ILS/LOC approaches using the APR mode of both AP‘s.

I found that only the TBM 930 doesn‘t arrive at center line of the RWY, but the C172 does.

The C172 touches down precisely on RWY center line just a little after the threshold, as it should be. For test purpose I didn’t switch off AP until the landing was fully completed without controlling flare. This means the C172 supports even auto landing as required for e.g. ILS CAT III /b/c approaches - which sure is neither possible nor legal in RL.

My initial conclusion: The „ILS APR doesn’t line up with RWY“ issue is not bad NAV aid programming but buggy functionality of the AP of the TBM 930 - and maybe other planes. It seems to me as if actually only the more basic Bendix KAP 140 is usable for precise ILS approaches. But I haven’t tested the AP of the big jets yet.

This has nothing to do with autoland. (there’s only CAT IIIa and b IRL)
Every AP will simply follow the ILS until it hits the runway IRL either, or more precisely down to ~20ft.
If the 172 touches down shortly after the threshold it apparently doesn’t follow the GS exactly because in this case it would cross the threshold at 50ft and touch down 1000ft after passing the threshold.

I’m not experiencing the TBM touching down off-center. Make sure that you always start the flight from the main menu.

I’ve noticed numerous times that the more often you slew to an approach position after an ILS approach, the greater the inaccuracy during the succeeding approaches.

Please learn, that I don’t want to cover details of CAT/x approaches and auto land here. Your are right with your comments, which I know well from my own RL experiences.
It’s only about what the Sim does here and whether it does it right. If your TBM touches down precisely it is worth to be mentioned here. I’m going to check your comment about "the more often you slew to an approach position . . . " and the the RWY center line inaccuracy. I wonder if this is true but it well could be, because there are other mysteries with MSFS2020 too.

Just to comment on CAT III “c”. This categorie is meant for DH “0” and RVR “0”. Under these, more theoretical conditions, an “auto land” procedure would be required. To my knowledge there are only very few airports worldwide which meet the equipment requirements for this categorie - but even so, most of them do not allow a true auto land . . . but
. . . but from own RL experiences I can say that ILS approaches have been done with an EMB 120 under conditions where I barely could drive home because I didn’t see the street 5 m ahead. It was from an airport with CAT III/a !

Knowing all this it sure is more than a miracle that the FS20 C172 did a perfect autoland - that’s all I want to mention.

FYI, CAT IIIa and b already require autoland since the DH can be 0ft. (HGS exception)

CAT IIIc requires autotaxi and I’m not aware of any airport which presently supports this.

No 172 can perform an autoland, not even in the sim!
If there’s no flare and no automatic power reduction it’s not an autoland!

It’s no miracle if your 172 slams unflared at a constant speed into the runway.

What is a true autoland?

No 172 can perform an autoland, not even in the sim!
If there’s no flare and no automatic power reduction it’s not an autoland!

How can you say this? Have you tried it? I did more than five autolandings with the C172 (non G1000).
Without controlling flare! Power setting at IM was to have 85 kts at touch down. After (!) complete touch down power was set to idle, all landings were almost soft landings.
I did it at the following airports: RWY 05 LFST, RWY 15 EDDH, RWY 24 EDLW, RWY 23 EDDL, RWY 26L EDDP. Wheather was set to very bad conditions but no wind.

It seems we have not only different opinions but different software too? You don’t believe my C172 auto land and I doubt your TBM ILS APPR at center line.

I suggest to test my findings before your doubt it and I’ll test your assertions.

No need to try.
Did you read the requirements of what an aircraft has to perform during an autoland?
Did the 172 AP actively flare by pulling back on the yoke? No.
Did the power automatically reduce to idle prior or at the flare? No.
Which means no autoland occured.

The correct approach speed for a 172 is 61-65kts, which means you were at least 20kts too fast.
85kts is already the flap limit speed!
The pitch attitude at this high speed is nose down, which means the 172 will touchdown nosewheel first, a no-go.

Just for fun I tried your ‘autoland’ and the only reason why the bounce (due to the nosewheel first touchdown) wasn’t excessive is, that the sinkrate reduced in ground effect due to the excessive speed.

edit: concerning the TBM.
Make sure that rudder trim is correct for the approach and not in the takeoff position.

No flaps - with flaps the attitude is nose down. And, no flaps allow 80 kts approach speed in this special case with no RWY sight. 80 kts give a little sinkrate which has a good safety margin, and here a soft touch down with nose wheel friendly landing. I have logged more than 200 hour on a real C172 (D-EOMC). I used to extend flaps only if the RWY was shorter than say 400 m, so the approach speed has to be as low as possible depending on the actual load.

Just for fun I tried your ‘autoland’ and the only reason why the bounce (due to the nosewheel first touchdown) wasn’t excessive is, that the sinkrate reduced in ground effect due to the excessive speed.

Just for fun I made this video.

No flaps, no pulling back the yoke, power back just before visual touch down in order to let the bird auto flare - because it’s a real / unreal auto landing.

Please remember we have been discussing here the “ILS APR is off center line” issue, not any auto land details. And please read the headline of my post. The video proofs that the Bendix AP 140 of the C172 works well - nothing less, nothing more.

From my side no further comments here.