Why does the flight path divert from the planned routes by cutting short the various waypoints? In the photo below, the path turns towards the next waypoint approxiamtely 5 NMs from the CADER intersect. When this happens on a decent, the autopilot has to rapidly readjust the decent rate that seems to have been calculated on the longer route (all the way to the waypoint) once the next waypoint becomes active in the FMS and sometimes there is an altitude elevation error message in the FMS because of this.

more photos of the same issue from the same flight.

Because the MD11 can not turn on a dime, what you are seeing is normal!

Each of these waypoints are "fly-by" type. In lateral NAV mode, the aircraft follows the path between them as smoothly as possible, taking "shortcuts" as you see here. What you'll find is if you manually reduce speed (i.e set speed to - say - 200 knots and right click the speed knob) then you'll see the magenta path passes much closer to each waypoint because the aircraft can make a tighter maneuver at slower speeds.As a side note, the approach path you have shown there is a little sharp. What is the airport you are landing at, and what runway / arrival procedures did you choose?

This particular case was KMEM (Memphis Int'l) Rnwy 18C. I was just doing a few departures and landings on this runway. At random, I entered a waypoint along the flight path some +/-10NM to the west then to a waypoint +/-15NM to the north (CADER) of the nearest waypoint for the approach to allow for some distance to adjust, since I understand the aircraft "can't turn on a dime".Thanks for your reply. Perhaps forcing the aircraft to slow down will correct the shorter path issue. I'll give it a try.

No problems Don, glad to assist. :( What will help also is to fly a flight path that doesn't involve such a 'sharp' turn in the first place. The procedure you're using here is probably not one used in real life (I say 'probably' because I don't fly into KMEM so I'm not 100% sure).The aircraft can fly it as you have it programmed, sure, but because it recalculates the lateral path during that big turn (and shortens the track distance you fly as a result), the vertical calculations which have determined your descent so far become invalid and you'll end up high every time. Not only that but at 245 knots, above the profile and less than 10nm from the runway you're setting yourself up for a heck of an approach, even experienced MD11 pilots will find that a handful!Really you want to try and set up a turn onto final that involves less than a 90 degree heading change and ideally about 30 degrees. So looking at your first picture think of a waypoint out in front of you that would make your flight path a rectangle shape, with a nice rounded turn at the end of your downwind leg.Combine that with the speed control technique I mentioned above and you should find the aircraft FAR more controllable on final approach.

No problems Don, glad to assist. :( What will help also is to fly a flight path that doesn't involve such a 'sharp' turn in the first place. The procedure you're using here is probably not one used in real life (I say 'probably' because I don't fly into KMEM so I'm not 100% sure).The aircraft can fly it as you have it programmed, sure, but because it recalculates the lateral path during that big turn (and shortens the track distance you fly as a result), the vertical calculations which have determined your descent so far become invalid and you'll end up high every time. Not only that but at 245 knots, above the profile and less than 10nm from the runway you're setting yourself up for a heck of an approach, even experienced MD11 pilots will find that a handful!Really you want to try and set up a turn onto final that involves less than a 90 degree heading change and ideally about 30 degrees. So looking at your first picture think of a waypoint out in front of you that would make your flight path a rectangle shape, with a nice rounded turn at the end of your downwind leg.

Thanks, however take a look at this:I was flying yesterday from KIAH to KMEM on the flight path suggested by FlightAware (ELD3 ELD TAMMY3) with southern winds for the approach. I had to plan for almost this exact landing. Knowing what I know now, I did change my speeds requirements in the FMS to 250 kts crossing TAMMY, 230kts crossing JAMEA and 210kts crossing TWIKL. Additionally, I forced the altitude at ACALE to be at 5,000 feet (I believe the FMS calcuated elevation for ACALE was over 8,000 feet), which helped when the decent path recalculated upon cutting short the planned route similar to the situation in the prevous post. Even at the reduced speeds, it still cut short the ACALE intersect by at least 5 NMs, similar to the photo in the previous post.

Flying the Tammy Arrival, you should fly the arrival to ACALE. From ACALE, your next waypoint should be LAURI which is the first waypoint of your approach according to your screenshots. At or before ACALE, in real life a controller would give you vectors to approach the runway. Since you don't have a controllers input, and the MD-11 doesn't know that, you have to wing it. Just as you would do in real life if the controller gave you a vector, you would engage HDG mode as opposed to NAV. In practice, what I do is maintain my vertical speed until I reach approach altitude, then make the turn for the approach using the magenta line. Using this method has the aircraft stabilized by the time that you hit the glide slope. Keep in mind according to the chart, you should be on track with the runway approximately 17 miles out. Since you know this from the chart, you can create a waypoint in the FMC to position your aircraft into position.

Hi Don,A couple of points on this procedure. My apologies if you already knew the following.The arrow at ACALE with the heading of 359 deg means that after passing that point you could expect vectors and altitudes from ATC to intercept the ILS. Obviously the ATC in FSX isn't exactly world class, (I'm hoping that 'Simair' from the REX guys is an ATC addon myself!) so in our case we would switch to heading select mode at ACALE, fly heading 359, then abeam (or slightly past abeam) of LAURI you would turn right 90 degrees, then turn right 60 degrees to intercept the ILS. I'm not sure what the ILS intercept alitude is there, but you'd want to be at that altitude as you made the base turn.As for speed, you might be slowing down a little early there, but it would cause no harm. I'd aim to be making the base turn at 220 knots, then intercepting the ILS at about 200-210 knots, then reducing to Vapp from there.