In various airports (e.x EDDM, LOWW, EDDH, EGKK, LGAV, etc) during the final approach, I have turned on APP, the plane is configured for landing, the GS comes alive and is captured, the plane starts descending on GS pitch mode (single CH) and after a while, unexpectedly, the plane starts twisting, banking to the left and then to the right, struggling to maintain the path.
I have tried with CMD A only. With both CMD A & CMD B, but it seems not play a role. Even if I disengage the A/P, it is very difficult to control the aircraft manually, it keeps having the tendency to bank to both sides in a consecutive way, making landing very very difficult, even impossible.
Any ideas? Am I doing something wrong?
I use the TM TCA yoke and the TM rudder pedals, and the Tobii eye tracker.
Dimitris, check if you have wake turbulence off. In the latest updates, this effect seems to have been strengthened to an unrealistic degree. If this does not solve the issue, contact our support team so they can check some other things for you.
What is your speed? Are you maintaining Vref 30 plus 5 knots as a minimum approach speed? (With 30 flaps, which is the normal landing setting on the 737.)
If the wind is higher you might have to add 1/2 half of the wind plus all of the gusts (above the steady wind). The maximum total wind correction you can apply is 20 knots above Vref. (If the wind and gusts are still higher, you would only add 20 knots.)
Example 1: Wind is 12 knots.( steady) Your wind correction would be Vref plus 6 knots ( I.e. half the wind speed)
Example 2: Wind is 12 knots gusting 20. Your wind correction would be 6 knots plus 8 knots.(the 8 knots are above the 12 knots of steady wind.) Total wind correction 14 knots above Vref.
Example 3: Wind is 30 gusting 50. Your correction would be 20 knots above Vref.
Note: During the landing itself you would ideally reduce the speed so you touch down with Vref. Otherwise you might touch down with the nose first, which is an absolute no no.
BTW, once you have selected APP to fly an ILS approach, the IAS/MACH window on the MCP will no longer be blank and you will have to dial in your required approach speed yourself! Maybe that was the reason that your speed was off on approach?
Flaps 40 is normally not used on the 737 except for very short runways. That may have been your issue, because flaps 40 create a lot more drag. The difference in approach speed between flaps 40 and flaps 30 is only about 4 knots, but the increased drag requires much more power, which creates more noise and increases fuel consumption.
As for configuring, try to join the localizer with about 200 knots and set flaps 1. Then select flaps 5 (skip flaps 2) and reduce to about 170. When the glideslope comes alive (i.e. starts moving) lower the landing gear and select flaps 15. (Again skip flaps 10) At this point speed should be about 160. Then flaps 25 and finally flaps 30. Reduce speed to Vref 30 with wind correction.
CMD B is used for autoland together with CMD A. However current 737NG pilots would be more qualified to comment on this as I only flew the 737-200 and the 737-400 series and never did an autoland IRL.
Unfortunately again the same phenomenon. Landing at EDDF, rwy25r, armed APP, captured VOR/LOC, when the GS came alive FLAPS1, then FLAPS 5, when the diamond near the centreline FLAPS 15/GearDown, captured the GS, started descent, Armed the CMB, FLAPS30 plus 2 (4 knots wind) and suddenly the plane started banking on the right and then on the left, losing completely the configuration! I had to disengage the AP to avoid ruin my flight and fortunately managed to land (a really bad and nervous landing).
Good luck! You may have noticed that I forgot to turn off the autobrakes after take off when doing these screenshots. My bad! I caught it before landing though.
P.S. If the approach speed in my example seems low, then it is because I used a 737-700 at low weight for this example. A loaded 737-800 will have quite higher Vref speed.
P.P.S. Why did you try to use CMD B? Were you trying an autoland? Try to land manually by disconnecting the autopliot and autothrottle before landing. It will make you a better pilot eventually.
