Cruise was FL180 and during the later part of the flight, I had a nice descent going at about 1000 ft/m using the B1900D autopilot, monitoring it with the GNS530 VNAV function. At about 11,000 ft the plane began experiencing violent turbulence. That is pitching up and down and rolling right/left. My descent airspeed to that point had been about 220 KIAS. Pitot L/R on, but no icing equipment turned on. Nothing that I could do would stop the pitching and rolling. I tried enabling and disabling the AP, yaw damper, rudder boost, and reducing the airspeed to about 170 KIAS. The aircraft kept this behavior all the way to touchdown. SInce it was leg 2 of the Christmas 2017 flight, I fought to save it and finally got the bird on the ground at Memphis. Fortunately, what was reported as 200 over and a half mile, was more like 700 and 5 miles.
This happened once before in the Thranda Kodiak. I’ve spent a good deal of thought trying to troubleshoot what may or may not be a problem with my X-Plane 11 install. At first I thought that it might be an add-on, like XPRealistic, but checking I found that I am running a very limited number of plugins and scripts.
Now I’m thinking that it may have been icing. Remembering the old formula to subtract 3F/2C for every thousand feet of altitude, it’s very possible that I was experiencing icing, given the temps. Although the behavior of the aircraft is not what I would have expected in that it felt more like strong turbulence.
Does anyone know how X-Plane exhibits icing or has had the same turbulence upon descent?
Yes, I experienced something similar during my Christmas Island flight in Alaska. Wing icing eventually created major turbulence and my aircraft just dropped out of the sky in a matter of seconds. The cause for it was my wing anti-ice system failure.
Question for you pros. Given this typical icing equipment panel, from the C404 Titan in this case, what would be your SOP for entering suspected icing conditions? For example, last night I flew a leg from KMEM to KICT in the C404. Departing WX for KMEM was 1200 overcast, which basically continued until around 9k, when we broke out. Temps were 9.4 C at the surface.
Not shown in the screenshot, I turned on PITOT HEAT, STALL HEAT, ANTI-ICE ELECT and PROP ANTI-ICE. I did not switch on DE ICE LIGHT or SURFACE DE ICE. Was this the correct procedure, or should it all have been on?
I think it’s to do with the fact that ice may have been build up inside the system and can come loose. Although that’s more of a consideration for flying a small carburettor equipped aircraft as far as I am aware.
I think so. Pitot and Stall heat are always supposed to be on when flying. Electrical Anti-Ice and prop Anti-Ice are usually electrical systems(although props can have a chemical system too depending on age) that are supposed to be used in a preventive fashion. De-ice equipment is used to remove ice when confirmed on the surface in question.
A little Caveat Emptor, this might chance per aircraft or manufacturers whim.
Yeah, in training for my private in C152 and later the Cherokee 140, the downwind leg mantra when reaching mid field was carb heat on, throttle back to 1800 rpm,maintain altitude until 80 kts, then pitch to keep 80. We used carb heat year round in Georgia.
I picked up icing in XP10 once while doing a DME-arc in C90 and actually crashed. It kept requiring more and more power to maintain level flight and eventually I was at max power and and still losing altitude. By the time I figured out what was going on it was too late and nothing would get me a positive rate of climb. I think somewhere on the screen it eventually said icing suspected or something like that.