Final approach: suddenly AP switches off, plane out of control!!!!

[mozart 1]

I've made a frightening experience on two flights with the 744 (once the pax, once the cargo version):less than 10 nm before touchdown, the AP suddenly switched itself off. The was previously well established on the LOC and GS, speed was around 170, flaps correctly set, etc... to say that everything was "normal" as in my other 60 or so landings (most of them ILS autoland).Trying to go around by selecting HDG SEL and V/S mode to fly the pre-programmed GA, the autopilot first didn't switch on, and when it finally did it was only to switch itself off again after a few seconds. On or off, the plane neither respected the commanded HDG,nor the commanded V/S or target ALT. Autothrottle, too, was completely out of control. I tried stabilising the plane and landing it manually which was virtually impossible as some "forces" made it behave strangely and unexpectedly.There was nothing special about these two flights, and nothing they had in common (other than that the destination airports are in California).SOme more details:Flight 1:JAL B747-400, landing at KSFO Runway 24R, FlyTampa KSFO scenery, FSNav, ASV weather, full AIFLight 2:Cargolux B747-400F (RR engines), landing at KLAX 25L, Cloud 9 scenery, FSNav, ASv6 weather, full AI, Flight Keeper.What could have gone wrong here? What could have caused the autopilot to switch itself off?

[kmanning 12]

>I've made a frightening experience on two flights with the>744 (once the pax, once the cargo version):>>less than 10 nm before touchdown, the AP suddenly switched>itself off. The was previously well established on the LOC and>GS, speed was around 170, flaps correctly set, etc... to say>that everything was "normal" as in my other 60 or so landings>(most of them ILS autoland).>>Trying to go around by selecting HDG SEL and V/S mode to fly>the pre-programmed GA, the autopilot first didn't switch on,>and when it finally did it was only to switch itself off again>after a few seconds. On or off, the plane neither respected>the commanded HDG,nor the commanded V/S or target ALT.>Autothrottle, too, was completely out of control. I tried>stabilising the plane and landing it manually which was>virtually impossible as some "forces" made it behave strangely>and unexpectedly.>>There was nothing special about these two flights, and nothing>they had in common (other than that the destination airports>are in California).>>SOme more details:>>Flight 1:>JAL B747-400, landing at KSFO Runway 24R, FlyTampa KSFO>scenery, FSNav, ASV weather, full AI>>FLight 2:>Cargolux B747-400F (RR engines), landing at KLAX 25L, Cloud 9>scenery, FSNav, ASv6 weather, full AI, Flight Keeper.>>>What could have gone wrong here? What could have caused the>autopilot to switch itself off?Hi mozart,Don't forget to sign your name. Did you move or put any pressure on the yoke at the time the auto-pilot disconnected? This will cause the auto-pilot to disconnect. Also click on the subject "Auto-Land Disconnect." There were others that had this same issue. You might find what's causing the problem there.Ken.

[phoenixphire 50]

Do you have Avtivesky installed? If you do you are probably experiencing the jetwash of another aircraft. Turn off

[The Ginge 0]

I have had the same problem coming into San Francisco on 28R. At about 700ft, with the autopilot and Auto Throttle off, doing the visual approach the 744 suddenly pitches nose down quite violently. Manage to recover it and then when at about 200ft it does it again and I end up landing at a descent rate of about 1500 fpm!!!I have Active Sky 6 so will try again and turn the wake turbulence setting off. RegardsTom P

[Guest benhoffman]

I had a similar experience once onto 28L at SFO after 15hrs of flying from SYD on UAL895.The weather was pretty poor and the surface wind was something like 24020kt or someting like that; so I got down to about 2,000ft and WHAMO! all of a sudden the autopilot disconnects and starts screaming at me.I did a go around and am not sure if it was windshear or just an isolated case.Hasn't happened since then.

[The Ginge 0]

The weather at SFO was 260/15 G23 but it has also happend at other airports where the wind has not been strong at all. Autopilot off and then it pitches down suddenly. Tom P

[soldano 0]

It happened to me, but I always thought it was due to the circumstance of landing in some complex airports with high ATC traffic combined with bad weather which caused a severe hit to frame rate (less than 8 fps)In this condition, I think the PC cannot continue handling the calculations of the autolanding function.-Athlon 64 3700Gforce 6600 GT