A very strange occurence happened to me over Germany whilst flying a Seneca V in very stable conditions ( strong high pressure).
I was at FL50 and had been in the cruise (155kts IAS) for about 20mins. All power indications reading normally VMC and Autopilot on (HDG ALT FD) . All very calm just waiting to be changed over to another radar unit when suddenly the a/c rolled sharply to the right to about 45 degrees AOB
. I immediately disengaged AP rolled wings level and pitched forward ( to reduce AOA in case it was a high speed stall). I also instantly checked engine T&Ps they were all reading normally. Then suddenly about 2 seconds later the a/c did the same thing
, rolled quickly right at which point I quickly rolled wings level. Visually checked flying surfaces all ok and controls felt fine. Nothing else abnormal and from then on perfectly normal flight. To me two possible causes.
1) There was a C-130 about 8nm in our 12 o clock same heading and altitude so we were effectively follow his track. I feel the there could have been wake turbulence from this that could have caused 2 wing drops. However, surely wake turbulence will decrease in altitude once it has developed so if the C-130 was at our level and 8nm away then wouldn't his wake turbulence be beneath us and so not effect us? Also all we had only 2 wing drops there was no small buffets, turbulence or disturbance in our flight condition prior and after the event.
2) On the previous leg we had problems with the AP which when put into a rate 1 turn would seem to rock the wings relatively slowly but definatley pronouced manner. Could this same glitch with the AP cause a sudden wing drop? What puzzles me with this possible cause is that AP was disconnected before the 2nd wing drop. It has been mentioned to me that the AP doesn't fully disengage immediately so may have been having some effect, but I'm not sure about this.
The a/c is been taking to maintence shortly and definately won't be used with passengers until the problem or cause is found (luckily no passengers on this leg). Would anyone else know what could have been the cause here or have had a similar occurence? Any help or advice would be greatly appreciated.
Regards,
Mooneyboy
