I haven't either...My ejoomacated guess is that either the air intake or the fuel delivery system was plugged, causing a lack of power in the #4 engine preventing sufficient altitude gain, and the pilot had aborted the mission thinking it could be cleared by the ground crew...One observer reported seeing smoke which could indicate an obstructed air intake...He is said to have made a wide turn in his RTB attempts which makes sense because it would enable minimum altitude loss...All I can do is guess, but we have pilots here, Billy Rightwing springs to mind, who may be able to add more...This is another of those times when I miss Dan's input......Ben