Originally Posted by
BRDuBois
The plane descended on a 5 degree slope over several hundred feet. After hitting a 50-ish foot high embankment it stayed in the air another 380 feet. If the bank steadily increased it should have hit about 1500 feet from where it did. In a steadily increasing bank it should have stalled at about 63 degrees with some 20 degrees more to roll before it hit.
The CAB report records ground level as 650 feet above mean sea level and the top of the embankment as being 675 feet. The embankment was only 25 feet high in relation to the surrounding terrain. That makes a significant difference to how much of the wing made contact with the embankment. It also has a direct bearing on how much such a contact would modify the flight path and attitude of the aircraft. If the wingtip made contact approximately 12 feet below the top of the embankment, (halfway up), then the loss of the outer 12 feet of the right wing would be expected to further increase the bank angle as the aircraft flew on due to loss of lift.
I use the term "lift" with reference to the direction of aerodynamic forces acting on the wing, a lift vector, but not in the sense of sustaining flight.
The investigators stated that the power lines were severed at some right bank angle between 60° and 70°, although no evidence as to how they derived this angle is included in the report. But this angle combined with a loss of lift from the right wing would lead to the conclusion that the attitude indicator that was recovered with witness marks interpreted as a bank angle around 100° is most likely to be correct.
So the initial impact with the ground beyond the embankment must have been between 5° and 10° nose down with a bank angle to the right of 100°+. Impact forces broke away the nose section and undoubtably the majority of the right wing. That part of the sequence can be stated with some confidence.
At 150 knots or so, the damaged wing of the aircraft would be expected to hit the ground some 250 feet beyond the embankment if it were simply in free fall, as it effectively would be with wings orientated vertically. The nose section another 100 or so feet further on. This fits reasonably well with the 380 feet figure you mentioned as the primary impact point of the aircraft with the ground beyond the embankment.
There is evidence that the remainder of the fuselage and left wing pancaked to the ground in a level and upright position. The only way that this could happen is if the inertia of the left wing and engines rotated the fuselage around to face backwards as it broke away from the nose section.
There appears to be a sudden deviation in the course of the wreckage path after the nose of the aircraft hit the ground. A rotational force being developed by thrust from the left wing engines which were still producing power, together with inertial forces may have been responsible. Gyroscopic forces produced by the still rotating propellers on the left wing should not be neglected as a source of rotational and precession energy either.
I suggest that the rear of the fuselage and left wing therefore impacted the ground like a sycamore seed and continued to slide, rotate and break up before encountering the ditch which imparted a final pitch pole movement to the wing box and tail section, leaving them inverted.
That is to my mind the only sequence that makes sense. With one wing and the nose section missing, the remainder of the aircraft would fit between the trees.
Obviously this would all occur in a matter of a few seconds, but it does broadly fit with the witness testimony appearing as a somersault to some, a flat or spinning impact to others, and of course the final inverted position of the tail pointing in the direction of travel.
All of this does presuppose that the aircraft struck the ground in a bank that was at or beyond vertical. I submit that the evidence available supports that view.
Apologies if I have stolen the wording or contents of other contributers posts in compiling this possible sequence of events, but as this thread seems to be about establishing what happened during the final seconds of the flight, I thought it worthwhile to attempt a summary that fitted the information available.