Conflicting eyewitness accounts notwithstanding, Saturday’s tragic mid-air collision of a Piper Saratoga and a sightseeing Eurocopter over the west bank of the Hudson likely resulted from the Saratoga pilot’s desperate and ill-fated attempts to avoid a collision. As the news reports have indicated, the airspace over the Hudson from the surface to 1,200 feet above ground level is a congested “VFR” (visual flight rules) corridor carved out of the otherwise very busy and controlled Class B airspace enveloping, like an upside down wedding cake, New York City’s three major airports, JFK, Laguardia and Newark. Airplanes, helicopters and blimps are required to self announce on a common traffic advisory frequency, self separate from conflicting traffic and fly on the right side of the river (west bank southbound and east bank northbound). The VFR traffic is thus compressed laterally (by the controlled airspace boundaries defined by either bank of the river) and vertically (by the VFR corridor ceiling).

Both the plane and the helicopter were headed southbound along the west bank (NJ side).  Eyewitness reports confirm that the plane was behind (or north of) the helicopter. Although many eyewitnesses report that the plane was below and flew up into the helicopter, these witnesses are likely mistaken. It is easy to tell which one of the two aircraft was behind the other,  given that they were both traveling in the same direction. However, it is nearly impossible from the ground to tell which one was a few feet above or below the other.

Eyewitness accounts uniformly report that the Saratoga pilot engaged in a radical evasive maneuver—a steep bank turn to avoid the collision.  While many said the plane was below the helicopter and flew up into it, the evidence suggests otherwise. First, the dramatic photographs taken by the ferry passenger clearly show the right wing of the Saratoga entirely off the plane. This requires a powerful and explosive impact—one sufficient to tear off the wing and the underlying superstructure—the main wing spar, an airplane’s equivalent to a beam or girder. This suggests that the airplane’s right wing, while in the steep bank, made contact with the helicopter's main rotor blades, which sheared the wing and its spar off the Saratoga, and as well resulted in the rotor blades separating from the helicopter. Eyewitness accounts also report seeing the helicopter blades falling to the river separated from the body of the helicopter. In addition, all the photographs show the helicopter leading the way down, after the crash, suggesting of course that the plane was above the helicopter at impact. The Saratoga is a low wing plane—wings attached to the bottom of the fuselage—making it impossible for the pilot to see what is directly beneath him at any given instant.

From this evidence, the most likely scenario is this. Both the plane and the helicopter were travelling southbound along the west bank at the same altitude. It remains to be seen whether either was equipped with TCAS or one of the other light plane systems available for alerting pilots to conflicting traffic. Undoubtedly the plane was overtaking the helicopter, probably at a closure rate approaching 100 miles per hour, given that the helicopter was on a sightseeing mission and of course can hover. At a closure rate of 100 miles per hour, 150 feet of linear separation evaporates each second. So, if the Saratoga pilot visually picked up the helicopter when he was 450 feet behind him, he had a mere 3 seconds to react. If he almost instantly inputted a steep turn to the NJ side of the river, he likely would have been over the helicopter on knife edge—right wing down, left wing up—mere seconds later. Even if the plane were slightly higher than the helicopter when the turn was initiated, planes tend to lose altitude in a steep bank (unless the pilot hauls back on the yoke) for two reasons. First the plane picks up effective weight due to the centrifugal force imposed by carving a steep turn. Second, the lift, which acts opposite the wings, is deflected from the vertical plane (downward) while in straight and level flight, to the horizontal plane (sideways), when the plane is on knife edge (in 90 degrees of bank). Thus a steeply banking plane effectively weighs more and generates less lift acting opposite to gravity—so it sinks. Likely then the Saratoga dipped as it banked hard right, causing its right wing to hit the helicopter’s main rotor blades resulting in an unsurvivable crash for each. Doubtless a slew of non-pilot legislators will react shortly with abundant solutions.

Stephen B. Meister