Originally Posted by
GroundedDinosaur
The Helicopter wasn't landing at DCA, but, most likely would have the airports barometric setting in it's altimeter? If it was off by 0.2 inches, that would be about 200 ft?
I assume the altitude reading that the Altimeter in the aircraft displays in the cockpit is identical to the Transponded signal that ATC shows on it's screen? Is there a chance
that the Helicopter would have a different altimeter setting set? A new ATIS came out recently, or a pressure front was moving in?
I'm not sure this is the key point here. 100ft vertical separation at 150 Knots +/- equipment error in any safety plan is going to go wrong one day.
Although the route / approach crossed the main plan was surely to never let two aircraft on different courses /stages get even 10 times that close in passing . . which takes us back to the real issue