Originally Posted by
Lonewolf_50
What has that got to do with this event? They were not on an IFR flight plan.
Also, as an aside the term "altitude" is typically used in aviation.
(Yes, I know that DH for a precision approach is "decision height"...and HAT is shown on approach plates (Height Above Touchdown).
Thank you, I am a professional pilot so I do understand the difference in meaning. 'Height' is the correct term here as the route was defined with reference to the surface and the pilots were using the (badly named...) radalt as their height reference.
Why do I think the IFR ACS might be relevant? Because it specifies the accuracy the FAA requires of skilled pilots when separation is to be achieved by procedural means. The fact that the "designed" separation between the 33 approach slope and the top of Route 4 was less than the allowable error for skilled pilots could be used to rebut an allegation of negligent flying as the cause of the accident. The Army no doubt has its own standards document, but I'd be surprised if it was radically different. Building the argument off the FAA's own document forces the focus onto its route design and visual separation procedures.
As to why this might be relevant to VFR flying - is it your opinion that parameters should be flown more accurately in VFR than in IFR? In any case, I have now dug further into the ACS and the same tolerance is prescribed for
commercial VFR helicopter operations (see CH.VII.A.S8).