Originally Posted by
WillowRun 6-3
(I'm imagining that military aviators may disagree insofar as it may be an article of faith as well as military regulation that the FAA is absolutely the one responsible party for civil controlled airspace, but as a legal point I think plaintiffs will attack it.)
Route 4 wasn't restricted to use by military helicopters, so it should be possible to argue the unsafe design point based purely on the FAA's own specification. As to expectations that the Army pilots should have flown the route to tighter tolerances, even a tolerance of plus zero would have been grossly unsafe on a procedural basis: altimeter errors alone would take up most of the 50-odd foot "separation", and variances in airliner approach slope angle the rest. Besides, "plus zero" is an impossible tolerance to achieve when maintaining an altitude or height. The only way of flying that route not above 200 feet on a "IFR-esque" procedural basis with an achievable tolerance would be to fly 150 feet plus or minus 50 feet, which would demand total focus on height keeping via radalt (it would be hopelessly unsafe to attempt to fly that low on barometric instruments).