Originally Posted by
aterpster
It was part of the design and certification of an unusual airplane.
A type-specific suspension of one of the Rules of the Air wasn't part of the certification process.
IMC = collision avoidance is the responsibioity of the controller, not the pilot. Ergo the pilot is not "required" to maintain a lookout, indeed as he is assumed to be IMC at all times by IFR rules he clearly
cannot do so. Its nice if he can, and obviously a good idea to do so when possible, but it ain't a requirement because it can't be.
If it were so then Concorde could not have been certificated to fly with the heatshield up.