By definition, concrete evidence of a 'black' programme isn't going to be there. So using the absence of that is going to prove nothing.
As is often said, "Absence of evidence is not evidence of absence".
From a technical perspective, there's lots that is feasible. For example, Google "The Quiet One" OH-6 from the Vietnam era. See also RAH-66 Comanche for other LO.
Last edited by hoodie; 26th Jul 2019 at 22:52.