It is for measuring what the air is doing (speed/angle) before that air is affected by the aircraft. It is something that's almost every test aircraft has. For

It is for measuring what the air is doing (speed/angle) before that air is affected by the aircraft. It is something that's almost every test aircraft has. For example, https://en.wikipedia.org/wiki/List_of_X-planes#/media/File:Grumman-X29-InFlight.jpg https://en.wikipedia.org/wiki/List_of_X-planes#/media/File:G... Once this data is gathered during the test program, the production aircraft can use less obvious sensors to measure what is going on.