Some of the activities at the Patuxent River Naval Air Station back in the days.
AIRBOYD - "Testport (1971) Naval Air Test Center, Pax River" (27 min)
AIRBOYD - "U.S. Naval Test Pilot School (1959)" (14 min)
The flight tests are not only for enlarging and establishing the safe flight envelope and characterizing the handling qualities such as spin recovery. Flight tests are also the source to the data in the flight manuals performance sections.
In case anyone is interested in getting deep into the details of flight testing there are few better resources that the USNTPS's flight test handbooks. You can get the gist of them even without the math. They can be found at the
USNTPS Alumni Association website.
Side note to the first video: The satellite based emergency transmitter system is probably related to the
Cospas-Sarsat system used by ELT (Emergency Locator Transmitter), EPIRB (Emergency Position-indicating Radio Beacon) and PLB (Personal Locator Beacon) emergency beacons. They are used in literally thousands of rescues every year.