When the DC-8 Went Supersonic (2011)
airspacemag.com
airspacemag.com
There was a 747-SP that went supersonic by accident and was only saved by the crew deploying the landing gear to slow the plane down. He amount of damage was non trivial.
Someone will probably jump all over the critics of Douglas and point out Boeing’s Tex Johnson’s barrel row. 1) that was not endorsed by the company and 2) was a neutral G maneuver. 3) the company appropriately freaked and told him never to do that again.
We have occupational safety and standards operating procedures for a reason.
It would warrant criticism if the pilot tried it without informing the crew prior to takeoff. All participants entered into the activity with an understanding that they were risking their lives.
These people did it because they enjoyed the challenge, not to score points with corporate overlords or jockey for a raise and a promotion. The marketing angle was simply to provide cost justification and demonstrate that a perceptible reward would be earned with the risk undertaken.
If it where in the context of understanding the plane's behavior at trans-sonic speeds, I can understand it, but that is not really given as a justification.
You're mixing up problems that are completely irrelevant to the issue. Fatigue is only an issue in high load cycles (typically over 10^6) which means that it becomes a problem only after years of significant commercial operations.
Running a prototype is, obviously, not the case.
Moreover, structures designed to meet fatigue requirements are designed so that ultimate load is far higher than operational loads (over 5 or 10 times), and ultimate loads are covered by their own design scenario.
Fatigue and ultimate loads only cause problems when aged structures (i.e., planes that were well used and reaching their design life) are subjected to loads close to their ultimate load. That may lead structures to fail when subjected to loads that, although higher than typical operational loads, are far from the expected limit strength.
Here's an example of a retired C130 being used in firefighting missions that gets its wings to break off mid-flight.
https://www.youtube.com/watch?v=PK49QALNj-0
Running a prototype is, obviously, not the case.
It looks like some of CP's stretched DC-8s lived on into the 90s, albeit with other airlines.
Buffeting occurs when the soundwaves of the noise of the craft and its motion directly affect the air as it flows across the surface of the plane.
This happens as the plane enters the shockwave of the sound barrier, and ceases when they accelerate beyond the speed of sound.
At and beyond Mach 1 the buffeting is behind the plane, and flight is smoother, with no rattling or shaking from the incidental turbulence.
It also happens when decelerating, although it’s easier to decelerate safely through the buffeting quickly, since less time is spent in the shockwave, and a reduction in speed grants improved control.