Last week: Sikorsky-Boeing SB-1 Defiant flew 205kts /380km/h

[Stratofreighter]

https://www.flightglobal.com/helicopter ... 60.article

The Sikorsky-Boeing SB-1 Defiant flew 205kt (380km/h) in a flight test on 9 June.

The compound co-axial helicopter passed 200kt for the first time
while flying at Sikorsky’s West Palm Beach Development Flight Test Center in Florida,
Boeing and Sikorsky announced on 16 June 2020.

Within a few months, the Sikorsky-Boeing team is pushing for the helicopter to top 250kt –
above the US Army’s 230kt cruise speed requirement
for the Future Long Range Assault Aircraft (FLRAA) programme.

“We went to 205kt with less than 50% of the installed propeller power,”
says Bill Fell, lead test pilot for the SB-1.

“So, expect a lot more in the future because we have a lot more power to apply to this machine.”

The SB-1 is competing against Bell’s V-280 Valor tiltrotor in the US Army’s FRLAA programme.
That aircraft has reached a top speed of 300kt.

...and
https://www.flightglobal.com/helicopter ... 60.article
has far more...