Beginning in 1943, Reaction Motors developed the XLR11 for the XS-1 (later X-1) supersonic research aircraft. The LR11 used ethyl alcohol and LOX fed to 4 thrust chambers. Chambers could be ignited separately or in any combination.
The earliest flight I can find for the XLR11 is on the XS-1 in 1946.

The U.S. Navy designation for this engine was the XLR8.

models

• XLR8-RM-6: 6,000 lb (26.7 kN)
• XLR11-RM-5: 6,000 lb (26.7 kg) thrust
• XLR11-RM-13: 8,000 lb (35.6 kg) thrust

specifications

• Liquid-fuel rocket
• Fuel: ethyl alcohol
• Oxidizer: liquid oxygen (LOX)

used by

• Bell X-1
  Douglas D-558-II
  Martin X-24
  Republic XF-91