52-01-06 BELL: (Applies to All Model 47 series Helicopters Having Covered Tail Booms.
Compliance required at next 300-hour overhaul, but not later than March 1, 1952.
To prevent the main rotor striking the tail boom as a result of boom deflection when yawing at high forward speed, install the 47-706-211-1 or -2 spoiler on the tail boom. (Note: Spoiler must not be installed on any helicopter having an uncovered tail boom.)
(Bell Service Bulletin No. 81 covers this same subject.)