ให้มาแล้ว !! เลขเด็ดประจักษ์ศิริ งวด 16/04/62

It was only in 1942 when helicopters reached full-scale production. At that time, 131 helicopters were successfully manufactured. In that short period of time that the helicopters were produced, they become both useful and necessary aircraft.
from: http://ezinearticles.com/?Helicopter-Lessons---Initial-Steps-Necessary-to-Begin-Flying-Helicopters&id=3220902