About 2100 central standard time, on March 23, 2001, a Boeing 727-200, N275US, operated by Northwest Airlines, as Flight 934, blew over a ramp employee during a power back from the terminal gate at Memphis Tennessee International Airport in Memphis, Tennessee. Flight 934 was operated under the provisions of Title 14 CFR Part 121, as a scheduled, domestic passenger flight from Memphis, Tennessee, to Miami. The flight was scheduled to depart the Memphis Tennessee International Airport at approximately 2100. There were three crewmembers and 124 revenue passengers on board Flight 934. No injuries were reported by the flight crew or the passengers. The wing walker received serious injuries. Visual metrological conditions prevailed at the time of the accident. The flight was operated on an instrument flight plan. According to the Northwest Airlines Safety Official, a wing walker was removing a stuck wheel chock from the right main landing gear during a power-back from the gate. The wing walker was blown over by the jet blast after the chock was removed. The wing walker received serious injuries. The flight was cancelled, and the passengers were deplaned. According to the flight crew, they were given the signal for engine start. After completing the taxi check, the flight crew signaled they were ready for powerback. The flight crew then stated, the coordinator signal for them to come forward. The captain moved the airplane forward by applying forward thrust. The Powerback/Coordinator then gave the flight crew the signal to stop. After a slight delay, the Powerback Coordinator then gave the powerback signal. The captain moved the throttles into reverse thrust, moving back for a very short distance. The Powerback Coordinator then gave the crew the stop signal. According to the Powerback Coordinator, there was a stuck wheel chock under the right main inner landing gear on the aft side. He gave the signal for the airplane to move forward so that the wing walker could remove the chock. After the airplane moved forward, he then gave the signal to stop. The wing walker unchocked the airplane, and proceeded to position himself for powerback. The wing walker was then blown to the ground behind the left main gear. The Powerback Coordinator stated that due to darkness he could not see the wing walker behind the gear. The Powerback Coordinator stated that the airplane started to move backwards, and he gave the crew the emergency stop signal. According to the wing walker, the airplane had settled back on the right main landing gear chock. He advised the marshaller that he would remove the chock when the airplane was moved forward. As the airplane was moved forward, the wing walker removed the chock and disposed of it to the right. He walked back under the airplane to the left wing. As he was exiting the left side, he heard the thrust reversers deploy and was knocked down by the reverse thrust. The wing walker stated that he was in no position to see the Powerback Coordinators signals. The Northwest Airlines Standard Practice Manual states, Powerback Coordinator (Marshal)-(Provides signals to the Captain) "Item A.1a. The Marshal is responsible for ensuring Wing Walkers are in proper position before giving the all clear signal. Never signal the flight deck crew to move the aircraft until the Wing Walker is in position and ready".