On July 25, 1997, at 1530 hours mountain standard time, a Robinson R-22 Beta, N4008D, collided with the ground following an in-flight loss of control while on the crosswind leg for landing at Chandler, Arizona. The aircraft was destroyed by the ground impact sequence. The flight instructor sustained serious injuries and the dual student sustained minor injuries. The aircraft was being operated as a instructional flight under 14 CFR Part 91 when the accident occurred. The flight originated in Chandler at an undetermined time for a takeoff and landing practice. Visual meteorological conditions prevailed at the time of the accident. The certified flight instructor (CFI) told the Federal Aviation Administration (FAA) that they departed Chandler Municipal Airport between 1500 and 1515. They were en route to Chandler Memorial Airport for pattern work. Once they arrived, he had the student practice steep approaches, hover techniques, autorotations, and normal takeoff procedures. The CFI reported that the aircraft was operating normally. The CFI told the FAA inspector that he instructed the student to "perform a takeoff and climb maneuver, flying runway heading 30, then turn left (20-25 degrees) at 1900' msl." In the turn, the CFI stated he took over the aircraft controls because "Mr. Tabata was not performing the maneuver properly." The CFI told the FAA in his written statement that the "aircraft was loosing altitude. . .he said he tried full up collective and full throttle but the aircraft did not respond and crash landed in the west side of the runway." The CFI reported in his report that the aircraft was "suddenly in a nose-low attitude with a high rate of descent." He said he tried to raise the collective to stop the descent rate with no apparent result. He further stated that there were "numerous dust-devils" around the airport which they had maneuvered around several times. He stated he "believes we encountered one of these dust-devils, thus leading to the accident, and loss of control." The dual student was interviewed by the FAA inspector on July 26, 1997. He told the FAA inspector that he preflighted the helicopter and found no discrepancies to report. He stated that he verified fuel tank quantity, visually, and with the fuel tank indicator; both of which registered full. He stated that this was the first flight of the day for both the aircraft and both pilots. The student stated that after accomplishing the preflight run-up, they departed Chandler Municipal Airport to the west en route to Chandler Memorial Airport. He stated the cruise altitude to Chandler Memorial Airport was 1700 feel msl. He said they entered the traffic pattern at 1700 feet using runway 30 with a left traffic pattern. The student reported that they made one normal approach to runway 30, performed hovering and landing techniques on the runway numbers, performed 360-degree turns, and then proceeded to climb out to traffic pattern altitude and performed one steep approach. Afterwards, they performed two autorotations and two 180-degree autorotations. The student reported that at approximately 1530 he performed a "normal take-off" climbing to 1700 to 1800 feet and "began a 30 degree bank to the left." He stated that the instructor felt the turn was "too lazy" and took control of the aircraft. He said the instructor proceeded to "increase the bank of the aircraft to approximately 45 degrees (to the left)." He further stated that the aircraft then began to pitch nose down, the collective and cyclic began to shake and vibrate, which continued until impact. The student also told the FAA that the aircraft had a nose-up attitude prior to impact. The student holds a private pilot certificate with single engine land and rotorcraft-helicopter ratings. He told the FAA that he had approximately 76 hours of fixed wing time and 233 hours in rotorcraft. He said he arrived in Arizona on July 8, 1997, and began flight training with the operator on July 10, 1997. He was training for a commercial add-on rating in rotorcraft. At the request of the Safety Board, the engine was examined under the supervision of an FAA inspector on August 4, 1997. According to the inspector's report, both the left and right magneto's were operationally bench tested and run with no abnormalities revealed. Both of the magneto harnesses also bench tested satisfactorily. All of the spark plugs were removed and appeared normal. The carburetor bowl was opened and revealed no abnormal residues or contaminants.