Incident Overview
On Friday, June 22, 2007, at 13:20 local time, a Robinson R44 Raven helicopter with registration EC-JDT crashed near Puerto de Malagón in San Lorenzo del Escorial, Madrid. The aircraft was operated by Intercopters, S.L., and was conducting commercial aerial observation work for police training purposes.
Flight Details and Crew
The helicopter departed from Cuatro Vientos Aerodrome at 10:31 local time with four people on board: the pilot in command, a qualified co-pilot, and two police officers from the BESCAM unit undergoing aerial observer training. The pilot had approximately 9,000 total flight hours but only 200 hours on the R44 type. The aircraft was flying at a pressure altitude of 5,100 feet with an estimated weight of 2,324 lb, which was close to the maximum allowable limit for that altitude and temperature.
Accident Sequence
During an approach to a flat area for a position change, the helicopter was at 20 feet above ground level with an indicated airspeed of 30 KIAS. The low rotor RPM warning system activated both acoustically and visually. The pilot lowered the collective pitch lever and attempted to gain speed to stabilize the aircraft for a rolling landing. However, the helicopter descended, impacted the ground, and overturned onto its right side.
Investigation Findings
The investigation found no evidence of mechanical malfunction causing the RPM drop. The probable cause was identified as an increase in blade angle of attack as the helicopter lost translational speed to maintain lift at high altitude and weight. At this altitude, the electronic governor is less effective, requiring manual throttle control. The pilot likely failed to open the throttle immediately upon receiving the warning, leading to a critical drop in rotor RPM and subsequent loss of lift.