History of Flight
On October 12, 2009, at 1100 Pacific daylight time, a MD Helicopter, Inc. (MDHI) 600N, registration N613BP, landed hard after a practice 180-degree autorotation at Gillespie Field Airport (SEE), San Diego, California. The Department of Homeland Security - Customs and Border Protection (CBP) operated the helicopter under Title 14 Code of Federal Regulations Part 91 as a public-use training flight. The MDHI factory training pilot (FTP) was not injured, while the CBP standardization instructor pilot (IP) sustained minor injuries. The helicopter experienced substantial damage; the skids spread and the aft portion of the skids penetrated the fuselage. The flight had departed Brown Field Municipal Airport (SDM) at 1000 with no flight plan filed.
The FTP, acting as pilot-in-command (PIC), stated the flight aimed to evaluate his suitability for conducting autorotation training for CBP pilots. The helicopter's gross weight at departure was 3,570 pounds. After performing several hovering autorotations, they progressed to full touchdown autorotations. The PIC performed the first without issues. Fuel weight was then between 600 and 650 pounds, and helicopter weight was about 3,450 pounds. The PIC noted main rotor rpm remained at the lower part of the green arc, occasionally dipping below if collective was increased during descent. His first approach was deliberately fast, and the helicopter slid about 50 yards after touchdown.
Each pilot performed two touchdown autorotations, with similar 50-yard slides. The PIC indicated that a slower touchdown speed would have increased damage risk. He informed the IP he would execute the first 180-degree autorotation at an entry altitude of 500 feet above ground level (agl), based on his experience. On the accident autorotation, the PIC maintained 85–90 knots, hoping for a more aggressive deceleration flare. However, the rate of descent was high, and as the helicopter rolled onto runway heading, it became apparent that the descent was excessive and altitude insufficient for a proper flare or power recovery. He attempted to level the helicopter before impact. The left skid contacted the runway first, collapsed, and the helicopter slid about 100 yards before stopping. Witnesses videotaped the flight.
Aircraft Information
The 1999 MDHI 600N, N613BP, serial number RN045, was powered by a Rolls-Royce 250-C47M turboshaft engine. Total time was 3,192.5 hours. Last maintenance, including weighing, occurred on October 7, 2009; the last 100-hour inspection was on April 5, 2009.
Meteorological Information
At the time of the accident, Gillespie Field (elevation 388 feet) reported overcast skies, temperature 68°F, and calm winds. Nearby Montgomery Field (MYF), 9 nautical miles west, reported few clouds at 3,400 feet, overcast at 4,400 feet, wind from 140° at 6 knots, temperature 17°C, dew point 9°C, and altimeter 29.89 inHg.
Examination Findings
Examination revealed no pre-impact malfunctions; flight control continuity was established. The NOTAR (no tail rotor) components, including the main rotor transmission, NOTAR transmission, and fan assembly, rotated freely. No visible damage to the tail boom or NOTAR empennage was noted. The left side of the airframe near the outboard landing gear damper attachment structure sustained damage, with the landing gear struts spread and the damper attachment structure torn and deformed.
According to the manufacturer's autorotation percentage chart (CSP-HMI-2, chapter 18-10-60, table 502), sufficient autorotation rpm is ensured at minimum gross weight. The main rotor rpm range is 90% to 106.4%. At the accident weight and density altitude, the main rotor rpm should have exceeded the 106.4% red line, requiring the pilot to increase collective pitch to stay within limits. The manufacturer's representative indicated that diminished main rotor rpm availability reduces autorotation capability.
Weight and balance data showed an operational weight of 3,406 pounds and a longitudinal center of gravity (CG) of 92.7 inches, within the certificated maximum gross weight of 4,100 pounds and CG limits of 91 to 96 inches.