Rialto, CA, USA
N625SB
McDonnell Douglas 600N
The sheriffs department helicopter was just beginning an evening patrol flight when the engine experienced a deceleration event during transition from climb out to cruise and the helicopter crashed into a residential street during an attempted autorotation. First responders to the accident site, which included sheriff's air unit mechanics, found the engine running at idle and a fire in the engine compartment. The helicopter had just come out of a scheduled 100/300-hour inspection and this was the first mission flight since the maintenance. During the inspection, the engine's fuel control Hydromechanical Unit (HMU) had been removed for compliance with a service bulletin. Prior to this flight, the helicopter had completed a 10-minute post maintenance flight check. The pilot in command (PIC) conducted the preflight inspection. The mission observer flight officer, who held a private pilot certificate with helicopter rating and was attempting to upgrade to a pilot position, had been given permission to fly the helicopter and installed the dual flight controls to the right side. No problems were noted during the preflight, and the takeoff was normal. About 500 feet above ground level during the transition from climb out to cruise, the pilot flying heard the LOW ROTOR voice warning (two times) followed by ENGINE OUT voice warning (two times). Without initiating an autorotation, he requested that the PIC take the flight controls. Simultaneously, the PIC had sensed a problem and took the flight controls. Prior to and during the departure up until the engine deceleration, the PIC performed the observer flight officer duties, which included radio communications with dispatch, and had not monitored the flight instrument readings or the progress of the departure. The LOW ROTOR voice warning activates when Nr falls below 95 percent. The voice warning system for ENGINE OUT activates when N1 falls below 55 percent or a high rate of decay in N1. No discrepancies were noted during the inspection of the airframe. A teardown of the engine disclosed no internal discrepancies; however, the fuel inlet line fitting to the engine HMU was found loose by two flats of the nut. Functional testing of the fire damage ECU (electronic control unit) found no discrepancies. The HMU was installed in a test bench and passed a functional check. The fuel line inlet fitting nut was then loosened incrementally one flat at a time with a functional test conducted each time. Significant fluctuations in metered fuel output flow were noted during one test with the nut three flats loose, and again at one complete turn loose. These results could not be reliably duplicated in subsequent tests. The investigation found that the operator had not established guidance for crew resource management pertaining to crew responsibilities, instrument monitoring responsibilities, emergency procedures initiation, or flight control transfer procedures when flying in a dual pilot operation.
1.1 HISTORY OF FLIGHT On October 3, 2002, at 1718 Pacific daylight time, a McDonnell Douglas 600N helicopter, N625SB, experienced a engine deceleration and crashed in a residential area located 3/4-mile south of the Rialto Municipal Airport (L67), Rialto, California, shortly after departure from a helipad. The San Bernardino County Sheriff's Department (SBSD) owned and operated the helicopter under the provisions of 14 CFR Part 91 as a public-use flight. The helicopter was substantially damaged. The commercial rotorcraft rated pilot and a deputy observer, a private helicopter pilot, were seriously injured. Visual meteorological conditions prevailed for the evening patrol flight. A company visual flight rules (VFR) flight plan had been filed. The helicopter had just come out of a scheduled 100/300-hour inspection and this was the first mission flight since the maintenance had been completed. Prior to this flight, the helicopter had completed a 10-minute post maintenance flight check. A mechanic for SBSD, located about 3/4-mile north of the accident site, observed the accident helicopter enter a left turn between 800-1,000 feet above ground level (agl). When he turned his back to go back inside, he stated that it "was quiet," so he looked back and saw the helicopter still in the air, but in a "dive towards the ground." The helicopter was in a "left diving steep turn," as if it were trying to gain airspeed. He lost sight of the helicopter as it passed behind the tree line. The mechanic reported that the helicopter was in a nose low attitude, approximately 70 degrees. He stated that he was able to see the top of the main rotor mast. He stated that the main rotor blades were turning fast enough that he was not able to count the blades. He did not hear any "popping noises, just silence." Prior to the diving turn, the helicopter had been in straight-and-level flight. Mechanics from SBSD who arrived on-scene with first responders and found the engine running at idle. They attempted to shut the engine down by turning off the fuel-shutoff valve, but it was stuck in the open position. The engine was eventually shut down. They turned off the battery, but did not recall if there were any instrument warning lights illuminated. One mechanic noted that the collective twist grip on the pilot's side was broken and he was not able to check the position of the ECU (Electronic Control Unit) switch on the collective. 1.1.1 Witness Information Witnesses in the surrounding area observed the helicopter traveling in a southerly direction when it made a descending turn to the north. The helicopter maneuvered around a house and descended through a tree prior to impacting the ground in a left nose and left skid low attitude. Witnesses indicated that the left landing gear and tail section separated from the helicopter after contacting the ground. The helicopter rotated around on it's left side and came to rest facing in a southerly direction. A compilation of witnesses stated that the helicopter was "slow," going about 30-40 miles per hour. Witnesses further stated that the engine was "very loud" and "revving." A witness, in a residence two blocks west of the accident site, observed the helicopter flying just above the rooftops. He lost sight of the helicopter as it descended out of his view. Another witness, located about one block south of the accident site, reported that the helicopter was 50-70 feet above the rooftops, and appeared to be losing altitude. The witness stated that the helicopter appeared to be "coasting." He also indicated that he did not see anything falling from the helicopter as it passed overhead. One witness observed the helicopter-flying overhead in a northbound direction. He indicated that the helicopter was very low, and the engine sounded like it was "going to blow." The witness stated that it looked like it was going to crash into a residence; however, it turned "quickly towards the left" and descended out of his view. A witness traveling southbound observed the helicopter traveling at an "extremely low level northbound." He saw the helicopter "drop" out of view, and did not see it rise above the houses or trees. A ground witness at the accident site stated that he looked up and saw the helicopter traveling in a northbound direction. The helicopter appeared to be "wobbling" and then came down and collided with the ground. 1.1.2 SBSD Air Unit and Pilot Statements 1.1.2.1 Sergeant/Pilot/Maintenance supervisor The National Transportation Safety Board investigator-in-charge (IIC) interviewed the sergeant, who is also a pilot and the maintenance supervisor. During the preceding 3 weeks while the helicopter was going through a 100/300-hour inspection, a series of ground runs had been conducted with no mechanical anomalies encountered. The day of the accident, he performed a preflight inspection in accordance with the manufacturer's Federal Aviation Administration (FAA) approved flight manual. The preflight inspection included a check of the engine compartment and engine for "any anomalies that would cause the aircraft to not function properly." The sergeant reported that he found no discrepancies during the preflight for the maintenance check on the day of the accident. During the flight check the sergeant conducted crosswind hovers in "all gradients," traffic pattern work, and autorotations. He did not feel any binding of the flight controls during the maneuvers. When he completed the flight check he conducted a "cool down prior to shutdown," and then put the helicopter back in the hangar. The Sergeant indicated that during the flight check he did not experience any uncommanded yaws, unusual vibrations, and no lights illuminated during power recoveries. The helicopter was then released for flight. He reassigned the night flight crew to fly the accident helicopter for a couple of hours. In a follow-up conversation with the Sergeant to clarify SBSD flight operational procedures, he noted that SBSD flight operations are conducted at a point on their facility that contains a concrete triangle with an "H" painted in middle of it. The pilots use this as the takeoff, departure, and arrival points. 1.1.2.2 Deputy/ Pilot-in-command According to the pilot-in-command's (PIC) written statement, Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), he arrived at his duty station at 1600, and began to preflight the accident helicopter. During the preflight, he "topped off" the fuel, and checked the fluid levels, and the engine compartment. He visually checked the air, fuel, and hydraulic lines for loose nuts ("slippage marks") in the engine compartment. He also visually checked the stabilizer for "play," main rotor assembly and fan, the tail section, and lights. According to the PIC, the helicopter was refueled to a total capacity of 650 pounds of Jet A fuel. While the PIC was conducting the preflight, the observer installed the dual flight controls so that he could fly from the right side. The PIC indicated that he was seated in the left seat. The PIC reported that he was also a training pilot for the air unit. His responsibilities were to provide transition training and/or be PIC while a new pilot built up their flight time. The PIC stated that the observer was flying the helicopter. They made a left-hand traffic departure from the sheriff's hangar, located on the southwest corner of the airport. Prior to and during the departure, the PIC was performing the job of observer flight officer, which included communicating with local area law enforcement agencies. A few minutes after takeoff, about 500 feet above ground (agl), he "sensed" something was wrong and that they were going down, he remembers grabbing the flight controls and looking for a place to land. He indicated that the helicopter was descending rapidly and he aimed for a street intersection. The PIC stated that they came close to houses and he had to maneuver between the houses. The PIC indicated that he could not recall the detailed events of the impact sequence. The IIC interviewed the PIC. During the left-hand turn to depart the traffic pattern, he realized that the helicopter was descending and took over the flight controls from the observer. The PIC indicated that he didn't recall hearing any audio tones, nor did he scan the gages, nor did he have time to look at the gages during the onset of the emergency. The PIC decided that he had about "5 seconds to make the right decision." He knew he would have to stretch the glide to find a safe place to land. The PIC noted that the collective lever and the nose of the helicopter were heavy. He indicated that up to the point where they were departing the traffic pattern everything had been normal. The PIC indicated that his responsibility was to be the flight observer on the accident flight. The other deputy would be the pilot flying the helicopter. The PIC recalled briefing the pilot flying that he (the PIC) would start the helicopter and if any emergencies took place the pilot flying would initiate the emergency procedures and then he (the PIC) would take the flight controls. 1.1.2.3 Deputy/ Observer/Pilot Flying In the written statement (NTSB Form 6120.1/2) the flying pilot/deputy observer indicated that he arrived at his duty station about 1550. He asked the PIC what aircraft they were flying, and the PIC indicated that they were going to fly one of the EC-120Bs. While they were on the hangar floor, the maintenance supervisor approached them and asked if they could fly the accident helicopter as it had just come out of the 100-hour inspection. The maintenance supervisor indicated that the helicopter had just completed a 10-minute flight check with no problems encountered and that it needed to be flown for a couple of hours to make sure nothing was wrong with it. The pilot flying asked the PIC if they could put in the dual flight controls so that he could fly. The PIC instructed him to get permission from the Lieutenant who subsequently approved the request for the addition of the dual flight controls. According to the pilot flying, the PIC was in the middle of the preflight when they were requested to respond to a callout. The request was cancelled prior to their departure. The pilot flying stated that the PIC went through the start up procedures, and the helicopter started with no problems. The PIC told the pilot flying that all the gages were in the "green" and that it was his aircraft to fly. The pilot flying stated that he took the helicopter to a hover and hovered to the "H". He performed several 360-degree pedal turns to get a feel for the helicopter. He then made a clearing turn and took off from the helipad westbound and made a climbing eastbound turn. There were no problems encountered with this portion of the flight. They continued in an eastbound direction. As he set up for cruise flight, he "reduced collective," noted the altitude as 500-feet agl, and the airspeed was between 80-90 knots. He then heard a "pop" from the engine followed by the audio voice warning system: 'low rotor, low rotor,' followed by 'engine out, engine out.' The pilot flying advised the PIC to take control of the helicopter. He then relinquished the flight controls to the PIC. The PIC made a northbound turn and entered an autorotation. The pilot flying indicated that their flight attitude was "almost straight down." The PIC turned the helicopter to avoid a house, and the pilot flying remembers the helicopter being almost level at that point. He did not recall anything about the impact. The IIC interviewed the pilot flying. The pilot flying stated that prior to the "pop" the engine sounded normal. When the engine made the "pop" noise he recalled not hearing the engine anymore. He did not look at the gages prior to or during the accident sequence. He indicated that he was building flight time and that he believed the flight was a training flight as well as a patrol flight. 1.5 PERSONNEL INFORMATION 1.5.1 Deputy/Certified Flight Instructor/Pilot-in-command According to SBSD, the pilot was hired on August 1, 1987, and assigned to the Aviation Division on April 22, 1989. A review of FAA airman records revealed that the PIC held a commercial pilot certificate with ratings for rotorcraft-helicopters and single engine and multiengine land and instrument airplane. The pilot also held a certified flight instructor certificate with a rotorcraft-helicopter rating issued on April 26, 1996. The CFI certificate expired on April 30, 2002. The PIC held a second-class medical certificate issued on September 27, 2001. It had the limitation that the pilot must wear corrective lenses. According to SBSD's Policy Manual under the section entitled PILOT PROFICIENCY/MEDICAL, "Pilots must hold a second-class medical certificate. The Commander may waive this requirement to accomplish a mission, but the pilot must obtain a current Class II medical within 30 days." Review of the pilot's records did not disclose a waiver for continued flight operations. According to NTSB Form 6120.1/2, SBSD indicated that the PIC accumulated an estimated total flight time of 11,500 hours. He logged 100 hours in the last 90 days, with 10 hours in the accident make and model. In the last 30 days he logged 30 hours, with 5 hours in the accident make and model. In the last 24 hours he, logged 5 hours. The PIC had an estimated 400 hours in the accident helicopter make and model. 1.5.2 Deputy/ Observer/Pilot Flying According to SBSD, the pilot flying was hired on April 4, 1988, and assigned to the Aviation Division on April 26, 1997. According to SBSD, there were no flight training records for the observer. A review of FAA airman records revealed the pilot flying held a private pilot certificate with a rotorcraft-helicopter rating issued on August 28, 2001. The pilot flying held a second-class medical certificate issued on July 7, 2002. It had no limitations or waivers. The pilot reported accumulating a total flight time of 83 helicopter hours. He logged 9.6 hours in the last 90 days, and 7.4 hours in the last 30 days. The pilot flying had 11.2 hours in the accident helicopter make and model. 1.5.3 San Bernardino County Sheriff's Department Aviation Division A review of SBSD's Policy Manual, Standard Operating Procedures, and flight training manual revealed no formal written training program to upgrade a deputy observer to a pilot. None of the aforementioned manuals elaborated on crew resource management with regard to rotorcraft crew responsibilities, instrument monitoring responsibilities, emergency initiation, or flight control transfer procedures. The Policy Manual contained a section for cockpit crew procedures for fixed-wing aircraft; however, there was no cockpit crew procedures section for rotorcraft. According to SBSD, in order to meet insurance requirements to act as PIC, the pilot must have 500 hours total time with 250 hours in turbine-powered rotorcraft, as well as complete a division recognized training program prior to be allowed to act as a PIC in department aircraft. According to SBSD, per the accident helicopter manufacturer's FAA approved flight manual, the PIC flies from the left seat. 1.6 AIRCRAFT INFORMATION The helicopter was a McDonnell Douglas 600N, serial number RN033. A review of the helicopter's maintenance logbooks revealed that it had accumulated a total airframe time of 2,400 hours at the last 100/300-hour inspection, which was completed on the day of the accident. Following the inspection, maintenance personnel performed a compressor wash followed by a ground run and leak check with no discrepancies noted. An annual inspection was completed on May 31, 2002. A 100-hour inspection was completed on July 12, 2002. The Hobbs hour meter read 2,300 at the last inspection. A Rolls-Royce Engine 250-C47M, serial number CAE 847832, was installed on the accident helicopter. Total time on the engine at the last 100/300-hour inspection was 2,400 hours. A hydromechanical unit (HMU), serial number JGALM0518, part number 23072725 (fuel metering unit part number 114070-03A
an engine deceleration event due to a loose HMU fuel line fitting, which was a result of inadequate maintenance procedures in the 100/300-hour inspection. Also causal was the flying pilot's and pilot-in-command's delayed recognition of the power loss, as well as, the flying pilot's failure to initiate an autorotation in a timely manner. The pilot-in-command's failure to regain and maintain adequate main rotor rpm was also causal. A contributing factor to the accident was the pilot-in-command's inadequate supervision and diverted attention due to his concentration on the flight officer observer duties.
Source: NTSB Aviation Accident Database
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