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Subject: 119 rotor droop
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helicopterkeysUser is Offline
JH Newbie
JH Newbie

07/03/2005 12:07 PM  
There are four 119 accidents in the NTSB database. Three of them involve rotor RPM droop, one is the incident in CA that DOC referred to in earlier posts on the other forum. The last is a TR failure. If the NR droops when the collective is lowered, as it did in the Utah crash, something is very wrong. All three listed NR droop cases happened in the mountains. I could be wrong about Austria but I think that was at least 4500 feet, Ogden 4200-5200 ( according to the city web site ), and Big Bear 6700. The Durango crash is in the 9000-10000 foot range, just an estimate on my part, no real data there. The Austrian pilot reported a droop to 70 % NR, I am surpised he did not drop out of the sky, but he also had forward airspeed. NTSB reports: On November 9, 2001, approximately 1445 mountain standard time, an Agusta A119 helicopter, N119RX, registered to Agusta Aerospace Corporation (AAC) of Philadelphia, Pennsylvania, and operated by Intermountain Health Care, dba IHC Life Flight of Salt Lake City, Utah, was destroyed during a hard landing at Mackay-Dee Hospital's helipad in Ogden, Utah. The pilot, the company's director of operations (also a pilot), and a flight nurse received minor injuries. Visual meteorological conditions prevailed, and no flight plan had been filed for the business flight being conducted under Title 14 CFR Part 91. The flight originated at Salt Lake City International Airport approximately 1300. Prior to accepting delivery of the helicopter from AAC in Philadelphia, Intermountain Health Care's (IHC) pilot noticed a 4 percent decay in engine and rotor rpm when the collective control was lowered after landing, activating the aural and visual LOW ROTOR RPM warnings. After a few seconds, engine and rotor speed returned to normal. Another Agusta 119 operator reported encountering the same situation. IHC's lead mechanic discussed the problem with Agusta's chief pilot and a technical representative, and told them he wanted it corrected prior to their departure. According to IHC, no one at Agusta could explain the phenomena, and no one seemed to know what the normal operation of the electronic engine control (EEC) and engine governing system should be when the collective control was lowered. A Pratt and Whitney technical representative said it should be of no concern as long as it operated normally during flight. He suggested adjusting the linear variable differential transducer (LVDT) after they returned home. On November 1, the helicopter was ferried from Philadelphia, Pennsylvania, to Salt Lake City, Utah. According to the pilot's accident report, they flew to Mackay-Dee Hospital in Ogden, Utah, to make a ground survey of its new helipad. He intended to make a low pass and circle to land. He lowered the collective control and noticed engine and rotor rpm had decreased to 96 percent, activating the LOW ROTOR RPM warnings. He realized he was too low to attempt an autorotation. He reduced collective and pitch attitude further. RPM drooped to 90 percent and stabilized. Approximately 20 to 30 feet above the helipad, the pilot raised the collective control to flare for landing. RPM rapidly deteriorated. The aircraft impacted the helipad in a tail-down position, rolled over, and came to rest on its left side. The entire accident was captured on videotape. On-site examination of the helicopter by FAA and IHC personnel revealed the throttle was in the cutoff position. There was fuel in the fuel filter bowl. The position of the Manual/Normal switch was inconclusive, but they noted the switch was "the third and final form of engine control in the event of failure of both the EEC and the MEC (mechanical engine control) system." In the Manual position, it allows the pilot to increase throttle past the flight gate and "provides direct mechanical control of the FCU (fuel control unit)." In the Normal position, the switch "provides a mechanical stop to prevent [throttling] past the flight [gate] position, and provides the 'detent' feeling for the flight position. IHC's report indicated the Py air line to the P3 filter was tight, but the jam nut to the filter housing was loose, creating a "slight" leak. There was a "slight" misrigging of the pilot and copilot's twist grip, resulting in a 60-degree difference on the FCU. The compressor and power turbine were unremarkable. The MEC/EEC mode select switch functioned correctly and revealed a collective lever pitch (CLP) fault code 6 (faulty LVDT). Further investigation revealed the LVDT to be inoperative, possibly due to impact damage. The rotary variable differential transformer (RVDT) was found rigged at 57.9 degrees of twist grip travel at the Flight Gate position. According to the A119 maintenance manual, the RVDT is supposed to be rigged to achieve 60 degree (+ or - 1 degree). Cutoff position was found to be set at 0. IHC concluded that this RVDT misrigging would cause incorrect fuel scheduling to the fuel control unit (FCU). The engine and accessories were shipped to Pratt & Whitney (P&W) Engine Company in Quebec, Canada, for disassembly, examination, and testing. According to P&W's report, "The investigation and analysis of the engine hardware control system components did not reveal any discrepancies which could have contributed to the reported power loss. The engine and its controls show no deterioration of their integrity or ability to respond to commands, thereby meeting normal operational performance requirements." At the time of the accident, the helicopter had approximately 40 hours total time-in-service. Next: On October 14, 2002, about 1230 local time, near Idalpe, Austria, the pilot of an Agusta 119A, DE-XSB, operated by Schenk Air GmbH, experienced a reported rotor rpm drop to 70 to 80 percent for 20 seconds, followed by a rotor speed increase which could not be stopped even with manual control. The rotor rpm changes were experienced during rescue training purposes while a rescuer was attached to an external cable. The pilot attempted to drop the rescuer over a lake from a reported 15 foot altitude at 70 to 80 knots indicated airspeed. The rescuer was later located and found deceased. The investigation is being conducted under the authority of FUS Flugunfalluntersuchungsste, Austria. The National Transportation Safety Board has offered assistance to the investigator-in-charge, FUS ; a Pratt & Whitney engine company service representative is reported assisting, on site. For further information, please contact: Mr. Gunter Raicher FUS tel 43 1 711 62-9200 / fax 9299 US Accredited Representative: Thomas R. Conroy Air Safety Investigator Office of Aviation Safety 490 L'Enfant Plaza East, SW Washington, DC 20594 1 202 314-6314
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