NTSB Identification: IAD98GA110
Accident occurred Friday, September 25, 1998 in NEWARK, TX
Probable Cause Approval Date: 11/22/2000
Aircraft: Hughes OH-6A, registration: N234ZM
Injuries: 1 Fatal,1 Serious.
: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.
The flightcrew and helicopter were properly certified and maintained in according with federal regulations. Weather was not a factor. At the time of the accident, the flight was not communicating with any tower or air traffic facility. Communications could have aided in initiating rescue and fire-fighting operations if a check-in schedule with KAFW tower or other facility or agency had been established. Facilities affected the accident, because there were no extinguishers or other fire-fighting equipment at the accident site, which was a usual autorotative training area. There was pilot-stated evidence that there may have been a power-related or other control problem with the accident helicopter, becoming apparent at a most critical time, that is, during power-on recover from a demonstrated autorotation. Specific evidence came from the interview and statement of a DEA Special Agent/Pilot, who on September 14, 1998, took the TP on a demonstration flight in the accident helicopter, prior to the TP beginning the OH-6A transition syllabus. The Special Agent/Pilot's written statement to the accident investigation, stated in part, 'The aircraft was flared, forward momentum was checked, and the aircraft was leveled as it started to descend toward the ground. At this time, collective was applied in order to recover to a three foot hover. I was surprised at the engine's reaction. I perceived a delay followed by an engine surge which created a significant yaw to the right.' Also, following his initial statement, when asked about the availability of power during recovery from the practice autorotations, the TP emphatically stated, 'Make sure you check that engine.' The engine was disassembled for an engineering examination and report under Safety Board IIC-oversight at Rolls Royce Allison, Indianapolis. In a similar manner, the main gearbox, transmission drive shaft, and overriding clutch were disassembled and subjected to engineering examinations and a report at the Boeing facility, Mesa, Arizona. The components examined at the two facilities were not severely fire-damaged. The engine, upon disassembly, evidenced that it was capable of producing power at the time of impact. The examinations of the main gearbox/overriding clutch systems showed no evidence of pre-impact damage and evidenced the ability to turn normally prior to impact. However, because of extensive fire damage or destruction to the fuel cells and related fuel lines, that system was not capable of being subjected to similar engineering examinations. Following a request at the beginning of the interview that he initially describe the event in his own words, and a few questions would then follow, the TP described a series of events that began after he made the comment regarding a '50 foot area,' in which the IP quickly took control of the helicopter, entered a climbing turn, leveled out, and then initiated an abrupt, steep angle of bank, and steep approach to a final in which the TP, 'hoped there would be enough at the end.' The impact site showed tail rotor blade strikes, first, evidencing a high nose attitude at impact. A high nose attitude at impact may indicate that, if the helicopter were responding to control inputs, the pilot was still attempting to arrest momentum. The IP was involved in an incident on November 3, 1995, in which the DEA Aviation Section Incident Form states, he 'took control of the A/C and said that he would demonstrate a zero airspeed autorotation.' That description is similar to the IP taking control of the accident helicopter following the TP's statement. The 1995 incident report continues, the IP 'then entered the maneuver and began explaining a proper procedure. At approx. 70' AGL [he] began to flare the A/C at which point [he] stated, 'I forgot to roll the throttle in.'' The autorotative recovery continued as an overtorque. 'As the A/C began to level at approx. [? feet] I noticed the torque gauge indicate past 120 [percent] at which point the maneuver was terminated [in] a hover.' The 1995 incident report leaves questions unanswered, but '120 percent' [an overtorque] raises a question whether an overtorque was necessary to recover, and 'terminate in a hover.' The IP was the only OH-6A instructor pilot for the DEA at KAFW. However, an interview with the training officer evidenced a lack of scheduled standardization meetings or procedures involving unit IPs, regardless of models, or involving the accident IP and the other OH-6A pilots in command that were based at KAFW. Scheduled standardization meetings should have been even more useful than normally expected, in that the flight operations manual was essentially copied from the U.S. Army manual, and, as the DEA training officer confirmed, under specific instructor pilot and transition pilot performance criteria, there was no more precise writing than that which was found in the OH-6 Pilot Transition lesson plan, which stated, 'Introduce Autorotations.'
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Failure of the Instructor Pilot to control the helicopter's rate of descent during a demonstrated autorotation. Contributing to the accident were the Operator's lack of: a. Instructor Pilot standardization procedures, and b. Specific or adequate flight demonstration procedures and techniques for both instructor and transition pilots. Full narrative available
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