12-Dec-2010 Source: Carson Helicopters
Carson Helicopters has been an active participant in the NTSB investigation of the Weaverville crash of N612AZ and as such has not commented publicly during the investigation due to regulatory prohibitions. We have a strong commitment to all the people affected by this tragic accident and to current flight operators of the S61 helicopter to understand what caused this accident.
It became apparent to Carson management and other members of the investigation team that there were issues with one of the 36 performance charts and the weight estimate of the aircraft provided by a Carson employee for performance of the Forest Service contract. Carson forthrightly acknowledged these issues that were the actions of one manager who acted without the knowledge or consent of Carson senior management and is not reflective of Carson’s 50 years of dedicated flight operations, 30 years of firefighting and exemplary safety record.
It is Carson’s firm contention that the facts clearly show that the primary cause of this accident was a loss of power to the #2 engine of the aircraft. There is a strong chain of physical evidence in the Public Docket that indicates a high probability that a malfunctioning fuel control unit (FCU) caused a sudden loss of power as the aircraft transitioned to forward flight. Extensive independent real-world flight testing has confirmed that even at weights exceeding what the NTSB has attributed to the accident aircraft, N612AZ should have had enough power to fly away from H44 with two properly operating engines. The co-pilot has confirmed much of this evidence with his recent testimony. The two pilots had nearly 26,000 flight hours of cumulative experience, and the copilot is an experienced ex-military Blackhawk pilot and B52 aircrewman. The NTSB has ignored his testimony in favor of supposition. Carson has repeatedly provided to the NTSB substantial evidence that the actual weight of N612AZ was several hundred pounds less than the NTSB has theorized.
Unfortunately, early in this investigation the NTSB lost custody of several fuel control parts, and conducted a filter inspection incorrectly, which they have acknowledged. Since that time, the NTSB has chosen to ignore the physical evidence and flight parameters that indicate a possible blockage in the FCU. They repeatedly refused to participate in independent flight testing, and they have not given proper consideration to the copilot’s direct testimony of conditions and available power just prior to the crash.
Carson has discovered there is a history of contamination and FCU power loss issues in the S61 Helicopter that was known by other parties. We regard this as an ongoing safety of flight issue and continue to pursue the source of the problem even as the body of evidence has grown indicating that a partial power loss was the major contributing factor to the loss of the crew and passengers of N612AZ. We continue to extend our thoughts and prayers to the families and loved ones of everyone involved.
The following points can be verified in the Public Docket as referenced
1. Actual meteorological conditions recorded on the CVR from the pilots and professional ground crew indicate that the correct temperature and wind is 20 deg. C and 3-5 knots of headwind. At this condition the aircraft had 420-750 lbs. of weight margin as calculated from FAA approved performance charts (NTSB Hover Study, Coultas Response 455943).
2. Repeated independent flight tests commissioned by Carson at the same density conditions and weights exceeding the accident aircraft show that it had sufficient power to fly away, except when power was partially removed from one engine (Carson Submission, II-F, Exhibit 5, Docket 438758, 446197). The NTSB has repeatedly refused to consider this real data in favor of Sikorsky flight simulations using datasets from differently configured aircraft.
3. The #2 engine had rpm fluctuations the last flight day before the accident. The #2 engine had significantly less internal damage and wear patterns than #1, possibly indicating it was running at lower power. Recovered intact torque gauges indicate the #2 engine was producing 30% less torque at impact. The #2 emergency throttle was halfway engaged. The copilot recounted that he had engaged the #2 emergency throttle after seeing a torque loss to #2 on the gauges right before impact (455939 Douglass affidavit, Carson Submission, III-A through E, NTSB Operations Report, Docket 444680-444684)
4. Significant contaminants ranging in size up to 28 microns were recovered from inside the #2 Fuel control Pressure Regulating Valve. Particles bigger than 4 microns can jam the Fuel control unit and cause uneven fuel flow and power. There is significant history about contaminant problems in this Fuel control unit that has been discovered in this investigation (Carson Submission, IV-A through E, Exhibits 8, 10-23)
