Crash During Takeoff of Firefighting Helicopter, U. S. Forest Service, Sikorsky S-61N, N612AZ, Weaverville, California, August 5, 2008
This is a synopsis from the Safety Board's report and does not include the Board's rationale for the conclusions, probable cause, and safety recommendations. Safety Board staff is currently making final revisions to the report from which the attached conclusions and safety recommendations have been extracted. The final report and pertinent safety recommendation letters will be distributed to recommendation recipients as soon as possible. The attached information is subject to further review and editing.
On August 5, 2008, about 1941 Pacific daylight time, a Sikorsky S-61N helicopter, N612AZ, impacted trees and terrain during the initial climb after takeoff from Helispot 44 (H-44), located at an elevation of about 6,000 feet in mountainous terrain near Weaverville, California. The pilot-in-command, the safety crewmember, and seven firefighters were fatally injured; the copilot and three firefighters were seriously injured. Impact forces and a postcrash fire destroyed the helicopter, which was being operated by the U.S. Forest Service (USFS) as a public flight to transport firefighters from H-44 to another helispot. The USFS had contracted with Carson Helicopters, Inc. (CHI) of Grants Pass, Oregon, for the services of the helicopter, which was registered to CHI and leased to Carson Helicopter Services, Inc. of Grants Pass. Visual meteorological conditions prevailed at the time of the accident, and a company visual flight rules flight plan had been filed.
- The flight crew was properly certificated and qualified in accordance with U.S. Forest Service contract requirements and Federal Aviation Administration regulations.
- No evidence was found of any pre-impact airframe structural or system failures.
- The emergency response and rescue of the injured firefighters and copilot were timely, and they were transported as quickly as possible given the constraints associated with, and limited access to, the accident site.
- Because Carson Helicopters provided an incorrect empty weight to the pilot-in-command, he overestimated the helicopter's load carrying capability by 1,437 pounds.
- The altered takeoff (5-minute) power available chart that was provided by Carson Helicopters eliminated a safety margin of 1,200 pounds of emergency reserve power that had been provided for in the load calculations.
- The pilot-in-command followed a Carson Helicopters procedure, which was not approved by the helicopter's manufacturer or the U.S. Forest Service, and used above-minimum specification torque in the load calculations, which exacerbated the error already introduced by the incorrect empty weight and the altered takeoff power available chart, resulting in a further reduction of 800 pounds to the safety margin intended to be included in the load calculations.
- The incorrect information—the empty weight and the power available chart—provided by Carson Helicopters and the company procedure of using above-minimum specification torque misled the pilots to believe that the helicopter had the performance capability to hover out of ground effect with the manifested payload when, in fact, it did not.
- The efficiency of the engines' compressors was not compromised, and the stator vanes functioned normally throughout the accident flight.
- The trace contaminants found within the fuel control units (FCUs) did not affect their operation, and both FCUs functioned normally throughout the accident flight.
- Both engines were operating normally throughout the accident flight.
- The accident takeoff was unsuccessful because the helicopter was loaded with more weight than it could carry in a hover out of ground effect given the ambient conditions.
- Safety would be improved if the hover-out-of-ground-effect capability indicated by performance charts represented all conditions for which the charts are applicable, including light and variable wind conditions.
- The lower-than-actual empty weights recorded by Carson Helicopters on the Chart B weighing records for the accident helicopter and 8 of Carson's other 10 helicopters created the appearance of higher payload capabilities; at their actual weights, the accident helicopter and 5 of the other helicopters would not have met the contractual payload specifications.
- The U.S. Forest Service's oversight of Carson Helicopters was inadequate, and effective oversight would likely have identified that Carson Helicopters was using improper weight and performance charts for contract bidding and actual load calculations and required these contractual breaches to be corrected.
- Although the U.S. Forest Service attempted to provide for safe operations by contractually requiring that the operator comply with 14 Code of Federal Regulations Part 135, these requirements without effective oversight were not adequate to ensure safe operations.
- The U.S. Forest Service's inadequate training of the inspector pilot led to his failure to correct the pilot-in-command's improper usage of above-minimum specification torque and contributed to his failure to identify the helicopter's marginal performance on the first two takeoffs.
- The Federal Aviation Administration's oversight of Carson Helicopter Services, Inc. (CHSI) was inadequate, and effective oversight would have detected discrepancies in the accident helicopter's maintenance, performance, and weight-and-balance documents and required their correction before the helicopter was added to CHSI's 14 Code of Federal Regulations Part 135 operations specifications.
- The pilots likely recognized that the helicopter was approaching its maximum performance capability on the two prior departures from Helispot 44 but elected to proceed with the takeoffs because they were accustomed to performing missions where operating at the limit of the helicopter's performance was acceptable.
- The performance of a hover out of ground effect power check before takeoff from helispots located in confined areas, pinnacles or ridgelines would increase flight safety.
- Without an immediate fire, additional occupants on board the helicopter would likely have survived the accident.
- The postcrash fire likely originated from the ignition of the fuel that was released or spilled from the helicopter's fuel tanks when the left side of the helicopter impacted the ground.
- The majority of the cabin seats that were occupied during the crash separated from the floor during the helicopter's impact with the ground, subjecting the occupants to secondary impacts from other occupants and seats and hindering their ability to evacuate the cabin.
- If the accident helicopter had been equipped with seat installations that met the load limit requirements of 14 Code of Federal Regulations (CFR) 29.561, more occupants may have survived the accident because the seats likely would not have separated from their mounting structures. Further, energy absorbing seat systems that met the requirements of 14 CFR 29.562 would have provided additional occupant protection.
- The surviving firefighters were unable to release the rotary restraints under emergency conditions because they were unfamiliar with the rotary-release mechanism.
- The leather gloves worn by the firefighters decreased their dexterity, hampering the release of their restraints after the crash.
- The U.S. Forest Service contract requirement for Carson Helicopters to install shoulder harnesses on the passenger seats did not provide improved occupant protection because Carson Helicopters installed the shoulder harnesses on seats with non-locking folding seatbacks.
- The designated engineering representative's failure to follow Federal Aviation Administration guidance materials resulted in his approval of a shoulder harness installation that did not improve occupant protection and, in fact, increased the risk of injury to the occupant.
- The Federal Aviation Administration disregarded its own guidance and condoned the installation of a shoulder harness that did not improve safety, and in fact, increased the risk of injury to the occupants.
- Making accurate basic weather information available to flight crews operating at remote helispots would increase flight safety.
- The 10-micron airframe fuel filters will reduce the risk of sticking or seizure of a pressure regulating valve or pilot valve, which could result in the degradation of engine performance during a critical phase of flight.
- An operating flight data recorder would have provided detailed information about the accident scenario and, thus, would have aided the National Transportation Safety Board in determining the circumstances that led to this accident.
- The Carson Helicopters, Inc., supplemental type certificate for installing side-mounted seats is misleading because it refers to the installation of the Martin Baker crash-attenuating seats, yet the total seat system does not provide occupant protection beyond the Civil Aviation Regulations 7.260 requirements.
- The Federal Aviation Administration missed an opportunity to require crashworthy improvements in an older transport-category helicopter when it issued a supplemental type certificate to Carson Helicopters, Inc., for installing side-mounted seats without requiring incorporation of any requirements beyond the certification level of the original seats (Civil Aviation Regulations 7.260).
The National Transportation Safety Board determines that the probable causes of this accident were the following actions by Carson Helicopters: 1) the intentional understatement of the helicopter's empty weight, 2) the alteration of the power available chart to exaggerate the helicopter's lift capability, and 3) the practice of using unapproved above-minimum specification torque in performance calculations that, collectively, resulted in the pilots' relying on performance calculations that significantly overestimated the helicopter's load-carrying capacity and did not provide an adequate performance margin for a successful takeoff; and insufficient oversight by the U.S. Forest Service and the Federal Aviation Administration.
Contributing to the accident was the failure of the flight crewmembers to address the fact that the helicopter had approached its maximum performance capability on their two prior departures from the accident site because they were accustomed to operating at the limit of the helicopter's performance.
Contributing to the fatalities were the immediate, intense fire that resulted from the spillage of fuel upon impact from the fuel tanks that were not crash resistant, the separation from the floor of the cabin seats that were not crash resistant, and the use of an inappropriate release mechanism on the cabin seat restraints.
As a result of this investigation, the National Transportation Safety Board makes the following safety recommendations to the Federal Aviation Administration:
- Require that the hover performance charts published by helicopter manufacturers reflect the true performance of the helicopter in all conditions for which the charts are applicable, including light and variable wind conditions.
- Develop and implement a surveillance program specifically for 14 Code of Federal Regulations (CFR) Part 135 operators with aircraft that can operate both as public aircraft and as civil aircraft to maintain continual oversight ensuring compliance with 14 CFRPart 135 requirements.
- Take appropriate actions to clarify Federal Aviation Administration (FAA) authority over public aircraft, as well as identify and document where such oversight responsibilities reside in the absence of FAA authority.
- Require the installation of fuel tanks that meet the requirements of 14 Code of Federal Regulations 29.952 on S-61 helicopters that are used for passenger transport.
- Require that S-61 helicopters that are used for passenger transport be equipped with passenger seats and seat mounting structures that provide substantial improvement over the requirements of Civil Air Regulations 7.260, such as complying with portions of 14 Code of Federal Regulations 29.561 and 29.562.
- Require operators of transport-category helicopters to equip all passenger seats with restraints that have an appropriate release mechanism that can be released with minimal difficulty under emergency conditions.
- Require that Advisory Circular 21-34 be used to evaluate all shoulder harness retrofit installations and to determine that the installations reduce the risk of occupant injury.
- Require operators of Sikorsky S-61 helicopters with General Electric model CT58-140 engines to install 10-micron airframe fuel filters.
- Require Carson Helicopters, Inc., to put a conspicuous notification on the title page of the Instructions for Continuing Airworthiness that accompany its supplemental type certificate for installing side-mounted seats indicating that the installation does not provide enhanced occupant protection over that provided by the originally installed seats and meets Civil Air Regulations 7.260 standards.
- Require all applicants for supplemental type certificate (STC) seat installations in any type of aircraft to put a conspicuous notification on the title page of the Instructions for Continuing Airworthiness that accompany the STC indicating whether the installation provides enhanced occupant protection over that provided by the originally installed seats and the certification standard level met by the seating system.
- Require supplemental type certificate (STC) applicants to improve the crashworthiness design of the seating system, such as complying with portions of 14 Code of Federal Regulations 29.561 and 29.562, when granting STC approval for older transport-category rotorcraft certificated to Civil Air Regulations 7.260 standards.
As a result of this investigation, the National Transportation Safety Board makes the following safety recommendations to the U.S. Forest Service:
- Develop mission-specific operating standards for firefighter transport operations that include procedures for completing load calculations and verifying that actual aircraft performance matches predicted performance, require adherence to aircraft operating limitations, and detail the specific Part 135 regulations that are to be complied with by its contractors.
- Require its contractors to conduct firefighter transport operations in accordance with the mission-specific operating standards specified in Safety Recommendation [#12].
- Create an oversight program that can reliably monitor and ensure that contractors comply with the mission-specific operating standards specified in Safety Recommendation [#12].
- Provide specific training to inspector pilots on performance calculations and operating procedures for the types of aircraft in which they give evaluations.
- Require that a hover-out-of-ground-effect power check is performed before every takeoff carrying passengers from helispots in confined areas, pinnacles and ridgelines.
- Review and revise policies regarding the type and use of gloves by firefighting personnel during transport operations, including, but not limited to, compatibility with passenger restraints and opening emergency exits.
- Review and revise your contract requirements for passenger transport by aircraft so that the requirement to install shoulder harnesses on passenger seats provides improved occupant crashworthiness protection consistent with the seat design.
- Require that helispots have basic weather instrumentation that has the capability to measure wind speed and direction, temperature, and pressure and provide training to helitack personnel in the proper use of this instrumentation.
- Modify your standard manifest form to provide a place to record basic weather information and require that this information be recorded for each flight.
- Require all contracted transport-category helicopters to be equipped with a cockpit voice recorder and a flight data recorder or a cockpit image recorder with the capability of recording cockpit audio, crew communications, and aircraft parametric data.
Previously Issued Recommendation Reiterated in this Report
The National Transportation Safety Board reiterates the following safety recommendation to the Federal Aviation Administration:
Do not permit exemptions or exceptions to the flight recorder regulations that allow transport-category rotorcraft to operate without flight recorders, and withdraw the current exemptions and exceptions that allow transport-category rotorcraft to operate without flight recorders. (A-06-18)