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Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R19980281
Date issued: 31 March 1999
Safety action status:
Background:

SUBJECT - PASSENGER SEAT UPPER-BODY RESTRAINT


SAFETY DEFICIENCY

Aeroplanes certified under United States, Federal Aviation Regulation (FAR) part 23 that are used for fare-paying passenger flights might not have all passenger seats fitted with harnesses that provide upper body restraint.

Note: FAR part 23 aircraft are broadly defined as light aircraft (small airplanes).


FACTUAL INFORMATION

Occurrence summary

On Sunday, 26 July 1998, at about 1324 EST, a Cessna A185E floatplane crashed onto a ridge forming the southern shore of Calabash Bay, NSW. The accident occurred during a go-around manoeuvre following an unsuccessful landing approach to the Berowra water alighting area. At the time of the accident, the Calabash Bay area was affected by strong winds, widespread rain and showers, low cloud, and reduced visibility. The aircraft was undertaking a charter flight from Palm Beach to Berowra. All five occupants, including the pilot, suffered fatal injuries. The aircraft was destroyed by impact forces.


Crew and passenger restraint

The aircraft cabin contained six seating positions, in two rows of dual seats and a rear two-place bench seat. The pilot and front seat passenger seats were fitted with both lap belts and shoulder restraints. The remaining four passenger seats were fitted with lap belts only. Four of the five occupants died immediately on impact. A passenger occupying the left rear bench seat died at the scene shortly after. The right rear bench seat was unoccupied.

During the impact sequence, the pilot and front seat passenger lap belts remained fastened. However, neither was wearing their respective shoulder restraint. The second row left seat outboard seat-belt stitching had failed at the belt end fitting. The end fitting was locked in the buckle and the inboard belt was intact. The right seatbelt was unlocked and the right outboard belt anchor point had been torn from the aircraft structure as a result of overload failure.

The second row inboard seat belts were attached to the floor structure using a single attachment point instead of individual attachments. This modification did not use either of the two attachment points fitted to the aircraft by the manufacturer.

The left seat belt of the rear bench seat was fastened, however, the inboard belt anchor bolt had failed in overload. The investigation found that the anchor bolt was not the correct part. Metallurgical examination found that although the bolt was of lower strength than the correct part, its strength was sufficient to meet the aircraft design specifications.


Specialist post-mortem examination

A specialist post-mortem examination of the pattern of injuries sustained by the occupants suggested that the failure of the lap restraints in the second row and rear seats would have allowed the occupants of those seats to be projected forward, onto the seats in front. This cascade effect could have been initiated by the failure of the rear seat-belt mounting, consequently contributing to the progressive loadings on the seats and occupants in front. The type and severity of injuries sustained suggested that, had adequate lap belt and upper body restraint been fitted and worn, such restraints would have aided survivability.


Other related occurrences

An accident involving a Cessna 172 in New Zealand in July 1990 claimed the lives of three occupants and seriously injured another. The Transport Accident Investigation Commission reported that the accident was survivable. The report stated that, "had the rear seat occupants had upper-restraint harnesses available, and worn them, it is likely that they both would have survived". It also stated that "the rear-seat occupants may have contributed to the pilot's injuries by the addition of their momentum to the load on the pilot's restraint systems".

Following an accident involving a DHC-2 (Beaver) in Canada, in which only one of the six occupants survived, the Transportation Safety Board deemed the accident to have been survivable. It concluded that if all seat belts had been anchored to the airframe (instead of the seats), and if shoulder harnesses had been installed and used, more of the aircraft occupants would have survived.

Research has shown that shoulder harnesses provide substantial injury protection against impact forces, in some cases up to six times greater than that provided by a lap belt. Evidence from accident investigations suggested that occupants without upper body restraint might have received disabling injuries that prevented them escaping from burning or sinking wreckage.


Installation requirements

There was no regulatory requirement for the C185E floatplane to be fitted with upper body restraint to other than the front row of seats. In December 1985, an amendment to the US Federal Aviation Regulations (FAR) part 23.2 required all aircraft in this category with less than nine passenger seats, manufactured after 12 December 1986, to have each seat fitted with a safety belt and shoulder harness. Australian-registered aircraft were similarly required by the then Civil Aviation Authority (CAA), to comply with Airworthiness Directive AD/General/67 "Passenger Safety Harnesses", by 31 July 1989.

Neither the US Federal Aviation Administration (FAA) nor the CAA required retrospective application of this AD. The effectiveness of an improved restraint system in aircraft manufactured before 12 December 1986 could not be guaranteed because of the possible design inadequacies of the seats and aircraft structures. This was a significant problem with the seats installed in many cabin-class multi-engine aeroplanes. Some manufacturers chose to make available modification kits to some of their existing aircraft fleets in order that owners could upgrade their aircraft to meet the amended safety standard.

An inspection of the Australian aircraft register revealed that the majority of light aircraft (FAR Part 23 certified) in Australia were manufactured prior to 12 December 1986. The major US aircraft manufacturers had ceased light aircraft production in the early to mid-1980s. Consequently, the protection afforded to passengers by the requirement for the provision of upper body restraint has not been extensively provided. Anecdotal evidence suggests that only a small percentage of these aircraft engaged in fare-paying passenger operations in this country meet the amended safety standard (FAR 23.2).

Manufacturers' instructions

On 4 September 1992, the Cessna Aircraft Company issued Single Engine Service Bulletin SEB92-28 "Seat belt and shoulder harness installation", which was applicable to all single-engine Cessna aeroplanes including the C185E. An installation kit for the seat belt and shoulder harness assembly for all passenger seats in these aircraft was available for purchase from the manufacturer. The service bulletin stated compliance was mandatory within the next 400 hours of aircraft operation or 12 months.

The mandatory requirement for compliance with manufacturers' service bulletins is driven by warranty and product liability issues and not necessarily by certification criteria. Determination of the applicability of compliance with service bulletins was that of the regulatory authority, in this case the US FAA. The FAA did not issue an Airworthiness Directive that would have mandated compliance with these service bulletins or instructions. In Australia, the CAA adopted the decision of the original certifying authority in accordance with their policy at the time.

An inspection of other US light aircraft manufacturers revealed the availability of similar installation kits. Piper Aircraft Corporation issued Service Bulletin No. 896 on 28 November 1988, mandating the installation of shoulder harness kits within one calendar year of the date of issue of the service bulletin. The applicable aeroplane models were all the Cherokee range of single-engine aircraft, including the derivatives- Arrow, Lance and Saratoga, the Malibu and the multi-engine Seneca and Seminole aircraft. Beechcraft issued Service Instruction No. 1020 "Notice of availability of shoulder harness kits", mandating the installation of the kits at the earliest opportunity, to all seats on their entire product range of single and multi-engine aircraft. In some instances this required the replacement of the existing seating with redesigned items.

General inquiries suggested that a small number of kits were imported at the time the service bulletins were issued. Most of these kits were installed in aircraft held at the time by distributors. Only a few aircraft owners wishing to provide greater protection for their passengers have since installed these kits.


Correct use of harness

The instructions provided by manufacturers in their service bulletins incorporated notes on the correct use of lap belts and shoulder harnesses. In its service bulletin, Piper stated that "the owner and/or operator should as standard procedure, use the shoulder harness and lap belt restraint systems and should advise all passengers and crew to use their systems, providing instruction for use as necessary". The Cessna service bulletin required the following placard to be displayed at each seat location:

"WARNING: Failure to install and properly utilize seat belts and shoulder harnesses could result in serious or fatal injury in the event of an accident."

In its "Safety Study of Survivability in Seaplane Accidents" (Report Number SA9401) the Transportation Safety Board of Canada stated, that "Failure to successfully exit a sinking aircraft is common for persons who suffer a trauma sustained because of a lack of appropriate restraint at the time of the accident. Yet, few occupants of seaplanes involved in water-accidents had taken advantage of available upper-torso restraint. Even pilots, who are more aware of the importance of being adequately restrained during an accident, and who are responsible for assisting survivors to exit the stricken aircraft after an accident, were often not using the shoulder harnesses that were available". This would be equally applicable to egress from a landplane following a ditching or an aircraft on fire following an accident.


Comparison with passenger vehicle requirements

By way of comparison, the requirement for upper body restraint (three-point harness) for rear-seat occupants in motor vehicles was introduced in accordance with Australian Design Rule (ADR) 5A. This was applicable to all new vehicles certified after 1 January 1971. A requirement for coaches greater than 5 tonnes to be fitted with upper body restraint for all occupants was introduced on 1 July 1994 by ADR 68/00.

As with many airworthiness directives, ADRs are not retrospectively applied. However, the much greater attrition rates for motor vehicles, compared to aircraft, means that compliance is achieved in a much shorter period.


ANALYSIS

The decision to not make the amendment to FAR Part 23 retrospective was based on the consideration that some existing airframes did not allow for the ready installation of shoulder harnesses without significant redesign and modification. It was assumed that with the normal replacement of aircraft fleets, the majority of aircraft would, in time, be fitted with this restraint system. However, the almost complete cessation of light aircraft production about the time the regulation was introduced resulted in fewer new aeroplanes, and as a consequence, fewer aeroplanes that met the certification standard being introduced into the existing fleets. Consequently, the intent of the regulation has not been as broadly encompassing as was originally envisaged.

Despite the availability of kits from most of the large manufacturers that enable aircraft owners to incorporate upper body restraint for all the passenger seats in many of the aircraft manufactured prior to the 12 December 1986, very few have been modified. The decision to install additional occupant protection was not mandated by an Airworthiness Directive. This allowed the decision to modify the restraint systems to be determined on a cost-benefit basis by each individual aircraft owner and/or operator, depending upon how they viewed their responsibilities and duty of care to their passengers.


Conclusion

Research has shown that upper body restraint can provide substantial injury protection against impact forces and in some instances increase injury tolerance by up to six times that provided by a lap belt alone.

The provision of upper body restraint to all passengers in FAR part 23 aircraft has not been effective through the normal process of fleet attrition and replacement, as originally envisaged by the responsible regulatory authorities. Retrospective application was not mandated, for technical and economic reasons, even though manufacturers made available seat belt and harness installation kits for many of their previous models. Voluntary installation of kits by Certificate of Registration holders (aircraft owners) has not been widely adopted. This has resulted in the majority of the affected fare-paying passenger aircraft being operated without upper body restraint for all occupants, despite the safety enhancement that can be readily achieved by such modification.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority mandate the compliance of all manufacturers' service bulletins relating to the provision of upper body restraint to occupants of FAR part 23 certified aircraft engaged in fare-paying passenger operations, and emphasise compliance with their instructions on the correct use of the restraint systems.

Initial response
Date issued: 04 August 1999
Response from: Civil Aviation Safety Authority
Action status: Open
Response text:

The value of upper body restraint in improving the chances of occupant survival following an aircraft impact is supported by both accident analysis and research testing. Australia has long been in the forefront of advocating the use of shoulder harnesses in both aircraft and road vehicles.

Any requirement for retrospective installation of shoulder harnesses in older small aircraft would be an Australian unique requirement, and as such CASA would need to conduct formal consultation with the industry. However, there are standard modification kits available for the most common types, but some design effort will be required for some aircraft types. Mandating the installation of upper body restraint in small aircraft would require substantiation to support the proposed rule. CASA therefore intends to gather the appropriate accident, research data and cost data to determine if the requirement can be justified in an NPRM.

CASA Airworthiness Branch, will be researching this issue.

Further correspondence
Date issued: 08 October 2001
Response from: Civil Aviation Safety Authority
Response status: Monitor
Response text:

On 8 October 2001, CASA advised that a draft discussion paper (DP 0109CS) had been prepared that was propsoing a requirement that all small aircraft that carry fare paying passengers be fitted with a shoulder restraint in all seats occupied for takeoff or landing. The DP was being processed through the Standards Coordination Branch of the Aviation Standards Division.

ATSB Note: In December 2001, CASA published Discussion Paper DP 0109CS "Proposed Airworthiness Directive, General Series - Upper torso Restraints for Occupants in Small Aircraft" for industry comment by 1 March 2002.

Further correspondence
Date issued: 26 July 2002
Response from: Civil Aviation Safety Authority
Response status: Closed - Accepted
Response text:

Following the crash of Cessna A185E VH-HTS while operating a charter operation north of Sydney in 1998, the Bureau of Air Safety Investigation issued safety Recommendation 8980281 which recommended that CASA "mandate the compliance of all manufacturers' Service Bulletins relating to the provision of upper body restraint to the occupants of FAR part 23 certified aircraft engaged in fare-paying passenger operations, and emphasise compliance with their instructions on the correct use of the restraint systems."

A research of safety benefits of shoulder harnesses confirmed the significant improvement in occupant protection, particularly in small aircraft where the impact loads transmitted to the occupant could be more severe than for a potentially survivable large transport aircraft crash. However, this benefit would be applicable to occupants in all small aircraft regardless of whether the aircraft manufacturer had issued a Service Bulletin. Therefore, for consistency, CASA believed that, if appropriate, the requirement should be applied to all aircraft types not exceeding 5700 kg MTOW. In December 2001 CASA published Discussion Paper DP 0109CS proposing a shoulder harness at each seat occupied during take-off or landing in all aircraft with a maximum takeoff weight not greater than 5700kg which are used to carry fare-paying passengers. Comments were requested by 1 March 2002.

Fifty-one responses to the Discussion Paper were received by CASA. Seventeen responses were clearly in favour of the proposal and 14 were clearly opposed. A common theme was that the cost of installation of shoulder harnesses in some aircraft would be significant. For example, at least one respondent advised that the cost to modify a Piper PA 31 aircraft in accordance with the Piper Service Bulletin would be approximately $100,000. Implementation in some aircraft would necessitate replacement of seats, and in some of those it is conceivable that floor strengthening would be required. For all aeroplanes whose type certification basis was set before 1985 (1989 for helicopters) the requirement proposed in the Discussion Paper would be unique to Australia and additional to the type certification basis.

In view of the difficulty of estimating the true costs and benefits, CASA believes that proceeding with a comprehensive benefit-cost analysis is not warranted. In light of the significant costs CASA believes that action to mandate installation of shoulder harnesses in Australian aircraft carrying fare-paying passengers cannot be justified. Therefore CASA does not intend to proceed further with the proposal covered by Discussion Paper DP 0109CS. A Summary of Responses will be prepared and distributed.

The installation and use of shoulder harnesses for all occupants in small aircraft will be strongly recommended to operators and the travelling public, and CASA will publicise the benefits of shoulder harnesses in this class of aircraft. This will be done in the expectation that the air-travelling public will become aware of the desirability of shoulder harnesses; and operators who can make this modification without threatening their economic viability will consider doing so.

ATSB response:

While acknowledging the efforts of the Civil Aviation Safety Authority in responding to this recommendation, the Australian Transport Safety Bureau will continue to monitor occurrences involving occupant restraints.

 
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Last update 01 April 2011