Recommendation

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.