Source: https://www.federalregister.gov/documents/2007/06/11/E7-11153/special-conditions-boeing-model-787-8-airplane-crashworthiness
Timestamp: 2017-09-24 23:31:03
Document Index: 369299445

Matched Legal Cases: ['art 25', '§\u200925', 'art 34', 'art 36', 'art 25', 'art 25', '§\u200925', '§\u200925', '§\u200925', '§\u200921', '§\u200925', '§\u200925']

Federal Register :: Special Conditions: Boeing Model 787-8 Airplane; Crashworthiness
A Proposed Rule by the Federal Aviation Administration on 06/11/2007
Comments must be received on or before July 26, 2007.
72 FR 32021
Docket No. NM368 Special Conditions No. 25-07-05-SC
E7-11153
Discussion of Proposed Special Condition
https://www.federalregister.gov/d/E7-11153 https://www.federalregister.gov/d/E7-11153
This notice proposes special conditions for the Boeing Model 787-8 airplane. This airplane will have novel or unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. These novel or unusual design features are associated with carbon fiber reinforced plastic used in the construction of the fuselage. For these design features, the applicable airworthiness regulations do not contain adequate or appropriate safety standards for impact response characteristics to ensure survivable crashworthiness. These proposed special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. Additional special conditions will be issued for other novel or unusual design features of the Boeing 787-8 airplanes.
Comments on this proposal may be mailed in duplicate to: Federal Aviation Administration, Transport Airplane Directorate, Attention: Rules Docket (ANM-113), Docket No. NM368, 1601 Lind Avenue SW., Renton, Washington 98057-3356; or delivered in duplicate to the Transport Airplane Directorate at the above address. All comments must be marked Docket No. NM368. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
Ian Won, FAA, Airframe/Cabin Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone (425) 227-2145; facsimile (425) 227-1320.
We will file in the docket all comments we receive as well as a report summarizing each substantive public Start Printed Page 32022contact with FAA personnel concerning these proposed special conditions. The docket is available for public inspection before and after the comment closing date. If you wish to review the docket in person, go to the address in the ADDRESSES section of this notice between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal holidays.
On March 28, 2003, Boeing applied for an FAA type certificate for its new Boeing Model 787-8 passenger airplane. The Model 787-8 airplane will be an all-new, two-engine jet transport airplane with a two-aisle cabin. The maximum takeoff weight will be 476,000 pounds, with a maximum passenger count of 381 passengers.
Under provisions of 14 CFR 21.17, Boeing must show that Model 787-8 airplanes (hereafter referred to as “the 787”) meet the applicable provisions of 14 CFR part 25, as amended by Amendments 25-1 through 25-117, except §§ 25.809(a) and 25.812, which will remain at Amendment 25-115. If the Administrator finds that the applicable airworthiness regulations do not contain adequate or appropriate safety standards for the 787 airplane because of a novel or unusual design feature, special conditions are prescribed under provisions of 14 CFR 21.16.
In addition to the applicable airworthiness regulations and special conditions, the 787 airplane must comply with the fuel vent and exhaust emission requirements of 14 CFR part 34 and the noise certification requirements of part 36. In addition, the FAA must issue a finding of regulatory adequacy pursuant to section 611 of Public Law 92-574, the “Noise Control Act of 1972.”
The 787 airplane will incorporate a number of novel or unusual design features. Because of rapid improvements in airplane technology, the applicable airworthiness regulations do not contain adequate or appropriate safety standards for these design features. These proposed special conditions for the 787 contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.
The 787 fuselage will be fabricated with carbon fiber reinforced plastic (CFRP) semi-monocoque construction, consisting of skins with co-cured longitudinal stringers and mechanically fastened circumferential frames. This is a novel and unusual design feature for a large transport category airplane certificated under 14 CFR part 25. Structure fabricated from CFRP may behave differently than metallic structure because of differences in material ductility, stiffness, failure modes, and energy absorption characteristics. Therefore, impact response characteristics of the 787 must be evaluated to ensure that its survivable crashworthiness characteristics provide approximately the same level of safety as those of a similarly sized airplane fabricated from traditionally used metallic materials.
The FAA and industry have been working together for many years to understand how transport airplane occupant safety can be improved for what are considered survivable accidents. This work has involved examining airplane accidents, conducting tests to simulate crash conditions, and performing analytical modeling of a range of crash conditions, all with the purpose of providing further insight into factors that can influence occupant safety. Results of this on-going effort have enabled specific changes to regulatory standards and design practices to improve occupant safety. This evolution is reflected in changes to the part 25 Emergency Landing Conditions regulations. For example, airplane emergency load factors in § 25.561, General, have been increased. Passenger seat dynamic load conditions have been added (§ 25.562, Emergency Landing Dynamic Conditions).
The seat dynamic conditions were added to the regulations based on FAA and industry tests and a review of accidents. These seat dynamic conditions reflect the environment for passengers and the airframe during a crash event. They are based on data gathered from accidents of previously certificated airplanes given conditions that were survivable. Tests of previously certificated airplanes demonstrated that performance of the airframe was acceptable in a survivable crash event. We continually update our requirements as such new information becomes available. In the context of this evolution of the regulations, there is at present no specific dynamic regulatory requirement for airplane-level crashworthiness. However, the FAA reviews the design of each new airplane model to determine if it incorporates novel or unusual design features that may have a significant influence on the crash dynamics of the airframe. The Administrator prescribes special conditions for the airplane model if the applicable airworthiness regulations do not contain adequate or appropriate safety standards because of the novel or unusual design feature. Because of the novel design features of the 787, the FAA intends to require Boeing to conduct an assessment to ensure that the 787 will not have dynamic characteristics that differ significantly from those found in previously certificated designs.
The nature of this proposed design assessment is largely dependent on the similarities and differences between the new type design and previously certificated airplanes. Such an assessment ensures that the level of safety of the new type design is commensurate with that implicitly assumed in the existing regulations, and achieved by airplane designs previously certificated. If significant trends in industry warrant change to the existing regulations, the FAA may use its rulemaking process in collaboration with industry to develop an appropriate dynamic regulatory requirement for airplane level crashworthiness.
The FAA and industry have collected a significant amount of experimental data as well as data from crashes of transport category airplanes that demonstrates a high occupant survival rate at vertical descent velocities up to 30 ft/sec. The majority of this data was collected on narrow-body (single aisle) transport category airplanes. Based on this information, the FAA finds it appropriate and necessary for an assessment of the 787 to span a range of Start Printed Page 32023airplane vertical descent velocities up to 30 ft/sec.
The FAA is proposing this special condition to maintain the level of safety envisioned in the existing airworthiness standards under foreseeable survivable impact events.
In order to provide the same level of safety as exists with conventional airplane construction, Boeing must demonstrate that the 787 has sufficient crashworthiness capabilities under foreseeable survivable impact events. To demonstrate this, Boeing would have to evaluate the impact response characteristics of the 787 to ensure that its crashworthiness characteristics are not significantly different from those of a similarly sized airplane fabricated from traditionally used metals. If the evaluation shows that the 787 impact response characteristics are significantly different, Boeing would have to make design changes to bring the different impact response characteristics in line with those of a similarly sized metal construction airplane, or incorporate mitigating design features.
Factors in crash survivability are retention of items of mass, maintenance of occupant emergency egress paths, maintenance of acceptable acceleration and loads experienced by the occupants, and maintenance of a survivable volume. In reviewing available data from accidents, tests simulating crash conditions, and analytical modeling of a range of crash conditions, the FAA has concluded that the airplane performance should be evaluated over a range of airplane level vertical impact velocities up to 30 ft/sec.
If the 787 impact characteristics differ significantly from those of a previously certificated wide body transport, this would result in a need to meet load factors higher than those defined in 14 CFR 25.561 in order to maintain the same level of safety for the occupants, in terms of retention of items of mass. In the cases of acceleration and loads experienced by the occupants, means would have to be incorporated to reduce load levels experienced by those occupants to the injury criteria levels of § 25.562, or load levels of a previously certificated comparable airplane, in order to maintain the same level of safety for the occupants.
As discussed above, these proposed special conditions are applicable to the 787 airplane. Should Boeing apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design features, these proposed special conditions would apply to that model as well under the provisions of § 21.101.
This action affects only certain novel or unusual design features of the 787 airplane. It is not a rule of general applicability.
The Boeing Model 787-8 must provide an equivalent level of occupant safety and survivability to that provided by previously certificated wide-body transports of similar size under foreseeable survivable impact events for the following four criteria. In order to demonstrate an equivalent level of occupant safety and survivability, the applicant must demonstrate that the Model 787-8 meets the following criteria for a range of airplane vertical descent velocities up to 30 ft/sec.
1. Retention of items of mass. The occupants, i.e., passengers, flight attendants and flightcrew, must be protected during the impact event from release of seats, overhead bins, and other items of mass due to the impact loads and resultant structural deformation of the supporting airframe and floor structures. The applicant must show that loads due to the impact event and resultant structural deformation of the supporting airframe and floor structure at the interface of the airplane structure to seats, overhead bins, and other items of mass are comparable to those of previously certificated wide-body transports of similar size for the range of descent velocities stated above. The attachments of these items need not be designed for static emergency landing loads in excess of those defined in § 25.561 if impact response characteristics of the Boeing Model 787-8 yield load factors at the attach points that are comparable to those for a previously certificated wide-body transport category airplane.
2. Maintenance of acceptable acceleration and loads experienced by the occupants. The applicant must show that the impact response characteristics of the 787, specifically the vertical acceleration levels experienced at the seat/floor interface and loads experienced by the occupants during the impact events, are consistent with those found in § 25.562(b) or with levels expected for a previously certificated wide-body transport category airplane for the conditions stated above.
3. Maintenance of a survivable volume. For the conditions stated above, the applicant must show that all areas of the airplane occupied for takeoff and landing provide a survivable volume comparable to that of previously certificated wide-body transports of similar size during and after the impact event. This means that structural deformation will not result in infringement of the occupants' normal living space so that passenger survivability will not be significantly affected.
4. Maintenance of occupant emergency egress paths. The evacuation of occupants must be comparable to that from a previously certificated wide-body transport of similar size. To show this, the applicant must show that the suitability of the egress paths, as determined following the vertical impact events, is comparable to the suitability of the egress paths of a comparable, certificated wide-body transport, as determined following the same vertical impact events.
Issued in Renton, Washington, on May 31, 2007.
[FR Doc. E7-11153 Filed 6-8-07; 8:45 am]