E8-27541. Special Conditions: Airbus A318, A319, A320 and A321 Series Airplanes; Inflatable Restraints

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions; request for comments.

SUMMARY:

These special conditions are issued for the Airbus A318, A319, A320, and A321 series airplanes. These airplanes will have a novel or unusual design feature associated with a passenger restraint system that contains an integrated inflatable airbag installed on passenger seats. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These 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.

DATES:

The effective date of these special conditions is November 12, 2008. We must receive your comments by January 5, 2009.

ADDRESSES:

You must mail two copies of your comments to: Federal Aviation Administration, Transport Airplane Directorate, Attn: Rules Docket (ANM-113), Docket No. NM394, 1601 Lind Avenue, SW., Renton, Washington 98057-3356. You may deliver two copies to the Transport Airplane Directorate at the above address. You must mark your comments: Docket No. NM394. You can inspect comments in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT:

Dan Jacquet, FAA, Airframe and Cabin Safety Branch, ANM-115, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; facsimile [phone].

SUPPLEMENTARY INFORMATION:

The FAA has determined that notice and opportunity for prior public comment hereon are impracticable because these procedures would significantly delay issuance of the design approval and thus delivery of the affected aircraft. In addition, the substance of these special conditions has been subject to the public comment process in several prior instances with no substantive comments received. The FAA therefore finds that good cause exists for making these special conditions effective upon issuance.

Comments Invited

We invite interested people to take part in this rulemaking by sending written comments, data, or views. The most helpful comments reference a specific portion of the special conditions, explain the reason for any recommended change, and include supporting data. We ask that you send us two copies of written comments.

We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel about these special conditions. You can inspect the docket 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 preamble between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal holidays.

We will consider all comments we receive by the closing date for comments. We will consider comments filed late if it is possible to do so without incurring expense or delay. We may change these special conditions based on the comments we receive.

If you want us to let you know we received your comments on these special conditions, send us a pre-addressed, stamped postcard on which the docket number appears. We will stamp the date on the postcard and mail it back to you.

Background

On September 2, 2008, Airbus, 1 Rond-Point Maurice Bellonte, 31707 Blagnac, Cedex, France, applied for an amendment to Type Certificate No. A28NM to install the AmSafe Aviation Inflatable Restraint (AAIR) for head injury protection on passenger seats on Airbus A318, A319, A320 and A321 series airplanes. The AAIR is designed to limit passenger forward excursion in the event of an accident, thus reducing the potential for head injury (and head entrapment).

The AAIR behaves like an automotive inflatable airbag except that the airbag is integrated into the passenger restraint system and inflates away from the seated passenger. While inflatable airbags are standard in the automotive industry, the use of an inflatable passenger restraint system is novel for commercial aviation.

Title 14, Code of Federal Regulations (14 CFR) 25.785 requires that passengers be protected from head injury by either the elimination of any injurious object within the striking radius of the head or by padding. Traditionally, compliance has required either a setback of 35 inches from any bulkhead, front seat or other rigid interior feature or padding where a setback was not practical. The relative effectiveness of these two means of injury protection was not quantified. The adoption of Amendment 25-64 to 14 CFR part 25, specifically § 25.562, created a new standard for protection from head injury. Airbus elected to comply with § 25.562, except for § 25.562(c)(5) (protection from head injury) and § 25.562(c)(6) (protection from femur injury), for the Airbus A318, A319, and A321 series airplanes. The pertinent parts of § 25.562 for these airplanes require that dynamic tests be conducted for each seat type installed in the airplane, and that each seat type meets certain performance measures. Although the head injury protection requirements of § 25.562(e)(5) are not part of the certification basis for the affected airplanes, it is relevant for future compliance with § 121.311(j). This regulation will require full compliance with § 25.562 for airplanes manufactured on or after October 27, 2009.

Because §§ 25.562 and 25.785 do not adequately address seats with AAIRs, the FAA recognizes that we need to develop appropriate pass/fail criteria that do address the safety of occupants of those seats. These special conditions are applicable to inflatable restraint systems in general. However, because this initial application is for the AAIR, the following discussion refers specifically to the AAIR.

The AAIR has two potential advantages over other means of head impact protection. The first is that it can provide significantly greater protection than would be expected with energy-absorbing pads; the second is that it can provide essentially equivalent protection for occupants of all stature. These are significant advantages from a safety standpoint, since such devices will likely provide a level of safety that exceeds the minimum part 25 standards.

On the other hand, AAIRs are active systems and must activate properly when needed, as opposed to an energy-absorbing pad or upper torso restraint that is passive and always available. Therefore, the potential advantages must be balanced against potential disadvantages in order to develop standards that will provide an equivalent level of safety to that intended by the regulations.

There are two primary safety concerns with the use of AAIRs: (1) They perform properly under foreseeable operating conditions, and (2) they do not perform in a way that would constitute a hazard to the airplane or occupants. This latter point has the potential to be the more rigorous of the requirements, owing to the active nature of the system.

The AAIR will rely on electronic sensors for signaling and pyrotechnic charges for activation, so that it is available when needed. These same devices could be susceptible to inadvertent activation, causing deployment in a potentially unsafe manner. The consequences of such deployment must be considered in establishing the reliability of the system. Airbus must substantiate that the effects of an inadvertent deployment in flight are either not a hazard to the airplane or that such deployment is an extremely improbable occurrence (occurring less than 10^-9 per flight hour). The effect of an inadvertent deployment on a passenger sitting or standing close to the AAIR must also be considered. A minimum reliability level will have to be established for this case, depending upon the consequences, even if the effect on the airplane is negligible.

The potential for an inadvertent deployment could be increased as a result of conditions in service. The installation must take into account wear and tear, so that the likelihood of an inadvertent deployment is not increased to an unacceptable level. In this context, an appropriate inspection interval and self-test capability are necessary.

Other outside influences are lightning and high intensity radiated fields (HIRF). Since the sensors that trigger deployment are electronic, they must be protected from the effects of these threats. Existing regulations regarding lightning (§ 25.1316) and HIRF (§ 25.1317) are applicable in lieu of any other lightning and HIRF special conditions that have been adopted for the affected airplanes.

For the purposes of compliance, if inadvertent deployment could cause a hazard to the airplane, the AAIR is considered a critical system; if inadvertent deployment could cause injuries to persons, the AAIR is considered an essential system. Finally, the AAIR installation should be protected from the effects of fire, so that an additional hazard is not created by, for example, a rupture of a pyrotechnic squib.

In order to be an effective safety system, the AAIR must function properly and must not introduce any additional hazards to occupants as a result of its functioning. There are several areas where the AAIR differs from traditional occupant protection systems, and requires special conditions to ensure adequate performance.

Because the AAIR is essentially a single use device, there is the potential that it could deploy under crash conditions that are not sufficiently severe as to require head injury protection from the AAIR. Since an actual crash is frequently composed of a series of impacts before the airplane comes to rest, this could render the AAIR useless if a larger impact follows the initial impact. This situation does not exist with energy-absorbing pads or upper torso restraints, which tend to provide protection according to the severity of the impact. Therefore, the AAIR installation should be such that the AAIR will provide protection when it is required and will not expend its protection when it is not needed. There is no requirement for the AAIR to provide protection for multiple impacts, where more than one impact would require protection.

Since each passenger's restraint system provides protection for that occupant only, the installation must address seats that are unoccupied. It will be necessary to show that the required protection is provided for each occupant regardless of the number of occupied seats and considering that unoccupied seats may have AAIR that are active.

Since there is a wide range in the size of passengers, the AAIR must be effective over the entire range. The FAA has historically considered the range from the fifth percentile female to the ninety-fifth percentile male as the range of passengers to take into account. In this case, the FAA is proposing consideration of an even broader range of passengers, due to the nature of the AAIR installation and its close proximity to the passenger. In a similar vein, passengers may assume the brace position for those accidents where an impact is anticipated. Test data indicate that passengers in the brace position do not require supplemental protection, so that it will not be necessary to show that the AAIR will enhance the brace position. However, the AAIR must not introduce a hazard in that case by deploying into the seated, braced passenger.

Another area of concern is the use of seats occupied by children, whether lap-held, in approved child safety seats, or occupying the seat directly. Similarly, if the seat is occupied by a pregnant woman, the installation needs to address such usage, either by demonstrating that it will function properly, or by adding an appropriate limitation on usage.

Since the AAIR will be electrically powered, there is the possibility that the system could fail due to a separation in the fuselage. Since this system is intended as a means of protection in a crash or after a crash, failure due to fuselage separation is not acceptable. As with emergency lighting, the system should function properly, if such a separation occurs at any point in the fuselage.

Since the AAIR is likely to have a large volume displacement, the inflated bag could potentially impede egress of passengers. Since the bag deflates to absorb energy, it is likely that an AAIR would be deflated at the time that persons would be trying to leave their seats. Nonetheless, it is considered appropriate to specify a time interval after which the AAIR may not impede rapid egress. Ten seconds has been chosen as a reasonable time, since it corresponds to the maximum time allowed for an exit to be openable. In actuality, it is unlikely that an exit would be prepared this quickly in an accident severe enough to warrant deployment of the AAIR, and the AAIR will likely deflate much quicker than ten seconds.

The manufacturers of the inflatable lap belts have been unable thus far to develop a fabric that meets the inflation requirements for the bag and the flammability requirements of Part I(a)(1)(ii) of appendix F of part 25. The fabrics that have been developed that meet the flammability requirements did not produce acceptable deployment characteristics. However, the manufacturer was able to develop a fabric that meets the less stringent flammability requirements of Part I(a)(1)(iv) of appendix F to part 25 and has acceptable deployment characteristics.

Finally, it should be noted that the special conditions are applicable to the AAIR system, as installed. The special conditions are not an installation approval. Therefore, while the special conditions relate to each such system installed, the overall installation approval is a separate finding and must consider the combined effects of all such systems installed.

Type Certification Basis

Under the provisions of § 21.101, Airbus must show that the A318, A319, A320 and A321 series airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A28NM or the applicable regulations in effect on the date of application for the change. The regulations incorporated by reference in the type certificate are commonly referred to as the “original type certification basis.” The regulations incorporated for each individual airplane model are defined within Type Certificate Data Sheet (TCDS) A28NM.

In addition, the certification basis includes other regulations and special conditions that are not pertinent to these special conditions.

If the Administrator finds that the applicable airworthiness regulations (i.e., 14 CFR part 25) do not contain adequate or appropriate safety standards for the Airbus A318, A319, A320 and A321 series airplanes, because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

In addition to the applicable airworthiness regulations and special conditions, each airplane model must comply with the fuel vent and exhaust emission requirements of 14 CFR part 34 and the noise certification requirements of 14 CFR part 36.

The FAA issues special conditions, as defined in § 11.19, under § 11.38 and they become part of the type certification basis under § 21.101.

Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to include any other model that incorporates the same novel or unusual design feature, or should any other model included on the same type certificate be modified to incorporate the same novel or unusual design feature, the special conditions would also apply to the other model.

Novel or Unusual Design Features

The Airbus A318, A319, A320 and A321 series airplanes will incorporate the following novel or unusual design features: These airplanes as modified by Airbus will have a passenger restraint system that contains an integrated inflatable airbag device installed on passenger seats. The AAIR will be installed to reduce the potential for head injury in the event of an accident. The AAIR works like an automotive airbag, except that the airbag is integrated with the passenger restraint system. The AAIR is considered a novel design for transport category airplanes and was not considered as part of the original type certification basis.

Section 25.785 states the performance criteria for head injury protection in objective terms. However, none of these criteria are adequate to address the specific issues raised concerning seats with AAIR. The FAA has therefore determined that, in addition to the requirements of 14 CFR part 25, special conditions are needed to address requirements particular to installation of seats with AAIR.

Accordingly, in addition to the passenger injury criteria specified in § 25.785, these special conditions are adopted for the Airbus A318, A319, A320 and A321 series airplanes equipped with AAIR. Other conditions may be developed, as needed, based on further FAA review and discussions with the manufacturer and civil aviation authorities.

Discussion

From the standpoint of a passenger safety system, the airbag is unique in that it is both an active and entirely autonomous device. While the automotive industry has good experience with airbags, the conditions of use and reliance on the airbag as the sole means of injury protection are quite different. In automobile installations, the airbag is a supplemental system and works in conjunction with an upper torso restraint. In addition, the crash event is more definable and of typically shorter duration, which can simplify the activation logic. The airplane-operating environment is also quite different from automobiles and includes the potential for greater wear and tear, and unanticipated abuse conditions (due to galley loading, passenger baggage, etc.); airplanes also operate where exposure to high intensity electromagnetic fields could affect the activation system.

The following special conditions can be characterized as addressing either the safety performance of the system, or the system's integrity against inadvertent activation. Because a crash requiring use of the airbags is a relatively rare event, and because the consequences of an inadvertent activation are potentially quite severe, these latter requirements are probably the more rigorous from a design standpoint.

Applicability

As discussed above, these special conditions are applicable to Airbus A318, A319, A320 and A321 series airplanes. Should Airbus apply at a later date for a change to type certificate to include another model incorporating the same novel or unusual design feature, the special conditions would apply to that model as well.

Conclusion

This action affects only certain novel or unusual design features on Airbus A318, A319, A320 and A321 series airplanes. It is not a rule of general applicability.

The substance of these special conditions has been subjected to the notice and comment period in several prior instances and has been derived without substantive change from those previously issued. It is unlikely that prior public comment would result in a significant change from the substance contained herein. For this reason and because a delay would significantly affect the certification of the airplane, which is imminent, the FAA has determined that prior public notice and comment are unnecessary and impracticable and that good cause exists for adopting these special conditions upon issuance. The FAA is requesting comments to allow interested persons to submit views that may not have been submitted in response to the prior opportunities for comment described above.

List of Subjects in 14 CFR Part 25

• Aircraft
• Aviation safety
• Reporting and recordkeeping requirements

The authority citation for these special conditions is as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

Accordingly, pursuant to the authority delegated to me by the Administrator, the following special conditions are issued as part of the type certification basis for the Airbus A318, A319, A320 and A321 series airplanes, as modified by installation of inflatable restraints.

1. Seats with inflatable restraints. It must be shown that the inflatable restraints will deploy and provide protection under crash conditions where it is necessary to prevent serious head injury or head entrapment. The means of protection must take into consideration a range of stature from a two-year-old child to a ninety-fifth percentile male. The inflatable restraints must provide a consistent approach to energy absorption throughout that range. In addition, the following situations must be considered:

(a) The seat occupant is holding an infant.

(b) The seat occupant is a child in a child restraint device.

(c) The seat occupant is a child not using a child restraint device.

(d) The seat occupant is a pregnant woman.

2. The inflatable restraints must provide adequate protection for each occupant regardless of the number of occupants of the seat assembly, considering that unoccupied seats may have active seatbelts.

3. The design must prevent the inflatable restraints from being either incorrectly buckled or incorrectly installed such that the inflatable restraints would not properly deploy. Alternatively, it must be shown that such deployment is not hazardous to the occupant and will provide the required head injury protection.

4. It must be shown that the inflatable restraints system is not susceptible to inadvertent deployment as a result of wear and tear or inertial loads resulting from in-flight or ground maneuvers (including gusts and hard landings), likely to be experienced in service.

5. Deployment of the inflatable restraints must not introduce injury mechanisms to the seated occupant or result in injuries that could impede rapid egress. This assessment should include an occupant who is in the brace position when it deploys and an occupant whose belt is loosely fastened.

6. It must be shown that an inadvertent deployment that could cause injury to a standing or sitting person is improbable.

7. It must be shown that inadvertent deployment of the inflatable restraints, during the most critical part of the flight, will either not cause a hazard to the airplane or is extremely improbable.

8. It must be shown that the inflatable restraints will not impede rapid egress of occupants 10 seconds after its deployment.

9. If lithium non-rechargeable batteries are used to power the inflatable restraints, the batteries must be DO-227 and UL compliant. However, if rechargeable lithium batteries are used, additional special conditions may apply.

10. The inflatable restraints must function properly after loss of normal airplane electrical power and after a transverse separation of the fuselage at the most critical location. A separation at the location of the lap belt does not have to be considered.

11. It must be shown that the inflatable restraints will not release hazardous quantities of gas or particulate matter into the cabin.

12. The inflatable restraints installation must be protected from the effects of fire such that no hazard to occupants will result.

13. The system must be protected from lightning and HIRF. The threats specified in Special Conditions No. 25-ANM-23 are incorporated by reference for the purpose of measuring lightning and HIRF protection. For the purposes of complying with HIRF requirements, the inflatable lapbelt system is considered a critical system if its deployment could have a hazardous effect on the airplane; otherwise it is considered an essential system.

14. There must be a means for a crewmember to verify the integrity of the inflatable restraints activation system prior to each flight or it must be demonstrated to reliably operate between inspection intervals.

15. The inflatable material may not have an average burn rate of greater than 2.5 inches/minute when tested using the horizontal flammability test as defined in 14 CFR part 25, appendix F, part I, paragraph (b)(5).

Issued in Renton, Washington, on November 12, 2008.

Stephen P. Boyd,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.