Special Conditions: Boeing, Model 747-8 Series Airplanes; Door 1 Extendable Length Escape Slide

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions.

SUMMARY:

These special conditions are issued for Boeing Model 747-8 airplanes. These airplanes will have a novel or unusual design feature associated with an extendable length escape slide. 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. Additional special conditions will be issued for other novel or unusual design features of Boeing 747-8 airplanes.

DATES:

Effective Date: August 1, 2011.

FOR FURTHER INFORMATION CONTACT:

Jayson Claar, FAA, Airframe and Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue, SW, Renton, Washington 98057-3356; telephone (425) 227-2194; facsimile (425) 227-1232.

SUPPLEMENTARY INFORMATION:

Background

On November 4, 2005, The Boeing Company, PO Box 3707, Seattle, WA, 98124, applied for an amendment to Type Certificate Number A20WE to include the new Model 747-8 series passenger airplane. Boeing later applied for, and was granted, an extension of time for the type certificate, which changed the effective application date to December 31, 2006. The Model 747-8 is a derivative of the 747-400. The Model 747-8 is a four-engine jet transport airplane that will have a maximum takeoff weight of 975,000 pounds, new General Electric GEnx -2B67 engines, and the capacity to carry 605 passengers.

Type Certification Basis

Under the provisions of Title 14, Code of Federal Regulations (14 CFR) 21.101, Boeing must show that the Model 747-8 (hereafter referred as 747-8) meets the applicable provisions of part 25, Amendments 25-1 through 25-120, plus Amendment 25-127 for § 25.795(a), except for earlier amendments as agreed upon by the FAA. These regulations will be incorporated into Type Certificate No. A20WE after type certification approval of the 747-8.

In addition, the certification basis includes other regulations, special conditions, and exemptions that are not relevant to these special conditions. Type Certificate No. A20WE will be updated to include a complete description of the certification basis for these airplanes.

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 747-8 because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

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 or series that incorporates the same or similar novel or unusual design feature, or should any other model or series already included on the same type certificate be modified to incorporate the same or similar novel or unusual design feature, the special conditions would also apply to the other model or series under § 21.101.

In addition to the applicable airworthiness regulations and special conditions, the 747-8 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.

Special conditions, as defined in § 11.19, are issued under § 11.38, and become part of the type certification basis under § 21.101.

Novel or Unusual Design Features

The Boeing Model 747-8 will incorporate the following novel or unusual design features: The 747-8 design offers seating capacity on two separate decks, the main deck with a maximum passenger capacity of 495 and the upper deck with a maximum passenger capacity of 110. Section 25.810(a)(1)(iii) requires that after full deployment the emergency escape system assist means must be long enough so that the lower end is self-supporting on the ground and provides safe evacuation of occupants to the ground after collapse of one or more legs of the landing gear. Typically, airplanes have fixed-length slides that meet the above requirements. However, it was not possible to use fixed-length slides for the 747-8 Door 1 because of the difference between normal sill height and the high-sill height associated with collapse of some of the landing gear in an emergency. Some combinations of landing gear collapse could cause the airplane to tip back on its tail. The 747-8 Door 1 escape slide is an extendable length design to meet the gear collapse and tail tip conditions.

Discussion

The regulations governing the certification of the 747-8 do not adequately address the certification requirements for an extendable length escape slide. The only reference to extendable length escape slides in Technical Standard Order (TSO) C69c, Emergency Evacuation Slides, Ramps, Ramp/Slides, and Slide/Rafts, is in the inflation time requirement section. The requirements of § 25.801(a)(1)(iii) for other airplanes have been addressed by a single length escape slide. However, for the 747-8 Door 1, it was not possible to have a single length escape slide because of the extreme difference in sill heights between normal sill height and high-sill height associated with collapse of some of the landing gear, and the additional case of the airplane tipping back on its tail. For Door 1, the normal sill height is approximately 187 inches, and the high-sill height is approximately 346 inches.

The design of the extendable length escape system has an approximately 12 foot long extension packed at the toe end of the escape slide. During normal operation, the extension portion remains packed at the toe end. The airplane is equipped with an electronic sensor that evaluates the attitude of the airplane, and determines if the extendable portion is needed. When the extended length is needed, the system sends a signal to an electronic sign on the door to indicate to the flight attendant that the extendable length of the slide needs to be inflated. The extendable length inflation system is activated by pulling on a separate inflation handle located on the right side of the slide girt.

The Airbus A380 airplane has an extendable length slide and the FAA issued Special Conditions Number 25-323-SC to address the installation of the extendable length escape slide in that airplane. These previously issued special conditions provide a starting point for developing special conditions for the 747-8 airplane, which consider and evaluate the unique aspects of this airplane's design.

The extension is intended only for use at high-sill heights. A typical fixed-length slide operating at high-sill height does not satisfy all of the performance requirements of § 25.810, but its variations in performance are understood and largely predictable. Certain performance criteria are valid regardless of sill height, while other aspects of performance can be expected to decline at higher sill heights. With an extendable slide, there is a step change in configuration and potentially a change in performance. Therefore, special conditions are needed to ensure acceptable performance in the extended mode.

Section 25.810 specifies the basic performance requirements for escape slides, including wind testing, repeatability testing, and testing at adverse sill heights. Section 25.1309(a) requires systems to perform under foreseeable operating conditions, such as extreme temperatures, and demonstrate that the system design is appropriate for its intended function. Standards for the equipment itself are in TSO-C69c and contribute to a satisfactory installation.

Typically, wind tests are only conducted on fixed-length slides at normal sill height. Since the regulations require that the escape slides have the capability of being deployed in 25-knot winds directed from the most critical angle, escape slides usually exceed 25-knot performance at other than the critical angle. The same is expected to be true of the slide in its extended mode, but some reduction in the required wind velocity is appropriate since the slide will be in an abnormal condition. Available data indicate that the capability of being deployed in 22-knot winds is appropriate to cover the slide in its extended mode at normal sill height. This corresponds to roughly 75% of the wind energy required for the slide in its normal attitude and will ensure that the slide can function in its extended mode at least as well as a fixed-length slide under similar abnormal conditions.

These special conditions also specify a rate for passenger evacuation that is consistent with that of fixed-length escape slides.

Discussion of Comments

Notice of proposed special conditions No. 25-11-12-SC for Boeing Model 747-8 airplanes was published in the Federal Register on May 10, 2011 (76 FR 26957). No comments were received and the special conditions are adopted as proposed.

Applicability

As discussed above, these special conditions are applicable to Boeing Model 747-8 airplanes. 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 special conditions would apply to that model as well.

Conclusion

This action affects only certain novel or unusual design features of Boeing Model 747-8 airplanes. It is not a rule of general applicability.

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 Boeing Model 747-8 airplanes.

1. The extendable escape slide must receive Technical Standard Order (TSO) C69c or latest TSO authorization published at the time of TSO application for the Door 1 Slide.

2. In addition to the requirements of § 25.810(a)(1)(iii) for usability in conditions of landing gear collapse, the deployed escape slide in the extended mode must demonstrate an evacuation rate of 45 persons per minute per lane at the sill height corresponding to activation of the extension.

3. In lieu of the requirements of § 25.810(a)(1)(iv), the escape slide with the extendable section activated must be capable of being deployed in 22-knot winds directed from the critical angle, with the airplane on all its landing gear, with the assistance of one person on the ground. Two deployment scenarios must be addressed as follows:

(a) Extendable section is activated during the inflation time of the basic slide and,

(b) Extendable section is activated after the basic slide is completely inflated.

4. Pitch sensor tolerances and accuracy must be taken into account when demonstrating compliance with § 25.1309(a) for the escape slide in both extended and unextended modes.

5.(a) There must be a “slide extension” warning such that the cabin crew is immediately made aware of the need to deploy the extendable section of the slide. The ability to provide such a warning must be available for ten minutes after the airplane is immobilized on the ground.

(b) There must be a positive means for the cabin crew to determine that the extendable portion of the slide has been fully erected.

6. Whenever passengers are carried on the main deck of the airplane, there must be a cabin crewmember stationed on each side of the airplane located near each Door 1 Exit. This special condition must be included in the airplane flight manual as a limitation.