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Federal Register / Vol. 86, No. 189 / Monday, October 4, 2021 / Rules and Regulations Steve.Slotte@faa.gov. Comments the FAA receives, which are not specifically designated as CBI, will be placed in the public docket for these special conditions.
Docket: Background documents or comments received may be read at https www.regulations.gov/ at any time. Follow the online instructions for accessing the docket or go to Docket Operations in Room W12140 of the West Building Ground Floor at 1200
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT:
Stephen Slotte, Aircraft Systems, AIR
623, Technical Innovation Policy Branch, Policy and Innovation Division, Aircraft Certification Service, Federal Aviation Administration, 2200 South 216th Street, Des Moines, Washington 98198; telephone and fax 206 231
3163; Steve.Slotte@faa.gov.
SUPPLEMENTARY INFORMATION: The substance of these special conditions has been published in the Federal Register for public comment in several prior instances with no substantive comments received. Therefore, the FAA
has determined that prior public notice and comment are unnecessary, and finds that, for the same reason, good cause exists for adopting these special conditions upon publication in the Federal Register.
Comments Invited The FAA invites 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.
The FAA will consider all comments received by the closing date for comments. The FAA may change these special conditions based on the comments received.
Background On September 30, 2018, Boeing applied for an amendment to Type Certificate No. T00001SE to include the new Model 7779 series airplane. The Boeing Model 7779 airplane, which is a derivative of the Boeing Model 777
airplane currently approved under Type Certificate No. T00001SE, is a twinengine, transport-category airplane with seating for 495 passengers, and a maximum takeoff weight of 775,000 lbs.
Type Certification Basis Under the provisions of title 14, Code of Federal Regulations 14 CFR, 21.101, Boeing must show that the
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Model 7779 series airplane meets the applicable provisions of the regulations listed in Type Certificate No. T00001SE, or the applicable regulations in effect on the date of application for the change, except for earlier amendments as agreed upon by the FAA.
If the Administrator finds that the applicable airworthiness regulations e.g., 14 CFR part 25 do not contain adequate or appropriate safety standards for the Boeing Model 7779 series airplane 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 that incorporates the same novel or unusual design feature, or should any other model already included on the same type certificate be modified to incorporate the same novel or unusual design feature, these special conditions would also apply to the other model under 21.101.
In addition to the applicable airworthiness regulations and special conditions, the Boeing Model 7779
series airplane 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 14 CFR 11.19, in accordance with 11.38, and they become part of the type certification basis under 21.101.
Novel or Unusual Design Features The Boeing Model 7779 series airplane will incorporate the following novel or unusual design feature:
Electrical and electronic systems that perform critical functions, the loss of which may result in loss of flight controls and other critical systems and may be catastrophic to the airplane.
Discussion The Boeing Model 7779 series airplane has a fly-by-wire flight control system that requires a continuous source of electrical power in order to maintain an operable flight control system. Section 25.1351d, Operation without normal electrical power, requires safe operation in visual flight rule VFR conditions for at least five minutes after loss of normal electrical power excluding the battery. This rule is structured around a traditional design using mechanical control cables and linkages for flight control. These manual controls allow the crew to maintain
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aerodynamic control of the airplane for an indefinite period of time after loss of all electrical power. Under these conditions, a mechanical flight control system provides the crew with the ability to fly the airplane while attempting to identify the cause of the electrical failure, restart engines if necessary, and attempt to re-establish some of the electrical power generation capability.
A critical assumption in 25.1351d is that the airplane is in VFR conditions at the time of the failure. This is not a valid assumption in todays airline operating environment where airplanes fly much of the time in instrument meteorological conditions IMC on air traffic control defined flight paths.
Another assumption in the existing rule is that the loss of all normal electrical power is the result of the loss of all engines. The five-minute period in the rule is to allow at least one engine to be restarted following an all-engine power loss in order to continue the flight to a safe landing. However, service experience on airplane models with similar electrical power system architecture as the Boeing Model 777
9 airplane has shown that at least the temporary loss of all electrical power for causes other than all-engine failure is not extremely improbable.
To maintain the same level of safety envisioned by the existing rule with traditional mechanical flight controls, the Boeing Model 7779 series airplane design must not be time-limited in its operation under all reasonably foreseeable conditions, including loss of all normal sources of engine or auxiliary power unit APU-generated electrical power. Unless Boeing can show that the non-restorable loss of the engine and APU power sources is extremely improbable, Boeing must demonstrate that the airplanes can maintain safe flight and landing including steering and braking on the ground for airplanes using steer/brake-by-wire and/or fly-bywire speed brake panels with the use of its emergency/alternate electrical power systems. These electrical power systems, or the minimum restorable electrical power sources, must be able to power loads that are essential for continued safe flight and landing, including those required for the maximum length of approved flight diversion.
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.

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