[Federal Register Volume 79, Number 106 (Tuesday, June 3, 2014)]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-12691]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2014-0329; Notice No. 25-14-03-SC]
Special Conditions: Bombardier Aerospace, Models BD-500-1A10 and
BD-500-1A11 Series Airplanes; Tire Debris Impacts to Fuel Tanks
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
SUMMARY: This action proposes special conditions for the Bombardier
Aerospace Models BD-500-1A10 and BD-500-1A11 series airplanes. These
airplanes will have a novel or unusual design feature associated with
the use of carbon fiber reinforced plastic (CFRP) for most of the wing
fuel tank structure, which, when impacted by tire debris, may resist
penetration or rupture differently from aluminum wing skins. The
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for this design feature. 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.
DATES: Send your comments on or before July 18, 2014.
ADDRESSES: Send comments identified by docket number FAA-2014-0329
using any of the following methods:
Federal eRegulations Portal: Go to http://www.regulations.gov/and follow the online instructions for sending your
Mail: Send comments to Docket Operations, M-30, U.S.
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
Hand Delivery or Courier: Take comments to Docket
Operations in Room W12-140 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.
Fax: Fax comments to Docket Operations at 202-493-2251.
Privacy: The FAA will post all comments it receives, without
change, to http://www.regulations.gov/, including any personal
information the commenter provides. Using the search function of the
docket Web site, anyone can find and read the electronic form of all
comments received into any FAA docket, including the name of the
individual sending the comment (or signing the comment for an
association, business, labor union, etc.). DOT's complete Privacy Act
Statement can be found in the Federal Register published on April 11,
2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov/ gov/.
Docket: Background documents or comments received may be read at
http://www.regulations.gov/at any time. Follow the online instructions
for accessing the docket or go to the Docket Operations in Room W12-140
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
FOR FURTHER INFORMATION CONTACT: Margaret Langsted, FAA, Propulsion
and Mechanical Systems Branch, ANM-112, Transport Airplane Directorate,
Aircraft Certification Service, 1601 Lind Avenue SW., Renton,
Washington, 98057-3356; telephone 425-227-2677; facsimile 425-227-1149.
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 will consider all comments we receive on or before the closing
date for comments. We may change these special conditions based on the
comments we receive.
On December 10, 2009, Bombardier Aerospace applied for a type
certificate for their new Models BD-500-1A10 and BD-500-1A11 series
airplanes (hereafter collectively referred to as ``CSeries''). The
CSeries airplanes are swept-wing monoplanes with an aluminum alloy
fuselage sized for 5-abreast seating. Passenger capacity is designated
as 110 for the Model BD-500-1A10 and 125 for the Model BD-500-1A11.
Maximum takeoff weight is 131,000 pounds for the Model BD-500-1A10 and
144,000 pounds for the Model BD-500-1A11.
Type Certification Basis
Under the provisions of Title 14, Code of Federal Regulations (14
CFR) 21.17, Bombardier Aerospace must show that the CSeries airplanes
meet the applicable provisions of part 25, as amended by Amendments 25-
1 through 25-129 thereto.
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 CSeries airplanes because of a
novel or unusual design feature, special conditions are prescribed
under the provisions of Sec. 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 or similar
novel or unusual design feature, the special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the CSeries airplanes 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, and the FAA must issue a
finding of regulatory adequacy under Sec. 611 of Public Law 92-574,
the ``Noise Control Act of 1972.''
The FAA issues special conditions, as defined in 14 CFR 11.19, in
accordance with Sec. 11.38, and they become part of the type-
certification basis under Sec. 21.17(a)(2).
Novel or Unusual Design Features
The CSeries airplanes will incorporate the following novel or
unusual design features: The use of carbon fiber reinforced plastic
(CFRP) for most of the wing fuel tank structure. The ability of
aluminum wing skins to resist penetration or rupture when impacted by
tire debris is understood from extensive experience, but the ability of
CFRP construction to resist these hazards has not been established.
There are no existing regulations that adequately establish a level of
safety with respect to the performance of the composite materials used
in the construction of wing fuel tanks. It requires the consideration
of fuel tank penetration, fuel leaks, discrete source damage tolerance,
and the effects of shock waves generated by tire debris impact.
Accidents have resulted from uncontrolled fires caused by fuel
leaks following penetration or rupture of the lower wing by fragments
of tires or from uncontained engine failure. The Concorde accident in
2000 is the most notable example. That accident demonstrated an
unanticipated failure mode in an airplane with an unusual transport
airplane configuration. Impact to the lower wing surface by tire debris
induced pressure waves within the fuel tank that resulted in fuel
leakage and fire. Regulatory authorities subsequently required
modifications to the Concorde to improve impact resistance of the lower
wing or means to retain fuel if the primary fuel retention means is
In another incident, a Boeing Model 747 tire burst during an
aborted takeoff from Honolulu, Hawaii. That tire debris penetrated a
fuel tank access cover, causing substantial fuel leakage. Passengers
were evacuated down the emergency chutes into pools of fuel that
fortunately had not ignited.
These accidents highlight deficiencies in the existing regulations
pertaining to fuel retention following impact of the fuel tanks by tire
fragments. Following a 1985 Boeing Model 737 accident in Manchester,
England, in which a fuel tank access panel was penetrated by engine
debris, the FAA amended 14 CFR 25.963 to require fuel tank access
panels that are resistant to both tire and engine debris (engine debris
is addressed elsewhere). This regulation, Sec. 25.963(e), only
addressed the fuel tank access covers since service experience at the
time showed that the lower wing skin of a conventional, subsonic
airplane provided adequate inherent capability to resist tire and
engine debris threats. More specifically, that regulation requires
showing by analysis or tests that the access covers ``. . . minimize
penetration and deformation by tire fragments, low energy engine
debris, or other likely debris.'' Advisory Circular (AC) 25.963-1, Fuel
Tank Access Covers, describes the region of the wing that is vulnerable
to impact damage from these sources and provides a method to
substantiate that the rule has been met for tire fragments. No specific
requirements were established for the contiguous wing areas into which
the access covers are installed, because of the inherent ability of
conventional aluminum wing skins to resist penetration by tire debris.
AC 25.963-1 specifically notes, ``The access
covers, however, need not be more impact resistant than the contiguous
tank structure,'' highlighting the assumption that the wing structure
is more capable of resisting tire impact debris than fuel tank access
In order to maintain the level of safety envisioned by 14 CFR
25.963(e), these special conditions propose a standard for resistance
to potential tire debris impacts to the contiguous wing surfaces and
require consideration of possible secondary effects of a tire impact,
such as the induced pressure wave that was a factor in the Concorde
accident. It takes into account that new construction methods and
materials will not necessarily yield debris resistance that has
historically been shown as adequate. The proposed standard is based on
the defined tire impact areas and tire fragment characteristics.
In addition, despite practical design considerations, some uncommon
debris larger than that defined in paragraph 2 may cause a fuel leak
within the defined area, so paragraph 3 of these proposed special
conditions also takes into consideration possible leakage paths. Fuel
tank surfaces of typical transport airplanes have thick aluminum
construction in the tire debris impact areas that is tolerant to tire
debris larger than that defined in paragraph 2 of these special
conditions. Consideration of leaks caused by larger tire fragments is
needed to ensure that an adequate level of safety is provided.
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
As discussed above, these special conditions are applicable to the
BD-500-1A10 and BD-500-1A11 (CSeries) airplanes. Should Bombardier
Aerospace apply at a later date for a change to the type certificate to
include another model incorporating the same novel or unusual design
feature, the special conditions would apply to that model as well.
This action affects only certain novel or unusual design features
on one model series of airplanes. It is not a rule of general
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
The Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for Bombardier Aerospace BD-500-1A10 and BD-500-1A11 (CSeries)
Tire Debris Impacts to Fuel Tanks
1. Impacts by tire debris to any fuel tank or fuel system component
located within 30 degrees to either side of wheel rotational planes may
not result in penetration or otherwise induce fuel tank deformation,
rupture (for example, through propagation of pressure waves), or
cracking sufficient to allow a hazardous fuel leak. A hazardous fuel
leak results if debris impact to a fuel tank surface causes a--
a. Running leak,
b. Dripping leak, or
c. Leak that, 15 minutes after wiping dry, results in a wetted
airplane surface exceeding 6 inches in length or diameter.
The leak must be evaluated under maximum fuel head pressure.
2. Compliance with paragraph 1 must be shown by analysis or tests
assuming all of the following:
a. The tire debris fragment size is 1 percent of the tire mass.
b. The tire debris fragment is propelled at a tangential speed that
could be attained by a tire tread at the airplane flight manual
airplane rotational speed (VR at maximum gross weight).
c. The tire debris fragment load is distributed over an area on the
fuel tank surface equal to 1\1/2\ percent of the total tire tread area.
3. Fuel leaks caused by impact from tire debris larger than that
specified in paragraph 2, from any portion of a fuel tank or fuel
system component located within the tire debris impact area defined in
paragraph 1, may not result in hazardous quantities of fuel entering
any of the following areas of the airplane:
a. Engine inlet,
b. Auxiliary power unit inlet, or
c. Cabin air inlet.
This must be shown by test or analysis, or a combination of both,
for each approved engine forward thrust condition and each approved
reverse thrust condition.
Issued in Renton, Washington, on May 15, 2014.
Acting Manager, Transport Airplane Directorate, Aircraft Certification
[FR Doc. 2014-12691 Filed 6-2-14; 8:45 am]
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