[Federal Register Volume 75, Number 75 (Tuesday, April 20, 2010)]
[Rules and Regulations]
[Pages 20516-20518]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-9026]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. CE305; Special Conditions No. 23-245-SC]
Special Conditions: Cirrus Design Corporation, Model SF50; Fire
Extinguishing for Upper Aft Fuselage Mounted Engine
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions; request for comments.
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SUMMARY: These special conditions are issued for the Cirrus Design
Corporation, model SF50 airplane. This single turbofan engine airplane
will have a novel or unusual design feature(s) associated with mounting
the engine in the aft fuselage. 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 April 12,
2010.
We must receive your comments by May 20, 2010.
ADDRESSES: Mail two copies of your comments to: Federal Aviation
Administration, Regional Counsel, ACE-7, Attn: Rules Docket No. CE305,
901 Locust, Kansas City, MO 64106. You may deliver two copies to the
Regional Counsel at the above address. Mark your comments: Docket No.
CE305. You may inspect comments in the Rules Docket weekdays, except
Federal holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Leslie B. Taylor, Federal Aviation
Administration, Small Airplane Directorate, Aircraft Certification
Service, 901 Locust, Room 301, Kansas City, MO 64106; telephone (816)
329-4134; facsimile (816) 329-4090, email [email protected].
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 persons to submit such written data, views, or
arguments as they desire. 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 may 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 9, 2008, Cirrus Design Corporation applied for a type
certificate for their new model SF50. The model SF50 is a 7 seat (5
adults and 2 children), pressurized, retractable gear, carbon
composite, airplane with one turbofan engine mounted partially in the
upper aft fuselage.
The single turbofan engine is mounted on the upper aft fuselage,
not in the pilot's line of site. Upper aft fuselage mounted engine
installations, along with the need to protect such installed engines
from fires, were not envisioned in the development of the part 23
normal category regulations.
[[Page 20517]]
Type Certification Basis
Under the provisions of 14 CFR 21.17, Cirrus Design Corporation
must show that the model SF50 meets the applicable provisions of part
23, as amended by Amendment 23-1 through Amendment 23-59 thereto.
If the Administrator finds that the applicable airworthiness
regulations, part 23, do not contain adequate or appropriate safety
standards for the model SF50 because of a novel or unusual design
feature, special conditions are prescribed under the provisions of
Sec. 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the model SF50 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 section 611 of Public Law 92-574, the ``Noise
Control Act of 1972.''
The FAA issues special conditions, as defined in Sec. 11.19, under
Sec. 11.38 and they become part of the type certification basis under
Sec. 21.17(a)(2).
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, the special conditions would also apply to the
other model.
Novel or Unusual Design Features
The model SF50 will incorporate the following novel or unusual
design features: An aft fuselage mounted engine is not in the pilot's
line of sight. This type of configuration was not envisioned in the
development of part 23 normal category airplanes. Therefore, a special
condition for the fire extinguishing system for the engine on the model
SF50 is required.
Regulations requiring and defining engine compartment fire
extinguishing systems already exist for part 23 commuter category
airplanes. These regulations will provide an adequate level of safety
for the normal category model SF50 with the aft mounted engine except
SC 23.1195 will require a two shot system.
As the extinguishing agent is subject to change during the service
life of the airplane, the certification basis must include 14 CFR
23.1197, 23.1199, 23.1201 in their entirety.
Discussion
Part 23 has historically addressed fire protection through
prevention, identification, and containment. Prevention has been
accomplished by minimizing the potential for ignition of flammable
fluids and vapors. Identification has traditionally been achieved by
the location of the engines within the pilot's primary field of view
and/or with the incorporation of fire detection systems. This
philosophy has provided for both the rapid detection of a fire and
confirmation when it has been extinguished. Containment has been
provided through the isolation of designated fire zones through
flammable fluid shutoff valves and firewalls. The containment
philosophy also ensures that components of the engine control system
will function effectively to permit a safe shutdown of the engine.
However, containment has only been required to be demonstrated for 15
minutes. In the event of a fire in a traditional part 23 airplane, the
corrective action is to land as soon as possible. For a small, simple
aircraft originally envisioned by part 23, it is possible to descend
the aircraft to a suitable landing site within 15 minutes. Thus, if the
isolation means do not extinguish the fire, the occupants can safely
exit the aircraft prior to the firewall being breached. These simple
and traditional aircraft normally have the engine located away from
critical flight control systems and primary structure. This has ensured
that throughout the fire event the pilot can maintain control and
continue safe flight. It has also made predicting the effects of a fire
relatively easy. Other design features of these simple and traditional
aircraft, such as low stall speeds and short landing distances, ensure
that even in the event of an off field landing the potential for a
catastrophic outcome has been minimized.
Excluding commuter category, normal category airplanes
incorporating one or more engines on the aft fuselage were not
envisioned in part 23. Engine(s) located on the aft fuselage offer
minimal opportunity to visually detect a fire. The ability to
extinguish an engine fire becomes extremely critical due to this
location. In a traditional pylon engine there is a standoff distance
from the fuselage where there is no possible impingement of fluid or
flame on the fuselage. Thus after 5 minutes if the fluid lines succumb
to the fire any liberated fluid would not come into contact with any
other critical structure or the fuselage. In essence the engine could
burn off of the pylon and not adversely compromise the fuselage. The
Cirrus design configuration does not benefit from this consideration
and thus there is a greater risk due to fire. Also, if there was a fire
due to a buildup of fuel in the exhaust nozzle a low velocity flame
could impinge upon the fuselage or empennage.
Airplanes of the classic configuration with twin aft pylon mounted
engines have fire extinguishing ``one-shot'' systems. A two shot system
is necessary for fuselage embedded engines since the metallic
components in the fire zone can be hot enough to re-ignite flammable
fumes after the first fire has been extinguished. The consequences of a
fire in these locations can be more varied, adverse, and difficult to
predict than the engine fire envisioned for a typical part 23 airplane.
The Cirrus aft engine installation is more indicative of an embedded
engine rather than a pylon mounted engine.
Applicability
As discussed above, these special conditions are applicable to the
model SF50. Should Cirrus Design Corporation 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.
Conclusion
This action affects only certain novel or unusual design features
on one model of airplanes. It is not a rule of general applicability
and affects only the applicant who applied to the FAA for approval of
these features on the airplane.
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. Therefore, 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 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 23
Aircraft, Aviation safety, Signs and symbols.
[[Page 20518]]
Citation
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and
21.17; and 14 CFR 11.38 and 11.19.
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 Cirrus Design Corporation model SF50
airplanes.
Fire Extinguishing for Upper Aft Fuselage Mounted Engine
SC 23.1195 Fire Extinguishing Systems
Fire extinguishing systems must be installed and compliance shown
with the following:
(a) Except for combustor, turbine, and tailpipe sections of
turbine-engine installations that contain lines or components carrying
flammable fluids or gases for which a fire originating in these
sections is shown to be controllable, a fire extinguisher system must
serve each engine compartment.
(b) The fire extinguishing system, the quantity of the
extinguishing agent, the rate of discharge, and the discharge
distribution must be adequate to extinguish fires. An individual ``two
shot'' system must be used.
(c) The fire extinguishing system for a nacelle must be able to
simultaneously protect each compartment of the nacelle for which
protection is provided.
SC 23.1197 Fire Extinguishing Agents
The following applies:
(a) Fire extinguishing agents must--
(1) Be capable of extinguishing flames emanating from any burning
of fluids or other combustible materials in the area protected by the
fire extinguishing system; and
(2) Have thermal stability over the temperature range likely to be
experienced in the compartment in which they are stored.
(b) If any toxic extinguishing agent is used, provisions must be
made to prevent harmful concentrations of fluid or fluid vapors (from
leakage during normal operation of the airplane or as a result of
discharging the fire extinguisher on the ground or in flight) from
entering any personnel compartment, even though a defect may exist in
the extinguishing system. This must be shown by test except for built-
in carbon dioxide fuselage compartment fire extinguishing systems for
which--
(1) Five pounds or less of carbon dioxide will be discharged, under
established fire control procedures, into any fuselage compartment; or
(2) Protective breathing equipment is available for each flight
member on flight deck duty.
SC 23.1199 Extinguishing Agent Containers
The following applies:
(a) Each extinguishing agent container must have a pressure relief
valve to prevent bursting of the container by excessive internal
pressures.
(b) The discharge end of each discharge line from a pressure relief
connection must be located so that discharge of the fire extinguishing
agent would not damage the airplane. The line must also be located or
protected to prevent clogging caused by ice or other foreign matter.
(c) A means must be provided for each fire extinguishing agent
container to indicate that the container has discharged or that the
charging pressure is below the established minimum necessary for proper
functioning.
(d) The temperature of each container must be maintained under
intended operating conditions to prevent the pressure in the container
from --
(1) Falling below that necessary to provide an adequate rate of
discharge; or
(2) Rising high enough to cause premature discharge.
(e) If a pyrotechnic capsule is used to discharge the extinguishing
agent, each container must be installed so that temperature conditions
will not cause hazardous deterioration of the pyrotechnic capsule.
SC 23.1201 Fire Extinguishing System Materials
The following apply:
(a) No material in any fire extinguishing system may react
chemically with any extinguishing agent so as to create a hazard.
(b) Each system component in an engine compartment must be
fireproof.
Issued in Kansas City, Missouri on April 12, 2010.
Steve Thompson,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2010-9026 Filed 4-19-10; 8:45 am]
BILLING CODE 4910-13-P