[Federal Register: April 12, 2007 (Volume 72, Number 70)]
[Rules and Regulations]
[Page 18372-18375]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr12ap07-5]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM371; Special Conditions No. 25-350-SC]
Special Conditions: Dassault Aviation Model Falcon 7X Airplane;
Sudden Engine Stoppage, Operation Without Normal Electrical Power, and
Dive Speed Definition With Speed Protection System
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Dassault Aviation
Model Falcon 7X Airplane; Sudden Engine Stoppage, Operation Without
Normal Electrical Power, and Dive Speed Definition with Speed
Protection System. This airplane will have novel or unusual design
features that include engine size and torque load, which affect sudden
engine stoppage; electrical and electronic systems which perform
critical functions, which affect operation without normal electrical
power; and dive speed definition with speed protection system. These
special conditions pertain to their effects on the structural
performance of the airplane. The applicable airworthiness regulations
do not contain adequate or appropriate safety standards for these
design features. 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.
EFFECTIVE DATE: April 4, 2007.
FOR FURTHER INFORMATION CONTACT: Tom Rodriguez, FAA, International
Branch, ANM-116, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue, SW., Renton, Washington 98057-3356;
telephone (425) 227-1503; facsimile (425) 227-1320.
SUPPLEMENTARY INFORMATION:
Background
On June 4, 2002, Dassault Aviation, 9 rond Point des Champs
Elysees, 75008, Paris, France, applied for an FAA type certificate for
its new Model Falcon 7X airplane. The Dassault Model Falcon 7X airplane
is a 19 passenger transport category airplane powered by three aft
mounted Pratt & Whitney PW307A high bypass ratio turbofan engines.
Maximum takeoff weight will be 63,700 pounds, and maximum certified
altitude
[[Page 18373]]
will be 51,000 feet with a range of 5,700 nautical miles. The airplane
is operated using a fly-by-wire (FBW) primary flight control system.
This will be the first application of a FBW primary flight control
system in an airplane primarily intended for private/corporate use.
The Dassault Aviation Model Falcon 7X design incorporates equipment
that was not envisioned when part 25 was created. This equipment
affects sudden engine stoppage, operation without normal electrical
power, and dive speed definition with speed protection system.
Therefore, special conditions are required that provide the level of
safety equivalent to that established by the regulations.
Type Certification Basis
Under the provisions of 14 CFR 21.17, Dassault Aviation must show
that the Model Falcon 7X airplane meets the applicable provisions of 14
CFR part 25, as amended by Amendments 25-1 through 25-108.
If the Administrator finds that the applicable airworthiness
regulations do not contain adequate or appropriate safety standards for
the Model Falcon 7X airplane because of novel or unusual design
features, special conditions are prescribed under the provisions of
Sec. 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the Dassault Model Falcon 7X 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 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 under Sec. 21.101.
Novel or Unusual Design Features
The Dassault Aviation Model Falcon 7X airplane will incorporate
novel or unusual design features that will affect:
Sudden engine stoppage.
Operation without normal electrical power.
Dive speed definition with speed protection system.
These special conditions address equipment which may affect the
airplane's structural performance, either directly or as a result of
failure or malfunction. These special conditions are identical or
nearly identical to those previously required for type certification of
other airplane models.
Discussion
Because of these rapid improvements in airplane technology, the
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for these design features. Therefore, in
addition to the requirements of part 25, subparts C and D, the
following special conditions apply.
Special Conditions for Sudden Engine Stoppage
The Dassault Model Falcon 7X will have high-bypass ratio turbofan
engines. Engines of this size were not envisioned when Sec. 25.361,
pertaining to loads imposed by engine seizure, was adopted in 1965.
Worst case engine seizure events become increasingly more severe with
increasing engine size because of the higher inertia of the rotating
components.
Section 25.361(b)(1) requires that for turbine engine
installations, the engine mounts and the supporting structures must be
designed to withstand a ``limit engine torque load imposed by sudden
engine stoppage due to malfunction or structural failure.'' Limit loads
are expected to occur about once in the lifetime of any airplane.
Section 25.305 requires that supporting structures be able to support
limit loads without detrimental permanent deformation, meaning that
supporting structures should remain serviceable after a limit load
event.
Since adoption of Sec. 25.361(b)(1), the size, configuration, and
failure modes of jet engines have changed considerably. Current engines
are much larger and are designed with large bypass fans. In the event
of a structural failure, these engines are capable of producing much
higher transient loads on the engine mounts and supporting structures.
As a result, modern high bypass engines are subject to certain
rare-but-severe engine seizure events. Service history shows that such
events occur far less frequently than limit load events. Although it is
important for the airplane to be able to support such rare loads safely
without failure, it is unrealistic to expect that no permanent
deformation will occur.
Given this situation, the Aviation Rulemaking Advisory Committee
(ARAC) proposed a design standard for today's large engines. For the
commonly-occurring deceleration events, the proposed standard requires
engine mounts and structures to support maximum torques without
detrimental permanent deformation. For the rare-but-severe engine
seizure events such as loss of any fan, compressor, or turbine blade,
the proposed standard requires engine mounts and structures to support
maximum torques without failure, but allows for some deformation in the
structure.
The FAA concludes that modern large engines, including those on the
Model Falcon 7X, are novel and unusual compared to those envisioned
when Sec. 25.361(b)(1) was adopted and thus warrant a special
condition. The special condition contains design criteria recommended
by ARAC. The ARAC proposal was to revise the wording of Sec.
25.361(b), including Sec. Sec. 25.361(b)(1) and (b)(2), removing
language pertaining to structural failures and moving it to a separate
requirement that discusses the reduced factors of safety that apply to
these failures.
Special Conditions for Operation Without Normal Electrical Power
The Dassault Aviation Model Falcon 7X airplane will have electrical
and electronic systems which perform critical functions. The Model
Falcon 7X airplane is a fly-by-wire control system that requires a
continuous source of electrical power for the flight control system to
remain operable, since the loss of all electrical power may be
catastrophic to the airplane. The airworthiness standards of part 25 do
not contain adequate or appropriate standards for the protection of the
Electronic Flight Control System from the adverse effects of operations
without normal electrical power.
Section 25.1351(d), ``Operation without normal electrical power,''
requires safe operation in visual flight rule (VFR) conditions for at
least five minutes with inoperative normal power. This rule was
structured around a traditional design utilizing mechanical control
cables for flight control surfaces and the pilot controls. Such
traditional designs enable the flightcrew to maintain control of the
airplane, while providing time to sort out the electrical failure, re-
start the engines if necessary, and re-establish some of the electrical
power generation capability.
The Dassault Aviation Model Falcon 7X airplane, however, will
utilize an Electronic Flight Control System for the pitch and yaw
control (elevator, stabilizer, and rudder). There is no mechanical
linkage between the pilot controls and these flight control surfaces.
Pilot control inputs are converted to electrical signals, which are
processed and then transmitted via wires to the control surface
actuators. At the control surface actuators, the
[[Page 18374]]
electrical signals are converted to an actuator command, which moves
the control surface.
To maintain the same level of safety as that associated with
traditional designs, the Dassault Model 7X airplanes with electronic
flight controls must not be time limited in their operation, including
being without the normal source of electrical power generated by the
engine or the Auxiliary Power Unit (APU) generated electrical power.
Service experience has shown that the loss of all electrical power
generated by the airplane's engine generators or APU is not extremely
improbable. Thus, it must be demonstrated that the airplane can
continue safe flight and landing--including steering and braking on
ground for airplanes using steer/brake-by-wire--after total loss of
normal electrical power with the use of its emergency electrical power
systems. These emergency electrical power systems must be able to power
loads that are essential for continued safe flight and landing.
Special Conditions for Dive Speed Definition With Speed Protection
System
Dassault Aviation proposed to reduce the speed margin between
VC and VD required by Sec. 25.335(b), based on
the incorporation of a high speed protection system in the Model Falcon
7X flight control laws. The Falcon 7X is equipped with a high speed
protection system which limits nose down pilot authority at speeds
above VC/MC and prevents the airplane from
actually performing the maneuver required under Sec. 25.335(b)(1).
Section 25.335(b)(1) is an analytical envelope condition which was
originally adopted in Part 4b of the Civil Air Regulations to provide
an acceptable speed margin between design cruise speed and design dive
speed. Freedom from flutter and airframe design loads is affected by
the design dive speed. While the initial condition for the upset
specified in the rule is 1g level flight, protection is afforded for
other inadvertent overspeed conditions as well. Section 25.335(b)(1) is
intended as a conservative enveloping condition for all potential
overspeed conditions, including non-symmetric ones.
To establish that all potential overspeed conditions are enveloped,
the applicant will demonstrate that the dive speed will not be exceeded
during pilot-induced or gust-induced upsets in non-symmetric attitudes.
In addition, the high speed protection system in the Falcon 7X must
have a high level of reliability.
Discussion of Comments
Notice of proposed special conditions No. 25-07-07-SC for the
Dassault Aviation Model Falcon 7X airplanes was published in the
Federal Register on March 1, 2007 (72 FR 9273). No comments were
received, and the special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to the
Dassault Aviation Model Falcon 7X airplane. Should Dassault Aviation
apply at a later date for a change to the type certificate to include
another model on the same type certificate incorporating the same novel
or unusual design features, these special conditions would apply to
that model as well.
For Final Special Conditions Effective Upon Issuance
Under standard practice, the effective date of final special
conditions would be 30 days after the date of publication in the
Federal Register; however, as the certification date for the Dassault
Model Falcon 7X is imminent, the FAA finds that good cause exists to
make these special conditions effective upon issuance.
Conclusion
This action affects only certain novel or unusual design features
on model Falcon 7X 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 Dassault Aviation Model Falcon 7X
airplanes.
1. Sudden Engine Stoppage
In lieu of the requirements of Sec. 25.361(b) the following
special condition applies:
(a) For turbine engine installations, the engine mounts, pylons and
adjacent supporting airframe structure must be designed to withstand 1
g level flight loads acting simultaneously with the maximum limit
torque loads imposed by each of the following:
(1) Sudden engine deceleration due to a malfunction which could
result in a temporary loss of power or thrust; and
(2) The maximum acceleration of the engine.
(b) For auxiliary power unit installations, the power unit mounts
and adjacent supporting airframe structure must be designed to
withstand 1 g level flight loads acting simultaneously with the maximum
limit torque loads imposed by each of the following:
(1) Sudden auxiliary power unit deceleration due to malfunction or
structural failure; and
(2) The maximum acceleration of the power unit.
(c) For engine supporting structures, an ultimate loading condition
must be considered that combines 1 g flight loads with the transient
dynamic loads resulting from:
(1) The loss of any fan, compressor, or turbine blade; and
separately
(2) where applicable to a specific engine design, any other engine
structural failure that results in higher loads.
(d) The ultimate loads developed from the conditions specified in
paragraphs (c)(1) and (2) above are to be multiplied by a factor of 1.0
when applied to engine mounts and pylons and multiplied by a factor of
1.25 when applied to adjacent supporting airframe structure. In
addition, the airplane must be capable of continued safe flight
considering the aerodynamic effects on controllability due to any
permanent deformation that results from the conditions specified in
paragraph (c), above.
2. Operation Without Normal Electrical Power
In lieu of the requirements of 14 CFR 25.1351(d), the following
special condition applies:
It must be demonstrated by test or combination of test and analysis
that the airplane can continue safe flight and landing with inoperative
normal engine and APU generator electrical power (i.e., electrical
power sources, excluding the battery and any other standby electrical
sources). The airplane operation should be considered at the critical
phase of flight and include the ability to restart the engines and
maintain flight for the maximum diversion time capability being
certified.
3. Dive Speed Definition With Speed Protection System
In lieu of the requirements of Sec. 25.335(b)(1)--if the flight
control system includes functions which act automatically to initiate
recovery before
[[Page 18375]]
the end of the 20 second period specified in Sec. 25.335(b)(1)--the
following special condition applies.
The greater of the speeds resulting from the conditions of
paragraphs (a) and (b), below, must be used.
(a) From an initial condition of stabilized flight at
VC/MC, the airplane is upset so as to take up a
new flight path 7.5 degrees below the initial path. Control
application, up to full authority, is made to try and maintain this new
flight path. Twenty seconds after initiating the upset, manual recovery
is made at a load factor of 1.5 g (0.5 acceleration increment) or such
greater load factor that is automatically applied by the system with
the pilot's pitch control neutral. The speed increase occurring in this
maneuver may be calculated, if reliable or conservative aerodynamic
data is used. Power, as specified in Sec. 25.175(b)(1)(iv), is assumed
until recovery is made, at which time power reduction and the use of
pilot controlled drag devices may be used.
(b) From a speed below VC/MC with power to
maintain stabilized level flight at this speed, the airplane is upset
so as to accelerate through VC/MC at a flight
path 15 degrees below the initial path--or at the steepest nose down
attitude that the system will permit with full control authority if
less than 15 degrees.
Note: The pilot's controls may be in the neutral position after
reaching VC/MC and before recovery is
initiated.
(c) Recovery may be initiated three seconds after operation of high
speed warning system by application of a load of 1.5 g (0.5
acceleration increment) or such greater load factor that is
automatically applied by the system with the pilot's pitch control
neutral. Power may be reduced simultaneously. All other means of
decelerating the airplane, the use of which is authorized up to the
highest speed reached in the maneuver, may be used. The interval
between successive pilot actions must not be less than one second.
(d) The applicant must also demonstrate that the design dive speed,
established above, will not be exceeded during pilot-induced or gust-
induced upsets in non-symmetric attitudes.
(e) The occurrence of any failure condition that would reduce the
capability of the overspeed protection system must be improbable (less
than 10-5 per flight hour).
Issued in Renton, Washington, on April 4, 2007.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E7-6889 Filed 4-11-07; 8:45 am]
BILLING CODE 4910-13-P