[Federal Register Volume 60, Number 239 (Wednesday, December 13, 1995)]
[Rules and Regulations]
[Pages 63901-63904]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-30366]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-120; Special Conditions No. 25-ANM-110]
Special Conditions: Jetstream Aircraft Limited Model 4101 Series
Airplanes; Automatic Takeoff Thrust Control System
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special conditions, request for comments.
-----------------------------------------------------------------------
SUMMARY: These special conditions are issued to Jetstream Aircraft
Limited for the Jetstream Model 4101 series airplanes. This airplane
will have an unusual design feature for which the applicable
airworthiness regulations do not contain appropriate safety standards.
The unusual design feature is an Automatic Takeoff Thrust Control
System (ATTCS) that resets power on the operating engine for compliance
with the approach climb performance requirements in Sec. 25.121(d).
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 December 6,
1995. Comments must be received on or before January 29, 1996.
ADDRESSES: Comments on these final special conditions, request for
comments, may be mailed in duplicate to: Federal Aviation
Administration, Office of the Assistant Chief Counsel, Attn: Rules
Docket (ANM-7), Docket No. NM-120, 1601 Lind Avenue SW., Renton,
Washington, 98055-4056; or delivered in duplicate to the Office of the
Assistant Chief Counsel at the above address. Comments must be marked
``Docket No. NM-120.'' Comments may be inspected in the Rules Docket
weekdays, except Federal holidays, between 7:30 and 4:00 p.m.
FOR FURTHER INFORMATION CONTACT: William Schroeder, FAA,
Standardization Branch, ANM-113, Transport Airplane Directorate,
Aircraft Certification Service, 1601 Lind Avenue SW., Renton,
Washington, 98055-4056, telephone (206) 227-2148.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA has determined that good cause exists for making these
special conditions effective upon issuance; however, interested persons
are invited to submit such written data, views, or arguments as they
may desire. Communications should identify the regulatory docket and
special conditions number and be submitted in duplicate to the address
specified above. All communications received on or before the closing
date for comments will be considered by the Administrator. These
special conditions may be changed in light of the comments received.
All comments submitted will be available in the Rules Docket for
examination by interested persons, both before and after the closing
date for comments. A report summarizing each substantive public contact
with FAA personnel concerning this rulemaking will be filed in the
docket. Persons wishing the FAA to acknowledge receipt of their
comments submitted in response to this request must submit with those
comments a self-addressed, stamped postcard on which the following
statement is made: ``Comments to Docket No. NM-120.'' The postcard will
be date stamped and returned to the commenter.
Background
On May 24, 1989, British Aerospace Public Limited Company (BAe)
(currently Jetstream Aircraft Ltd.) applied for a type certificate for
the BAe Model 4100 (currently Jetstream Model 4101) airplane in the
transport airplane category. The Jetstream Model 4101 is a transport
category airplane powered by two Garrett TPE331-14GR/HR Series turbo-
propeller engines mounted on the wing. McCauley Model B/C 5JFR36C1101/2
or 3/4-/L114 G/H CA-0 five-blade propellers are installed. The airplane
is type certificated with two flight crewmembers and up to 30
passengers.
The Jetstream Model 4101 will incorporate an unusual design
feature, the Automatic Takeoff Thrust Control System (ATTCS), referred
to by Jetstream as Automatic Power Reserve or APR, to show compliance
with the approach climb requirements of Sec. 25.121(d). Appendix I to
part 25 limits the application of performance credit for ATTCS to
takeoff only. Since the airworthiness regulations do not contain
appropriate safety standards for approach climb performance using
ATTCS, special conditions are required to ensure a level of safety
equivalent to that established in the regulations.
Type Certification Basis
Under the provisions of Sec. 21.101, Jetstream must show that the
Model 4101 series airplanes, as changed, continues to meet the
applicable provisions of the regulations incorporated by reference in
Type Certificate No. A41NM or the applicable regulations in effect on
the date of application for the change. The regulations incorporated by
reference in the type certificate are commonly referred to as the
``original type certification basis.'' The regulations incorporated by
reference in Type Certificate No. A41NM are as follows:
Based on Secs. 21.29 and 21.17 and the type certification
application date, the applicable U.S. type certification basis for the
Model 4101 was established as follows:
--Part 25 of the FAR dated February 1, 1965, as amended by Amendments
25-1 through 25-66 (all based on BAe application date to CAA), and
--Part 25 of the FAR, Amendments 25-67, 25-68, 25-69, 25-70, 25-71, and
--Part 25 of the FAR, Secs. 25.361 and 25.729 and paragraphs
25.571(e)(2), 25.773(b)(2) and 25.905(d), all as amended by Amendment
25-72, and
--Section 25.1419 as amended by Amendments 25-1 through 25-66, and
--Special Conditions (SC) as follows:
--Special Conditions No. 25-ANM-48 issued August 29, 1991, Lightning
and High Intensity Radiated Fields (HIRF)
--Special Conditions No. 25-ANM-45 issued July 9, 1991, Cabin Aisle
Width, and
--The following exemptions were petitioned for and granted:
--FAA Exemption No. 5587 issued January 13, 1993, Head Impact Criteria
(25.562(c)(5)) for the three most forward passenger seats in passenger
cabin, and
--Equivalent safety findings as follows:
--25.349 of the FAR, Rolling Conditions
[[Page 63902]]
--25.729(e)(2) of the FAR, Landing Gear Aural Warning
--25.811(d)(2) of the FAR, Emergency Exit Marking, Over Wing Exits
--25.1182 of the FAR, Nacelle areas behind firewalls, and
--Part 34 of the FAR effective September 10, 1990, and
--Part 36 of the FAR effective December 1, 1969, including Amendments
36-1 through 36-18, including Appendices A, B, and C.
If the Administrator finds that the applicable airworthiness
regulations (i.e., part 25 as amended) do not contain adequate or
appropriate safety standards for Jetstream Model 4101 series airplanes
because of a novel or unusual design feature, special conditions are
prescribed under the provisions of Sec. 21.16 to establish a level of
safety equivalent to that established in the regulations.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 after public notice, as required by Secs. 11.28 and
11.29(b), and become part of the type certification basis in accordance
with Sec. 21.101(b)(2).
Novel or Unusual Design Features
The Jetsteam 4101 is a twin turbopropeller airplane equipped with
electronic engine controls that protect against exceeding the engine
temperature and torque limits. It also incorporates an ATTCS system
that can automatically add power to the operating engine in the event
one engine fails. This system benefits engine life by allowing the
normal all-engines-operating power to be set at less than the maximum
available power when the airplane operation is limited only by one-
engine-inoperative performance considerations. If an engine fails, the
ATTCS is armed and the operating engine is above 65% torque, the ATTCS
automatically increases the Exhaust Gas Temperature (EGT) limit by
40 deg. C and the torque by 11%, but does not allow the torque to
exceed either the 100% torque limit or the higher EGT limit. Therefore,
the Jetstream 4101 ATTCS only provides an increase in power at
temperatures above the normal flat rate limit temperature.
The part 25 standards for ATTCS, contained in Sec. 25.904 and
Appendix I, specifically restrict performance credit for ATTCS to
takeoff. Expanding the scope of the standards to include other phases
of flight, including go-around, was considered at the time the
standards were issued, but flightcrew workload issues precluded further
consideration. As stated in the preamble to Amendment 25-62:
In regard to ATTCS credit for approach climb and go-around
maneuvers, current regulations preclude a higher thrust for the
approach climb (Sec. 25.121(d)) than for the landing climb
(Sec. 25.119). The workload required for the flightcrew to monitor
and select from multiple in-flight thrust settings in the event of
an engine failure during a critical point in the approach, landing,
or go-around operations is excessive. Therefore, the FAA does not
agree that the scope of the amendment should be changed to include
the use of ATTCS for anything except the takeoff phase. (52 FR
43153, November 9, 1987)
The ATTCS incorporated on the Jetstream 4101 allows the pilot to
use the same power setting procedure during a go-around regardless of
whether or not an engine fails. In either case, the pilot obtains go-
around power by advancing the power levers until reaching either 100%
torque or the EGT limit. If ATTCS is operating (i.e., one engine is
inoperative), the EGT limit computed by the electronic engine control
and displayed to the pilot is 40 deg. C higher than when all engines
are operating. For a go-around in which an engine fails after go-around
power has been set, the ATTCS operates exactly as it does during
takeoff to automatically boost power.
The definition of a critical time interval for the approach climb
case, during which time it must be extremely improbable to violate a
flight path based on the Sec. 25.121(d) gradient requirement is of
primary importance. The Sec. 25.121(d) gradient requirement implies a
minimum one-engine-inoperative flight path capability with the airplane
in the approach configuration. The engine may have been inoperative
before initiating the go-around, or it may become inoperative during
the go-around. The definition of the critical time interval must
consider both possibilities.
As discussed above, these special conditions are applicable to the
Jetstream Model 4101. Should Jetstream Aircraft Limited apply at a
later date for a change to the type certificate to include another
model incorporating the same novel or unusual design feature, these
special conditions would apply to that model as well under the
provisions of Sec. 21.101(a)(1).
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 Jetstream
Model 4101 is imminent, the FAA finds that good cause exists to make
these special conditions effective upon issuance.
Conclusion
This action affects only certain design features on the Jetsteam
Model 4101 airplane. It is not a rule of general applicability and
affects only the manufacturer who applied to the FAA for approval of
these features on the airplane.
The substance of these special conditions has been subject to the
notice and public comment procedure in a recent instance with no
comment. For this reason and because a delay would significantly affect
the applicant's installation of the system and certification of the
airplane, which is imminent, the FAA has determined that good cause
exists for adopting these special conditions without notice. Therefore,
special conditions are being issued for this airplane and made
effective upon issuance.
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. app. 1344, 1348(c), 1352, 1354(a), 1355,
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et
seq.; E.O. 11514; and 49 U.S.C. 106(g).
The Special Conditions
According, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the Jetstream Model 4101 airplane.
(a) General: An ATTCS is defined as the entire automatic system,
including all devices, both mechanical and electrical, that sense
engine failure, transmit signals, actuate fuel controls or power
levers, or increase engine power by other means on operating engines to
achieve scheduled thrust or power increases and furnish cockpit
information on system operation.
(b) Automatic takeoff thrust control system (ATTCS). The engine
power control system that automatically resets the power or thrust on
the operating engine (following engine failure during the approach for
landing) must comply with the following requirements:
(1) Performance and System Reliability Requirements. The
probability analysis must include consideration of ATTCS failure
occurring after the time at which the fightcrew last verifies that the
ATTCS is in a condition to operate until the beginning of the critical
time interval.
(2) Thrust Setting. The initial takeoff thrust set on each engine
at the beginning of the takeoff roll or go-around may not be less than:
[[Page 63903]]
(i) Ninety (90) percent of the thrust level set by the ATTCS (the
maximum takeoff thrust or power approved for the airplane under
existing ambient conditions);
(ii) That required to permit normal operation of all safety-related
systems and equipment dependent upon engine thrust or power lever
position; and
(iii) That shown to be free of hazardous engine response
characteristics when thrust is advanced from the initial takeoff thrust
or power to the maximum approved takeoff thrust or power.
(3) Powerplant Controls. In addition to the requirements of
Sec. 25.1141, no single failure or malfunction, or probable combination
thereof, of the ATTCS, including associated systems, may cause the
failure of any powerplant function necessary for safety. The ATTCS must
be designed to:
(i) Apply thrust or power on the operating engine(s), following any
one engine failure during takeoff or go-around, to achieve the maximum
approved takeoff thrust or power without exceeding engine operating
limits; and
(ii) Provide a means to verify to the flightcrew before takeoff and
before beginning an approach for landing that the ATTCS is in a
condition to operate.
(c) Critical Time Interval. The definition of the Critical Time
Interval in Appendix I, Sec. I25.(b) shall be expanded to include the
following:
(1) When conducting an approach for landing using ATTCS, the
critical time interval is defined as follows:
(i) The critical time interval begins at a point on a 2.5 degree
approach glide path from which, assuming a simultaneous engine and
ATTCS failure, the resulting approach climb flight path intersects a
flight path originating at a later point on the same approach path
corresponding to the Part 25 one-engine-inoperative approach climb
gradient. The period of time from the point of simultaneous engine and
ATTCS failure to the intersection of these flight paths must be no
shorter than the time interval used in evaluating the critical time
interval for takeoff beginning from the point of simultaneous engine
and ATTCS failure and ending up reaching a height of 400 feet.
(ii) The critical time interval ends at the point on a minimum
performance, all-engines-operating go-around flight path from which,
assuming a simultaneous engine and ATTCS failure, the resulting minimum
approach climb flight path intersects a flight path corresponding to
the Part 25 minimum one-engine-inoperative approach climb gradient. The
all-engines-operating go-around flight path and the Part 25 one-engine-
inoperative approach climb gradient flight path originate from a common
point on a 2.5 degree approach path. The period of time from the point
of simultaneous engine and ATTCS failure to the intersection of these
flight paths must be no shorter than the time interval used in
evaluating the critical time interval for the takeoff beginning from
the point of simultaneous engine and ATTCS failure and ending upon
reaching a height of 400 feet.
(2) the critical time interval must be determined at the altitude
resulting in the longest critical time interval for which one-engine-
inoperative approach climb performance data are presented in the
Airplane Flight Manual.
(3) The critical time interval is illustrated in the following
figure:
BILLING CODE 4910-12-M
[GRAPHIC][TIFF OMITTED]TR13DE95.000
[[Page 63904]]
*The engine and ATTCS failed time interval must be no shorter
than the time interval from the point of simultaneous engine and
ATTCS failure to a height of 400 feet used to comply with I25.2(b)
for ATTCS use during takeoff.
Issued in Renton, Washington, on December 6, 1995.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, AMN-100.
[FR Doc. 95-30366 Filed 12-12-95; 8:45 am]
BILLING CODE 4910-13-M
