[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]



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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.

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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