[Federal Register Volume 64, Number 155 (Thursday, August 12, 1999)]
[Proposed Rules]
[Pages 43943-43946]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-20857]
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Proposed Rules
Federal Register
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This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 64, No. 155 / Thursday, August 12, 1999 /
Proposed Rules
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR part 25
[Docket No. NM162; Notice No. 25-99-08-SC]
Special Conditions: Bombardier Model DHC-8-400 Airplane;
Automatic Takeoff Thrust Control System
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This notice proposes special conditions for the Bombardier
Model DHC-8-400 series airplanes. This new airplane will have a novel
or unusual design feature associated with an Automatic Takeoff Thrust
Control System (ATTCS). The applicable airworthiness regulations do not
contain appropriate safety standards for approach climb performance
using an ATTCS. 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: Comments must be received on or before September 13, 1999.
ADDRESSES: Comments on this proposal may be mailed in duplicate to:
Federal Aviation Administration, Transport Airplane Directorate,
Attention: Rules Docket (ANM-14), Docket No. NM162, 1601 Lind Avenue
SW., Renton, Washington, 98055; or delivered in duplicate to the
Transport Airplane Directorate at the above address. Comments must be
marked ``Docket No. NM162.'' Comments may be inspected in the Rules
Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Greg Dunn, FAA, Transport Airplane
Directorate, Aircraft Certification Office, Standardization Branch,
ANM-113, 1601 Lind Avenue SW., Renton, Washington, telephone (425) 227-
2799; facsimile (425) 227-1149.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of
these proposed special conditions by submitting such written data,
views, or arguments, as they may desire. Communications should identify
the regulatory docket or notice 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.
The proposals described in this notice may be changed in light of the
comments received. All comments received 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 notice must include with those
comments a self-addressed, stamped postcard on which the following
statement is made: ``Comments to Docket No. NM162.'' The postcard will
be date stamped and returned to the commenter.
Background
On January 31, 1995, Bombardier Regional Aircraft, 123 Garratt
Blvd., Downsview, Ontario, France, M3K 1Y5, applied for an amended type
certificate to include the new Bombardier Model DHC-8-400 airplane. The
Bombardier Model DHC-8-400, which is a derivative of the Bombardier
(formerly de Havilland, Inc.) Model DHC 8-300 series airplanes
currently under Type Certificate No. A13NM is a medium-sized airplane
powered by two Pratt & Whitney Canada PW150A turbopropeller engines
mounted on the wings. Each engine is equipped with a Dowty Aerospace
Model R408 propeller and is capable of delivering 5071 horsepower at
takeoff. The airplane is configured for five flight crewmembers and 78
passengers.
The Bombardier Model DHC-8-400 incorporates an unusual design
feature, the Automatic Takeoff Thrust Control System (ATTCS), referred
to by Bombardier as uptrim, 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 14 CFR 21.101, Bombardier must show that
the Model DHC-8-400 meets the applicable provisions of the regulations
incorporated by reference in Type Certificate No. A13NM or the
applicable regulations in effect on the date of application for the
change to the type certificate. 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. A13NM are as follows: part 25,
effective February 1, 1965, including Amendments 25-1 through 25-86,
and Sec. 25.109 as amended by Amendment 92. The certification basis may
also include later amendments to part 25 that are not relevant to these
special conditions. In addition, the certification basis for the Model
DHC-8-400 includes part 34, effective September 10, 1990, including
Amendment 34-3 effective February 3, 1999, plus any amendments in
effect at the time of certification; and part 36, effective December 1,
1969, including Amendments 36-1 through 36-21 and any subsequent
amendments which will be applicable on the date the type certificate is
issued. These special conditions form an additional part of the type
certification basis. In addition, the certification basis may include
other special conditions that are not relevant to these special
conditions.
If the Administrator finds that the applicable airworthiness
regulations (i.e., part 25, as amended) do not contain adequate or
appropriate safety standards for the Bombardier Model DHC-8-400 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 DHC-8-400 must
[[Page 43944]]
comply with the fuel vent and exhaust emission requirements of 14 CFR
part 34 and the noise certification requirements of 14 CFR part 36.
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).
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, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
Novel or Unusual Design Features
The Model DHC-8-400 will incorporate the following novel or unusual
design feature: the Automatic Takeoff Thrust Control System (ATTCS),
referred to by Bombardier as uptrim, to show compliance with the
approach climb requirements of Sec. 25.121(d). The Bombardier Model
DHC-8-400 is a medium-sized airplane powered by two Pratt & Whitney
Canada PW150A turbopropeller engines equipped with Full Authority
Digital Engine Controls (FADEC) that, in part, protect against
exceeding engine limits. The Model DHC-8-400 is also equipped with
Dowty Aerospace Model R408 propellers as part of the propulsion
package. The propellers incorporate a Propeller Electronic Control
(PEC) that functions with the FADEC to control the engine/propeller
system.
The Model DHC-8-400 incorporates a non-moving throttle system that
functions by placing the throttle levers in detents for the takeoff and
climb phases of flight, allowing the FADEC to schedule power settings
based on flight phase. With the uptrim and associated systems
functioning normally as designed, all applicable requirements of part
25 of the Federal Aviation Regulations (FAR) and paragraph 25 of the
Joint Aviation Requirements (JAR), will be met without requiring any
action by the crew to increase power.
Automatic takeoff power control on the Model DHC-8-400 involves
uptrimming the remaining engine to Maximum Takeoff Power (MTOP) and
autofeathering the propeller on the failed engine. These actions will
be controlled by the PEC. At takeoff when AUTOFEATHER (A/F) is selected
and the power levers are set to Normal Takeoff Power (NTOP), an ``A/F
ARM'' message on the engine display will confirm to the pilot that the
system is armed and autofeather and uptrim will occur without any
further action by the crew if an engine fails. During go-around the
uptrim will be automatically armed as soon as the control (power)
levers are set to the takeoff (go-around) configuration.
Engine power is set to NTOP, which is 90 percent of MTOP, to
initiate the takeoff roll. The value of NTOP for the current ambient
conditions will be calculated and set by the FADEC. Following an engine
failure during takeoff or go-around, the ATTCS will change the power
reference on the operating engine to achieve the MTOP rating if the
engine power was originally set to NTOP. If the reduced power takeoff
option is being used the ATTCS will increase the power of the operating
engine from 90 percent to 100 percent of the corresponding set power.
The engine operating limits (turbine temperature and RPM) for NTOP
are set and displayed to the pilot when that rating is selected. These
limits are set such that the engine red line limits are not exceeded
when an uptrim is applied. When MTOP rating is selected or triggered,
the engine limits are reset automatically to reflect the engine red
line limits.
When both Power Lever Angles (PLA) are high and both the Condition
Lever Angles (CLA) are at maximum position (MAX), the system is armed.
If the torque on one engine drops below 25 percent, the PEC on the
failed engine sends an uptrim signal to the remaining engine. Other
conditions that will trigger the uptrim are the reduction of prop speed
(Np) below 80 percent or the automatic feathering of the prop. The
power levers will continue to function normally should the ATTCS fail.
The MTOP can also be selected by pressing the ``MTOP'' switch on the
engine control panel. The full MTOP is available if the pilot elects to
push the PLA past the takeoff power detent into the over travel range.
To deactivate the uptrim, the PLA's should be moved out of the
rating detent to a position less than 60 degrees (PLA not high) or the
CLA of the active engine should be moved out of the MAX/1020 takeoff
detent.
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 Model DHC-8-400 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 moving the throttles into the forward (takeoff/go-
around) throttle detent. Since the ATTCS is permanently armed, it will
function automatically following an engine failure, and advance the
remaining engine to the ATTCS thrust level. Therefore, this design
adequately addresses the pilot workload concerns identified in the
preamble to Amendment 25-62. Accordingly, these proposed special
conditions would require a showing of compliance with those provisions
of Sec. 25.904 and Appendix I that are applicable to the approach climb
and go-around maneuvers.
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.
Applicability
As discussed above, these proposed special conditions would be
applicable to the Bombardier Model DHC-8-400. Should Bombardier 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).
[[Page 43945]]
Conclusion
This action affects only certain design features on the Bombardier
Model DHC-8-400 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.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these proposed 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 the Bombardier Regional Aircraft Model DHC-8-400 airplane.
1. General. An Automatic Takeoff Thrust Control System (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.
2. 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:
a. Performance and System Reliability Requirements. The probability
analysis must include consideration of ATTCS failure occurring after
the time at which the flightcrew last verifies that the ATTCS is in a
condition to operate until the beginning of the critical time interval.
b. 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:
(1) 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);
(2) That required to permit normal operation of all safety-related
systems and equipment dependent upon engine thrust or power lever
position; or
(3) 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.
c. 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:
(1) 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
(2) 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.
3. Critical Time Interval. The definition of the Critical Time
Interval in Appendix I, Section I25.2(b) shall be expanded to include
the following:
a. When conducting an approach for landing using ATTCS, the
critical time interval is defined as follows:
(1) 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 upon reaching a height of 400 feet.
(2) 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.
b. 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.
c. The critical time interval is illustrated in the following
figure:
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[GRAPHIC] [TIFF OMITTED] TP12AU99.007
* 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 August 4, 1999.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate Aircraft Certification
Service, ANM-100.
[FR Doc. 99-20857 Filed 8-11-99; 8:45 am]
BILLING CODE 4910-13-P
