[Federal Register Volume 86, Number 56 (Thursday, March 25, 2021)]
[Rules and Regulations]
[Pages 15780-15784]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-06027]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2020-0721; Special Conditions No. 25-785-SC]


Special Conditions: Mitsubishi Aircraft Corporation Model MRJ-200 
Airplane; Use of Automatic Power Reserve for Go-Around Performance 
Credit

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 Mitsubishi 
Aircraft Corporation (MITAC) Model MRJ-200 airplane. This airplane will 
have a novel or unusual design feature when compared to the state of 
technology envisioned in the airworthiness standards for transport-
category airplanes. This design feature is an Automatic Takeoff Thrust 
Control System (ATTCS), referred to as an Automatic Power Reserve 
(APR), to set the performance level for approach-climb operation after 
an engine failure. 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: This action is effective on MITAC on March 25, 2021. Send 
comments on or before May 10, 2021.

ADDRESSES: Send comments identified by Docket No. FAA-2020-0721 using 
any of the following methods:
     Federal eRegulations Portal: Go to http://www.regulations.gov/ and follow the online instructions for sending 
your comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
     Privacy: Except for Confidential Business Information 
(CBI) as described in the following paragraph, and other information as 
described in 14 CFR 11.35, the FAA will post all comments received 
without change, to http://www.regulations.gov/, including any personal 
information you provide. The FAA will also post a report summarizing 
each substantive verbal contact received about this proposal.
     Confidential Business Information: Confidential Business 
Information (CBI) is commercial or financial information that is both 
customarily and actually treated as private by its owner. Under the 
Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from 
public disclosure. If your comments responsive to this Notice contain 
commercial or financial information that is customarily treated as 
private, that you actually treat as private, and that is relevant or 
responsive to this Notice, it is important that you clearly designate 
the submitted comments as CBI. Please mark each page of your submission 
containing CBI as ``PROPIN.'' The FAA will treat such marked 
submissions as confidential under the FOIA, and the indicated comments 
will not be placed in the public docket of this Notice. Send 
submissions containing CBI to the person indicated in the Contact 
section below. Comments the FAA receives, which are not specifically 
designated as CBI, will be placed in the public docket for this 
rulemaking.
     Docket: Background documents or comments received may be 
read at http://www.regulations.gov/ at any time. Follow the online 
instructions for accessing the docket or go to Docket Operations in 
Room W12-140 of the West Building Ground Floor at 1200 New Jersey 
Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday through 
Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Joe Jacobsen, Performance and 
Environment Section, AIR-625, Technical Innovation Policy Branch, 
Policy and Innovation Division, Aircraft Certification Service, Federal 
Aviation Administration, 2200 South 216th Street, Des Moines, 
Washington 98198; telephone and fax 206-231-3158; email 
joe.jacobsen@faa.gov.

[[Page 15781]]


SUPPLEMENTARY INFORMATION: The substance of these special conditions 
has been published in the Federal Register for public comment in 
several prior instances with no substantive comments received. 
Therefore, the FAA has determined that prior public notice and comment 
are unnecessary, and finds that, for the same reason, good cause exists 
for adopting these special conditions upon publication in the Federal 
Register.

Comments Invited

    The FAA invites interested people to take part in this rulemaking 
by sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    The FAA will consider all comments received by the closing date for 
comments. The FAA may change these special conditions based on the 
comments received.

Background

    On March 3, 2015, MITAC applied for a type certificate for their 
new Model MRJ-200 airplane. This airplane is a twin-engine, transport-
category airplane with seating for 92 passengers and a maximum takeoff 
weight of 98,767 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.17, the applicant must show that the airplane meets the 
applicable provisions of 14 CFR part 25, as amended by amendments 25-1 
through 25-141.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the MITAC Model MRJ-200 airplane 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec.  21.16.
    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, these special conditions would also apply to 
the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the MITAC Model MRJ-200 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 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The MITAC Model MRJ-200 airplane will incorporate the following 
novel or unusual design feature:
    An Automatic Takeoff Thrust Control System, referred to as an 
Automatic Power Reserve, to set the performance level for approach-
climb operation after an engine failure.

Discussion

    MITAC included an APR system (an ATTCS) in the Model MRJ-200 
airplane and proposed using the APR function during go-around. They 
also requested approach-climb performance credit for the use of 
additional thrust set by the APR system. The MITAC Model MRJ-200 
powerplant control system comprises a Full Authority Digital Engine 
Control (FADEC) for the engine. The engine FADEC system utilizes the 
APR function during the takeoff and go-around phases of the flight when 
additional thrust is needed from an operating engine following a single 
engine failure. The APR system is available at all times, without any 
additional action from the pilot. It allows the pilot to use the same 
power-setting procedure during a go-around regardless of whether or not 
an engine fails. Because the APR system is always armed, it will 
function automatically following an engine failure, and advance the 
remaining engine to a higher thrust level.
    The part 25 standards for ATTCS, contained in Sec.  25.904, and 
appendix I to part 25, specifically restrict performance credit for 
ATTCS to takeoff. Expanding 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 the preamble of amendment 25-62 states:
    In regard to ATTCS credit for approach-climb and go-around 
maneuvers, current regulations preclude a higher power 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 power settings in the event of an engine failure 
during a critical point in the approach, landing, or go-around 
operations is excessive. Therefore, the amendment should not include 
the use of ATTCS for anything except the takeoff phase.
    Because the airworthiness regulations do not contain appropriate 
safety standards to allow approach-climb performance credit for ATTCS, 
special conditions are required to ensure a level of safety equivalent 
to that established in the regulations. 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. In the event 
of a simultaneous failure of both an engine and the APR function, 
falling below the minimum flight path defined by the 2.5-degree 
approach, decision height, and climb gradient required by Sec.  
25.121(d) must be shown to be an extremely improbable event during this 
critical time interval. 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.
    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.

Applicability

    As discussed above, these special conditions are applicable to the 
MITAC Model MRJ-200 airplane. Should MITAC 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.

Conclusion

    This action affects only a certain novel or unusual design feature 
on one model of airplanes. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the

[[Page 15782]]

Administrator, the following special conditions are issued as part of 
the type certification basis for MITAC Model MRJ-200 airplanes.
    1. The MITAC Model MRJ-200 airplane must comply with the 
requirements of 14 CFR 25.904, and appendix I, and the following 
requirements for the go-around phase of flight:
    2. Definitions
    a. Takeoff/go-around (TOGA): Throttle lever in takeoff or go-around 
position.
    b. Automatic Takeoff Thrust Control System: The ATTCS in MITAC 
Model MRJ-200 airplanes is defined as the entire automatic system 
available during takeoff and in go-around mode, 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 increase), and furnish cockpit information on system 
operation.
    c. Critical time interval:
    (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 that 
corresponds 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.
    (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 Figure 1:
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[[Page 15783]]

[GRAPHIC] [TIFF OMITTED] TR25MR21.002

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    The all-engines-operating go-around flight path, and the part 25 
one-engine-inoperative approach-climb gradient flight path (engine 
failed, ATTCS operating path in Figure 1), originate from a common 
point, point C, on a 2.5-degree approach path. The period of time, 
``time interval DE,'' from the point of simultaneous engine and ATTCS 
failure, point D, to the intersection of these flight paths, point E, 
must be no shorter than the corresponding time in Figure 2, above.
    d. The ``critical time interval AD'' is illustrated in Figure 1.
    3. Performance and system reliability requirements: The applicant 
must comply with the performance and

[[Page 15784]]

ATTCS reliability requirements as follows:
    a. An ATTCS failure or a combination of failures in the ATTCS 
during the critical time interval (Figure 1):
    (1) Must not prevent the insertion of the maximum approved go-
around thrust or power, or must be shown to be a remote event.
    (2) Must not result in a significant loss or reduction in thrust or 
power, or must be shown to be an extremely improbable event.
    b. The concurrent existence of an ATTCS failure and an engine 
failure during the critical time interval must be shown to be extremely 
improbable.
    c. All applicable performance requirements of part 25 must be met 
with an engine failure occurring at the most critical point during go-
around with the ATTCS functioning.
    d. 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.
    e. The propulsive thrust obtained from the operating engine, after 
failure of the critical engine during a go-around used to show 
compliance with the one-engine-inoperative climb requirements of Sec.  
25.121(d), may not be greater than the lesser of:
    (1) The actual propulsive thrust resulting from the initial setting 
of power or thrust controls with the ATTCS functioning, or
    (2) 111 percent of the propulsive thrust resulting from the initial 
setting of power or thrust controls with the ATTCS failing to reset 
thrust or power, and without any action by the flightcrew to reset 
thrust or power.
    4. Thrust setting
    a. The initial go-around thrust setting on each engine at the 
beginning of the go-around phase may not be less than any of the 
following:
    (1) That required to permit normal operation of all safety-related 
systems and equipment dependent upon engine thrust or power lever 
position; or
    (2) That are shown to be free of hazardous engine-response 
characteristics, and not to result in any unsafe airplane operating or 
handling characteristics when thrust or power is advanced from the 
initial go-around position to the maximum approved power setting.
    b. For approval to use an ATTCS for go-arounds, the thrust-setting 
procedure must be the same for go-arounds initiated with all engines 
operating as for go-around initiated with one engine inoperative.
    5. Powerplant controls
    a. 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.
    b. The ATTCS must be designed to:
    (1) Apply thrust or power to the operating engine(s), following any 
one-engine failure during a go-around, to achieve the maximum approved 
go-around thrust without exceeding the engine operating limits;
    (2) Permit manual decrease or increase in thrust or power up to the 
maximum go-around thrust approved for the airplane, under the existing 
conditions, through the use of the power lever. For airplanes equipped 
with limiters that automatically prevent the engine operating limits 
from being exceeded under existing ambient conditions, other means may 
be used to increase the thrust in the event of an ATTCS failure, 
provided that the means:
    (i) Is located on or forward of the power levers;
    (ii) Is easily identified and operated under all operating 
conditions by a single action of either pilot with the hand that is 
normally used to actuate the power levers; and
    (iii) Meets the requirements of Sec.  25.777(a), (b), and (c).
    (3) Provide a means to verify to the flightcrew, before beginning 
an approach for landing, that the ATTCS is in a condition to operate 
(unless it can be demonstrated that an ATTCS failure, combined with an 
engine failure during an entire flight, is extremely improbable).
    6. Powerplant instruments: In addition to the requirements of Sec.  
25.1305:
    a. A means must be provided to indicate when the ATTCS is in the 
armed or ready condition; and
    b. If the inherent flight characteristics of the airplane do not 
provide adequate warning that an engine has failed, a warning system 
that is independent of the ATTCS must be provided to give the pilot a 
clear warning of any engine failure during a go-around.

    Issued in Kansas City, Missouri, on March 17, 2021.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2021-06027 Filed 3-24-21; 8:45 am]
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