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Federal Register / Vol. 86, No. 56 / Thursday, March 25, 2021 / Rules and Regulations
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 oneengine-inoperative climb requirements of 25.121d, 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
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a. In addition to the requirements of 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 engines, following any oneengine failure during a go-around, to achieve the maximum approved goaround 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 25.777a, 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 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.

DEPARTMENT OF TRANSPORTATION

Issued in Kansas City, Missouri, on March 17, 2021.
Patrick R. Mullen, Manager, Technical Innovation Policy Branch, Policy and Innovation Division, Aircraft Certification Service.

You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20200710; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, any comments received, and
FR Doc. 202106027 Filed 32421; 8:45 am BILLING CODE 491013P

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Federal Aviation Administration 14 CFR Part 39
Docket No. FAA20200710; Project Identifier 2019CE037AD; Amendment 3921457; AD 20210514
RIN 2120AA64

Airworthiness Directives; Air Tractor, Inc., Airplanes Federal Aviation Administration FAA, DOT.
ACTION: Final rule.
AGENCY:

The FAA is adopting a new airworthiness directive AD for all Air Tractor, Inc., Air Tractor Models AT
250, AT300, AT301, AT302, AT
400, AT400A, AT401, AT401A, AT
401B, AT402, AT402A, AT402B, AT501, AT502, AT502A, AT502B, AT503, AT503A, AT504, AT602, AT802, and AT802A airplanes. This AD was prompted by reports of cracks in the flap torque tube actuator attachment brackets that may cause the flap actuator to detach from the flap torque tube. This AD requires repetitive visual and dye penetrant inspections of the flap actuator attachment bracket welds for cracks and replacement if cracks are identified. The FAA is issuing this AD to address the unsafe condition on these products.
DATES: This AD is effective April 29, 2021.
The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD
as of April 29, 2021.
ADDRESSES: For service information identified in this final rule, contact Air Tractor, P.O. Box 485, Olney, TX 76374:
phone: 940 5645616: email: info@
airtractor.com: website: https
airtractor.com/. You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call 8163294148. It is also available at https www.regulations.gov by searching for and locating Docket No.
FAA20200710.
SUMMARY:

Examining the AD Docket
E:FRFM25MRR1.SGM

25MRR1