### UNITED STATES OF AMERICA DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION RENTON, WASHINGTON 98057-3356

In the matter ofthe petition of 

### Exemption No. 

### 13477

The Boeing Company Regulatory DocketNo. 

### FAA-2015-0469
for an exemption from§ 25.345(c) of Title 14, Code ofFederal Regulations



### GRANT OF EXEMPTION
By letter dated February 19, 2015, Mr. David Horn, ODALead Administrator, The Boeing Company, 6001 S. Air Depot, Oklahoma City, Oklahoma, 73135, petitioned the Federal Aviation Administration (FAA) for an exemption from the requirements of§ 25.345(c) ofTitle 14, Code ofFederal Regulations (14 CFR). This exemption, ifgranted, would allow deployment ofhigh lift devices duringprolonged flight for the purpose ofmilitary aerial refueling operations on supplemental type certificate (STC) modified 767-2C tanker airplanes. The requested exemption would apply to military use only and would enable the refueling ofall aircraft that are currently refueled by KC-135 and KC-10A tankers.


### The petitioner requests relieffrom the following regulations: Section 25.345(c) at Amendment 25-91- Ifflaps or other high lift devices are to be used in en route conditions, and with flaps in the appropriate position at speeds up to the flap design speed chosen for these conditions, the airplane is assumed to be subjected to symmetrical maneuvers and gusts withinthe range determined by-- (1) Maneuveringto a positive limit load factor as prescribed in Sec. 25.337(b); and (2) The discrete vertical gust criteria in Sec. 25.341(a).


### The petitioner supports its request with the following information:
This section quotes the relevant information from the petitioner's request, with minor edits for clarity. The completepetition is available at the Department ofTransportation's Federal Docket Management System, on the Internet at http://regulations.gov, in DocketNo. FAA-2015-0469.

### Description ofIssue The United States AirForce (USAF) requires that the KC-46A (or 767-2C) be capable of refueling all aircraft that may currentlybe refueled using KC-135 or KC-10A tankers. Some ofthese receiver aircraftrefuel at low speeds that would require prolonged flight withhigh lift devices deployed during aerial refueling operations. The intent ofthe requirement of§ 25.345(c) maybe satisfied by consideration ofthe expected usage ofthe KC-46A airplane, operational procedures, and inherent structural capability. Note that the KC-10A requires a similar low speed refueling envelope with flaps down operation. The current en route flap requirements of§ 25.345(c) were notpart ofthe KC1

OA certification basis. Expected Usage
Low speed refueling should be regarded as a customer required capability and not as common usage as envisioned by the regulation. This capability is expected to be utilized very infrequently as these flaps down refueling events are not part ofthe KC-X specification mission profiles which form the basis for structural durability evaluation. For any KC-46A, the frequency oflow altitude refueling missions, including flaps down refueling, is expected to be less than 10 hours peryear, equivalentto 10"2 

### per flight hour. Flaps down refueling operations are low speed, in the range of 185 to 200 KIAS and belowthe flaps down maximum altitude limit of20,000 ft. Flaps will not be deployed during high speed orhigh altitude flight. Only takeoffflap settings, detents 1, 5, 15, and 20, may be used. Since flaps 1and 5 are sufficient to perform these missions, flaps 15 and 20 usage is expected to be rare. This operation is expected to be very infrequent. Therefore,the cumulative lifetime refueling flaps down operation is not significant both from an exposure to elevated maneuver and gust environment and effects on the overall structural durability. Operational Procedures
For aerial refueling operations, turbulence is avoided and the fuel offload maneuvering limit is 1.5g's. Similar to the KC-10A aerial refueling operations manual, the KC-46A operations manual will instruct the flight crew to terminate refueling ifmoderate turbulence is encountered.
Situational awareness is high due to proximity ofreceiver aircraft. When not in preparation or execution ofslowreceiver offload, the tanker aircraft would operate flaps up to minimize fuel bum during loiter segments. When not offloading, flaps down maneuver limits remain at the current airplane flight manual (AFM) limit, Og to 2g. Structural Capability
As discussed in the Amendment 25-46 publicationpreamble, the current requirement for consideration ofen route flaps is intended to address situations where the airplanes are 2"commonlyflown in en route conditions with flaps deployed for purposes otherthan as speed brakes, and the airplane structure should be designed for the appropriate loads regardless ofthe operational reason." Sufficient and appropriate structural capability for the expected flaps down refueling operations is providedby the existing design bothfor offload operations and for loading conditions following disconnect.
Inthe eventthat severe turbulence is encountered during aerial refueling operations, the KC-46A structural capability is sufficient for the effects ofthe gust andrapid refueling termination and disconnect. Rapid disconnects and resulting fuel pressure transients are addressed in the basic USAF approved aerial refueling criteria. In the event ofa rapid disconnect followed by high maneuvering or severe gusts, the aircraft loads are limited by airplane lift capability to the existing structural capability as described below. During operationin the low speedrefueling regime, the vertical maneuvering and gust loads are naturally limited by airplane maximum lift capabilityto envelopes comparable to the flaps down envelope required by§ 25.345(a). Encounters with severe head on gusts, while notrequired by§ 25.345(c), are also very unlikely to exceed structural capability duringthese operations.
Since flaps 1 and 5 are expected to be used more often, the maneuvering and gust capabilities are shown for flaps 5, the most critical. Flaps 15 and 20 are available, but refueling operations with these settings is expected to be rare and are not considered. 

### Statement ofPublic Interest
The USAF requires thatthe KC-46A be capable ofrefueling all aircraftthat may currently berefueled using KC-135 or KC-1OA tankers. Some ofthese receiver aircraft refuel at low speeds that would require prolongedflight with high lift devices deployed during aerial refueling operations. Application of§ 25.345(c) would cause significant modification to the airplane that would provide no net benefit inthe configuration and no commensurate increase in safety. Ifthe reliefis not granted, it could lead to delays inthe delivery ofthe STC-modified 767-2C to the USAF at a critical time ofneed. 

### It remains inthe public interestto grant Boeing an exemption to§ 25.345(c) for the STC-modified 767-2C airplane

. 

### Statement ofNo Adverse Effect on Safety
The petitionerrequests thatthis petition for exemptionnot be delayed by the public process, which includes publication ofthe subjectpetition. Ifthis exemption is not granted, it could lead to delays in the delivery ofthe STC-modified 767-2C to the USAF at a critical time ofneed. The STC-modified 767-2C approved aircraft will notbe eligible to receive a civil airworthiness approval or standard certificate ofairworthiness. 

### It is intended that the aircraft will be maintained as a public use aircraft only for the life of the product.

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### Federal Register publication Althoughthe petitionerrequested that action on its petition notbe delayed for publication in the Federal Register, the FAA found thatthe petition, ifgranted, would set a precedent. Therefore, to allow an opportunity for the public to comment on the petition, we published a summary ofit inthe Federal Register on July 10, 2015 (80 FR 39830). No comments were received. 

### The FAA's analysis
Aerial refueling is not an approved operation ofcommercial airplanes and the requested exemption only applies to military refueling operations. The 767-2C airplane is not currently commercially available; however, we recognize that future sales or conversions could include airplanes that are the subject ofthis exemption andthese airplanes could beused in commercial service. Boeing addresses this concernby providing operating limitations inthe AFMthatwill prevent aerial refueling operations in commercial service. The intended use ofthis airplane is military aerial refueling and not commercial operation. As stated bythe petitioner, low speed refueling is not considered common usage for commercial airplanes envisioned by the regulation and also is expected to occurvery infrequently. The airplane's design has shown sufficient and appropriate structural capability for the expectedflaps down refueling operations, and the operations manual provides appropriate instructions if moderate turbulence is encountered during these operations. This exemption will not adversely impactpublic safety. We agree that granting this exemption is in the public interest because it will preventexpenditure oftaxpayer dollars on unnecessary structural modifications and it will enhance the United States military byreplacing older, less efficient tanker airplanes and ensure consistency within the current USAF fleet.


### The FAA's decision
In consideration ofthe foregoing, I find that a grant ofexemption is in the public interest. Therefore, pursuantto the authority contained in 49 U.S.C. 40113 and 44701 delegated to me by the Administrator, I grant The Boeing Company an exemption from 14 CFR25.345(c). The exemption is granted to the extent necessaryto allow deployment ofhigh lift devices during prolonged flight for the purpose ofmilitary refueling operations on STC modified 767-2C military tanker airplanes.

Issued inRenton, Washington, on 

### 0 C

T

· 302015

Michael Kaszycki Acting Manager, Transport Airplane Directorate Aircraft Certification Service

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