U.S. Department 

of Transportation 

Federa l Aviation 

Administration 

October 17, 2014 

Douglas M. Lane 

Director 

The Boeing Company 

PO Box 3707 

Seattle, Washington. 98124 

Dear Mr. Lane: 

Transport Airplane Directorate 

1601 Lind Ave, SW. 

Renton, Washington 98057-3356 

Exemption No. 11086 

Regulatory Docket No. F AA-20 13-0767 

This letter is to inform yo u that we have granted your request for exemption. It transmits our 

decision and explains its basis. 

The Basis for Our Decision 

By letter RA-13-03942 elated August 26, 2013, Mr. Thomas Howorth, on behalf of The Boeing 

Company, petitioned the Federal Aviation Administration (FAA) for an exemption from the 

requirements of~ 25.961(a)(5) of Title 14, Code of Federal Regulations (14 CFR) as it relates to 

fuel-system hot-weather operation. The request seeks relief from these requirements for Boeing 

Model 767-2C a irplanes. 

The FAA has issued grants of exemption. with operational limits, in circumstances similar in all 

material respects to those presented in your petition, including for Boeing Model 747-400 and 

757 series airplanes using JP-4 and Jet B fuel. 

Having reviewed you r reasons for requesting an exemption, I find that-

• they don't diffcr materiall y hom those presented by the petitioner in the enclosed grant of 

exemption: 

• the reasons stated by the FAA for granting the enclosed exemption also apply to the 

situation you present: and 

• a grant of exemption is in the public interest. 
Federal Register Publication 

The FAA has determined that good cause exists for not publishing a summary of the petition in 

the Federal Register because the requested exemption would not set a precedent, the FAA has 

not received public comments on other exemption requests for relief from § 25.961 (a)( 5), fuelsystem hot-weather operation, and any delay in acting on this petition would be detrimental to 

The Boeing Company. 

Our Decision 

Under the authority contained in 49 U.S.C. 40113 and 44701, which the FAA Administrator has 

delegated to me, I hereby grant The Boeing Company an exemption from the requirements of 

14 CFR 25.961(a)(5) as it relates to fuel-system hot-weather operation on Boeing Model 767-2C 

airplanes. 

All "Operational Limits" described in the "Grant of Exemption" section of exemption 7790 also 

apply to this exemption. 

Sincerely, 

Michael Kaszycki 

Acting Manager, Transport Airplane Directorate 

Aircraft Certification Service 

Enclosure 
Exemption No. 7790 

UNITED STATES OF AMERICA 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

RENTON, WASHINGTON 98055-4056 

In the matter of the petition of 

The Boeing Company 

for an exemption from§ 25.961(a)(5) of 

Title 14, Code ofFederal Regulations 

Regulatory Docket No. FAA-2001-11155 

GRANT OF EXEMPTION 

By letter dated November 8, 2001 (B-H320-2001-00899), Mr. Edgars A. Kupcis, Manager, 

Certification, Certification & ETOPS Programs, B-H320, The Boeing Company, P.O. Box 3707, 

Seattle, WA 98124-2207, petitioned for an exemption from the requirements of§ 25.961(a)(5) at 

Amendment 25-85 of Title 14, Code of Federal Regulations (14 CFR) to permit The Boeing 

Company, for the Model 757-300 series airplanes powered by Pratt & Whitney PW2000 series 

engines, to be relieved of the requirement that the airplane and engines perform satisfactorily 

with the critical fuel at a temperature of at least 11 0°F. 

Sections of the Federal Aviation Regulations (FAR) Affected 

Section 25.961(a)(5), at Amendment 25-85, requires that the airplane and engines 

perform satisfactorily with the critical fuel at a temperature of at least 110°F. 

Petitioner's Supportive Information 

The Boeing Company's supportive information is summarized as follows: 

Boeing is introducing a Model 757-300 series airplane powered by Pratt & Whitney 

engines. The Model 757-200 series airplane with Pratt & Whitney engines was introduced 

in 1984, and has accumulated over 11.6 million flight hours of revenue service. The 

Model 757-300 series airplane with Rolls Royce engines was introduced in 1999 and has 

accumulated over 80,000 flight hours of revenue service. The Pratt & Whitney-powered 
Model 757-300 series airplane will offer three engines: PW2037, PW2040, and PW2043. 

The Model 757-200 series airplane offers PW2037 and PW2040 engines. 

Boeing is requesting relief from the requirements of 14 CFR 25.961(a)(5), at Amendment 

25-85, for the Pratt & Whitney-powered Model 757-300 series airplane. The regulation 

requires that the airplane and engines perform satisfactorily with the critical fuel at a 

temperature of at least 11 0°F. Boeing requests that the FAA approve a set of limitations 

for JP-4 (a military designation for a Jet B type commercial grade fuel with additives) and 

Jet B fuels on the Pratt & Whitney-powered Model 757-300 series airplane in lieu of 

compliance with the specified temperature of 11 0°F. The limitations consist of restricting 

the fuel temperature to 85°F, restricting the initial cruise altitude vs. fuel temperature, and 

restricting JP-4 and Jet B fuels to the main tanks only. These same limitations were 

approved for the Rolls Royce-powered Model 757-300 series airplane. 

Boeing submits this petition for the following reasons: 

( 1) It is in the public interest. Airline operators strongly desire the operational flexibility 

of JP-4 and Jet B fuels, and a maximum temperature of 85°F meets their needs. 

(2) The Model 757-200 series airplane with Pratt & Whitney PW2037 engines 

demonstrated satisfactory performance with JP-4 at 1 04°F. All Pratt & Whitneypowered Model 757-200 series airplanes are approved for JP-4 and Jet B use up to 

ll0°F. 

(3) There will be no significant differences in the fuel system between the Pratt & 

Whitney-powered Model 757-200 and the Model 757-300 series airplanes. 

( 4) The proposed limitations on fuel temperature, maximum altitude for initial cruise, and 

prohibition on the use of JP-4 and Jet B fuels in the center tank provide a level of 

safety equal to that intended by§ 25.961(a)(5). 

(5) The FAA granted a similar exemption for the Rolls Royce-powered Model 757-300 

series airplane (FAA Exemption No. 6867, issued Feb. 12, 1999, Regulatory Docket 

No. 29202). The Rolls Royce-powered Model 757-200 series airplane has had an 

85°F temperature limitation for JP-4 and Jet B fuels since entry into service in 1983. 

Public Interest 

Boeing argues that it is in the public interest that airlines be able to operate with JP-4 and 

Jet B fuels. These fuels are used in some parts of the world and are occasionally the only 

fuels available at military airfields that may serve as diversion airports. The economic 

impact of not being able to divert to these airfields in the event of an emergency is 

significant. When surveyed, several 757 operators reported that the loss of this capability 

would significantly impact their operations. Excerpts from two operators are provided 

below. 

The usage of JP-4 fuel is very rare, but in a few occasions it was necessary ... due to 

diversions to military airfields. Restricting the use of JP-4 fuel would heavily impact the 

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operation ... as several enroute alternates or destination alternates could no longer be 

chosen for flight planning. This is especially true for the areas of Alaska, Canada, 

Caribbean, Iran/Persia and Turkey. 

If the aircraft were not certificated to use JP-4/Jet B then each sector would need to be 

re-evaluated with respect to approved diversionary airfields and reserve fuel carried, so 

it is quite possible that there would be many routes which would cost more to operate 

and others where a decision would be made not to operate because of the capability of 

the aircraft. 

Boeing contends that the economic impact of full compliance with§ 25.961(a)(5) would 

be debilitating. It is unlikely that the existing Pratt & Whitney- and Rolls Royce-powered 

Model 757's or the upcoming Pratt & Whitney-powered Model 757-300 series airplanes 

would satisfy the performance requirements as they have been applied to recent new 

airplane programs with 11 0°F fuel. A major redesign to the airplane fuel feed system, 

fuel tanks, and potentially the airplane electrical system would be required to satisfy these 

requirements as most recently interpreted. These changes would involve an expensive recertification effort of the Model 757 fuel feed system with essentially no return on 

investment or enhancement of safety. It is probable these changes would introduce new 

failure modes into the present system that has proven very reliable in service. 

Level of Safety Provided 

With regard to§ 25.961(a)(5), the ability of an ·airplane to operate with JP-4 and Jet B 

fuels is a function of the vapor pressure of the fuel, which increases with temperature. 

The vapor pressure of wide cut fuels such as JP-4 and Jet B is considerably higher than 

that of narrow cut fuels such as Jet A. Under normal conditions, the aircraft fuel boost 

pumps maintain the pressure in the fuel feed system above the vapor pressure of the fuel. 

If all aircraft boost pumps are inoperative, the engine fuel pumps will continue to draw 

fuel out of the tanks to maintain engine operation. This condition is termed suction feed 

operation. At high fuel temperatures and high altitudes, the pressure in the fuel feed 

system can decrease to or reach a value near the vapor pressure of the fuel, allowing some 

fuel to vaporize and potentially causing engine flameout. Regulation§ 25.961(a)(5) 

addresses this condition, among others, and is intended to ensure that airplane operation 

will not be adversely impacted by fuel temperature. 

Boeing believes that incorporating a temperature limitation of 85°F for JP-4 and Jet B 

fuels provides a level of safety equal to that intended by the regulation. This position is 

based on several considerations: 

a) Differences between the Model 757-200 and Model 757-300 series airplane fuel 

systems do not affect suction feed operation. The changes include longer wiring 

between the fuel quantity indicating system processor and in-tank capacitance probes, 

a slightly increased allowable fuel volume for all three fuel tanks, and a longer fuel 

3 
feed hose to the auxiliary power unit. These changes were certified on the Rolls 

Royce-powered Model 757-300 series airplane. There are no further airplane fuel 

system changes planned for the Pratt & Whitney-powered Model 757-300 series 

airplane. 

b) There are no hardware differences between the PW203 7 /PW2040 engine fuel systems 

on the Model 757-200 and Model 757-300 series airplanes. 

c) Hardware differences between the PW2037/2040 and PW2043 engine fuel systems do 

not adversely affect suction feed operation. There are two changes in the engine fuel 

system to support the PW2043: the fuel control unit (FCU) and the fuel pump. The 

PW2043 FCU is the same basic unit as the PW2037/2040 FCU with a larger fuelmetering window. The PW2043 fuel pump is designed to match the performance of 

the PW2037/2040 pump with increased flow capacity at higher pump rotational 

speeds. The PW2043 pump was certified for use on the Model 757-200/PW2037 and 

PW2040 via bench and flight testing in June 2000. Suction feed requirements were 

substantiated by back-to-back rig testing. 

d) Thrust differences at maximum continuous thrust (MCT) between the PW203 7, 

PW2040, and PW2043 are offset by the temperature limitation of 85°F. The Model 

757-200 series airplane with PW2037 engines demonstrated satisfactory performance 

in suction feed operation with JP-4 fuel at a temperature of 104 °F. The slightly lower 

system pressure resulting from the increased fuel flow at PW2040 and PW2043 thrust 

is more than offset by the decreased vapor pressure between 1 04 °F and 85 °F. The 

slightly higher fuel pump rotor speed at PW2040 and PW2043 thrust has a negligible 

effect on the net positive suction pressure required by the pump to prevent cavitation. 

In addition to the temperature limitation, Boeing proposes to incorporate additional 

restrictions on altitude vs. temperature and center tank usage to further ensure an equal 

level of safety. The following limitations, already approved and incorporated in the Rolls 

Royce-powered Model 757-300 airplane flight manual, are proposed for the Pratt & 

Whitney-powered Model 757-300 airplane flight manual: 

(1) JP-4 or Jet B fuel shall not be used in the center tank. 

(2) The maximum allowable fuel temperature for JP-4 or Jet B fuel is 85°F. 

(3) When operating with JP-4 or Jet B fuels, the maximum allowable altitude for 

the first two hours of cruise operation shall be limited to: 

Dispatch Fuel Temperature (°F) 

65 to 85 

45 to 65 

25 to 45 

15 to 25 

4 

Altitude Limit (Feet) 

32,000 

36,000 

39,000 

41 ,000 
15 or Lower 42,000 

( 4) The fuel tanks must be defueled to sump level (i.e. level at which fuel pump 

low-pressure lights illuminate) following operations with JP-4 or Jet B fuel. If 

the fuel tanks are not delueled, the JP-4 fuel usage limitations shall continue to 

apply. 

It should be noted that there is an inherent margin of safety associated with limiting JP-4 

or Jet B fuel usage based on suction fuel feed capability. Under normal conditions, the 

airplane tuel boost pumps will be functioning. There are two alternating current (AC) 

powered boost pumps in each of the main fuel tanks, and two AC-powered boost pumps 

in the center tuel tank. The center tank boost pumps can adequately supply fuel to the 

engines with the main tank boost pumps inoperative. Under pressure feed conditions, the 

airplane can operate normally with .IP-4 fuel at a temperature of 110°F up to maximum 

altitude. Suction feed operation is required only when all AC power is lost on the 

airplane. The probability of this occurrence is extremely low due to redundancies 

incorporated in the airplane electrical system. 

Notice and Public Pt·ocedurc Provided 

On March 28,2002. the FAA published notice of the petition for exemption in the Federal 

Register and requested comments from the public. No comments have been received. 

FAA's Analysis of the Petition 

The regulation regarding fuel system performance with hot fuel is intended to ensure that 

an uninterrupted fuel supply is provided to the engines. Section 25.961 (a)(5) specifically 

requires that this capability be demonstrated with fuel at a temperature of at least 110 °F. 

The Boeing Model 757-200 series airplane with Pratt & Whitney PW2037 engines was 

shown by testing of components and tuel system analysis to directly comply with 

§ 25.961 (a)(5). As discussed by the applicant, an 85 °F fuel temperature limitation was 

imposed for Boeing Model 757-200 series airplanes equipped with Rolls-Royce engines 

following testing intended to show compliance with § 25.1351 (d). This testing showed 

that engine power interruption could not be induced at any altitude within the airplane 

performance envelope with J P-4 fuel at a temperature of 85° F. A similar, early test on 

the 757-200 airplane with Pratt & Whitney PW2037 engines demonstrated adequate 

performance ofthe fuel system with 104° F. JP-4 fuel and JP-4/Jet B use was therefore 

unrestri cted within the normal I I oo F limitation. 

Since the original finding of compliance with§ 25.961(a)(5) on the Boeing Model 

757-200 series airplane with Pratt & Whitney PW2037 engines, the FAA has determined 

that a more extensive tlight test of the airplane with hot fuel is necessary to show 

compliance with this section. Ana lysis and component testing alone are no longer 

accepted by the FAA as an adequate demonstration of compliance because of unexpected 

5 
fuel flow interruption to the engines during certification flight testing on an airplane 

utilizing these methods. 1-! owever, in this petition for exemption, the applicant has 

proposed operational limitations on dispatch fuel temperatures and altitude that ensure 

that satisfactory fuel system performance will be achieved. These limitations are 

consistent with flight test per1ormance previously demonstrated by the airplane and 

engines, and with the latest. more stringent, requirements. 

The petitioner has requested that the Boeing Model 757-300 derivative airplane equipped 

with Pratt & Whitney PW2000 series engines be granted an exemption from 

§ 25.961 (a)(5). The information provided by the petitioner indicates that granting of the 

exemption to allow usc or JP-4 and Jet B fuel would be in the public interest because it 

will allow use of alternate airports where these fuels are the only fuels available. Public 

safety would not be adversely a ffected because the temperature and fuel loading 

limitations placed on the airplane will limit operation of the airplane to fuel temperatures 

where satisfa ctory fuel system performance has been demonstrated. 

The Grant of Exemption 

In consideration of the roregoing, I 1ind that a grant of exemption is in the public interest and will 

not adversely afrect the level or safety provided by the regulations. Therefore, pursuant to the 

authority contained in 49 U.S.C. 40113 and 44701, delegated to me by the Administrator, the 

petition of the Boeing Company for an exemption from the fuel system hot weather operation 

requirements or§ 25.96 1 (a)(5) at Amendment 25-85, tor the fuel system of the Boeing Model 

757-300 series airplanes powered by Pratt & Whitney PW2000 series engines, is hereby granted, 

with the following limitations. 

The foll owing limitations are to be included in the airplane flight manual (AFM) for 

Model 757-300 se ries ai rpl anes powered with Pratt & Whitney PW2000 series engines: 

"Operational Limits: 

"(I) JP-4 or Jet B fuel shall not be used in the center tank . 

.. (2) The maximum all owable fuel temperature for JP-4 or Jet B fuel is 85 °F . 

.. (3) When ope rating with JP-4 or Jet B fuels, the maximum allowable altitude for 

the first two hours of cruise operation shall be limited to: 

Dispatch Fuel Temperature (°F) 

65 to 85 

45 to 65 

25 to 45 

15 to 25 

15 or Lower 

6 

Altitude Limit (Feet) 

32,000 

36,000 

39,000 

41 ,000 

42,000 
"(4) The fuel tanks must be defueled to sump level (i.e. level at which fuel pump 

low-pressure lights illuminate) following operations with JP-4 or Jet B fuel. If the 

fuel tanks are not defueled, the JP-4 fuel usage limitations shall continue to apply." 

Issued in Renton, Washington, on June 3, 2002. 

Is/Ali Bahrami 

Ali Bahrami 

Acting Manager 

Transport Airplane Directorate 

Aircraft Certification Service 

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