Enclosure 

RA-15-00662 

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Petition for Exemption from Title 14 CFR 25.961(a)(5) Amendment [25-57], Fuel System Hot 

Weather Operation 

Name and Address of the Petitioner

Douglas M. Lane, Director 

The Boeing Company 

PO Box 3707 

Seattle, Washington, 98124 

Section(s) of the Regulations from which Relief is sought:

§25.961(a)(5) Fuel System Hot Weather Operation: 

"(a) The fuel system must perform satisfactorily in hot weather operation. This must be shown 

by showing that the fuel system from the tank outlets to each engine is pressurized, under all 

intended operations, so as to prevent vapor formation, or must be shown by climbing from the 

altitude of the airport elected by the applicant to the maximum altitude established as an 

operating limitation under Sec. 25.1527. If a climb test is elected, there may be no evidence of 

vapor lock or other malfunctioning during the climb test conducted under the following 

conditions: 

(5) The fuel temperature must be at least 110° F." 

Extent of Relief and Reason

Boeing is requesting relief from the requirements of 14 CFR 25.961(a)(5), Amendment [25-57], 

for the Pratt & Whitney-powered 767-2C. The regulation requires that the airplane and engines 

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

that the FAA approve a set of limitations for JP-4** and Jet B fuels on the Pratt & Whitneypowered 767-2C in lieu of compliance to the specified temperature of 110°F. The limitations 

consist of restricting the maximum fuel temperature to 85°F, restricting the cruise altitude vs. fuel 

temperature, and making use of fuel tank temperature indication to allow JP-4 usage in any tank 

including the center and body tanks. Similar limitations were approved for the Rolls Roycepowered 757-300 and 747-400/-400F. This exemption from the 110°F requirement is required 

because the properties of JP-4 will not support operation at that temperature under all intended 

operations. 

Boeing submits this petition for the following reasons: 

(1) It is in public interest. The customer for the 767-2C requires their aircraft be able to operate 

with JP-4 and Jet B fuels. A maximum temperature of 85°F will meet their operational 

requirements. 

(2) The 767-2C will demonstrate fuel feed performance under normal and abnormal conditions 

with JP-4 at the maximum temperature allowed under this exemption. 

(3) The 767-2C will demonstrate fuel feed performance under normal and abnormal conditions 

to cover all other approved fuels to temperatures in excess of 110°F. 

(4) The 767-2C will be certified with an inerting system in all tanks that will limit flammability 

below the levels required by 14 CFR 25.981(b). 
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(5) The proposed limitations on fuel temperature and maximum altitude for cruise provide 

a level of safety equal to that intended by 14 CFR 25.961(a)(5). 

(6) The FAA has granted similar exemptions in the past: 

(a) for the Rolls Royce-powered 757-300 (FAA Exemption No. 6867, issued 

2/12/1999) 

(b) for the Pratt & Whitney-powered 757-300 (FAA Exemption No. 7790, issued 

6/3/2002) 

(c) for the Rolls Royce-powered 747-400/400F (FAA Exemption No. 7496, issued 

4/12/2001) 

(d) the Rolls Royce-powered 757-200 has had an 85°F temperature limitation for JP-4 

and Jet B fuels since entry into service in 1983. 

**JP-4 is a military designation for a Jet B type commercial grade fuel with additives. 

Description of Issue

Boeing is introducing a 767-2C airplane model powered by Pratt & Whitney PW4062 engines. 

The 767 with Pratt & Whitney PW4000 series engines was introduced in 1986, and has 

accumulated over 15.1 million flight hours of revenue service. The 767-2C will offer only the 

PW4062 engine at this time. The customer has requested the aircraft be certified to operate with 

JP-4 fuel in all tanks. The 767 with PW4000 series engines is currently certified to operate with 

JP-4 fuel, as listed on the Type Certificate Data Sheet, however, there is an Airplane Flight 

Manual limitation that does not allow it for revenue flights. 

With regard to 14 CFR 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 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 main tanks to maintain engine operation. This 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 14 CFR 25.961(a)(5) addresses this condition, among 

others, and is intended to insure that airplane operation will not be adversely impacted by fuel 

temperature. Boeing seeks to establish appropriate temperature and altitude limitations to ensure 

the intent of the regulation is met. 

Statement of Public Interest

It is in the public interest that the 767-2C be able to operate with JP-4 and Jet B fuels. These 

fuels are used in some parts of the world, particularly in cold weather areas due to their low 

freezing point. Occasionally they are the only fuels available at military or diversion airfields. 

Use of JP-4 and Jet B fuels in all tanks will allow the 767-2C greater utilization and flexibility. 
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The 767-2C will provide industry-leading operating economics and environmental 

improvements. The 767-2C will be replacing older aircraft with poorer fuel economy and 

higher maintenance costs. Granting this petition will reduce operational costs by reducing the 

amount of fuel consumed and reducing aircraft maintenance costs. The reduction in fuel 

consumed will also result in reduced engine emissions into the atmosphere. These benefits will 

accrue with no decrease in safety. 

Statement of No Adverse Effect on Safety

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 the 

following: 

(1) Suction feed performance flight testing with JP-4 at the maximum allowed temperature 

will be demonstrated for certification. 

(2) The following proposed altitude restrictions are based on fuel temperature and will be 

incorporated to keep fuel pressure and V/L (vapor/liquid) ratio within the engine 

manufacturer’s limitations at the engine pump inlet. 

Fuel Tank Temperature (°F) Altitude Limit (feet)

65 to 85 32,000 

45 to 65 36,000 

25 to 45 39,000 

25 or lower 40,100 

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

(4) The maximum fuel temperature of the left main tank, center wing tank, forward body 

tank, and aft middle body tank is indicated in the flight deck which allows the Flight Crew to 

operate within the limitation including when the center or body tanks contain JP-4 or Jet B 

fuel. 

(5) The AFM (Airplane Flight Manual) will include ground dispatch guidelines that will 

enable the operator to comply with the temperature limitation requested in this exemption. 

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 fuel boost 

pumps will be functioning. There are two AC powered boost pumps in each of the main fuel 

tanks, and two AC powered override pumps in the center fuel tank. Under pressure feed 

conditions, the airplane can operate normally with JP-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 
Enclosure 

RA-15-00662 

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

the airplane electrical system. 

Request to ‘Waive Publication and Comment’

Not requested. 

Privileges of the Exemption Outside the United States

Not requested. 

Summary to be Published in the Federal Register

Boeing is requesting relief from the requirements of 14 CFR 25.961(a)(5), Amendment 57, 

for JP-4 and Jet B fuel usage on 767-2C program. The regulation requires that the airplane 

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

Boeing requests that the FAA approve limitations for JP-4 and Jet B fuels on 767-2C in lieu 

of compliance to the specified temperature of 110°F. The limitations would consist of 

restricting the fuel temperature to 85°F, and altitude restrictions. The altitude restrictions 

will be based on fuel temperature to keep fuel pressure and V/L (vapor/liquid) ratio within 

the engine manufacturer’s limitations at the engine pump inlet. 

Similar exemptions have been approved on 757-300 and 747-400/-400F model airplanes. 

Boeing asserts that an exemption to 14 CFR 25.961(a)(5) subject to the limitations presented 

herein is in the public interest and maintains a level of safety equal to that intended by the 

regulation.