March 3, 2015

U.S. Department of Transportation

Docket Operations

West Building Ground Floor, Room W12-140

1200 New Jersey Avenue, SE

Washington, DC 20590

Subject: Petition for Exemption

Reference: 14 CFR §121.629(b) – Operation in Icing Conditions

Dear Sir or Madam:

In accordance with the provisions of Title 14, Code of Federal Regulations (14 CFR) §11.63 and 

§11.81, Airlines for America, on behalf of our passenger and cargo airline members and similarlysituated air carriers1

, petitions for a limited Exemption from 14 CFR §121.629(b). Specifically, A4A 

requests an Exemption on the Boeing B737-600, -700, -800 and -900/-900ER “Next Generation”

(B737NG) series aircraft from the requirement that “No person may take off an aircraft when frost, 

ice, or snow is adhering to the wings” where the Original Equipment Manufacturer (OEM) has 

determined a “safe” zone within which cold soaked fuel frost (CSFF) is permissible, has visibly 

marked the zone on the wing, and has placed an appropriate limitation in the Airplane Flight 

Manual (AFM) that the Federal Aviation Administration has approved. 

Background 

Airframe icing in general has long been known to be a hazard to safe operation of aircraft, 

especially on the wing. Wing surface texture changes can disrupt laminar airflow on the wing 

causing loss of lift and reduced stall speed, adversely affecting aircraft performance. Further, the 

weight of accumulated ice may present a weight and balance issue unknown to the crew and that 

cannot be accurately estimated from visual observation. Ice on the wing may form in a particular 

set of conditions that may include near- or sub-freezing temperatures in combination with 

precipitation and/or high humidity (especially fog). Additionally, frost may form on a cold wing, 

particularly in areas with underlying cold soaked fuel as in the case of an airplane recently 

exposed to high altitude cruise conditions that has landed in a humid climate, a condition known 

as CSFF.

Boeing has applied painted lines defining an area on the upper surface of the wings on certain 

B737NG aircraft where, with certain other limitations, CSFF may exist with negligible impairment 

of performance. Boeing has issued a new limitation in the AFM that sets forth conditions under 

which takeoff is not permitted with CSFF (attachment 1), stating that CSFF outside the painted

limit lines, extremely cold fuel, or the presence of other common airframe icing conditions

preclude takeoff in accordance with 14 CFR §121.629(b). However, if the above-listed limiting

 

1 A4A airline members affected by the issue are: Alaska Airlines, Inc.; American Airlines, Inc.; Delta Air Lines, Inc.; Southwest 

Airlines Co.; and United Air Lines, Inc.
March 3, 2015, A4A Petition for Exemption

conditions are not met, i.e. CSFF is present within the limit lines and other specified adverse 

conditions do not exist, operation should be permissible. An example of such permissible 

operation would be an airplane that has arrived in a moderate temperature, humid climate after

long-range high altitude cruise. Frost may form in the limited area due to cold fuel, but the outside 

conditions are not otherwise conducive to icing and Boeing’s limitation would not preclude takeoff. 

Regulation 14 CFR 121.629 does not allow for any exception, including the OEM’s safety 

determination set forth in the Airplane Flight Manual, an FAA approved document. By approving 

the AFM, FAA provides the basis upon which operation with CSFF can be permitted if this petition 

is granted. 

The Applicable Regulations and Relief Sought

We seek an exemption from 14 CFR §121.629(b) to permit operation with CSFF within a defined 

area of the wing’s upper surface The exemption would be limited by Boeing’s Airplane Flight 

Manual – Miscellaneous Limitations notation that defines conditions under which takeoff with 

CSFF is not permitted.

Reasons for seeking the relief at this time include: 

1) FAA has approved Boeing’s conservative determination through aerodynamic analysis of the 

conditions under which operation with CSFF is and is not permitted.

2) Boeing’s application of painted lines on the wing, which FAA also approved, define the areas 

of acceptable CSFF.

3) The AFM limitation assures that operations are only permitted in certain instances of cold 

soaked fuel, operations are not authorized (without deicing) when airframe icing conditions 

otherwise exist.

Granting the Exemption Would Not Adversely Affect Safety

Safety will not be adversely impacted if the FAA grants this petition because FAA has concluded 

by approving the AFM that the conditions under which operation with CSFF present is permitted 

on B737NG by the AFM are sufficiently conservative and tested by Boeing to be safe for takeoff. 

The requirements contained in this AFM limitation prevent application on aircraft that are not 

eligible. A visual inspection of the upper wing surface is required to ensure that CSFF is not 

beyond the lines defining the boundaries of the cold soaked fuel frost area. To apply the revised 

B737NG AFM limitation for Cold Soaked Fuel Frost, the B737-NG must have the “permissible” 

lines defining the boundaries of the CSFF area on the upper wing. The B737NG AFM limitation 

for CSFF cannot be applied to a 737 Classic (100-500) series aircraft or B737NG aircraft that has 

not been delivered or later modified with the CSFF boundary lines. 
March 3, 2015, A4A Petition for Exemption

A Summary of this Petition that FAA Could Publish in the Federal Register

Petitioner: Airlines for America

Affected Regulations: 14 CFR 121.629(b)

Summary of Relief Sought: FAA is requested to provide relief from the cited rule when the OEM, 

Boeing allows operation of B737-600, -700, -800, and -900/-900ER

“NG” aircraft with Cold Soaked Fuel Frost present in defined areas 

of the wing upper surface and states conditions in the FAA-approved 

Airplane Flight Manual when operations are not permitted.

Granting this Exemption is in the public interest as it maintains an equivalent level of safety, 

because Boeing has conducted aerodynamic analyses that conservatively conclude the 

conditions under which safe operation is permissible.

Conclusion

For the foregoing reasons, we respectfully request an Exemption from the requirements of 14 

CFR §121.629(b) for CSFF limited by Boeing’s AFM conditions.

Sincerely,

Robert Ireland

Managing Director

Engineering and Maintenance
March 3, 2015, A4A Petition for Exemption

ATTACHMENT 1 – Excerpt from Boeing B737NG Airplane Flight Manual