June
2, 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, United Airlines 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

li nes 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, extreme

l y cold fuel, or the presence

of other common airframe icing conditions preclude takeoff

in accordance with 14 CFR

§ 1 21.629(b). However,

if the above-listed limiting

# 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

(1 00-500) series aircraft
or B737NG aircraft that has not been delivered

or later modified with the CSFF boundary lines.ASummaryofthisPetitionthatFAACouldPublishintheFederalRegisterPetitioner:AffectedRegulations:SummaryofReliefSought:UnitedAirlines14CFR121.629(b)FAAisrequestedtoproviderelieffromthecitedrulewhentheOEM,BoeingallowsoperationofB737-600,-700,-800,and-900/-900ER"NG"aircraftwithColdSoakedFuelFrostpresentindefinedareasofthewinguppersurfaceandstatesconditionsintheFAA-approvedAirplaneFlightManualwhenoperationsarenotpermitted.GrantingthisExemptionisinthepublicinterestasitmaintainsanequivalentlevelofsafety,becauseBoeinghasconductedaerodynamicanalysesthatconservativelyconcludetheconditionsunderwhichsafeoperationispermissible.ConclusionFortheforegoingreasons,werespectfullyrequestanExemptionfromtherequirementsof14CFR§121.629(b)forCSFFlimitedbyBoeing'sAFMconditions.StevenBastasManager-WinterOperationsUnitedAirlines-233SouthWackerDriveWHQAO-17thFloorIChicago,IL606060872-825-1209IM224-735-6029steve.bastas@united.com