### BEFORE THE FEDERAL AVIATION ADMINISTRATION

WASHINGTON D.C.

Petition of: DELTA AIR LINES, INC. OPERATING CERTIFICATE DALA026A Docket FAA- 2015- 

### For exemption of certain requirements of 14 C.F.R. §121.629(b)

PETITION OF DELTA A.IR LINES, INC. FOR AN EXEMPTION June 15, 2015
Delta Air Lines, Incorporated, operating certificate DALA026A, hereby petitions the Federal Aviation Administration (FAA), pursuant to 14 C.F.R. Part 11 for relief from Federal Aviation Regulation (FAR) §121.629(b), provided certain conditions and limitations are met.

Sec , d¢a?v ofr itlhca FrllR Afffec$e¢a7 Section § 121.629 Operation in icing conditions. (b) No person may take off an aircraft when frost, ice, or snow is adhering to the wings, control surfaces, propellers, engine inlets, or other critica ➢ surfaces of the aircraft or when the takeoff would not be in compliance with paragraph (c) of this section. Takeoffs with frost under the wing in the area of the fuel tanks may be authorized by the Administrator. Specifically, Delta requests an Exemption for the Boeing B737-700, -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.
Backg r® aa n ¢9 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 iaminar airflow on

- the wing causing loss of iift 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 particufar set of conditions that may include near- or sub-freezing temperatures in combinat+,on with precipitation and/or high humidity (especially fog).Petition for Exemption - (FAR) §121.629(b)

Delta Air Lines, Inc. June 15, 2015 Page 2
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 inay exist with negligible impairment of performance. Boeing has conducted thorough aerodynamic analysis of the conditions under which operation with CSFF is and is not permitted and has issued a new limitation in the AFM that sets forth conditions under which takeoff is not permitted with CSFF (attachment 1), stating: Takeoff with cold soaked fuel frost on the wing tank upper surfaces is not permitted if any of the following conditions are present:
1. The ambient air temperature is below +4°C, +39°F. 2. The tank fuel temperature is below -16°C, +3°F. 3. There is cold soaked fuel frost on the wing tank upper surfaces that is beyond the lines defining the permissible cold soaked fuel frost area. 4. There is precipitation or visible moisture (rain, snow, drizzle, or fog with less than 1 mile visibility). Any of these conditions would therefore preclude takeoff in accordance with 14 CFR §121.629(b). However, if the above-listed limiting conditions are not present, 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 cYuise. 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.Petition for Exemption - (FAR) §121.629(b)

Delta Air Lines, Inc. June 15, 2015 Page 3

Extent ®f Relief and Reas®n Delta seeks 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 inc!ude: 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.
Requesg f®a- expeclited c®nsadea
- aUan DAL is also requesting that, as part of this Petition for Exemption request, the public comment phase be waived as per Title 14 CFR Part 11.87(a), which states: "The FAA may not publish a summary of your petition for exemption and request comments if you present or we find good cause v ✓ hy we should not deiay action on your petition. The factors we consider in deciding not to request comment include: (a) Vb'hether granting your petition would set a precedent... It is the opinion of DAL that since the mitigating actions are already in place and the operation requested has been demonstrated by Boeing and approved by the FAA in the AFM, there is no precedent being set with our request. The purpose of this exemption is to continue operating the B737fVG aircraft in safe and compliant operations under the restrictions and limitations provided by the AFM.

PubVac Benefit This exemption, if granted, provides a safe operation while allowing greater flexibility, thereby providing the traveling public an equivalent leve9 of safety. Having the flexibility to operate while adhering to the restrictions specified in the Boeing B737 AFM is in the best interest of the traveling public for reliability of the operation.Petition for Exemption - (FAR) §121.629(b)

Delta Air Lines, Inc. June 15, 2015 Page 4



### No Adverse Affect on 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 operatior 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 appiication 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 Xt'ring. 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.


### Summargf for Federal Reguster
Petitioner: Delta Air Lines, Inc. Affected Regulations: 14 CFR 121.629(b) Summary of Relief Sought: Delta requests an Exemption for the Boeing B737-700, -800 and -900/-900ER "Next Generation" (B737NG) series aircraft from the requirement that "No person may take ofP 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. Granting this Exemption is in the public interest as it maintains an equivalent level of safety, because Boeing has conducted aerodynamic analyses that conservativeiy conclude the conditions under which safe operation is permissible.Petition for Exemption - (FAR) §121.629(b)

Delta Air Lines, Tnc. June 15, 2015 Page 5

Conclusiora 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. Please contact Charles M. Schramek, General Manager Quality Assurance and Compliance, at (404) 715-1112 or e-mail at 

### chuck.schramek(

~ 

### )delta.com , if you have and questions or need additional information.
Sincere€y,

St en M. Dicks n Senior Vice President Flight Operations 

### Delta Air Lines, Inc.
cc: David Gerken, Acting Office Manager, Delta Certificate Office - FAA James T. Giies, Jr, Principal Operations Inspector, Delta CMU - FAA