FAA Grants Allegiant Air Exemption For Boeing 737 MAX Frost On Wings Operations

The Federal Aviation Administration ( FAA) has granted Allegiant Air an exception to take off with its Boeing 737 MAX 8-200 aircraft with ice adhering to a particular zone of the wing at the discretion of the captain flying the single-aisle jet.

Affecting a certain wing zone

In a filing on November 5, which was made public on the following day, the FAA said that it approved Allegiant Air’s request to take off with its 737 MAX 8-200 aircraft when frost, ice, or snow is adhering to the wings in a safe zone, within which cold soaked fuel frost (CSFF) is allowed.

The original equipment manufacturer (OEM), namely Boeing, made that determination, the FAA added.

“[…] the FAA considered Boeing’s aerodynamic analysis, as well as FAA-approved procedures contained in the petitioner’s manuals and included in its training program, and found that Boeing’s aircraft flight manual (AFM) definition of a safe zone where CSFF can be permitted on upper wing surfaces of certain Boeing 737 aircraft, at the discretion of the pilot-in-command, provides a level of safety equivalent to the requirements of Section 121.629(b).”

Section 121.629(b) prohibits takeoffs when frost, ice, or snow is adhering to the aircraft’s wings, control surfaces, propellers, engine inlets, or other critical surfaces when the takeoff does not comply with deicing/anti-icing requirements. However, the section noted that the regulator could approve takeoffs with frost under the wing in the area of the fuel tanks. Allegiant Air will have to adhere to certain conditions and limitations.

The airline took delivery of its first 737 MAX 8-200 aircraft on September 9, with the single-aisle jet entering commercial service on October 20.

No takeoffs when the ambient temperature is lower than 4°C

The FAA pointed out that the exemption only applied to Allegiant Air’s 737 MAX 8-200 aircraft, with the airline having to adhere to the revised Boeing AFM’s miscellaneous limitations for CSFF in all instances concerning fuel in such conditions.

“This exemption does not relieve Allegiant from any other limitations or requirements with regards to deicing and anti-icing operations.”

Furthermore, a takeoff with CSFF on the wing tank upper surfaces is prohibited if the ambient air temperature is lower than 4°C (39°F), the tank fuel temperature is -16°C (3°F), there is CSFF on the wing tank upper surfaces beyond the lines defining the permissible CFSFF area, and there is precipitation or visible moisture, namely rain, snow, drizzle, or fog with less than 1 mile (1.6 kilometers) of visibility.

Mandatory training

The regulator has approved the carrier’s CSFF pilot training program. However, Allegiant Air pilots must undergo training before applying the exemption’s standards, the FAA said.

“Allegiant must provide ground and operational training to all pilots and ground personnel to ensure each is able to clearly discern the applicability of the CSFF exemption requirements, to include identifying which Allegiant aircraft have the painted CSFF upper wing areas. The training must include recognition of those airplanes approved for CSFF exemption.”

In addition, the FAA concluded that a pilot-in-command (PIC) retains final authority over whether an aircraft can take off with CSFF.

The regulator retains the right to suspend the exemption if Allegiant Air fails to comply with the conditions and limitations. The exemption is set to expire on November 30, 2026, unless superseded or rescinded.

When Allegiant Air applied for the exemption, it said that while frost may form in the limited area due to cold fuel, the outside conditions would not otherwise be conducive to icing, and Boeing’s limitation would not prevent the aircraft from taking off.

“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.”

Allegiant Air cited the FAA’s approval of Boeing’s “conservative determination through aerodynamic analysis of the conditions under which operation with CSFF is and is not permitted,” application of painted lines in areas where CSFF is accepted, and AFM limitations.

The latter assured that operations are only allowed in certain instances of CSFF. Otherwise, flights are not allowed to depart in icing conditions without deicing.