FAA Orders Boeing Fan Cowl Swaps to Stop Mid-Air Mishaps
Published Date: 3/4/2025
Rule
Summary
The FAA is making new safety rules for Boeing 737 airplanes to fix problems caused by engine fan parts falling off. Owners must replace certain fasteners, modify parts, or swap in safer fan cowls by April 8, 2025, and update their maintenance plans. These changes keep flights safer and might cost some money but prevent serious emergencies.
Analyzed Economic Effects
4 provisions identified: 1 benefits, 3 costs, 0 mixed.
Airlines must retrofit Boeing 737 fan cowls
If you operate Boeing 737-600/-700/-700C/-800/-900/-900ER airplanes, you must replace certain fasteners, modify the radial restraint assembly, and install an external doubler at the starter vent (or install a serviceable fan cowl) as required by Boeing Special Attention Requirements Bulletin 737-71-1937 RB, Revision 1. The AD is effective April 8, 2025, and the FAA estimates it affects 1,979 U.S.-registered airplanes; the FAA estimates the modification and installation cost per airplane at $13,300 (140 work-hours x $85/hour = $11,900 labor plus $1,400 parts) and the serviceable fan cowl option could cost up to $16,280 per airplane.
Passengers benefit from fewer fan-cowl failures
You as a passenger are better protected because the rule addresses engine fan blade-out events that previously caused fan cowl and inlet cowl parts to separate and in one case caused fuselage damage, loss of pressurization, and an emergency descent. The AD requires hardware changes and maintenance-program updates to prevent fan cowls from departing the nacelle and striking the fuselage or stabilizer.
Operators must update maintenance programs
If you operate affected Boeing 737s, you must revise your maintenance or inspection program to include new Airworthiness Limitations (AWLs). The FAA estimates revising a maintenance program takes 90 work-hours at $85/hour, for an average cost of $7,650 per operator.
Compliance deadlines and operation limits
This AD is effective April 8, 2025, and requires incorporation of the AWLs before further flight as part of the modifications. The FAA specified that operators have until December 31, 2029 to incorporate solutions addressing potential engine nacelle maintenance errors (AWL No.4), and figure 1 states certain fan-cowl and inlet modifications must be installed so aircraft cannot operate past July 31, 2028 unless upgraded to compliant hardware.
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