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FAA Expands CF34 Fuel System Checks

The new airworthiness directive orders a series of new inspections on the engines.

Operators of the GE CF34-8C-powered fleet, made up of larger Bombardier CRJs, face expanded inspections of engine fuel control system components following the FAA’s mandate of GE recommendations that target reducing in-service fire risk. The agency indicated that it will consider mandating checks for -8E models that power Embraer 170-series aircraft as well.

The new airworthiness directive (AD), published Nov. 18, orders inspections of -8C operability bleed valve (OBV) fuel tubes, bleed air manifold link rod assemblies, and fuel fittings, and replacement of parts that do not pass the checks. It supersedes an existing AD, adding revised procedures as well as -8C5A2s and -A3s, which power CRJ1000s.

The directives were prompted by several in-service engine fires, including a July 2017 incident on a SkyWest Airlines CRJ700 during an arrival at Denver International Airport. "Fire was observed at the left engine inlet, left engine aft pylon, and on the ground below the left nacelle, and an emergency evacuation was initiated on the taxiway,” the NTSB said in an incident brief. None of the 59 people onboard were injured.

The board has not finished its work, but reported that the fire started “after the OBV fuel supply line fitting pulled out of its housing.” That incident prompted the initial AD, issued in Nov. 2017.

GE used results from early inspections to refine its recommendations. It also introduced a new OBV part number, ending in P05, in Dec. 2018. GE told the FAA that its analysis determined that the P05 OBVs are less susceptible to the wear identified as creating the fire risk, so long as operators follow the OEM’s maintenance program. GE’s latest service recommendations, issued in May, call for a deadline of 16,000 hours for initial inspections and 1,680 hours for repeat checks, and it asked the FAA to revised its proposed directive to reflect the newest parts’ durability. 

The FAA rejected GE’s request, saying in the AD’s preamble that it "did not find GE’s test and analysis data sufficient to justify the extended inspection intervals."

The directive specifies initial inspections within 880 flight hours since the previous inspection, 500 flight hours from the AD’s Dec. 22 effective date, or 6,880 flight hours since new—whichever is later--for all -8C1, -8C5, -8C5A1s, and certain -8C5B1 serial numbers. The engines power Bombardier CRJ-700s, 900s, and 1000s.

Any -8C5B1s, which power CRJ-700 NextGens, and the -8C5A2s with more than 6,000 hours have initial inspection deadlines of 880 hours from the AD’s effective date. Engines below 6,000 hours must be checked within 880 flight hours or at 6,880 total hours.

The FAA directive would apply to 1,300 engines on U.S.-registered aircraft. Aviation Week’s Commercial Aviation Fleet Database shows about 1,600 -8Cs in service worldwide.

The NTSB, providing input during the AD’s comment period, urged the FAA to extend the OBV checks to -8E engines, which power E-170s/175s. The agency said it "agrees to consider future rulemaking” for the -8Es "because those engines have experienced the same unsafe condition addressed by the engine models of this AD.”

GE in September issued a service bulletin for the -8E OBVs with the same inspection intervals as its -8Cs bulletin. GE’s -8E recommendations do not include inspections for any P05-equipped engines, however.

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