Metroliner and Merlin pitch-trim AD: inspections start by year-end

The FAA is ordering recurring checks of the pitch trim actuator on 198 U.S.-registered Metroliner and Merlin aircraft after reports of in-flight failures. The agency says moisture getting into the actuator could lead to reduced control of the airplane, and the first inspections are due by year-end.If your SA226 or SA227 carries a Simmonds-Precision pitch trim actuator, part number DL5040M5, DL5040M6 or DL5040M8, the AD covers you. For most operators, the first deadline falls on Dec. 31. Each of the two required checks costs an estimated $255, but an actuator that fails the travel-time test must be replaced before the aircraft flies again, at an estimated cost of $20,425. The FAA cannot estimate how many actuators will fail, and the rule does not address replacement-part availability.The part at issue is the pitch trim actuator, which the FAA files under the elevator tab control system. According to the FAA, moisture can get into the actuator body through the rod-end keyway and the actuator piston. The April proposal cited six reports of in-flight failures due to corrosion, which it said trace to the piston rod being "drilled through," which lets moisture in.The AD requires two recurring checks: an inspection of the actuator's rod-end sealant and a measurement of its travel time. Any compromised sealant must be addressed according to the rule's procedures. An actuator that misses the travel-time criteria must be replaced before the next flight, and the AD bars special flight permits. Check First due Repeats FAA estimate Rod-end sealant inspection Dec. 31, or the actuator's first six months or 1,000 flight hours in service if that comes later Every 1,000 flight hours or 12 months, whichever is first $255 Travel-time measurement Same as above Every 250 flight hours or six months, or 300 for some actuator versions $255 Replacement after a failed check Before further flight Not applicable $20,425, of which $20,000 is the part The longer 300-hour interval applies to DL5040M6 and M8 actuators and to replacement DL5040M5 units in which both nut tube assemblies were replaced with new ones. The FAA estimates three labor hours per check at $85 an hour, with no parts. If the sealant turns out to be compromised, the actuator's age decides the fix. One that has reached six months or 1,000 flight hours in service comes out before the next flight, while a younger one gets resealed for an estimated $319.Some operators may already be ahead. The earliest Ontic service bulletin the AD references is dated July 2024, and the AD credits a sealant inspection done before Dec. 1 under the earlier versions. On airplanes with the original DL5040M5, the measurement interval stays at the 250 hours or six months, matching AD 2007-16-03, which the FAA said operators should already be following.The rule doesn't require a repair station. One commenter argued the inspection can't be done in the field and asked for that requirement, and the FAA declined. It said the service bulletins give a mechanic what's needed and that the owner or operator must make sure a qualified and licensed mechanic does the work.Why it mattersWhat an owner can't price is where the failure happens. An actuator that misses the travel-time test, or shows compromised sealant after six months or 1,000 flight hours in service, stops the airplane wherever it happens to be, and with no ferry permit allowed, the repair has to come to it. Nobody controls which side of that line an actuator lands on, but an owner does control where the airplane sits when the check comes due, and whether a shop and a part are lined up there. The FAA sets the date, and the owner gets to choose the place.Browse current twin-engine turboprops on GlobalAir.com.