The FAA is proposing two airworthiness directives affecting Pilatus PC–12s and has issued another for the Pilatus PC–6.
Both proposed ADs for the PC–12 stem from ADs issued by the European Union Aviation Safety Agency.
One AD would affect Pilatus models PC–12, PC–12/45, PC–12/47, and PC–12/47E turboprops. The action would correct an unsafe condition created by “improperly manufactured horizontal stabilizer rear attachment bolts.” The problem could “lead to fatigue failure of the bolts and loss of airplane control,” the proposal states.
Pilatus had issued a service bulletin (No. 55-004) in March 2019 to provide instruction on inspecting and replacing the bolts.
The proposed AD would affect 14 aircraft of U.S. registry and cost an estimated $5,127.50 per aircraft to comply. The FAA is accepting comments until September 21. To submit comments online or to send them by mail or fax, see the AD.
The second proposed AD, also based on an AD issued by EASA, would affect only Pilatus PC–12/47E aircraft, and seeks to correct “seizing of a main landing gear spring pack assembly.” The problem could prevent the main landing gear from safely extending and lead to loss of control after landing.
According to the proposed AD, “An occurrence was reported of an unlocked main landing gear (MLG) during landing of a PC–12/47E, equipped with electro-mechanical landing gear. Subsequent investigation identified that the aeroplane was equipped with an affected part [spring pack assemblies having part number (P/N) 5188.8.131.52], which had completely seized. Serviceable parts [spring pack assemblies having P/N 5184.108.40.206] have a special surface treatment on the inner and outer tube, which would have prevented the seizure.”
Pilatus had issued a service bulletin (No. 32-027) for this issue in January 2019. The service bulletin details the procedures for inspecting the main landing gear spring pack assembly to find the part number, removing and discarding affected assemblies, and installing “the improved design spring pack assemblies.”
It would cost about $5,255 per aircraft to comply; 29 affected aircraft are listed in the U.S. registry.
The FAA is accepting comments through September 21.
Several Pilatus PC–6 models are affected by annother AD that the FAA has issued, effective September 9, to address “rudder shaft assemblies with incorrect rivet configurations.” The AD affects the PC–6, PC–6/350, PC–6/350–H1, PC–6/350–H2, PC–6/A, PC–6/A–H1, PC–6/A–H2, PC–6/B–H2, PC–6/B1–H2, PC–6/B2–H2, PC–6/B2–H4, PC–6/C–H2, PC–6/C1–H2, PC–6–H1, and PC–6–H2.
The AD is also based on airworthiness action that EASA took in October 2018.
EASA issued the AD because a “pilot experienced loss of rudder control” during a check flight and made a precautionary landing followed by a runway excursion. According to the AD, “The post-event inspection of the affected rudder shaft assembly found an incorrect rivet configuration. Subsequent investigation results identified that the tapered pins had been replaced with an insufficient quantity of rivets of unknown origin, which effectively constituted a modification that does not conform to any of the three different Pilatus-approved configurations. Prompted by this event, five more aeroplanes were inspected and various non-standard rivet configurations were found in the same area. It cannot be excluded that more PC–6 aeroplanes have had a similar modification applied.”
Pilatus released a service bulletin (No. 27-006, Rev. No. 1) in September 2018 for inspecting the rudder shaft assembly and rivets. Repairs should cost about $595 per aircraft; 30 aircraft in the U.S. registry are impacted.
Even though the AD goes into effect September 9, the FAA is still accepting comments.