FAA grants limited turbocharger clamp AD extension

The AMOC allows continued use of some, though certainly not all, of the v-band couplings installed on airplanes, helicopters, and engines subject to the 2023 airworthiness directive that consolidated a number of previous directives, casting a wide net in an effort to prevent exhaust separation and fire in flight caused by failure of a part common to many makes and models: the spot-welded, multi-segment v-band coupling.

This safety-critical part installed on most turbocharged piston engines began to fail in the mid-1970s, causing "a significant number of incidents and accidents (fatal and non-fatal) on both airplanes and helicopters," the FAA noted in the 2023 AD. The directive was preceded by 20 previous ADs for specific makes and models, 10 special airworthiness information bulletins, and seven NTSB recommendations—all related to v-band coupling failures.

Consolidating dozens of aircraft and engine makes and models into a single directive to replace v-band couplings that have exceeded 500 hours in service, the FAA allowed operators two years to keep couplings in service up to 500 hours with mandatory inspections to be conducted every six months or 100 hours, whichever comes first. The AD set a deadline of July 17 (two years following the effective date of the 2023 AD) to cease installation of v-band couplings with any service time at all, "unless it has passed all inspections required."

The Continental AMOC approved July 16 extends the potential service life of the v-band coupling (part number 653332) installed on 11 of the 35 Continental engine models that are subject to the 2023 AD. The 500-hour limit increases to 1,400 hours on some engines, up to as much as 2,000 hours for others in the group of 11 engines, though it expires in nine months, on April 15. The six-month or 100-hour interval requirement remains in place for all spot-welded v-band couplings. Extending the service life of some Continental couplings may ease the supply constraint that could otherwise begin grounding aircraft if owners are unable to obtain new v-band couplings after July 17. Any v-band couplings of unknown time in service must be replaced, according to both the AD and the Continental AMOC.

Of the estimated 41,058 aircraft and engines subject to the AD, "many are Continentals," said AOPA Vice President of Regulatory Affairs Murray Huling, who reached out to the FAA to ask whether any other AMOCs for other makes and models subject to the AD have been submitted for FAA approval.

"Unfortunately, it sounds like none are in work at this time," Huling said. “Also, it is imperative that companies develop new v-band clamps which will negate the need for an AD and AMOC altogether.”

Requiring replacement of spot-welded v-band couplings at 500 hours with brand-new parts creates a surge in demand that manufacturers may not be able to keep up with, a constraint the FAA acknowledged in the 2023 AD, which granted owners two years to keep couplings with higher service times installed, subject to recurring inspection. With that time now expired, replacement of a part that the FAA estimates will cost $400, plus labor, on the next inspection interval is mandatory.

AOPA challenged the FAA's compliance cost estimate when the AD was first proposed, noting that the $85 hourly labor rate is much lower than many members report. The FAA estimates two work hours per engine will be needed to remove and replace the coupling with a new part.