Transport Canada, FAA Issue Emergency ADs After Bell 212 Crash

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Transport Canada and the FAA have issued emergency airworthiness directives (ADs) grounding some Bell 212, 204B, 205A-1 and 205B helicopters pending replacement of certain outboard main rotor hub strap pins. The ADs stem from an investigation into the fatal crash of a Bell 212 helicopter in Edmonton, Canada, last week, which found that the outboard main rotor hub strap pin on the accident aircraft had sheared off during flight, causing the main rotor blade and the main rotor head to detach from the aircraft. Bell Textron has also issued an alert service bulletin (ASB) regarding the replacement of affected pins, which it estimates will take approximately 20 hours per aircraft.

“Bell has determined that some main rotor hub strap pins P/N 204-012-104-005 may have not been manufactured in accordance with the engineering design requirements and may shear as a result of the non-conformance,” Bell said in the ASB (PDF). “Although the investigation remains in progress, this ASB mandates that the suspected strap pins with serial number prefix ‘FNFS’ be immediately removed from service.”

According to the Transport Canada AD (PDF), investigators found that the sheared strap pin on the accident aircraft had accumulated just 20 total hours time in service. In addition, an inspection of another Bell 212 found a pin made by the same manufacturer with the same serial number prefix to be deformed after only 29 hours in service. Around 400 aircraft are believed to be affected by the ADs.

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4 COMMENTS

  1. I read both of the linked PDF alerts.

    This is as bad as it gets: “Before next flight.”

    It appears Bell made these life safety-critical pins (“Jesus pins”) in-house, so I’m at a loss on how this mfg. failure happened. (Both Robinson and SpaceX make items this important in-house to increase reliability, but Bell was already making this part themselves.)

    I don’t casually do helicopter flights because of how close to the edge tolerances are. They don’t call it the “Jesus nut” for nothing:

    https://en.wikipedia.org/wiki/Jesus_nut

  2. Ouch.

    Robinson had a problem of premature delamination of rotor blades due inadequate bonding in manufacture. A fatal in eastern Canada, helicopter owner was not doing the simple visual inspections that would show beginning of debonding.

    • FYI: I think Robinson still has a 2,000 hour lifetime on blades, but some startups like the Guimbal Cabri G2 have 6,000 hours or more, plus a bunch of other components with TBOs instead of lifetimes.

      https://en.wikipedia.org/wiki/Guimbal_Cabri_G2

      So flight schools are buying the new designs, which cost about half to operate over the heli lifetime.

      I looked into the Hill HX50. The team behind it has the engineering skill to design and prototype both the engine and body, we’ll see if goes into production. (The appeal of designing your own heli engine is that you can just include the exact accessories needed, reducing weight or increasing HP. Also, 3rd party jet engine makers are very pricey, think $500,000+ per engine.)

  3. “Bell has determined that some main rotor hub strap pins P/N 204-012-104-005 may have not been manufactured in accordance with the engineering design requirements and may shear as a result of the non-conformance,” Bell said in the ASB”.

    That statement from Bell does not sound like in-house manufacturing of those strap pins. While Bell may have originally manufactured them, it sounds like that process was eventually outsourced. I am sure verification will come very soon with a press release placing manufacturing anomalies on someone else other than Bell.