Technical correction issued regarding Hughes 369E rotor blade machining

Casualties unknown • Glastonbury, Somerset, GB

An AAIB bulletin correction has clarified specific machining dimensions for the inner edge of rotor blade pockets on a Hughes 369E.

What happened

Following an earlier publication in AAIB Bulletin No 2/2012, a technical correction was issued regarding the manufacturing specifications of rotor blades. The correction pertains to the precise machining requirements for the internal edge of the pocket area on certain components.

The investigation

During the review of previously published material, it was identified that the measurement for the corner radius within the blade pocket was recorded incorrectly. The investigation into the documentation established that the original figure provided was inaccurate.

Findings

  • The original report stated a corner radius of 2.29 mm (0.090") for the inside edge of the pocket.
  • The corrected specification establishes that the inside edge of the pocket was actually machined to provide a corner radius of 0.254 mm (0.01").

Probable cause

The error was a typographical inaccuracy in the published measurement of the blade pocket corner radius.

Frequently asked questions

What happened in the 2011-06-19 McDonnell Douglas Helicopters Hughes 369E accident near Glastonbury, Somerset, GB?

An AAIB bulletin correction has clarified specific machining dimensions for the inner edge of rotor blade pockets on a Hughes 369E.

What aircraft was involved and where did it happen?

The accident on 2011-06-19 involved a McDonnell Douglas Helicopters Hughes 369E, registration G-KSWI, at Glastonbury, Somerset, GB.

What was the probable cause of the accident?

The error was a typographical inaccuracy in the published measurement of the blade pocket corner radius.

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