407 mast failure

[rotormatic]

INFORMATION LETTER 407-03-68

TO: All Owners/Operators of Bell 407 series Helicopters

SUBJECT: BELL 407 MAST – INCIDENT REPORT

 

This Information Letter is issued to advise of an unusual incident and to stress

the importance of adhering to the published Bell 407 maintenance procedures.

 

On 9 January 2003, a Bell 407 was flying in the Gulf of Mexico when the pilot

heard a noise, detected a vibration, and returned to his base for an investigation.

Visual inspection found a crack indication in the mast pole below the swashplate

drive hub and above the swashplate boot.

 

The crack extended circumferentially around approximately 40% of the mast outer diameter.

 

This is the first reported occurrence of this nature since Bell 407 deliveries began in January 1996.

 

While the cause of the crack has not yet been determined, preliminary

investigation reveals that the mast pole had been painted in the cracked area

and that corrosion was also visible. In view of the above the following points are

stressed:

 

· As noted in the CR&O manual the mast pole is not to be painted in that

area;

 

· Routine inspection is necessary to detect and remedy any sign of

corrosion during daily checks and scheduled inspections.

 

The Bell 407 comprises approximately 545 aircraft and has accumulated close to

800,000 flight hours. Bell Helicopter has given this investigation the highest

priority and operators will be informed of the results and further action if any, as

soon as possible.