Nice to see this thread back on track
Before we start I would like to say that I am a pilot and not a helicopter engineer, but this post has been written in conjunction with the engineer that disassembled the aircraft. I have described what was found. The A.A.I.B. were present and I am sure that a full report will be published in the future. From my own point of view I have a few hours on the R22 and therefore have an interest in the continued airworthiness of the type. Nothing I saw gave me any concern about the design of the aircraft and it is a testament to the strength of the blade design that it had remained intact.
The helicopter in question landed at Biggin Hill airport with a vibration. The local maintenance company (Not the company responsible for the maintenance of the aircraft) were asked to investigate the problem. On initial investigation it was discovered that there was a crack from the trailing edge of the blade to just before the “D” section at the leading edge of the blade approximately one third of the span from the root. The crack was through both top and bottom skins and the honeycomb. It was noted that the rotor head was unable to flap about the teetering hinge. The blades were removed from the aircraft and then the head was removed. During the disassembly of the rotor head it became very clear that the head was unable to teeter. The head was then stripped and it was discovered that the shims that are required to be fitted in-between the surface of the rotor head and the thrust washers were absent. In my humble opinion it would seem that since the head was unable to teeter the rotor blade had to take the stresses that teetering would normally allow and therefore the crack developed.
They were very lucky.