Originally Posted by
helispotter
..... I had always assumed Sikorsky Sea Kings had 5 blade tail rotors while Westland had 6 blade tail rotors. Never understood why the difference. But following search on internet, seems Westland HAS.1 also had 5 blade TR while later variants had 6. Seems it was only in later years, with composite blades, that the TR reverted to 5 blades again. Does anyone here know the reasoning around these changes in number of TR blades?
OK, some dates may be suspect (
) as I dipped in and out of the SK world but, from memory....
Mk1 to Mk2 circa 79/81 - uprated Gnomes with the Mk2 required more TR authority to cope with the higher torque (ie tendency for the helo to rotate!) with the higher powers so went from 5 to 6 blade TR. Both MRBs and TRBs were metal. Late 80's (or Mk 6 era?) a strake was added down the port shoulder of the tail boom to, IIR disrupt the main rotor downwash which tried to "lift" the tail to port. This meant less tail rotor thrust needed to keep straight but it still had the 6 metal blade TR. Again, late 80's(?) the metal MRBs were replaced across the fleets with WHL plastic blades but the 6 blade metal TR was retained.
Carson then came up with his S61 plastic blade late '90's(?) offering quite an improved performance. The UK was interested ...... but no money and Merlin was of course heading inbound so........! Also, independently, Westlands developed a new plastic 5 blade TR which was more efficient and was adopted by the Indian Navy. Of course, for the RN, no money so same old same old........
Roll on Afghanistan and the Mk4 struggled in the ...... wait for it .......
Hot 'n' High conditions!!! Had to get that in!!!!
So, early 2000's, the idea of Carson blades was resurrected and a demo was sorted between Carson/Westlands/Boscombe and the Carson blades proved to greatly improve things both in terms of load lift and top speed. The plan was, at the same time, also to release more power back to the MRH by using the new Westlands plastic 5-bladed TR as part of the same mod - hence a return to a 5 blade TR but now using WHL plastic blades. This was all introduced under an UOR (Urgent Operational Requirement) for just (some?) Mk4s.
Anyway, that's how I recall it all happening tho precise dates are a bit vague in my memory now. The new plastic TR was not retrofitted fleet-wide - just the Carson-bladed Junglies got the new WHL plastic 5-blade TR ...... unless someone knows more!!
Hope that helps! Cheers,
H 'n' H