The Tay name is given to two Rolls-Royce jet engines. The original was a follow-on to the Nene that was used on small numbers in the 1950s, the newer one a massively upgraded version of their famous Spey turbofan design.

The original Tay was essentially an (optionally) afterburning version of the Nene, aimed at the same military market that the Nene served. It saw little use in England, but the design was licensed by Pratt & Whitney as the J48 and saw extensive use in several versions of the Grumman F9F Panther and F-94 Starfire, and by Hispano-Suiza as the Verdon which was used in the Dassault Mystère IV .

The newer Tay is a development of the Spey, using the low-pressure components from the famous RB.211 to produce a version with considerably higher bypass ratio. The Tay has been used on a number of small airliners and larger bizjets, including the Gulfstream IV , Fokker F70 and Fokker F100, with later versions being used to re-engine Boeing 727's and Douglas DC-9s.

Tay 611

Thrust: 13,850 lbf (62 kN)
Aircraft: Tay 611 entered service in 1987 on the Gulfstream IV/IV-SP, for which it is the exclusive powerplant.

Tay 620

Thrust: 13,850 lbf (62 kN)
Aircraft: Fokker F70 from 1988, Fokker F100 from 1994

Tay 650

Thrust: 15,100 lbf (67 kN)
Aircraft: Originally designed to re-engine the BAC One-Eleven, the 650 entered service on the Fokker 100 in 1989 .

Tay 651

Thrust: 14,400 lbf (64 kN)
Aircraft: Boeing 727-100 from 1992 and Douglas DC-9.