I have collected some material on the "Racer" but haven't spotted the JA.5 designation before. Where did you find it?
That 'J.5' for the Heston Type 5 Racer seems to have originated with
The Aeroplane and
Flight.
There's a lot of confusion (and speculation) around Heston Aircraft Company designations. Initially, Heston just used Type numbers - beginning with the Type 1
Phoenix. Later, Heston began applying designation prefixes in the JA. and JC. series. After WW2, the S.B.A.C. designation system incorporated some these codes into its series as well.
There is also some uncertainty about the presentation of these designations. They are seen with one dot (between prefix and number); two dots (one after each prefix letter); a space between letters and number; no space at all; or a hyphen between letters and number (which also became the official style for S.B.A.C. designations.
-- Eg:
Air Pictorial and Air Reserve Gazette, Vol XIII, No.12, Dec 1951, pg 365
FWIW, the Heston designation list I have follows:
Heston JA. Series
JA.1 - 1935 Heston Type 1
Phoenix 5-seat cabin tourer; x 6
- JA.1
Phoenix I : 1 x 200 hp DH
Gipsy Six srs I; span 12.29 m
- JA.1
Phoenix II: 1 x 205 hp DH
Gipsy Six srs II; span 12.29 m
JA. 2 - (Project)
Griffin; 6-seat
Phoenix development
- JA.2: 1 x 290 hp Wolseley
Scorpio 9-cyl. radial; span (??)
JA.3 - 1938 Heston 2-seat trainer monoplane to T.1/37; x 2
- JA.3: 1 x 200 hp (?) DH
Gipsy Queen; span 12.80 m
JA.4 - (Project) T.7/37 RAF communications a/c; no details (??)
JA.5 - 1940 Heston Type 5 Racer; aka Nuffield-Napier-Heston Racer
- JA.5: 1 x 2,450 hp Napier
Sabre H24 engine; span 9.76 m
JA.6 - JA.7 - (??) speculative
JA.8 - 1941 Boulton Paul P.92/2 half-scale turret fighter prototype
- JA.8: 2 x 130 hp DH
Gipsy Major II 4-cylinders; span 10.00 m
Heston JC. Series
JC.1 - (Project) T.23/43 RAF elementary trainer; (??) no details
JC.2 - JC.4 - (??) speculative
JC.5 - (Project) A4/45 (OR.164) Army 3-seat communications a/c
- JC.5: 1 x 240 hp de Havilland
Gipsy Queen; span (??) m
-- A.4/45 contestants proved under-powered; contest cancelled
JC.6 - 1947 A.2/45 (OR.176) AOP prototypes; x 2 (VL529 & VL530)*
- JC.6: Tandem 2-seater; twin-boom pusher; fixed tricycle u/c
- JC.6: 1 x 240 hp de Havilland
Gipsy Queen 33; span 13.00 m
-- * VL530 not flown; VL531 & VL532 serials assigned; not built
-- Saro P.100: (Project) Saunders-Roe floatplane variant; not built
JC.7 - JC.8 - (??) speculative
-- Heston was a sub-contractor for Barnes Wallis'
Wild Goose*
-- * Alas, no evidence ties JC.7 or JC.8 to
Wild Goose project
-- There is alternative speculation on JC.7 & JC.8 in the thread
JC.9 - (Project) Variable-geometry wing demonstrator for Vickers*
- JC.9: PoC vehicle for Barnes Wallis'
Swallow SST concept
- JC.9: 1 x 870 lbf AS ASA.1
Adder jet;** span 11.58 m (unswept)
-- * Delivered to Vickers Weybridge; never assembled; scrapped
-- ** Meant to first fly as glider, then with S-intake fed turbojet
