Spit­fire ori­gins

Pilot - - AIRMAIL -

Ex­cel­lent ar­ti­cle on the Spit­fire Mk VIII, with a touch of the Saint-ex­u­pery and Richard Bach but, al­though it may seem a bit pedan­tic, as folk tales and myths be­come the ‘truth’ if re­peated enough times, can we please fi­nally shoot the old ‘ca­nard’ that the Spit­fire was in­flu­enced by the Heinkel 70?

Let’s look at Su­per­ma­rine’s sit­u­a­tion in 1934. Back in 1931 Mitchell had de­signed the S6B float­plane that won the Sch­nei­der Tro­phy and sub­se­quently set a World Air Speed Record at 407.5mph. His new sin­gle-seat fighter (the Type 224) was no faster than the Gaunt­let bi­plane it was in­tended to re­place. Mitchell wanted speed, at what­ever cost in com­plex­ity. Aero­dy­namic the­ory, prov­ing that an el­lip­ti­cal wing of­fered a re­duc­tion in in­duced drag over any other plan­form, had been avail­able since the twen­ties (Lanch­ester, Prandtl, Joukowski et al) and the new gen­er­a­tion of mono­planes could use­fully take ad­van­tage of that ben­e­fit. Mitchell had a bril­liant young Cana­dian aero­dy­nam­i­cist (Bev Shen­stone) who burnt the mid­night oil with three-di­men­sional cal­cu­lus, log ta­bles, and slide rules (no com­put­ers then) to con­vert the con­cept into re­al­ity. Speed is also a func­tion of wing thick­ness and here Joe Smith (Chief De­signer after Mitchell’s death) pro­vided a novel wing struc­ture al­low­ing T/C ra­tios of 13% root, 6% tip that still en­abled com­bat stresses to be ab­sorbed, not a re­quire­ment for the He70 air­liner. The RAE chipped in with a cool­ing sys­tem de­sign that ac­tu­ally pro­vided thrust rather than drag ( the Mered­ith ef­fect — Ed).

So, rather than be­ing a ‘warmed over He70’, the Spit­fire was a team ef­fort push­ing the bounds of tech­ni­cal knowl­edge. Was the ef­fort worth­while?

Martle­sham Heath re­ports show that the Spit­fire pro­to­type achieved 349mph, while the Hur­ri­cane man­aged 315mph. Both pow­ered by the Mer­lin C. Case proven!

Other air­craft that had el­lip­ti­cal wing forms, but prob­a­bly not the same so­phis­ti­cated de­sign, in­clude: Anf-mureaux 190 f.f 1936 (France) — fighter; Boe­ing XF7B-1 f.f. 1933 (USA) — fighter; Nieu­port De­lage 121 f.f.1932 (France) — fighter; Pi­ag­gio Pc7 1929 (Italy) — Sch­nei­der Tro­phy Racer; Sev­er­sky SEV-1XP f.f. 1935 (USA) — fighter (which evolved into the P-47 Thun­der­bolt); Short-bris­tow Cru­sader 1927 (UK) — Sch­nei­der Tro­phy Racer.

Did their de­sign­ers all form an or­derly queue out­side the Heinkel de­sign of­fice?

As for the el­lip­ti­cal wing be­ing adopted to cover the ar­ma­ment, no way. With the orig­i­nally-spec­i­fied four gun re­quire­ment, it can be seen that we have a nice, com­pact group just out­board of the wheel wells. When this was in­creased to eight, num­bers five and six are still rea­son­ably placed but seven and eight are out near that thin tip; when pulling ‘g’ I do won­der where the bul­lets went!

One fi­nal thing: Shen­stone never worked for Heinkel! He did spend some time with Junkers but, more im­por­tantly, he helped Dr Lip­pisch on the aero­dy­namic cal­cu­la­tions for the DFS 194 all-wing re­search air­craft that de­vel­oped into the Messer­schmitt ME163 rocket fighter.

There, I feel bet­ter now. Mik San­som, Seaton What a joy to be able to read Maxi Gainza once again in Pi­lot! And not once, but twice. Firstly the vin­tage piece in the 50th an­niver­sary is­sue and then the ar­ti­cle on the Spit­fire Mark VIII in the Novem­ber is­sue. The fact that we old read­ers have been graced over the years by nu­mer­ous ar­ti­cles on the Spit­fire does not de­tract from the fresh­ness and read­abil­ity of this piece. I par­tic­u­larly en­joyed and shared the con­sid­er­a­tion that we pi­lots can find mer­its even fly­ing the prover­bial barn door.

All in all a very en­joy­able read that brought me back to years past when Maxi was a reg­u­lar contributor to this mag­a­zine and was writ­ing in­formed ar­ti­cles in his beau­ti­ful lin­ear English that only a for­eigner can muster. I am look­ing for­ward to read­ing the next in­stal­ment in the De­cem­ber is­sue. Alex Bu­rani

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