A.T.C. #678 (4-29-38) STINSON "RELIANT", SR-10C

The Stinson "Reliant" had always been a masterpiece of classic styling and it is remarkable that it could be steadily improved just about every model year. For 1939, once again the "Reliant" was improved in the new SR-10 series, and this time there were some 25 structural and aerodynamic changes. It is nigh onto impossible to make something that's already good, any better, but Stinson design-engineers met this same challenge just about every model change, and proved again in the SR10 they were quite equal to the task. The new SR-10 was a big, beautiful airplane and it is easy to see where the designers had done their work. The formerly rigid cabin entrance steps were now retracted out of sight, cabin doors were flush-mounted to reduce surface drag, all junctures were smoothed out, the whole inside was completely restyled, and pilots were treated to fingertip control. The redesigned engine cowl was very snug for reduced drag, and the exhaust system was greatly improved. There was much more than this, of course, but it had to be seen and felt to be fully appreciated. Each year the "Reliant" was getting a little heavier, and sometimes a little bigger, but it remained always a marvelously graceful airplane. The SR-10 series more or less fell into 3 different groups, and the groups under consideration here were all powered with various "Lycoming" engines. The SR-10B (economy model) was powered with the 9 cyl. R-680-D6 engine of 245 h.p., the SR-10C (standard model) was powered with the R-680-D5 engine of 260 h.p., the SR-10G was powered with the R-680-E1 engine of 290 h.p., the SR-10H was powered with the R-680-E2 engine of 280 h.p., and the SR-10J was powered with the R-680-E3 engine of 300 h.p. Here indeed was a selection of airplanes that would suit just about any need and preference. Of the 5 models offered with power by "Lycoming," the SR-10C seemed to have the edge and became the most popular version. Prices for the new "Reliant" ranged at or above $12,000, so not too many were bought by private-owners; just about all of the new "Reliant" went to corporations, and the larger commercial operators. Each of these new "Reliants" were as versatile as any that were ever built, and operated on wheels, skis, or floats. Some were even drafted by the USAAF for wartime service.

The Stinson "Reliant" in the SR-10 series was a high-winged cabin monoplane of imposing proportions with seating arranged for four or five. Because of the ominous shaping of world events, Stinson designers and engineers sensed that perhaps this would be the last of the "Reliant" series; because of this they channeled their efforts into making this series the finest that was ever put together. An airplane of this type could not be built cheaply, so the price tag was relatively high; this narrowed down the circle of potential customers, and drew the "Reliant" into competition with other airplanes that promised just as much for about the same price. Still, the "Reliant's" reputation was known far and wide, so it did not suffer too badly in the competition. The most prolific group in the SR-10 series were all powered with the 9 cyl. "Lycoming" engine, and with 5 of these models to choose from a customer was bound to better fit his particular needs. In this group there were the SR-10B, SR10C, SR-10G, SR-10H, and SR-10J; an SR10G3 and SR-10J3 were also available. Only 2 of the SR-10B were built, and the SR-10H was offered, but apparently not produced. The power spread in this group was from 245 h.p. to 300 h.p., and it stands to reason that the "Reliant" itself was much happier with the more powerful engines. As powered with the Lycoming R-680DS engine of 260 h.p. the model SR-10C was the happy medium in price and in performance, so it became more or less the favorite. The SR-10C had a marvelous performance and a very deliberate character. Reaction was generally a little bit slower than what "Reliant" pilots were used to, but very precise, and there was no need for all that hurry - she did everything best in her own time. This is not to say she couldn't be "spurred," she could indeed, but she was happier having her own way. The (245 h.p.) SR-10B was on the low end of the scale, and the (300 h.p.) SR-10J was on the high end of the scale; so then, performance and character would vary accordingly. The type certificate for the SR-10 as powered with various Lycoming engines was issued 4-29-38 and some 45 to 50 examples were built in all. Manufactured by the Stinson Aircraft Corp. at Wayne, Mich.

Listed below are specifications and performance data for the "Reliant" model SR-10C as powered with Lycoming R-680-D5 engine rated 245 h.p. at 2100 r.p.m. at sea level (260 h.p. at 2300 r.p.m. for takeoff); length overall 27'8"; height overall 8'7"; wingspan 41'II"; max. wing chord 96"; total wing area 258.5 sq. ft.; airfoil Mod. Clark Y; wt. empty 2530 lbs.; useful load 1345 lbs.; payload with 76 gal, fuel 682 lbs. (3 pass. & 171 lbs. baggage, or 4 pass. & no bag.); gross wt. 3875 lbs. (later raised to 3900 lbs.); max. speed 150 at sea level; cruising speed (.75 power) 147 at 7000 ft.; landing speed (with flaps) 57; climb 880 ft. first min. at sea level; ser. ceiling 13,500 ft.; gas cap. 76 gal.; oil cap. 5 gal.; cruising range (.75 power at 4600 ft.) at 16 gal. per hour 660 miles; price $10,995 at factory. The SR-IOB had Lycoming R-680-D6 engine rated 225 h.p. at 2100 r.p.m. at sea level .(245 h.p. for takeoff) and all specifications were identical, except for slightly lower performance. The SR-10C was eligible as seaplane on Edo 39-4000 twin float gear at 4210 lbs. gross wt.

Listed below are specifications and performance data for the SR-10G and SR-10J in that order. The SR-10G was powered with Lycoming R-680-E1 engine rated 275 h.p. at 2200 r.p.m. at sea level (290 h.p. at 2300 r.p.m. for takeoff), and SR-10J was powered with R-680-E3 engine rated 285 h.p. at 2200 r.p.m. at sea level (300 h.p. at 2300 r.p.m. for takeoff); length overall 27'10"; height overall 8'7"; wingspan 41'11"; max, wing chord 96"; total wing area 258.5 sq. ft.; airfoil Mod. Clark Y; wt. empty 2605 (2610) lbs.; useful load 1395 (1390) lbs.; payload with 76 gal. fuel 730 lbs.; payload with 100 gal. fuel 573 lbs.; gross wt. 4000 lbs. with 6-ply tires, otherwise at 3900 lbs., max. speed 160 at sea level; cruising speed (.75 power) 150-152 at optimum altitude; landing speed (with naps) 59; climb 920-930 ft. first min. at sea level; ser. ceiling 15,000 ft.; gas cap. 76-100 gal.; oil cap. 5-7 gal.; cruising range (.75 power at 7000 ft.) at 18 gal, per hour 600-800 miles: price approximately $12,585 at factory. The SR-10H was offered with R-680-E2 engine rated 265 h.p. at 2200 r.p.m. at sea 1eve1(280 h.p. at 2300 r.p.m. for takeoff); all specs were the same and performance was only slightly less. The latest offerings were the SR-10G3 and SR-10J3.

The construction details and general arrangement of the "Reliant" had been more or less the same for several years now, and the SR-10 series varied only in basic detail. Interiors progressively got bigger and a little finer, the entry doors were getting bigger and getting in was easier, vision was constantly being increased or improved, extra fuel capacity was allowed for greater range, and in-the air or on-the-ground operation was enhanced by electric or hydraulic aids; outside of this the "Reliants" were still pretty much alike. The most significant difference in the new SR-10 series was particular attention to reducing drag, the addition of little niceties that would appeal to prospective buyers, and enhance their desire for comfort. Standard equipment that was normally installed left very little to be desired, but many useful options were still available. Some customers opted for just bare minimums, but others insisted on all that was available; this usually amounted to several thousands of dollars extra. Like its earlier counterparts the SR-10 was also a very versatile machine; it was just as happy in being a well-kept "executive transport" for some corporation, or hauling supplies to some wilderness camp. The SR-10 had room enough for 5, but fuel load had to be reduced if any amount of baggage was carried; with normal fuel load, 3 passengers and a pilot, the baggage allowance was 150 lbs. The cabin was tight, quiet, stylish, and could be very plush; a far cry from the Stinson of 10 years previous. All control surfaces were aerodynamically balanced for fingertip control, and the pilot had everything he needed within easy reach. A Lycoming-Smith controllable prop, electric engine starter, battery, generator, fuel gauges, carburetor heater, compass, clock, dual control wheels, navigation lights, hydraulic wheel brakes, 7.50x10 wheels with 8.50x10 tires, parking brake, cabin heater, cabin vents, vacuum-operated wing flaps, bonding & shielding, full-swivel tail wheel, map pockets, ash trays, nickeled hardware, assist ropes, and first-aid kit were standard equipment. A Hamilton-Standard controllable prop, wheel pants, landing lights, para-flares, pressure-type fire extinguisher, extra fuel tanks, radio gear, Edo pontoons, custom interiors, and custom colors were optional. The next "Reliant" development was the Wright-powered SR-10D and SR-10E as described here in the chapter for ATC# 679.

Listed below are Lycoming-powered SR-10 entries as gleaned from registration records:

This approval for ser. # 3-5801, 5901 and up; 5800 series were manufactured in 1938, and 5900 series were manufactured in 1939 and beyond; only 2 of SR-10B were built; records note that 46 of SR-10C were built, 12 of the SR-10G, none of the SR-10H, and 11 of the SR-10J, this includes SR-10G3 and SR-10J3 versions; OK-ATZ was SR-10C in Holland, and G-AFVT was SR-10J in England (ser. nos. unknown); ser. # 3-5813 del. to Scintilla Magneto Co.; ser. # 3-5824 del. to Dept. of Aero., State of Mich.; ser. # 3-5830 del. to Shell Aviation of St. Louis-later modified to SR-10G; ser. # 3-5838 del. to Penna. State Police-later modified to SR-10G; ser. # 3-5842 del. to Florida State Road Dept.; ser. # 3-5828, 3-5844, 3-5854-55-56 del. to All American Aviation (2 or 3 pl.) for experiments in airmail pick-up; ser. # 5919 del. to Maine Dept. of Fisheries; 5 of SR-10C in USAAF as UC-81K and 2 of SR-10G as UC-81A; this approval expired 2-28-41.

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