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  • Writer's pictureJ.K. Caldwell

Stinson SM-8A Junior

Photography by Roger Cain

First Impressions: If you enjoy flying low and slow with your arm out the window on a warm day while checking out the landscape below, you’ll love the Junior! The SM-8A is an easy-to-fly classic cabin monoplane that is comfortable for both pilot and passengers. From the outside, this 90+ year old vintage plane looks like it belongs in a museum but remains relevant and reliable as a touring airplane for the right collector.

Background: With open-cockpit aircraft still very much the norm in the 1920s, comfort was a relatively new concept in aviation. The Stinson Aircraft Corp. developed the SB-1/ SM-1 Detroiter in 1926 and it was a big success as a “modern” six-seater. It had an electric starter and an enclosed (and heated) cabin for both pilot and passengers. Because of its reliability, safety and comfort, a couple airlines used it for regularly scheduled flights. In order for Eddie Stinson to market his successful monoplane design to a wider customer base, he created a scaled-down version of the Detroiter, the SM-2 Junior. The “Detroiter Junior” or “Baby Detroiter” hit the market in 1928 as either a three or four-seater and continued to evolve with bigger engines (including a Packard diesel), larger cabin area, float and ski options, and even retractable undercarriage. Production ended in 1933 with a total of 321 Junior models built. The model flown for this article was a 1930 SM-8A with a 225 hp Lycoming R-680.

Photo by Roger Cain. Yes, that's the copilot's arm!

Design Features: Your first impression walking up to a Junior is how substantial an airplane it is. With a 41’8” wingspan and gross weight of around 3,200 lbs., it is not a small aircraft, by modern four-seater standards. The wings are braced with dual, parallel (airfoil-shaped) struts that connect to the landing gear struts and braces. The landing gear is an oleo strut system and includes an external retention cable for when the struts are extended in flight. Large flush-mounted Grimes lights are located under both wings. When selected, they pivot down and forward before illuminating.

Two large doors and convenient two-rung ladders make access into the cabin easy. As you step up the ladder, there is a leather loop on the door frame for assistance in climbing aboard. Even though it doesn’t seem necessary, there is a small inward swinging door on the port aft side of the cabin for loading baggage behind the back seat. Once in the cabin, you’ll notice there is no shortage of leg room in the back of a Stinson Junior and no tiny eyeball air vents for Stinson passengers - both rear seat passengers have a sliding window for all the fresh air they want! Up front, the cockpit is pure 1920s. Both the pilot and passenger/copilot have a commanding view out the front, even with the tail on the ground.

Powerplant: The SM-8A was introduced in 1930 and originally came with a 215 hp Lycoming R-680, the first year that engine was produced. After WWII, the market was flooded with surplus, later-model R-680s. The SM-8A I flew had a 225 hp R-680 installed, coupled to a metal ground-adjustable propeller from the Standard Steel Propeller Co, before they were combined to form Hamilton Standard. Sixty-one gallons of fuel, stored in two wing tanks provide about 5 hours of flight time.

Photo by Roger Cain

Preflight/Taxi: Everything, including the engine, is straightforward and easily accessed during the preflight inspection. Fuel quantity is indicated via a red bobber in a glass sight gauge that protrudes from the underside of the wing, making one wonder what would happen if a bird strike took it out. The uncowled R-680 makes even a detailed inspection easy. Because the nose is fairly high, walking the propeller through to check for hydraulic lock is a little easier with a second person. After climbing into the cabin, ensure the doors are secured and your passengers are comfortable and briefed before settling in up front. Once in the cockpit, roll down the windows with car-style hand cranks and buckle up. The first feature that you’ll notice in the cockpit is the beautiful polished mahogany steering wheels. The second notable feature you will notice is the long lever with the squeeze grip located between the pilot and copilot’s seats. No, it’s not a gear-shifter or even a flap handle (there are no flaps). It is a trim lever and will be important to familiarize yourself with prior to taking flight. The trim lever requires that you squeeze the grip lever, and move the lever to one of nine detents before releasing. If your first time operating this unique system is during flight with air loads on the elevator, there is a good chance you will not be prepared for how the actuation works and you will release all trim. Trust me when I say this can be quite startling and will require significant control inputs to counteract the air loads while you wrestle with the lever! The trim lever does take some getting used to, but once you have it figured out, you’ll find it is actually not a bad system.

Photo by Roger Cain

There are upper fuel shutoff valves at eye-height and low fuel shutoff valves by the pilot and copilot’s ankles in addition to a main shutoff valve on the copilot’s side of the instrument panel. Aviators in the 20s and 30s were very aware of cockpit fires and rightfully so. Ensure all the valves are open before priming the cylinders and shouting “CLEAR!”. Push the starter, count nine blades, and turn the magnetos on. Perhaps, with a little help from the throttle, the cylinders will fire and belch white smoke one at a time until all nine are rhythmically chugging. Taxi is straightforward and accomplished with a steerable tailwheel and differential braking. There is also no need to swerve to see in front of the nose.

Flight Characteristics: After run-up and pre-takeoff checks are complete, take the runway and pour on the coals. Do not expect 225 horsepower to accelerate 3,200 pounds quickly. Fortunately, you’ve got 236 square feet of high-lift wing to get you airborne so it won’t be long until you’re climbing away. This airplane will get you where you’re going in style, comfort and safety, but not quickly. It’ll cruise at about 110 mph at 1900 rpm on a good day, while burning around 12 to 13 gallons per hour. It’s a stable aircraft with very forgiving flight characteristics for even the most ham-fisted of aviators. This airplane truly flies like a very large Cub!

Landing: Landing characteristics are generally good but it is worth noting that the landing gear oleo struts will compress at slightly different rates even with a perfectly smooth touchdown with no wind, requiring some “undeserved” counter corrections. It can be wheel landed without much difficulty and even the relatively small rudder is far enough back that a three-point landing will still provide ample directional control and the large ailerons maintain roll authority even at very slow airspeeds.

Photo by Roger Cain

Wrap-up:The Stinson Junior is certainly a rare and classy bird from the “Golden Age of Aviation”. Unlike many early designs, it was a genuinely good one that has stood the test of time. The Stinson “Detroiter Junior” was born at the perfect time - when aviation had matured enough for safety, comfort and reliability to actually be design characteristics, not just afterthoughts.Aviators of the 1920s and 1930s appreciated the Stinson Junior and aviators of the 2020s continue to appreciate them.

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1 Comment

Mar 12, 2023

😍I like the arm out the cockpit picture. Very interesting article and well written! You should continue to pursue a writing/flying career.

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