Last week we had a plane with an awesome name and an unusual aerodynamic configuration. This week, the aerodynamics are fairly normal, but the name is strange and the powertrain is even stranger - the Beechcraft Model 34 'Twin-Quad'
Twin-Quad? Don't those mean two different things? Why yes of course they do Johnny, but this plane IS indeed a Twin-Quad! It's a twin prop, quad motor aircraft.
See how there are two inlets, one on either side of the prop? Those are cooling holes for the two engines that drive each propeller. Here's a closer view:
And on the inside, it's arranged like this:
Two Lycoming GSO-580 engines were connected through an automated clutch system to power one propeller. The clutch was designed so that in the event of a single engine failure, the prop could still operate.
So why are the engines arranged like this? Well, it's actually pretty innovative. The airfields the Twin-Quad was expected to fly from varied from large, established airports to small fields, sometimes even rough fields, in smaller towns and communities. This meant that the Twin-Quad needed to be capable of short take off and landing. One way to improve STOL performance is to run a large prop at a very low RPM, producing more thrust at lower speed, which is exactly what the twin quad was designed to do. By using two smaller engines instead of one large engine, the engines could also be embedded in the wing. The Twin-Quad was the first aircraft to do so, and this reduced drag and also improved the lift gained by blowing air over the wing with the prop. The aircraft had excellent STOL capabilities as a result, and this type of arrangement for STOL has been used since, most notably in the Boeing YC-14 concept
Beyond the engines, the cabin configuration was actually pretty unique. This was designed as a feeder aircraft, to fly short distance routes connecting smaller towns and cities to the large hubs of the day. A lot like regional jets today. This was seen as a huge market post WWII as air transport became more common. To better suit the needs of regional carriers, the cabin carried 20 passengers but could easily be rearranged to carry cargo instead, or a combination of the two. Seats folded up into the ceiling and the bulkheads could be moved, so not only could it be rearranged, it could be rearranged from flight to flight. This was revolutionary
I praise this aircraft as it's an excellent design. So why have you never heard of it? It was a failure, as were any other aircraft designed for the same job. Why? Well, after WWII, airlines bought up surplus C-47's and converted them back into DC-3's for carrying cargo and passengers. These were much less expensive than new built airplanes, and did the same job as well if not better. C-47's were so good at the job that many are still doing the same job today, which is why I consider the DC-3 to be the single greatest aircraft ever designed.
Usually at this point I would tell you where you can go see a Twin-Quad in person, but unfortunately you cannot. The only Twin-Quad suffered an engine failure after takeoff and made a forced landing in a field in Wichita, KS in January of 1949. An electrical fire led to the accidental operation of a master battery switch, killing power to all four engines. The crash killed one person and injured two others, and the aircraft was damaged beyond repair. At the time it was clear that the DC-3 would win the battle for regional carriers so Beechcraft abandoned the project.
For more information on the powerplant, visit this page: http://www.flightglobal.com/pdfarchive/vie…
Next week I don't know what I'm going to write about. I'll pick something. If there's an era or type of airplane you'd like to see, I'm open to suggestions.