The 1950s and 1960s were truly a marvelous era for Av Geeks. It was a transition from the graceful lines of the Lockheed Connie and Convairs to the first generation of screaming turbojets (what’s a fan?) pouring out obscene contrails of black smoke. The pilots were dashing, the flight attendants classy. It was also an era of experimentation and ideas. One such idea was how to reach passengers in rural or austere areas of the country which could not otherwise be supported with the current fleet of aircraft. And that is where this story begins…
In 1968, the population of the entire United states was 201.2 million. For context, the current population is approximately 332.6 million, which represents a 65.3% increase. The population density and demographics were considerably different in 1969 than they are now, with much of the population living a more rural existence. A lot of the major suburbs that we see know were still farm communities in the 1960s. Also, the Vietnam War was in full swing at the time, and air travel was not readily available in a lot of communities on the outer reaches of the U.S. The Breguet could potentially connect communities like Joliet and Bloomington or even Meigs in downtown to Chicago O’Hare or connecting Westchester and Connecticut suburbs to JFK.
Since the late 60’s, airports which would have been target markets have since grown considerably in infrastructure and capacity. In fact, towered GA operations in 1970 were less than half of what they would be in 1979, a remarkable feat considering the oil crisis was smack dab in the middle of that decade. This is an indicator of the self-reliant, uncontrolled nature of aviation that defined an era. But these airports lacked the characteristics to support even the most robust prop-driven commuters of the time.
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Along with vast expanses of rural America, American Airlines also sought out to reach the downtown districts of America. The idea being that commuting passengers could be picked up and delivered much closer to their destinations in airports which had much smaller footprints. In the era 1960s, jet airliners needed enormous distances for takeoff and rollout; there being no such thing as a CRJ-200s (thank God); no B737-800 operating on sub-6,000’ runways either.
A Short Takeoff and Landing concept was imagined, one where very short and marginally improved runways could be put into service for commercial air travel. And by short, we are talking 1,500’. Since turbojets were still quite new in their evolutionary development, the aircraft would be propeller driven, have a wing with a lot of lift, lots and lots of flaps, and a rugged landing gear system.
The Prototype Breguet 941
In collaboration with McDonnell Douglas American decided on the obscure Breguet 941, a defunct design from the French aircraft company Breguet. The 941 was a quad-engine, high-wing monoplane with a relatively short range of around 500nm, depending on configuration. Seating would have been just shy of 60 passengers.
On the surface, it honestly looks like a slightly smaller C-130…but looks can be deceiving because the appearance is only skin deep; the 941 held some seriously interesting design features.
First and foremost were the engines. The 941 was powered by four Turbomeca Turmo III turboprop engines, rated at 1,500shp each. Okay, no big deal right? Well, the Turbomeca engines were originally designed for helicopter use and employed a common method among helicopters of power going through a transmission box rather than going directly to the rotor, for obvious reasons; power must be split in a helo to either a second tandem blade or more commonly to the tail rotor. However, fixed wing turboprop engines run more or less directly to a prop (for simplicity sake I am omitting talking about reduction drives, etc).
Breguet was keenly aware of an issue which has plagued traditional multi-engine aircraft since their inception which is the imbalance of power and torque when you lose an engine. In a four engine aircraft, you essentially are losing an additional engine to the one which is already out to compensate, making for a potentially dangerous situation. The 941 employed a radical system to address this issue: run all power through a central gearbox and run all of the propellers off of a central driveshaft. That’s right folks. In the event of a single engine failure, the aircraft still had 75% of it’s available power and all four props would still produce equal thrust.
One other design characteristic of the 941 that is noteworthy are the flaps. This design just blows my mind. To say that they barn doors is a tragic understatement; the 941 was designed in the deflected-slipstream technique to optimize lift. The flaps were full wingspan and double-slotted, and had a maximum deflection of 98° for the interior flaps, and 65°for the outer flap sections. With so much surface area devoted to flaps, the 941 adopted a common control surface technique in utilizing four spoilers for roll control.
Downsides to the Breguet 941
As truly interesting and unique as the Breguet 941 was, American Airlines ultimately scrapped the joint venture with McDonnell Douglas and only four of the aircraft were ever built. The interconnected propeller system is a great idea which is a considerable safety feature, but it also added a lot of weight to the aircraft in regard to the central gearbox and drive shafts. These added considerable complexity to the aircraft as well, and as we all know, complexity equals cost. The design just did not solve enough problems to implement it, but it is certainly a totally unique design for Av Geeks to ponder and admire.