American’s 1969 STOL Aircraft Evaluation – What You Need To Know

In the spring of 1969, American Airlines conducted a 75-hour short takeoff and landing (STOL) evaluation with McDonnell Douglas. The two United States-based firms used French-designed aircraft in the form of the Bréguet 941 for this experiment. However, the plane didn’t end up joining the Texan carrier’s fleet.

American Airlines STOL
It would have been a rare treat to see American Airlines’ classic livery paired with Mcdonnell Douglas’ branding on this STOL aircraft. Photo: American Airlines via Twitter

A helpful type

STOL aircraft are designed for operations that rely on short runways. Many of them also have features for use on runways with sensitive environments. For instance, services at airports at high altitudes or fields with icy conditions are often better suited to be performed with STOL models.

The Bréguet 941 was a four-engine turboprop STOL aircraft developed n the 1960s. The 941 prototype was tested heavily in both France and across the pond. In the US, a license agreement had been formed with the McDonnell Aircraft Corporation. The prototype would be known as the McDonnell 188 in the country. It was evaluated by NASA and the military. Additionally, carriers across the nation tested out the improved 941S. However, no orders were ever made in the US for type.

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Quick to depart

American was one of the US airlines to try out the plane. However, the operator wasn’t convinced to take on the aircraft despite the positive results.

“Did you know? In 1969, in conjunction with the McDonnell Douglas Corporation, we evaluated the French-designed Breguet 941, a short takeoff and landing (STOL) aircraft, for short-distance flights from small airports,” American shared on Twitter.

“With only seven seconds to takeoff, STOL planes were able to use runways of about 1,500 feet. In the end, we never ordered the aircraft, but c’est la vie.”

Breguet 941
A photo of a Bréguet 941 held by the French Air Force – American Airlines evaluated the enlarged version of this model, the 941S. Photo: Getty Images

In-depth tests

According to a Society of Automotive Engineers document written by Robin K. Ransone, shared by SAE Mobilus, the 941S that American tested was fitted with Butler-National, Decca, and Litton 3-D RNAV systems, along with a Singer-General Precision, Inc. microwave landing guidance system. Data were obtained on the plane and STOL/RNAV operational procedures. Approximately 9,800 frames of onboard position indications were recorded and correlated “with precision, ground-based tracking radar measurements to quantitatively determine the RNAV and TALAR systems’ accuracy and repeatability.”

The document highlights that American had not yet decided to conduct commercial STOL operations. It had been studying it from an integrated system standpoint. To gather this information, the 75-hour STOL evaluation program was conducted. The wing of the Model 188 was wholly immersed in the propeller slipstream, developing “Propulsive Lift” for slow speed flight. The fuselage of the plane was approximately the same length as an F27 unit.

Flight at notably slow speed was possible because of the high lift offered by large, full span, triple-slotted trailing-edge flaps. The final approach and landing were conducted with a propeller control technique named “transparency.” This placed the inboard propellers at a high pitch and the outboard propellers at nearly flat pitch. This was a considerably high drag setup that allowed a high power setting and steep descent angle with an indicated airspeed of approximately 65 knots.

Breguet_941S
The Bréguet 941S had a capacity of 57 civil passengers, a length of 23.75 m (77 ft 11 in, a wingspan of 23.4 m (76 ft 9 in), and a height of 9.65 m (31 ft 8 in). Photo: PpPachy via Wikimedia Commons

Successful outcomes, but not convincing enough

Overall, the results indicated that STOL with RNAV is technically feasible and has operational benefits. All of the equipment tested was conceptually satisfactory. However, both the test unit and the RNAV systems weren’t satisfactory for the carrier to use in the form they were in at the time.

American wasn’t the only US operator to carry out these types of evaluations. According to the Civil Aeronautics Board Reports, Volume 55, Eastern Air Lines also worked with McDonnell Douglas on a STOL demonstration project. However, like its counterpart, it didn’t take on the 941S either.

“The STOL demonstration project conducted by Eastern and McDonnell Douglas established that STOL aircraft can be operated into and out congested areas without creating undue noise problems and with comfort to the passengers. It also shows that such aircraft, outfitted with proper guidance and control equipment, can be operated independently of CTOL traffic in the airlanes as well as in the terminal areas,” the Civil Aeronautics Board shared.

“By means of area navigation, the aircraft was operated in airspace not being used today. This is described more fully, infra. The demonstration project was not designed to provide data on air carrier operating costs. It did provide valuable data on aircraft operations and navigation.”

Le Bréguet 941 Aircraft
In total, including prototypes, only six units of the Bréguet 941 family were produced. Photo: André Cros via Wikimedia Commons

It wasn’t meant to be

The four produced Bréguet 941S units entered service with the French Air Force in 1967. They went on to serve until 1974. The variant had a range of 1,000 km (540 NM), a maximum speed of 450 km/h (280 mph), and a cruise speed of 400 km/h (250 mph). It also had a service ceiling of 9,500 m (31,200 ft) and a take-off run: 185 m (607 ft) at 22,000 kg (48,502 lb).

American Airlines may not have taken on the type, but it undoubtedly would have learned about some crucial details with these evaluations. Nonetheless, it would have been interesting to see where it would have deployed these planes at the time. Many passengers of the airline undoubtedly would have loved to fly on the aicraft if they had the chance.

Simple Flying reached out to American Airlines for further details on its short takeoff and landing evaluation with McDonnell Douglas in 1969. We will update the article with any further announcements from the carrier.

What are your thoughts about American Airlines’ 1969 STOL aircraft evaluation? Do you feel that the operator should have taken the Bréguet 941S on? Also, where do you think it would have flown the plane? Let us know what you think in the comment section.

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