This 1941 training film, Principles of Operation: What is a Brake? (TF 1-162), is part of the Airplane Hydraulic Brakes training films and covers the basic principles of braking, looks at the two braking systems on planes (independent system for lighter aircraft and integral system for heavier planes), and reviews the mechanical operations of the hydraulic brake. The film opens with a person flipping through a book. Basic animation shows a large plane (possibly a rendering of a Curtiss-Wright C-46 Commando) as it is landing, explaining how motion energy is changed to heat energy in the brake. The animation gives a scenario of a 36,000-pound plane flying at 90 mph (03:05) and what kind of energy is needed for braking. What appears to be a C-46 Commando lands on a grassy field (05:01). An illustration is used to show the different braking systems inside a plane (integral and independent systems). Animation is then used to show how the various components of a hydraulic braking system work: the film covers the pistons and cylinders, actuating cylinder, compression springs, and brake drum. The film shows footage of a large truck braking (10:36), as well as a large airplane—both use a power brake system. It shows a hydraulic braking system’s accumulator tank (10:57), which stores the system’s pressure. The film shows an illustration of the pressure control valve system, and reviews how the hydraulic fluid moves through the braking system, moving fluid from the reservoir to the brake. The film then shows several shots of actual braking systems on airplane wheels (15:38), featuring a debooster to reduce the pressure going to the smaller brakes on the wheels. The film concludes with a brief recap of the independent and integral braking systems.
A hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing glycol ethers or diethylene glycol, to transfer pressure from the controlling mechanism to the braking mechanism.
Malcolm Loughead (who later changed the spelling of his name to Lockheed) invented hydraulic brakes, which he would go on to patent in 1917. "Lockheed" is a common term for brake fluid in France. Fred Duesenberg used Lockheed hydraulic brakes on his 1914 racing cars and his car company, Deusenberg, was the first to use the technology on a passenger car, in 1921. Knox Motors Company of Springfield, MA was equipping its tractors with hydraulic brakes, beginning in 1915. The technology was carried forward in automotive use and eventually led to the introduction of the self-energizing hydraulic drum brake system (Edward Bishop Boughton, London England, June 28, 1927) which is still in use today.
The Martin B-26 Marauder is an American World War II twin-engined medium bomber built by the Glenn L. Martin Company in Middle River, Maryland (just east of Baltimore) from 1941 to 1945. First used in the Pacific Theater in early 1942, it was also used in the Mediterranean Theater and in Western Europe.
After entering service with the United States Army aviation units, the aircraft received the reputation of a "Widowmaker" due to the early models' high accident rate during takeoffs and landings. The Marauder had to be flown at exact airspeeds, particularly on final runway approach and when one engine was out. The 150 mph (241 km/h) speed on short final runway approach was intimidating to pilots who were used to much slower speeds, and whenever they slowed down to speeds below what the manual stated, the aircraft would stall and crash.
The B-26 became a safer aircraft once crews were re-trained, and after aerodynamics modifications (an increase of wingspan and wing angle-of-incidence to give better takeoff performance, and a larger vertical stabilizer and rudder). The Marauder ended World War II with the lowest loss rate of any USAAF bomber.
A total of 5,288 were produced between February 1941 and March 1945; 522 of these were flown by the Royal Air Force and the South African Air Force. By the time the United States Air Force was created as an independent military service separate from the United States Army in 1947, all Martin B-26s had been retired from U.S. service. The Douglas A-26 Invader then assumed the "B-26" designation — before officially returning to the earlier "A for Attack" designation in May 1966.
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October 30, 2020 Subject:
Not exclusively about the Martin B-26
The title should remove the reference to the Martin B-26 Marauder. This film is about aircraft hydraulic brakes in general and the B-26 is one example of its use. The B-26 in this film has an appearance at 5:00 for about 15 seconds. Other aircraft shown are the C-46, B-17, A-20, etc. The biography of the B-26 in the film's description is probably a misplaced copy and paste.