Daily Archives: June 25, 2021

25 June 1946

Northrop XB-35 taking of at Northrop Field, Hawthorne, California. (U.S. Air Force)
Northrop XB-35 taking off at Northrop Field, Hawthorne, California. (U.S. Air Force)
Max R. Stanley (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers))

25 June 1946: Northrop Aircraft, Inc., experimental test pilot Max R. Stanley,  flight test engineer Dale Schroeder and Orva H Douglas, Jr., flight engineer, made the first flight of the Northrop XB-35 “Flying Wing,” serial number 42-13603. They took off from the factory’s airfield at Hawthorne, California, and flew the prototype bomber to Muroc Army Air Field (now, Edwards Air Force Base). The initial flight lasted 55 minutes.

The Los Angeles Times reported:

On June 25, 1946, Stanley piloted the first Flying Wing, the B-35, which was a four-engine 172-foot-long, boomerang-shaped craft, from Northrop’s Hawthorne Airport to what was then the Muroc Army airfield east of Palmdale.

Emerging from the cockpit after the 55-minute flight, Stanley told The Times: “She handled beautifully.”

But taxiing along the rabbit-infested Hawthorne runway, he had had momentary doubts, he conceded 50 years later: “I looked out and I was not gaining speed on this rabbit. I thought, either something’s wrong or that’s one hell of a fast rabbit.”

Flight test crew of Northrop's XB-35 at Northrop Field, Hawthorne, California, 1946.
The flight test crew of the Northrop XB-35 at Northrop Field, Hawthorne, California, 1946. Left to right, Dale Schroeder, flight test engineer; Orva H Douglas, Jr., flight engineer; and Max Stanley, test pilot. (Unattributed)

The XB-35 was designed as an aerodynamically efficient heavy bomber. It had a very unusual configuration for an aircraft of that time. There was no fuselage or tail control surfaces. The crew compartment, engines, fuel, landing gear and armament was contained within the wing. It was 53 feet, 1 inch (16.180 meters) long, with a wingspan of 172 feet (52.426 meters) and overall height of 20 feet, 1 inch (6.121 meters). The prototype weighed 89,560 pounds (40,624 kilograms) empty, with a gross weight of 180,000 pounds (81,647 kilograms).

The Wing defined the airplane. It had an aspect ratio of 7.4:1. The wing’s root chord was 37 feet, 6 inches (11.430 meters). The wing was 7 feet, 1.5 inches (2.172 meters) thick at the root. The tip chord was 9 feet, 4 inches (2.844 meters). There was 0° angle of incidence at the root, with -4° of twist, and 0° 53′ dihedral. The leading edge was swept aft 26° 57′ 48″, and the trailing edge, 10° 15′ 22″. The wing’s total area was 4,000 square feet (371.6 square meters).

This view of the Northrop XB-35 Flying W 42-13603 on the ramp at Muroc Air Force Base shows the pusher arrangement of four-bladed contra-rotating propellers. In the background, a turbojet-powered YB-49 is in a right bank.. (U,S. Air Force)
This view of the first prototype Northrop XB-35, 42-13603, the “Flying Wing,” on the ramp at Muroc Air Force Base shows the pusher arrangement of four-bladed contra-rotating propellers. In the background, a turbojet-powered Northrop YB-49 is in a steep bank. (U.S. Air Force)

The XB-35 was powered by four air-cooled, supercharged and turbocharged 4,362.49 cubic-inch-displacement (71.49 liter) Pratt & Whitney Wasp Major TSB1P-RGD (R-4360-17 or  -21) four-row 28-cylinder radial engines with a compression ratio of 7:1. The R-4360-17 was rated at 2,500 horsepower at 2,550 r.p.m at 40,000 feet (12,192 meters), and 3,000 horsepower at 2,700 r.p.m., for takeoff. It could maintain the takeoff rating to an altitude of 40,000 feet (12,192 meters) for Military Power. The engines were mounted completely inside the wing and were connected to a remote propeller drive unit by drive shafts. The engines were direct drive, while the propeller gear boxes had a 0.381:1 reduction ratio. The R-4360-17 was 5 feet, 7.00 inches (1.702 meters) long, 4 feet, 4.50 inches (1.334 meters) in diameter, and weighed 3,306 pounds (1,499.6 kilograms).

Northrop XB-35 42-13603 in flight with early contra-rotating propellers. (U.S. Air Force)

The propellers were dual three-bladed contra-rotating assemblies located in pusher configuration at the wing’s trailing edge. (These were quickly changed to four-bladed propellers, which were smoother in operation and more efficient.)

Northrop XB-35 42-13603. (U.S. Air Force)
Northrop XB-35 42-13603. (U.S. Air Force)

The XB-35 had a cruising speed of 183 miles per hour (295 kilometers per hour) at 39,700 feet (12,100 meters) and maximum speed was 391 miles per hour (629 kilometers per hour) at 35,000 feet (10,668 meters). With a crew of nine, and another six relief crewmembers, the bomber had a range of 8,150 miles (13,116 kilometers).

The production Northrop B-35 would have been armed with twenty .50-caliber machine guns for defense and a maximum bomb load of 51,200 pounds (23,223 kilograms).

The XB-35 was plagued by unresolved problems with the propeller gear boxes which eventually forced Jack Northrop to ground the aircraft until the engine and propeller manufacturers could come up with a solution, which was to change from piston to turbojet engines. That version became the YB-49. Because of the continuing problems, though, 42-13603 was grounded after only 19 flights, and with its sister ship, XB-35 42-38323, was scrapped in August 1949.

Northrop XB-35 in flight. (U.S. Air Force)
A Northrop XB-35 in flight. (U.S. Air Force)

© 2018, Bryan R. Swopes

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25 June 1937

25 June 1937: Leg 25. After flying from Bandoeng to Soerabaya the previous day, a problem with Amelia Earhart’s Lockheed Electra 10E Special, NR16020, could not be repaired there, forcing her to return to Bandoeng.

“In the air, and afterward, we found that our mechanical troubles had not been cured. Certain further adjustments of faulty long-distance flying instruments were necessary, and so I had to do one of the most difficult things I had ever done in aviation. Instead of keeping on I turned back the next day to Bandoeng. With good weather ahead, the Electra herself working perfectly, the pilot and navigator eager to go, it was especially hard to have to be “sensible.” However, lack of essential instruments in working order would increase unduly the hazards ahead. At Bandoeng were the admirable Dutch technicians and equipment, and wisdom directed we should return for their friendly succor. So again we imposed ourselves upon these good people to whom I shall be grateful always for their generosity and fine spirit. A particular niche in my memory is occupied by Colonel L.H.V. Oyen, Commander of the Air Force, H.A. Vreeburg, chief engineer, and so many K.N.I.L.M. personnel to whom I would like again to say ‘Thank you’.”

— Amelia Earhart

Amelia Earhart’s Lockheed Electra 10E Special, NR16020, at Bandoeng, Java, Dutch East Indies, June 1937. (Purdue University Libraries, Archives and Special Collections)
Bandoeng to Soerabaya, 352.26 miles (566.91 kilometers). (Google Maps)

© 2018, Bryan R. Swopes

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25 June 1919

First flight of the Junkers F.13 at Dessau, Germany, 25 June 1919. (Junkers)

25 June 1919: Junkers Flugzeugwerke Aktiengesellschaft test pilot Emil Monz made the first flight of the Junkers F.13 at Dessau, Saxony-Anhalt, Germany. It was the first airplane to be built of all-metal construction specifically for commercial passenger service. The the first flyable prototype, constructor’s number (c/n) 533, carried the identification mark D 183. Professor Junkers had named the airplane Herta in honor of his oldest daughter.¹

Up to this time, airplanes had been primarily constructed of wood. Wood is susceptible to changes in dimension because of temperature and humidity, and it can warp over time. This effects the flight characteristics of the aircraft. Wood is also vulnerable to termites.

By building the airplane of metal, a much more rigid structure was created. The airplane’s flight characteristics did not change over time. Also, because metal is so much stronger than wood, an all-metal airplane could be significantly lighter than one built of wood.

The cockpit of the Junkers F.13 accommodated two pilots. (Junkers)
The cockpit of the Junkers F.13 accommodated a crew of two. (Junkers)
Otto Reuter (Junkers)

Designed by Chief Engineer Otto Reuter, the F.13 was a single-engine, low-wing monoplane (tiefdecker) with a corrugated duralumin skin over a duralumin structure. It had a flight crew of two and four passengers could be carried in a comfortable enclosed cabin of the same size as automobiles of the time. The single wing was cantilevered and, unusually for the time, used no braces or support wires.

The prototype had a wingspan of 14.47 meters (47 feet, 5.7 inches). The wingspan was increased to 14.82 meters (48 feet, 7.5 inches) in production airplanes. The airplane was 9.59 meters (31 feet, 5.6 inches) long and 4.10 meters (13 feet, 5.4 inches) high. It had a maximum takeoff weight of 1,800 kilograms (3,968 pounds).

The first of three prototypes to fly, Junkers F.13 D 183, Herta, photographed on 19 August 1919. (Junkers)

The first F.13 was powered by a water-cooled, normally-aspirated 14.778 liter (901.81 cubic inch) Daimler Motoren Gesellschaft Mercedes D.IIIa vertical inline six-cylinder engine. This was a single overhead cam right-hand tractor direct-drive engine. It used two valves per cylinder and a compression ratio of 4.64:1. It produced 174 horsepower at 1,400 r.p.m., and drove a two-bladed, fixed-pitch laminated wood propeller. The D.IIIa weighed 660.0 pounds (299.4 kilograms), including the propeller hub and exhaust manifold.

Production airplanes used BMW and Junkers engines.

The F.13 had a maximum speed of 170 kilometers per hour (106 miles per hour).

The passenger compartment of the Junkers F.13 seated for passengers. (Junkers)
The passenger compartment of the Junkers F.13 seated for passengers. (Junkers)

In production from 1919 to 1932, a total of 332 Junkers F.13s were built. Some remained in service in the late 1930s.

In 1920, D 183 was confiscated by the Inter-Allied Control Commission. Later, the F.13 flew for Lufthansa. The registration mark was changed to D 1 and it was named Nachtigall (Nightingale).

Junkers F.13 D 1, Nachtigall, in Luft Hansa livery at Berlin-Templehoff.
Emil Monz

Emil Monz was born 9 June 1893, in Stuttgart, Germany. He was the son of Karl and Mathilde Monz. He married Fräulein Maline Georgine Erhardt, 24 January 1915, at Weingarten u. Wilhelmsdorf, Württrmberg, Deutschland.

During World War I, Monz was a reconnaissance pilot for the German Empire.

On 13 September 1919, Monz flew the second F.13, with seven passengers on board, to an altitude of 6,750 meters (22,146 feet). This was an unofficial world record.

Emil Monz died 18 February 1921 when the Junkers F.13 that he was flying, D 128, crashed in a snowstorm enroute to Stuttgart.

¹ While it is believed that Professor Junkers named the prototypes after his daughters Herta and Annelise, sources vary over which name was applied to which aircraft. The confusion may be a result of the serial numbers. The first F.13 to fly was c/n 533, while the second had an earlier number, c/n 531.

© 2018, Bryan R. Swopes

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