By akademiotoelektronik, 30/10/2022
Northrop P -61 Black Widow - Definition and explanations
Introduction
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|---|---|---|---|
| < /b> | |||
| Manufacturer | Northrop | ||
| Role | Fighter (A fighter (also called a fighter) is a military aircraft designed to attack night...) | First flight (The first flight or maiden flight of an aircraft is the first opportunity for it to take...) | May 26, 1942 |
| Motorization | |||
| Motor (A motor is a device that transforms non-mechanical energy (wind, chemical,...) | Pratt & Whitney (Pratt & Whitney is the name of an American aircraft engine manufacturer whose production is...) R-2800-65 Double Wasp | ||
| Number (The notion of number in linguistics is covered in the article “Number...) | 2 | ||
| Type | Motor (A motor (from Latin mōtor: “the one who moves”) is a device...) in star (A star is a celestial object emitting light in an autonomous way, similar to a...) | ||
| Power (The word power is used in several fields with a particular meaning:) unitary | 2,250 hp | ||
| Wingspan (The wingspan is the distance between the ends of the wings. The term is valid for...) | 20.12 m | ||
| Length (The length of an object is the distance between its two extreme ends...) | 15.11 m | ||
| Height (Height has several meanings depending on the area covered.) | 4.47 m | ||
| Surface (A surface generally refers to the superficial layer of an object. The term a...) alar | 61.53 m² | ||
| Mass | |||
| Vacuum (Vacuum is commonly defined as the absence of matter in a spatial area.) | 10,637 kg | ||
| Armed | 13,471 kg | ||
| Maximum | 16,420 kg< /td> | ||
| Performance | |||
| Speed (We distinguish:) maximum | 589 km/h | ||
| Ceiling (By extension, a ceiling represents the maximum of something :) | 10,600 (operational ceiling) m | ||
| Ascent rate | 12.9 m/min | ||
| Range of action | 3,060 km | ||
| Weapons | |||
| Internal (In France, this name designates a doctor, a pharmacist or a dental surgeon, at the...) | 4 Hispano 20mm cannons (200 rounds per gun)4 Browning cal.50 (12.7mm) machine guns in turret (560 rounds per gun) | ||
| 8 500-pound bombs 6 5-inch (127 mm) rockets | |||
| edit |
The P-61 Black Widow is an American night fighter of the Second World War built by Northrop Corporation (Northrop Corporation was a major aircraft manufacturer in the United States.).
It is an aircraft of all-metal construction, twin-engine, twin-boom, high-wing monoplane, specifically designed for night penetration and fighter, used by the USAAF during World War II.
It was the first aircraft (An aircraft, according to the official definition of the International Civil Aviation Organization...) American specifically designed as a night fighter equipped with radar (Radar is a system that uses radio waves radio to detect and determine the...).
Origins
In the years before World War II, the Royal Air Force (The Royal Air Force (the Royal Air Force in English, most often abbreviated as...) and the Luftwaffe (The term Luftwaffe (literally, weapon of the air) indicates the various…) worked to define and to develop (Graphie) the theories and the doctrines of use of the night air weapon.
Implementing night air operations is a real challenge because of their complexity. the basis for the success of the P-61.
The Beginnings of the Black Widow
In August 1940, 16 months (The month (Lat. mensis “month”, and formerly Plur. “menses”) is a period of time... ) before the United States entered the war, the USAAC's corresponding officer in London (London (English: London - /?l?nd?n/) is the capital as well as the largest city.. .), Lieutenant-General Delos C. Emmons, was made aware of British research into RADAR (RAdio Detection And Ranging), a development that had been in progress since 1936 and which played a fundamental role in the defense of the British Isles against the Luftwaffe during the Battle of Britain (England is one of the four constituent nations of the United Kingdom....). General Emmons was informed of the existence of a new airborne interception radar, an autonomous device which could be installed in an aircraft and made it possible to operate in flight without resorting to ground stations. In September 1940, the Tizard mission approached the British research (Scientific research designates in the first place all the actions undertaken with a view...) of the British on numerous subjects, including radars, with a view (The view is the sense which makes it possible to observe and analyze the environment by reception and...) to produce devices in the United States.
At the same time, the British Purchasing Commission, in the process of evaluating American aircraft, declared its need (Needs are at the level of the interaction between the individual and the environment. It is... ) urgent need for a fast high-altitude interceptor (Altitude is the vertical elevation of a place or object above a level...) capable of engaging German night bombers attacking London. This plane had to be able to patrol all night above the city (A city is an urban unit (a "human settlement" for...) requiring de facto a minimum autonomy of eight hours (The hour is a unit of measurement :) and of course the carriage of the first airborne radars.The specified armament was arranged in "multiple turrets". of the RAF had demonstrated its ability to carry a radar for night hunting but was discarded in 1942 and the night versions of the De Havilland Mosquito (The De Havilland Mosquito (mosquito, as a reminder of the harassment function initially planned...) , excellent from the point of view of performance, needed to be reinforced from the point of view of their structure.
These specifications were distributed to all designers and aircraft manufacturers working for the British. Jack Northrop was among them and realized that the constraints of speed, altitude, fuel carrying capacity (A fuel is a fuel which feeds a thermal engine. This one transforms...) and on-board armament led to a large multi-engine aircraft.
General Emmons returned to the United States with the detailed specifications of the British night fighter and his report stated that such an aircraft could be produced by the aeronautical industry (Aeronautics includes science and technology aimed at to build and...) American. The Emmons commission developed the basic specifications and sent them, towards the end of 1940, to the Air Technical Service Command at Wrigth Field . Taking into account the two biggest constraints - the high mass (The term mass is used to designate two quantities attached to one...) of the on-board radar and the long autonomy (however standard for hunters of the time) of eight hours - the commission, of which Jack Northrop was a member, defined a twin-engine aircraft, of a size accordingly and recommended that these parameters be taken into account by the candidate projects.
In the meantime, Vladimir H. Pavlecka, head of research at Northrop, was present at other discussions at Wrigth Field. On October 21, 1940, Colonel Lawrence Craigie of the ATSC called Pavlecka to explain some USAAC specifications but told him, "Don't take notes, keep this in mind (Generally speaking, memory is the storing information. It's also remembering...) and get started” (Davis & Menard, 4). Craigie said nothing about the radar, then top secret, and described it to Pavlecka in these terms: "It is a device for locating enemy planes in the dark and has the ability to see and distinguish other planes ". The mission, Craigie continued, is to “intercept and destroy enemy aircraft in flight in darkness or low visibility (In meteorology, visibility is the distance at which it is possible to…)”.
Pavlecka met with Jack Northrop the next day and briefed him on the USAAC specifications. Northrop compared his notes with those of Pavlecka, found similarities between the USAAC specifications and those of the RAF and pooled the work done on the British request. A month had already passed (The past is first of all a concept linked to time: it is made up of the whole...) and the following week, Northrop responded to the USAAC's proposal.
On November 5, Northrop and Pavlecka met with Air Material Command officers at Wrigth Field to present their preliminary design. The Douglas XA-26 was the only competitor for this night fighter, it was Northrop's proposal that was selected: The Black Widow was born.
Preliminary studies
Following USAAC approval, Northrop began detailed design work for this device, which was to be the first designed specifically for night hunting. The result was the largest and most effective American night fighter of World War II.
Northrop's first study presented a long fuselage-nacelle flanked by two engine nacelles extending aft in beams intended to receive the vertical stabilizers and the horizontal stabilizer (Horizontal is an orientation parallel to the horizon, and perpendicular to the...), inspired by the P-38 Lightning.
The engines were Pratt & Whitney R2800-10 Double Wasp, 18-cylinder radial engines giving 2,000 horsepower (1.5MW) each.
The fuselage (The fuselage designates the envelope of an aircraft which generally receives the load...) housed a crew of 3 men, the radar and two turrets of four 12.7 mm Browning M2 heavy machine guns (caliber 0.50 inch) fitted with 36-inch "aviation (Aviation is an aerial activity defined by all stakeholders,...)" barrels. The turrets were located in the nose (The nose (from the Latin nasus) is in humans the median projection of the face located above ...) and at the rear of the fuselage.
The device rested on a landing gear (A train is a guided vehicle traveling on rails. A gear is composed of...) (The landing designates, in the etymological sense, the fact of reaching the earth closes....) tricycle (The tricycle is a three-wheeled cycle.) and full-span retractable high-lift flaps, flaps called "Zap flaps" after the engineer ("The basic craft of the engineering is to solve problems of nature...) Edward Zap working at Northrop.
The plane was large, as Northrop had expected. Much bigger and heavier than the twin-, tri-, four-engine or even larger bombers in production at the time.
A length of almost 14 meters (45 feet and 6 inches), a wingspan of more than 20 meters (66 feet) and a maximum payload mass (The payload represents what is actually...) projected in the order of 10 tons (22,600 pounds) were unprecedented characteristics for a hunter, unacceptable or even completely (Completely or completely automatic, or even by Anglicism completion or...) most specialists of the time.
Changes to the project (A project is an irreversible commitment of uncertain result, not reproducible a...)
Other configurations were studied before the detailed studies. Among these, a variant with a single set (In set theory, a set intuitively designates a collection...) rudder-rudder but it was discarded. Another variant provided for the positioning (We can define the positioning as a strategic choice which seeks to give to an offer...) of the turrets on the bottom and the top of the fuselage and the boarding of a second gunner.
At the end of November 1940, Jack Northrop returned to the twin-drift solution and the crew of 3 people. To achieve the high firepower specifications (Fire is the production of a flame by an exothermic chemical oxidation reaction...) of the USAAC, the ventral turret was abandoned in favor of four Hispano M2 20 mm mounted in the fenders. The P-61 then became one of the few American aircraft armed as standard in this way. The others were the P-38, the F4U-1C (a little-produced sub-version of the Corsair) and the A-36 Apache dive-bomber (an early version of the P-51 Mustang). Although a few F6F Hellcats and a few P-39s (renamed P-400s) taken over under Lend-Lease were also armed with four 20mm cannons, this was not standard equipment.
Northrop's Proposal 8A (NS-8A) was formally presented to Air Army Material Command at Wright Field on December 5, 1940. A few adjustments later, this proposal met with USAAC approval and Northrop received a order (Order: term used in many fields, generally it designates an order or a...) on December 17; a contract for two prototypes and two wind tunnel models, for a maximum amount of 1,367,000 dollars, followed on January 10, 1941.
By decision of the DoD (Department of Defense), the NS-8A proposal became the XP-61 project.
Characteristics
It carried a crew of three men: pilot, gunner and operator (The word operator is used in the domains:) radar. It was armed with four 20mm Hispano M2 cannons, two in each wing and four horizontally arranged 12.7mm Browning M2 machine guns (the central two slightly raised) in a remotely operated dorsal turret. The turret was controlled by a gyroscope firing computer (A gyroscope (from the Greek “which looks at the rotation”) is a device which exploits the...) General Electric (General Electric is an American conglomerate founded in 1892 by the merger of 'une...) GE2CFR12A3 and could be controlled by the gunner or by the radar operator, each having the fire controls and a collimator (A collimator is an optical device making it possible to obtain a beam of rays of light. ..) gyroscopic on their swivel seats.
The two Pratt & Whitney Double Wasp R2800-25S, each mounted approximately one-sixth of the wingspan, were supercharged by two-speed, two-stage mechanical superchargers. The turbochargers, although bringing a speed gain of 50 knots (92 km/h) and an increase in the operational ceiling of 10,000 feet (3,000 m) were not used for two reasons: They were not judged necessary and, moreover, they would have occupied a volume (The volume, in physical or mathematical sciences, is a quantity which measures the extension...) important all (The whole understood as a set of what exists is often interpreted as the world or...) by adding weight (Weight is the force of gravity, of gravitational and inertial origin, exerted by the...).
The main gear landing gear housings were located under the nacelles, just behind the engines. The main gear extended forward and folded aft, with the guide compasses pointing forward. Each wheel (The wheel is an organ or mechanical part of circular shape rotating around an axis passing through...) was turned towards the inside of the leg of the landing gear. The doors of each main landing gear were in two pieces of equal size, with a longitudinal closing joint, and hinged on the outer edges of the landing gear housings.
Each engine cover and nacelle extends aft into a beam that ends in a wide centerboard and a triangular-shaped steering flap (In Euclidean geometry, a triangle is a plane figure, formed by three points ...) rectangle (In geometry, a rectangle is a quadrilateral whose four angles are ...), the leading edge of the fin presenting an angle (In geometry, the general notion of angle comes in several concepts...) of 37 degrees from the vertical (The vertical is a straight line parallel to the direction of gravity, given in particular by the...). The horizontal stabilizer is arranged between the two fins and has a rope, rudder (A rudder is a mobile surface acting in the air or in the water used to pilot a...) of depth included, approximately equal to three- quarters of the chord of the wing measured at the root. The elevator represents approximately one third of the width (The width of an object represents its dimension perpendicular to its length, i.e....) of the fixed plane-rudder assembly, seen from above, the elevator has a trapezoidal shape. The horizontal stabilizer and elevator are assembled to be very aerodynamic.
The engine nacelles are located at the ends of the central wing box, which has a positive dihedral of 4 degrees and is extended by the rest of the wing which has a dihedral of 2 degrees. The leading edge of the wing is straight and perpendicular (In plane geometry, we say that two straight lines are perpendicular when they intersect in...) to the axis of the plane. The trailing edge is straight and parallel to the leading edge in relation to the central box then has a 15 degree deflection after the nacelle. The engine air intakes are located on the leading edges a few tens of centimeters on either side of the engine nacelles. The shape of these air intakes is similar to that of the F4U Corsair (rectangular with semi-circular ends) with, inside, multiple blades to channel the flow (The word flow (from the Latin fluxus, flow) designates in general a set of elements...) of air.
There were no fins; in addition to the "Zap flaps", retractable flaps over the entire wingspan, the control (The word control can have several meanings. It can be used as a synonym for examination, of...) of the aircraft in roll was entrusted to lift destroyers approximately 3 meters (10 feet) long and 15 cm (6 inches) wide each. They are located outside each of the engine nacelles. Their operation is as follows: The lift destructor or spoileron located in the wing turns towards the upper surface of the wing, which modifies airflow and decreases lift by breaking Bernoulli's Principle.
The main fuselage, centered on the plane's axis of symmetry, from the tip of the nose to the tip of the terminal cone, has a length of approximately 5/6 of the length of a wing (from l root at the marginal edge). The nose houses a General Electric SCR-720A radar, an improved version of the Signal radar ( General terms A signal is a simplified and generally coded message. There are...) SCR-268 body. Just behind the radar is the forward crew compartment: pilot and gunner, raised about 15 cm (6 inches) above the pilot. The canopy, of the "gardener's greenhouse" type, with multiple uprights, comprised two marked levels; one for the pilot and the other for the gunner shifted in height and rearward. Combined with the roughly flat upper surface of the nose, this two-step canopy gave the front of the fuselage a low-rise three-step profile. On the XP-61, the front canopy included parts in thermoformed Plexiglas in front of the pilot and the gunner, and parts with uprights for the top and the sides of the cockpit (The cockpit (but also cockpit, cockpit, cell or cockpit) of a...).
Beneath the forward crew compartment is the nose landing gear, this was also the access to the aircraft for the pilot and gunner.
The front lander leg retracts backwards, against a specially shaped panel which, during flight , closed the cockpit floor; the lander had no room to retract if this panel was not closed. The steering compass was facing forward. The front caster was centered with the strut on the left. The front wheel had a diameter (In a circle or a sphere, the diameter is a line segment passing through the center...) approximately equal to 2/3 of the diameter of the main wheels. There were two doors for the nose gear, symmetrical, the longitudinal closing joint, the doors hinged on the outer edges of the gear housing.
The central part of the fuselage housed, among other things, the main wing spar (The spar is a basic element of a structure. This term appears in different fields...), the fuel tanks, the systems power supply and their control systems as well as the flight control cables, the engine and propeller pitch controls, the radio (to be deleted) and the IFF, but above all the frame of the dorsal turret as well as its rotation and elevation control; the ammunition magazines for the four 12.7 mm (0.50 in) caliber Browning M2 heavy machine guns, the GE2CFR12A3 gyroscopic fire control computer, as well as the links to the gunner's and operator's fire consoles radar, respectively forwards and backwards.
At the rear of the fuselage was the position of the radar operator, it was accessed by a small hatch equipped with a ladder, located under the aircraft. The controls and display screens for the SCR-720 radar were located in the rear compartment, isolated from the rest of the aircraft. Radio, intercom and remote turret command and control systems also took place there. The aft compartment canopy followed the general line of the forward canopy, except that it included only one rounded rung (A rounding of a number is an approximate value of that number obtained, from its... ). The rear of the fuselage consisted of a tapered Plexiglas canopy. Connecting to the fuselage of rectangular section, this terminal cone had a slightly larger section seen from the side than seen from above, which gave, seen in perspective, the impression of a rounded "blade".
The cross-section of the fuselage was rectangular, oriented vertically, over most of it. The tip of the nose, very round, was quickly connected to the rectangular section of the fuselage; then the transverse section of the fuselage rounded frankly under the housing of the landing gear and the cockpit. The height increased with each rung of the forward canopy, the second rung being level with the top of the fuselage (not counting the turret). Aft of the forward crew compartment, the cross-section rises sharply downwards to a point, located between the aft of the forward compartment and the front of the aft compartment, from which the rounded shape under the fuselage begins to shrink.
The cross-section of the nacelles was mostly circular, growing and shrinking from the cowlings, fenders, and undercarriage housings to the rear beams and tail fins. A bulge on the top of the wings maintained a circular cross-section at the wing-nacelle intersections. The cross-section then took on a slightly egg-shaped shape in line with the gear housings, wider at the bottom but still rounded. An oblong bulge on the doors of the main gear made it possible to house the main wheel when the gear was retracted.
The marginal edges, the wing-nacelle joints, the edges of the stabilizers and the control surfaces (except the horizontal stabilizer and the elevator) were very well rounded and streamlined, cleanly connected. the plane had very few angles or sharp edges; aerodynamically speaking, the design of this aircraft was very clean, its lines flowing.
Development of the XP-61
In March 1941, the Army/Navy standardization committee decided to standardize the use of vertical carburettors in all US military sectors. The XP-61 project, designed for inverted carburetors, required at least two additional months to redesign the engine nacelles to make them compatible with this decision. Later, this decision was canceled by the same committee (the situation (In geography, the situation is a spatial concept allowing the relative location of a...) delicate of the XP-61 project had something to do with it) , thus avoiding a possible delay in the development of the XP-61.
The Air Corps visited Northrop on April 2, 1941 to inspect the XP-61 layout mock-up; several modifications were requested following the inspection. The most important was the change of position of the 4 Hispano 20 mm guns from the outer portions of the wings (beyond the engine nacelles) to the belly of the central fuselage where they were grouped just behind the nose gear housing. With the guns quite close to each other, centered with respect to the axis of the plane, superimposed in pairs, the upper guns slightly overhanging, this arrangement makes it possible to eliminate the problems due to convergence (The term of convergence is used in many areas :) weapons.
Weapons convergence is mandatory for aircraft with wing-mounted weapons. Convergence consists of crossing the fire of the different weapons with the axis of the aircraft, at one or more points, at a given distance and elevation, in order to avoid the "safety zone" that we would have at the front of the plane if these guns each fired straight ahead. Projectiles fired past the focal point scatter behind the target and miss by far. Those fired at an objective below, either pass around (Autour is the name that the avian nomenclature in French language (update) gives...), or do not hit the target in a sufficiently concentrated way to inflict maximum damage . In both cases, the effective range of guns is limited to a very narrow area around a given distance (In information technology (IT), a datum is a basic description, often...), which brings additional problems for the calculation of the deflection when firing at a moving target.
With no convergence, aiming is faster and easier and the grouped guns created a true stream of 20mm projectiles. Removing cannons and ammunition from the wings also helped to clean up the aerodynamics of the airfoils and increase the internal fuel capacity of the aircraft. 2,044 to 2,441 liters (540 to 645 gallons).
Other modifications were to provide attachment points under the wing for external drop tanks, flame arresters on the exhausts, and to review the layout of some radio equipment. While all of these changes were beneficial, especially the new gun layout, they resulted in an additional month of re-design, when the XP-61 was already behind schedule.
During the summer of 1941, it was realized that the planned dorsal turret was really very difficult to install, the General Electric ring turret was replaced by a base system like the dorsal turrets of the B17, B-24, B25 , A-20 and other bombers. Following these modifications, the turret itself was not available, because operational aircraft – the B-29s in this case – had priority over experimental aircraft for deliveries of this component (A component is a set of fabrics contributing to the realization of a function...) in great demand. For the flight tests, a dummy turret was installed.
During February 1942, Curtiss announced to Northrop that the planned propellers (model C5424-A10, four-bladed, with automatic pitch adjustment (Automatics is part of the engineering sciences. This discipline deals with the...) and feathering) for the prototype would not be ready for taxiing and first flights. Hamilton Standard propellers were used instead, pending Curtiss availability.
The weight of the XP-61 increased during the construction of the prototype to 10,156 kg (22,392 lb) empty and 13,459 kg (29,673 lb) at takeoff (Takeoff is the transient phase during which an aircraft passes state...). The engines were R-2900-25S Pratt & Whitney Double Wasp, driving Curtiss C5425-A10 four-bladed propellers 3.70 m (12 ft 2 in) in diameter in the direction (SENS (Strategies for Engineered Negligible Senescence) is a scientific project which aims to... hands of a watch seen from the front. Radio equipment included two main SCR-522A radios and three other radios: SCR-695A, AN/APG-1 and AN/APG-2. The turret fire control was the same as on the B-29, General Electric GE2CFR12A3.
The SCR-720 radar
The production model of the SCR-720 featured a radar transceiver in the nose of the aircraft; in the "air intercept" mode it had a range of 5 miles. The device could also function as an on-board radio beacon, a guidance system, a navigation aid (Navigation is the science and all the techniques that make it possible to:) or in collaboration with IFF transponders. The radar operator of the XP-61 located the targets on his screen then informed, via the intercom, the pilot with the course and trajectory corrections (The trajectory is the line described by any point of a moving object, and...) necessary. Once the target had been approached, the pilot used a smaller screen, integrated into the dashboard (The dashboard is the element which indicates to the driver of a vehicle (car, boat), etc.), to s approach closer.
The remote-controlled turret
The rotating turret of the XP-61 could be maneuvered by any of the three crewmen or could be locked forward to add its firepower to that four 20mm guns. The radar operator could rotate the turret rearward to engage targets coming from the rear of the aircraft. Capable of 360 degrees in rotation and 90 degrees in elevation, it covered the entire half sphere (In mathematics, and more precisely in Euclidean geometry, one...) above the XP-61.
Operational changes
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