Lockheed SR-71 is one of the most famous reconnaissance aircraft and at the same time one of the most unknown. Blackbird is the brainchild of renowned aircraft designer Clarence Johnson, Head of Advanced Development (ADP), Lockheed. Designed in the late 1950s, the Blackbird looks futuristic even today, despite the fact that it was created not using high-speed computers, but on an ordinary kulman.
Design
SR-71 Blackbird is built according to the "tailless" scheme with a triangular wing and a two-tail tail. The design is traditional - with stringers, frames and working skin. Carefully "licked" forms serve not only aerodynamics. Stealth Aircraft created using Stealth technology are considered to be an invention of the last decade, but this technology is also largely embodied in the Blackbird design. Rounded contours and smooth mating surfaces make the aircraft less visible to radars.
The strategic supersonic reconnaissance has almost no flat surfaces. The exception is rather large keels, but they are tilted inward, which reduces their effective dispersion area. In addition, radar absorbing materials in the form of triangular inserts of honeycomb plastic structures are used in the design of the leading and trailing edges of the wing. Due to this form of insertion, the radio waves are reflected inside the triangle until they are completely attenuated. To top it off, operating radio equipment distorts the signal reflected from the aircraft, confusing the air defense radar operators.
During a long flight at supersonic speeds, the aircraft undergoes strong and prolonged heating. Therefore, the Blackbird design is almost 93% composed of the high-strength and heat-resistant titanium alloy Beta B-120.
Fuselage
Given that at speed smooth wing paneling panels warp and swell from heating, these elements are made corrugated. Longitudinal grooves not only work as stiffeners, but also increase the area of āāheat dissipation, almost without increasing resistance.
Many modern American combat aircraft have inflations on the root of the wing, but at the Blackbird they occupy the entire length of the fuselage, because of which its cross-section becomes almost diamond-shaped. These influxes play a dual role: they create a very significant lifting force, which halves the bending moment on the long fuselage, and at the same time serves to accommodate fuel and equipment. In addition, they work on aerodynamics, reducing drag.
The crew is housed in cockpits located āin tandemā with individual lanterns opening back. The glazing of the Lockheed SR-71 model cabs is made of special glass that does not allow hard ultraviolet radiation to pass at high altitudes. The cabins are equipped with air conditioning, the crew flies in altitude-compensating suits.
Wing
The wing has a twist of the outer consoles, reducing bending and torque on it. Purge the model in the wind tunnel showed that there is no need for flaps or slats - a large wing on landing creates a powerful air cushion, providing a very soft landing with almost no pilot intervention. Widely spaced engine nacelles are carefully smoothed and have noticeable influxes from the outside at the junction with the leading edge of the wing.
Tail
The vertical tail is made all-turning. Such keels are 2.5 times more effective than traditional rudders and require smaller deflection angles, which reduces drag. The maximum deflection angle of the Blackbird keels at a speed of up to Mach 0.5 is 20 Ā°, at a higher speed it automatically decreases to 10 Ā°. Keels are tilted inward by 15 Ā°, which positively affects stability and controllability. For example, the supersonic aircraft SR-71 is not afraid of side wind up to 18 m / s. Combined ailerons and elevators occupy the entire trailing edge of the wing.
Motors
Blackbird has two particularly powerful engines such as the Pratt & Whitney JT11D-20B turbojet engine (another designation is J58) with a thrust of 144.56 kN each. The secret of Blackbirdās great range lies in them: at Mach 3, the motors essentially turn into straight-through engines: 58% of the thrust comes from the air intake, 25% from the nozzle, and only 17% from the engine itself. The air intakes of the Black Bird aircraft were designed to provide a significant portion of the total thrust. The cones are made adjustable to hold the shock wave in the air intake.
When constructing the J58 engine, specialists from Pratt & Whitney faced serious difficulties: the temperature in the air intake reached 380 Ā° C, in the fuel injectors - 160 Ā° C, in the afterburner - 280 Ā° C, and the oil in the engine - 485 Ā° C. Therefore, in the design of J58, in addition to titanium, particularly heat-resistant nickel alloys Hastelloy-X and Rene-41 were used. Due to such intense thermal conditions, the engines were completely disassembled and checked every 200 hours of operation.
Chassis
The Blackbird chassis is a three-leg with a nose wheel. The nasal support with two wheels retracts forward, the main ones toward the center. The landing gear is cleaned immediately after taking off the ground, as the Lockheed SR-71 quickly accelerates to the maximum permitted flight speed with the landing gear (555 km / h). The main supports have three wheels on one axis to reduce ground pressure and at the same time save the internal volume of the fuselage.
Tires are made not of rubber, but of a special heat-resistant material, and in order to maintain constant pressure in all flight modes, as well as to avoid oxidation, they are filled not with air but with nitrogen. They have a smooth tread and are coated with silver paint to reduce heat. The wells of the chassis are surrounded by fuel tanks - fuel plays the role of a coolant.
Brake system
The reconnaissance aircraft is equipped with a single brake parachute with a diameter of 12 m, released with the help of a squib immediately after touching the runway at a speed of 280-330 km / h. The parachute is made of a special heat-resistant material and is made mesh so that it does not burst with a high-speed pressure. It detaches when the aircraft speed drops to 110 km / h so that the halyard does not get entangled in keels.
Equipment
US Aviation uses the most advanced telemetry and control systems. The Blackbird is equipped with an eight-channel stability enhancement system (SPU), which compensates for the ābuilt-inā instability of the aircraft (it is caused by uneven heating during cruise flight). The system works on all three coordinate axes and is duplicated three times.
At speeds of Mach 3 and above, too energetic actions by the rudders can lead to a sharp change in the position of the aircraft in space, and this is fraught with its destruction. On the other hand, at the height at which the SR-71 Blackbird operates, the air density is less than 2% of its density at sea level, so a large deviation of the rudders is required.
SPU was created by Honeywell and turned out to be one of the most reliable in the entire aircraft: its average time between failures was about 130,000 hours. If the system nevertheless breaks down, it is difficult, but possible to control the aircraft in cruise mode.
Honeywell also developed a flight data processing computer that corrects for distortions that occur in flight at supersonic speeds. Due to the strong rarefaction of air at high altitude, conventional devices with data input from LDPE tubes were unreliable. The exact values āāof vertical speed, altitude and speed in Mach numbers were displayed from the computer on three digital displays in the pilot's cabin.
Fuel system
Strong and prolonged heating of the Lockheed SR-71 aircraft during cruising flight required the development of new fuels and lubricants, sealants, hydraulic mixtures, insulation materials, etc. For example, the fuel used in the Blackbird JP-7 brand has such a high temperature flashes that it was necessary to set fire to it with a special reagent - triethylborane (TEB). Due to this, it is used as a coolant for cooling crew cabins and the most sensitive to overheating units, especially the chassis. But as the fuel was developed, uneven heating of the fuselage began, which caused the deformation of its influx.
In a special tank on the plane there is a stock of triethylborane for starting engines in the air and turning on afterburners. The strategic scout is equipped with six fuel tanks that hold 46,000 liters of fuel. The tanks are integral, their upper and lower walls are formed by the skin, and due to the systematic expansion and contraction of the airframe during heating and cooling, they crack. Every 200 hours of flight, they are sealed, but still the tanks are flowing, and under the planes parked in the parking lot, whole pools of fuel accumulate. Since the JP-7 fuel is non-volatile, there is practically no danger of fire, but during cruising the tank walls heat up to 280 Ā° C, so even JP-7 fuel with its high flash point can cause an explosion. Therefore, in flight, the tanks are filled with nitrogen.
Specifications
Model SR-71 has the following specifications:
- Length - 32.7 m.
- Wingspan: 16.9 m.
- Height - 5.6 m.
- Take-off weight - up to 78 tons.
- Flight range - 4800-5200 km.
- The maximum speed is 2125 km / h at an altitude of 9,000 m and 3220 km / h at an altitude of 24,000 m.
Armament
Of the three Blackbird variants, only the YF-12A supersonic interceptor had weapons. It consisted of four Hughes GAR-9 (AIM-47A) Super-Falcon air-to-air missiles, aimed at a target using the AN / ASG-18A radar. Reconnaissance versions did not have weapons, although the option to install a dropable container of nuclear bombs on the SR-71 was being worked out, in the manner of the Convair B-58 Hustlen bomber.
Elusive
Military aircraft play an important role in modern warfare strategies. Despite the impressive grouping of tracking satellites among the leading powers, aviation is still important in conducting reconnaissance missions. Perhaps, it is Blackbird that is the most legendary reconnaissance aircraft.
Having been in all the "hot spots" of the world, the SR-71 has never been shot down. In 1972, in a military journal, Ramparts quoted the words of a former Air Force sergeant who worked for the National Security Agency: "It's impossible to shoot down the SR-71." The sergeant cited cases when the Chinese tried to do this, but the pilots of the MiG-21 interceptors raised by the alarm had only to wonder where the intruder had evaporated. According to him, the Blackbirds also flew over Soviet territory, and NSA listening stations along the borders of the USSR recorded the reaction of Soviet air defense. Moreover, the former sergeant said that US electronic intelligence equipment allowed them to monitor the flights of almost all Soviet military aircraft and even determine who is currently piloting a particular vehicle. And in this is a considerable merit of the "seventy-first."
Throughout the 70s, American planes flew over North Korea, China, Cuba, along the borders of the USSR. At the same time, there were meetings with the fastest Soviet interceptor of the time - the MiG-25P, and they ended, according to the Americans, not in favor of the latter. Attempts were also unsuccessful to get the elusive āguestā with the latest anti-aircraft missiles at that time.
Lockheed A-12
The name "Blackbird" is most often associated with the strategic scout SR-71. However, behind this name there are two more not so well-known cars: A-12 and YF-12A.
The history of the appearance of these designations is quite curious. It is known that US military aircraft have a clear classification. The abbreviation YF denoted the class of fighters, in fact, YF-12A and was an experimental fighter. The letter A (attack) was assigned to the attack aircraft, but the A-12 is clearly not similar to the attack aircraft. This was done to confuse USSR intelligence after a grand international scandal involving the downing of an American spy plane over Sverdlovsk (Yekaterinburg) . Then President Eisenhower promised Khrushchev not to use reconnaissance aircraft in the sky over the Soviet Union, but the Lockheed project was precisely focused on these operations. Formally, it was considered "civilian", as it belonged to the CIA - not an army organization.
By January 1962, the prototype A-12 was ready for testing. After the first flights, it turned out that the design has many flaws. The power plant was particularly annoying, requiring a long and laborious refinement of the air intakes. Despite this, the A-12 was launched into the series - the CIA urgently needed a high-speed reconnaissance to replace the outdated U-2. 14 copies were issued.
Design features
Lockheed A-12 remained essentially experimental - it had many shortcomings that could only be eliminated by finalizing the design. Perhaps the main one is a huge load on the pilot, who, in addition to controlling the aircraft, which in itself was a difficult matter, had to cope with numerous reconnaissance equipment.
The external signs of the A-12 were a very pointed nose with straight edges of the front parts of the fuselage flows and a short tip of the latter. The main difference from subsequent modifications of the Blackbird was that it was single. Behind the pilot's cabin was a reconnaissance equipment compartment (the so-called Q-compartment), reconnaissance equipment was also located in the fuselage inundations. With rare exceptions, the A-12s remained almost completely unpainted - only the bow with the pilot's cabin, the front edges of the wings and the cones of the air intakes were black.
Interceptor YF-12A
It is a combat branch of the Blackbird family. The main differences from spy planes:
- The YF-12A is equipped with a Hughes AN / ASG-18A fire control radar with an integrated infrared target search and tracking system.
- Armament - four AIM-47A (GAR-9) Super-Falcon air-to-air missiles.
- Behind the pilot's cabin, instead of the Q-compartment, a second cabin is provided, where the weapons operator was located.
In 1964, designer Clarence Johnson was awarded the Colliere Award āFor Outstanding Achievements in US Aeronauticsā. The Lockheed YF-12A presentation featured black-painted aircraft. Perhaps from here their informal name went - "Black Bird".
End of an era
By the beginning of the eighties, the resource of machines was already running out, and maintaining them in flight condition became very problematic. The situation with engines was especially difficult: the J-58 turbojet engine was discontinued at the end of the sixties, and although every 200 hours of operation the engines undergo complete disassembly and inspection, and after every 600 hours, overhaul, of course, they wear out. It was becoming increasingly difficult to get spare parts for them.
In the spring of 1988, US Air Force Secretary Edward Aldridge said the cost of maintaining the SR-71 fleet was equal to the cost of maintaining two wings of fighter aircraft. By that time, the number of machines in operation was halved - from 12 to 6. In 1989, it was decided to remove the SR-71 reconnaissance aircraft. In the spring of 1990, the āseventy-firstā were fired. Three machines were transferred to the NASA Dryden Flight Test Center as flying laboratories for the study of supersonic flight. Of the remaining at least six sides are mothballed and theoretically can, if necessary, be brought into flight condition.