Lockheed SR-71 Blackbird: Flight Performance

Lockheed SR-71 - one of the most famous reconnaissance aircraft and at the same time one of the most unknown. "Blackbird" is the brainchild of the famous aircraft designer Clarence Johnson, the head of the department of advanced development (ADP) firm Lockheed. Designed in the late 50's, Blackbird still looks futuristic, and this despite the fact that it was created not by high-speed computers, but by an ordinary culmination.

Design

SR-71 Blackbird is built according to the "tailless" scheme with a triangular wing and a two-kilo tail unit. The construction is traditional - with stringers, frames and working plating. Carefully "licked" forms serve not only aerodynamics. "Stealth aircraft", created by technology Stealth, is considered to be the invention of the last decade, but this technology is largely embodied in the design of "Blackbird". Rounded contours and smooth mating surfaces make the aircraft less noticeable for radar.

The strategic supersonic scout has almost no flat surfaces. The exception is rather large keels, but they are inclined inwards, which reduces their effective scattering area. In addition, in the design of the front and rear edges of the wing are used radio absorbing materials in the form of triangular inserts of honeycomb plastic structures. Due to this form of insertions, the radio waves are reflected inside the triangle until it attenuates completely. To top it all, the operating radio equipment distorts the signal reflected from the aircraft, confusing operators of air defense radars.

When a long flight at supersonic speeds, the aircraft is subjected to a strong and prolonged heating. Therefore, the design of "Blackbird" is almost 93% composed of high-strength and heat-resistant titanium alloy "Beta B-120".

Fuselage

Considering that at speed smooth panels of the wing skin are warped and blown from the heating, these elements are made corrugated. Longitudinal grooves not only work as stiffeners, but also increase the area of heat dissipation, almost without increasing resistance.

Many modern American combat aircraft have influxes on the root part of the wing, but at Blackbird they occupy the entire length of the fuselage, because of which its cross-section from the round turns into an almost diamond-shaped section. These influxes play a dual role: they create a very significant lifting force, which reduces the bending moment by half on the long fuselage, while simultaneously serving fuel and equipment. In addition, they work on aerodynamics, reducing drag.

The crew is housed in "tandem" cabins with separate, back-opening lanterns. Glazing cabins model Lockheed SR-71 is made of a special glass, not allowing hard ultraviolet radiation at high altitude. The cabins are air-conditioned, the crew makes a flight in high-compensating suits.

Wing

The wing has a twist of outer cantilevers, reducing the bending and twisting moments on it. The blowing of the model in the wind tunnel showed that there is no need for flaps or slats - a large wing on the landing creates a powerful air cushion, providing a very soft landing almost without pilot intervention. The widely spaced nacelles are carefully smoothened and have noticeable outliers on the outer side of the junction with the leading edge of the wing.

Tail tail

The vertical tail unit is made all-turning. Such keels are 2.5 times more effective than traditional rudders and require smaller deflection angles, which reduces the resistance. The maximum deflection angle of the Blackbird keels at speeds up to 0.5 Mach is 20 °, at a higher speed it automatically decreases to 10 °. Keels are inclined inward by 15 °, which positively affects stability and controllability. For example, supersonic aircraft SR-71 is not afraid of a side wind up to 18 m / s. The rear edge of the wing is entirely occupied by combined ailerons and elevator rudders.

Motors

"Blackbird" has two particularly powerful engines such as the TRD Pratt & Whitney JT11D-20B (another designation is J58) with a thrust of 144.56 kN. In them lies the secret of the vast range of Blackbird: at Mach 3 speed, the motors become essentially in-line: 58% of the thrust is provided by the air intake, 25% by the nozzle and only 17% by the actual engine. Air intakes of the "Black Bird" aircraft were designed to give a significant part of the total traction. Cones are made adjustable to hold the shock wave in the air intake.

By designing the J58 engine, experts from Pratt & Whitney faced serious difficulties: the air intake temperature reached 380 ° C, the fuel injectors 160 ° C, the afterburner 280 ° C, and the engine oils 485 ° C. Therefore, in the J58 design, in addition to titanium, the highly heat-resistant nickel alloys Hastelloy-X and Rene-41 were used. Because of this intense thermal regime, the engines passed a full disassembly and inspection every 200 hours of operation.

Chassis

The chassis of the Blackbird is three-wheeled with a bow wheel. The bow support with two wheels is retracted forward, the main support is to the center. The chassis is cleaned immediately after being pulled off the ground, as the Lockheed SR-71 quickly accelerates to the maximum permitted speed with the chassis released (555 km / h). The main supports have three wheels on one axis to reduce pressure on the ground and simultaneously save the internal volume of the fuselage.

Tires are made not of rubber, but of a special refractory material, and in order to maintain constant pressure on all flight modes, and to avoid oxidation, they are filled not with air, but with nitrogen. They have a smooth protector and are covered with silver paint to reduce heat. Wells of the chassis are surrounded by fuel tanks - fuel plays a role of a cooling liquid.

Brake system

The reconnaissance aircraft is equipped with a single brake parachute with a diameter of 12 m, produced with a pyro cartridge immediately after touching the runway at a speed of 280-330 km / h. The parachute is made of a special heat-resistant material and made mesh so that it does not break with a high-speed head. It detaches when the speed of the aircraft drops to 110 km / h, so that the halyard is not entangled in the keels.

Equipment

US aviation uses the most advanced telemetry and control systems. "Blackbird" is equipped with an eight-channel system of stability enhancement (SPU), which compensates for the "built-in" instability of the aircraft (it is caused by uneven heating in cruising flight). The system operates on all three axes of coordinates and is three times duplicated.

At speeds of 3 Mach and higher, too energetic actions by the rudders can lead to a drastic change in the position of the aircraft in space, and this is fraught with its destruction. On the other hand, at the altitude at which the SR-71 Blackbird operates, air density is less than 2% of its density at sea level, therefore a large deviation of the rudders is required.

SPU was created by Honeywell and proved to be one of the most reliable in the whole plane: the average time between failures is about 130,000 hours. If the system is still broken, it's difficult to control the aircraft in cruising mode, but it is possible.

Honeywell has also developed a computer for processing flight data, which corrects for distortions that occur in flight at supersonic speeds. Due to the strong low-pressure air at high altitude, conventional instruments with data input from the LDPE tubes were unreliable. The exact values of the vertical velocity, altitude and speed in the Mach numbers were output from the computer to three digital displays in the pilot's cabin.

Fuel system

The strongest and longest heating of the Lockheed SR-71 in a cruise flight required the development of new fuels and lubricants, sealants, slurries, insulating materials, etc. So, the fuel used in Blackbird, JP-7, has such a high temperature Flare that it had to be set on fire with a special reagent - triethylborane (TEB). Due to this, it is used as a coolant to cool the crew cabs and the most sensitive to overheating components, especially the chassis. But with the development of fuel, the uneven heating of the fuselage began, which caused the deformation of its influxes.

In a special tank on the plane there is a stock of triethylborane for starting engines in the air and forcing the afterburner. The strategic scout is equipped with six fuel tanks, which hold 46,000 liters of fuel. The integral tanks, their upper and lower walls form the skin, and because of the systematic expansion and contraction of the glider during heating and cooling, they crack. After every 200 hours of flying, they are sealed, but still the tanks flow, and under the standing in the parking lot, fuel piles accumulate. Since the fuel JP-7 is non-volatile, there is practically no fire hazard, but in the cruising flight the tank walls are heated to 280 ° C, so that even the JP-7 fuel with its high flash point can give an explosion. Therefore, in flight, the tanks are filled with nitrogen.

Specifications

The SR-71 has the following specifications:

• The length is 32.7 m.
• Wingspan: 16.9 m.
• The height is 5.6 m.
• Takeoff weight - up to 78 tons.
• The range of flight is 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 versions of Blackbeard, the armament had only supersonic interceptor aircraft YF-12A. It consisted of four Hughes GAR-9 (AIM-47A) Super-Falcon air-to-air missiles guided by AN / ASG-18A radar. The reconnaissance versions of the weapons were not available, although the option of installing a resettable container with nuclear bombs on the SR-71, in the manner of the Convair B-58 Hustlen bomber, was being worked out.

Elusive

Military aircraft play an important role in the modern strategy of warfare. Despite the impressive grouping of tracking satellites from leading powers, aviation is still important in conducting reconnaissance missions. Perhaps, it is the Blackbird is the most legendary reconnaissance aircraft.

Having visited all the "hot spots" of the world, the SR-71 has never been shot down. In 1972, the words of a former Air Force sergeant working for the National Security Agency were quoted in the military journal Ramparts: "It is impossible to bring down the SR-71". The sergeant cited cases when the Chinese tried to do this, but the pilots of the intercepted MiG-21 interceptors only had to wonder where the perpetrator had disappeared. According to him, the Blackbirds flew over the Soviet territory, and the listening stations of the ANB along the borders of the USSR fixed the reaction of Soviet air defense. Moreover, the former sergeant said that the US electronic reconnaissance equipment allowed them to monitor the flights of almost all Soviet military aircraft and even determine who is currently piloting this or that car. And this is a great merit of the "seventy-first".

During the 70's, American aircraft flew over North Korea, China, Cuba, along the borders of the USSR. At the same time, meetings were held with the Soviet interceptor, the MiG-25P, which was the fastest for those times, and they ended, according to the testimony of the Americans, not in favor of the latter. Unsuccessful were also attempts to get the elusive "guest" by the newest at the time anti-aircraft missiles.

Lockheed A-12

The name "Blackbird" is associated most often with the strategic intelligence officer SR-71. However, behind this name there are two more not so well-known machines: 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. A (attack) was assigned to stormtroopers, but the A-12 clearly does not look like an attack aircraft. This is done to confuse the intelligence of the USSR after a grand international scandal involving the shooting down 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 just focused on these operations. Formally, it was considered "civil", 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 there are a lot of defects in the design. Especially annoyed power plant, which required a long and time-consuming debugging air intakes. Despite this, the A-12 was launched into the series - the CIA urgently needed a high-speed scout to replace the outdated U-2. 14 copies were produced.

Design Features

Lockheed A-12 Remained essentially experimental - it had many shortcomings, which could be eliminated only by reworking 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 task, had to be managed with numerous reconnaissance.

External signs of the A-12 were a strongly pointed nose with straight edges of the front parts of the influx of the fuselage and a short tip of the latter. The main difference from the subsequent modifications of "Blackbird" was that it was single. Behind the pilot's cab was a compartment for reconnaissance equipment (the so-called Q-compartment), reconnaissance equipment was also placed in the influx of the fuselage. With rare exceptions, the A-12 remained almost completely unpainted - only the nose with the pilot's cab, the front edges of the wings and the cones of the air intakes were black.

Interceptor YF-12A

He is a fighting branch of the "Blackbird" family. The main differences from aircraft spies:

• On the YF-12A is installed a fire control radar model Hughes AN / ASG-18A with the conjugate IR system search and tracking targets.
• Armament - four AIM-47A (GAR-9) Super-Falcon air-to-air missiles.
• For the pilot cabin instead of the Q-compartment is provided a second cabin, where the operator of the armament was located.

In 1964, Designer Clarence Johnson was awarded the Collier Award for Excellence in Aeronautics USA. At the presentation of the Lockheed YF-12A, airplanes painted in black were presented. Perhaps, from here and went to their informal name - "Black Bird".

End of an era

By the beginning of the eighties the resource of machines was already running low, and their maintenance in the flight state became very problematic. Particularly difficult was the position of the engines: the JD-58 was withdrawn from production in the late sixties, and although every 200 hours of operation, the engines undergo complete disassembly and testing, and every 600 hours - overhaul, of course, they wear out. Spare parts for them were hard to come by.

In the spring of 1988, US Air Force Secretary Edward Aldridge reported that the cost of maintaining the SR-71 is equal to the cost of maintaining two wings of fighter aircraft. By that time, the number of cars in operation had been halved, from 12 to 6. In 1989, it was decided to lift the SR-71 reconnaissance aircraft from armament. In the spring of 1990, the "seventy-first" were dismissed. Three vehicles were transferred to the NASA Dryden Flight Test Center as flying laboratories for research on supersonic flight. Of the remaining at least six boards are conserved and theoretically can be put in flight if necessary.