On 29 March 1999, the Yugoslav media published a story headlined titled "Sorry, we thought you were invisible" that spread round the world.
What happened?
A few hours after midnight on 24 March 1999, NATO commenced military action against Yugoslavia. Tomahawk missiles and laser-guided bombs were launched against military bases and communications centres.
The bombardment of selected targets continued for several nights and NATO experts were convinced that the Yugoslav air defence had been destroyed.
What followed came as a surprise.
In the night of 27 March an F-117 took off from the NATO base at Spangdahlem in Germany to carry out a military action in Yugoslavia.
About 40 km before the Yugoslav-Croatian border it was detected by a radar dating from the 1970’s, and a few minutes later the F 117A was shot down by Yugoslav air-defence at Budjanovci about 45 km to the northwest of Belgrade.
The official US military explanation was that the F117 had technical trouble.
Yugoslav and some French and German newspapers reported later that two more F 117 had been damaged and made emergency landings in Bosnia.
A few hundred flights in the first Gulf war 1991 without any trouble, and some military operations in Central America confirmed the superiority of the plane. The US Air Forces bought 54 planes in the first phase at a cost of $40 million each.
The shooting down of the plane in Yugoslavia was a big shock and a blow to American pride.
F117 was developed under highest possible degree of secrecy, with the US government investing enormous funds to make it invisible to radar.
The author has collected data for more than three years from the army experts, military magazines, Internet, acquaintances from Serbia, and eyewitnesses of the event. All the technical data was checked by two radar experts, one from France and one from Slovenia.
The article first describes the principle of operation of the radar.
Then the methods of hiding the aircraft from radar are explained.
The size comparison radar cross-section for the airplanes B 52, F-16 and F-117 aircraft is given, clearly showing a considerable reduction of the radar cross-section surface for F-117.
Further reduction of the received signal scattered from the aircraft was achieved by the so-called stealth technique in which a coating of special material, known as microwave absorber, is applied to the aircraft. The material absorbs some EM waves and transforms them into the heat.
The different types of absorbers and their method of working are given.
The author obtained a complete coated piece of fuselage and wing and had the ICP-OES spectroscopic chemical analysis made. The analysis showed a multi-layer coat structure on a ferromagnetic basis.
Measurements of the extent of absorption of the EM waves against different frequencies were made and are shown in the figure. The results are surprising.
Another table shows the strength of radar signals scattered from F-117 by military air surveillance radars at various frequency ranges, with the figures for the minimum detectable signal included for all radars described.
In the next graph the visibility of the F117 for different radars is given.
Then the types of radars Yugoslavia had in 1999 at the time of the attack are described.
The aircraft were detected at the distance more than 40 km from the radar, and a few minutes later it was shot down, about 45 km to the northwest of Belgrade. The pilot was later rescued by helicopter. An eyewitness statement shows how it happened.
In conclusion:
- Experience gained by using it in the "Gulf War" and in the South America cannot be the reference for success of this weapon elsewhere.
-The F-117 was never invisible to radar and will thus become an easier target for the air defence, since owing to their non-aerodynamic shape they travel at lower speeds and are less agile than other modern aircraft.
- I feel sure that at least the Russian and the Chinese armies know very well the response to the "invisible F-117 ".
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