Operationally, the IM was known for her ability to withstand combat damage to the point that she reach mythical status among her supporters as a bomber that could not be shot down. Her defensive weapons arrangement no doubt made many an enemy airmen think twice before tangling with IM's. To drive the point further, it was noted that German fighter pilots oft-refused to tangle with IM's if they could avoid it, such was her reach and defensive circle created by her guns and gunners. In fact, reports show that only one (some sources state up to three) IM bombers were ever lost to enemy fire in the air while IM crews themselves were credited with at least 10 air-to-air victories - a ratio few wartime bombers can boast. The first IM bomber was lost to no less than 4 German Albatros fighters on September 12th, 1916. Despite this loss, three of the four German fighters were also destroyed. Other Ilya Mourometz's were destroyed by Russian hands to avoid capture by Germans - such was the value of the Mourometz.
IM's were seen in a myriad of production forms throughout her wartime run from 1913 through 1917. Among these were the early No 107, Kievsky No 128, Type B No 135 and Type Nos 136 through 139's. These were differentiated by their selection of engines of either the German Argus or French Salmson brands ranging from 100 to 200 horsepower. The No 107 (appearing in 1913)utilized four of the Argus 100 horsepower engines while Kievsky (1914) saw fit to give their No 128 2 x Argus engines of 140 horsepower and 2 x Argus engines of 125 horsepower. While the Type B No 135 - appearing in 1914 - fitted 4 x Argus engines of 130 horsepower each, the Type B No 136-139 (beginning use in 1914) were outfitted with Salmson series engines in a 2 x 200 horsepower and 2 x 135 horsepower arrangement. It was not wholly uncommon to mix and match engines in this fashion while finding the right balance of output and weight all the while dealing with wartime availability and shortages.
The most common model in the IM line became the Type V (S-23) to which some 32 to 34 were produced from 1914 through 1916. Type V's were the first in the Mourometz line to be developed from the start as a bomber (the previous offerings were conversions). These were fitted with 4 x Sunbeam Crusader V8 engines of 148 horsepower each. The Type V No 151's arrived in 1915 with their 4 x Argus engines of 140 horsepower each. The Type V No 159 was a crew trainer from 1915 onwards and was fitted with just 2 x 225 horsepower engines of the Sunbeam brand - no doubt in an effort to commit engines to war-bound aircraft instead. 4 x RBVZ-6 engines of 150 horsepower each were added to the design of the Type V No 167, also appearing in 1915.
1916 brought about more faces in the IM line, this including the Type G-1 with her 4 x Sunbeam engines of 160 horsepower each. Likewise, the Type G-2 "Russobalt" utilized an arrangement of 4 x RBVZ-6 series engines of 150 horsepower each (RBVZ designating its Russo-Baltic Carriage Factory origins) and were built in 30 production examples. The Type G-3 saw fit to combine 2 x Renault engines of 220 horsepower (each) with 2 x RBVZ-6 engines of 150 horsepower each. The final IM production model became the Type E "Yeh-2" model with her 4 x Renault engines of 220 horsepower, appearing in only 10 production examples. By 1918, only 13 IM aircraft were built, effectively signaling the end of the IM's wartime production run. Some 80 total Ilya Mourometz were eventually produced.
As an aside, one IM aircraft was produced with water floats and, though it provided for some successful water-based landings and take-offs, the arrangement was not found to offer much in terms of military value. Other costly (manpower and financial) developments were also pursued with many ending up abandoned. License production was undertaken by the British and French while the Sikorsky four-engine bomber concept was copied throughout the world during the war years and beyond. The aging Ilya Mourometz line was replaced during the war World War 1 by Sikorsky's new Alexander Nevsky bomber design beginning in 1916. In all, the Mourometz line served through some 400 combat sorties against targets in Germany and Latvia, mostly from Vinnitza in Poland during the war.
The Ilya Mourometz proved herself a capable mount in her relatively short time along the Front. Despite missing out on the chance to become the world's first four-engine, multi-passenger commercial airliner, the IM instead developed many "firsts" in the realm of military aviation. The IM was the world's first purpose-designed, four-engine bomber featuring an internal bomb bay, bomb sighting device and excellent defensive armament. Specialized techniques were also developed for machine gun crews when combating multiple enemy fighters at one time. As the war rolled on, bombing effectiveness from IM platforms reached near-excellent levels.
IM's enjoyed a short-lived existence after the war with a handful still being produced. From May through October of 1921, Moscow-Kharkov line was finally able to utilized the aircraft in its originally intended role of passenger transport until these aircraft were deemed too fragile for further use. The aged technology and construction methods had finally taken their toll on this fine machine. After 1921, IM's were all but extinct with the last IM's flying in 1922. Beyond the Russian Empire Air Force and soon-to-follow USSR Air Force, Poland was the only other operator of the aircraft.
Incidentally, the name, Ilya Mourometz, is a hero based in Russian mythology.
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