Sikorsky's Ilya Mourometz was the world's first four-engine bomber. Construction started in August, 1913 and first flight was in January, 1914. The cockpit had space for several persons. Openings on both sides of the fuselage permitted mechanics to climb out on the wings to service the engines during flight. A hatch on the left side provided an exit to the front bridge. Behind the cockpit was a large passenger cabin. In the rear was a stairway to the upper bridge and a washroom. Further back was a private cabin including a berth, small table and cabinet. During World War I over 75 ILia Mourometz were deployed in a special squadron at the front for bombing and reconnaissance missions.
The Ilya Muromets (Sikorsky S-22) was designed and constructed by Igor Sikorsky at the Russo-Baltic Carriage Factory (RBVZ) in Riga in 1913. It was based on his earlier S-21 Russky Vityaz or Le Grand which had played an important role in the development of Russian aviation and the multi-engine aircraft industries of the world.
Russia had a chance to become the birthplace of the first multi-passenger and multi-engine airliner. The Ilya Muromets was first conceived and built as a luxurious aircraft. For the first time in aviation history, it had an insulated passenger saloon, comfortable wicker chairs, a bedroom, a lounge and even the first airborne toilet. The aircraft also had heating and electrical lighting.
On 10 December 1913, the Ilya Muromets was tested in the air for the first time, and on 25 February 1914, took off for its first demonstration flight with 16 passengers aboard. From 21 to 23 June (one source gives 30 June - 12 July interval), it set a world record by making a trip from St Petersburg to Kiev, a distance of some 1200 km, and back. The first leg took 14 hours and 38 minutes with one landing for fuel - at Orsha, and the return one, with a fuel stop at Novosokolniki, took even less time, some 13 hours. If it had not been for World War I, the Ilya Muromets would probably have started passenger flights that same year.
With the beginning of World War I, Sikorsky decided to change the design of the aircraft to become the world's first purpose-designed bomber. Internal racks carried up to 800 kg of bombs, and positions for up to nine machine guns were added for self-defense in various locations, including the extreme tail. The engines were protected with 5 mm-thick armor.
In August 1914, the Ilya Muromets was adopted by the Imperial Russian Air Force. On 10 December 1914, the Russians formed their first ten-bomber squadron, slowly increasing the number to 20 by the summer of 1916. During World War I, the Germans often refused to attack Ilya Muromets in the air due to their defensive firepower. On 12 September 1916, the Russians lost their first Ilya Muromets in a fight with four German Albatroses, three of which it managed to shoot down. This was also the only loss to enemy action during the war, while three others were damaged in combat, but managed to return to base to be repaired.
The heavy bombers of other participants appeared in 1916, all resembling the Russian pioneer to a certain degree. The Russian government and Sikorsky himself sold the design and production license to the British and the French. The Germans tried to copy its design, using the fragments of the example they had shot down over their territory in September 1916.
By the end of 1916, the design was generally believed to have exhausted itself. The ensuing modifications, such as additional armor, made the aircraft too heavy and not worthy of upgrading. Even though the English, French and German bombers were faster, Sikorsky decided to switch to a new type of aircraft he would call the Alexander Nevsky.
The Russians built 73 Ilya Muromets bombers between 1913 and 1918. During this period, the Russians were the first in aviation history to perform bombing from heavy bombers, bomber group raids on enemy targets, night bombing and photographic bomb damage assessment. They were also the first to develop defensive tactics for a single bomber engaged in an air combat with a number of enemy fighters. Due to systematic weapon upgrades, the effectiveness of bomb-dropping reached 90%. The Ilya Muromets performed more than 400 sorties and dropped 65 tons of bombs during the war.
The last flight of an Ilya Muromets bomber took place in 1922 at the Air Shooting and Bomb-dropping School in Serpukhov.
The S-22 cockpit had sufficient space allowing several persons to observe the pilot. Openings on both sides of the fuselage permitted mechanics to climb out onto the wings to service the engines during flight. Hatch on the left side provided an exit to the front bridge. Behind the cockpit was a large passenger cabin with four large windows on each side. Placed at the rear was a stairway to the upper bridge and a washroom. Further back was a private cabin which included a berth, small table and a cabinet. Lighting was provided by a wind driven generator and heating was supplied by two long engine exhaust pipes which passed through the corners of the cabin.