Igor Sikorsky built the world's first four-engined aircraft, The Russky Vitaz, in 1913. The Ilya Murometz became a radically improved modification. The first built Ilya Murometz was a purely civil transport/airliner, providing exceptional luxirities as no any other aircraft many years ahead:
Many demonstration flights were performed over the imperial capital and its environs. Unlike pilots of single-engine aircraft, Sikorsky was confident in reliability of multi-engine aircraft. Some flights were performed over city as low as at 400 meters. Every flight by the Ilya Mouromets attracted huge crowds, bringing street traffic to a standstill.
The record flight of Ilya Mouromets took place in June 30 - July 12, 1914. Flight from St.Petersburg to Kiev (1200km wit one refueling stop in Orsha) and back (with refueling in Novo-Soloniki). During flight to Kiev one of engines caught a fire, sprayed with gasoline from broken fuel pipe. It was extinguished in-flight, but landing was made to have it back running and to avoid arrival to Kiev in dark time.
The flight back (13 hours) was performed without accidents, despite the aircraft faced severe turbulence and air pockets up to 500m deep flying over forest fire area. Weather condition sometimes forced crew to fly above the clouds without using ground features.
As the WWI broke out, Murometsy were ordered into production by Ministry of War. German Argus engines became unavailable, and aircraft was re-engined for French Salmson. Those proved to be less useful, and contributed to the negative attitude of military pilots toward the Ilya Mouromets.
Early in the war attempts were made to arm the aircraft with 37mm Hotchkiss or a 3-inch recoilless Gelvig/Oranovsky cannons, as well as to protect pilots with 2mm steal a'la modern-day knights' armor. Most of those efforts were found impractical.
One Ilya Mouromets was equipped with floats and made several successful flights, but was found of little military significance. All those novel experiments took a considerable amount of time and efforts, but mostly were rejected as impractical.
Another problem was that military pilots - elite of all times - had to re-train to new flying machine in the war emergency under supervision of civilians. This certainly bruised their egos.
For training purposes two-engine IM's were employed. Salmson engine problems and errors of young pilots resulted in few non-fatal crashes. But a tradition came to life to blame all on the Ilya Mouromets.
Dostoevsky once said, "Give a Russian student a map of the Heavens and he will submit it to you next day with corrections"... Even this superior aircraft failed under critics of aviators.
But quite soon the aircraft found its place as prominent bomber, capable carry as many as 700-800kg of bomb load. Powerful strikes again railroad stations and bridges deep into enemy territory were performed regularly. Raid of a single plane was able to paralyze life at a targeted railroad station for few days.
Many reconnaissance missions were flown hundreds kilometers into enemy territory, photographing depots and regiment movements. Confidence in the aircraft was growing so fast, that it resulted into negligence. Pilots even started to through away defensive machineguns to take more bombs...
The Third Army chief of staff Major General Romanovsky expressed this confidence very clear : "Give me just three Murometsy and take away all the light aeroplane - and I will be satisfied."
Aircraft had internal bomb bay and bombsight to provide precise bombing. Other aircraft of early WWI relied on crew throwing bombs or grenades by hands from the open cockpit, using eyesight for aiming... Numerous machineguns (see below) provided Ilya Mourometz with excellent defence, and it was easy to believe a legend that no one of those giants was shot down.
Indeed, there were 3 cases when the first heavy bomber was shot down. But during service it scored more than 10 air-to-air victories, so it seems right to honor it as The Only Heavy Bomber With Positive Score vs Fighters. And, as usual, plane shooting down Ilya Mourometz received quite a heavy damage. Lucky hunters, I guess, were happy to have their fighters landed safely, as well as to have such a air victory.
In May-October 1921 few "Ilya Mouromets" aircraft were used on the passenger line Moscow-Kharkov. Line was closed because aircraft were extremely worn. About 76 flights were performed. This division was retired completely only in May 1923, when giant wooden planes got worn beyond repair.
August 2, 1921 - one IM participated in Air Fleet Day celebration in Moscow;