Late to the Party
In the immediate post war years the helicopter was coming into its own and being embraced by militaries on both sides of the Cold War. Both east and west fielded light utility types though it was the United States which introduced the first true transport helicopter into service in the form of the Sikorsky S-55 which first flew in 1949.
The Soviet army lacked such a dedicated transport helicopter at the time; however, the versatility and flexibility the S-55 provided American and allied forces with in the Korean War would change that very quickly.
In 1951, on the direct orders of Stalin himself, Soviet helicopter manufacturers were given 12 months to develop a machine which would give their army the same mobility and flexibility that the S-55 was giving to the west. Ultimately, only the Mil bureau rose to the challenge and the prototype for the Mi-4 flew for the first time in 1952.
The Mi-4 entered service with the Soviet and Polish air forces in 1953. It would be the beginning of a long and varied life for an aircraft which would form the backbone of Warsaw Pact rotary wing transport until the 1970s. In the full scope of its career, the Mi-4 would do much, much more than simply move equipment and personnel from one place to another.
The helicopter existed in both military and civilian variants. Inside a production run totalling roughly 4000 airframes from both Soviet and Chinese assembly lines, the aircraft family comprised at least 30 different versions. Throughout its lifetime, the Mi-4 was subject to constant development and upgrading.
The Sincerest Form of Flattery?
From a western perspective, the Mi-4 spent its life being derided as nothing more than a copy of the Sikorsky S-55. This could be attributed as much to the dominating point of view in the west that the bulk of Soviet produced military hardware was simply copies of, presumably, superior western designs as it could be to any physical resemblance the two aircraft shared.
The similarity between the two aircraft is quite understandable as long as one keeps in mind that Stalin only gave one year to develop a helicopter and the S-55 had already proven itself as a design formula that worked in battle. For any of the Soviet aircraft manufacturers to try to create a clean sheet design and take it to flying status in the space of a year would have been, frankly, idiotic and wasteful. Drawing inspiration from the Sikorsky design was perfectly sensible given the time available and the projected role of the finished product.
On even brief examination, the two aircraft have more differences than similarities:
The Mil helicopter was a significantly larger and stronger machine than the S-55 and more flexible in what it could transport. It was possible to open the entire rear fuselage and load vehicles, artillery pieces and other larger loads which were completely outside the S-55’s ability to lift internally.
From a strictly weight lifting standpoint, the Mi-4 was much more comparable to Sikorsky’s S-58 which superseded the S-55. However, the S-58 still did not have the same internal carrying abilities the Mi-4 did. To carry such loads as vehicles and artillery, the S-58 would need to carry them externally in a sling under the aircraft.
While attempts were made to adapt the S-55 to the armed gunship role, all but the most modest of gun armaments proved too heavy for it and left it under powered for the task. The Mil, by contrast, adapted very well to the attack helicopter role and was able to carry a variety of guns, rockets, mines and even torpedoes in a specialized anti ship variation. The Mil’s armament also included a gondola in the underside of the fuselage which could be fitted with a forward firing machine gun.
The above are the larger differences between the two, certainly more could be uncovered on closer scrutiny. Suffice it to say, the Mil designers most certainly took inspiration from the Sikorsky design but in no way created an imitation of it.
Generally speaking; if one is to look at western helicopter designs that could be considered contemporary to the Mi-4, there really wasn’t any direct and complete counterpart for it.
Working Like a Dog
The Mil-4, which was known as “Hound” under the NATO code naming system for Soviet aircraft, was a very busy aircraft in both military and civilian circles.
In military service, it fulfilled roles as diverse as transport, electronic warfare, maritime patrol, reconnaissance, VIP transport, medical evacuation and rescue work among others.
Notable military actions the Mi-4 played a role in include the Hungarian uprising of 1956, the Indo Pakistani War of 1971 and the Soviet occupation of Afghanistan during the 1980s.
The Hound’s military life spanned a little over 50 years; the last military variants, Chines built Harbin Z-5 versions, were retired by Albania in 2005.
In the civilian world, it was every bit as busy operating in agriculture, forestry, fisheries, geology and infrastructure fields as well as bush flying in Siberia, Antarctic exploration, air taxi, air ambulance and fire fighting.
Outside of regular duties, a modified version of the Mi-4 was used to set a number of speed and altitude records in the late 1950s. Additionally, the Mi-4 won a gold medal at the World’s Fair in Brussels in 1958.
The Mi-4 Today and Learning More
By all appearances, it would seem that there are no remaining airworthy examples of either the Mil Mi-4 or Harbin Z-5 at the time of writing.
Several seem to be either restored or in storage at museums in several locations around the world while others look to be abandoned and corroding into oblivion in other places. As such, there are certainly opportunities to see these aircraft though the quality may be highly variable depending on where you see them.
Following this link will take you to the Polish Aviation Museum’s information page about the Mi-4:
This link will take you to an entry at the Travel for Aircraft blog featuring the Mi-4 used as Ho Chi Minh’s personal transport: