Helicopters often are considered to be rather unreliable vehicles, but it’s not totally true. Today there are a lot of rotorcrafts, which possess some outstanding advantages such as vertical takeoff and landing, ability to operate in confined areas, and others. They may be used in evacuation, military operations, rescue missions, etc.

Now let us pay attention to helicopter engineering, which can be considered to be one of the most sophisticated fields within the realm of aviation. In order to develop such an aircraft, a person should invest a lot of efforts, and not all attempts resulted in success. Nowadays we have examples of both unsuccessful projects and those which managed to prove themselves well. However, some of them failed but gave a lot of valuable information.

1. Mil V-12 (“Homer”)

Undoubtedly, one of the best examples of an unsuccessful helicopter should be a giant Mil V-12. It got its alternative name of “Homer” in order to differentiate itself from others. The aim was to solve the issue of transporting bulky cargos including intercontinental ballistic missiles.

Key Specifications of the Mil V-12 (“Homer”)

• Type: Heavy lift helicopter
• Manufacturer: Mil Moscow Helicopter Plant
• First successful flight: 10 July 1968
• Status: Prototype program cancelled
• Number built: 2

One may note that it is the biggest rotorcraft of all times. The unique design of the helicopter is connected with using a wingspan-type rotor system and twin rotors. Due to this fact, it became a good vehicle to transport such loads. Nevertheless, there were quite a few aspects that prevented it from becoming a successful helicopter.

2. Lockheed AH-56 Cheyenne

It should be noted that this helicopter had an interesting task of becoming a real attack helicopter to be helpful in battles. The unusual design of the helicopter can be explained by its status of a compound helicopter combining both rotary and fixed wings.

Key Specifications of the AH-56 Cheyenne

• Type: Attack helicopter
• Manufacturer: Lockheed Corporation
• First flight: 21 September 1967
• Status: Program cancelled
• Number built: 10

As practice showed, it was not so. It can be explained by such facts as high cost of production and high complexity of operation. Engineers tried to improve stability but failed. In addition, reliability was not good enough, and it resulted in fatal crashes. These factors led to its cancellation in 1973. After that, the AH-64 Apache appeared. It is evident that this helicopter was a better choice than the previous one.

3. Hughes XH-17

The Hughes XH-17 was an ambitious attempt to create a heavy-lift helicopter capable of transporting extremely large loads using an unconventional propulsion system. Instead of relying on a traditional gearbox, it used tip-jet propulsion, where compressed air was fed through the rotor blades and ignited at their tips.

Key Specifications of the XH-17

• Type: Experimental helicopter
• Manufacturer: Hughes Helicopters
• First flight: 23 October 1952
• Status: Scrapped
• Number built: 1

In spite of this fact, there were some disadvantages, such as its unsuitability for any other operation besides the transportation of cargoes. In addition, noise level was high. Another significant drawback was frequent replacement of the blades.

4. Yakovlev Yak-24 (“Horse”)

This rotorcraft had its primary aim of becoming a reliable heavy lift helicopter. It should be noted that its design was based on tandem rotors, i.e., two rotors: one placed in the front and the second – in the rear. This helicopter was created for carrying soldiers and cargos.

Key Specifications of the Yak-24 (“Horse”)

• Type: Transport helicopter
• Manufacturer: Yakovlev Design Bureau
• First flight: 3 July 1952
• Status: Retired
• Production: Approximately 40–100 units

Nevertheless, as soon as it started its operation, it revealed a lot of problems. Among the most widespread drawbacks, one should indicate severe vibration, which was harmful for helicopter’s systems. Attempts to improve this aspect were vain.

5. Percival P.74

One may say that this helicopter is unique due to some special peculiarities of its design. It is rather similar to the previous one as its main aim was to carry bulky loads. It used such a thing as a tip jet rotor system. It means that there were no gearboxes

Key Specifications of the Percival P.74

• Type: Experimental helicopter
• Manufacturer: Hunting Aircraft
• Status: Cancelled in 1956
• Power system: Tip-jet rotor concept
• Number built: 1

Despite years of development and testing, the P.74 was unable to achieve flight. The engines failed to produce sufficient lift, leaving the aircraft grounded even during test runs. Engineers attempted to improve performance through modifications, but these efforts were unsuccessful.

6. Kamov Ka-50 (“Black Shark”)

This rotorcraft is a unique one due to some innovations. One of them is its coaxial rotor system which allowed getting rid of the tail rotor. This fact contributed to higher maneuverability. In addition, this helicopter was light-weighted and compact, which were its advantages.

Key Specifications of the Ka-50 (“Black Shark”)

• Type: Attack helicopter
• Manufacturer: Kamov
• First flight: 17 June 1982
• Introduced: 1995
• Number built: Approximately 18–19

However, as it appears, some of its ideas hindered it from becoming successful. Its status of a one-man helicopter did not allow its pilot to control surroundings properly while the aircraft was operated. Thus, engineers decided to modify it into a two-man machine known as Kamov Ka-52 Alligator.

7. Sikorsky CH-53E Super Stallion

This helicopter may be ranked as one of the largest and most effective ones. It was created with the aim of performing various operations related to heavy lifting and transportation of passengers and various types of equipment.

Key Specifications of the CH-53E (“Super Stallion”)

• Type: Heavy lift military helicopter
• Manufacturer: Sikorsky Aircraft
• First flight: 1 March 1974
• Introduced: 1981
• Number built: 172

However, there were a few aspects which hindered it from performing its tasks. Among them, one can single out its complex maintenance process and its old age, which caused accidents. It is evident that such disadvantages resulted in developing its modification called CH-53K King Stallion.

8. Bell Boeing V-22 Osprey (Early Service)

This helicopter was considered to be very promising one as it used an innovative approach to its operation. It was equipped with a tiltrotor system allowing it to combine vertical takeoff with fixed-wing flight, as well as hovering. Thus, it could perform various kinds of missions and could be useful in different situations.

Key Specifications of the V-22 Osprey (Early Service)

• Type: Tiltrotor military transport aircraft
• Manufacturers: Bell Helicopter and Boeing
• First flight: 19 March 1989
• Introduced: 2007
• Primary user: United States Marine Corps

However, its early development was marked by serious challenges. The complexity of the tiltrotor system led to several accidents during testing and initial deployment. Pilots also had to manage unique aerodynamic risks, such as vortex ring state.

9. Hiller OH-23 Raven

The Hiller UH-12, later known as the OH-23 Raven in military service, was one of the earliest practical helicopters developed in the late 1940s. It played an important role in both civilian and military operations, including reconnaissance and training missions, helping to establish the foundation for future rotorcraft designs.

Key Specifications of the OH-23 Raven

• Type: Light observation helicopter
• Manufacturer: Hiller Aircraft
• First flight: 1948
• Production: 1948–1965
• Number built: Over 2,000

However, it cannot be regarded as a perfect helicopter, as it possessed a number of flaws. To begin with, it was underpowered and its autorotation abilities were poor. Additionally, it was unable to operate well under bad weather conditions.

10. Eurocopter AS332 Super Puma (Early Variants)

It should be said that this helicopter was a better version of its predecessor known as Puma. It used more powerful engines and had higher weight capacity. Because of this, it could be used not only in military but also in civilian sphere.

Key Specifications of the Super Puma (Early Variants)

• Type: Utility helicopter
• Manufacturer: Aérospatiale / Eurocopter / Airbus Helicopters
• First flight: 13 September 1978
• Status: In service
• Production: Over 1,000 aircraft

However, early variants of the Super Puma experienced serious mechanical failures, particularly involving the main gearbox. These failures led to several fatal accidents, especially in offshore environments. While later models addressed these issues, the early incidents highlighted the importance of rigorous engineering and safety standards in helicopter design.