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BTO ( RANK 2.0 ) ( 🇺🇸 USA ) ( Rotary-Wing Aircraft ) ( Sikorsky R-4 (XR-4) Helicopter )

🚁 Sikorsky R-4 (XR-4) – Overview and History
The Sikorsky R-4 was the first mass-produced helicopter in the world and the first to enter military service. Designed by Igor Sikorsky, it made its maiden flight in 1942 and was used by the U.S. Army Air Forces, U.S. Navy, Royal Air Force, and others during World War II.

It revolutionized battlefield mobility, especially in rescue and reconnaissance missions where conventional aircraft couldn’t operate.

🛠️ Design and Role
Built around a single main rotor and tail rotor configuration.

Used primarily for:

Pilot training

Medical evacuation (MEDEVAC)

Rescue missions in rough terrain or at sea

Light reconnaissance and transport

Praised for its agility, vertical takeoff/landing capabilities, and versatility in missions where fixed-wing aircraft couldn’t reach.

⚔️ Military Use
Deployed during:

World War II (Burma Theater, Pacific Islands)

Search and rescue behind enemy lines

Evacuation of downed airmen and wounded soldiers

It marked the birth of rotary-wing combat aviation, laying the groundwork for future helicopters like the UH-1 and AH-64.

🔧 Legacy
Although only 131 units were produced, its impact was enormous.

It became the first helicopter used in active military missions, proving that rotary-wing aircraft had a vital role on the battlefield.

Its creator, Igor Sikorsky, went on to become a pioneer in global helicopter development.






📊 Sikorsky R-4 (XR-4) Specifications
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| **Parameter** | **Value** |
| ---------------------- | ---------------------------------- |
| **Type** | Light military utility helicopter |
| **First flight** | January 14, 1942 |
| **Production years** | 1942–1944 |
| **Crew** | 1 pilot + 1 observer/passenger |
| **Length** | 33 ft 7 in (10.2 m) |
| **Rotor diameter** | 38 ft (11.6 m) |
| **Height** | 12 ft 5 in (3.8 m) |
| **Empty weight** | \~1,800 lb (820 kg) |
| **Max takeoff weight** | \~2,900 lb (1,315 kg) |
| **Engine** | Warner R-550-3 (7-cylinder radial) |
| **Power output** | \~200 hp |
| **Max speed** | \~75 mph (120 km/h) |
| **Range** | \~130 miles (210 km) |
| **Service ceiling** | \~8,000 ft (2,440 m) |
| **Drive** | Single main rotor + tail rotor |
| **Landing gear** | Fixed (tricycle type) |