Focke-Wulf Fw 61 / Fa 61 Experimental Helicopter / Technology Demonstrator
The Focke-Achgelis Fw 61 helicopter served Germany well as a technology demonstrator - two were built prior to the war.
Authored By Staff Writer; Content ©www.MilitaryFactory.com
The autogyro is a unique breed of air vehicle that more a fixed-wing aircraft than true helicopter. The main rotor set above the autogyro system is a free-spinning element used to generate lift while a traditional engine-and-propeller arrangement actually drives the vehicle forward. As such, autogyros typically do land nor take-off vertically as a helicopter can. The concept was brought to the forefront during 1923 when Spanish engineer Juan de la Cierva introduced to the world his "Autogiro". He later joined forces with industrialist James George Weir to develop the concept under the Cierva Autogiro Company brand label and the design was licensed globally.
The autogyro concept evolved during the latter half of the 1920s and into the early part of the 1930s. Henrich Focke of Focke-Wulf fame - makers of the classic World War 2-era Fw 190 fighter - undertook license-production of the Cierva Model C-30 during the inter-war period and this experience led him to consider a helicopter design to do away with the limitations inherent in the autogyro - taking off and landing vertically - a key limitation of the Cierva autogyro and its kind. In 1932, he teamed with Gerd Achgelis to forward such a product and this work begat Fw 61".
To streamline development, the Fw 61 relied on the existing airframe of the Fw 44 "Stielglitz" ("Goldfinch") biplane trainer. This aircraft proved itself popular on the global stage as it was adopted by a plethora of operators form Argentina to Yugoslavia and saw six major versions appear during its production run. The Fw 61 retained the fixed wheeled undercarriage of its predecessor as well as its single-finned tail unit. The engine was fitted forward of the open-air cockpit and drove a two-bladed propeller unit as normal. A key change to the original biplane design included deletion of the biplane wing arrangement and, in its place, was installed a strut network outboard of the fuselage sides. These structures mounted three-bladed main rotors of 23 foot diameter. Another change was a small horizontal plane attached to the very top of the tail fin and an anti-tipping device was fitted under the nose. The aircraft would be powered by a single Bramo Sh.14A seven cylinder radial piston engine of 160 horsepower. The Fw 61 exhibited an overall length of 24 feet with a height of 8.7 feet.
Finalized and completed, first flight of Prototype 1 (V1 D-EBVU) was on June 26th, 1936 and the aircraft eventually caught the attention of the RLM (the German Air Ministry) who commissioned for a second prototype as "V2 D-EKRA". This was completed and followed into the air during 1937. The vehicles were used in a myriad of tests and showcased at various events while collecting several aviation records during its time in the sky. For its career, the Fw 61 served primarily as a technology demonstrator and was never adopted for serial production - so just the two prototypes were all that was ever built.
Performance specifications were a maximum speed of 70 miles per hour, a cruise speed of 55 miles per hour, a range out to 145 miles and a service ceiling of 11,245 feet. Rate-of-climb was 690 feet-per-minute.
Interest in helicopters continued for Focke-Wulf for, in 1937, the Focke-Achgelis brand label was established for developing such products with increased performance and stability to undertake real-world assignments - both military and civilian. The company was able to deliver several short-lived helicopter designs during World War 2 beginning with the Fa 223 transport (20 produced) and ending with the Fa 336 prototype of 1944. No doubt the German military took a serious interest in the helicopter concept before their defeat - envisioning such aircraft in roles like submarine/ship spotting, air-sea rescue, aircraft recovery, MEDEVAC, and as supply mule to mountain troops. However, few were used operationally and these in very limited numbers.
Flettner also delivered several helicopter concepts for German military use during this period and their contribution can be found on this site as well.
One of the more interesting Focke-Achgelis helicopter projects became the Fa 269, a VTOL point defense fighter considered by the RLM before the end of the war. None were built but considerable work went into the project before it was cancelled including full-scale mockups and components. Much was lost in an Allied air raid which delayed the program and forced its cancellation.