Development, construction and flight testing of the N-20.1

The development of the N-20.1 glider started 24.März 1947. The document outlines the objectives, dimensions and weight together with the expected costs to build the aircraft.

One of the first drawings shows the characteristic lines of the fuselage and wing together with the slats and the solid rocket motor in the tail.

The indicated ballast tanks were not realised. The tandem nose wheel was replaced by a DH-100 nose gear. The observer seat was built but did not come into use.

The fuselage structure is built from frames, longerons and a semi carrying wood skin. The curved lines make for some rather challenging work.
The missing tail section was built from sheet metal and attached to the main section at a later stage.

The wing was completely made of wood and built in one single piece. Both main spars are curved and lead through the fuselage section.

The massive wing core section, the elevons, trim flaps, and the already installed main landing gear are prominently visible.
Notice the position of the landing gear in front of the forward main spar.

The entire building process of the aircraft is described in detail in the document FO-0233.

Some of the building process was recorded.

In January 1948, after only 8 month building time, the aircraft was completed. The entire aircraft was then put into the wind tunnel for initial evaluations.

Notice the exhaust of the soild rocket motor, the slats and the trim flaps.

Recordings of the aircraft in the wind tunnel.

Amongst all the comprehensive wind canal experiments the flutter characteristic was looked into seriously too.

Recoring of the first roll out and life firing test of the solid rocket motor.

The purpose of the solid rocket motor was to accelerate the aircraft to its maximum designed speed for spin recovery during flight testing.

It proved helpfull for initial take off runs as well.

The first flight took place on  17. April 1948.

Towed by a C-36 aircraft it was led to a point on final approach at 50m above ground and then released. After a short gliding phase the aircraft landed safely. Total flight time: 12 minutes.

 

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During further test flights the release altitude was increased. The manouver and speed envelope was gradualy extended.

On 26. Juni 1948 the canopy detached while in tow for test flight. The subsequent approach and landing under these conditions resulted in a collapsed nose landing gear and the aircraft nose section being damaged. 

Total flight time at this point: 6 hrs 34 min.

The aircraft was repaired and put back into service in record time.

The flight testing phase continued with release altitudes up to 6000 meters above sea level and consequently longer gliding times. The landing gear was retracted allowing the speed and manouver enveloppe to be extended further.

The landing gear retraction and extention didnt’ exactly work as advertised. A strong rattling developped from the worm gears. Besides the electric motor cut out due to overload and the clutch showed overheat symptoms.

A number flights were performed with the canard wings installed, with unanticiptated results.

On 1. Juli 1949 the aircraft developped overcontrol issues during final approach, landed short of the runway and was damaged beyond repair.
The total flight time at this point was  30hrs 18min.
(Gliding time 7hrs)

Accident report in detail