The Junkers Ju 49 was a German aircraft designed to investigate high-altitude flight and the techniques of cabin pressurization.
It was the world’s second working pressurized aircraft, following the Engineering Division USD-9A which first flew in the United States in 1921.
By 1935, it was flying regularly to around 12,500 m (41,000 ft).
The Junkers Ju 49 was developed entirely to investigate techniques for flight at high altitude.
To this end, it had a specially developed engine and the first pressurized cabin in a German aircraft.
The engine was the Junkers L88a, which combined two six-cylinder inline L8 motors into an upright V-12 and had a two-stage supercharger plus intercooler to sustain power at high altitudes.
It produced 522 kW (700 hp) at about 5,800 m (19,000 ft).
This engine drove a large four-blade propeller.
The pressure cabin held the two crew.
The original intention was for operation at about 6,000 m (20,000 ft).
The Ju 49 was built in typical Junkers fashion as a cantilever-wing monoplane of all-metal construction with stressed duralumin skin throughout, corrugated on the flying surfaces.
The wing trailing edge featured the standard Junkers “double wing”, combining adjustable flap and aileron surfaces outboard, together with plain flaps inboard.
The aircraft had a fixed, split-axle main undercarriage which was noticeably tall, to accommodate the large-diameter propeller, plus a tailskid.
A retractable rectangular radiator descended between and just in front of the undercarriage legs.
The pressurized cabin had five small portholes for the pilot, two forward, two sideways and one overhead, and there were two more, one on each side for the second crew member.
The forward view was so poor that a periscope was fitted with a downward view for landing.
The supercharged engine was not cleared for use at the time of the first flight on October 19 and the Ju 49 used instead the unsupercharged L88 version.
Externally this installation was characterised by a tall, inline vertical stack of exhausts, unlike the single sloping pipe of the L88a.
By summer 1932, the supercharged engine was flight-ready and installed, and the research program proper began.
This was uneventful, with no serious engine or cabin problems.
Remarkably, given the initial target altitude of around 6,000 m (20,000 ft), by 1933 flights at 10,000 m (30,500 ft) were being made and by 1935 altitudes of 12,500 m (41,000 ft) were routine.
No absolute records were set, but the experience gained fed into later pressurized aircraft, particularly the Ju 86P bombers and reconnaissance machines.
Only one Ju 49 was built, carrying the civil registration D2688 and later (when German civil registrations changed from numbers to letters) D-UBAZ.
It ended its life at the German research centre (Deutsche Versuchsanstalt fur Luftfahrt) and crashed in October 1937.
