The concept of the Airacobra fighter aircraft was innovative and imaginative in many aspects, which initially led to high hopes. The Airacobras had a layout that was highly atypical at the time, with the Allison engine located behind the cockpit to make room in the nose for the large 37 mm calibre T9 cannon manufactured by Oldsmobile. The empty nose also allowed for the installation of an innovative three-wheel undercarriage.
Big Sting
Today we will focus on the T9 cannon.
The film shows a 37 mm cannon firing through the spinner of two different early Airacobras – first, armed with two 0.5-inch guns above the cannon (probably in the D or D-2 version), then the C version, armed with 4 guns above the cannon (two 0.50 inch and two 0.30 inch)
Advantages and disadvantages
This arrangement had many advantages. The tricycle undercarriage made taxiing significantly easier.
Cartoon from original Airacobra’s pilot’s manual
Placed near the centre of gravity, the engine should have theoretically increased manoeuvrability. Finally, the 37 mm cannon with fragmentation ammunition had devastating firepower. However, the P-39 also had significant drawbacks. The cannon fired slowly, with a steep trajectory, and was not suitable for use in high-speed duels with enemy fighters, where there was insufficient time for accurate aiming. To make matters worse, it was notorious for jamming after firing off two or three rounds – a feature that regularly made it unusable.
Allison engine placed behind Airacobra’s cockpit
Engine and transmission. Cannon is removed
The atypical arrangement, with power being transmitted from the drive to the propeller through the entire fuselage, resulted in there being little space in the fuselage. Thus, the XP-39 prototype’s canopy protruded quite high above the fuselage outline. During testing, it was decided to lower the canopy to reduce drag. As a result, the cockpit of the P-39 became very cramped, even claustrophobic. It soon became apparent that only pilots of very short stature could serve in squadrons equipped with Airacobras. Those were taller simply could not push themselves into the cockpit.
Engine with transmission and cannon – photo gallery
At the National Museum of the United States Air Force in Dayton, Ohio, there is an Allison V-1710-85 engine dismantled from a P-39Q Airacobra with an exposed T9 37 mm cannon installation. Wojtek Łuczak photographed this extraordinary exhibit and agreed to share his photos. Welcome to the gallery!
And it all shot like this:
In the material I used fragments of Tomasz Gronczewski’s text about the Airacobra P-400, which we will publish soon!
Buy Airacobra model kit online directly at Arma Hobby store!
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Modeller, son and father of a modeller. Loves digging through references and analysing old photographs. He builds aircraft, ship and vehicle models, the older the better. He has a weakness for Polish equipment, but does not despise the RAF, FAA and Great War topics. A journalist by training.
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