Continuing our exploration of lesser-known Spanish aircraft from the interwar period,
we come to the González Gil-Pazó GP-1.
At the start of the 1930s Spain was faced with a bit of a challenge, it was trying to
modernise its armed forces, whilst also trying to cut costs owing to the financial difficulties
brought on by the great depression.
As the fighter aircraft of the Spanish air forces were to be upgraded, a new training
aircraft was required as well, but all of this had to be done on a tight budget.
To meet this requirement, two Spanish engineers, Arturo Gonzalez Gil and Jose Pazo, collaborated
to produce a single-engine, two-seat, monoplane training aircraft.
Both men already had experience in both flying aircraft and designing them, and they had
in fact already worked together on-and-off since they had first met in the 1920s.
Their work quickly produced a prototype, known as the GP No.1.
This was a low-wing cantilever monoplane, unfortunately no photos of it exist, so you’ll
have to bear with me using this basic graphic.
It had a mixed construction, primarily of wood aft of the cockpits, and mostly steel
framing going forward.
The control surfaces appear to have been fabric covered, with the majority of the wing covered
by a skin of plywood, and the fuselage appeared to be fabric covered, the exception being
the nose and engine which had a metal cowling.
With a loaded weight of 1715 lbs (777KG), and powered by a 90hp ADC Cirrus III engine,
it flew for the first time in June of 1932.
No production orders were forthcoming for this design, but when the Spanish government
renewed its requests for a new training aircraft in 1934, Gil and Pazo submitted an updated
design known as the GP-1.
Flown for the first time in July of that year, the GP-1 only had a few notable differences
from its predecessor.
It now had a faired undercarriage to reduce drag, the fuselage structure was now made
completely from steel, and the engine was replaced with a 195hp, 5.8 litre, Walter Junior,
which was an air-cooled 4-cylinder inline engine.
Like the GP No.1, the wings had a straight leading edge, and had semi-elliptical tips,
its unknown if the original came with split-flaps, but the GP-1 was specifically advertised in
having them.
The GP-1 was entered into a competition against three other designs, the Arado 1.E.7, the
Hispano HS-21, and the Loring X.
As the only monoplane submission, and with the highest top speed of 212 km/h (132 mph),
the GP-1 was the clear winner, and a production order was placed for 100 aircraft.
Construction was to begin at the Aeronautica Industrial S.A factory in Madrid, but the
outbreak of the Spanish Civil War curtailed this plan, and construction was instead completed
with the assistance of Hispano-Suiza, with approximately forty GP-1’s being built,
along with a couple of experimental models.
As built, the GP-1 had a wingspan of 11.6 meters (37ft 1 in) and a length of 8.5m (27
ft 11 in), the height of the aircraft is unknown.
Fully fuelled, it had a range of approximately 1000 km (620 miles), and it had a service
ceiling of 7,500 meters (24,600 feet) – though going up that high with a 195hp engine…in
an open cockpit was probably not a pleasant experience.
The GP-2 featured an enclosed cabin for up to two occupants, was powered by a 130hp De
Havilland Gypsy Major, and was famous for a couple of record-setting flights.
One of these was a non-stop journey from Madrid to the city of Bata in Equatorial Guinea,
completed at an average speed of 187 km/h.
The GP-4 was designed for up to four people, came with a new fuel system, had an improved
undercarriage design, and was powered by a 130hp Walter Major.
Only one GP-4 was built, and it signalled the end of the collaboration between Arturo
Gil and Jose Pazo.
The two men had opposing political views, Gil was a communist, and Pazo leaned towards
the nationalists.
After the GP-4 was impressed by the republicans in 1936, Pazo took exception to this, stole
it, and flew it to Nationalist-held territory.
After joining the Nationalists, Pazo took part in several aircraft projects before eventually
moving into other work; meanwhile Gil would not survive the civil war, being killed as
a foot soldier in the final year of the conflict.
As for the forty GP-1s that were built, details of their wartime service are nebulous at best.
However, around 30 survived to the end of the civil war and were put into service as
trainers with the nationalist air force, most of which joining Grupo 30.
Some of these remained in service all the way up to the mid-1950s, a considerably achievement
for such a lightweight design, and some others, sold into civilian hands, remained on the
Spanish civil register even longer, with at least two still being used in 1960.