Worthy of a Prince; The Royal Siamese Air Service Paribatra (Boripatra)

January 18, 2023

The Kingdom of Siam, today better known as Thailand, had a somewhat precarious existence during the age of European colonialism. Sandwiched as it was between the empires of France in Indochina and Britain in Burma, Siam saw its position as a regional power diminished in the face of the expansion of European domains in the 19th century, and the Thai’s gradually saw more and more of their territories annexed by the Imperial powers

This led to an appreciation, much like Japan at the same time, that the country would need to modernise rapidly if it wasn’t to be swallowed up like its neighbours. The upper echelons of Thai society went abroad to receive their educations and returned full of ideas on how to modernise their feudal state into a modern country. They also came back with a keen appreciation of the effectiveness of modern technology and in particular, the new weaponry being churned out by industrialised countries.

And one of the concepts they seem to have really liked was the value of air power. The Kingdom of Siam was a very fractious place with poor communications across much of the country and many of the regions being independent kingdoms only a few years before. Air power therefore provided a natural solution to enforcing the King’s authority over far flung provinces and in providing a deterrent to avaricious imperial powers.

So it isn’t that surprising that the Air Service of the Royal Siam Army was established as early as 1913, one of the first such forces to be created in Asia. Thai aviators would go on to be sent to France during the First World War where, though they wouldn’t see much action, they benefitted from considerable amounts of training provided by their French counterparts.

All this meant that at the end of the war in 1918, Siam had a surprisingly large body of well-trained military aviators on hand plus access to the large quantities of surplus aircraft being sold off at bargain rates.

One of the first major purchases the Thai’s made was of Bréguet 14 bombers from France.

This was a competent aircraft that had performed well in the latter half the war, and which would prove a popular aircraft with many air forces throughout the 1920s.

But the Thai’s recognised that, with France one of the potential threats to their security, they needed to be able to build their own aircraft. They also had a limited budget and it was thought that it would be cheaper in the long run to build their own aircraft as the Thai’s had ambitious plans to build considerable quantities of aircraft.

They proceeded to acquire a licence to build the Bréguet and put it into production as the Bomber Type 1 at a new facility located north of Bangkok; the Air Service’s Aeronautical Workshops. Here much experimentation was conducted to find local woods that could be used to replace European supplied ones, with some success, but the issue of sourcing aero parts made from metal alloys was one that the limited Thai industry of the day couldn’t resolve. This came to a head in 1927 when the company that supplied the Renault engines that the Thai-built Bréguet’s used suddenly increased the price.

Initially thought was given to fitting a different engine to the Bomber Type 1’s, but it was also recognised that things had moved on and instead it might be better if the Thai’s designed and built their own aircraft. This may seem an ambitious ask for a country with a very limited industrial base as Siam had at the time, but credit where credit was due, they succeeded.

Designed by Lt. Col. Luang Vejayan Rangsrit, who would go on to become head of the Air Force, the new aircraft was designated as the Bomber Type 2.

 

But it was more generally known as the Paribatra (pronounced in English as “Boripat”) after the Minister of Defence at the time, who was also a prince of the royal household and a major driver in updating the Thai military.

The new aircraft was a single-bay, equal-span biplane of mixed construction, with a metal skin fitted to the front of the fuselage and doped fabric on the rear, wrapped around a fuselage composed of a framework of steel tubing. This was the same technique used in the construction of the Bréguet 14, though the Paribatra utilised a more rounded and streamlined appearance in contrast to the rather boxy French aircraft.

Probably because of the use of a familiar construction technique development was surprisingly fast, with the first aircraft beginning construction on the 5th April, 1927 and making its first flight only about ten weeks later on June 23rd.

A two-seater like its predecessor, the Paribatra was armed with two machine guns and could carry a small bombload of 150lb (68kg). In fact, this light payload shows the true purpose of the Paribatra, which was to serve as an experimental type to test the capabilities of the Air Service Workshop and to act as an engine testbed. As a result, the Paribatra never had a standard engine fit, and the limited sources are contradictory as to the order in which aircraft were built with what engine, but the various Paribatra’s were fitted with BMW VI inline engines, Curtiss D-12s and ultimately the Bristol Jupiter VI radial.

This seems to have become the primary standard after the aircraft was declared operational with the Air Service in 1928 and, according to the Royal Thai Air Force Museum, this engine produced 465hp and gave the Paribatra a top speed of 157mph (253km/h), which was 30% faster than the Bréguet. The Paribatra was therefore a pretty advanced aircraft for its day, and certainly a step up from its predecessor.

 

The Thai’s were certainly keen to demonstrate their new indigenous aircraft, and in December 1929 three were dispatched on a goodwill visit to British India. Unfortunately, the long multistage trip seems to have been too much of a test for the aircraft and their crew, and two were lost, though the final one made it successfully to Delhi and, assumably, back again. This was followed the next year by a visit to French Indochina, which seems to have gone off without a hitch.

Indeed, it seems that the Thai’s hoped that they could build the aircraft in enough numbers to become their new attack and reconnaissance aircraft. But that wasn’t to be.

The issue mainly stated for this in histories of the aircraft is cost. Apparently when the French engine supplier found out about the development of Paribatra and, more specifically, that it didn’t use their powerplant, they had a change of heart and decided to drop the price of the Renault inline that the Thai’s had been using in their production of the licensed Bréguet 14.

Funny that.

As a result, it suddenly became much more economical for the Thai’s to resume construction of the older aircraft design and, considering that they had hopes for building a substantial air force, this was an important consideration.

However as said, that is the generally cited reasoning, but I suspect there may be another factor involved that gets overlooked. In 1932 a coup was staged against the Thai monarchy that ended the absolutist rule that had endured for centuries.

But notably, though the king was allowed to retain his throne and remained the head of state, his half-brother, the afore mentioned Prince Paribatra, was exiled to the Dutch East Indies and never allowed to return while alive.

So, it is entirely likely that fielding an aircraft named after a figure who seems to have been a reason for the launching of the coup was, understandably, unacceptable. Considering Paribatra’s influence in other Thai military endeavours, plus his name being used for the aircraft I do wonder if he may have played more in the decision to create it than is recorded, and this damned the design in the eyes of the new officialdom by association, though that is speculation on my part. If so though, that would once again be a factor in the choice to not pursue further construction and development of the aircraft.

Because in fact the Thai’s were by this point well aware that the Bréguet 14 was obsolete and needed replacing, and they did not build anymore of the type despite the drop in engine price. Instead they began to look around for another aircraft to build as a replacement, and eventually settled on the Vought Corsair, which was built in some numbers by the Thai’s.

As for the Paribatra’s, the exact number built appears to be unknown, though likely less than a dozen. These served until 1940, according to the Thai Air Force, and appear to have all been scrapped or junked at some point during the Second World War. A somewhat sad end for a rather interesting aircraft that was, after all, Thailand’s first indigenously designed and built aircraft.

But at least the Thai’s later realised the significance of the type and in the 1980s built a couple of replica’s, which seem pretty faithful to the real thing, and these are currently on open display at the Royal Thai Air Force Museum in Bangkok.

Sources/Related:

https://en.wikipedia.org/wiki/Boripatra

http://www.aeroflight.co.uk/waf/aa-eastasia/thailand/thai-manu-history2.htm

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