The P.Z.L. P.24 was a refined version of the P.11 designed to use engines other than Bristol radials, so they could be exported without causing problems with the licensing agreement for those engines.
The original P.Z.L. P.1 had been designed by Zygmunt Pulawski, and made its maiden flight in 1929. It was a gull wing monoplane, with a fixed ‘scissors’ undercarriage. The gull wing was adopted to improve the pilot’s view – the more familiar parasol wing configuration gave a good view down, but blocked the view up, so Pulawski removed the central section of the wing, and replaced it with inner panels that sloped down from the wing to the sides of the fuselage. The P.1 greatly interested the Polish air force, but they didn’t want to use it’s inline engines, so the first production version, the P.Z.L. P.7, was powered by radial engines built under licence in Poland. It was soon followed by the P.11, which would be the main Polish fighter when the Germans invaded in 1939.
The P.11 was powered by Bristol radial engines produced under licence in Poland, but the terms of the licence meant that no Polish manufactured Bristol engines could be sold abroad, and the company could investigate the sale of Polish aircraft using Bristol engines from other sources. As a result in 1932 Wseiwolod Jakimiuk at P.Z.L. began to work on a separate version of the aircraft that could take other radial engines, starting with the new 700hp Gnome-Rhone 14Kds radial. Gnome-Rhone were very interested in the idea, as they needed a suitable aircraft to try and win a fighter contract in France. As a result in 1932 they offered to provide up to 150,000 francs, a free engine and sponsor any P.Z.L. entry in the French fighter contests.
In June 1932 Gnome-Rhone was asked to deliver a 760hp Kds fourteen cylinder two-row supercharged radial engine. Work on three prototypes began in July 1932. The engine was due to arrive in December, but was three months late, and arrived without the three-blade medal airscrew that was meant to have come with it.
The P.24 was similar to the P.11, but with some changes. It was designed to carry heavier armament with space for two 20.mm Oerlikon FF cannon mounted at the strut support in the wings and could carry, two or four machine guns or two cannon and two machine guns. The radial engines used on all production examples of the Pulaswki fighter reduced the forward view, so on the P.24 the engine was lowered, the pilot’s seat was raised and moved backwards and the inner sections of the wings altered to reduce the size their impact on the view.
The first prototype, P.24/I, was ready by January 1933 but didn’t make its maiden flight until May because of the late delivery of the new engine. When it did fly it was using a two-blade fixed pitch wooden airscrew produced by Szomanski. The maiden flight wasn’t a great success – after a few minutes the hub fairing on the airscrew broke, smashing the airscrew. The pilot, Captain Boleslaw Orlinski, managed to land the damaged aircraft, but the entire forward fuselage needed re-working. Flight tests resumed in October 1933, this time with the Gnome-Rhone three-blade metal airscrew. The 20mm cannon mount also broke during firing trials.
The second prototype, P.24/II, was known as the Super P.24. Over 150 modifications were made to this aircraft after the tests with /I, including a new NACA engine cowling, a chance to the cooling and exhaust systems, and a stronger cannon support. It was also powered by a 760hp 14Kds radial engine, and made its maiden flight in March 1934 when it reached just over 248.5mph in level flight. On 28 June the same aircraft reached a speed of 257.2mph, breaking the FAI International Speed Record for radial powered fighters.
The third prototype, P.24/III, also known as the Super P.24bis, was given a new 930hp Gnome-Rhone 14Kfs radial after the French company finally agreed to deliver one. This engine arrived in July 1934 and made its maiden flight in August. Towards the end of the year it was shown at the Salon de l’Aeronautique in Paris. During the show it was armed with two 20mm cannon and two machine guns, and was touted as being the best armed and fastest fighter in the world. However no French order was received, where more advanced low-wing fighters were soon about to enter service. However several other countries were interested in the type.
The prototypes were followed by a batch of six pre-production P.24s with work beginning in the spring of 1935. These aircraft had enclosed cockpits but with open side windows, highest aspect ratio wings, a new tail identical to that used on the P.11c, an new exhaust system and with the armament entirely carried in the wings. These aircraft were then used to test out different combinations of armaments and engines and as sales models.
The first order was placed by Turkey, and included fourteen P.24As and twenty six P.24Cs. The P.24A was to be armed with two Oerlikon FF cannon and two 7.9mm Colt-Browning machine guns and racks for four 22lb bombs, two under each wing.
The P.24B was developed in response to a Bulgarian order, and was armed with four 7.92mm machine guns and racks to carry four 22-27.5lb bombs. Fourteen P-24Bs were delivered to Bulgaria. Greece also ordered six P-24Bs, but they were delivered as the improved P.24G.
The P.24 was armed with four 7.9mm Colt-Browning machine gins and two 110lb bombs below the wings. Some of the P.24Cs were produced with some minor aerodynamic improvements after they failed to achieve the expected speed. Twenty four were delivered to Turkey and twenty to Bulgaria.
The P.24E was produced to satisfy a Romania order, with most examples built by I.A.R. in Romania. It was to be powered by a licence built version of the Gnone-Rhone 14K engine, produced at I.A.R. Six were built in Poland, but using 900hp I.A.R. 14KIIc32 engines built in Romania. The first licence built aircraft used the same engine, before production switched to the 940hp I.A.R. 14KMc36 engine. The earlier versions had a top speed of 253.6mph at 14,763ft. The P.24E was armed with two cannon and two machine guns.
The P.24F and P.24G were improved versions of the P.24A and P.24B, built around a new Gnome-Rhone 14N radial engine, which provided more power but with a smaller diameter. A new airscrew spinner with built in cooling louvers was used, and an air filter installer over the coolant intake. The wing inner section was modified and the forward fuselage was improved aerodynamically. The cockpit was given 35mm armoured glass and some armour for the pilot.
The P.24F was powered by the 970hp Gnome-Rhone 07, and was armed with two 20mm cannon and two machine guns. It entered production late in 1937.
Twenty five were produced to complete the Greek order. Twenty six were ordered by Bulgaria, of which all but four were delivered before the German invasion of Poland.
The P.24G had the same improvements as the P.24F, but was armed with four machine guns.
Six were produced under the Greek order.
At first the Polish air force had no interest in the P.24, which had no significant advantages over their existing P.11s. However by 1938 a large armament loan from France made the purchase of the Gnome-Rhone radial more affordable, and in the spring of 1939 an order was placed for seventy P.24Hs. These would have been armed with 1,050hp Gnone-Rhone 14N21 radials, and armed with either two 20mm cannon and two 7.7mm machine guns or just two 20mm cannon. It was expected to reach a top speed of 285.8mph. However the plans were probably cancelled in August 1939 in favour of the P.45A Sokol. Although none of these aircraft were ever produced, one P.24 did take part in the fighting in September, claiming two victories towards the end of the campaign.
The first order was placed by Turkey, in the middle of 1936. They ordered forty aircraft to be built in Poland and partly prepared parts for another twenty, which would be built in Turkey. The Polish built aircraft were split between fourteen P.24As (two cannon, two machine guns) and twenty-six P.24Cs (four machine guns). Deliveries began late in 1936 and ended in the summer of 1937. The twenty aircraft to be built in Turkey were apparently completed as six P.24Fs and fourteen P.24Gs. As many as 100 aircraft may have been built in Turkey, and they remained in service into the post-war period.
The second order came from Greece and was originally for a small number of the P.24A. This was soon changed to one for thirty-six aircraft, with a mix of thirty P.24As and six P.24Bs. However only five P.24As were built before the rest of the order was switched to the twenty five of the improved P.24F and six P.24Gs.
When the Italians invaded Greece on 28 October 1940 the Greeks had 36 P.24s, nine Bloch MB-151s and two Gloster Gladiators. The P.24 was used by Nos.21, 22 and 23 Squadrons, which helped fight off the more numerous Italian air force. Twenty of the P.24s were still available when the Germans invaded in April but they had finally met their match, and only a handful survived to try and escape to Egypt.
Bulgaria was the third country to place an order, starting with one for fourteen P.24Bs (four machine guns). These were delivered early in 1938. It was followed by an order for twenty P.24Cs to be delivered by the end of 1938 and a third order for twenty-six P.24Fs, to be delivered by September 1939. The last four of these aircraft were still in Poland when the Germans invaded and were damaged in a German raid on the P.Z.L. factory.
Late in 1936 Romania purchased six pattern aircraft and a licence to build the aircraft in Romania. All of these aircraft were of the P.24E variant. At least 40 of these aircraft were produced in Romania, starting in 1937. These aircraft and the earlier P.11fs were used against the Russians on the Eastern Front, and some were reported by US bomber crews into 1944.
P.24A, B and C
Engine: Gnome-Rhone 14 Kfs
Span: 35ft 2.5in
Length: 24ft 7.5in
Empty Weight: 2,928lb
Loaded Wright: 4,079-4,167lb
Max loaded Weight: 4,409lb
Maximum Speed: 254.7mph at 14,763lb, 211.2mph at sea level
Climb rate: 6min to 16,404ft
Service Ceiling: 29,527ft
Range: 435 miles
Guns: See above
P.24F and G
Engine: Gnome-Rhone 14 N07
Span: 35ft 0.75in
Length: 24ft 11.5in
Height: 8ft 10.25in
Empty Weight: 2,937lb
Normal Loaded Weight: 4,221lb
Maximum Loaded Weight: 4,409lb
Maximum Speed: 267.1mph at 14,763ft, 214.3mph at sea level
Climb rate: 5min 40 sec to 16,404ft; 12min to 26,246ft
Service Ceiling: 34,449ft
Range: 435 miles
Guns: See above