SI VIS PACEM, PARA BELLUM: Lo Yakovlev Yak-23 (in cirillico Яковлев Як-23, nome in codice NATO Flora)

Lo Yakovlev Yak-23 (in cirillico Яковлев Як-23, nome in codice NATO Flora) era un monomotore a getto da caccia ad ala dritta progettato dall'OKB 115 diretto da Aleksandr Sergeevič Jakovlev e sviluppato in Unione Sovietica negli anni quaranta.

Sviluppo del precedente Yak-17, venne impiegato negli anni successivi principalmente dalla Sovetskie Voenno-vozdušnye sily (VVS), l'Aeronautica militare dell'Unione Sovietica, e da alcune forze aeree degli stati aderenti al Patto di Varsavia, rimase operativo dal 1949 ai primi anni sessanta.

Storia del progetto

Lo Yak-23 fu progettato su iniziativa della Yakovlev per essere una caccia a getto semplice e leggero in grado di utilizzare le piste di aeroporto esistenti, contenendo la corsa di decollo e atterraggio. Era il risultato dello sviluppo dei precedenti caccia modelli Yak-15 e Yak-17, dai quali ereditava l'architettura non convenzionale con il motore a getto installato nel naso e lo scarico al di sotto del cockpit detta "redan" (a scalino). L'aereo adottava un'ala dritta derivata dallo Yak-19m a differiva per la presenza di piani di coda orizzontali e timone maggiorati. Era motorizzato con una copia sovietica del motore britannico Rolls-Royce Derwent V, prodotto con il nome Klimov RD-500 ed effettuò il primo volo l'8 luglio 1947, cui seguirono i collaudi di accettazione nel 1948. Fu approvata la produzione in serie che cominciò nella tarda primavera dello stesso anno. Fu valutato come aereo estremamente maneggevole con una buona accelerazione, corsa di decollo e prestazioni in salita grazie all'alto rapporto spinta-peso. Manifestava come difetti una scarsa stabilità direzionale a velocità intorno a Mach 0,86 e la mancanza di una cabina pressurizzata.

Malgrado fosse uno dei migliori jet da caccia ad ala dritta, risultò inferiore agli emergenti nuovi progetti con ala a freccia e i due soli reggimenti della VVS sovietica che avevano ricevuto il caccia di Yakovlev nel 1949, lo sostituirono con il MiG-15 nel 1951, relegando il Flora alla esportazione e alla costruzione su licenza nei paesi del Patto di Varsavia. La produzione totale in Russia terminò nel 1950 e fu di 310 esemplari.

Varianti

Yak-23 - versione da caccia costruita in serie.
Yak-23UTI - addestratore biposto con fusoliera più lunga e armamento più leggero, rimasto allo stato prototipo.
Yak-23DC - versione da addestramento biposto prodotta in Romania. Quattro Yak-23 monoposto furono convertiti nel 1956 dalla ASAM Pipera. Due appartenevano alla Aeronautica bulgara.
S-101 - denominazione cecoslovacca.

Utilizzatori

Albania Forcat Ajrore Shqiptare
Bulgaria Balgarski Voennovazdushni Sili - 12 aerei nel 1949.
Cecoslovacchia Češkoslovenske Vojenske Letectvo - 12 "S-101" nel 1950.
Polonia Siły Powietrzne - 95 aerei impiegati tra il 1950 e il 1961.
Romania Forțele Aeriene Române - 62 aerei nel 1951, impiegati fino al 1958.
Unione Sovietica Sovetskie Voenno-vozdušnye sily - 2 reggimenti operativi dal 1949 al 1951.
Stati Uniti United States Air Force - 1 aereo nel novembre 1953 utilizzato per prove di volo.

Esemplari attualmente esistenti

due Yak-23 con marche 14 e 52 sono conservati al Museo dell'aviazione di Bucarest.

ENGLISH

The Yakovlev Yak-23 (Russian: Яковлев Як-23; USAF/DoD reporting name Type 28, NATO reporting name Flora) was an early Soviet jet fighter with a straight wing. It was developed from the Yak-17 in the late 1940s and used a reverse-engineered copy of a British engine. It was not built in large numbers as it was inferior in performance to the swept-wing Mikoyan-Gurevich MiG-15. Many Yak-23s were exported to the Warsaw Pact nations and remained in service for most of the 1950s, although some were still in use a decade later.

Development and description

On 11 March 1947, the Council of People's Commissars ordered several design bureaux (OKB), included that of Alexander Yakovlev, to develop a single-seat, straight-winged jet fighter to be equipped with a single British Rolls-Royce Nene or Rolls-Royce Derwent turbojet engine. The aircraft should have a maximum speed of 950 kilometers per hour (590 mph) at sea level and a speed of 1,000 km/h (621 mph) at an altitude of 5,000 meters (16,400 ft). It should be able to climb to that altitude in 3.5 minutes or less and should have a maximum range of no less than 1,200 kilometers (750 mi). Alexander Yakovlev decided to develop two designs, the Yakovlev Yak-25 in accordance with the Ministry's order and a lightweight, more agile aircraft (the Yak-23) in the hopes that one or the other would win an order from the Ministry. Yakovlev's decision was a risky one as it could be construed as unauthorized use of state monies if discovered, which could have landed Yakovlev in a lot of trouble.

To minimize risk, the new aircraft used the same "pod-and-boom" layout as the earlier Yak-17 fighter, but the metal fuselage was redesigned as a semi-monocoque structure with the single-seat, unpressurized cockpit and its teardrop-shaped canopy positioned just above the trailing edge of the wing. Not coincidentally, this was also above the exhaust of the 1,590-kilogram-force (15.6 kN; 3,500 lbf) centrifugal-flow Klimov RD-500 engine, an unlicensed copy of the Derwent V. Fitted with tricycle landing gear, the main landing gear retracted inwards into the fuselage while the nose gear retracted forwards. Unlike the installation in the Yak-17, the Yak-23's forward landing gear was flush with the fuselage when retracted. The laminar-flow, two-spar, wing was mounted in the middle of the fuselage. It was equipped with slotted flaps and ailerons and had a modest 3° 30' dihedral. The horizontal stabilizers had 5° of dihedral. The pilot was protected by a bulletproof windscreen and the armored back of the ejection seat. The Yak-23 was equipped with five non-self-sealing fuel tanks in the fuselage that had a total capacity of 910 liters (200 imp gal; 240 U.S. gal) of fuel. In addition it could carry a pair of 195-liter (43 imp gal; 52 U.S. gal) drop tanks under the wingtips. The fighter was armed with two 23-millimeter (0.9 in) Nudelman-Rikhter NR-23 autocannon, each with 90 rounds.

Two prototypes and a static-test airframe were ordered and the aircraft first flew on 8 July 1947 with the Hero of the Soviet Union, Lieutenant Colonel Mikhail Ivanov, at the controls. While still involved in its manufacturer's flight testing, the first prototype participated in the flypast at Tushino Airfield on 3 August. The Yakovlev OKB concluded its testing on 24 September and turned over the second prototype for state acceptance trials on 22 October. Although the Yak-23 was accepted for series production, it was criticized of heavy aileron and rudder forces, lack of cockpit pressurization and heating and ventilation, protection for the pilot and weak armament. The test pilots did praise it as highly maneuverable, with a good acceleration and takeoff and climb capabilities thanks to a high thrust-to-weight ratio. The second prototype was modified afterwards to address some of these issues and successfully tested again in 1948. 

Operational history

The first aircraft were produced in a factory in Tbilisi in October 1949. In late 1949 they entered Soviet air force service. The Yak-23 was quickly replaced in the Soviet service with the more complicated swept-wing MiG-15, which offered superior performance. In all, only 316 Yak-23 aircraft were built before production ended in 1951. Apart from the fighter there were two trainer versions of the Yak-23 which were built in small numbers. The Yak-23UTI two-seat trainer which appears to have had the unusual arrangement of having the instructor seated in front of the student, and the Yak-23DC trainer which was produced in Romania.

Small numbers of Yak-23s were exported to Czechoslovakia (20 from 1949, named S-101), Bulgaria (from 1949), Poland (about 100, from 1950), Romania (62, from 1951). Poland and Czechoslovakia acquired licenses for the aircraft, but built the superior MiG-15 instead. Yak-23s were withdrawn by the late 1950s, except in Romania which used them for another decade.

U.S. testing

A single Yak-23 was acquired by US intelligence via Yugoslavia in November 1953. The aircraft was a Romanian Yak-23 flown by Mihail Diaconu who had defected with it. The aircraft arrived disassembled and was shipped to the U.S. Air Force Test and Evaluation Center at Wright Field near Dayton, Ohio. It was reassembled and made operational for several test flights, during which time it was disguised with U.S. markings. Efforts were made to keep the aircraft's identity secret and it was flown only in the early morning. On one occasion it was passed on the runway by a formation of F-86 Sabres whose pilots inquired as to the plane's identity. A story was conceived that the aircraft was a Bell X-5, which had a similar layout. At the completion of design and flight evaluations the aircraft was again disassembled and shipped quietly back to Yugoslavia in its original paint scheme.

Records

On September 21, 1957, the Polish pilot Andrzej Abłamowicz set two FAI world records in the Yak-23 with civilian markings SP-GLK, in its weight class, climbing to 3,000 m (9,843 ft) in 119 seconds (4,962.6 ft/min) and to 6,000 m (19,685 ft) in 197 seconds (5,995.4 ft/min). This plane was withdrawn in 1961.

Variants

Yak-23: Fighter version, serial built.
Yak-23UTI: Two-seat training version with longer fuselage and lighter armament, three built.
Yak-23DC: Romanian-built two-seat training version. Four Yak-23 single-seaters were converted in 1956 by ASAM Pipera, two of them belonging to the Bulgarian AF.
S-101: Czechoslovak designation.

Operators

Albania Albanian Air Force - The first aircraft was received in 1951.
Bulgaria Bulgarian Air Force - Received over 100 aircraft, used them until 1958.
Czechoslovakia Czechoslovak Air Force - Received 20 aircraft in 1949.
Korean People's Army Air Force - A small number were used in the Korean War.
Poland Polish Air Force - Received about 100 aircraft operated between 1950 and 1956.
Romania Romanian Air Force - Received 62 aircraft in 1951 and used them until the late 1960s.
Soviet Union Soviet Air Force - Operated aircraft between 1949 and 1951.

Specifications (Yak-23)

General characteristics

Crew: 1
Length: 8.13 m (26 ft 8 in)
Wingspan: 8.73 m (28 ft 8 in)
Height: 3.31 m (10 ft 10 in)
Wing area: 13.5 m2 (145 sq ft)
Empty weight: 1,980 kg (4,365 lb)
Gross weight: 3,384 kg (7,460 lb)
Powerplant: 1 × Klimov RD-500 centrifugal-flow turbojet engine, 15.6 kN (3,500 lbf) thrust.