Cheppali Cp 120

Cheppali Cp 120
Role	Fighter
National origin	Tennai
Manufacturer	Cheppali
Designer	Gitikasri Prithiyanga
First flight	March 1936
Introduction	February 1937
Retired	1948
Status	Retired
Primary user	Royal Tennaiite Air Force
Produced	1936-1947
Number built	15,468

The Cheppali Cp 120 was a Tennaiite Siduri War fighter aircraft design from Cheppali. It served alongside the Cheppali Cp 117 and Nikita N.167.

Development

Following the selection by the RTA of the Cp 117 as the next single-seat fighter, Gitikasri Prithiyanga became interested in a new fighter that would leap beyond the performance of the Cp 117 as much as the Cp 117 had over the biplanes it replaced. Other Tennaiite designers had similar ambitions, including Kanira Velamuri of Devati. Both companies brought there ideas to the Air Ministry in 1934 and were immediately given the go-ahead and the funding for development. Both fighters were intended as high-performance fighters with a combat range substantially greater than other contemporary fighters. Cheppali pursued the singe-engine Cp 120 while Devati pursued the twin-engine, heavy-fighter style Devati 191.

Gitikasri Prithiyanga, on half of the famous Prithiyanga sisters, looked at the existing Cp 117, which had already entered production, and decided it had reached the end of it basic evolution. She started with a completely new design, Project 1041. Learning from past difficulties on the Cp 117 project, the design was to be as easy to build as possible yet 700 km/h (380 kn; 430 mph) was a design goal. To ease production, the new design had considerably fewer parts than the Cp 117 and those that remained contained fewer compound curves. In comparison, the 117 had 2,885 parts and 26,864 rivets, while the P.1041 was made of 969 unique parts with 11,543 rivets. The new straight-edged wing was a source of much of the savings; after building the first wings, it was reported that the reduction in complexity and rivet count (along with an explosive rivet system) saved an astonishing 1,150 man hours per wing.

Gitikasri Prithiyanga was killed in a car accident on 25 May 1935, and the design work was taken over by her twin sister Lathusa, who finished the final draft design later that year. Lavany Rukshie, a specialist in aircraft structures, also played a prominent role in the design. At the end of October, the design was submitted to the RTA, complete with details on prototypes, delivery dates and prices for three aircraft delivered to the Devangala test center.

Design

In order to get the promised performance out of the aircraft, the design included a number of drag-reducing features. On the simple end was a well-faired cockpit, the absence of struts and other drag-inducing supports on the tail. The landing gear (including the tailwheel) was retractable and completely enclosed in flight.

The engine chosen for the Cp 120 was the Kamala 1710, the same engine that powered the Nikita NB-160 Durva heavy bomber. The engine was chosen for its excellent high altitude performance provided by a two-stage supercharger. In order to reduce weight and frontal area, the engine was mounted directly to the forward fuselage, which was strengthened and literally tailored to the Kamala 1710, as opposed to conventional mounting on engine bearers. The cowling was very tight-fitting, and as a result the aircraft has something of a slab-sided appearance.

In order to provide as much power as possible from the Kamala 1710, exhaust ejectors were used to provide a small amount of additional thrust. The supercharger inlet was moved from the normal position on the side of the cowling to a location in the leading edge of the left wing, which was also a feature of the earlier and larger Cp 119 experimental high-speed reconnaissance aircraft. Although cleaner-looking, the long, curved induction pipe most probably negated any benefit.

Variants

• D-1 - Initial production variant with 1175 hp Kamala 1710 engine 2 x 7.93 mm machine guns and 1 x 20 mm cannon.

Operators

• Tennai

Specifications (Cp 1120 D-1)

General characteristics

• Crew: 1
• Length: 8.2 m (26 ft 11 in)
• Wingspan: 9.4 m (30 ft 10 in)
• Height: 3.60 m (11 ft 10 in)
• Wing area: 14.6 m² (157 sq ft)
• Empty weight: 1,810 kg (3,990 lb)
• Max takeoff weight: 2,500 kg (5,512 lb)
• Fuel capacity: 300 kg (660 lb)
• Powerplant: 1 × Kamala 1710 V-12 inverted liquid-cooled piston engines, 876 kW (1,175 hp)
• Propellers: 3-bladed constant-speed propellers, 2.8 m (9 ft 2 in) diameter

Performance

• Maximum speed: 670 km/h (416 mph; 362 kn) at 6,000 m (19,685 ft)
• Cruise speed: 552 km/h (343 mph; 298 kn)
• Range: 2,020 km (1,255 mi; 1,091 nmi)
• Combat range: 1,010 km (628 mi; 545 nmi)
• Service ceiling: 11,000 m (36,000 ft)
• Time to altitude: 6,000 m (19,685 ft) in 7.8 minutes

Armament

• Guns:
  

• 2 × 7.93 mm (0.312 in) Basu HV 80 machine guns in wings
• 1 x 20 mm (0.787 in) Basu FG 20-20 cannon firing through propeller hub

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