Category Archives: Reconnaissance

Reconnaissance

Republic XF-12 ‘Rainbow’ (Anigrand Models, Resin)

TYPE: High-performance reconnaissance aircraft

ACCOMMODATION: Crew of seven

POWER PLANT: Four Pratt & Whitney R-4360-31 “Wasp Major” radial engines, rated at 3,250 hp each

PERFORMANCE: 470 mph

COMMENT: The Republic XF-12 “Rainbow” was an American four-engine, all-metal reconnaissance aircraft designed by the Republic Aviation Company in the late 1940s. The aircraft was designed with maximum aerodynamic efficiency in mind. The XF-12 was referred to as an aircraft that was “flying on all fours” meaning: four engines, 400 mph cruise, 4,000 miles range, at 40,000 feet. It is still the fastest piston-engined airplane of this size, exceeding by some 50 mph the Boeing XB-39 of 1944. Although highly innovative, the postwar XF-12 “Rainbow” had to compete against more modern turbojet engine technology, and did not enter production.
In August 1943, U.S. President Franklin D. Roosevelt’s son, Colonel Elliot Roosevelt, commander of the F-5 (modified P-38) “recon” unit, recommended the acquisition of a dedicated high-performance photo reconnaissance aircraft, capable of providing pre-strike target acquisition and photo interpretation. Followed by additional overflights to provide post-strike analysis of their subsequent destruction, this would give commanders the ability to make pivotal strategic decisions and set up subsequent raids. The XF-12 “Rainbow” was Republic Aviation’s attempt to meet those goals. Its primary competition during this time was the Hughes XF-11. Both were introduced at the same time, and both were powered by the new Pratt & Whitney  R-4360. The XF-12’s first flight was made on 4 February 1946. During the XF-12’s subsequent flight testing and development period, it demonstrated the capability of operating at 45,000 feet, at a speed of 470 mph, over a range of 4,500 mi, so it met and exceeded the design goals for which it had been designed. Neither the XF-11 nor the XF-12 was purchased in any quantity by the U.S. Army Air Forces (two each), as their need evaporated after hostilities ended in World War II.
When the XF-12 was modified with increased “all weather” equipment and outfitted with its new engines capable of providing short burst of extra power, it suddenly assumed tremendous importance in the eyes of both the U.S. Air Force and the State Department. As a potent intelligence weapon, the XF-12 had the ability to obtain photographs both in daylight and under conditions of restricted visibility at high altitudes over long ranges and with great speed. In theory, operating from northern bases (Alaska and Canada), this “flying photo laboratory” was capable of mapping broad stretches of territory in the Arctic regions performing reconnaissance with near-invulnerability.[4]
Low drag was a primary consideration throughout the design of the XF-12. Many of its features were taken directly from Republic’s considerable experience with fighter plane design. In an extremely rare case of design direction, absolutely no compromise with aerodynamics was made in the shape of its fuselage, the sharp nose and cylindrical cigar shape of the XF-12 fulfilled a designer’s dream of a no compromise design with aerodynamic considerations.
To fulfill its reconnaissance role, the XF-12 contained three separate photographic compartments aft of the wing. One vertical, one split vertical, and one trimetrogon each using a six-inch Fairchild K-17 camera. For night reconnaissance missions, the XF-12 had a large hold in the belly which accommodated 18 high-intensity photo-flash bombs; these were ejected over the target area. All of the bays were equipped with electrically operated, inward retracting doors (again designed for maximum aerodynamic cleanliness). The camera lenses were electrically heated to eliminate distortion. All of this combined to allow full photo operations during high speed flights. The XF-12 also carried a variety of photographic equipment, including complete darkroom facilities to permit the development and printing of films in flight. This was augmented by adjustable storage racks, able to handle any size film containers and additional photo equipment. This allowed the Army Intelligence units to have immediate access to the intelligence the aircraft was able to collect, with no delay in processing.
The XF-12 “Rainbow” featured a wing of straight taper with squared tips and high aspect ratio for maximum efficiency. The engines featured a sliding cowl arrangement to facilitate cooling airflow instead of the normal cowl flaps, which caused too much drag. At the front of the cowls, the engines were also fitted with a two-stage “impeller fan” directly behind the propeller hub and prop spinner. This allowed the engines to be tightly cowled for aerodynamic efficiency, but still provide the cooling airflow the engines required. When the sliding cowl ring was closed (during flight), the air used for cooling the engine was ducted through the nacelle to the rear exhaust orifice for a net thrust gain, as opposed to the usual cooling drag penalty.
All of the air for the engine intakes, oil coolers and intercoolers was drawn through the front of each wing between the inboard and outboard engines. This allowed less drag than with individual intakes for each component. In addition, because the air was taken from a high-pressure area at the front of the wing, this provided a “ram air” benefit for increased power at high speeds, and more effective cooling of the oil and intercoolers. The intake portion of the wing comprised 25% of the total wingspan. They were extensively wind tunnel tested for intake efficiency and inlet contour efficiency. This cooling air, after being utilized, was ducted toward the rear of the nacelle, to provide additional net thrust. The entire engine nacelle was the length of a Republic P-47 “Thunderbolt”. Each engine featured twin General Electric turbochargers, situated at the aft end of the nacelle. All of the exhaust from the engines was ducted straight out of the back of the nacelles. This provided additional thrust. Research showed that roughly 250 equivalent horsepower was generated by each engine exhaust during high speed cruise at 40,000 ft.
The original design of the XF-12 called for contra-rotating propellers, similar to those used on the original XF-11. However, due to the added complexity and reliability issues, the propellers were never installed. They would have been twin three-bladed propellers (rotating in opposite directions). As it was, the aircraft used standard four-bladed Curtiss Electric propellers for all flights.
Had the XF-12 “Rainbow” been available in 1944, it almost inevitably would have been ordered in quantity, and along with its civilian counterpart, the whole postwar structure of aircraft markets might have been altered. As it was, the XF-12 disappeared into oblivion, despite its graceful lines and high performance. The “Rainbow” remains the ultimate expression of multi-engine, piston-powered aircraft design. Its high speed, near-perfect streamlined form, and neatly cowled engines make it a design classic, often unappreciated, and not very well known. The XF-12 was the fastest, four engine pure piston-powered aircraft of its day, and the only one ever to exceed 450 mph in level flight. (Ref.: 24).

De Havilland “Mosquito” F-8, 25th BG(R) -802 RG(P) (Matchbox)

TYPE: Photo-reconnaissance aircraft

ACCOMMODATION: Pilot and radio-operator/navigator

POWER PLANT: Two Packard “Merlin” 31 or 33 liquid-cooled engines, rated at 1,460 hp each

PERFORMANCE: 408 mph at 28,000 ft

COMMENT: Until the end of WW II the de Havilland Company Canada rolled out 1,133 “Mosquito” aircraft of different subtypes.  The “Mosquito” B Mk XX was the Canadian version of the “Mosquito” B. Mk. IV bomber aircraft of which 145 were built. From these 40 were converted into F-8 photo-reconnaissance aircraft for the USAAF and used with the 8th USAAF in the European Theatre of Action. It had the same Packard “Merlin” engines and was equipped with three overload fuel tanks, totaling 3,500 L in the bomb bay. Additionally, for range extension it could also carry two 230 L or 450 L drop tanks.
The de Havilland “Mosquito” of 25th BG(R) -802 RG(P) were painted in normal RAF P.R. Blue finish. In August 1944 the vertical tail was colored in red and in September 1944 all tail surfaces were painted red. This marking was necessitated by frequency of misidentification of “Mosquito” as enemy type. Similar marking were used on BoeingB-17G of 652 BS.
The 25th Bombardment Group (Reconnaissance) was constituted in the days after D-Day and activated in England in August 1944 to carry out photographic and mapping missions over mainland Europe as the Allied armies pushed east. The Group were designated a Bombardment Group but they did not drop bombs. Instead they flew bombers to drop ‘chaff’ screenings for other Bomb Groups. ‘Chaff’, strips of metallic paper, would interfere with the enemy’s ability to detect aircraft using radar (Ref.: 24).

Republic XF-15 “Reporter” (Airfix, Parts from Airmodel, Vacu-formed)

TYPE: Photo-reconnaissance aircraft

ACCOMMODATION: Crew of two

POWER PLANT: Two Pratt & Whitney R-2800-65 “Double Wasp” radial engines, rated at 2,000 hp each

PERFORMANCE: 376 mph at 17,000 ft

COMMENT: In autumn 1944, two Northrop P-61B “Black Widow” night fighters were extensively modified in an attempt to improve the performance and to extend the long-range in order to use these aircraft as long-range escort fighters.  Designated XP-61E the fuselage decking was cut flush with the wing to allow a large blown canopy to be fitted. The center and aft section of the fuselage nacelle housed additional fuel tanks and the nose radar was supplanted by four machine guns. The XP-61E’s were tested in the early month of 1945 but the second was lost in an accident on April 1945 and in view of the changing course of the war, further development of the “Black Widow” in this role as long-range escort fighter was abandoned. The first and remaining prototype was converted to the XF-15 “Reporter”, a long-range photo-reconnaissance aircraft, tested after the war. Due to the on-coming new turbojet powered aircraft a production order never was placed (Ref.: 9).

Supermarine ‘Spitfire’ Mk. IX, 7th Photographic Group, 8th USAAF (Matchbox)

TYPE: Interceptor fighter, fighter bomber, photo-reconnaissance

ACCOMMODATION: Pilot only

POWER PLANT: One Rolls-Royce ‘Merlin 66’ liquid-cooled engine, rated at 1,720 hp

PERFORMANCE: 404 mph at 21,000 ft

COMMENT: By the end of 1941, the ‘Spitfire’ Mk. V was experiencing increasing difficulty in combating the newer versions of the Messerschmitt Me 109 and found itself completely outclassed by the Focke-Wulf Fw 190. So the need for a higher performance was a matter of the most vital urgency. In order to achieve the desired performance improvement with the least possible delay, it was decided to install the Rolls-Royce ‘Merlin 60’ Series engine in the basic ‘Spitfire’ Mk.VC, this marriage of convenience being designated ‘Spitfire’ Mk. IX. Despite the fact that the ‘Spitfire’ Mk. IX was considered solely as an interim type, it was to be produced in larger quantities than any other Spitfire variant, in total 5.665 aircraft being manufactured. Logical evolutions of the ‘Spitfire’ Mk. IX were the photo-reconnaissance P.R. Mks. IX, X, and XI. A universal camera installation provided accommodation for two F.8 or F.52 vertical cameras, or two F.24 vertical and one F.24 oblique camera. A number of Spitfire P.R.Mk. IX was delivered to the 8th USAAF and the aircraft shown here belonged to the 7th Photographic Group, stationed at Chalgrove, U.K. (Ref.: 12)

Hughes XF-11 (Anigrand, Resin)

TYPE: Long-range reconnaissance-aircraft

ACCOMMODATION: Crew of two

POWER PLANT: Pratt & Whitney R-4360-31 Wasp Major, rated at 3,000 hp each

PERFORMANCE: 450 mph

COMMENT: The Hughes XF-11 was designed as a long-range reconnaissance aircraft. Its design based on the Hughes D-2, a fighter and bomber project of early 1940, and resembled somewhat to the Lockheed P-38 Lightning but was much greater. So it had a tricycle landing-gear, two engines, twin boom and a pressurized central crew nacelle. In 1943 the USAAF ordered 100 F-11s, but only two examples were completed immediately after WWII. The first aircraft crashed in 1946 with Howard Hughes at the controls and the second prototype was completed and successfully flown in 1947. (Ref.: 23)