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The Rolls-Royce Merlin – Could it be the best piston engine ever?

Tuesday, January 11, 2011

The RAF fighters which resisted the German invasion in 1940 during the Battle of Britain, were all equipped with the same engine, the Rolls-Royce Merlin.  This same engine also powered the majority of the bombers of RAF Bomber Command, and some of the best fighters of the 8th USAAF.   Named after a bird of prey, like all piston engines that Rolls-Royce produced, the Merlin is a unique engine for several reasons.

  • Unlike other engines, which changed relatively little during the war, between 1939 and 1945, no fewer than 52 different versions of the Merlin were produced
  • Powered a wide variety of aircraft, including both fighters and bombers.  These included the Spitfire, Hurricane, Boulton Paul Defiant, Avro Lancaster, De Havilland Mosquito, Handley Page Halifax, Armstrong-Whitworth Whitley, and the P-51 Mustang.  The Merlin even replaced the Hercules II version of the Bristol Beaufighter and the Pegasus in version II of Wellington.
  • The Merlin transforms two of the most important aircraft of World War II.  From the poor performing Manchester was born the transformed Merlin powered Lancaster, the legendary aircraft of Bomber Command.  The P-51 Mustang became one of the best fighters in WWII once the under-powered Allison’s were replaced with the Merlin.  With the new found extended range, it became the only fighter to effectively protect the 8th USAF B-17 deep into enemy territory.
  • Finally, it is the only engine to be built in large numbers simultaneously on both sides of the Atlantic during WWII.

The Birth of the Merlin

The Merlin is a conventional engine, derived from relatively older power trains, as engineers and technicians at Rolls-Royce simply evolved the Merlin from existing proven designs. The Merlin was born into a family of  V12 engines whose origin dates back at Rolls-Royce to the First World War.  As mentioned, they all  bear the names of birds of prey, when studying reciprocating engines from Rolls Royce, you also get a lesson in  ornithology.   Rolls entry into aeronautical engines begins with the Eagle in 1915.  The V-12 Eagle propels the Short Bomber (1916), the Vickers Vimy (1917), the Handley Page O/100 (1916), the Handley Page V/1500 (1918), and fighters like the AIRCO DH.4 (1917).  The Eagle is also mounted in the U.S. aircraft (Fairey F.17).  The Eagle was rated between  250 and 375 hp in its various versions, which for the time was a considerable amount of power, and advantage that the water-cooled engines had over the air-cooled engines of the day.   During this time period the Americans, British and French prefer the V-12 engines from  Rolls Royce, Hispano-Suiza, Renault, and Liberty.  The Germans and Italians are loyal to the 6-cylinder Mercedes, Fiat and Isotta-Fraschini.

After the war, Rolls-Royce began, like all its competitors, the race for power, while remaining faithful to the formula of V-12 liquid cooling.  Advances in design, metallurgy, and fuel allow for an increase in the speed (RPM) and compression ratio of the engine.  In 10 years, the compression ratio increases by 50% (it goes from 4: 1-6: 1) and the rotational speed from approximately 1800 to 2400 rpm. In 1927, the Kestrel 21.25 liter engine is released, which soon powers the Hawker biplanes (Audax, Fury, Hart) in the early 1930s.  The Kestrel develops 745 hp, double the power of the engines produced at the end of WWI.  In order to compensate for lower density air at higher altitudes, the Kestrel gets a mechanical compressor, the super-charger, the first turbocharged engine Rolls-Royce produces.  With the gasoline at that time rated at 87 octane, it allowed for a boost pressure of 5.6PSI.

The Kestrel turns out to be a great engine, with innovations such as the use of ethylene glycol for cooling which reduces the size of the radiators.  Interestingly, Messerschmidt, which still awaits the Daimler-Benz V12 engine, will acquire a Kestrel to test the first version of the BF 109 in 1935.  However, the displacement of the Kestrel is a bit inadequate for the next generation of fighters will require, such as Britain’s future Spitfire.

The Kestrel was followed in 1929 by the Buzzard (36.7 liters), which was named Type R in its competition form. It is with the 2300 hp R-type aircraft that race Supermarine S6 allows England to win for the third consecutive time in the 1931 Schneider Cup and beat the world speed record at 407MPH.  However, the Type R is a racing engine, whose performance can only be sustained for a short period of time.

To fill the existing hole in the range between Kestrel and Buzzard, Rolls began to privately develop a new V12 called the PV 12 (Private Venture 12).  In October 1934, the Air Ministry officially orders the PV12 into production and it is given the name Merlin.  For the next 10 years, Rolls-Royce will continue to develop the Merlin, to make it ever more powerful and versatile.

The Merlin I and II : In July 1934, Rolls releases the first pre-production Merlin A, which like many motors, has a bore (137 mm) which is slightly less compared to the stroke (152 mm), a feature that promotes low-end torque. The Merlin is estimated at 790 hp at 2500 rpm at an altitude of 12,000 feet, already outstanding performance for a block that weighs less than 1322 pounds dry (no oil or coolant).  At the same time (Feb 1935), another version (Merlin B) is produced with a redesigned combustion chamber and 4 valves per cylinder, it reached 960 hp at 11,000 feet. The changes follow through F, to be released in small numbers with the name of Merlin I. The Merlin G (called Merlin II production) is the first type for mass production, it reached 1030 hp at 3000 rpm and 16,250 feet. Compared to the type A, the Merlin type G has gained 30% in power, while the weight has increased by 220 pounds. The Merlin II has a single-speed super-charger, and with 87-octane fuel limit has a boost pressure up to 5.6PSI, and in 1939 with the introduction of 100 octane fuel, this was increased to 11.2PSI, improving power at high-altitude.

The X Merlin : The Merlin X represented a milestone in the evolution of Merlin with the introduction of a two-speed compressor.  Driven by the engine, the supercharger requires power to compress the incoming air.  Therefore, it is important that the power required to compress the air does not exceed the power gained.  The two-speed compressor would allow a lower pressure when the engine was at low to medium altitude, and only use maximum pressure at high altitude.  With the adoption of this compressor Rolls-Royce significantly improves the performance of the Merlin.

Series 60 and Beyond : For the 60 series, the Merlin receives a two-stage compressor. Rather than resorting to turbocharging, which Rolls Royce has no experience, and requires special alloys, Sir Stanley Hooker (Merlin Head Engineer) prefers to mount a two-stage compressor.  This again allows efficient low altitude performance, while increasing high altitude performance.  The ultimate development of this technology will lead to the series 100, which develops over 2000 hp at sea level, and retains a power of 1000 hp at 12,000 ft, with a boost pressure of  2.8PSI.  With the two-stage compressor, Rolls-Royce has the Merlin which is the envy of American turbocharged engines.

The Merlin in Action

Almost all British aircraft, fighters or bombers, were, during the war, equipped with the Merlin. With its V configuration, Merlin offered a reduced frontal area, which was perfect for swift fighters.  Two of these mythical Battle of Britain fighters were the Spitfire and Hurricane. The first Spitfire and Hurricane used the Merlin II. Although designed for fighters, the Merlin also powers almost all British bombers, first the twin-engine bombers (Stirling, Whitley, Mosquito) and then the four-engined Lancaster and Halifax.  The Merlin power plant is also installed in two American fighters, the Curtis P-40 in limited numbers, and the P-51 Mustang almost excusively.

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North American P-51 Mustang

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Bell P-39N Airacobra – Little Sir Echo – Small Fry

Tuesday, September 7, 2010

Bell P-39 Airacobra - Little Sir Echo

This is P-39N-5 “Little Sir Echo / Small Fry” Serial Number 42-19027 which served with the USAAF 5th Air Force (AF), 71st Tactical Reconnaissance Group (TRG), 82nd Tactical Reconnaissance Squadron (TRS), from June 1943 to July 16, 1944. It was abandoned at Tadji, Papua New Guinea, a Japanese airfield that was liberated by the US Army on April 26, 1944. Tadji became a major Allied air depot for American and Australian forces, and the resting place for this P-39 for the next thirty years. It is now on static display at the Planes of Fame Museum in Chino, CA.

This specific P-39 was delivered to the US Army on April 28, 1943, and sent to the Pacific in May. Lyndall W. Tate was assigned to this aircraft. Lyndall was born Oct 20, 1920 in Texas, and passed away Sept 15, 2008. He served over 28 years in the military. If anyone else has any further information on Lyndall, please let us know more about this hero. The aircraft was recovered from Tadji in a 1974 salvage operation funded by David Talichet’s Yesterday’s Air Force (MARC). It currently is on static display at the Planes of Fame museum. It still supports its original markings of Olive Drab over Neutral Grey with White New Guinea theatre markings on tail unit, wing leading edges and spinner (thin White band on nose). In addition it features an interesting shark mouth on the center drop-tank.

The Bell P-39 was one of the US’s main-line fighters when war first broke out in the Pacific at the beginning of World War II. It was unique at the time for having a tricycle undercarriage and a mid-mounted engine located behind the pilot. This arrangement was due to the proposed installation of a powerful 30 mm cannon in the nose. Ultimately, the P-39 was unable to achieve the same performance of later US and European fighters, mainly due to a lack of a turbo-supercharged engine which greatly limited the P-39′s ceiling and speed. However, its low-altitude performance, mid-mounted engine, and armor plating allowed it to become a great ground-support aircraft, most notably used by the Soviet Air Force. In the end, the Bell P-39 became Bell’s most successful fixed-wing aircraft that they ever produced.

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P-51 Mustang

Wednesday, April 1, 2009

U.S. Army Air Force (USAAF) fighter aircraft manufactured by North American Aviation, Inc., between 1942 and 1945. In its role as a long-range bomber escort in the European Theater of Operations during World War II, the P-51 exhibited its greatest influence and is credited by many as the airplane that shifted the European airwar in favor of the allied forces.

This P-51 was used by the USAFF, USAF and various U.S. Air National Guard units during and after World War II, performing a variety of missions, including interception of enemy aircraft, long-range bomber escort, armament support for land and sea forces, photographic reconnaissance and flight training.

The P-51 performed at levels surpassing other single-engine, propeller driven fighter aircraft during World War II.  The wingspan of 44-73287 is 37.03 feet and has a wing area of 236 square feet. The plane’s two-section, semimonocoque fuselage is constructed entirely of aluminum alloy and is 32 feet and 2 5/8 inches in length.

Laminar flow airfoil was used during World War II in the design of the wings for the North American P-51 Mustang, as well as some other aircraft. Operationally, the wing did not enhance performance as dramatically as tunnel tests suggested. For the best performance, manufacturing tolerances had to be perfect and maintenance of wing surfaces needed to be thorough. The rush of mass production during the war and the tasks of meticulous maintenance in combat zones never met the standards of NACA laboratories. Still, the work on the laminar flow wing pointed the way to a new family of successful high-speed airfoils. These and other NACA wing sections became the patterns for aircraft around the world.

P-51 Mustang

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Grumman F-14 Tomcat

Tuesday, August 19, 2008

 Grumman F-14 Tomcat

The Grumman F-14 Tomcat is a supersonic, twin-engine, variable sweep wing, two-place strike fighter. The Tomcat’s primary missions are air superiority, fleet air defense and precision strike against ground targets. Recently phased out of active service, the F-14 has had a long and distinguished career. The person responsible for the F-14 project was Admiral Tom Conolly, Deputy Chief, Naval Operations for Air. The aircraft was dubbed “Tom’s Cat” long before it was officially named “Tomcat”. Naming their aircraft after ‘cats’ is a long held Grumman tradition.

The F-14 Tomcat had visual and all-weather attack capability to deliver Phoenix and Sparrow missiles as well as the M-61 gun and Sidewinder missiles for close in air-to-air combat. The F-14 also had the LANTIRN targeting system that allows delivery of various laser-guided bombs for precision strikes in air-to-ground combat missions. This enabled the Tomcat to acquire mensurated target coordinates that are accurate enough for GPS weapons, which was unique to the Tomcat. The F-14, equipped with Tactical Air Reconnaissance Pod System (TARPS) was the Navy’s only manned tactical reconnaissance platform.

The F-14 was designed in 1968 to take the place of the controversial F-111B, which was under development for the Navy’s carrier fighter inventory. The F-14A used the P&W TF30 engines and AWG-9 system and carried the six Phoenix missiles that had been intended for the F-111B. A completely new fighter system was designed around these with emphasis on close-in fighting “claws” along with standoff missile fighting. Grumman was announced as competition winner for the new carrier-based fighter for the U.S. Navy. Emphasis had been placed on producing a comparatively small, light weight, high performance aircraft with a significant advance over the then current F-4 Phantom II. The F-14 had three primary missions; the first was as a fighter / escort to clear contested air space of enemy fighters and protecting the strike force. The second mission was to defend the carrier task force with Combat Air Patrols (CAP) and interception operations. The third role was secondary attack on tactical ground targets.

From its first flight on 21 December 1970, the F-14A went through five years of development, evaluation, squadron training and initial carrier deployments to become the carrier air wings’ most potent fighter. Technical and financial problems that received a great deal of publicity were overcome in achieving this goal. Originally it was planned that the F-14B with the advanced P&W F401 would be the major production version. However, performance of the TF30-P-412 exceeded expectations while development of the F401 was delayed. One F-14B was flight tested, showing that an F401-powered Tomcat would be a potential future option.

The first operational ‘Tomcat’ squadrons with the U.S. Navy were VF-1 and VF-2. VF-2 flew the first operational sorties from the U.S.S. Enterprise in March 1974. The first ‘combat’ cruise of the Tomcat was in April 1975 when the Enterprise covered the withdrawal from Saigon, South Vietnam although no combat took place between American and North Vietnamese forces. In the 1980s, in what was known as the ‘Gulf of Sidra Incident’, a pair of VF-41 ‘Black Aces’ Tomcats from USS Nimitz shot down two Libyan Su-22 Fitters on 19 August 1981. A similar incident took place again on 4 January 1989 when a pair of VF-32 ‘Swordsmen’ Tomcats from USS John F. Kennedy shot down two Libyan MiG-23 Floggers.

Also, during the 1980s, Iranian F-14s (the only export customer for the F-14) were engaged in combat against the Iraqi Air Force during the Iran-Iraq War. Apart from functioning in its intended role, Iranian Tomcats were also used as mini-AWACS, using their superior radar system to direct other Iranian fighter planes (such as the F-4 and the F-5) against Iraqi aircraft. The final kill by the US Navy Tomcat is an Iraqi Mi-8 helicopter, shot down by an F-14 from VF-1 using a Sidewinder AAM on 7 February 1991 during Operation Desert Storm. These five kills are the only ones scored by the US Navy. The IRIAF Tomcats is much more successful, shooting down fairly large numbers of Iraqi warplanes using all the weapons systems available.

The Tomcat caps a long line of Grumman Cats. In the hands of Navy pilot/NFO teams, it provided the carrier task force with its first-line offense and defense against any enemy air threat in the tradition of its predecessors.  The F-14 became famous to the general public, as the star of the movie Top Gun, which also featured Tom Cruise.

The F-14 Tomcat performed superbly in Operation Allied Force and the strikes in Operation Southern Watch. While the Navy provided only eight percent of the total dedicated aircraft in Operation Allied Force, the Navy was credited with 30 percent of the validated kills against fielded forces in Kosovo as a result of the superb performance of the Tomcat in the Forward Air Controller (Airborne) (FAC(A)) role.

Specifications
Function: Carrier-based multi-role strike fighter
Contractor: Grumman Aerospace Corporation
Unit Cost: $38 million
Propulsion:
F-14A: Two Pratt & Whitney TF-30P-414A turbofan engine with afterburners
F-14B and F-14D: Two General Electric F110-GE-400 turbofan engines with afterburners
Thrust:
TF-30P-414A: 20,900 pounds (9,405 kg) static thrust per engine
F110-GE-400: 27,000 pounds (12,150 kg) static thrust per engine
Length: 61 feet 9 inches (18.6 meters)
Height: 16 feet (4.8 meters)
Maximum Takeoff Weight: 72,900 pounds (32,805 kg)
Wingspan: 64 feet (19 meters) unswept, 38 feet (11.4 meters) swept
Ceiling: Above 56,000 feet
Range: 1239 km 1994 km
Speed: Mach 2+
Crew: Two: pilot and radar intercept officer
Armament: Up to 13,000 pounds to include AIM-54 Phoenix missile, AIM-7 Sparrow missile, AIM-9 Sidewinder missile, air-to-ground precision strike ordnance, and one M61A1/A2 Vulcan 20mm cannon.
Date Deployed: First flight: December 1970

Click the picture for even more great Tomcat pictures!
Grumman F-14 Tomcat

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Lockheed Martin F-22 Raptor

Monday, August 11, 2008

F-22 Raptor

The F-22A Raptor is a next-generation fighter/attack aircraft that features the latest stealth technology to reduce detection by radar. Using more advanced engines and avionics than the current F-15 Eagle, the F-22A is intended to maintain U.S. Air Force capabilities against more sophisticated enemy aircraft and air defenses in the 21st century.

The Raptor combines stealth, maneuverability and the ability to fly long distances at supersonic speeds — or “super cruise” — in performance of air superiority and air-to-ground missions. Furthermore, it requires less maintenance than older fighters. These capabilities represent an exponential leap in war fighting capabilities.

In 1981 the U.S. Air Force needed a new air superiority fighter that would take advantage of new technologies in fighter design including composite materials, lightweight alloys, advanced flight control systems, higher power propulsion systems and stealth technology. Lockheed Martin’s F-22 won the design competition in April 1991, and the rollout ceremony for the first F-22 Raptor occurred in April 1997.

The Raptor successfully completed its initial operational and test evaluation in 2004, and the program received approval for full rate production. In December 2005 operational aircraft were designated F-22As.

Production of the F-22A is a partnership between Lockheed Martin, Boeing and Pratt & Whitney. Boeing builds the Raptor’s wings and aft-fuselage; the engines come from Pratt & Whitney, and Lockheed Martin builds the forward fuselage and assembles the subsections in Marietta, Ga.

On May 12, 2005, the Raptor program achieved a historic milestone with the delivery of the first combat-capable Raptor to the 27th Fighter Squadron, 1st Fighter Wing, at Langley Air Force Base, Va. In January 2006 the 27th Fighter Squadron flew the first operational mission with the F-22 in support of Operation Noble Eagle (the official name given to the defense of U.S. borders).

A combination of sensor capability, integrated avionics, situational awareness, and weapons provides first-kill opportunity against threats. The F-22A possesses a sophisticated sensor suite allowing the pilot to track, identify, shoot and kill air-to-air threats before being detected. Significant advances in cockpit design and sensor fusion improve the pilot’s situational awareness. In the air-to-air configuration the Raptor carries six AIM-120 AMRAAMs and two AIM-9 Sidewinders.

The F-22A has a significant capability to attack surface targets. In the air-to-ground configuration the aircraft can carry two 1,000-pound GBU-32 Joint Direct Attack Munitions internally and will use on-board avionics for navigation and weapons delivery support. In the future air-to-ground capability will be enhanced with the addition of an upgraded radar and up to eight small diameter bombs. The Raptor will also carry two AIM-120s and two AIM-9s in the air-to-ground configuration.

Advances in low-observable technologies provide significantly improved survivability and lethality against air-to-air and surface-to-air threats. The F-22A brings stealth into the day, enabling it not only to protect itself but other assets.

The F-22A engines produce more thrust than any current fighter engine. The combination of sleek aerodynamic design and increased thrust allows the F-22A to cruise at supersonic airspeeds (greater than 1.5 Mach) without using afterburner — a characteristic known as super cruise. Super cruise greatly expands the F-22A ‘s operating envelope in both speed and range over current fighters, which must use fuel-consuming afterburner to operate at supersonic speeds.

The sophisticated F-22A aero design, advanced flight controls, thrust vectoring, and high thrust-to-weight ratio provide the capability to outmaneuver all current and projected aircraft. The F-22A design has been extensively tested and refined aerodynamically during the development process.

From the very beginning, the F-22A exceeded the USAF’s expectations, and during exercises and deployments, it proved to be more than a match for any fighter opposing it.

During the highly realistic Exercise Northern Edge 2006, the F-22 proved itself against as many as 40 “enemy aircraft” during simulated battles. The Raptor pilots achieved a 108-to-zero “kill” ratio against the best F-15, F-16 and F-18 “adversaries.” The stealthy F-22A also proved that it could avoid and destroy enemy surface to air missiles, and recorded an impressive 97 percent mission capability rate.

Specifically noting the Raptor’s performance at Northern Edge, the National Aeronautic Association (NAA) awarded its 2006 Robert J. Collier Trophy, considered America’s most prestigious award for aeronautical and space development, to the Lockheed Martin Corp.-led F-22 Raptor aircraft team “for designing, testing and operating” the Raptor. Team members included Lockheed Martin, Boeing, Pratt & Whitney, Northrop Grumman, Raytheon and BAE Systems. This amazing aircraft was described as “the most efficient and effective fighter in history, through exceptional performance and outstanding safety features.”

The F-22A will have better reliability and maintainability than any fighter aircraft in history. Increased F-22A reliability and maintainability pays off in less manpower required to fix the aircraft and the ability to operate more efficiently.

Specifications
Primary Function: Air dominance, multi-role fighter
Contractor: Lockheed-Martin, Boeing
Power Plant: Two Pratt & Whitney F119-PW-100 turbofan engines with afterburners and two-dimensional thrust vectoring nozzles.
Thrust: 35,000-pound class (each engine)
Wingspan: 44 feet, 6 inches (13.6 meters)
Length: 62 feet, 1 inch (18.9 meters)
Height: 16 feet, 8 inches (5.1 meters)
Weight: 43,340 pounds (19,700 kilograms)
Maximum Takeoff Weight: 83,500 pounds (38,000 kilograms)
Fuel Capacity: Internal: 18,000 pounds (8,200 kilograms); with 2 external wing fuel tanks: 26,000 pounds (11,900 kilograms)
Payload: Same as armament air-to-air or air-to-ground load outs; with or without 2 external wing fuel tanks.
Speed: Mach 2 class with super cruise capability
Range: More than 1,850 miles ferry range with 2 external wing fuel tanks (1,600 nautical miles)
Ceiling: Above 50,000 feet (15 kilometers)
Armament: One M61A2 20-millimeter cannon with 480 rounds, internal side weapon bays carriage of two AIM-9 infrared (heat seeking) air-to-air missiles and internal main weapon bays carriage of six AIM-120 radar-guided air-to-air missiles (air-to-air load out) or two 1,000-pound GBU-32 JDAMs and two AIM-120 radar-guided air-to-air missiles (air-to-ground load out)
Crew: One
Unit Cost: $142 million
Initial operating capability: December 2005
Inventory: Total force, 91

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