One Second In The Life Of A Merlin Engine

If you could slow time down, and examine just one second of what takes place inside a filly operating Merlin engine at full power, what would you find?

In that one second, the V-12 Rolls-Royce Merlin engine would have gone through 60 revolutions, with each of the 48 valves slamming open and closed 30 times. The twenty four spark plugs have fired 720 times. Each piston has traveled a total of 60 feet in linear distance at an average speed of 41 miles per hour, with the direction of movement reversing 180 degrees after every 6 inches. Three hundred and sixty power pulses have been transmitted to the crankshaft, making 360 sonic booms as the exhaust gas is expelled from the cylinder with a velocity exceeding the speed of sound. The water pump impeller has spun 90 revolutions, sending 4 gallons of coolant surging through the engine and radiators. The oil pumps have forced 47 fluid ounces, roughly one-third gallon, of oil through the engine, oil cooler, and oil tank, scavenging heat and lubricating the flailing machinery. The supercharger rotor has completed 348 revolutions, it's rim spinning at Mach 1, forcing 4.2 pounds or 55 cubic feet of ambient air into the combustion chambers under 3 atmospheres of boost pressure. Around 9 fluid ounces of high octane aviation fuel, 7843 BTU's worth of energy, has been injected into the carburetor along with 5.3 fluid ounces of methanol/water anti-detonant injection fluid. Perhaps 1/8 fluid ounce of engine oil has been either combusted or blown overboard via the crankcase breather tube. Over 1.65 million foot pounds of work have been done, the equivalent of lifting a station wagon to the top of the Statue of Liberty.

In that one second, the hard-running Merlin has turned the propeller through 25 complete revolutions, with each of the blade tips having arced through a distance of 884 feet at a rotational velocity of 0.8 Mach. Fifteen fluid ounces of spray bar water has been atomized and spread across the face of the radiator to accelerate the transfer of waste heat from the cooling system to the atmosphere.

In that one second, the aircraft itself has traveled 704 feet, close to 1/8 mile. The pilot's heart has taken 1.5 beats, pumping 5.4 fluid ounces of blood through his body at a peak pressure of 4.7 inches of mercury over ambient pressure. Our pilot happened to inspire during our measured second, inhaling approximately 30 cubic inches (0.5 liter) of oxygen from the on-board system, and 2.4 million, yes million, new red blood cells have been formed in the pilot's bone marrow.

In just one second, an amazing sequence of events have taken place. Don't blink!

The Rolls-Royce Merlin XX Engine	The Liberty Engine
Merlin-powered Aircraft	Inside The Merlin Engine
The Rolls-Royce Packard "Merlin" Engine	The "Merlin" Mustang

Everyone knows the Spitfire story, how it was designed by Joseph Mitchell, based on some of the knowledge from building the Supermarine Schneider Trophy seaplane racers. However it is not acknowledged that without the Merlin engine the Spitfire would not have been the exceptional aircraft that it was. In the following paragraphs some interesting facts about the Merlin will be revealed. It is presumed that the reader will be familiar with basic technical details, e.g., twelve cylinder "V" design, liquid cooled, supercharger, etc.

The Battle of Britain was a pivot point in WWII and the history of the world. The Merlin engine was an important factor in the success of the RAF. Merlin design and development was a private venture by Rolls Royce. No government funding was provided and it was called the PV-12 (Private Venture). The engine was first flown on April 12, 1935, in a Hawker Hart biplane.

By strange chance, both the ME109 and HE113 fighters in Gremany were first flown with a Rolls Royce engine, the Kestral, as the Dailmer-Benz engine was not yet available. As a further note -- the ME109s featured in the post-war Battle of Britain film were Spanish ME109s fitted with Merlin engines.

Merlin's, in many different MKs, were fitted to many different aircraft, including Spitfires, Hurricanes, Wellingtons, Defiants, Lancasters, Halifaxes, Mustangs, and Mosquito's. When the Allison-engine Mustang come to England it was very fast at low altitude (350 mph), but pretty useless above 10,000 feet. However when fitted with the Merlin the speed increased to 450 mph and it had excellent performance at altitude. The official speed record for a piston engine powered aircraft is held by a Mustang (499.048 mph), powered by a Griffon engine which was a later development of the Merlin.

Churchill considered the Merlin so important that early in the war he secretly ordered a set of drawings sent to America in case England was overrun. In 1940 production was arranged in the U.S.A. where they were made by the Packard plant in Detroit. Henry Ford turned down the chance to make the world's greatest engine because he thought Britain would lose the war.

All aircrew who have flown in Merlin-engine aircraft will pay tribute to the performance of these engines. The post-war North Star was noisy but at least one knew that the engines were doing their job! Lord Trenchard, when reviewing the Battle of Britain, gave full credit to the Merlin engine as one of the chief factors in the RAF victory.