Z-Car

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

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.


B-17 E-Z Goin’ and the Sonderkommando Elbe – Buchen Raid

Laurence J. Lazzari Crew
Kneeling L to R: Sgt. Laurence W. Donnelly (BTG), T/Sgt. Robert J. Steele (ROG), 2nd Lt. Charles W. Staiger (NAV)Sgt. Joseph G. Allen.  Standing L to R: Sgt. Richard H. Heritage (NG/TOG), T/Sgt. Charles A. Weiss (TTE), 2nd Lt. Laurence J. Lazzari (P),
2nd Lt. Guiher G. Greenwood (CP), 2nd Lt. Daniel J. O’Connell, Jr. (TG).
100th BG Photo Archives

This website recently received a comment from USAF Colonel Guiher G. Greenwood (retired) who served with the 351st Bomb Squadron, 100th Bomb Group, regarding a picture posted in our gallery. He identified the plane pictured as that of the B-17 E-Z Goin’ piloted by Joe Martin with co-pilot Henry Cervante on the Buchen raid of April 7, 1945. Interestingly, Col Greenwood and Joe Martin lived through one of the more infamous “suicide” attacks by the Germans in their last desperate days of the war.

The Sonderkommando Elbe was a special squadron of the German Luftwaffe, a Luftwaffe task force assigned to bring down Allied bombers by ramming German aircraft into the Allied bombers. Sonderkommando means special command, and Elbe is a river that runs through Germany to the North Sea. The Sonderkommando Elbe was formed at Reichmarschall Hermann Goering’s insistence that the Reich’s defense units should start ramming bombers as a last resort. This group of fighters was not solely tasked with ramming bombers, but that was their last ditch option. In theory this was not a suicide mission, they were only supposed to ram an Allied bomber if there was a chance to bail out alive. Unlike the Japanese kamikaze pilots, the inexperienced German pilots brought a parachute with them while flying their striped-down Messerschmitt Bf 109’s, if the pilot survived the collision, he could use the parachute.

The only documented mission, often called Rammkommando Elbe (ramming) or Werewolf, was on April 7, 1945 when a total of 120 pilots took off in their fighters and attacked several formations of U.S. bombers heading towards the Germany heartland. These young German pilots were motivated to destroy Allied bombers by any means necessary, they had seen their country decimated by the relentless Allied bombing campaign. Although the Luftwaffe had an amply supply of airplanes, even in April 1945, they lacked trained pilots and aviation fuel. Many of the Sonderkommando pilots had only 50 hours of training, and their lack of experience was as likely to get them killed as the P-51 Mustangs that protected the Bomber Armada.

This last ditch effort of the mighty Luftwaffe resulted in only 15 Allied bombers attacked with eight successfully destroyed. Several planes barely limped back to base, these included the E-Z Goin’ flown by Joe Martin’s crew. Their left stabilizer was ripped off, and the rudder substantially damaged. In addition to having little control of the plane, they also lost engine #1. Somehow the crew was able to return to England, and landed successfully.

 


 


P-38’s in Chino at Planes of Fame – Honey Bunny, Glacier Girl, and three others…

P-38 Honey Bunny in Chino at Planes of Fame

Last week  5 of the 7 still flying P-38s flew from Chino to the Sacramento Capital airshow at Mather for the weekend show.   John Maloney flew chase in a P-51!

The fighters joined up over Lake Mathews for a photo shoot and then climbed up and headed north to Mather.  Along the way Hinton decided they would buzz Shafter where his son was preparing “Stega” for the Reno Races.  The WWII  fighters went screaming by the hangar all in a row at about 300 MPH!   The Air Museums P-38  23 Skidoo cracked a head so they followed her to descent at FAT and then pressed on.   At one point in the flight Maloney came from behind in the Mustang and dove down the right of the formation and pulled up into a giant exaggerated barrel roll around the rather loose goose formation so the camera man could snap a photo thru the canopy of the Mustang as he was inverted over the P-38 flight.  Sounds like fun!

Other P-38’s that made it to Mather included Ruff Stuff, Thoughts of Midnight, and Tangerine.


North American P-51 Mustang

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


Planes of Fame Air Museum Visit

Planes of Fame Air Museum Front Sign

I recently visited the Planes of Fame Air Museum in Chino California. What a wonderful place to visit and stroll through dozens of old classic birds.  Where else can you find a perfectly restored Corsair and Mustang along side a B-29 fuselage waiting for some loving care?

The Air Museum was founded by Edward Maloney, who recognized the importance of preserving WWII aircraft at a time when most of these planes were being cut up into scrap metal. The Air Museum was the first permanent air museum west of the Rocky Mountains. It officially opened its doors to the public in January 1957, with an initial collection of six aircraft and a great deal of hope for the future.  Of the museum’s approximate 150 aircraft, 30 are flyable. On a typical Saturday, you may see two P-51 Mustangs fly by escorting a B-25 Mitchell bomber, or a Grumman F6F Hellcat with a Chance-Vought Corsair making a formation overhead approach to the airport.


Pictures of RX-7 at Summit Point

This is my 94 RX-7 at Summit Point. In this picture,
I am going through Turn 6. The car looks good here,
nicely settled into Turn 6 at just about the proper apex.
The quality of these pictures is not that great, click on
the picture to get a slightly higher quality JPG.
I got a little anxious here, and I am just up on the
curbing. Six inches to the left, and I am in heaven.
There is a red Mustang trying to catch me in the
background (good luck). You can see how his rear is
unloading as he trail brakes into Turn 5.
Again, I am approaching the apex of Turn 6. This time
I have a Porsche 911 on my tail. The 911’s are quick at
Summit Point, but this one was being driven by a rookie.
Hitting the second apex on Turn 6.
Once again, hitting the second apex on Turn 6.
Once again I am hitting the apex to Turn 6. This time
I have a Thunderbird TurboCoupe behind me. Hopefully not
for long.
Going through Turn 6, getting ready to hit the second
apex. Those wheels sure look clean!
Picture of my Dad in my RX-7 the day we picked up my
new race Z in Rhode Island.