Common Questions and Answers

General

Could the turret gunner in the TBM shoot the tail of the airplane?

Not unless the gun is being fired manually. The TBM Avenger was equipped with an electrically operated Grumman 150SE-1 or -2 Ball Turret which has a built in mechanism in the turret ring that prevents firing through a certain arc.

According to the TBM Pilot’s Handbook: “Interrupter cams actuate a micro switch in the gun firing circuit automatically stop the firing of the turret gun when the tail and wing surfaces are in [the] line of fire. The Erection and Maintenance Manual for the airplane further explains how to "zone", or calibrate, the turret by mounting a portable light to the muzzle of the gun to visualize its field of fire and therefore determine dead zones.

A track around the circumference of the turret is shaped to follow the contour of the fuselage. A moveable arm which is electrically connected to the main turret control switch will ride on the track, when the gun is depressed, automatically limiting the angle of depression of the gun as the turret revolves.”

However, in the event of an electric failure, the turret can be operated manually. If this occurs, the Handbook warns: “No fire interruption is provided when the turret gun is fired manually, consequently the gunner must exercise care in pointing the gun so as not to fire into tail and wing surfaces.”

There is one other scenario in which a gunner could inadvertently shoot his own airplane: ammunition cook off. This refers to the situation in which the heat the guns build up from firing could ignite the powder in the bullet casing. While there was no protection against this in the TBM, the B-25 did incorporate an additional safety feature in the event this occurred. On the top of the fuselage there were two small bumps that were directly in line with the guns from the top turret when it was trained directly rearwards. If cook off occurred, these devices – known as “ricochet generators” – would hopefully cause the bullet from the gun to be deflected away from the airplane. The reason this extra effort was taken in the B-25 and not the TBM was because the tail gunner was in the top turret’s field of fire – and while it is one thing to accidentally hit one’s own plane, it is quite another to accidentally shoot one’s own crew.

How do the wings on the TBM fold?

The wings on the TBM are hydraulically folding and controlled by the pilot from the cockpit. However, manpower is necessary to move them the final few inches to allow the tie back cables to be attached.

When the outer wings unfold they swing out and around until they are in line with the inner stub wing. The hinge is mounted on a diagonal, so that as they move forwards they also “rotate” to be parallel with the ground. A tab on the outer wing fits into a slot on the inner stub wing. A pin then slides through a hole in the tab, locking the wing into place. Simultaneously, red “flags” sticking out of the top of the wing are retracted to let the pilot know the wings are locked in position and he is free to takeoff without fear of them folding up in flight.

Roy Grumman, the TBM’s designer, came up with the idea by sticking two paperclips in a soap eraser. Known as the Sto-Wing, it was used on other Grumman designs such as the F4F Wildcat, F6F Hellcat, as well as the postwar E-1 Tracer, C-2 Greyhound, and E-2 Hawkeye.

Why are the wings on the Corsair “bent”?

The Corsair has what is known as an inverted gull wing. It was so called because it was an upside down version of the gull wing – which is itself named after the shape of the wings on a seagull.

The airplane needed long propeller blades to absorb the power of the large Pratt & Whitney R-2800 Double Wasp engine. These blades were so long that they would not be able to clear the ground when the plane took off. One solution was that the main landing gear could be lengthened. However, the Corsair was designed to operate off of aircraft carriers – a situation that involves very hard landings. Longer landing gear were less sturdy. Another option was to use a wing mounted low on the fuselage instead of in the middle. This was also unacceptable, as engineers had figured out that there was a distinct aerodynamic benefit to the wing meeting the fuselage at a 90-degree angle, and a traditional low wing would not allow this. So, to keep the landing gear short, the wing at a 90-degree angle to the fuselage, and still have enough clearance for the propeller, the wings were “bent” downward.

How many planes did an aircraft carrier have?

The most common American aircraft carrier in World War II, the Essex class, carried a total of 90 planes. This was broken down into 36 fighters, 36 dive bombers, and 18 torpedo bombers. This combination of aircraft was known as the “Sunday punch”.

The number of airplanes carried increased throughout the war. At the beginning of 1942, the standard was a total of about 70 airplanes. By mid-1945, that number had risen to approximately 100.

Did World War II aircraft carriers have catapults?

All American non-escort class aircraft carriers had at least one aircraft catapult. However, catapults were not as widely used as they are today. Furthermore, some of the catapults were in unusual locations – such as those in the hangar deck that fired perpendicular to the centerline of the ship.

What happened to spent bullet casings and belt links?

Before answering this question, it is important to distinguish between fixed and flexible mounted guns. Fixed guns cannot be moved and are aimed by turning the entire airplane. They are usually mounted in the wings or nose. Flexible guns can be moved and are aimed by moving the gun itself. An example of this is the tail gun position on a B-25.

During World War II, fixed gun positions on aircraft almost always ejected the bullet casings and links out of the bottom of the aircraft. In rare cases they were collected, such as with the wing gun on the T-6, but this was the exception rather than the rule.

Similarly, in many flexible gun positions, the spent bullet casings simply fell to the floor.

Could drop tanks be used as improvised bombs?

There were some cases of drop tanks being used as improvised bombs, but the tactic was likely not very widespread. This is because drop tanks lack a number of features that reduce their effectiveness in this role.

First, unlike actual bombs, drop tanks lack any sort of fuse or detonator. So when they impact the ground, there is a good chance that they may simply spray fuel everywhere without igniting it.

In addition, generally speaking, drop tanks do not have the stabilizing fins that actual bombs do, making them likely to tumble off course when they are dropped. When combined with the fact that many aircraft with drop tanks do not have bombsights, which makes them hard to aim, it makes them very inaccurate.

However, there were instances where drop tanks were used in this manner. During attacks on the Japanese garrison on the island of Rota in the Mariana Archipelago, Marine Corps Corsairs used drop tanks to destroy a vegetable garden. To solve the problem of ignition, after the first wave of aircraft dropped their belly tanks a second wave fired incendiary rounds into the pooled liquid. The strike was also almost certainly made at low altitude, negating the accuracy problem.

Quite in contrast to their use as weapons, Germany dropped leaflets informing Polish civilians that the large objects they were finding were actually not bombs, but fuel tanks.

How many flying [given aircraft] are there?

It is hard to say with certainty, since the number fluctuates regularly. However, one good metric to use are the reunions and gatherings that have attempted to invite as many aircraft of a certain type as possible.

Some 76 P-51s, or versions thereof, attended the 2007 Gathering of Mustangs and Legends in Columbus, Ohio.

A total of 22 B-25s attended the 2012 Doolittle Raider Reunion at the National Museum of the United States Air Force in Dayton, Ohio. It was quite likely the largest gathering of B-25s since World War II – surpassing even the 17 flying airplanes assembled in 1970 for the filming of the movie Catch-22.

11 TBMs attended the 2018 TBM Avenger Salute to Veterans in Peru, Illinois. Although only 7 TBMs ended up actually being able to make it, for the 2017 reunion as many 16 airplanes originally verbally committed, meaning the total number of flying TBMs was at least that high.

34 DC-3s, C-41s, C-47s, C-53s, and Li-2s confirmed participation for the Daks Over Normandy event in 2019. While it isn’t clear if all of the aircraft were able to attend, it does mean that there were likely at least that many airworthy.

7 Hawker Hurricanes flew in formation at the Shuttleworth Collection Military Airshow in Old Warden, Bedfordshire, England on 7 July 2019.

11 Corsairs took part in the 2019 Thunder Over Michigan air show hosted by the Yankee Air Museum in Ypsilanti, Michigan – although 14 were originally scheduled to attend.

Did the Tuskegee Airmen actually never lose a bomber they were escorting?

No, but whether they did or didn’t isn’t really all that relevant to their story.

The short version is that there were at least 27 B-17s and B-24s lost from bomb groups escorted by the Tuskegee Airmen. At the same time, white fighter groups in the Fifteenth Air Force lost an average of 46 bombers. However, there are many factors that can affect this number, making it difficult to draw definitive conclusions, and the end result is that it unclear whether they were any “better” than any of the other fighter groups.

However, in many ways this doesn’t really matter. The truth does not need to be embellished. What the Tuskegee Airmen did was already amazing enough. Simply by performing their duty they were already doing twice as much as any other American airman. To succeed they had to fight not only Nazi forces in Europe, but also racial prejudices at home. Defeating them both would lead to the hoped for “Double V Victory”.

What was the average height and weight of an American airman in World War II? How does it compare to today? (a.k.a. Were people really smaller back then?)

First, it is useful to remember that the military accepted a range of heights and weights. For example, fighter pilots were permitted to be from 5' 4" to 6' tall and weigh 120 to 180 pounds. When it came to bombers, commissioned officers could be between 5' and 6' 4" and 120 to 200 pounds. However, the average airman was 5’ 9” tall and weighed 154 pounds unclothed.

Often, this question arises in reference to the ability of airmen to fit inside confined spaces – especially ball turrets. The Army Air Force was not unaware of this issue during the war and research in the field of anthropometrics, or the study of measurements of the human body, was carried out. The subject of anthropometrics in relation to gun turrets was already being discussed as early as the summer of 1940 and by December 1941 planning for a survey was underway. Based on this research, in January 1943 an upper limit of 70 inches and 170 pounds was set for gunners.

Interestingly, one of the bigger problems that was encountered was not just the size of the individual person, but also the bulk of the flying clothing and equipment they were wearing. Early enclosed gun turrets were designed at a time when airplanes operated at lower altitudes. This meant that relatively little protection was needed from the elements as the temperature there was warm enough and the air was breathable. However, as technological advanced pushed aerial combat higher and higher, the temperature dropped and the air thinned, making heavy clothing and oxygen masks a necessity. Yet turrets were still being designed without consideration for the amount of space that these new provisions were taking up. As an example of bulk of this equipment, the standard uniform, electrically heated suit, and oxygen system alone added just under 30 pounds.

An interesting demonstration of the importance of anthropometrics comes from the experience of Women Airforce Service Pilots (WASPs). When they joined there were no women’s uniforms available and as a result they had to make due with oversized men’s mechanics coveralls they nicknamed “zoot suits” after the popular fashion trend of the time.

How dangerous was the ball and/or tail gun position?

According to an analysis of casualties suffered by the Eighth Air Force from June to August 1944, the crew position with the greatest chance of being injured or killed was the bombardier followed by the navigator. The tail gunner was third most dangerous and the ball turret gunner was actually the safest position.

Did the Doolittle Raiders replace the tail guns in their B-25s with broomsticks?

Not exactly. The B-25Bs used on the raid did have twin broomsticks placed in the rear of the airplane as a ruse. However, stock B-25Bs did not have tail guns installed, so the broomsticks did not replace existing guns, but added them where there had not been any before.

This is an important distinction because in the 2001 movie Pearl Harbor it is suggested that the guns were replaced to lighten the weight of the airplanes. In addition, it is presented as a decision that was made on the spur of the moment, when it fact it was actually made at Eglin Air Force Base – long before the B-25s were ever aboard the USS Hornet. To further confuse matters, the movie depicts the guns being replaced as the waist guns, not those in the tail.

Did the phrase “the whole nine yards” really come from the length of machine gun belts in World War II?

No, there is attested usage of the phrase, or a very similar variation, that predates World War II.

Did WASPs ferry airplanes overseas during World War II?

No, although it was attempted on one occasion. To quote the book WASP of the Ferry Command:

Then on September 1, 1943, Nancy and Betty left Cincinnati in B-17F (No. 42-30624) on the first leg of the trip. With them were 1st Lt. R.O. (Pappy) Fraser, navigator; T/Sgt. Stover, radio operator; T/Sgt. Sidney Weintraub, aerial engineer; and T/Sgt. L.S. Hall, assistant aerial engineer. The plane was destined for the U.S. Eighth Air Force in Great Britain. After some delays, they landed in Goose Bay, Labrador, on September 4. Much of their trip from Presque Isle, Maine, had been under instrument conditions.

They never look off from Goose Bay. General C.R. Smith, thinking the two women and their crew were well on their way, sent a wire to England alerting the commander of the ATC European Wing, Brig. Gen. Paul Burrows, that the plane flown by the two women pilots was on its way, and to notify General Arnold.

Routine delivering flight arriving in your wing will be B-17 number 30624 in few days. For Burrows and Atwood from Smith. Airplane is piloted by WAF crew first pilot Nancy Harkness Love and second pilot Betty Gillies. … Desire General Arnold be informed.

The telegram was delivered while Burrows was having dinner with his boss, Hap Arnold. Burrows handed the telegram to Arnold who immediately ordered the flight stopped. The following is Arnold's message:

Just have seen message from C.R. Smith … indicating that a B-17 with women crew will leave for England shortly. … Desire that this trip be cancelled and no women fly transoceanic planes until I have had time to study and approve.

Passengers Nancy Love and Betty Gillies boarded a C-52A in Goose Bay the morning of September 6, 1943. The flight was bound not for Prestwick, Scotland, but back to Presque Isle, Maine. They were going home. Two male pilots took their places and ferried B-17F No. 42-30624 on to Scotland.

“If we had left the day before–when we were scheduled to leave–we'd have been in England before General Arnold ever heard,” Betty recalled years later. “But the weather was bad and we couldn't get clearance.”

That was the first and only attempt to have WASP pilots ferry aircraft overseas during the war. Stories do circulate that service men saw women pilots delivering airplanes in both the Atlantic and Pacific theaters, but no WASP ever did so–and they will all tell you that, in no uncertain terms. Yes, the women flew to and all across Canada and, though not generally known, two WASP flew to Puerto Rico in December 1944.

How accurate was the Norden bombsight?

The legend of the Norden bombsight’s accuracy results from the famous claim that a bombardier using the device could “drop a bomb in a pickle barrel from several thousand feet”.

It is illustrative that as early as December 1940 this claim was both being exaggerated and questioned. One news article notes that in recent retellings, the altitude in the quote had increased from 10,000 to 30,000 feet and the pickle barrel had been replaced with a “flower pot”. Another states that “the accuracy claims in stories published six months or so ago about the Sperry bombsight seems to have been greatly overdrawn”. A third from February 1940 – presumably one of the ones being referred to above – makes the unrealistic claim that the Sperry bombsight allows a bomber to drop bombs “while the plane is actually maneuvering, banking, rolling, etc.”

While these stories apparently describe the earlier “Sperry [S-1] bombsight” and not the later “Norden”, they do capture the general spirit of the times and the sense that the rumor mill surrounding both of them had taken off.

The reality was that accuracy was far worse. In 1943, “only 16 percent of bombs fell within 1,000 feet of the aiming point”. By 1945, however, this had increased to 60 percent.

How secret was the Norden bombsight? Was the secrecy effective?

The Norden bombsight was actually compromised before World War II ever began. Herman W. Lang, an inspector in the Norden factory, passed blueprints to the Germans in 1938.

As a matter of fact, it is likely that the secrecy surrounding the Norden bombsight stemmed more from Carl Norden’s desire for exclusive government contracts then any attempt at preventing the device from falling into enemy hands. By ensuring the bombsight’s secrecy, he made sure that his competitors – mainly the Sperry company – could not obtain a license to build it. Eventually, the secrecy “took [on] a life of its own” and mushroomed into the myth that is common today.

It is important to note, however, that despite the excessive secrecy, the security measures during the war were taken seriously and sincerely believed by most servicemen.

An illustrative example of the difference between fact and fiction can be found in the instructions on what to do with the bombsight in the event the bomber was shot down. The bombardier handbook did dictate that the bombsight be destroyed and that the correct method was to shoot it three times with a pistol and then throw it overboard. However, contrary to what is often claimed, the bombsight itself incorporated no provision for an incendiary device to “melt it into an unusable lump of metal”. Aircraft did sometimes carry such AN-M14 incendiary grenades, but the manual clearly states that they are intended for “DESTRUCTION OF THE ENTIRE PLANE”, not the bombsight.

Furthermore, it is worth noting that these type of instructions are in no way isolated to the Norden bombsight or heavy bombers. For example, handbooks for ground based radio sets included similar language on when and how to destroy the equipment to prevent enemy capture.

Did pilots always fly the same airplane?

It depends. Pilots with more prestige, in other words those with a lot of kills or unit leaders, were more likely to have a personal airplane.

Frequently, pilots were more concerned with the opposite: avoiding being forced to fly the "squadron hack". Squadron hacks were aircraft restricted from combat missions because they were obsolete or beat up. They were sometimes pushed of the side of the airfield where they served as a "parts bird" that was scavenged from to keep the other airplanes flying. However, if one of the regular aircraft suffered a malfunction, a pilot might have to fly one as a backup. The lack of care and maintenance, however, made this a risky proposition. The book Black and White Airmen states:

Crews always had favorite aircraft, but except for the special Pathfinder ships, no crew had a guarantee of their "own" plane. When the squadron’s original crews landed in England in 1942, every B-17 commander had a "personal" aircraft, usually with a sweetheart’s name or a racy pinup picture or a slogan painted on the nose. As those planes were damaged or their crews went home, they passed into a general pool to be patched up or refitted for newcomers. Replacement crews quickly learned which B-17s were the trusty ones and which were the dangerous "crates." The more missions you flew, the more likely you were to get a plane you trusted or even a brand-new B-17G.

How did the Allison V-1710 and Rolls-Royce Merlin compare?

To quote the book Vee's for Victory:

The Allison V-170 and the Rolls-Royce V-1650 liquid cooled V-12 aircraft engines were really very many different engines. The active production period for each extended for nearly 15 years. A large number of variations of the engines were built to meet the needs of military tacticians related to the key rolls both engines played during the war. Both engines were needed, and while one particular model or another was preferred for a given mission, not every airplane, and not every engine, should be expected to perform every mission with equal superiority or effectiveness.

The V-1710 was designed to be a two-stage engine, albeit, with the first stage being a turbosupercharger. When pressed into service as a single stage power plant it should not be a surprise that it would be "altitude" limited. Power ratings were quite similar once the U.S. military allowed WER ratings, the V-1710 was able to equal or exceed comparable Merlin performance.

Although the V-1710 had a four year headstart in design and testing, the Government funded Merlin benefited from the experienced Rolls-Royce development team. They had the engine ready and with it the Battle of Britain was won. At that point in time, the V-1710 had just gone into series production. Furthermore, Rolls-Royce was able to grow the capabilities of the engine with their masterful arrangement of superchargers and aftercooling to provide a compact two-stage engine that was able to establish air superiority over both Europe and Japan. Allison was able to match this performance, but was never able to get its most advanced engines into production combat aircraft during the war.

What were the standard sizes of ammunition used by aircraft during World War II?

While there are countless variations, almost all rounds using on aircraft during World War II came in one of eleven sizes. In order of increasing diameter, they are:

• 7.62 mm (.30 cal) – American, British, Soviet
• 7.7 mm – British, Italian, Japanese
• 7.92 mm – German
• 12.7 mm (.50 cal) – American, British, Italian, Soviet
• 13 mm – German
• 15 mm – German
• 20 mm – American, British, Italian, German, Japanese, Soviet
• 23 mm – Soviet
• 30 mm – German, Soviet
• 37 mm – American

In the jump from 13 mm and 15 mm, there is an important change in the makeup of the projectile. Until that point, the weapons are machine guns with bullets – that is to say they are simply solid pieces of metal. However, above it they are autocannon with shells, which means they have a small internal explosive.

Choosing the correct size of round was a balance. Smaller rounds had a higher rate of fire and higher muzzle velocities, but were less damaging. Larger rounds, the opposite. These characteristics influenced how each type were used.

When attacking small, maneuverable aircraft the engagement window – the time one has to shoot at the enemy – is very short. Therefore, high rates of fire are preferred to put as many rounds in the air as possible to increase the chance of a hit. On the other hand, larger aircraft, such as multiengine level bombers, are slow and lumbering, but can absorb more damage due to their larger size. In this case, a heavier round is better, as it takes less hits to bring down an aircraft and the target will likely not attempt to dodge.

In turn, as a result of the situations they faced, different countries favored different rounds. Britain discovered early on in the Battle of Britain that the rifle caliber 7.7 mm guns in their Spitfires and Hurricanes lacked the stopping power to be effective. As a result, they quickly added 20 mm autocannon to their new aircraft. Germany and Japan would come to the same realization as they found themselves under attack from Allied bombers later in the war. As their situation grew desperate, they increasingly focused on the development of heavy autocannon and by 1945 were fielding weapons of 30 mm.

The United States, never at risk of a bomber attack and facing mainly other lighter aircraft, stuck with the .50 caliber throughout the war. Furthermore, when facing an enemy such as Japan, whose aircraft were comparatively lightly built, a larger round would have been overkill.

Some countries, notably Germany and the Soviet Union, also developed guns for ground attack.

The postwar era saw near universal worldwide adoption of autocannon and today almost all fighters have guns in the 20 mm to 30 mm range.

How did crews go to the bathroom in an airplane?

Depending on the type of airplane, there were a couple different ways pilots could relieve themselves. Some single seat aircraft had a "relief tube" under the seat that could be pulled out and urinated into. It consisted of a funnel attached to a rubber hose that led to a Venturi tube mounted on the outside of the fuselage. Larger, crew served aircraft such as medium and heavy bombers actually had a toilet seat. The British Avro Lancaster featured a chemical toilet called the "Elsan". In B-25Cs and Ds, the toilet even doubled as a riding seat for the operator of the aerial camera that was mounted in the floor.

However, the problem with sit down toilets is that they take up a lot of room for a piece of equipment that has a very limited use and so were often just not included. For example, later variants of the B-25 disposed with the toilets along with the camera mounting. In aircraft without a toilet, crews would either defecate into a leftover box such as an ammunition crate that could be thrown out of the airplane or go out of the open bomb bay. For this reason it could be argued they were really unnecessary anyway.

The high altitudes at which the aircraft operated could cause some unusual problems, however. The cold temperatures could cause relief tubes to freeze, rendering them unusable. Even if the urine did manage to successfully leave the aircraft, it could still cause problems. On B-17s, the tube discharged out of the bomb bay and a failure to warn the ball turret gunner could result in his view out of the front of the turret being obscured by a frozen yellow liquid. In at least one other case, a B-17 farther back in the formation was hit in the windscreen by a discarded box containing what was left of the crew's morning meal.

Dedicated toilets for larger aircraft eventually became standard for two reasons. First, as their size and power increased the space and weight penalties of the equipment were less of a problem. In addition, aircraft began using pressurization and the requirement for a sealed aircraft made it impossible to simply open a hatch to dispose of unwanted material.

Airplane Design

What is “hand-propping”?

“Hand-propping” is a method of starting the engine on an airplane used when no automatic starter is present. To do this the pilot exits the airplane, walks to the front, grabs hold of the propeller, and gives it a yank to start the engine turning over.

It is the equivalent of using a hand crank to start a car. While it is generally regarded as old fashioned in both the aviation and automobile worlds, it is much more common to come across an airplane that need to be hand propped, than it is a car that needs to be hand cranked.

It is important to note that as soon as the propeller starts turning the airplane will want to move forward. Not fast enough to take off, but often fast enough to make it impossible to get back in the cockpit. Therefore, before hand-propping an airplane, the pilot must take one of two precautions. If flying alone, they will tie down the tail in such a way that it can be released after entering the cockpit. If flying with another person, that person will simply hold down the brakes with their foot.

Why do airplanes have three power plant control levers?

The pilot of most World War II airplanes had to manage three different aspects of its power plant: the fuel flow, the fuel mixture, and the propeller pitch.

Consider that, in a modern car with an automatic transmission, there is only one acceleration control for the driver – the gas pedal – which controls the throttle.

The Fw 190 famously had an advanced engine control unit called the “Kommandogerät” that automatically managed a number of various settings in such a way that only a single throttle lever was necessary.

What is the benefit of a variable pitch propeller?

On a variable pitch propeller the angle of the blades can be changed – usually in flight. This is contrasted with a fixed pitch propeller, on which the angle of the blade is fixed.

A variable pitch propeller performs much the same function as the transmission on a car, with each different angle being similar to a different gear. Therefore, flying an airplane with a fixed pitch propeller would be like driving a car with only a single gear.

What is the benefit of reduction gearing?

To quote an advertisement by Pratt & Whitney:

The employment of a reduction gear secures better propeller efficiency by reducing the speed of the propeller. Further, on air transport ships the practise [sic] adds to passenger comfort by reducing propeller noise.

What are the tradeoffs between inline and radial engines?

Inline and radial engines each have their own benefits and certain countries and military branches tended to have their own reasons for preferring one over the other.

On the one hand, inline engines have less drag, increasing the speed of the airplane. However, it was impossible to sufficiently cool the rear cylinders because the airflow was blocked by the ones in front of them. Therefore, inline engines needed a liquid cooling system. This added additional complexity to the engine. In addition, if the liquid cooling system was to fail for any reason – say, due to loss of coolant from battle damage – the engine would quickly overheat and seize. In contrast, aircraft with radial engines were known to return to base with entire pistons shot away.

What is the difference between a rotary and radial engine?

Rotary and radial engines are often confused and their names interchanged incorrectly. Simply put, in a rotary engine the entire cylinder block rotates around a fixed crankshaft, while in a radial engine the cylinder block is fixed and the crankshaft rotates.

Why do radial engines leak oil?

The cylinders in a radial engine are arranged in a circle around the crankshaft, so the cylinders on the bottom of the engine are upside down. Over time gravity causes the oil to drain from the upper cylinders down to the lower ones, where it collects. Since the cylinders on the bottom are upside down, and the valves and seals are not designed to contain it, the oil leaks out around them.

If enough oil pools in the lower cylinders, it can result in a condition called “hydrolock”. Hydrolock occurs when a fluid, such as oil, builds up in the combustion chamber of a cylinder. Since the fluid is nearly incompressible, the piston cannot complete its full stroke. Depending on the amount of force applied, attempting to turn the engine over will either be impossible or result in damage.

This is the reason that propellers on aircraft with radial engines are “pulled through” before a flight. Doing so allows the crew to check whether hydrolock has set in. Alternatively, it may be performed as a preventative measure on aircraft that have not been run in a while to recirculate the oil throughout the engine.

Why do some aircraft have folding wings?

Folding wings are found almost exclusively on naval aircraft. There is a limited amount of space onboard an aircraft carrier, so folding wings allow multiple aircraft to fit in the space that a single non-folding wing design would take up.

However, parked footprint is not the only consideration as there are other size constraints on the ship. For example, aircraft must also be able to fit on the elevators that move them between the hangar and flight decks. This is why aircraft like the Mitsubishi A6M have folding wingtips: a feature which is not particularly useful for increasing aircraft capacity due to the small amount – only 20 inches – of wingspan reduction.

What kind of armor did World War II airplanes have?

The two most common places for armor in a World War II aircraft are the windshield directly in front of the pilot and the seat directly behind him.

Generally speaking, you are far better off trying to avoid the hit than absorbing the damage it causes. Additional armor meant additional weight, which meant reduced speed and maneuverability. For that reason, armor was normally kept to a minimum.

However, certain aircraft did carry additional armor. Usually, it was those that operated in conditions where being hit was seen as unavoidable. The first type of aircraft that fell into this category were those that couldn’t maneuver. This encompassed aircraft such as heavy bombers, that had to remain in formation. The other category were aircraft that flew in areas where the volume of fire was so high that the aircraft would inevitably be hit. These were ground attack aircraft, where multiple anti-aircraft guns would be firing at a single target. This resulted in aircraft like the Soviet Ilyushin Il-2, which famously had heavy steel plate around the engine, fuel tanks, and all sides of the pilot.

Specifications

How many rounds did planes carry?/How long could the guns fire?

The most common gun used on American aircraft during World War II was the Browning AN/M2 .50 caliber machine gun. It had a fire rate of 750 to 850 rounds per minute. The number of rounds carried varied based on the type of aircraft and mounting. The P-51D, for example, carried 400 rounds on each of the inboard guns and 270 rounds for each of the center and outboard guns. So a P-51D pilot had a maximum firing time of 30 seconds (400 rpg / [800 rpm / 60 s]) – although four of the six guns would only last just over 20 seconds.

In the Pacific, pilots complained when the new “-4” variant of the F4F was introduced. Compared to the “-3” variant it added two additional guns, bringing the total to six. The additional guns reduced the total number of rounds per gun, and therefore the total firing time. Noted pilot Jimmy Thatch argued that, “the pilot who will miss with four .50-caliber guns won't be able to hit with eight.”

Other Questions

How long does a dogfight last?

Most dogfights, as aerial battles between two airplanes are known, happen very quickly. In fact, according to one study, “roughly 80% of all fighter victims in war are shot down unaware of their attacker”. In other words, 80% of all fighter combat has an effective duration of 0 seconds.

It must be remembered that aerial combat is extremely physically exhausting. Fighter combat often involves pilots “pulling” multiple Gs that multiply their body weight many times over. In addition, before the invention of boosted controls, the only force the pilot had to move the control surfaces was his own brute strength.

To get an idea what this is like, consider the closest common civilian equivalent: a rollercoaster. Rollercoasters subject their riders to rapid changes in positive and negative G. However, on a rollercoaster the rider is merely a passive participant – they are not required to do anything. In contrast, in a dogfight the pilot must actively control the airplane as well as keep track of the enemy and constantly plan the next maneuver he has to make.

However, extremely long dogfights did take place. In one case, an SBD piloted by “Swede” Vejtasa fought three A6Ms for 17 minutes.

Why is piloting a tail wheel airplane so difficult?

A tail wheel airplane, often called a taildragger or conventional landing gear, is an airplane where the centerline landing gear is positioned behind the two main landing gear located further outboard.

There are two main reasons flying a tail wheel airplane is difficult: center of gravity and lack of visibility.

The key to understanding the center of gravity issue is that on a tailwheel airplane it is located behind the main landing gear and that this can cause something called a "ground loop".

A ground loop occurs when the nose and tail of the aircraft "swap ends" while taking off or landing. In other words, the aircraft rotates 180 degrees (or more) so that its nose is no longer facing the direction of travel. If not immediately corrected, the aircraft will either go off the runway, have the landing gear fold under due to the side load, or both. The end result is, of course, serious damage to the aircraft.

If a pilot were to stomp on the brakes in an airplane with a tailwheel, the remaining forward momentum would cause the tail to lift up until the airplane comes to a rest on its nose. In severe cases, it could even cause the airplane to flip over completely. This is the same force that causes a rider to go over the handlebars on their bicycle when they stop too fast.

The main landing gear of a tail wheel airplane is longer than the tail wheel. This results in the plane having a nose high attitude on the ground. On airplanes with a large engine in front of the cockpit, the pilot's view forward is blocked. On the ground this can be somewhat mitigated by performing "S-turns" where the pilot swings the airplane from left to right and back again to gain a glimpse out of the side of the canopy to see the taxiway ahead. A similar technique, using a curved approach, can be employed when landing. However, neither of these is a perfect solution and require skill to be performed properly.

For the reasons above, most modern aircraft use tricycle or nose landing gear configuration. This transition began during World War II and was apparently significant enough of an problem for pilots that the Army Air Force issued a technical order explaining the differences between the two different configurations.

What does "sloshed/suitable for aromatic fuel(s)" mean?

A substance is "aromatic" if it has a "noticeable and pleasant smell". When used in context of fuels, it refers to a category of chemical compounds related to benzene that were historically grouped together due to the fact they had a common smell.

These types of compounds were added to aviation fuels during the war because they increased engine performance. However, they were also highly corrosive and if certain parts of the fuel system of an aircraft were not specially treated, specifically the rubber used in seals and self-sealing fuel tanks, it could cause damage.

The aircraft that had this treatment therefore had a note added to the technical data block on the side of the fuselage that it was safe to use these type of fuels in them.

What is the process before takeoff?

1. Pulling propeller through

   • Before they even enter the airplane, the pilots will pull and push the propellers through a certain number of complete rotations to ensure that the engines are not hydraulically locked. If this were the case, when attempting to turn them they would reach a point that they could not move any further.

2. Pre-start checklist

   • There are a variety of settings and instruments to check to ensure they are properly configured before starting the engine. This is performed via "call and response" between the pilot and copilot in the cockpit, so the only evidence of this from the ground will be a delay where it appears nothing is happening.

3. Ground power (optional)

   • Although most World War II aircraft have a battery to power their electrical starter, they can also be started using a "battery cart" that plugs into the side of the aircraft. This lessens wear on the battery. Once the engines are started, the cart is unplugged by a member of the ground crew.

4. Bumping the propellers through

   • The pilots will then slowly rotate the propellers with the engine starter to check again that the engine is not hydraulically locked. As they do so, they will "count blades" to make sure that every cylinder has gone through compression.

5. Call "Clear!"

   • This callout alerts anyone on the ground that the engines are about to start and they should clear the area.

6. Engine start

   • The engines will initially exhaust a large amount of smoke before clearing up. This is the result of the extra oil in the cylinders being burned off. The amount and duration of smoke will therefore generally depend on how long the airplane has sat since its last flight.

7. Oil temperature wait

   • Much of the time spent on the ramp before the airplane starts rolling is waiting for the engine oil to warm up. When cold, oil is more viscous and attempting to push thick oil through an engine can result in a failure of some component.

8. Control surface checks

   • The control surfaces are moved to their fullest extent of travel in each direction to ensure that they are not blocked.

9. Magneto checks

   • Piston aircraft engines have two magnetos and for redundancy each controls one of the two spark plugs per cylinder. The pilots will briefly switch off both magnetos to confirm that they are working properly. This step, called idle ignition grounding, ensures that the engine can be shut down if necessary and results in it briefly sounding like it is cutting out.

10. Taxi out

    • The aircraft leaves the ramp and taxies to the end of the taxiway.

11. Run up

    • Once the aircraft reaches the end of the taxiway, the throttles are briefly advanced to near takeoff power before being brought back down again. This serves the same purpose as the control surface check, but for the engines.

12. Takeoff

This guide is written for the benefit of a person watching the airplane from the ground. As a result, it omits or simplifies certain steps in the process that are not evident from this position. Furthermore, it is written in reference to a B-25, but while there are minor differences from airplane to airplane (e.g. number of pilots and engines), the steps are generally similar. Third, while certain steps must occur in a specific order, a few can be performed at different points between the aircraft leaving the hangar and takeoff.

What does it take to fly warbirds?

It varies based on which aircraft is being referred to, but the following Federal Aviation Administration (FAA) restrictions apply to a at least one of a representative sample of World War II aircraft:

• Complex – an aircraft that has two or more of the following features: flaps, retractable landing gear or a variable pitch propeller
• High-performance – an aircraft with an engine that produces more than 200 horsepower
• Multi-engine – an aircraft with more than one engine
• Seaplane – an aircraft that can operate on water
• Tailwheel – an aircraft with a centerline landing gear behind the main landing gear
• Type rating/letter of authorization – an aircraft with a maximum gross takeoff weight of 12,500 pounds or greater

The following table is presented in lieu of a detailed explanation of the requirements for each airplane:

	Complex	High Perf.	Multi	Seaplane	Tailwheel	Type
AT-6	✓	✓			✓
B-25	✓	✓	✓			✓
C-45	✓	✓	✓		✓
FG	✓	✓			✓
Fw 190	✓	✓			✓
L-4					✓
P-40	✓	✓			✓
P-51	✓	✓			✓
PBY	✓	✓	✓	✓		✓
PT-17		✓			✓
PT-22					✓
TBM	✓	✓			✓	✓

Multi-engine, seaplane and type are ratings and complex, high-performance and tailwheel are "endorsements". The complex endorsement requires a private pilot's license, but high-performance and tailwheel do not.

Aside from the actual training, earning an endorsement is relatively simple, as it only requires a signature from a qualified instructor in the applicant's logbook.

While they are not listed on the back of the physical card and do not require a commercial license, aviation endorsements are otherwise comparable to the endorsements on a driver's license in that they are additions to a license rather than an entirely separate level of license.

Obtaining a type rating requires both access to an aircraft of that type and a designated pilot examiner, or DPE. As the number of flying warbirds are limited and the cost of operating them is high, doing so can be quite expensive. Therefore, it is not uncommon for organizations to "sponsor" a pilot – that is to say, pay for their training. However, because of the significant outlay, an informal commitment is generally expected of the pilot to fly for the organization.

Aside from a tailwheel endorsement, anyone who can fly one of the Cessna 172s on the other side of the airport could fly the L-4 or J3. In fact, in a way these aircraft require less, as they are lightweight enough, less than 1,320 pounds, to be considered "light sport aircraft". This means they can be flown with a sport pilots license, which has less stringent requirements than a private pilot's license.

References