Jug Time

by Jim "Twitch" Tittle

Article Type: Military History
Article Date: January 17, 2003


After a tour in B-17s over Europe Major Peeples requested assignment to a fighter squadron, the 44th Air Depot Group at Wattisham in the spring of 1944. Peeples hadn’t flown a single-engine plane since his training in the BT-13 so the P-47D was quite a transition.

The usual intimidation occurred when he climbed into the huge, round fuselage and stared over the immense nose with its 2,300 HP Pratt & Whitney 18-cylinder. Peeples eventually rotated back to the States and got some time in the “N” model in 1947 on Guam. Major Peeples was based at Harmon field, Guam as a test pilot in 1947-48 where 35 standard Ns and two with no armor or armament were used for proficiency flights.

The Thunderbolt’s broad wing spanned 42.5 feet. The barrel fuselage, where the “Jug” moniker came from, was 36.3 feet long. This model was 11,000 lbs. empty, 16,300 lbs. loaded and could tip the scales at 20,700 lbs fully loaded. A factory test pilot got one off at 22,500 lbs. The 2,300 HP P & W of the D was replaced by a 2,800 cubic inch (45.9 liter) 2,800 HP R-2800-57C Wasp Major 18-cylinder that weighed 2,350 lbs. Some other engines of similar power were used with 73C or 77C designations.

R-2800 -Put out 3,600 HP in testing

An exhaust-driven General Electric CH-5 turbo-supercharger with “War Emergency Power” water injection into the intake manifold permitted 72 inches of manifold pressure at 2,800 RPM. “Dry” the engine put out 2,100 HP with 54.5 inches of manifold pressure. With a high compression engine running full bore, detonation or knock would occur. It is a fault of the fuel not burning properly within the cylinder. When some would burn too fast it would “explode” instead of burning smoothly causing knock or ping. The injection of water evened out and cooled the mixture to make for smooth burning and more usable horsepower at least for a short time.

Different than most fighters, the two-stage turbo-supercharger was located in the lower, aft fuselage. The Curtiss 836 electric full feathering, constant speed, four-blade prop had a diameter of 13 feet. When the tail was up and level the prop had only three inches of ground clearance.

The main fuel tank held 270 gallons with an auxiliary 100-gallon tank and 100 gallons in each wing. No more was the P-47 short-legged. All tanks were self-sealing. With a belly tank of 75 or 110 gallons plus two underwing tanks of 110, 165 or 300 gallons. On internal fuel alone it could fly 1,500 miles. With the 165-gallon tanks 2,350 miles was possible and with the 300-gallon babies it was a tad over 3,000 miles! The N could take 1,280 gallons of fuel. During the war N pilots escorted B-29s from Guam and Saipan to Japan and back making for twelve-hour-long missions mostly over water!

The N actually had a General Electric G-1 auto pilot. My friend Fred Christiansen told me of his first flight-testing the N after returning from the ETO with 21.5 victories. Near the Farmingdale New York plant he set the thing all on zeros and the crate promptly was upside down.

Production Ns being test flown near Farmingdale

A K-14 gyro gunsight was used to aim the eight .50 caliber Browning M2 machine guns. Loads varied from 267 rpg to 425 RPG. Two 1,00 lb. or three 500 lb. bombs plus ten 5-inch rockets could be carried. Actually three 1,000-pounders could get off the ground under the P-47N. an AN/APS-13 tail warning radar was fitted.

Peeples mentioned that handling felt similar to the D though some pilots thought it was more sluggish heavily loaded and the roll rate was lower. Major Peeples only flew Ns lightly loaded so could offer no personal insight. Ns were visually identifiable over all other models since the two-foot larger wing was squared off at the tips.

The N, like other P-47s, needed positive elevator trim for nose up attitude with power applied to pull out of dives when compressibility was reached. And only when the air was thick enough did the Jug respond and nose up. Peeples felt the control input to movement was superb. “It seemed that you only had to think ‘right turn’ and you were in a right turn without having moved the controls. Rolls and wingover were heavenly to the point of joy.”

“Landings were easy except for the visibility when in a three point attitude with no tendency to drop a wing, he declared.

“Climb “dry” (no emergency power) in a clean plane at 2,800 RPM at 54 inches manifold pressure got the N to 30,000 feet in seventeen minutes. At 2,600 RPM and 45 inches it took twenty-two minutes. With two 165 gallon tanks at 2,800 RPM and 54 inches it took twenty-eight minutes,” he recalled.

Hot

The Jugs usually lost mock dogfights with Marine F4U Corsairs based on the island. The P-47s were restricted in the use of the water injection too. On one flight in the stripped down Thunderbolt, weighing some 2,000 lbs. less than normal, with only 350 gallons of fuel aboard he engaged one though.

“I noticed a Corsair approaching me at an angle and slightly higher than my 4,00 feet. Suspecting he was going to bounce me, I added power to get about 280 IAS (indicated air speed). He turned and closed on my left wing and made the circling motion with his hand indicating “dogfight.

“I knew he was accustomed to outclimbing Jugs so I pointed up vigorously several times and I saw him laugh. I hit he throttle- all the way-(water injection engaged) 2,800-RPM and 72 inches. The N howled upward with the rate of climb indicator off the scale. The Corsair was left like he never started the climb. I hit 10,000, chopped the power in a quick wingover and met him still coming up. That was one surprised Marine!”

Peeples said, “Flying those light ships was wonderful. They leapt off the runway before you could open the throttle all the way at 2,000 RPM and 34-35 inches and hit 270 IAS at low altitude right away.”

In 1949 back in the States, Major Peeples taught a lesson to a P-51H pilot who’d made disparaging remarks about the Jug before he took off. When the P-51 was turning 90-degrees off the takeoff line Peeples made a full power takeoff.

“After the gear came up I held the N to about 200 feet until 300 came up. I’d kept an eye on the 51 who was now parallel to the runway. He’d lost sight of me cause I heard him ask the tower if I was off yet. At 300 IAS I tipped the left wing and eased into a smooth chandelle, rolled out and chopped power right on his tail! I eased over and slid up on his wing to say 'Hi!' He never got over it.”

The N wing that assisted range came from the third P-47M in that test program as the XP-47N numbered AC42-27387. $101,000 was expended for the wing fabrication in mid-1944. A P-47C-5-RE, number 41-6601 was fitted with the new wings for testing and it was referred to in Republic correspondence as P-47C-707.

XP-47

The idea was to put the wing in production in three months. It was vital since it was expected to add 1,000 miles to the range of the Jug. In reality the N was simply an M with eighteen-inch wing extensions and more fuel. By the same token, the hot rod M model was the N with P-47 D wings. It had 570 gallons, up 200 from the D without the internal wing tanks The P-47N was given a “go” on August 7, 1944 and the General Motors P-75 Eagle project pretty much bit the dust.

XP-75

The P-47N-5-RE hit 397 MPH at 10,000 ft., 448 MPH at 25,000 ft. and 460 MPH at 30,000 ft. Climb rate at 5,000 ft. was 2,770 FPM and at 20,000 it was still 2,550 FPM. 42,000 feet altitude could be reached. Sub-models up to the P-47N-25-RE, which used that later R-2800-77C engine were produced. Of interest to note, when the 2,800 cubic inch engine was tested on the torquemeter it measured 3,600 HP during 1943 testing. So more was possible.

The N had a 36-inch wider track width on the landing gear. The larger wing upped the 300 square foot wing area from all other models to 322 sq. ft.

Most of the Ns were destined for Far East deployment. 1,667 were built at the Farmingdale, New York facility and 149 at the Evansville, Indiana plant.

But that’s not quite the end of the Thunderbolt story though the N was the last production model. Back when the P-47B came to life in 1940 designer Alexander Kartveli began work on the XP-69 and XP-72. The XP-69 Wright R-2160-3 of 2,500 HP and the XP-72 a Wright R-4360-13 28-cylinder Wasp Major with 3,450 HP! The experimental R-2160-3 had 42-cylinders. It was located aft of the pilot like the P-39 with a shaft driving contra-rotation props. Weaponry for the strange plane was to have been two 37mm cannon and four .50 caliber machine guns. The more conventional XP-72 was chosen for development.

XP-72 with 6-blades

The XP-72 looked quite like the experimental XP-47J owing to the belly scoop though it had a bubble canopy that the XP-47J did not. The XP-72 design was begun as soon as the P-47B was finished and flew on February 2, 1944 with a four-blade prop but the 2nd prototype had a six-blade Aero Products contra-rotating affair. Power to turn those props came from the 28-cylinder R-4360-13 with 3,450 HP using a two-stage mechanical turbo-supercharger.

Compressibility flaps were installed on the standard, 300 sq. ft. wings. Six fifties with 267 RPG were mounted but four 37mm cannon could be substituted. Two 1,000 lb. bombs could be carried.

Maximum speed was 490 MPH at 25,000 ft. and range at 300 MPH was an optimistic 1,200 miles. This could be increased to 1,530 miles with two 150-gallon drop tanks. Initial climb rate was a staggering 5,280 FPM and at 25,000 ft it was still 3,550 FPM. 5,000 ft. was reached in 3.5 minutes and 20,00 ft. in 5.0 minutes. Dimensions were the same as the D-model Jugs but weights were 11,476 lbs. empty, 14,433 lbs. normal and 17,490 lbs. maximum even with the big engine. A lot of weight-saving engineering was done to accomplish it. With the need for range and advent of the P-80’s impending debut the project calling for 100 examples was cancelled with just two planes ever made.

P-47N seen with the Republic XF-12

A P-47N seen with the Republic XF-12 above shows size differential with this prototype recon ship. Known as the RC-2 "Rainbow" it was competitor of Hughes XF-11. It had four Wasp Majors and was fast.

After official U.S. military service, the National Guard used P-47Ns sometime past 1950. The Fuerza Aérea del Peru operated two squadrons of F-47Ds with a few Ns as late as 1968. But the P-47 served with the air forces of Bolivia, Brazil, Britain, Chile, Dominican Republic, Ecuador, France, Honduras, Iran, Italy, Mexico, Nicaragua, Turkey, Venezuela and Yugoslavia as F-47s in the post WW II era.

More than one individual or group purchased retired Thunderbolts from Latin American air forces for restoration in the U.S. Some still fly today at air shows around the country.

Sources

• Air Age Technical Staff
  Republic P-47 Thunderbolt
  Air Age, Inc. NY, 1958
  
  
• Bodie, Warren, M.
  Whine From the Jug
  Airpower July 1974
  
  
• Dorr, Robert, F.
  US Fighters of WW II
  Arms & Armour Press, London, 1991
  
  
• Green, Wm.
  The Complete Book of Fighters
  Smithmark Publishers, NY, 1994
  
  
• Green, William
  Fighters Vols. 4
  Doubleday & Co., 1960
  
  
• Training Service Section - General Motors War Products
  “A Power Primer”
  General Motors Corp., Detroit, 1944
  
  
• Westburg, Peter
  The Mighty N
  Air Classics February 1975

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