physics - B-17 Flying Fortress

A B-17 nicknamed Sally B in England in 2001

The Boeing B-17 Flying Fortress was the first mass-produced, four-engine heavy bomber. It is still one of the most recognised aeroplanes ever built. It was most widely used for daylight strategic bombings of German industrial targets during World War II as part of the United States Eighth Air Force.

Contents

1 Development

2 Operational history

3 Variants/Design stages

4 Units Using the B-17

5 Noted B-17 pilots

6 Specifications (B-17G)

6.1 General characteristics
6.2 Performance
6.3 Armament

7 References and external links

8 Related content

Development

The prototype B-17 first flew on July 28 1935 as the Boeing Model 299, with boeing chief test pilot Les Tower at the controls. During a demonstration later that year at Wright Field in Dayton, Ohio, Model 299 competed with the Douglas DB-1 and Martin Model 146. While the Boeing design was obviously superior, Army officials were daunted by the much greater expense per aircraft. October 30th of 1935 the Army Aircorps test pilot Ployer Hill took the Model 229 on a second evaluation flight. Forgetting to take of the control lock, the aircraft took off into a steep climb, nosed over, and crashed. In January of 1936, thirteen YB-17s with a number of significant changes from the Model 229, most notably that of the engines to more powerful Wright R-1820-39 Cyclones, next to 99 B-18s (successor of the DB-1).

The first B-17 went into service in 1938. By December 7 1941, few B-17s were in use by the Army. Following the attack on Pearl Harbor, production was quickly accelerated. The aircraft served in every World War II combat zone. Production ended in May 1945 after 12,726 aircraft had been built.

B-17 Flying Fortresses over Eastern Europe during World War II

Operational history

The name "Flying Fortress" was coined by Dick Williams, a reporter for the Seattle Times who gave this name to the Model 229 when it was rolled out showing off its machine gun installations. Boeing was quick to see the value of the title and had it copyrighted for use. Among the combat aircrews that flew bombers in World War II, noted aviation writer Martin Caidin reported that the B-17 was referred to as the "Queen of the Bombers."

The B-17 was noted for its ability to take battle damage, still reach its target and bring its crew home. It reportedly was much easier to fly than its contemporaries, and its toughness more than compensated for its shorter range and lighter bomb load when compared to the Consolidated B-24 Liberator or the British Avro Lancaster heavy bombers.

The design went through eight major changes over the course of its production, culminating in what some consider the definitive type, the B-17G, differing from its immediate predecessor by the addition of a chin turret with two 0.50 calibre (12.7 mm) machine guns under the nose. This eliminated the aeroplane's main defensive weakness of head on attacks.

Variants/Design stages

Main article: B-17 Flying Fortress variants

The B-17 went through several iterations in each of its design stages and variants. Of the thirteen YB-17s ordered for service testing, only one was actually used. Experiments on this plane led to the use of a turbo-supercharger, which would become standard on the B-17 line. When this aircraft was finished with testing, it was redesignated the B-17A, and was the first plane to enter service under the B-17 designation.

As the production line developed, Boeing engineers continued to improve upon it. To improve performance, the original design was altered to include larger flaps, a larger rudder, and a new nose. The engines were upgraded to more powerful versions several times. Similarly, the gun stations were altered on numerous occasions to enhance their effectiveness.

By the time the B-17G appeared, the number of guns had been increased from seven to thirteen, the designs of the gun stations were finalised, and other adjustments were complete. In this, it incorporated all changes made in its predecessor, the B-17F (which was the first mass-produced version of the B-17). The B-17G is generally considered the defining version of the B-17. Some 8680 were built, and many were converted for other missions, such as cargo-carrying, engine testing, and reconnaissance.

Two versions of the B-17 were flown under different designations. These were the XB-38 and the YB-40. The former was an engine test bed for Allison V-1710 liquid-cooled engines, to test the engine should the Wright engines normally used on the B-17 become unavailable. The YB-40 was a modification of the standard B-17 used before the P-51 Mustang became available. Since no fighters had the range to escort the B-17, a heavily armed modification was used instead with an additional power turret in the radio room, a chin turret (which went on to become standard with the B-17G) and twin .50 caliber (12.7 mm) guns in the waist positions. The ammunition load was over 11,000 rounds making the YB-40 well over 10,000 pounds (4,500 kg) heavier then that of a fully loaded B-17F. Unfortunately, the YB-40s with their numerous heavy modifications had trouble keeping the pace with empty bombers, and the project was abandoned with the arrival of the Mustang and phased out in July of 1943.

Late in World War II, at least 25 B-17s were fitted with radio controls, loaded with 12,000 lb (5443 kg) of high explosives, dubbed 'BQ-7 Aphrodite missiles,' and used against U-boat pens and bomb-resistant fortifications. Because few (if any) BQ-7s hit their target, the Aphrodite project was scrapped in early 1945. (×24)

During and after World War II, a number of weapons were tested and used operationally on B-17's. Some of these weapons included razons (radio guided), glide bombs, and the JB-2 Thunderbugs's, the equivalent of the German V-1 Buzz Bomb.

Units Using the B-17

Main article: List of units using the B-17 Flying Fortress

The B-17 was an ubiquitous aircraft, and it served in dozens of units in theatres of combat throughout World War II. Its main use was in Europe, where its shorter range and smaller bombload relative to other aircraft available did not hamper it as much as in the Pacific Theatre. Only three B-17 groups were stationed in the Pacific, but dozens were stationed in Europe.

It was also used by the Royal Air Force, though mainly roles other than those it had been designed for. The first B-17s - known to the RAF as "Fortress I"s - used by the Royal Air Force had been tragic disasters, and despite its overwhelming success in American hands, the British were reluctant to use the B-17 for its original mission profile of heavy bombing, regarding it as uneconomical due to its larger crew and relatively small bomb load, instead later equipping a number of them with sophisticated radio-countermeasures equipment and using them for some of the first Electronic countermeasures operations with RAF 100 Group.

During World War II, some forty B-17s were repaired by the Luftwaffe after being captured, and put back in the air. Many of these were codenamed as "Dornier Do 200"s and given German markings to disguise their origin, while other B-17s were kept in Allied markings to infiltrate B-17 squadrons and report on their positions.

When Israel achieved statehood in 1948, the IAF (Israeli Air Force) had to be assembled quickly to defend the new nation from the war it found itself embroiled in almost immediately, against the invading armies of Egypt, Jordan and Syria, which were superior in numbers and weapons. The early fleet of the Israeli Air force was a rag tag of hastily acquired Aircraft, many obtained covertly because of international weapon sales ban by the US and other European countries. Among the first aircraft acquired by the Israeli Air Force were 3 US surplus B-17s, smuggled via South America to Czechoslovakia and then Israel. Though generally unsuitable for the ideal needs of the IAF and the nature of this conflict (which did not particularly necessitate long range bombing raids on large area targets), the aircraft were used by 69 Squadron Israeli Air Force . A fouth Aircraft was captured by American officials and confiscated. In their delivery flight from Europe, the aircraft were ordered to bomb the Royal Palace of King Farouk in Cairo, before continuing to Israel. This was a retaliation for Egyptian bombing raids on Tel-Aviv. The Aircraft performed the mission (despite some of the crew fainting alternately due to defective oxygen equipment) but caused only little damage to the target. They were mainly used in the 1948 War of independence; afterwards saw more limited usage until being phased out in 1958.

Noted B-17 pilots

Specifications (B-17G)

General characteristics

Crew: 10
Length: 74 ft 4 in (22.7 m)
Wingspan: 103 ft 10 in (31.6 m)
Height: 19 ft 1 in (5.8 m)
Wing area: 1527 ft² (141.9 m²)
Empty: 54,900 lb (24,900 kg)
Loaded: 72,134 lb (32,720 kg)
Maximum takeoff: 74,000 lb (34,000 kg)
Powerplant: 4× Wright R-1820-97 turbo-supercharged radials, 1,200 hp (895 kW)

Performance

Maximum speed: 300 mph (480 km/h)
Range: 3,400 miles (5,500 km)
Service ceiling: 35,600 ft (10,900 m)
Rate of climb: ft/min ( m/min)
Wing loading: 47.2 lb/ft² (231 kg/m²)
Power/mass: 0.0655 hp/lb (110 W/kg)

Armament

13× Browning M-2 0.50 calibre (12.7 mm) machine guns
8,000 lb (3,600 kg) of bombs

References and external links

Hess, William N. Big Bombers of WWII. Lowe & B. Hould, 1998. (ISBN 0681075708)
Jablonski, Edward. Flying Fortress. Doubleday, 1965. (ISBN 0385038550)
Johnson, Frederick A. Boeing B-17 Flying Fortress (Warbird Tech Series, Volume 7). Minnesota: Voyageur Press, 2001. (ISBN 1580070523)
Lloyd Alwyn T. B-17 Flying Fortress in detail and scale. AERO Books, 1986. (ISBN 0816850291)
O'Leary, Michael. Boeing B-17 Flying Fortress (Osprey Production Line to Frontline 2). United Kingdom: Osprey Publishing, 1999. (ISBN 1855328143)
Wagner, Ray. American Combat Planes. Doubleday, 1982. (ISBN 0930083172)
BQ-7 history
Encyclopedia of American Aircraft
USAF Museum