Class A airfield
Encyclopedia
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
in the Second World War. Several were transferred to the U.S. Eighth Air Force
Eighth Air Force
The Eighth Air Force is a numbered air force of the United States Air Force Global Strike Command . It is headquartered at Barksdale Air Force Base, Louisiana....
for use as heavy bomber
Heavy bomber
A heavy bomber is a bomber aircraft of the largest size and load carrying capacity, and usually the longest range.In New START, the term "heavy bomber" is used for two types of bombers:*one with a range greater than 8,000 kilometers...
bases.
Class A layouts were constructed to specifications set by the British Air Ministry
Air Ministry
The Air Ministry was a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964...
in August 1942, the main feature of which was a set of converging strips, each containing a concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...
for takeoffs and landings, optimally placed at 60 degree angles to each other in a triangular
Triangle
A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....
pattern. The longest strip was designated the main strip and aligned southwest to northeast wherever possible, this being chosen to allow aircraft to takeoff and land into the prevailing wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
s. The other two runways were to allow use when the winds were blowing from other directions. The primary consideration was for operational safety for any type of aircraft then in operation or under development, including the U.S. B-29 Superfortress
B-29 Superfortress
The B-29 Superfortress is a four-engine propeller-driven heavy bomber designed by Boeing that was flown primarily by the United States Air Forces in late-World War II and through the Korean War. The B-29 was one of the largest aircraft to see service during World War II...
.
The strips were 600 feet (183 m) in width, cleared, graded and surfaced with turf
Sod
Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of thin material.The term sod may be used to mean turf grown and cut specifically for the establishment of lawns...
. A concrete runway 150 feet (46 m) in width was centered on the strip, with a minimum length of 6,000 feet (1,830 m) for the main strip and 4,200 feet (1,280 m) for the secondary strips. On each side of the strip the field was cleared of obstructions and leveled an additional 300 feet (90 m). Gradient
Gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....
s for the strips were a maximum 1 in 80 longitudinally and 1 in 60 transversely. In addition, an area at the end of each runway was cleared of obstructions at an angle of fifteen degrees outward from each side on a rising imaginary plane of 1 in 50 to provide a flightway called a funnel.
The material needs for building runways suitable for heavy bombers were approximately 18,000 tons of dry cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
and 90,000 tons of aggregate
Construction Aggregate
Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world...
. Expected stress factors of 2,000 pounds per square inch led to runway thicknesses of six to nine inches of concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
slab laid on a hardcore base, covered with a layer of asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
. In areas where there was no natural rock, such as East Anglia
East Anglia
East Anglia is a traditional name for a region of eastern England, named after an ancient Anglo-Saxon kingdom, the Kingdom of the East Angles. The Angles took their name from their homeland Angeln, in northern Germany. East Anglia initially consisted of Norfolk and Suffolk, but upon the marriage of...
, stone had to be imported for the hardcore.
Taxiway
A taxiway is a path on an airport connecting runways with ramps, hangars, terminals and other facilities. They mostly have hard surface such as asphalt or concrete, although smaller airports sometimes use gravel or grass....
s called a perimeter track, of a standard width of 50 feet (15m). A 30-foot (9m) area was cleared and leveled on either side of the perimeter track. Class A specifications for taxiways set a minimum curve radius
Radius of curvature (mathematics)
In geometry, the radius of curvature, R, of a curve at a point is a measure of the radius of the circular arc which best approximates the curve at that point. If this value taken to be positive when the curve turns anticlockwise and negative when the curve turns clockwise...
of 150 feet measured from the center line for angles greater than 60 degrees and 200 feet (61m) for angles less than 60 degrees. Perimeter track gradients could not exceed 1 in 40 in any direction, and no building could be placed closer than 150 feet from the edge of the track.
Dispersals called hardstands were placed along the perimeter track, made of concrete, with their centers at least 150 feet from the edge of the track and the edges of each hardstand separated from each other and from the funnels by a minimum of 150 feet. The purpose of the hardstands was to allow the parking
Parking
Parking is the act of stopping a vehicle and leaving it unoccupied for more than a brief time. Parking on one or both sides of a road is commonly permitted, though often with restrictions...
of aircraft some distance from each other so that an air attack
Strategic bombing
Strategic bombing is a military strategy used in a total war with the goal of defeating an enemy nation-state by destroying its economic ability and public will to wage war rather than destroying its land or naval forces...
on the airfield would be less likely to destroy all the aircraft at once. Dispersal also minimised the chance of collateral damage
Collateral damage
Collateral damage is damage to people or property that is unintended or incidental to the intended outcome. The phrase is prevalently used as an euphemism for civilian casualties of a military action.-Etymology:...
to other aircraft should an accident occur whilst bombing-up.
Nine bases (Alconbury
RAF Alconbury
RAF Alconbury is an active Royal Air Force station in Cambridgeshire, England. The airfield is adjacent to the Stukeleys [Great and Little] and located about northwest of Huntingdon; about north of London....
, Bassingbourn
RAF Bassingbourn
RAF Bassingbourn is a former military airbase located in Cambridgeshire approximately north of Royston, Hertfordshire and south west of Cambridge. During World War II it served first as an RAF station and then as a bomber base of the U.S. Eighth Air Force...
, Chelveston
RAF Chelveston
RAF Station Chelveston was a military airfield located on the south side of the A45, 5 miles east of Wellingborough, near the village of Chelveston in Northamptonshire, United Kingdom....
, Grafton Underwood
RAF Grafton Underwood
RAF Grafton Underwood is a former World War II airfield in England. The field is located 4 miles NE of Kettering in Northamptonshire.-RAF use:...
, Kimbolton
RAF Kimbolton
RAF Kimbolton is a former World War II airfield in England, located 8 miles west of Huntingdon in Cambridgeshire.-USAAF use:The airfield was originally built in 1941 for RAF Bomber Command, then expanded to Class A airfield standards for use by American heavy bombers during 1942. Kimbolton was...
, Molesworth
RAF Molesworth
RAF Molesworth is a Royal Air Force station located near Molesworth, Cambridgeshire, United Kingdom with a history dating back to 1917.Its runway and flight line facilities were closed in 1973 and demolished to support ground-launched cruise missile operations in the early 1980s...
, Podington
RAF Podington
RAF Podington is a former World War II United States Army Air Force base in England. It is located six miles south-east of Wellingborough, in Bedfordshire.-Overview:...
, Polebrook
RAF Polebrook
RAF Polebrook is a former World War II airfield located 3.5 miles east-south-east of Oundle, at Polebrook, Northamptonshire, UK. The airfield was built on Rothschild estate land starting in August 1940....
, and Thurleigh
RAF Thurleigh
RAF Thurleigh was a Royal Air Force station located five miles north of Bedford, England. Thurleigh was transferred to the U.S. Eighth Air Force on 9 December 1942, designated Station 111, and used for heavy bomber operations against Nazi Germany.-Origins:...
) were allotted to the Eighth Air Force but had been completed prior to the Class A standard for runway lengths. These were brought to Class A standards in 1942 and early 1943 by extending their runways, repositioning their perimeter tracks, and adding additional hardstands.
Class A airfields were also characterized by standardized technical site requirements for repair, maintenance and storage of aircraft. Two T2 type metal hangar
Hangar
A hangar is a closed structure to hold aircraft or spacecraft in protective storage. Most hangars are built of metal, but other materials such as wood and concrete are also sometimes used...
s (240 feet long by 115 feet wide by 29 feet high) were the standard for most bases, although a few pre-1942 bases had three T2 hangars and Thurleigh had four. Three bases (Chelveston, Molesworth, and Polebrook) also had a J Type brick-and-metal hangar (300' X 151') in addition to a pair of T2's, and Bassingbourn, which had been a pre-war RAF bomber station, had four C type brick hangars measuring 300 by 152 feet.
With the end of World War II and the resurgence of the sport of motor racing several former airfields were used as race tracks, e.g., Silverstone
Silverstone Circuit
Silverstone Circuit is an English motor racing circuit next to the Northamptonshire villages of Silverstone and Whittlebury. The circuit straddles the Northamptonshire and Buckinghamshire border, with the current main circuit entry on the Buckinghamshire side...
, Castle Combe
Castle Combe Circuit
Castle Combe Circuit is a motor racing circuit in Wiltshire, England, approximately from Bristol. The circuit used to be the perimeter track of a World War II airfield, and opened to racing in 1950.- History :...
, Goodwood Circuit
Goodwood Circuit
Goodwood Circuit is an historic venue for both two- and four-wheeled motorsport in the United Kingdom. The 2.4 mile circuit is situated near Chichester, West Sussex, close to the south coast of England, on the estate of Goodwood House, and completely encircles Chichester/Goodwood Airport...
, the races generally being run on the encircling perimeter track, one exception to this being the drag racing
Drag racing
Drag racing is a competition in which specially prepared automobiles or motorcycles compete two at a time to be the first to cross a set finish line, from a standing start, in a straight line, over a measured distance, most commonly a ¼-mile straight track....
strip at Santa Pod Raceway
Santa Pod Raceway
Santa Pod Raceway, in Northamptonshire, England, opened at Easter in 1966, is Europe's first permanent drag racing venue. It was built on a disused World War II American air base, RAF Podington, once used by the 92nd Bomber Group. It is now the home of European drag racing and has grown...
, where the contestants use the runway of the former RAF Podington
RAF Podington
RAF Podington is a former World War II United States Army Air Force base in England. It is located six miles south-east of Wellingborough, in Bedfordshire.-Overview:...
as a track.