Advanced landing ground


Advanced landing grounds were temporary advance airfields constructed by the Allies during World War II during the liberation of Europe. They were built in the UK prior to the invasion and thereafter in northwest Europe from 6 June 1944 to V-E Day, 7 May 1945.
Unlike the permanent airfields built in the United Kingdom and designed for the strategic bombardment of Germany, the tactical combat airfields on the continent were temporary, often improvised airfields to be used by the tactical air forces to support the advancing ground armies engaged on the battlefield. Once the front line moved out of range for the aircraft, the groups and squadrons moved up to newly built ALGs closer to the ground forces and left the ones in the rear for other support uses, or simply abandoned them.

Overview

When the Allies invaded Normandy on D-Day, Royal Air Force Airfield Construction Service engineers were among those in the initial assault waves. Their mission was to rapidly construct forward operating airfields, known as advanced landing grounds , on the European continent. As the Allied armies advanced across France and into Nazi Germany, several hundred airfields were built or rehabilitated for use by the allied air forces.
For security reasons, the airstrips were referred to by a coded number instead of location. In the United Kingdom, USAAF installations were identified by three digit numbers ranging from AAF-101 to AAF-925. After D-Day, continental airfields in the European Theater of Operations were also assigned coded numbers. American airfields were given A-, Y-, or R-, prefixes and numbered consecutively from 1 to 99. Both "A" and "Y" designated airfields could be found in France, however many "Y" fields would also be in the Netherlands, Belgium and occupied areas of Germany. "R" coded fields were usually located in occupied Germany. British airfields on the continent were also consecutively numbered, but with a B-prefix.
The numbering system for airfields was sequentially assigned as airfields were allocated, not by location or by date of operational use. A-1, Saint Pierre du Mont, was declared operational on 13 June 1944; A-3 Cardonville on 14 June. However A-2, Cricqueville-en-Bessin, was declared operational a few days later on 19 June.
Also many of these airfields had no combat air group or squadron attached to them. They were designed for casualty evacuation and supply transport and consisted of a quickly built runway manned only by a small complement of station personnel with little or no infrastructure other than tents. As the ground forces moved east, wounded would be sent to the airfield to be picked up by C-47s and taken to hospitals in England or other rear areas. Also supplies would be airlifted to the fields and unloaded, to be quickly transported to the front line units. These were normally known as S&E Fields.
Once completed, airfields were usually utilised by the combat groups or squadrons within a day or so of being declared operational for military use by the IX Engineering command engineers. They would be used for perhaps a few days to a week, to several months, depending on the location, use, and operational requirements. Once the combat units moved up to the next assigned ALG, they could be utilised as S&E Fields, or deconstructed quickly and abandoned, with the land being released back to the landowners or civil authorities in the area.

Construction

The mission for constructing ALGs was placed in the hands of the Airfield Construction Service of the RAF Second Tactical Air Force, whilst the USAAF's Ninth Air Force and its specially created engineering arm, the IX Engineer Command, were responsible for ALG's in the US sector of operations. Each aviation engineer battalion in the command was composed of sufficient men and equipment to quickly construct an airfield or landing ground for a single tactical fighter or bomb group unit.
ALGs were selected in two ways. First, existing enemy military or civilian airfields which were captured as the ground forces advanced were noted by engineers assigned to ground units. Second, engineers noted areas in grid locations where an airfield was desired, that had flat terrain, good land drainage, and where an airfield could be constructed quickly.
Captured airfields could be restored for use as advanced landing field in one to three days depending upon the amount of damage and the number of mines and booby traps encountered.
Dry-weather advanced landing fields were constructed by a single battalion at a favourable site in flat terrain in one to three days, including time for reconnaissance. At less favourable sites, where more clearing and grading were required, or all-weather fields which also needed additional infrastructure, the time varied from three to ten days.
ALGs were equipped with an access road that was connected to the existing road infrastructure; a dump for supplies, ammunition, and gasoline drums, along with a drinkable water and a minimal electrical grid for communications and station lighting. Tents were used for billeting and also for support facilities. Time was the all-important factor and ALGs serve its purpose if available for only a few days. As the forward area became the rear area, an advanced landing field could be improved for medium bomber use, but initially they primarily served fighter and transport groups.
Based on the experience obtained in the North African and Italian campaigns, fighter groups required an airfield 120 feet x 3600 feet long, and fighter-bomber groups required fields 120 feet x 5000 feet long. Medium bomb groups required 120 feet x 6000 feet runways.

Runway types

Instead of using rough, unimproved dirt strips, engineers used surfacing material necessary to strengthen the soil to support the weight of the aircraft and as a measure of insurance against the wet weather. Airfields were initially single runway landing strips which were laid down east–west unless local conditions dictated a different runway direction.
ALGs laid in the UK were of Sommerfeld Tracking, a form of stiffened steel wire mesh.
  • Square-mesh track
The surfacing material selected for the building of advanced landing grounds during the first weeks after the Normandy invasion was known as square-mesh track. SMT, a British development, was material composed of heavy wire joined in three-inch squares. It was chosen over other surfacing materials because it was very lightweight, allowing sufficient quantities to be transported across the English channel on over-tasked landing craft. Easily workable, a SMT landing mat for fighters could be laid like a carpet in about one week.
  • Prefabricated Hessian
After the initial batch of airfields was completed using SMT, the Army aviation engineers switched almost exclusively to another surfacing material known as prefabricated hessian surfacing. Light and easily transportable, PBS did not create the dust problem encountered with SMT fields. Made of an asphalt-impregnated jute delivered in rolls 300 feet in length and 36 inches or 43 inches in width, PBS was laid in overlapping layers to produce a dust-free fair weather surface. It was also common to build airstrips using both SMT and PBS, laying SMT on top.
  • Pierced steel plank
To provide an all season durable airfield for the RAF's 2TAF and the USAF Ninth Air Force's medium and light bombers, a third type of surfacing material known as pierced steel plank, or Marston Matting was introduced on the Normandy bridgehead in July 1944. It consisted of, steel planks joined together and laid perpendicular to the line of flight. Long used in other theatres, PSP would have been ideal for all airfields on the continent, but its limited availability and greater weight made this impractical. Moreover, because of supply problems, construction of even a PSP fighter-bomber field could take a month or longer, while similar PBS and SMT fields could be constructed in two weeks and one week, respectively.
In addition, sod and earth runways were built for emergency landing strips and refuelling and rearming strips. Captured airfields contained a wide variety of runways, most commonly asphalt; concrete; macadam or tar-penetrated macadam.

Airfield types

There were five main types of airfields built by the USAAF combat engineers on the continent. These were:
  • Emergency Landing Strip
Consisted of a rough, graded runway approximately 2000 feet long to provide a place for emergency belly-landings of damaged aircraft.
  • Supply and Evacuation
Usually a rough graded runway near the front line or an airfield in the rear that was used by C-47s for transport of casualties to the rear, or delivery of supplies and munitions to the front line.
  • Refueling and Rearming Strip
Consisted of a runway and an aircraft marshalling area on each end of the runway. It was designed to provide an airfield near the front lines upon which aircraft based in rear areas could land, be refuelled and rearmed, and take off again on a mission without having to return to their home field in the rear. Also could be used for dispersal or for when services other than refuelling or rearming was required. These airfields could be expanded into advance landing grounds by the addition of dispersal and other station facilities. Generally if an R&R strip was built, it would be sited wherever possible with a view to further expand it later into an ALG.
  • Advanced landing grounds
An advanced landing ground could be constructed as such from the beginning or by development from an R&R Strip by the addition of dispersal facilities, expansion of the road network and other additions to the station and technical area in order for it to be used over an extended period of time.
  • Tactical air depots
A number of ALGs were expanded into tactical air depots by the addition of hangars, shops, more dispersal hardstands, roads, and other facilities. Some were developed from the beginning.