Advanced landing ground: Difference between revisions

Advanced Landing Ground (ALG) was the term given to the temporary airfields constructed by the Allies on continental Europe between D-Day, 6 June 1944 and V-E Day, 7 May 1945.

When the Allies invaded Normandy on D-Day, United States Army Air Forces (USAAF) engineers were among those in the initial assault waves. Their mission was to rapidly construct forward operating airfields, known as Advanced Landing Grounds (ALGs), on the continent. As the Allied armies advanced across France and into Germany, several hundred airfields were built or rehabilitated for use by the allied air forces.

Unlike the permanent airfields built in the United Kingdom and designed for the strategic bombardment of Germany, 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.

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 (AAF) numbers ranging from AAF-101 to AAF-925. After D-Day, continental airfields in the European Theater of Operations (ETO) 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 France, as well as 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, Criqueville, was declared operational 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 compliment 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 (Supply and Evacuation).

The mission for construing ALGs was placed in the hands of USAAF's Ninth Air Force and its specially created engineering arm, the IX Engineer Command. Each aviation engineer battalion in the command (of a total of sixteen) 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 equipped with an access road was built to the existing road infrastructure; a dump for supplies, ammunition, and gasoline drums, along with a drinkable water and 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 becomes the rear area, an advanced landing field could be improved for medium bombers but initially it served primarily fighter and transport groups.

Dry-weather advanced landing fields were constructed by a single battalion at a favorable site in flat terrain in from 1 to 3 days, including time for reconnaissance. At less favorable sites, where more clearing and grading were required, the time varied from 3 to 10 days.

Captured enemy airfields could be restored for use as advanced landing field in 1 to 3 days depending upon the amount of drainage and the number of mines and booby traps encountered.

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. 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.

• Square-Mesh Track (SMP)

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). 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 overtasked landing craft. Easily workable, a SMT landing mat for fighters could be layed like a carpet in about one week.

• Prefabricated Hessian (SMP)

After the initial batch of airfields was completed using SMP, the Army aviation engineers switched almost exclusively to another surfacing material known as prefabricated hessian (burlap) surfacing (PBS or PBS). 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 layed in overlapping layers to produce a dust-free fair weather surface.6 It was also common to build airstrips using both SMT and PBS, laying SMT on top.

• Pierced Steel Plank (PSP)

To provide an all season durable airfield for the Ninth Air Force's medium and light bombers, a third type of surfacing material known as pierced steel plank (PSP), was introduced on the Normandy bridgehead in July 1944. It consisted of 10 feet long, 15 inch wide steel planks joined together and layed perpendicular to the line of flight. Long used in other theaters, 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.

Once completed, airfields were usually utilized by the combat groups or squadrons within a day or so of being declared operational for military use by the IX Engineering command engineers.

An unforeseen development was the extraordinary demand for transport, supply, and evacuation fields as the Allied armies pushed past Paris toward the German frontier. In late 1944, supplies could not keep pace with General Eisenhower's forces, and to help lessen the supply shortage airfields for C-47 Skytrain cargo planes became a priority. Bringing in ammunition of all types and especially gasoline on the trip to the ALGs on the continent, the C-47's on the return trip evacuated wounded to the rear.

By 15 September 1944, IX Engineer Command had placed over eighty ALG airfields in operation, while British engineers had constructed seventy-six airfields in their zone. In Southern France, another twenty or so fields had been built by American engineers from Twelfth Air Force from the Mediterranean Theater of Operations (MTO). In October these uncoded airfields were assigned to the ETO and given ALG code numbers.

The stabilization of the front lines in Holland, Belgium, and eastern France in mid-September 1944, which would last into the new year, allowed aviation engineers a chance to reorganize and prepare for the upcoming winter season. As expected, they could not build new PHS and SMI airstrips during the fall rain and winter snow seasons because of the moist ground. Besides concrete, the American-made PSP was the only available surfacing material that could be laid down during this inclement weather in Europe.

To keep the supply lines open, selected airfields in Belgium and France were therefore "winterized" with PSP. Because of the limited supply of PSP, however, only a limited number of airfields could be winterized, making it necessary to base two group sized units per airfield. But sufficient fighter-bomber and tedium bomber airfields were completed that winter to ensure Ninth Air Force aircraft could continue flying combat missions.

The major problem affecting airfield construction in early 1945 was not the surprise German Ardennes counteroffensive (which caused the Abandonment on only one airfield - Y-39, Hagenau). Rather, an early February thaw threatened to make airfields inoperable due to the mud and water. Using local civilian labor, engineers performed extensive maintenance on the threatened airfields and successfully resolved the crisis

The renewed allied offensive in early 1945, following the Battle of the Bulge, was supported in earnest by the building of tactical airfields in occupied Germany. Trier (Y-57), became the first operational tactical American airfield on German soil on 10 March 1945. When a crossing over the Rhine River was spearheaded at Remagen, Germany, a supply and evacuation strip was quickly set up to support the bridgehead. As Allied tank columns struck out rapidly into the heartland of Germany, the airfield "clutches" of the Ninth Air Force's tactical air commands moved east of the Rhine river within range of virtually any target in Germany.

Scores of Luftwaffe sod and hard surfaced airfields were captured in the lightning advance, virtually undamaged, lessening the requirement for SMT, PHS, and PSP prefabricated surfacing. The relative lack of German military opposition in late March, April and May of 1945 lessened the need for close air support and produced a greater demand for supply airstrips to keep the offensive moving. Every opportunity was used to clear captured German airfields for use along the armies' route, allowing C-47's and other transports to land with food, gas, and ammunition. The supply effort received top airfield priority. By V-E Day, 9 May 1945, 76 of the 126 airfields made operational east of the Rhine river were strictly supply and evacuation fields.

USAAF Engineers constructed or rehabilitated over 280 continental airfields in the ETO from D-Day to V-E Day. In the summer months that followed, a few new airfields were constructed, but dozens more were abandoned.

The airfield coding system remained in effect until after the Japanese surrender in the Pacific, when, on 14 September 1945, the system was officially discontinued. Thereafter, airfields were referenced by their geographic name.

 This article incorporates public domain material from the Air Force Historical Research Agency

• Maurer, Maurer. Air Force Combat Units of World War II. Maxwell AFB, Alabama: Office of Air Force History, 1983. ISBN 0-89201-092-4.
• Johnson, David C. (1988), U.S. Army Air Forces Continental Airfields (ETO), D-Day to V-E Day; Research Division, USAF Historical Research Center, Maxwell AFB, Alabama.
• IX Engineering Command ETO Airfields layout

• Normandy ALGs