The need for airborne liaison with army commanders on the battlefield was first recognized during the American Civil War, long before the first flight of the Wright Brothers in 1903. Both the Confederacy and the Union used balloons to observe enemy movements. On September 24th, 1861, Professor Thaddeus Lowe made history when he used a telegraph to direct the fire of Union artillery against enemy positions beyond their field of vision. They struck their targets, which demonstrated the importance of airborne artillery direction beyond any question of doubt. The picture below shows Lowe's balloon Intrepid being filled with gas. (Click the picture for a larger view.)
Unfortunately, balloons proved somewhat capricious in operation. They needed a supply of gas, were unusable in high winds and bad weather, and if they broke free from their moorings they could be carried across enemy lines and captured (as happened to a Confederate balloon in the summer of 1863). Nevertheless, they had proven their usefulness. Interestingly, this led to the first Naval "aircraft-carrier" when Lowe supervised the modification of a coal barge into the grandly-named George Washington Parke Custis. Lowe used it on 11th November 1861 to take General Daniel E. Sickles aloft to observe Confederate positions, and later it towed one of his balloons for over 13 miles while he made continuous observations.
The interest of European armies was attracted by these experiments, and the Prussian Army sent Count Ferdinand von Zeppelin to observe Professor Lowe's balloons in operation. His reports led the Prussian (and later the German) Army to develop their own observation balloons, and other European armies followed suit. By World War I they were a widely-used instrument of war for observation and artillery direction. The picture below shows a US Major in the basket of an observation balloon near the front line in 1918.
"Balloon busting" became an important mission of early aircraft, firing incendiary ammunition to set ablaze the inflammable gas filling the balloons. In response both sides installed early anti-aircraft artillery and machine-guns around their balloon positions, making such attacks extremely hazardous for the aircraft concerned. Oddly enough, balloon observers were equipped with parachutes to escape such attacks long before aircraft pilots received the same life-saving equipment.
The limitations of balloons became even more apparent now that aircraft could move under their own power, and efforts were made to supplement (and eventually replace) them with planes. During World War I numerous aircraft served in an army liaison role, carrying a pilot and observer. They could monitor enemy movements and report them to military commanders on the ground, initially by dropping written messages in tubes with ribbons attached to make them easier to track and find, and later by using radios and Morse code.
During the inter-war years more specialized aircraft were developed for the army liaison and close reconnaissance role. However, given budgetary restrictions on aircraft purchases, relatively small numbers were involved and they usually had a low priority compared to fighters and bombers. It would take World War II to see an explosion in the use of such aircraft and the further development of their roles to include casualty evacuation, the relaying of orders and ferrying of supplies to front-line troops, and the transportation of officers from their units to and from headquarters.
World War II liaison aircraft were often based on civil aviation designs adapted for the purpose (and sometimes commandeered from their civilian owners for military use). For simplicity's sake I'll describe them in alphabetical order of their countries of origin. Only the main combatants will be covered.
The Westland Lysander was one of the best liaison aircraft of World War II, despite its oddly antiquated appearance. It first flew in 1936 and served with the Royal Air Force (RAF) throughout the war. It had high gull wings (it's interesting to compare them to the inverted gull wings of the later American Corsair fighter) which were fitted with automatic slats and slotted flaps to give it a relatively low stalling speed and short take-off and landing ability. It was powered by a Bristol Mercury radial engine and used a fixed undercarriage inside streamlined "spats" to reduce aerodynamic drag. A .303-inch machine-gun was fitted into each "spat", and two more were provided at the back of the cabin for use by an observer to defend the rear. It could carry a cargo "pod" or additional fuel tank beneath the fuselage, and a light bomb load if necessary.
Lysanders fought in the Battle of France, proving to be easy prey for German fighters. (This was an early lesson in the use of army liaison aircraft: they could only be safely deployed under conditions of air superiority, otherwise losses would be heavy.) After the fall of France they were used in almost all theaters of war by British allies, including some by the US Army Air Force (USAAF). Prior to the invasion of France in 1944 the Lysander gained fame as the principal aircraft used to insert and extract agents and resistance fighters between Britain and the Continent. Its ability to fly low and slow and land in very restricted spaces proved invaluable for this purpose. It was even used for air-sea rescue to drop dinghy and supply containers to pilots in the water.
Almost 1,800 Lysanders were built, and it served throughout the war. Its last operational service was with the Egyptian Air Force against Israel in the 1948 Arab-Israeli War.
Another British liaison aircraft was the Taylorcraft Auster. Based on a design by the American Taylorcraft company, the Model B, it went through several production versions using different engines and cabin layouts. Over 1,600 were built, and it was the most-used British army co-operation aircraft during the European battles of 1944-45. It was also deployed to the China-Burma-India theater of operations.
It continued in production for some years after the war, and many examples are today in civilian hands. One is shown in the short video clip below.
The French Air Force operated the ANF Les Mureaux 113 observation aircraft during the Battle of France. Equipped with a high parasol wing, it was comparable to similar aircraft of other nations. Some were converted into night fighters, but proved unsuccessful in this role. About 285 were built, but most were destroyed during the Battle of France.
In the early 1930's Germany fielded the Heinkel He 46 army co-operation aircraft. About 500 were built, and it saw operational service in Spain with the Condor Legion and in Poland during the invasion of 1939. It was then withdrawn for training use, but returned to operational service in 1942-43 as a night bomber to respond to the "Night Witches" of the Soviet Union. (The latter were described in Weekend Wings #4.)
The Henschel Hs 126 was a contemporary of the He 46, entering service in 1938 after prototypes were evaluated by the Condor Legion in Spain. It looked somewhat similar to the British Lysander with a high parasol wing and fixed undercarriage enclosed in "spats". It saw service during most of World War II. Ironically, Germany supplied some of them to Greece, which in turn used them against Italian and German invaders during 1941!
The most successful front-line communications and army co-operation aircraft in the Luftwaffe was the Fieseler Fi 156, known as the Storch or Stork. It had a high wing fitted with leading-edge slats and a huge trailing flap, giving it outstanding short take-off and landing characteristics and the ability to fly at very low speeds. It was probably the best-performing aircraft of World War II in this respect.
Almost 3,000 were built, and the Storch served on every front. At least 60 were captured by the Allies, who admired its low-speed performance. Indeed, a captured Storch was selected by British Field Marshal Montgomery for use as his personal aircraft! The Storch is perhaps most famous for its role in Unternehmen Eiche or Operation Oak, the commando raid led by Otto Skorzeny on the Campo Imperatore Hotel in the Gran Sasso region of Italy's Apennine Mountains to rescue the imprisoned Fascist dictator of Italy, Benito Mussolini, in September 1943. A Storch landed in less than 100 feet, collected Mussolini and Skorzeny and took off again to fly them to safety. Film of the rescue is included in the clip below.
The Germans also fielded two unique army reconnaissance aircraft, having no direct equivalents in Allied air fleets. The Blohm & Voss BV 141, which first flew in 1938, was an odd-looking aircraft with its crew module separate from its engine and main fuselage.
This asymmetrical design actually flew very well, its designer, Dr. Richard Vogt, having calculated correctly that the offset weight of the crew cabin would be counterbalanced by the torque of the engine. However, due to difficulties obtaining engines and other production problems, only 38 were built.
The Focke-Wulf Fw 189, known as the Uhu or Owl, was far more widely used, with almost 850 being produced. It was a twin-engined design which first flew in 1938 and entered operational service in 1941.
The Uhu was mostly produced at an aircraft factory in occupied France, and used French engines, which is why it was manufactured in far greater numbers than the BV 141 (which relied on German engines, harder to obtain in competition with other German aircraft). It was mostly used on the Eastern Front against the Soviet Union. The Uhu is widely regarded as the best army co-operation and close-support reconnaissance aircraft of World War II, and proved able to absorb a great deal of damage (sometimes including the loss of one of its two tail booms) and still return safely to base. It was very agile and easy to handle, making a difficult target for enemy fighters.
The video clip below is from a German war newsreel, showing an Fw 189 dropping instructions to an artillery battery in the Stalingrad region.
Finally, although not designed for this purpose, the Luftwaffe used the Messerschmitt Bf 108 Taifun or Typhoon for army communication and liaison duties (and many other functions). The Taifun was a low-wing monoplane similar in some respects to the Bf 109 fighter. It could carry up to four people. Production was transferred to occupied France in 1942, and after the war its manufacture was continued there as the Nord Pingouin.
The Kokusai Ki-76 was inspired by and had similar flying characteristics to the German Fi 156 Storch. The Allies gave it the reporting name of "Stella".
It was introduced in 1942 and saw action in the China-Burma-India theater and in the Philippines. Some also flew from aircraft-carriers of the Imperial Japanese Navy.
The Soviet Union did not develop a purpose-designed army co-operation and liaison aircraft during World War II. The Polikarpov Po-2 biplane was used in very large numbers for this purpose, as well as for training, night bombing and other tasks. This aircraft was described in some detail in Weekend Wings #4, so I won't go into detail about it here.
In addition to the Po-2, large numbers of army co-operation aircraft were supplied to the Soviet Union by Britain and the United States.
The USA fielded numerous army co-operation and liaison aircraft during World War II. I'll list them in alphabetical order by manufacturer. A confusing feature is that many different aircraft models from different manufacturers were all referred to by the common name of "Grasshopper" in military service, so I'll avoid this name and refer to them by their official designations.
The Aeronca L-3 was a high-wing monoplane adapted from pre-war civilian designs. It was obsolete by the time the USA entered the war, and served mostly in the continental US to train observation and liaison pilots who would fly more modern aircraft in combat zones.
The Beech UC-43 Traveler was a military designation for the Beechcraft Staggerwing biplane. Several hundred were purchased or pressed into service from civilian owners to serve as light personnel transports and liaison aircraft. Most were used in the Continental USA.
The Douglas O-46 was introduced in 1937, with about 90 purchased for the USAAF and the Philippine Army Air Corps. It proved too large, slow and heavy for observation duties, and was consequently relabeled as the L-46 (L standing for "liaison"). Several were destroyed in the Japanese attack on the Philippines in 1941, and the remainder were declared obsolete the following year. They were subsequently used for training and utility duties.
The Interstate L-6 was a relatively unsuccessful light observation and liaison aircraft. It was plagued by engine overheating problems that were never fully solved, and as a result was used only in the USA and not sent to combat zones overseas.
The Piper L-4 was perhaps the most famous US army co-operation aircraft, and certainly the most widely used.
Based on the pre-war Piper J-3 Cub design, almost 6,000 were purchased for military service. They flew in all operational theaters and were used for artillery fire control, courier duties and front-line liaison. In the continental US they were used to train glider pilots. The L-4's short landing capability is demonstrated in the video clip below.
The Stinson L-5 Sentinel was the second most widely used army co-operation aircraft in the USAAF, with almost 3,600 being produced. It performed liaison, artillery spotting and air ambulance duties in many theaters of the war.
The Stinson Model 74, also known as the Vultee L-1 Vigilant, was initially designated the O-49 by the USAAF and later redesignated the L-1. In RAF service it was dubbed the Vigilant. It used a large radial engine, and was more comparable to the British Lysander than to other American army co-operation aircraft. Some 324 were built. An ambulance version is shown below.
The Taylorcraft L-2 was another light high-wing monoplane observation and liaison aircraft. It was originally designated the O-57. Several hundred were built for the USAAF or impressed into service from civilian owners. The example shown below hangs in the USAF Museum.
In all more than 10,000 aircraft served the USAAF in the army co-operation role. They did anything and everything one could think of, including artillery spotting, liaison and communications duties, rescue, transporting supplies, special espionage missions behind enemy lines, and even dropping light bombs.
After World War II all air forces and armies continued to use liaison aircraft. They saw service in Korea, and to a lesser extent in Vietnam, but increasingly their role was taken over by the ever more ubiquitous helicopter. Today there are very few of this type of aircraft still in service. A helicopter can get into much tighter spots and do all that is necessary without requiring a landing strip, making it a much more suitable option: and artillery spotting and reconnaissance of enemy positions, hazardous tasks in the presence of enemy anti-aircraft fire, are increasingly being conducted by unmanned aerial vehicles.
Many of the older liaison aircraft are still flying in civilian hands, and along with military surplus training aircraft they formed the basis for the explosion in private civil aviation after World War II. Some, such as the Piper Cub, are even available in new-production kit form! They have attracted ongoing interest among the flying public, and some organizations such as the Alamo Liaison Squadron specialize in putting on flying displays with several of these aircraft. The ALS has published a book, "Box Seat Over Hell", that vividly describes the World War II experiences of US army liaison pilots. To close this edition of Weekend Wings, here's an excerpt:
Grasshopper pilots not only handled some of the most difficult missions of the war, they also handled some of the most treacherous and hair raising. They flew in every theatre: from the desert when, in the super heated air, it was a real struggle to get airborne; in the arctic, where they fought to stay on course though williwaws and boreal storms, and where if they got lost they were almost guaranteed a frigid death. They flew over jungles with aircraft so overloaded they barely maintained altitude, with engines screaming, to clear the tree tops. These pilots were not the "glory boys" of the Air Corps. They were never given the recognition or the medals of the bomber pilots . . . In the process, they succeeded in turning their flimsy crates into one of the most useful tools of the air war.