Airpower Orphans, Part II: Whatever Happened to Liaison Aircraft?


The airplane was remarkably pretty. Sporting a steel frame, the O-49 was a high-wing, fabric-covered monoplane built for the Army Air Corps in 1940. Silvery sheet metal enclosed the engine, in front of a two-place cockpit. The skeletons of the control surfaces and tail were stainless steel, immune to corrosion. It could land in its own length, or clear a 50-foot obstacle a mere 500 feet after starting a takeoff roll. Drawn from the Stinson Model 74, which engineers designed as a business airplane, the O-49 was a new type of aircraft — the liaison aircraft. Also called an “Army cooperation” aircraft, designers intended the liaison aircraft to perform traditional observation functions but added another traditional role — using small aircraft to facilitate communications between widespread ground elements (especially artillery) on the move — and to ensure that air support met the needs of the ground commanders in an environment where distant communications were unreliable. To do that, the aircraft needed to be able to land pretty much anywhere.

As it turned out, the O-49 was too big and too expensive for the Army. By the summer of 1940, British and French experience showed that Allied forces suffered from a lack of suitable liaison aircraft, in contrast to the Wehrmacht, which didn’t. The U.S. Army then purchased thousands of military variants of the J.3 Piper Cub (called L-4 Grasshoppers) and Stinson’s L-5 Sentinel, and used them extensively in every theater of war. That capability lasted through Korea, waned afterwards, and came back with a vengeance in Vietnam. In the intervening years, however, the perceived need for this class of airplanes diminished, which advances in communications facilitated. The Department of Defense hasn’t had a liaison airplane since the 1980s. If the next war occurs in conditions where military communications remain intact, cyber warfare remains unused, and airfields are not subject to attack, then the United States can probably do without the liaison aircraft. In the absence of those unrealistic assumptions, however, the Department of Defense is missing a critical wartime capability, and it’s not clear the absence is even noticed. Whatever happened to liaison aircraft?

Back in the Day

When World War I broke out in August 1914, the airplane was still brand new, newer than transcontinental wireless (1901), the Zepplin (1900), the machine gun (1861), or the submarine (1775), which military professionals all considered key technologies of the era. The Army Air Service used early aircraft, designed to carry one or two people aloft, to keep tabs on enemy ground forces and direct artillery fire — exactly like Union observation balloons in 1863. Indeed, the observation function was the first military mission for the technological marvel. (The need to prevent observation aircraft and bombers from accomplishing their missions prompted the development of pursuit aircraft (fighters)). The observation aircraft was well-suited to the static battlefields of World War I, and the ability of early aircraft to operate from grass or dirt fields was excellent — because the first paved runway didn’t appear until 1924. Aircraft designed to carry a pilot and observer (or pilot and gunner) could just as easily carry a pilot and passenger, and perhaps some documents. In the mud-drenched warren of dirt roads that was endemic to World War I, the Army Air Service utilized the aeroplane’s ability to jump over poor transport routes extensively. The aeroplane proved itself to all of the major combatants.

Just what it proved, exactly, was the subject for much post-war debate. The Army never lost sight of the idea that slow aircraft could provide an excellent perch from which to observe conditions on the ground, even with no enemy presence. In the interwar years, the U.S. Army bought more observation aircraft than any other type, although arguments about their utility extended up and into World War II. As late as 1940, the Army was still split into multiple factions, all with a different identified need for some kind of aircraft — and without a hint of the demands that modern warfare would impose. An extensively researched history from 1945, The Evolution of the Liaison-Type Airplane, (from which this article draws extensively), points out that by 1939, the Army hadn’t conducted a realistic combined arms exercise since 1920, allowing it to miss entirely the specific needs for its light aircraft. On the European battlefield in World War I, the Air Service used “observation” aircraft extensively for artillery spotting and reconnaissance. In 1940, the Wehrmacht blitzed across Europe, amply supported by the F.156 Storch (Stork), a short-takeoff and landing liaison aircraft that did everything about which Allied military officers still argued. By the end of World War II, light liaison aircraft had performed a complete set of missions well beyond the observation and liaison missions for which acquisition managers procured them.

Figure 1: Finnish Lieutenant General Siilasvuo prepares to leave Uhtua on February 19, 1942, during the Continuation War. The aircraft is a Luftwaffe ski-equipped F.156 Storch (SA-kuva, Finnish Wartime Photography Archive)

Observation aircraft became liaison aircraft just before World War II, and the role adapted throughout the war. These aircraft still performed observation missions, but they also did more: Light aircraft conducted casualty evacuation, search and rescue, forward air control, VIP transport, surveillance, antisubmarine warfare, and even attack missions. History credits Lt. .Col (then a major) Charles “Bazooka Charlie” Carpenter with destroying six tanks (including two of the mighty Tigers) and immobilizing eight more — with a six-pack of bazookas bolted to the wing struts of his Grasshopper, “Rosie the Rocketer.” The liaison aircraft had evolved into a small, multipurpose aircraft that could land almost anywhere and accomplish missions that involved putting an airman, or a passenger, mail, or precious packages, wherever and whenever they needed to be. For the invasion of Sicily, the L-4B Grasshopper used six converted landing ships as mini carriers. After June 1944, Allied air superiority over Europe was sufficient to allow the Grasshoppers — including ski-equipped variants used in wintertime — to roam where needed.

Figure 2: Major Carpenter and his bazooka-armed L-4 Grasshopper, 1944. Maj. Carpenter would have had to take shots in a diving attack, with a hand-built sighting system — at close range. (Library of Congress)

In the Pacific, the Army used L-4 and L-5 aircraft for similar purposes, under wildly different conditions than in Europe. In the Pacific, L-4s were used in the same way that helicopters would later be used in Korea – evacuation of casualties from the very front lines. In the Philippines, the Army used two landing ships as mini-carriers, and U.S. Army Air Forces Captain James Brodie (OSS), came up with a trapeze-based system called the “Brodie Landing System” that consisted of a cable strung off the side of a landing ship or Liberty Ship. Awkward but functional, this system allowed the ship to maintain its original purpose in addition to carrying spotting aircraft, which also had an antisubmarine role. Engineers built a land-based variant of the landing system for the Far East; while the Americans never used it, the British tested it in Burma. The light observation aircraft were simply too handy to do without. Korea and Vietnam saw similar demand for light aircraft; in Korea it was not only the same aircraft type but often the same exact aircraft the Army used in World War II.

Figure 3: The U.S. Navy tank landing ship LST-16 underway in the Mediterranean, circa 1943. It earned five battle stars at Tunisia, Sicily, Salerno, Anzio, and Normandy. In the Mediterranean, technicians fitted the ship with a 220 x 16 foot steel-plank flight deck; here with a U.S. Army Air Forces Piper L-4 Grasshopper ready for takeoff. The service later reconverted it for landing on Omaha Beach. The Coast Guard landed the LST-16 like many LSTs. (U.S. Navy Photo)

Modern Clones

The liaison aircraft has long since disappeared from the U.S. arsenal; the Vietnam-era O-1 Bird Dog and O-2 phased out of Air Force service in 1974 and the late 1980s, respectively; predictably, the Army kept its O-2s around until 2010, but only as range-control aircraft. Today, remotely piloted aircraft fill the observation role — at a comparatively exorbitant cost. Helicopters conduct casualty evacuation. FedEx handles small package delivery. There are no remaining lightweight, manned aircraft with an operational mission. The roles for this category of aircraft still exist; it’s just that the Air Force has lost sight of the empty holes in its airpower portfolio. It need not be that way.

Today, civil aviation manufacturers in the United States do exactly what their forerunners did in the 1930s — provide a wide range of civil-built airpower options that would serve the role formerly held by liaison aircraft, if the government took an interest. Just as the more powerful Cub Special and Super Cub replaced the Piper Cub, a wide variety of light aircraft exist to do everything the Piper Cub did, and more. An entire industry emerged around supporting “bush aircraft,” intended to haul people and cargo to otherwise inaccessible locations. Excluding kit-built aircraft, at least three factories churn out F.A.A.-certified Super Cub clones in the United States today. Aviat (Maine) makes the A1C Husky, a Super Cub clone that is fully certified for instrument flight. CubCrafters (Washington) manufactures several copies of the Super Cub, including Top Cub, Carbon Cub and XCub. American Legend (Texas) builds modern variants of the Cub, Cub Special and the Super Cub, and even offers a Grashopper-styled “Combat Cub” paint job for any of them. Prices range from $200,000 to a half-million dollars, depending on avionics and options.

Modern Applications

The existing lack of liaison-type aircraft is yet another missing piece in what could be a much more versatile collection of airpower capabilities in the U.S. Air Force. The utility of the, well, utility-type aircraft is simply too great to ignore. One might envision applications for featherweight airlift, infiltration and exfiltration, clandestine gray zone operations, rescue and recovery, maritime patrol, training, reconnaissance, medical evacuation, and observation and surveillance missions. At the ridiculously low unit cost and cost per flying hour, this class of aircraft would be a marvelously cost-effective way to provide airpower, particularly in far-flung locations. Much longer-ranged and far less maintenance-intensive than helicopters, the ability to land and takeoff from roads, fields, forest clearings, and just plain level surfaces approaches that of rotary wing aircraft — only without the distinctive noise and dust cloud.

One can imagine light forces, such as special operations forces in Africa, using liaison aircraft to provide overhead watch. Aviation fuel can run most of the piston engines Cub-class aircraft use, making it possible to land and refuel from a convoy with no more than a stepladder and jerrycans. Medical evacuation crews could use that same aircraft on that same mission in cases of injury. Using small, commercially available links would allow real-time transmission of overhead imagery directly to soldier tablets. If a liaison aircraft had been overhead for the ill-fated mission in Africa that ended in the loss of four soldiers, a different outcome could be envisioned. For a long-term commitment against violent extremists, or for a conflict in Europe, or for never-ending commitments in the Middle East, or even for operations off of small islands in the Pacific, it is easy to find a niche this class of aircraft can credibly fill — because it has done so before.

Adopting the Orphan

Considering reentry into this corner of airpower application would serve the Air Force well. The service is always in danger of focusing on technology over utility, and conditions where funds are limited and the marquee aircraft is staggeringly expensive to own and operate only exacerbate this tendency. The reality of the next major conflict is that all of the participants will be employing advanced technology, and that communications may very well be the first target. It isn’t that the Air Force shouldn’t pursue high-tech solutions; it is only that the Air Force should also remember that low-tech, inexpensive airpower applications are no less useful because they are simple and cheap. A relative handful of liaison-type aircraft could have an outsized impact on a modern conflict in Europe, for an investment that is barely more than budget dust. Airmen should not lose sight of the fact that airpower comes in more than one flavor, and that the most expensive solution is not automatically the best.

Figure 4: LST-906, with a brace of L-4 Grasshoppers on her flight deck. Four other aircraft are stowed alongside (U.S. Army Signal Corps photo)


Col. Mike “Starbaby” Pietrucha was an instructor electronic warfare officer in the F-4G Wild Weasel and the F-15E Strike Eagle, amassing 156 combat missions over 10 combat deployments. As an irregular warfare operations officer, Col. Pietrucha has two additional combat deployments in the company of U.S. Army infantry, combat engineer, and military police units in Iraq and Afghanistan. He is currently assigned to Air Combat Command.

The views expressed are those of the author and do not necessarily reflect the official policy or position of the Department of the Air Force or the U.S. government.

Image: Army Air Corps Stinson L-1 Vigilant: The First of the Liaison aircraft (Air Force Museum Photo)