Air Reconnaissance in World War One
by Del Kostka
For most people, the great aces are the most enduring personalities of World War I. Almost 100 years after they blazed across the skies of Europe, names like Richthofen, Bishop, Guynemer and Rickenbacker are still memorialized as the chivalrous "knights of the air". Yet few people today give thought or credence to the pilots and observers of reconnaissance aircraft. Often portrayed as lumbering and defenseless victims of air combat, aerial reconnaissance crews actually made an impact and contribution to the war effort far greater than their glamorized brethren. The accuracy and timeliness of the intelligence they gathered changed the nature of warfare, and the devastating artillery barrages they orchestrated from high above the battlefield accounted for more casualties than any other weapon system of the Great War. Simply put, the reconnaissance aircrew was the most lethal killing machine of World War One.
Air reconnaissance operations during the First World War were not for the feint of heart. The mortality rate among pilots and observers during the Great War is legendary. Air crews fell victim to mechanical failure, weather, ground fire and air-to-air combat. It was not even unheard of for reconnaissance aircraft to be struck and obliterated by the very artillery rounds they were directing. Life in the air was turbulent, confined and freezing cold. Often, airmen who had just returned from a reconnaissance mission were so numbed and dazed from prolonged exposure, that they literally had to thaw out before they could report their observations in a coherent and intelligible manner.
There was no doctrine for air reconnaissance operations in 1914. The first flight crews developed their own tactics and procedures through hard-earned experience. However, the lessons they learned were channeled into an entirely new industry focused on improving the evolving intelligence discipline. World War One saw incredible advancements in aviation, photography and communication technologies. The airmen themselves underwent a tremendous evolution as well. As new technologies and reconnaissance capabilities appeared, basic flight training evolved into a highly technical curriculum for both pilots and observers. We can gain a great deal of insight into the importance of aerial reconnaissance operations by studying this transformation of men, machines and process during the Great War.
The Early Years
The concept of aerial reconnaissance did not originate with the Great War. As far back as 1794, the French military used observation balloons to detect and monitor enemy troop movements during the French Revolutionary War. Balloon technology evolved considerably throughout the nineteenth century. During the American Civil War the Union forces employed a small number of observation balloons manned by non-military ballooning enthusiasts. They were ineffective from a tactical perspective, but the experiment did enhance the timeliness of strategic intelligence reporting, including the first telegraphic transmissions from an observation gondola directly to the War Department in Washington DC. In the Franco-Prussian War, the French used untethered balloons to pass communications over the Prussian blockade during the 1870 siege of Paris. This inspired their Prussian adversaries to develop the worlds first antiaircraft artillery capability.
Stationary reconnaissance was still the mainstay of aerial observation at the outbreak of the Great War, and remained an important component of intelligence gathering throughout the conflict. But balloon observation had serious limitations. A spherical balloon could not be used in winds greater than 20 miles per hour, and even a light breeze made for a very unsteady observation platform. Of course the big shortfall of balloon observation was the fixed position and the limited line of sight imposed by a tethered platform. As the size and complexity of the battlefield increased, the need for further penetration necessitated the move towards fixed wing aircraft for aerial observation.
Observation balloons were an important component of aerial surveillance throughout the First World War, but they had significant limitations.
The very first use of fixed wing aircraft for reconnaissance purposes actually predates the First World War by several years. On October 23, 1911, an Italian monoplane scouted Turkish infantry positions outside of Tripoli, Libya during the short lived Turco-Italian War. It marked the first operational use of an airplane for military purposes and was a major factor in the Italian victory. The outbreak of World War 1 in August of 1914 saw each belligerent rushing to take advantage of the flying machine as an instrument of warfare. Initially, military strategists felt the sole purpose of aircraft in battle was to observe enemy movements along the front. However, as the commanders soon realized, the rules of warfare were changing. No longer could a cavalry reconnaissance unit envelop the flank of an army that was entrenched over the span of a continent, nor could battlefield commanders harness the awesome power and range of new heavy artillery without a responsive and accurate method of targeting. Fueled by necessity, the First World War saw the evolution of the humble flying machine into a fast, powerful and maneuverable instrument of war, and airmen of limited skill and knowledge into the most effective intelligence agents of their generation.
At the beginning of the First World War, each countries air service consisted of unarmed, general purpose aircraft. Most early aircraft were a "pusher" configuration with the engine located at the rear of the plane to push the ship forward. Early pusher aircraft were notoriously slow and cumbersome in the air, but they did offer some distinct advantages for reconnaissance. The slow and stable ride was ideal for observation, and with the engine in the rear the visibility was excellent. As 1914 drew to a close, the typical reconnaissance aircraft had a 90 hp engine, a top speed of 70 mph, and could reach the then impressive altitude of 12,000 ft.
Early pusher style aircraft, like this British Airco DH-1, were no match for single seat scouts designed specifically for air to air combat.
As each combatant realized the benefits of their own air reconnaissance efforts, it became apparent that it was a huge tactical advantage to deny the enemy the same detailed view of the battlespace. Soon, pilots and observers began carrying rifles to shoot at enemy reconnaissance flights. By 1915, both sides were designing “scout” aircraft, single seat fighters specifically designed to engage and destroy observation aircraft. Greater horsepower and an engine-forward "tractor" design provided the scouts more speed, more agility and higher rates of climb then their pusher style adversaries.
The first significant development in air-to-air combat was the Eindekker E-1, a monoplane scout produced by Dutch aircraft designer Anthony Fokker for the Imperial German Air Service. The E-1 could obtain a top speed of 87 mph and reach a ceiling height of only 11,800 ft, but it made up for it's lack of engine performance with an ingenious and lethal integrated weapons system. Prior to the E-1, the great challenge of the more efficient tractor design was the forward-mounted propeller which prohibited the placement of machine guns within easy reach of the pilot. Fokker solved this problem by developing an “interrupter gear.” Attached to the propeller shaft, the interrupter gear synchronized the machine guns trigger mechanism with the revolutions of the propeller allowing the gun to be mounted on the engine cowling directly in front of the pilot. Armed with the E-1's, the German Imperial Air Service methodically swept the skies of Allied reconnaissance aircraft.
Germany's Eindekker E-1 ruled the sky in early 1915
To counter this “Fokker Scourge,” the British developed an enhanced reconnaissance aircraft with a bite of it's own. Introduced in late 1915, the FE-2 was an advanced version of the pusher-type air frame. It was incredibly stable in the air, and the enormous engine block in back of the pilot offered the crew some measure of protection against marauding air predators. The FE-2 had a single 7.7mm Lewis machine gun mounted in the front nacelle, and a second Lewis mounted on the surface of the top wing to defend against rear-approaching attackers. Although the front mounted machine gun offered the observer an excellent field of view and firing arc, the top mounted weapon required him to stand on his seat to fire the weapon. This was a very precarious situation considering the observer had no advance notice or indication of the evasive maneuvers taken by the pilot. At 100 miles per hour, with the plane twisting, turning and diving, the observer's only hold on life was the suspect gun mount of his Lewis machine gun.
An FE-2 observer demonstrates how the top mounted machine gun could be used to fend off attack from the rear. The procedure was a bit more terrifying when performed at 5000 feet.
The possibility of being hurled out of the airplane was not the only drawback of the FE-2's pusher style airframe. Both pilot and observer had to maintain an iron grip on any loose artifact. An unattended map case or ammunition drum could quickly be sucked into the powerful rear-mounted propeller and disable the aircraft in mid-flight. And pusher style aircraft were notoriously deadly in a crash, as the occupants were followed into the ground by the massive engine and fuel tank. Although the FE-2 served for the duration of the war, it was the last pusher style aircraft to make a substantial contribution to military planning and operations.
Throughout the Great War, each belligerent continued to develop new aircraft and aircraft technologies for the expressed purpose of observing the enemy via the air, and preventing their adversary from doing the same. New two-seat tractor designs that placed the observer behind the pilot traded view for performance, but greatly enhanced aircraft speed, altitude and endurance. Improved avionics, such as redundant control wires to lesson the impact of severed cables, improved the survivability of reconnaissance aircraft as well. By war's end, Britain's premier armed reconnaissance fighter, the Arco DH-4, had a 250 hp engine, could climb to 22,000 ft, and reach speeds in excess of 143 mph.
Air Photo Reconnaissance Comes of Age
The original intent of aerial observation was simple visual reconnaissance. The crew would carry a note pad to record observations and sketch hostile positions, but the quality and accuracy of their reports were limited by the observers experience, artistic ability, and the turbulent, arctic environment of the open air nacelle. In September of 1914, an industrious British observer took his personal box camera along on a mission and took five photographs of enemy gun positions. The photographs were grainy and blurred, but once on the ground a detailed study of the prints revealed context information and details that would have been overlooked by even the most sharp-eyed observer. The art of air photo interpretation had been born.
Soon, intelligence units of both sides were clamping bulky, high resolution cameras to the outside of the fuselage to photograph the terrain directly below the aircraft. The plate glass film frames were heavy and required a 35 minute development process after the plane landed, but the photos revealed details about the enemy's elaborate trench system never before realized by military commanders. Photo mosaics were created that surpassed the currency and accuracy of any cartographic product of the era. Intelligence analysts even utilized the most popular parlor entertainment of the day to enhance their knowledge of the battlespace. Stereoscopic imagery, obtained via a dual-lensed camera that took two exposures simultaneously, provided a three-dimensional view of the terrain and allowed analysts to detect even the most elaborately camouflaged gun emplacements.
A British observer adjusts his camera prior to a mission
Photo reconnaissance was exceptionally dangerous work. Most early photo missions were conducted between 4000 and 5000 feet, well within range of anti-aircraft guns. An accurate photo mosaic also required total concentration by both pilot and observer. The pilot had to continually look from map to ground to instrument panel in order to keep the aircraft on a precise course with consistent air speed and altitude. Managing the camera was the full-time duty of the observer, who used a stop watch to ensure the correct overlap of each exposure. It was extremely easy for an enemy scout to sneak up on a pre-occupied photo reconnaissance aircrew. In fact, over half of Manfred von Richthofen's 80 victories were observation aircraft.
Even when a reconnaissance aircrew survived the gauntlet of dangers in the sky, a safe return to the aerodrome was no guarantee of mission success. Early photo development equipment was crude, and the correct mixture of chemicals, exposures and drying times was very much a trial and error process. Subtle atmospheric anomalies could also be a challenge, as the camera lens would detect and record atmospheric haze that was transparent to the pilot and observer. But like the aircraft themselves, the utility of aerial photography inspired a technological revolution of its own. Soon, cameras were being produced that were designed specifically for use in aerial photography, and the war brought major improvements in camera stability, shutter speed and lens quality. The Germans advanced optical lens technology so dramatically that photographs taken at 15,000 feet could be enlarged to show footprints in the mud. By the time of the Armistice, aerial photography and air photo interpretation had given aerial reconnaissance an identity and a value not predicted by even the most optimistic of early air advocates.
A Communication Breakthrough
As an observation platform, aircraft had proven their ability to fly over enemy positions and report on enemy troop movements. However, one lingering concern was the timeliness of information obtained by the reconnaissance unit. In the early days of aerial reconnaissance, the preferred method of communication was to land near the front and report intelligence in person. This was hardly a risk free or practical method of communication given the lack of established airfields near the front. Soon, reconnaissance units of both sides began dropping messages in weighted canisters and bundles. The air drops improved the timeliness of intelligence, but unless ground units were alerted to expect the air drop, the valuable intelligence would often lay unnoticed in the mud and debris of the front lines. Some units devised signal systems using klaxon horns or colored lights, but these were difficult to detect from the ground and often led to misinterpretation. The real breakthrough in air to ground communication occurred in late 1914 when the British began experimenting with wireless telegraph equipment.
Wireless technology of the era had some obvious drawbacks. First, the equipment was too heavy and bulky for planes to carry both a transmitter and receiver, so planes flew with a transmitter only. Second, in order to omit a clear signal the aircraft would have to descend to an altitude below 5000 ft and unreel a wire antennae that dangled 150 feet behind the plane. And Morse code was hardly the fastest method of communication when relaying complex observations. A skilled observer could only send messages at a rate of up to 12 words per minute. Still, the benefits offered by this crude method of communication revolutionized air reconnaissance, and nowhere did aerial reconnaissance change the nature of warfare more than in the coordination and targeting of artillery.
The Lethal Eye in the Sky
To really appreciate the impact and value of airborne artillery spotting, one needs to understand the incredible advances in artillery technology in the decades preceding the Great War. Just 40 years prior, the French and German armies were still using horse-drawn cannon to pound each other during the Franco-Prussian war.39 Targeting was generally accomplished through a time honored system of flash spotting and sound ranging. As the name implies, a designated spotter would use a stop watch to calculate range based on the interval between the flash of the muzzle and the report of the guns. Once the range was determined, the cannons were aimed entirely by sight, and their stiff recoil knocked the cannon out of position with every shot. By the later part of the 19th Century, breech-loading howitzers had been developed that could absorb the recoil, allowing the gunners to engage enemy positions with far greater consistency and rate of fire. The new howitzers also had much greater range than the visual capacity of the gun crews. New methods had to be developed in order to improve accuracy and take advantage of this lethal technology.
Modern artillery, like this British howitzer, was the most lethal weapon technology of the war.
Even before the introduction of wireless, aerial spotting vastly improved the targeting process for long-range artillery. The first method used to calculate the range of a target via aircraft was simple trigonometry. A reconnaissance aircraft would fly over enemy positions at a predetermined altitude and drop a signal flare or smoke bomb when directly over the target. Grounds spotters, who used binoculars to keep watch on the aircraft, would calculate range to the target using the known altitude of the aircraft and it's look angle above the horizon. The method was equally effective at night when flight crews used colored lights to signal ground spotters. Rather than cause any substantive damage, the intent of a night barrage was simply to terrorize, but in this capacity it was extremely effective. Pity the unfortunate infantryman who happened to light a cigarette while under the watchful eye of an aerial observer.
Although the triangulation method improved general ranging of artillery, there were a number of factors that limited its accuracy. First, early fixed wing aircraft determined altitude by means of a barometer which could only approximate true height above the ground. Also, the aircraft had to remain under continual observation by the ground spotters. Atmospheric glare or haze that did not prevent the reconnaissance crew from observing the target was often enough to obstruct the view of the aircraft by the ground spotters. Direct communication via wireless telegraph was the element that ultimately revolutionized targeting accuracy.
Initially, each wireless-equipped reconnaissance aircraft worked in conjunction with a single artillery battery. At the beginning of each mission, the aircraft had to locate their assigned battery by way of large canvass letters that were laid out upon the ground near each battery to form the letters of a code. Once the position of the battery was established and a target was identified, the observer would transmit a firing order to the battery using a “clock code,” an abbreviated Morse code template based on the face of a clock that indicated range and vector to the target. When the observer saw the first round fall in relation to the target, a second round could be directed with deadly accuracy. To the forces on the ground, being spotted and deemed a worthy target by an artillery cooperation aircraft was analogous to certain death.
Wireless receivers were located directly at the battery site. To allow more than one observation unit to operate in the same area, a “clapper break” was devised to set a distinct tone for each respective aircraft's signal. Signals were also heard and monitored at a central wireless station in each area. Should the wireless signal be degraded between any aircraft and their battery, the central wireless station could relay the target intelligence to the battery via a telephone line. Each side aggressively attempted to detect and jam enemy wireless communications, or inundate enemy receiving stations with bogus transmissions. The Germans even devised a “compass station” to detect and locate the source of wireless transmissions in order to direct scout patrols to the offending reconnaissance aircraft. The experiment had limited success due to the time lag between the location of the source and the arrival of the scouts, but the effort shows the critical impact of aerial reconnaissance upon ground operations during the Great War. Once wireless technology was integrated into the aerial reconnaissance and artillery targeting process, the resulting weapons system brought death and destruction to the battlefields of Europe on a scale the world had not imagined possible.
Just as technology evolved during the course of the war, so too did the skills and abilities of the pilots and observers. Early in the war, pilots were generally newly-commissioned officers. They received minimal training by today's measure, but at least they had a standardized form of instruction at established flight schools. By contrast, observers were generally volunteers from among the senior enlisted ranks who would gain their experience and develop their own reconnaissance methods over the front lines. But as aerial reconnaissance became more scientific, the technical skills required of observers increased as well.
In September of 1915, an aerial gunnery school was established in England to enhance observers marksmanship and survivability in air combat. A course in wireless technology and Morse code soon followed to help observers master air to ground communication. By the end of the war, each European nation had established special schools for the systematic training of observers. Besides wireless communications and gunnery, each observer was trained in map reading, photography and photo interpretation, as well as practical flying skills such as instrument reading, avionics and engine mechanics. The British also required observer trainees to spend two weeks serving as liaisons to front line artillery units, working directly with ground spotters in communication with aerial observation aircraft. Conversely, gunnery officers were required to fly periodic reconnaissance missions in the role of observer to understand the perspective of the flight crews. This joint training was invaluable to enhance the trust and working relationship between the Army and Royal Flying Corp.
Pilots and observers were among the best trained and highly skilled combatants of the Great War. Here, a group of Canadian airmen receive a lesson on avionics.
The air reconnaissance crews who fought and died during the first world war have largely been forgotten, but their courage and dedication to duty stand among the greatest achievements in aviation history. Their two-man reconnaissance aircraft were no match for light weight and heavily armed scouts that were specifically designed for air combat, and the open air environment was uncomfortable and rife with danger. Those who survived beyond the average pilot/observer life span of 16 weeks had to adapt to technical change at a frantic pace. Yet the air reconnaissance missions they flew in the skies over Europe revolutionized warfare and forged intelligence principles that are as relevant today as they were almost a century ago. They, and the reconnaissance airmen who have followed in their footsteps, deserve our unwavering admiration.
. “The Machine Gun 1914-1918.” bbc.co.uk. BBC, 23 Dec 2002. Web. 25 June 2011
. Ari Unikoski, “The War in the Air – Observation and Reconnaissance,” firstworldwar.com, 22 Aug 2009, Web. 25 June 2011
. Frederick Talbot, “Scouting from the Skies” worldwar1gallery.com, n.d. Web. 25 June 2011
. Mead, Peter. The Eye in the Air: History of Air Observation and Reconnaissance for the Army – 1785-1945. London: HMSO Books, 1983. 13. Print.
. Ibid, 17.
. Ibid, 18.
. Raleigh, Walter A. The War in the Air. Oxford: The Clarendon Press, 1922. 460. Print.
. Michael Duffy, “The War in the Air – Summary of the Air War,” firstworldwar.com, 22 Aug 2009, Web. 25 June 2011
. Raleigh, 293
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. Barker, J. Ellis. Introduction. The Red Fighter Pilot – The Autobiography of the Red Baron. By Manfred von Ricthofen. 1918. St. Petersburg: Red and Black Publishers, 2007. 8. Print.
. “1915 Aircraft.” militaryfactory.com, n.d. Web. 25 June. 2011
. Barker, 9.
. Hart, Peter. Bloody April. London: Orion Book Ltd, 2006. 43. Print.
. Ibid, 44.
. Ibid, 45.
. “1918 Aircraft.” militaryfactory.com, n.d. Web. 25 June. 2011
. Hart, Bloody April, 24.
. Mead, 66.
. Hart, Bloody April, 24
. Ibid, 316
. Hart, Peter. Aces Falling. London: Orion Book Ltd, 2007. 115. Print.
. Hart, Bloody April, 24.
. Talbot, Scouting from the Skies
. Pamela Feltus, “Aerial Reconnaissance in World War 1,” centennialofflight.gov, n.d. Web. 25 June 2011
. Frederick Talbot, “The Airman and Artillery” worldwar1gallery.com, n.d. Web. 25 June 2011
. Mead, 66.
. Hart, Bloody April, 25.
. Ibid, 59.
. Barker, 7.
. Hart, Bloody April, 36.
. Barker, 7.
. Talbot, The Airman and Artillery.
. Raleigh, 351.
. Ibid, 351.
. Mead, 75.
. Ibid, 76.
. Hart, Bloody April, 59.
. H.B. Ward, “Wireless Waves in the Worlds War, The Yearbook of Wireless Telegraphy and Telephony.” 1916, Pages 625-644. Web. 25 June 2011
. Mead, 89.
. Hart, Aces Falling, 27.
. Hart, Bloody April, 22
. Raleigh, 444.
. Hart, Bloody April, 104
. American Expeditionary Forces France. The Battle of Chatillon; A Graphic History of the second Corps Aeronautical Flying School. Grand Rapids: The Dean Hicks Company, 1919. Web. 25 June 2011
. Hart, Aces Falling, 21.
Copyright © 2011 Del Kostka
Written by Del C. Kostka. If you have questions or comments on this article,
please contact Del Kostka at:
About the author:
Del C. Kostka is a staff officer at the National Geospatial Intelligence Agency in St. Louis, Missouri. He has a Masters Degree in Operational Arts and Military Science from the US Air Force Air Command and Staff College.
Published online: 10/09/2011.