Azon Guided Bomb

AZON, the first guided bomb developed by the United States. The VB-2 version is pictured.

 

AZON (or Azon), from "azimuth only", was one of the world's first guided weapons, deployed by the Allies and contemporary with the German Fritz X.

Officially designated VB-1 ("Vertical Bomb 1"), it was invented by Major Henry J. Rand and Thomas J. O'Donnell during the latter stages of World War II as the answer to the difficult problem of destroying the narrow wooden bridges that supported much of the Burma Railway.

AZON was essentially a 1,000 lb (454 kg) general-purpose AN-M65 bomb with a quadrilateral 4-fin style radio controlled tail fin design as part of a "tail package" to give the desired guidance capability, allowing adjustment of the vertical trajectory in the yaw axis, giving the Azon unit a lateral steering capability (meaning it could only steer left and right, and could not alter its pitch or rate of fall). This lack of any pitch control meant that the bombardier still had to accurately release it with a bombsight to ensure it could not fall short of or beyond the target. The "tail package" bolted onto the standard bomb warhead, in place of the usual sheet-metal fixed fins; this concept was an early iteration of a now common method of making modern guided bombs (such as the JDAM, the Paveway family, etc.): making the guidance and control units as separate pieces that attach to the tail and/or nose of a standard "iron bomb", making it into a guided weapon. There were gyroscopes mounted in the bomb's added tail package that made it an Azon unit, to autonomously stabilize it in the roll axis via operating a pair of ailerons, and a radio control system to operate the proportional-control rudders, to directly control the bomb's direction of lateral aim, with the antennas for the tail-mounted receiver unit built into the diagonal support struts of the tail surface assembly. The bomb's receiver and control system were powered by a battery which had around three minutes of battery life. The entire setup in the added "tail package" was sufficient to guide the weapon from a 5,000-foot (1,500 m) drop height to the target. Situated on the tail of the bomb was a 600,000-candela flare which also left behind a noticeable smoke trail, to enable the bombardier to observe and control it from the control aircraft. When used in combat, it was dropped from a modified Consolidated B-24 Liberator, with earlier development test drops of the Azon in the United States sometimes using the B-17 Flying Fortress as the platform. Some ten crews, of the 458th Bombardment Group, based at RAF Horsham St Faith, were trained to drop the device for use in the European theater.

The ability to only control the path of the bomb in the azimuth direction, made AZON bombs most suitable for long and narrow targets, such as bridges or railways. A disadvantage of using an AZON bomb was that after a bomb was dropped the bomber could not break away immediately, because the bombardier had to keep the bomb in view so he could guide it. The bombardier used a BC-1156 joystick control to adjust the course left or right. The directional commands were sent to the guidance package via a special-purpose radio system.

The 493rd Bomb Squadron also dropped Azon bombs in Burma in early 1945 from similarly modified B-24s, based at Pandaveswar Airfield, India, with considerable success, fulfilling the designers' original purpose for the ordnance.

Azon Operations

Azon Operations in Europe by the Eighth Air Force, June–September 1944
Target	Date	Result
Melun	8 June 1944	Mission 400: an attack on the Melun bridge by an Azon unit is foiled by clouds.
Ham-sur-Somme	14 June 1944	Mission 412: 7 of 15 B-24s hit the bridge over the Somme at Ham and 5 use Azon bombs against targets of opportunity; no losses.
Étaples	15 June 1944	Mission 414: 12 B-24s use Azon bombs against Étaples railroad bridge and 7 others use the bombs against the Pecrone railroad bridge.
Saumur	22 June 1944	Mission 432: 9 of 10 B-24s use Azon bombs against the Saumur Bridge.
Esternay	17 August 1944	Mission 558: 10 B-24s are dispatched to drop Azon bombs on the Les Foulons rail bridge near Esternay but the mission is abandoned due to deteriorating weather.
Moerdijk	25 August 1944	Mission 571: 10 of 10 B-24s fly an Azon bomb mission to attack railroad bridge at Moerdijk, Netherlands but the target is missed by all 40 bombs launched.
Moerdijk	26 August 1944	Mission 577: a second attempt on the Moerdijk rail bridge is made with 9 aircraft, but clouds prevent an attack.
Ravenstein	1 September 1944	Mission 597: 12 of 12 Azon-equipped B-24s hit the Ravenstein rail bridge in the Netherlands, without loss.
Hemmingstedt & Kropp	13 September 1944	Mission 629: 6 of 11 B-24s dispatched on an Azon mission attacked the Hemmingstedt oil refinery and 5 hit the secondary target, ammunition dumps at Kropp. Operation Aphrodite guided bombs also attacked Hemmingstedt the next day.

The Azon Bomb

by OCH #77, KA8MCC, MARION

from Old China Hands web site on the Internet Archive

In June, 1942, I was inducted into the armed forces at Camp Blanding, Florida. From Camp Blanding I was based in different parts of the country. My basic training was at Atlantic City, NJ; Wayne County Air Transport Command in a Guard Squadron outside of Detroit, Michigan; Scott Field Radio School outside of Belleville, Illinois and Harlingen Gunnery School in Texas.

I met my first crew at Hammar Field in California. Traveling to Muroc (now Edwards) Army Air Base, this crew broke up at the end of training. Shortly thereafter I got assigned to another crew. Eugene Morris was the pilot with Duane Jordan, co-pilot; Art Ruonavaara, navigator and Frank Nelson, bombardier. The enlisted men were: Thomas Dean, flight engineer, (then later Milfred Piper replaced Dean as our flight engineer). I was the radioman with Kenneth Robinson as my assistant in radio. The gunners were: Kenneth Robinson, Joseph (Sonny) Johnston, Hugh Fletcher the armorer/gunner, Andy Hocko a gunner and assistant flight engineer to Dean (later Piper). With the doing away of the ball turret, I became the person to open and close the bomb bay doors. This was to make that the bomb bay doors always open safely. Also, I could slightly open the bomb bay to have a ringside seat to see the hits. At the completion of our training, at Muroc, we received shipping orders to Hamilton Field in California.

After a week's stay at Hamilton Field, ten crews were selected for a highly classified cross-country trip to Ft. Dix, New Jersey. My crew was one of the ten selected. Settling down at Ft. Dix we were quickly briefed as to why we were there. Instructors, at Ft. Dix, told our ten crews that we were about to enter something new in warfare. We were told that we would have 'it' and the enemy would be seeking to find out what 'it' was. Security lectures were given and would be a daily ritual for the four weeks that we were in training.

Looking in our service records we discovered that someone had investigated all men for this training. The investigators had traveled to each man's home life area to know how we would rate on a top secret assignment We were given information on several new types of bombs. They were the Azon, Razon and Felix types. The Azon was radio-controlled, while the Razon was radio-controlled plus a television camera in its nose. Using a television receiver, the bombardier could guide it to the target. The Felix was a heat seeking type. The Azon equipment would be what we would train on and that training started immediately.

The Azon (Azimuth only) consisted of a radio transmitter and controls. The receiver was located in the tail assembly of the bomb. The tail fin assembly had four movable surfaces for the control of the bomb. Two surfaces were for the horizontal (roll) control and called the ailerons. The ailerons kept the bomb level when dropping and were controlled by a gyro. The other two surfaces, which were the rudder controls, were handled by the radio receiver located inside the tail and controlled the bomb left to right during its fall.

AZON Four braces were connected to the fins to support the aileron and rudder controls. The four braces were also the antenna for receiving the signal from the transmitter. The Azon transmitter antenna was located at the rear of the plane. The antenna was approximately three feet in length. One day some person, not connected to the Azon group, got curious about the antenna. He asked what the antenna was used for. A ground crewman, involved with the Azon equipment and mindful of the high degree of classification surrounding the project, answered, "It is a highly classified flak repellent gadget. It keeps the plane from getting hit."

A flare is placed on the rear of the bomb's tail assembly and timed to ignite when the bomb has dropped between five hundred or a thousand feet below the plane. This was a safety feature to keep the flare from firing too quickly. The flare would be either a bright white or red color which also would leave a smoke trail to aid in the guidance to the target. Our first day of lecture, we took notes as the instructor lectured. However, at the end of the day, we were instructed to surrender our notes. This Azon training was top secret material, therefore all notes had to be destroyed by burning. We were given a test over the training lectures at the end of the first day. I was able to answer two questions out of twenty five. I thought to myself that I would be washed out of this training. Failure of the lecture test was not to be. For a full week we trained with the training lectures given twice a each day. At the end of the week, each radioman and bombardier passed the test with flying colors. We could not fail. Everyone passed with a straight A. Everybody was now ready for phase two.

Our training involved instructing the radioman on how to adjust and tune the Azon transmitter. We were given instructions on the complete breakdown of the tail assembly. The bombardiers were given one step further on the Azon equipment. They had to know the controls that would move the dropping bomb from left to right. The Nordan bombsight was accurate to a certain point. Hitting a bridge, jetty or perhaps a boat meant that the Azon's bombardier would have to adjust the error. When dropped, the bomb could be moved left to right to score a hit. The Azon bomb was ideal for hitting a moving ship zig-zagging along. Frank, our bombardier, once made the remark that he wished he could have the opportunity to see a moving enemy ship. The bombardier had the Azon controls close to his bombsight. The controls were all assembled in a box with an on-off switch for the transmitter and the receivers. The receivers being located in the tail assembly attached on the bombs. A control stick, located on the box, was used to control the bomb's azimuth. Prior to release, the Azon receivers were powered from the airplane's electrical system. However, upon dropping of the bomb a battery located inside the tail would take over.

The practice missions, at Ft. Dix, were at altitudes of ten to twenty five thousand feet. Ground crews would load the bombs on the plane and install the tail assembly. The bombardier and radioman would give the equipment a quick checkup before takeoff. In flight the two men would check to ensure the rudders were in working order. On bombing missions the Azon equipment would be turned on about a couple of hours before arriving over the target. The radioman had to check to see if the rudders reacted to the transmitter signal. After a month of training, all ten crews were assigned to B-24 aircraft with the Azon equipment installed. Each plane was issued several Azon fins to be prepared for their first mission. Our shipping orders arrived and on August, 24, 1944 we were on our way to overseas. First to Mitchell Field, N.Y.; Grenier Field, N.H.; Newfoundland; Azores; Merrakech; Tunis; Cairo; Abandan, Iran; Karachi; Agra and Kurmitola, an ATC base. Kurmitola would be our home base for a while. We got a mission or two over the Hump hauling fuel supplies to China bases. On October 6 we moved to the base at Pandaveswar (called Panda for short). Here we would finally fly bombing missions which would make use of our Azon training. But we were in for a surprise. We were assigned to the 9th. Bomb Squadron of the 7th. Bomb Group. A colonel, who was in charge of operations, ordered the Azon equipment removed from the planes. We were astonished! We had gone through all of the training and listening to daily security briefings, now this.

We got a bombing mission to go after a bridge--number 277. I have no idea just how many planes vent after this target. Anyway it was a waste of time. No one made a direct hit. Frank, on our plane, dropped his bombs which hit to the right side of the bridge spans. A straight line of explosions, indeed. We began talking on the intercom and saying if we had had our Azon equipment we would have gotten that bridge. A later mission was for some shipping. The hits were fair at best.

November saw a change of a couple of our crew members. A couple of months previous, in September, Thomas Dean had to leave our crew at Karachi. He had been showing evidence of back problems. These back problems were slowly getting worse as the days went by. Thomas was admitted to the base hospital at Karachi and would be permanently grounded within a few days. Andy Hocko, our assistant flight engineer and gunner, had to take over the responsibility of the flight engineer. Thomas was shipped back to the US for further hospital care. Later, at Pandaveswar, Milfred Piper joined our crew as flight engineer. Our navigator, Art Ruonavaara, began having problems with malaria which started at Kurmitola. At Pandaveswar, Art came down with the malaria once again and had to be hospitalized, A new navigator joined our crew temporarily. His name was Flight Officer Merle Wiley.

December of 1944, we and eleven other crews were sent to China on detached service to the 14th Air Force. Our assignment was to haul fuel and miscellaneous supplies to certain bases in China. Some of this had to be flown over the Hump from India. The Japanese had cut China into two sections. Our assigned base in China, was Luliang. From Luliang crews had to haul fuel and supplies to Suchow which was located east of the Japanese line. Luliang was located west of the Japanese line. One of these flights, across the Hump, was hauling a load of liquor. We picked up several cases of liquor at Pandaveswar to haul to Luliang. Upon arriving to Luliang a captain, in a jeep, drove up. He asked, "Has any of the cases of liquor been opened." We gave an answer of "No sir." The captain proceeded to open each case and examine each bottle to see if the seal was broken. This captain bugged us about looking at each bottle so carefully. The captain loaded the liquor in his jeep and drove off. I made the remark, "What is the matter with that captain, doesn't he trust us."

Shortly after Christmas, orders came for us to quickly return back to Pandaveswar. Back at Pandaveswar we were in for some good news. While we were in China, a major came to the 7th Bomb Group wanting to know why no reports were submitted about the Azon equipment. The operations colonel explained that the Azon equipment had been taken off. The major, angrily, then began explaining to the colonel that the Azon equipment was a project ordered by General Arnold. Orders were that all Azon equipment must be replaced back on the planes immediately. All Azon crews were given back the planes we had flown over, with all Azon equipment installed back in place. The Azon crews and planes were then transferred from the 9th to the 493rd Bomb Squadron. The 493rd. then became known as the Azon Squadron.

We began to get results with our Azon equipment. We got bridge after bridge. There is no need to go into detail about each mission as they would all be the same. We got the bridges! Soon, this made the other squadrons a bit jealous. Other groups wanted to get the Azon. But, as the officer at Ft. Dix said, "You will have IT." So we were enjoying IT. During our missions, the ground crews had rigged up the Azon transmitter so its signal could be heard over the plane's intercom. We all had a ringside seat watching the bomb fall. Hearing a low hum over the intercom, we would see the bomb move to the right. A high pitch hum, we would see the bomb move to the left. Always, we had a good fighter escort to keep the Japanese planes away. The only thing that we had to worry about was flak. On January the 23rd 1945, we were to go after bridge 277 with the Azon. However, bad weather set in. All planes were ordered to return home. We removed the Azon tail assemblies and dropped the bombs into the bay before returning to our home base.

Later orders came to bomb bridge 277 at low level. Frank made a good hit, knocking the steel and concrete bridge out in one span. Our crew received credit for hitting the bridge. There were no planes lost although we took some hits. Only one life was lost in all of the planes going after the bridge, which I later learned was the famous "Bridge on the River Kwai."

Shortly after the mission for bridge 277, Art began to get his malaria problem once again. This time the attacks were worse than previous attacks. Art was in the hospital for several days. Finally he was released back to the 493rd. This time Art lost several pounds in weight. The decision was then made by the medics to return him back to the US to get better care. We had to bid Art farewell as he left us to return back to the US. Our crew was then assigned a new navigator, Kenneth R. Van Zandt. Also at this time, Milfred Piper had gotten in all of his combat flying time in. We all bid Milfred a farewell as he flew out. We got another replacement for Milfred's position. His name was Pete Hoidra.

In May, 1945, we received our shipping orders to return back to the US. We were flown, by a B-24, to Dum Dum. The plane buzzed us after leaving. The only crew members, to leave for the US, at this time were myself, Frank Nelson, Kenneth Robinson, Andy Hocko, Sonny Johnston and Eugene Morris. Eugene was to meet us just before hitting the boat for the US. Eugene had a delay at Pandaveswar for a couple of days. Hugh Fletcher and Duane Jordan were unable to leave with us. They would leave the base a couple of weeks later. Pete Hoidra and Kenneth Van Zandt were assigned to other aircraft. We waved back to the plane as the men, returning back to Pandaveswar, waved in return. How little did I realize that I would not fly again and that I was waving goodbye, also, to an old friend--the B-24J. I received my honorable discharge from the Army Air Force in October, 1945, at Drew Field, Florida.

 

Rear view of an Azon MCLOS-guided bomb, showing details. 

 

This is a World War II joystick for guiding bombs in flight. During the war, the Allies developed a system for guiding bombs so they could hit small targets, such as the wooden bridges that supported much of the Burma Railway. This system was known as AZON, because the guidance was “azimuth only” (i.e., the bomb could only be steered left or right, but the length of its path could not be changed). To control the bomb’s direction a collar with radio-controlled fins was attached to the back of a standard bomb, such as an M-65 1000 pound bomb. A flare was also attached to the bomb so the bombardier could more readily track the bomb as it fell. In combat, an AZON bomb was dropped from a Consolidated B-24 Liberator. After the bomb was released, the bombardier watched the bomb fall and used the BC-1156 control lever to steer the bomb left or right. While some AZON bombs were used in Europe, they were primarily used, with considerable success, in the China-India-Burma theater. (Steven Fine photo)

 

VB-1 Azon Guided Bomb in the World War II Gallery at the National Museum of the U.S. Air Force. (U.S. Air Force photo 090901-F-1234S-002)

 

VB-1. The VB-1 Azon - short for 'Azimuth Only' - was a radio command link controlled tailkit attached to a standard M44 and later AN-M65 1,000 lb bomb body. The Azon entered production in 1943, after earlier development by USAAC's Air Technical Service Command. The Azon used an annular tail assembly like the Fritz-X, was roll stabilized like the Fritz-X, but could only be steered in azimuth and thus it range error on delivery was similar to a dumb bomb. The Azon guidance package was limited to five preset radio channels, limiting the number of concurrent drops during a raid. The Azon kit was produced until November, 1944, by which time 15,000 units were built. It was deployed in the ETO from February, 1944, and used extensively in Burma for bridge dropping strikes. The 15th AF in the Mediterranean is credited with Azon attacks on the Danube river locks, and the Avisio viaduct. In Burma, Azons were used to destroy 27 bridges using 493 rounds, including the famous Kwai River bridge. 

 

The AZON bomb consisted of the tail fin unit being bolted to a 1,000-pound general purpose bomb. The fins and collar on an assembled bomb made it too large for transporting in the standard racks and tended to limit the number of bombs that could be carried to four.

 

Each Allied bomber outfitted with the azimuth-only system had three antennas mounted beneath its tail section for control purposes. One controlled left deflection, one controlled right deflection, and one activated the smoke system.