The Hurricane Aircat was an airboat used as a riverine patrol boat by the US Army and South Vietnamese Army (ARVN) during the Vietnam War. It was used to conduct various counterinsurgency (COIN) and patrol missions in riverine and marshy areas where larger boats could not go.
Background The Viet Cong (VC) insurgents, one of the US Army's main enemies in Vietnam, relied heavily on motorized and paddled sampans to move troops and supplies throughout the canals, streams, swamps, and rivers abundant in Vietnam, particularly in the Mekong River delta. The boats used by US forces prior to the Aircat's 1964 introduction relied on screw-propellers, which would become fouled by aquatic plants and thus rendered useless. US forces sometimes used paddled sampans to avoid this problem, although these sampans had the same speed as the VC ones and so were unable to effectively pursue and defeat them. Because US boats had trouble navigating the waters of the Mekong Delta, the region quickly became home to many Viet Cong strongholds and logistics bases.
In 1961, the US Navy brought airboats and pump-jet boats, neither of which rely on propellers in the water, to Vietnam at the behest of ARVN for testing. The Navy found that airboats outperformed pump-jets and screw-propeller boats in all respects except noise, although they concluded that airboats' noise made them unacceptable for use in counterinsurgency operations. Army special forces and others in the US and South Vietnamese militaries disagreed, however.
Development and selection In spring of 1964, US Special Forces advisers to ARVN forces in South Vietnam expressed a need for fast, shallow-draft boats. In response, the Commander of the Military Assistance Command in Vietnam, (COMUSMACV) stated an operational requirement in June 1964 for shallow-draft boats capable of carrying 4-5 troops plus crew-served weapons that could negotiate aquatic plants and other obstacles abundant in marshes and rice paddies at speeds of at least . The Commander-in-Chief of the US Pacific Command (CINCPAC) approved the request on June 19, 1964, and ordered six airboats from two commercial manufacturers—the Hurricane Fiberglass Products Company of Auburndale, Florida and Susquehanna Danville Airport of Danville, Pennsylvania—to evaluate and test them and then select a winner. The Susquehanna airboats were a joint venture between Ken Burrows-owned Danville Airport of Danville and Mari-Mar Industries of Port Trevorton, Pennsylvania. The two models of airboats evaluated were the Hurricane Aircat and the Susquehanna Skimmer.
Each Aircat and Skimmer cost about $6,000 each in 1964 (equivalent to about $49,000 in 2018).
The Army finished its evaluation by the end of 1965. The Aircat was found to be more durable, maneuverable, and have greater obstacle crossing capabilities than the Skimmer, although the Skimmer outperformed the Aircat in deep water. As such, the Army opted to begin purchasing Aircats in early 1966.
Design The Hurricane Aircat had a rectangular hull long with beam. The draft varied with speed but was no more than . At top speed, the Aircat could draw as little as a single inch () of water. The hull was made from five layers of molded fiberglass and was semi-catamaran fore and flat-bottomed aft. This unique hull shape helped the Aircat surmount higher obstacles.
The Aircat was powered by a 4-cylinder Lycoming O-360 aircraft engine providing . The engine was hooked up to a diameter aerial propeller. The propeller blades were made from wood and tipped with bronze, which sometimes caused a problem, as three propellers failed during the evaluation period when the wood rotted and the bronze tips were separated by centrifugal force. Steering was provided by a stick controlling two air rudders aft of the propeller and propeller guard. Counting crew and passengers, the Aircat could carry payloads of up to .
A .30 caliber (7.62 mm) M1919 machine gun was mounted on a pintle mount in the bow. These guns were found to be accurate up to , comparable to the guns of some WWII fighter aircraft. Some crews substituted this gun for the heavier .50 caliber (12.7 mm) M2HB machine gun to increase the boat's firepower, though the M2HB often proved too powerful for the flimsy vessel. While the gunner fired, the pilot had to pull forward to offset the gun's recoil or risk the boat being blown about or even capsized. The 57mm M18 recoilless rifle was test fired from an Aircat and proved impractical owing to its extensive back blast. The 106mm M40 recoilless rifle was used on airboats “frequently” by the 7th Armored Squadron, 1st Air Cavalry Division, who and “proven very valuable”. Using the 106mm recoilless rifle on an Aircat had little effect on the airboat or on accuracy, but issues arose relating to speed and maneuver (the boat could not attain top speed and was not as maneuverable) and ammunition (only 4 rounds can be carried in the boat with the gun; any additional rounds had to be transferred from other Aircats). The 106mm recoilless rifle was fired off to the side to avoid exposing crew to the back blast. The Aircat enabled bringing the weapon over “terrain where normally a heavy crew served weapon could not be used”.
The Aircat was equipped with an AN/PRC-25 radio for short-range communication. The AN/PRC-25 posed challenges because of the difficulty hearing the radio over the engine noise and the fragility long antennas, which took a beating from bushes, trees, and other obstacles. Testing by the 5th Special Forces Group found that the noise issue could be overcome by using the radio with a CVC tanker's helmet and that the antenna vulnerability issue could be fixed by using a vehicular radio and antenna such as the AN/VRC-12 or AN/VRC-16. Nevertheless, radio problems persisted at least through 1968–69.
Operational history
During the Vietnam War the Hurricane Aircat was used by US Special Forces and ARVN to patrol and attack in riverine and marshy areas where larger boats could not go. Aircats were used primarily in the of the Mekong Delta and Plain of Reeds though they also saw action in the Bảy Núi mountains near the Cambodian border. Its most important contribution to the American war effort was in allowing American Green Berets to attack previously unassailable Viet Cong (VC) support bases and strongholds in wetlands and swamp forests. Aircats saw combat on many occasions in which they engaged Viet Cong forces, captured enemy documents, weapons, and munitions, and received enemy fire and suffered casualties. The Aircat proved effective at many types of missions: in its 104 missions in 1965, encompassing reconnaissance, flank security, and assaults, it killed 86 VC, destroyed 26 of their boats, and achieved most mission objectives.
Aircats were able to clear obstacles that proved insurmountable for other boats. The Aircat could cross high dikes at and there were several examples of US troops encountering obstacles or blockades in other watercraft, such as Swift Boats and river patrol boats, making a note of the obstacle, and then returning in Aircats and proceeding over it. These characteristics made the Aircat invaluable during the rainy monsoon season, as it could easily cross flooded rice paddies and jump dikes between paddies.
The Aircat was very fast relative to other patrol boats, being capable of speeds up to in deep water and on shallow water or rice paddies. Its speed made it ideal for reconnaissance, providing flank security for riverine assault boats, and special forces use. The Aircat's speed and maneuverability was important for US Special Forces because they were able to outrun and outmaneuver most enemy vessels. As such, the craft was used widely by special forces for pursuing and assaulting Viet Cong units in flooded areas in the Mekong Delta. That said, the Aircat's speed and maneuverability could also be a disadvantage, as Aircat crews would often get disoriented without constant aerial observation. The 5th Special Forces Group was especially noteworthy for its use of Aircats, operating 84 of the vessels in the Mekong Delta beginning in early 1967. Colonel Francis J. Kelly, commander of the 5th Special Forces Group from June 1966 to June 1967 and author of a book about US Army Special Forces in Vietnam, praised the Aircat for its "speed and firepower," writing that once tactics adjusted to employ the Aircat to maximum effect, Aircats enabled "telling victories over the Viet Cong" and turned the flood season into a tactical advantage for US forces.
The use of Aircats, increases in troop strength, and introduction of other tactics allowed the 5th Special Forces Group to take the fight to the VC and capture territory in the Delta, helping to make the 50% of territory and CIDG bases that were previously too overrun with Viet Cong to enter safe enough to operate in. It also helped the 5th Special Forces Group mount operations and establish CIDG bases deep into territory previously under the control of the Viet Cong. These gains were not without cost, however: 55 Special Forces and 1,654 Vietnamese were killed during 1967, as well as an estimated 7,000 Viet Cong. The 5th Special Forces Group found that the Aircats were most effective when used in combined arms operations with gunships, as the gunships would locate and engage the enemy while the Aircats would use their speed and maneuverability to seal off escape routes.
The Aircat was also valuable to special forces because it could be easily transported by Chinook helicopter, allowing for flexible operations across southern Vietnam.
In addition to special warfare use, Aircats were used by the South Vietnamese government for transporting important officials and by Vietnamese police forces for inspecting fishing boats.
Crew sizes varied greatly by mission. The Aircat could carry as many as 12, although it generally carried no more than six. Crew sizes were reduced to an average of 5–6 in response to a December 1964 accident in which an airboat carrying 11 ARVN soldiers sank in the Mekong River, drowning five. Observers at the scene believed that the overloading of the boat contributed to the accident. Normal roles for the five-soldier crew were one commander/operator, one machine gunner, one radio operator/assistant gunner, and two riflemen. Aircat airboats in American and South Vietnamese service operated in units of six boats. In use by special forces units, the Aircat often operated with a crew of three: commander/pilot, gunner, and radio operator/grenadier. A rifle platoon could be transported in 6–8 boats.
Initially, Aircats were able to operate with impunity, as they were faster and sturdier than any enemy vessels. Their dominance of the Mekong Delta led the Viet Cong to develop dedicated anti-airboat tactics and introduce several dedicated anti-airboat traps, including a light naval mine mounted on the end of a bamboo pole and piano wire strung between wooden poles that held fishing traps, used to decapitate or injure airboat drivers and gunners. The change in VC tactics exposed a major weakness of the Aircat: the fiberglass hull offered no protection against gunfire or shrapnel. Standard defensive tactics for the Aircat were to "avoid becoming decisively engaged," i.e. to dodge enemy fire and perform offensive actions. The Aircat was also modified to defend against the piano wire traps by welding a large piece of iron to the gun mount that would protect the Aircat crew from the wire.