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The 2.75 inch Folding Fin Aerial Rocket (FFAR)

For our UH-1C and Cobra Gunships

see Flechettes - VT (Variable Time) Fuse - emails


The 2.75 inch (70mm) folding fin aerial rocket (FFAR) was fired from our UH-1C and AH1G Cobra Gunships.

In the early years the High Explosive (HE) warhead was 10 pounds. As the war progressed, the 17 pound warhead was introduced. It was attached to the same rocket motor and became the weapon of choice.

Maximum range was listed at 8000 meters, but the Centaurs generally fired at 1000 to 1600 meter range for more accuracy.

The rockets were launched from pods of 7, 19 or 24 tubes. There was one pod on each side of the helicopter, matched in size for weight and balance purposes. Rockets were generally fired in pairs for that same reason (one rocket from each side). The pilot could select how many rockets to fire using a control box in the cockpit called an Intervalometer.


The 10lb HE warheads were similar in explosive power to the WWII 75mm howitzer round and having up to a 50 meter casualty radius.

The 17lb HE warheads had similar explosive power to the 105 Howitzer artillery round in their effectiveness.

We used the 10lb White Phosphorus (WP or "Wily Pete") warhead almost exclusively for marking targets. WP is a highly efficient smoke-producing agent, burning quickly and producing an instant blanket of smoke.

FFARs The photo to the right is a pilot showing a comparison of the 10 pound and 17 pound 2.75" folding fin rockets. Introduced sometime in 1968, the new rocket had the same rocket motor as the 10 pound warhead rocket. However, because of the much heavier warhead, the flight characteristics required the use of not only "windage" correction, but super-elevation.

We used three versions of the 10 pound warhead, High Explosive (HE), White phosphorus (WP) and the Flechette (Nails). Once the newer and more devistating 17 pound warhead came out in mid 1967, we pretty much quit using the 10 pound HE.


The 10 pounder HE: M151 High-Explosive. (see diagram below) is an antipersonnel and antimaterial warhead. The bursting radius is 10 meters; however, the high velocity fragments can often increase the lethality radius in excess of 50 meters. The nose section is constructed of cast iron and threaded to receive the fuze. The base section is constructed of steel or cast iron and is threaded so that it can be attached to the rocket motor. The base section and the rocket motor are brazed together. Total weight of the loaded, unfuzed, warhead is 8.7 pounds, of which 2.3 pounds is composition B4 explosive.

The 10 pounder WP: M156 White Phosphorous/Smoke. "Willie Pete" (see diagram below) Primarily used for target marking and incendiary purposes. Similar construction to the HE warhead but contains 2.2 pounds of WP with .12-pound bursting charge of composition B. Weight of the fuzed warhead is about 9.7 pounds.

The 10 pounder Flechette: WDU (4A/A). Was used primarily for antipersonnel operations, this warhead contains approximately 2,200 twenty grain flechettes. The flechettes are released by a base-mounted, fuze-ignited (integral fuze) expulsion charge at rocket motor burnout. Fuzed weight of the flechette is 9.3 pounds.

The 17 pounder HE: M229 High-Explosive. Is an elongated version of the M151. The filler consists of 4.8 pounds of composition B4 explosive and can use the same fuzes as the M151. Its unfuzed weight is 16.4 pounds.





The VT (Variable Time) Fuse

For the 2.75 inch Folding Fin Aerial Rocket

vt fuseAlthough we always called them VT - what they actually are is Proximity Fuzes that provided an airburst about 5 meters above the ground.

Technical Data (TM 43-0001-30): This fuze is an all transistorized, continuous wave, doppler device to provide airburst characteristics. It was designed primarily for use with HE warheads for improved anti-personnel effectiveness. A super-quick impact switch serves as a backup in the event of failure of the airburst electronics. The arming mechanism is similar to that contained in the standard fuse (M423/M427) except that it has been modified to include an electric detonator as well as a battery starter assembly to initiate an electric battery. An electric detonator is assembled in the rotor. A plastic (lexan) sleeve houses the thermal battery which is located directly above the safety and arming device.

See photo one in Sam Dooling's PhotoAlbum



The Flechette Warhead

For the 2.75 inch Folding Fin Aerial Rocket


The 10 pound Flechette: WDU (4A/A). Was used primarily for antipersonnel operations. Contained approximately 2,200 twenty grain flechettes. The flechettes are released by a base-mounted, fuze-ignited (integral fuze) expulsion charge at rocket motor burnout. Fuzed weight of the flechette is 9.3 pounds.

Play the Flechette Movie








Email Discussion about Flechettes:

Bruce Powell (67-68):
I haven't yet found the writings that Tom Meeks and I did at Cobra Hall for the gunnery training program that we developed, but the 1600 meter slant range to get a football size impact area with flechettes is a strong memory for me (doesn't mean that it is right. I'll keep looking).

FlechetteInHand We need to hear from the F Troop guys (71-72) about their use of flechette rounds. I was there in 72 with a different unit (supporting the Korean Army) and flechettes were a basic load for my external Cobra stores.

Bob Graham (66-67):
The 1600 meter Range
A football field two or three. If that that is is size of area you were suppressing that's the correct range. Our targets were much more selective. For each side of and LZ or a tree line, small canyon, top of a ridge line. So your are right on. We often did not have that much area or room between the slicks and the suppressed area. Our initial. pass was the actual LZ just before the slicks touched down to stick all the little guys before touch down. The following team or second pass of a single team covered the most like prepared positions and the initial objective. Then another team would arrive for this to develop. We put a lot into the initial suppressive fires to insure a successful organization and first movements of the landed force. I did have a slick driver come stomping into my battery with a little arrow between his fingers. All excited about getting it out of his rotor blade. I asked him if it was a hot LZ. He said Yes. I asked how much fire he received, He said, none. There was silence==== then he understood. We had a cold beer.

Pat Eastes (67-68):
I flew guns my whole tour, but I'm damned if I remember ever shooting nails. Tom says we would have used them during Tet 68, but again, I sure don't remember using them. Am I alone with this CRS syndrome, or do other gun drivers not remember using flechettes?

Charlie Johnson (67-68):
I am on the same memory lane as Pat on this one: A dead end.

I flew HOGS from about August 1967 to about May 1968 and don’t recall any flechette rockets being used or tested by the Heavy Weapons Section. Ditto for the Heavy Scouts as far as my recollection goes.
I do recall seeing a flechette round being fired by one of the Cav tanks at the 1968 Ton Son Nhut war games. We were trying to line up a gun run on 3 or 4 NVA running for the woodline, running away from the Cav, when they were suddenly overtaken by a small, dark swarm almost like a swarm of bees around a bee hive and in the blink of an eye converted to a pink mist or cloud. This was one of those moments that was just plain scary, making the hair on the back of your neck stand up scary, because of the damage that one round did, even though it wasn’t aimed at us.
I recall wishing at the time we had something like that but also thinking that the Heavy Scout’s mini-guns did much the same thing to troops in the open or under light cover. Actually, the mini-guns chewed up people and scenery without regard to what kind of cover they had, going deeper into tree lines than a flechette round might be able to for example.

Tom Fleming (67-68):
One of the reasons that most of you weren’t aware of the box of flechettes in the troop ammo dump was that there was a report that had to be filled out for each one fired.  After some testing with them in early 1967 they became virtually forgotten.  In Dec 1967 about the time they were moved across the runway they were rediscovered and a couple of them tested, by whom I cant recall but they were deemed too inaccurate for the kind of gunning we were doing.

I remember a conversation about how we could load one or two in a rocket pod and not fire them if the mission was inappropriate.  One of the other considerations was that loading them would reduce the firepower available.  There considerations were also applicable to carrying white phosperious warheads..   I mistakenly presumed that someone would remember that they were available during the target rich TET and post TET period.

I witnessed the devastating effect of flechettes fired from artillery during the LZ Gold battle in early 1967.  At that time they were classified.

My comment on the use of Flechettes is based on recalled memory of comments from other Centaurs on post TET 1968 actions.  I cannot verify the accuracy of these recollections.  It was common knowledge that we had a few flechette rounds in the ammo dump and that given an opportunity to engage a massed enemy formation that the would be devastating, but the decisions post TET to use or not use were not mine.

Carl Betsill (70-71):
Concerning the use of flechetts in 71-72, history would not be complete without noting "other" uses. When the unit moved from Lai Khe in February of 72 the hocches were simple metal buildings with open bays. We quickly converted them with lumber from rocket crates into private rooms. Of course we needed nails and the flechetts canisters provided a ready source.

Flechetts also were a good subject for speculation. Since we enlisted men were usually kept in the dark about everything, rumors often replaced fact. I remember being told the red powder was an anticoagulant and that the Flechett rounds were against the Geneva Convention. There was no end to the imagination of an enlisted man!

Jack Craig (69-70): I always carried a full load of Flechettes in the outboard stores of my Cobra; 19 in each pod for a total of 38. It proved to be a far better weapon than the 17 pounders.

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20mm Automatic Cannon



Image courtesy of Linford E. Riniker

Rate of Fire—650 to 850 Rounds per Minute (Typical 750 Rounds Per Minute).

Range—3,500 Meters Area Fire and 2,000 Meters Point Fire.

Muzzle Velocity—3,200 Feet Per Second.

Ammunition—M56 HEI (High-explosive Incendiary); M53 API (Armor-piercing Incendiary)

The M35 Armament System mounted a modified M61 Vulcan 20mm Automatic Cannon designated M195. With much shorter barrels than the M61, the rate of fire for the M195 had to be drastically reduced for helicopter use to 750 shots per minute from the Vulcan's normal rate of fire of 4,000 to 6,000 shots per minute, but even at that the vibration of the weapon was tremendous.


Introduced to Vietnam in late December 1969, the M35 armament system weighed in at 1,239 pounds fully loaded with 950 rounds. The ammo was delivered to the gun from two saddle ammunition containers affixed each side of the fuselage above the skids and connected by crossover feed chutes. Due to the explosive muzzle blast from the M195, extra plating had to be installed on the left side of the aircraft to protect the wiring, flight controls and fuselage.This weapon system provided Army aviation assets a long range suppressive fire system to counter .51 caliber Machineguns and other NVA anti-aircraft systems prevalent in South Vietnam areas of operation. The Centaurs had not made use of 20mm cannons until January 1972 when they accepted delivery of AH-1G 69-16439, a Cobra that obtained near legendary status as a Super Scout since deployed in 1970.


Centaur armorers left and right,
439 crew chief center,
in October/November 1972.
Image courtesy of Michael A. Peake.

The new Cobra 439 arrived in country in late 1969, for the 3rd Squadron, 17th Cavalry operating in the Pleiku region, configured with the M35, three 7-tube rocket pods and twin 7.62mm Miniguns in the nose turret. Under the command of CW2 Dave Tela, a three-time recipient of the Distinguished Flying Cross, the gunship saw extensive service in Cambodia during May/June 1970, and remained with the 17th Cavalry in the same configuration until transferred to Troop F, 4th Air Cavalry Centaurs in 1972.

20mm3The first modification the Centaur armorers made to 439 replaced the turret’s left hand minigun, prone to persistent jamming, with the M129 40 mm grenade launcher. To maximize effectiveness against NVA armor and light vehicles, including T54 and PT76 tanks, armorers altered the high explosive incendiary ammunition load for the 20mm with an armor piercing incendiary every third round.

Image courtesy of Linford E. Riniker.


With the target rich environment diminishing by May 1972, 439 often returned with the right hand ammunition box at full capacity. From that time until the cease-fire, the aircraft flew missions with 500 rounds in the left-hand box. To compensate for the weight differential and to give the aircraft added punch, a 19-tube rocket pod replaced the 7-tube launcher mounted inboard right side.



Vietnam Choppers and Their Crews, Jonathan Bernstein/Gordon Rottman, Osprey Publishing Ltd. (2007).

Vietnam Order of Battle, Shelby L. Stanton, U. S. News Books (1986).