Dropping Bullets From a Plane

Is it safe to airdrop ammunition?

A helicopter drops relief supplies in Pakistan
A helicopter drops relief supplies in Pakistan

A helicopter delivering supplies to an Afghan National Police outpost accidentally dropped its cargo at the wrong location, a NATO spokesman acknowledged Thursday. According to a briefing given to the Afghan Parliament, the supplies—which included ammunition, rocket-propelled grenades, and food —fell into the hands of a nearby Taliban leader. Wait, is it safe to drop ammunition and grenades from the air?

Yes, if you make sure it’s not falling too fast. There shouldn’t be much risk of personal injury, since supplies aren’t usually dropped until an area is cleared of people. As a result, the biggest challenge is to ensure that the supplies themselves survive the fall. While smaller, less-fragile supplies—like individual rations of food or leaflets, for example—can be dispersed widely in a free drop, most airdrops utilize some method for reducing the delivery’s speed before it hits the ground. For a drop to be classified as “low-velocity,” the cargo must be falling at a rate of no more than 28 feet per second (about 19 mph) by the time it lands. But even higher-velocity airdrops, which fall at 70 to 90 feet per second, can include packages of ammunition.

While details about the bungled Afghanistan drop are sketchy, it is likely that the supplies weren’t released from very high above the ground. Most higher-altitude airdrops are made from airplanes, which can carry far more than a helicopter but which are far harder to get near the ground in remote locations. When helicopters are used, they often carry and deposit large cargo by hooking it as a “sling load” that hangs below the aircraft and can be lowered more gently to the ground. Sling loads can be used to haul Humvees or even other helicopters; the Boeing-made Chinook can carry up to 26,000 pounds on a single hook.

Since World War II, the most popular method of delivering supplies from high in the air has involved using parachutes that open after the cargo is released. Today, the most advanced aerial delivery methods, like the recently developed Joint Precision Airdrop System, can safely drop loads weighing several tons from as high as 25,000 feet. Using technology similar to that employed with smart bombs, the system tags cargo with GPS devices that help adjust the parachute to ensure the cargo reaches its intended destination. These drops are sometimes used in Iraq and Afghanistan, where they allow resupply convoys to stay off the road and out of the reach of IEDs and other hazards. In most cases, however, supplies are still dropped with a “dumb” parachute from lower altitudes.

To reduce the force of impact, cargo is often secured within honeycomb, a cardboardlike layer a couple of inches thick. In some humanitarian drops, blankets or ration packets have been used instead to help cushion the rest of the delivery. Before items like munitions are cleared for aerial delivery, they are tested in repeated drops at places like the Yuma Proving Ground in Arizona.

In the case of humanitarian relief, the biggest danger associated with airdrops often comes in the chaos that can occur when the food and medicine finally arrive. When the World Food Program is forced to airdrop, it creates cordoned-off zones to collect the supplies. But in India last year, at least three people sustained injuries after falling from their roofs while attempting to receive food packets dropped from Indian Air Force helicopters. And during the initial phases of the 2003 invasion of Iraq, the United Nations warned that children might easily mistake “bomblets” dropped from airplanes with the similarly colored food rations distributed by coalition forces on the ground.

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