Booms can cause injuries directly, sweep people overboard, and their associated hardware and lines represent tripping hazards. On larger boats, sailors tend to stand on the boom to perform sail maintenance and install or take off sail covers. Falls from the boom onto the deck below occur. Even when stationary, booms represent a hazard since on most boats there is insufficient headroom to walk below them without ducking. According to a German study, "boom strikes were the most common cause of sailing injury overall". When boom injuries occur far from shore they can require expensive rescues. In 2010 the US Coast Guard and Air National Guard utilized a Lockheed C-130 Hercules aircraft to rescue a man from 1400 miles off the Mexican coast. Deaths and injuries can occur on boats operating upon lakes and coastal waters. As a precaution, any sailboat with a low boom should mandate use of life jackets, and ensure others know how to obtain assistance and operate the craft. In Boston a sailor knocked overboard by the boom died in full sight of the land and other boats and the person left aboard didn't know how to use the radio. New boat designs to lower boom risks To address the dangers associated with the boom, some designers have raised the boom higher off the deck or applied padding. However, these raise the center of gravity and increase the chances of capsizing and turtling. Some designers have addressed the issue by eliminating the boom completely. Classic types of sail like the square rig or the standing lugsail have always worked without booms. Modern alternatives without a boom are the mast aft rig. Other boom uses On an open cockpit sailboat at a mooring, a tarpaulin may be run over the boom and tied to the rails to form a tent over the cockpit. In certain situations on larger boats, the boom can be used as a crane to help lift heavy items like a dinghy aboard. Other boom types Flexible boom When the foot of a sail is attached along its whole length to a boom, the stiffness of the boom tends to hold the lower part of the sail flat. However, the greatest aerodynamic efficiency of the sail is created when the sail is allowed to curve into an airfoil-like shape. A flexible boom bends with the sail to create this greater efficiency. Park Avenue boom