Beartrap: The Best Way To Land A Big Helicopter On A Small Ship At Sea

Today, navies around the world use an ingenious system to

land

helicopter

s on the rolling deck of a

ship

at sea. It enabled the powerful

helicopter

-destroyer combination that has become the dominant form of anti-submarine warfare at sea. It is the "helicopter rapid safety and descent device", or more commonly known as the Beartrap. The experience with HMCS Labrador demonstrated that helicopters could be operated by

ship

s at sea. During construction, a flight deck and hangar were installed to allow storage of its Piasecki HUP-3 and Bell HTL helicopters. Watch my video about HMCS Labrador and the search for her through the Northwest Passage for more information.

They flew from the deck when conditions permitted and the flight deck was comparable to one on the ground. In case of bad weather or high seas, the helicopters were grounded. They had no effective way to secure the heavy helicopters to the deck or move them to the hangar without significant human effort. While the Labrador demonstrated that helicopters could operate from ships at sea, she also demonstrated that a more effective and safer technique needed to be developed. The Royal Canadian Navy was seeking to expand its anti-submarine warfare capabilities against the new, faster Soviet nuclear-powered submarines. Their destroyers were not fast enough to guarantee an interception, so ways to extend their range were explored.

The RCN had two simultaneous programs to address this problem: hydrofoils and helicopters. The RCN had been involved in hydrofoil research since the Second World War, culminating with the incredible HMCS Bras D'Or. Super-fast offshore hydrofoils held promise, but even before Bras D'Or began testing they were already in danger. Ultimately, hydrofoils were abandoned in favor of the use of shipboard helicopters. Check out the video I made on the Bras D'Or for more details. The next step was to try to

land

a helicopter on a ship the size of a destroyer at sea. It was a bold move. Landing large helicopters on a

small

ship had never before been attempted.

Previously, helicopters were carried on aircraft carriers such as HMCS Magnificent and HMCS Bonaventure, but the RCN was not interested in operating a fleet as large as that. Instead, they wanted to combine the efficiency of a destroyer with the capabilities of a helicopter. This would help reduce costs and increase flexibility, as a fleet of many helicopter-destroyer combos could patrol a larger expanse of ocean than one or two large aircraft carriers. The Royal Canadian Navy Experimental Squadron VX 10, based at Shearwater, took on the task of developing a helicopter landing and handling system for ships. They had worked in Labrador since 1954 and learned many valuable lessons.

Early RCN helicopters, such as the HUP-3 and HTV, were not suitable for sustained anti-submarine warfare operations, but proved very useful in the Arctic. Now the RCN focused on acquiring a more capable platform. This came in the form of the Sikorsky HO4S-3. These had diving sonars and legs to remain aloft for a significant period of time. The problem was that they were much larger and heavier than the ones they had previously worked with. To gain more experience, a

small

flight deck was installed on the frigate HMCS Buckingham. The successful landings were made with an HO4S-3, mirroring the success of the Labrador.

A second flight deck was installed on the smaller destroyer escort HMCS Ottawa. A larger Sikorsky S-58 was used in these tests and again proved successful. This led to the conclusion that the destroyer-helicopter combination was a viable concept. It was decided that the RCN's new class of destroyer, called the St. Laurent class, would be modified to employ helicopters in an anti-submarine role as its primary weapons system. However, two things needed to be addressed. First, the helicopters used in the tests lacked the all-weather capabilities necessary for effective anti-submarine warfare operations. Second, they needed a way to land and move a large helicopter over the deck of a rocking, rocking ship.

To respond to the first need, RCN acquired the new Sikorsky CH-124 Sea King. He was much more capable than any type previously employed. It could operate in any weather and could carry systems to track and attack submarines. Watch my upcoming video on the Sea King to learn more about her long history with the RCN. The Sea King is heavy, with a gross weight of 8,449 kg (18,626 lb). This made handling it on a moving flight deck almost impossible without some form of assistance. The landings were comparatively easy compared to trying to get the helicopter into its hangar. Once the problem was defined, Fairey Aviation in Dartmouth, Nova Scotia, was contracted under the supervision of the RCN.

What they came up with was called the Rapid Security and Helicopter Transport Device, also known as the “Bear Trap.” The system was made up of several parts. A probe and cable assembly, a control console, winch, power unit, anchoring system, rails and shock absorbers. The first unit was installed on HMCS Assiniboine during her 1962-63 conversion, which also saw the addition of roll stabilizer fins, a landing platform, fueling facilities and a hangar. Probably the

best

way to explain how the entire system works is to go over what a typical landing looks like. To begin the process, the landing helicopter will approach from the stern and match the ship's forward speed, maintaining a hover just behind and to the left of the landing platform.

This allows the pilot to see the deck and initiate radio communications with the landing control officer aboard the ship. The pilot then aligns the "rear line" markings on the deck. They are called butt lines because they align your butt directly over them. A small messenger probe is then lowered from beneath the helicopter. A crew member aboard the boat then takes the probe and attaches it to the trailing cable leading from the center of the trap. The cables are then retracted into the helicopter and secured at its center of mass. The pilot increases power as the winch operator pulls the cable to achieve a "hover tension." This allows the helicopter to apply tension equal to its gross weight, making it much more stable.

Tension is maintained by a complicated system of winch controls and shock absorbers. The LCO retracts the cable and the helicopter descends to the deck, guiding its probe into the jaws of the trap. When safe, the trap closes around the probe, securing the helicopter to the pitch and roll platform. The system can easily handle 30-degree roll and 8-degree pitch. Once secured in the trap, a tail probe is connected and the engine is shut down. Following this, it is now safe to fold back the rotors and tail pylon and move the helicopter across the flight deck to the hangar.

Tracks on the deck allow the bear trap to be moved independently of the movement of the boat. Takeoffs were a little less complicated. The helicopter is moved to the flight deck using the trap and rails. Once in position, the engines are started and brought to full idle. The tail probe is retracted and the trap is released. The pilot then applies full power and takes off from the deck when the LCO senses that there is a sufficient pause in the ship's motion. They then hold the cursor just above the platform to make sure they don't drag any cables.

Once everything is clear, they walk away and begin their mission. Day trials began in late 1963 and continued until mid-1964 using the new Sea Kings. Night tests and bad weather tests followed shortly after, which were also successful. The other 6 St. Laurent-class destroyers were fitted with their landing systems and aviation facilities during their DDH refits. All of these were completed by 1965. By April 1967, the entire Beartrap system was fully operational. The system would later be installed on all newly built frigates and destroyers serving in the Canadian fleet to this day. Other navies were impressed with the Canadian achievement and wanted a similar system for themselves.

While their systems differed in some minor details and were built by different manufacturers, many other navies, including those of the US, UK, Japan and Australia, were early adopters of Beartrap. Since then, almost all Navies that operate helicopters from small ships use the basic Beartrap concept in some way. The exception is the harpoon and grill method, but it lacks much of the function and safety of the Canadian system. It really is the

best

way to solve the problem, which is why the solution was widely adopted. In fact, Beartrap is so successful that it hasn't undergone any major redesigns or changes since it was introduced over 60 years ago.

Advances have been made in how the probe is handled or, in some cases, not handled, and how focusing is performed and controlled, but the principle of core probe and trap remains the same. This device may be little known to the public, but it represents one of the greatest contributions Canada has ever made to naval aviation and ushered in the era of helicopters at sea.