Safer landings at sea

The US Navy is developing new technology that allows helicopter pilots to land on moving ships in challenging conditions with greater safety, speed and ease. 

Over the past ten years the US Navy and US Marine Corps have suffered 16 major helicopter accidents resulting in a total of 36 deaths — a sobering statistic that highlights the dangers that still exist in trying to land rotary aircraft in degraded environmental conditions. 

While specially-trained navy helicopter pilots can routinely land on ships in relatively rough seas, the operations can be compromised or abandoned due to excessive rolling or pitching, high winds, poor visibility, and even air turbulence coming off the vessel’s superstructure. 

Beartrap breakthrough

In the late 1960s, the Royal Canadian Navy developed the ‘beartrap’ haul down device which, to this day, allows helicopters to land on smaller naval vessels, such as frigates and destroyers, while the vessels are rolling up to 30 degrees and pitching up to nine degrees. 

Copied in various forms by most other navies, the beartrap uses a cable lowered from the helicopter that is attached to the ship’s flight deck via a hydraulic tensioning system. When the pilot and ship’s landing crew feel that the motions of both the aircraft and vessel are relatively stable and synchronised, the pilot reduces the aircraft’s vertical power as the cable’s tension is increased — pulling the helicopter swiftly down onto the deck. The cable is instantly secured into a snare mechanism that can then move the aircraft into a hangar, if required, along a rail track. Advanced modern versions of the beartrap now use lasers to monitor the exact position of the helicopter relative to the ship throughout the operation.

Night vision

Naval helicopter pilots also now use NVGs (night vision goggles) — binocular devices mounted onto their helmets that allow them to look through the goggles to outside the cockpit or below the goggles to their flight instrumentation. However, while NVGs provide an increase in the quality of visual information compared to unaided night vision, the vision they provide is monochromatic, with a limited field of view, and much reduced visual acuity.  

To solve these problems, the US Naval Air Warfare Center has developed a new system — ASGaRD (Adaptive Shipboard Guidance and Recovery Display) — which, it says, will allow rotary pilots to perform ship landings that would never previously have been considered. 

Credit: US Navy/Flickr

Simulator trials

“Landing on a cruiser or destroyer at night or in low visibility is the hardest thing I ever have to do — but ASGaRD allows me to do it easier, faster and safer,” explains US Navy helicopter test pilot Lt. McMillan Hastings, who is helping trial the new system via simulator exercises.  

“ASGaRD uses special cockpit displays to provide the pilot with clear visual cues to assist with the landing, without interfering with the pilot’s own control of the flight — and with a great deal less conversation amongst the aircraft’s crew during the operation. It also helps give the pilot a better sense of the environment so they can better feel how they are flying. 

“That helps with decelerating from the higher approach speed to getting into the hover over the ship, and then coming down safely from altitude and onto the ship’s flight deck.” 

“The system also adjusts for the ship’s motion, providing the pilot with an indication as to when it’s safe to land,” adds aerospace engineer Jacques Hoffler. “Yet it doesn’t touch the flight controls or the flying characteristics in any way, which is still completely entirely up to the pilot. It does, though, provide clear guidance on how to control the aircraft.” 

Dennis O’Neill is a freelance journalist specialising in maritime