Bad weather shipboard helicopter operations could almost be the poster child for sensory overload.
Philip Smart | Adelaide
By definition, a deck landing could mean manoeuvring around 10 tonnes of airframe, fuel, weapons and people to within metres of a ship’s superstructure to land on a helideck that is itself pitching and rolling with the vessel.
Eddy currents and turbulence from a vessel’s superstructure can push a helicopter around at the low forward speeds and hover required for a safe approach, while operations in any kind of weather will ensure the pilot is also coping with reduced visibility through a cockpit windscreen driven with sea spray and rain.
In the last few seconds, the ship’s moving structure can fill the pilot’s vision, robbing them of any stable point to sense the helicopter’s own movement at a time when the danger of a rotating rotor blade contacting the ship is at its greatest. The complexities involved have so far defied attempts to automate the process, so every landing is a visual, hands and feet arrival.
“The ship itself can present as many challenges to safe flying as the airframe”
And even a successful landing doesn’t guarantee safety. With the helicopter deckbound it rolls and pitches with the ship, which in extreme cases can see the aircraft topple over or slide down the deck on its undercarriage.
Since 2004, Adelaide company Prism Defence has provided the world’s defence forces with the critical operational testing and guidance needed to know and cope with the limits for each combination of helicopter and ship.
Prism has conducted more than a dozen such trials for the navies of Oman, Malta, NZ, Denmark and Sweden, including integrating the new Royal Danish Navy MH60R Seahawk Romeo across the whole of the Danish Navy’s fleet of helicopter-capable ships.
Through a combination of in-house computer modelling and practical testing with instrumented helicopters and vessels, the Prism team delivers a package of data and limit information, including a set of Shipboard Helicopter Operating Limit (SHOL) visual guides called SHOL plates, the shipboard helicopter equivalent of an airline pilot’s airport approach plate.
“We develop a whole book of SHOL plates for different aircraft operational states that you might want to perform,” Prism’s James Forrest said to ADM. “So there’ll be a SHOL plate which will govern launch and recovery, there will be a SHOL plate which will govern night landings, and a SHOL plate which will govern one-engine-inoperative landings.”
The SHOL plates take in to account the ship and helicopter operating parameters, including practical points such as the fact that helicopter pilots fly from the right-hand seat, so most ship approaches are conducted from the left side to maximise visibility. And unlike aircraft carriers, smaller vessels don’t necessarily turn in to wind for helicopter operations. The plates aren’t just about safety, but also about ensuring the most effective helicopter operations in line with the ship’s own requirements.
“You’ve got maybe a 60-degree arc in which you can conduct operations easily. You go much outside that arc and then you can really restrict what you can do.
“It’s about expanding the envelope and allowing them to operate in as many conditions as they can. Because it’s not always as simple as saying give a red two-zero which might be the optimal. There might be an island in the way, they might be in a flotilla. There’s various reasons why sometimes a ship has to maintain its course and speed, so making that envelope as big as possible everywhere is really the name of the game.”
Reliable data
Creating reliable data is very much a hands-on operation. Prism test pilots investigate the ship and helicopter type to be integrated long before operational trials begin. The practical phase includes attaching their own instrumentation to the test helicopter and vessel before flying an incrementally more difficult set of test parameters. Ironically, this sometimes means flying is scrubbed because the weather is too good to gain useful test points.
The ship itself can present as many challenges to safe flying as the airframe.
“There’s sometimes been a disconnect between the ship designers and the aviation operations side of things,” Forrest said. “Even with things like anemometer (wind speed measuring device) placements. We need to know accurately what the relative wind speed is. But they’ll put them behind a mast, or they’ll put them really close to a piece of superstructure so you get this air bending around and speeding up, and turbulence. So if the ship driver’s there and he thinks he’s got a red two-zero at 30-knots, in reality, what the aircraft is seeing behind is nothing like that.”
Shipboard Helicopter Operating Limit (SHOL) visual guides called SHOL plates are the shipboard helicopter equivalent of an airline pilot's airport approach plate. Credit: Prism Defence
But Forrest has also seen modern ship design starting to incorporate helicopter-friendly design changes, including smoothing off superstructure corners to reduce wind turbulence, adding gyro-stabilised horizontal bars on the superstructure to provide an artificial horizon for incoming helicopters and providing deck lighting that helps guide a pilot without temporarily blinding them or creating false visual cues.
With thousands of hours of test and calculation behind it, Prism is acknowledged as one of the world’s foremost helicopter-ship integration specialists, including now being partnered with Airbus’s Defence and Space division in development of its DeckLander automated landing system.
Prism has also expanded its services beyond first of class flight trials and operational limits testing to include consultancy on helicopter-related ship design, airflow trials and training for embarked aircrew, deck crews and ship officers. With increasing numbers of patrol and military vessels sporting helidecks the company’s experience is expected to be in great demand.
“Ship and aircraft operators are showing an increasing need for ship-based helicopter capabilities. For the military, the helicopter is often regarded as a force multiplier, by extending the surveillance and strike capabilities of the ship’s weapon system. Other roles such as medical evacuation, personnel transport, and supply support are common to both military and civil operators.
“Prism personnel have first-hand knowledge flying helicopters and commanding ships and therefore have a thorough understanding of the complexity of the task, and the operational imperatives.”
This article first appeared in the March 2017 edition of ADM.