HOV­ER­ING with IN­TENT

Boating NZ - - Feature - WORDS AND PHO­TOG­RA­PHY BY LIND­SAY WRIGHT

Most of us pass through Auck­land Air­port at some stage in our lives, where gi­ant air­lin­ers line up on a run­way stick­ing into the Manukau Har­bour like an ex­tended fore­fin­ger. Few think about the peo­ple tasked with pick­ing up sur­vivors if it all goes wrong.

De­pend­ing on the state of the tide, the D run­way is sur­rounded by a quag­mire of mud and sand flats, thinly dis­guised, at high tide, by tur­bid brown wa­ter. But every year more than two mil­lion peo­ple pass over­head; sit­ting in that par­lous state be­tween be­ing aloft and aground.

Few peo­ple no­tice the clus­ter of build­ings on the fore­shore or, if they do, don’t give them a thought, but it’s head­quar­ters for the 60 or so per­son­nel of the Air­port Emer­gency Ser­vices (AES) who main­tain a 24/7 watch on op­er­a­tions.

The air­port fire­fight­ers are, like their ur­ban coun­ter­parts, con­stantly on alert for po­ten­tial dan­ger and highly trained to cope with it. But, in line with the spe­cialised na­ture of their lo­ca­tion, they have a two ex­tra tools.

These are the two lime-green Grif­fon hov­er­craft slumped on de­flated air skirts in the fenced-off yard on the har­bour shore.

“This one [H1] is 25 years old,” says se­nior fire­fighter and hov­er­craft trainer, Richard Gowdy. Its lime fuse­lage looks like new.

“One of the ad­van­tages hov­er­crafts have over he­li­copters is that you don’t need spe­cial­ist tech­ni­cians to main­tain them.

He un­latches an alu­minium cover. “Look – a plain old Deutz air-cooled V8 diesel – just about any me­chan­i­cal­ly­minded per­son can look af­ter it.”

A belt-driven com­pres­sor off the front of the en­gine “gen­er­ates the vol­ume of lift-air that’s main­tained by the flex­i­ble skirt at a higher pres­sure than the am­bi­ent at­mo­spheric pres­sure,” the Grif­fon web­site ex­plains. “They can travel over al­most any non-por­ous sur­face – ice, de­bris, rock, sand.”

An­other belt takes power from the back of the en­gine to drive the two-me­tre di­am­e­ter pro­pel­ler and an elec­tro­hy­draulic pump pushes the hy­draulic oil used to ad­just pro­pel­ler pitch. “The de­fault po­si­tion is full pitch – so you al­ways have enough drive to get you back to home base if any­thing fails,” says Richard.

Not much of this is new tech­nol­ogy – Sir Christo­pher Cock­erell con­ceived the idea over 50 years ago. Hov­er­craft have been used for years to sup­ply far-flung out­posts in the Cana­dian Arc­tic over thin ice dur­ing their frozen win­ters.

“She’s saved a few lives, this old girl,” Richard pats the alu­minium hull af­fec­tion­ately. The AES hov­er­craft are called on by po­lice, Coast­guard and SAR au­thor­i­ties in Manukau Har­bour and have res­cued kayak­ers, pad­dle board­ers, dis­tressed fish­ers and oth­ers.

“They’re per­fect for res­cue work,” he ex­plains. “You can go right up to a per­son or ves­sel, de­flate the skirts and set­tle be­side them like any boat with ex­tra low free­board. They don’t leave any wake or wash – and you can go al­most any­where. Some­times we take one down to Huia for a cup of cof­fee or a feed of fish and chips – just run it up on the beach and walk across the road.”

Un­der­neath, the 2mm ma­rine al­loy hull plat­ing is

slightly con­cave with buoy­ancy tanks run­ning down each side to stiffen the struc­ture and pro­vide fas­ten­ing points for the rub­ber skirts.

Richard ush­ers us aboard H2, a five-year old Grif­fon 2000TD, pow­ered by a 440hp, liq­uid-cooled Deutz V6 diesel, and dis­trib­utes life­jack­ets with his safety brief­ing. “If we turn over,” he points out, “we won’t be able to get out of the gull­wing doors – so take this fire axe and smash the win­dows.”

The hov­er­craft are un­der Mar­itime New Zealand sur­vey for 15 pas­sen­gers but there are six 30-pas­sen­ger life rafts fas­tened around the side decks and, “if we had to – we’d load them to the max,” says Richard. “If a plane dumped in the mud or shal­low wa­ter – our role would be to trans­fer sur­vivors to the boats wait­ing out in deep wa­ter.”

Each shift of air­port fire­fight­ers has four skip­pers who hold

Re­stricted Lim­its Launch Mas­ter (RLL) tick­ets. They carry a min­i­mum crew of three; helms­man, skip­per and trainee/ deck­hand. They aim for a five-minute de­ploy­ment dead­line from an alarm be­ing sounded to on-the-wa­ter readi­ness.

It’s a cold, breezy day and the latte- coloured wa­ter looks most un­invit­ing. “Our op­er­at­ing pa­ram­e­ters are 20 knots – gust­ing 30 – of wind. We call the con­trol tower and they tell us what we’ve got.”

Any en­gine or belt noise from the Deutz is drowned out by pro­pel­ler roar as the bags in­flate and the hov­er­craft jerk­ily rises like a camel groan­ing to its feet. It glides to­wards the wa­ter. Well – where the wa­ter should be at high tide – and bar­rels down the launch­ing ramp, slightly down by the nose with a sen­sa­tion that is half float­ing, half fly­ing.

“One dif­fer­ence from a boat is these foot ped­als,” Richard points out. “They con­trol the skirt ma­trix by push­ing or pulling a stain­less rod which al­ters the shape of the skirts to en­able bet­ter han­dling and cor­ner­ing. And, of course, you have to al­ter pro­pel­ler pitch in sync with what­ever ma­noeu­vre you want to do.”

They can travel over al­most any non­porous sur­face – ice, de­bris, rock, sand.”

Three small rud­ders are mounted side by side in the pro­pel­ler wash and en­able the hov­er­craft to vir­tu­ally spin on its axis at speed. With no boat in the wa­ter, or fric­tion on the skirts, the hov­er­craft ro­tates ef­fort­lessly, the panorama flash­ing past the win­dows is the only in­di­ca­tion that we’re in a two-tonne spin­ning top.

The Grif­fon web­site cau­tions against op­er­at­ing the hov­er­craft on steep slopes. “All hov­er­craft are sus­cep­ti­ble to side-slip­ping,” it says un­der­stat­edly.

“Driv­ing them is seat of the pants stuff – some peo­ple get the feel for it quite quickly – oth­ers never do. These things are all about cen­tre of grav­ity – you have to be mind­ful of it all the time – it’s all about feel,” says Richard.

Any of the air­port crash re­spon­ders who show in­ter­est – and a de­gree of com­pe­tency – can ask to be trained as hov­er­craft op­er­a­tors.

An­other point of dif­fer­ence from a con­ven­tional ves­sel is the bal­last/ fuel tanks which hold 440 litres of fuel at ei­ther end of the boat – sorry, hov­er­craft. A pump trans­fers the fuel from tank to tank in sec­onds through 50mm pipework. Counter-in­tu­itively, says Richard, they go bet­ter down­wind when the weight is in the for­ward tank.

At about 20-25 knots we scoot across the sand bars and over the channels, ig­nor­ing mark­ers and buoys, like school­boys splash­ing through pud­dles af­ter school. The wheel­house win­dows are quickly covered in a smear of muddy wa­ter be­ing pushed around by the three wipers.

In op­er­a­tional mode – the skip­per would sit in the right-hand seat to keep an eye on the radar and plot­ter.

The launch­ing ramp is dead down­wind. “That’s about the worst an­gle of at­tack for a hov­er­craft – the wind up your back­side pushes you all over the place.” Gauges flicker and he hits switches to trans­fer bal­last, his feet firmly pres­sur­ing the skirt con­trol ped­als. The ramp lines up with the craft’s blunt nose and we run straight up it to set­tle in the car park. Easy as that.

At 1800rpm, the Deutz uses about 45 litres per hour of fuel. Con­sump­tion climbs to 75 litres at 2000 rpm and dou­bles to 90 litres at 2100 rpm. “We try to run them at about 1500rpm which is eco­nom­i­cal cruis­ing and less drag on the skirts,” says Richard.

“The skirts last for years – but we only get 4-6 months out of the fin­gers (the rub­berised strips on the un­der­side of the skirts that make con­tact with the ground).”

Op­er­a­tional speed over wa­ter is 35 knots, or 15 knots on firm ground, and they can carry a 2200kg pay­load. “They’re the per­fect tool for the job re­ally,” Richard says.

Ready and wait­ing.

BELOW H1 is sur­veyed for 15 pas­sen­gers but she car­ries six 30-per­son life rafts.

BOT­TOM The op­er­a­tional end of the hov­er­craft, and op­po­site, right, the 440hp Deutz V6 diesel en­gine.

LEFT Plenty of space to ac­com­mo­date pas­sen­gers un­lucky enough to end up in the drink. BELOW Propul­sion comes from a five­bladed, two-me­tre pro­pel­ler.

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