The red and yellow helicopter, call-sign G-ORKY, swoops in low over Braeriach, high in the Cairngorms.

Alan Wright stands and watches it approach. Beneath the helicopter, at the end of a cable, is part of a cabin complex in which he and his four colleagues will spend the next three months.

The chopper hovers over the spot. Workmen on the ground quickly detach the cabin from the cable and Angus Gibson takes off again, headed for a clearing at Rothiemurchus, a few minutes' flight away. The pilot has a busy day ahead of him.

By the end of the day, a four-cabin complex will have been airlifted from Rothiemurchus and assembled on site at Braeriach, at 1296m the third-highest mountain in the British Isles, behind Ben Nevis and Ben Macdui. The Cairngorms National Park is itself Britain's largest. It covers an area equivalent to a sixth of Scotland, and has five of the country's tallest peaks.

The thin, hardy, green steel cabins include a kitchen/dining area, a bunkroom, a toilet and a store/drying room. A few feet away lies a series of external, waterproof, vermin-proof containers for food, and waste storage, and the batteries and generators that will give the workers – who are repairing a two-mile stretch of badly eroded mountain path – heat and light. To the untutored eye, the units seem bare and thin. But they are not quite as they seem. They have to be warm and effectively ventilated, and strong enough to withstand the 120mph winds that are often a feature of life here. If they were neither robust nor warm, they wouldn't be at the clearing, waiting to be winched up.

This part of the Cairngorms is beautiful but challenging. Access is not easy. The revelant entry in The Munros: A WalkHighlands Guide, says the route that takes in Braeriach, Cairn Toul, Sgor an Lochain Uaine and the Devil's Point is "extremely long, remote and exposed to severe weather, with very difficult navigation on the plateaux in poor visibility". Having the workers walk in and walk out each day – a four-hour round trip – wasn't an option. Hence the cabins, or remote accommodation system, to use the official name.

For the reason why Wright and his colleagues will live in this area from now until the end of August, you need do no more than look at the footpaths that run like jagged scars across the landscape. Every year, more than 1.4 million people come to the park on foot, or on bike. That means a hell of a lot of wear and tear on the footpaths. If you think the remotest paths escape such attention, think again: they can still register 12,000 visitors every year.

The effect of so many feet, coupled with the harsh climate and fragile habitat, has been to ensure a profound degree of erosion. One particular path in the Cairngorms has become so wide with overuse that it can be seen from the A9.

In response, the four-year, £2.1 million Cairngorm Mountain Heritage Project has been repairing and enhancing no fewer than 17 eroded footpaths on the Abernethy, Cairngorm, Rothiemurchus and Glenfeshie estates. Almost 60 miles worth, all told. Some of the paths date back to the middle ages.

Funding for the project has come from sources as diverse as the Heritage Lottery Fund (£720,000), the European Regional Development Fund (£722,000) and agencies including the Cairngorms National Park Authority, Scottish Natural Heritage and the RSPB.

But donations from the public, including Herald readers, are now being sought for a Mountain Path Appeal.

"When we're all done and dusted," says Dougie Baird, chief executive of the Cairngorm Outdoor Access Trust, which is managing the project, "we need to ensure the paths are maintained so that they don't fall into disrepair again. The thought behind the appeal is, if we can start raising a comparatively small amount of money – £10,000, £20,000, £30,000 a year – we can continue to look after the paths.

"If we don't maintain them the paths will be all right for two or three years but they'll begin to deteriorate, and the more they deteriorate, the further you get into a vicious cycle.

"If you're driving through Pitlochry and look up at Beinn a'Glo, you'll see a really obvious path up there. This is the difficulty: once the path gets damaged and horrible to walk on, people walk on the next little bit, and the path just gets wider and wider, and the problem gets worse and worse."

But a little can go a long way. "A single donation of £30," adds Baird, "would mean than more than 100 metres of mountain path can be maintained."

The work is being carried out by Wright and his colleagues Stuart Taggart and Julian Digby, from Cairngorm Wilderness Contracts, plus trainees Robert McFarlane and Alex Fishwick. "Alan, Stuart and Julian came through the training scheme in 2011 and set up the company afterwards, and they've been awarded lots of contracts," says Baird. "They know what they're doing."

Wright, who is 30, acknowledges that the weather can change quickly here. "The sun can be shining, like it is at the moment, and suddenly you can have winds coming in at you. That's one of the nastiest things about being up here: you can see the weather coming from a long way off.

"You can be sitting there, having your piece, and you can look up and see the weather coming in from 30 miles away and there's nothing you can do about it."

But the setting is absolutely stunning: from the peak "you can see all the way out to the Moray Firth, and all the mountains all around - the Moray Firth must be at least 40 miles away".

As far as Braeriach's path is concerned, Wright says they are hoping to complete about 10 metres a day. "The job is very technical for the first 150 metres – that's the real problem area, it'll be hard-going for that bit, but it'll get slightly more general as it goes up towards the top."

It's a tough, skilled job. The workers build the paths using aggregate and stone they scavenge from the mountainside. They repair drainage channels and have to landscape the paths sensitively, so they look natural.

What sort of shift patterns apply here?

"We're looking to do five or six days on and a couple off. A couple of the guys are going to do nine on and four or five off. We're planning being out of the cabin at half seven [in the morning], be on site for eight, and work through until six or half past. Ten or 11-hour shifts. It can take its toll after a week; everyone will be in need of their days off."

A couple of days later, I speak to Wright again. How are things going?

"Everything's set up in the cabin, everything's plumbed in and ready to go," he says. They even have a flat-screen TV, "although we're having a bit of difficulty getting a signal, though we can play DVDs through it". One of the other men has a guitar, which will probably arrive in due course.

There are substantial supplies of food, as you would expect. Fresh meat has just been brought up on the day we phone; that night's dinner will be haggis, neeps and tatties, with stew the following night.

"There's a few crates of beer in there as well," Wright adds. "One of the cans of Guinness just got punctured, so I'll stick that in the stew tomorrow night." n

To donate, see the leaflet enclosed with today's paper. Visit www.cairngormsoutdooraccess trust.org.uk.