Network Rail is a multi-million pound operation which spends a lot of money on equipment to maintain the railway infrastructure. It operates everything from Land Rovers to high-output track-laying trains, with a plethora of complicated and specialised plant in between.

Even so, the fact that Network Rail also has its own helicopter, with an operating cost of around £1,300 per hour, is perhaps a bit of a surprise. How can it contribute to the cost-effective maintenance of Britain’s rail network?

The answer is simple, and perhaps surprising. Not only does G-NTWK earn its living, it does so all day, every day. It is equipped to inspect a variety of lineside structures and its ability to travel at speed over any terrain means that it is very effective indeed.

Air Operations is a small department. Manager Wendy Welsh reports directly to Steve Featherstone, Network Rail’s Director of Maintenance. Two pilots and two observers report to her – and that’s it. There are a couple of relief pilots and observers as well, but otherwise its one of Network Rail’s smallest units.

Two Squirrels?

The aircraft is a Eurocopter AS355 Twin Squirrel, built in France. Network Rail’s is leased from PDG Helicopters who also supply the experienced pilots and arrange all the servicing. As a twin-engined machine, it is allowed to operate over cities where a lot of its work is carried out.

It has no fixed base. Servicing takes place at Cumbernauld in Scotland or near Wolverhampton, but the helicopter spends its nights at airfields all over the country – and its crew use a lot of hotels! But, in doing so, they cover a lot of ground.

So what is it that a helicopter can do that a cheaper, ground-based crew can’t? The secret is in the instrument pod hung under its nose. Designed and built by FLIR Systems it contains three cameras: one is a TV camera with a standard zoom, the second has a super telephoto zoom to pick out smaller details, whilst the third benefits from an infrared imaging unit and three levels of zoom.

It was the thermal imaging capability that Network Rail chose to demonstrate to the rail engineer recently. On a damp day, we met up with pilot David Blane and observer Sean Leahy just outside Coventry and, after the obligatory safety briefing, we were soon off to fly over Nuneaton Station.

While David hovered at 1,000 feet, Sean demonstrated the capabilities of the two video cameras. From a wide view of the area, he was able to tighten into a close-up of the four-foot, filling the monitor screen in front of him. The level of detail was impressive and the video was being recorded for later study if necessary.


The observer controls the cameras using a remote console and monitor screen.

Point heaters

Then we were shown what we had really come to see. The signaller had turned on all the point heaters in the area. Of course, on the normal video there was nothing visible. However, switching to the infrared camera, the glowing lines of the heated rails stood out. Sean demonstrated how he could check half-a-dozen points at one time by a simple glance at the screen. Zooming in, the twin bright lines on one particular set of points became clear.

He told us that any malfunction in a heater would show up as a break in those lines with either one leg of the points being dark (and therefore cold) or at least exhibiting a shorter line than the other.

If that happened, he showed how he could tighten the shot even further and, from a thousand feet overhead, read the number of the points in question so the fault could be reported to the local maintenance team.

In 20 minutes over Nuneaton, in the middle of a working day and without disrupting train movements, half-a-dozen sets of point heaters had been inspected.

Compare the costs involved – around £1,000 – with the logistical challenges and financial implications of sending crews out to inspect each switch individually, probably at night with a possession in place. We started to understand how the helicopter’s cost justified itself.

Booster boxes

On the way back to our departure point at Network Rail’s Westwood facility, Sean gave us another example. They had recently examined all the booster boxes in Scotland. There are over 800 of them and to despatch a maintenance team to each one in a Land Rover costs around £1,500.

From the air, Sean had inspected all of them, checked their external condition for paint flaking and rust, read the oil level off the gauge on the box and used the infrared camera to check for any excess heat which could indicate a potential electrical breakdown. All this was done in a week at an estimated cost of £75 a box!

There are more mundane inspections too. Last year there was an increase in the incidence of cows escaping from farmers’ fields onto the track. Network Rail’s Twin Squirrel was able to fly along affected sections at around 120mph, inspecting fences on both sides whilst recording the camera feeds.

Potential weak spots were identified, both in terms of the fences’ condition and the number of cows being kept close to the line. This gave ground-based teams the information they needed to go and strengthen the railway’s defences.


Cable theft is another active issue for the team. Although statistically a thief would have to be very unlucky to find the helicopter overhead just as he was committing his crime, the air support team can spot concealed access points and even evidence of rat runs where thieves, graffitists and other miscreants make their way over railway property.

So whether it is inspecting equipment or safeguarding property, there are many ways in which Network Rail’s helicopter can save time and money, and even do inspections that would otherwise be impossible.

Many thanks to Steve Featherstone, Wendy Welsh and their team for allowing us to see the unit in action.