ATC is 100

The world’s first civil aerodrome control tower was opened 100 years ago this month at London’s Croydon airport

Early in 1920 the UK Air Ministry decided that, with an average of 12 air movements a day, the air traffic at London’s main airport – Croydon – needed organising.

The ministry had no template for such a task, but issued a specification for a building they believed would do the job. It was to be called an aerodrome control tower, and the working part of it was to be “15ft above ground level, with large windows to be placed on all four walls”.

Radio communication was already in use, but even primitive radar would not be developed for another 20 years.

CATOs in radio communication with aircraft. Picture taken 1927

Radio direction-finding, however, provided the Civil Aviation Traffic Officers (CATOs) with the bearing from the airport of any aircraft transmitting a radio message, thus they could provide the crew with a course to fly to arrive overhead the aerodrome. They could also provide the pilots with weather information, including visibility, wind speed and direction, but also the approximate position of other traffic in the area so the crew could keep their eyes out for it.

Airline travel in 1920. An Airco de Havilland DH-4 plied the London Croydon – Paris Le Bourget route

Navigation was primitive in aviation’s early years. Clearly identifying the destination aerodrome so the crew landed at the right one was important. The pilots were helped to find the aerodrome by a bright, strobing “lighthouse” beam – green alternating with white – which was located on a high point. When control towers came in, the light was above the tower.

Croydon airport from above, 1925

Positive airfield identification was provided by very large lettering spelling out the airport name, either on the ground, or on the roof of a large hangar.

Separation between aircraft, if there was more than one near the aerodrome at any time, was assured visually by pilots looking out for other aeroplanes, with advice from the tower if necessary as to the position of potentially conflicting traffic.

Protocols about which of any two aircraft has the right to hold course and which should give way are set in the rules of the air, similar to the rules which mariners follow on the sea, and a disciplined circuit pattern over an aerodrome was a system with which pilots were familiar.

Permission to land or take off could be signalled by radio, or by a CATO shining a green aldis lamp toward the aircraft cockpit. Similarly, a red lamp would refuse permission. Firing off a green or red Verey flare from the tower was an alternative.

The UK’s principal air traffic management provider NATS is somewhat more sophisticated today! But its daily traffic tally is nearly 9,000 movements across the country, so it rather has to be.

P.S. Thanks to NATS for providing the colourised old photographs and historical detail from their archives.

 

 

 

Suddenly I see…

Today, air traffic control officers (ATCOs) on each side of the North Atlantic can see the aircraft they are controlling as they fly between Europe and North America.

It is almost impossible to convey the huge significance of this boring and apparently obvious piece of information, because most people don’t know that – yesterday – the same ATCOs couldn’t see the aircraft they were responsible for. They never had been able to see them, because the machines were outside radar range.

When flying between North American and Europe, until now aircraft of all kinds have always been invisible to air traffic control from the time they were about 350km off the coast on either side.

Under yesterday’s system, ATCOs knew approximately where each aircraft was because the pilots reported their position, their height and an estimate for the next reporting point every 15min or so. This worked safely because aircraft were painstakingly released into their pre-cleared, one-way oceanic tracks at specific heights, time intervals, and speeds, so they would maintain separation vertically and horizontally.

That system is a well-tried air traffic management (ATM) technique known as procedural control, and most of the world will continue to control air traffic procedurally over almost all oceanic and wilderness areas for some years yet.

In fact only 30% of the earth’s surface has radar coverage enabling aircraft surveillance for air traffic management (ATM) purposes.

But now, a new global constellation of 66 low-earth-orbit smart satellites – launched over the last decade by satcoms company Iridium Communications – each carries a device that links aircraft ADS-B datalink signals to ATM centres. Aircraft-mounted ADS-B (automatic dependent surveillance – broadcast) streams information about the aircraft’s position, height and much more. This enables ATCOs to track the aircraft in real time, with a radar-like update rate of 8 seconds.

Here’s the history (this announcement should really be preceded by a trumpet fanfare!): US-headquartered communications technology company Aireon yesterday announced that its space-based air traffic surveillance system was switched on, and active surveillance trials involving ANSPs (air navigation service providers) Nav Canada and UK NATS have begun on the busy North Atlantic routes that each manages from its respective oceanic base either side of the sea.

Aireon CEO Don Thoma was able to boast that “For the first time in history, we can surveil all ADS-B-equipped aircraft anywhere on Earth.”

Well, it’s true that they are set up to do so, but not all the world’s ANSPs are ready for it yet. Those who are ready include Nav Canada and NATS, but also the Irish Aviation Authority, Italy’s Enav, and Denmark’s Naviair.

The European Aviation Safety Agency (EASA) is in the process of certificating the provision – by Aireon – of space-based surveillance over the whole continent. That will be another first: the provision of surveillance capability by an organisation that is not an ANSP nor the military.

Others will follow.

Daedalus spreads its wings

The operating future of the old Royal Navy aerodrome at Daedalus is assured, says its owner Fareham Borough Council. We know, they say, because we put £1.5 million into it after we bought it last year, including resurfacing the runway.

To be fair, that looks like an organisation putting its money where its mouth is, but what about the proposed on-site National Grid interconnector terminal that – by running high power electricity cables under the aerodrome – could interfere with aviation activity and high-tech systems by creating a powerful electromagnetic field above ground?

Not on my watch, says Fareham’s Executive Leader Councillor Sean Woodward. “We saved this site for aviation, so we’re not going to do anything to damage that.”

Yes, he says, the interconnector will be sited at Daedalus to the north of the airfield, but not until means have been agreed to neutralise any electromagnetic effects, whether by shielding or by burying them at sufficient depth underground. At the moment the aerodrome costs Fareham about £0.3 million a year, says Woodward, and income from the new tenant would help with investment while they work to make the airfield sustainable.

And they have plenty of investment plans still to run, says Woodward. The big plan, already under way, is to use non-operational land on the Daedalus site to attract aviation, aerospace engineering and marine industries that would benefit from being based on an operational aerodrome. This is not such a far-fetched idea when Daedalus’ location at Lee-on-the-Solent is wedged between the civil marine port of Southampton and the military harbour at Portsmouth, plus Britten-Norman and NATS are already on site, and the airfield has a runway capable of serving business jets.

Woodward says he doesn’t see the aerodrome as the main money-maker – for the time being at least – but as the attraction to lure businesses to the site. One of the incumbents already at Daedalus is a technical college, CEMAST – Centre of Excellence in Engineering Manufacturing and Advanced Skills Training for the aerospace, marine and automotive industries. It accepts 900 students a year, all places taken.

daedalus-tower
RCA (Regional and City Airports) manages the airfield and air traffic control for Fareham

While at Daedalus last week I detected an infectious enthusiasm among people at all levels there, born of a respect for the site’s long aviation history and a determination to capitalise on it.

daedalus-slipway-hovercraft
Serious aviation history here. Daedalus was a RN Air Service seaplane base in WW1, before it became an aerodrome. Taken from the seashore, this picture shows the seaplane base slipway and the old hangars at the top. And the Hovercraft Museum that’s sited there too.