Decca Navigator established its presence in France as a result of the French Postal Service requirement for the timely delivery of night airmail service. The story which follows provides the details of that service.

In imaginative thinking, France leads the world and it's 35 years now since a handful of her young pilots, flying World War I aircraft of wood and canvas over the Moroccan desert dreamed of the world's first  air mail linking "France Outre Mer"  with the homeland.

In 1919, they brought this dream to reality  hopping precariously from Toulouse to Rabat in little Breguets, Latécoères and other now forgotten warplanes. There were no maps; they made their own as they went along, naming many of the capes and landmarks after fellow pilots. They flew in pairs, so that when one made a forced landing the other could land beside him and transfer the mail while the unlucky "groundling" stayed in the desert until he had effected his own repair. Punctionality was paramount even then. It was not sufficient that the mail should get through - it had to get through on time. They became renowned and were offered new concessions.

In 1930, they were regularly crossing the South Atlantic in single engined airplanes averaging 80 mph and had opened up the airways of South America where mail-carrying overland was a matter of weeks. The important run from  Rio to Santiago via Buenos Aires was cut to 24 hours, literally changing aircraft fix or six times on the 1,900 mile flight.  The complete route included Dakar - Natal - Rio, another 3,200 miles of which 1,800 were across the Atlantic  - no mean adventure in those days.

By 1935, impressed by the progress made externally, the French postal authorities were considering an internal or 'Metropolitan' air mail service. It was one of their greatest ambitions to deliver by morning, letters posted late the previous evening no matter where. That ambition was realized by one man - Raymond Vanier. In May 1939, he and his colleagues of Societe Air-Bleu inaugurated the first air mail line, Paris to Bordeaux-Pau and three months late , a  second  - Paris-Lyons-Marseilles. Both had proved their success until WWII hindered their development.

As soon as hostilities ceased, work began again and in 1945 the present Centre d' Exploitation Postal Metropolitain del al Compagnie Air France came into being. It was responsible to the French Postmaster General for all air mail carried in France. During its first year, 1946, it carried 1,360 tons of letters and every year since has shown an increase. By 1954,  it was carrying 5,200 tons.

For the first two years (1935-36) a surcharge of 3 francs was made for air mail letters but the system proved so economical this was soon dropped. The success of his service says Vanier  is due chiefly to the magnificent spirit among his pilots and their careful study of the finer points of flying. All their services run by night. Letters posted by as late as 10:00 pm in Paris mailboxes are arriving at the mail centre at Le Bourget by takeoff time. The evening mail from England and other European countries also arrives  around the same time ready for sorting and distribution.  In comparison, if the mail in France had been distributed by train, it would have taken 24 hours if there were suitable trains but there were none.

In two years, Vanier's organization proved they could carry the mail faster and cheaper than the railways but with the same dependability. This meant taking off in the most adverse of conditions and by the use of the best navigational devices and touching down in poor visibility. In 1953, Vanier was justifiably proud of the fact that they had a 98% success rate in getting to their airfields and that 112 landings were made under Q.G.O (all aircraft grounded conditions) . They never had an accident.

A DC-3 being loaded with mail at Le Bourget field for the nightly run to Lyons and Marseille. (Photo courtesy Decca Navigator Company)

The radio altimeter is an essential part of their flying equipment and Vanier thinks very highly of the flare path system in which the lights come up on the pilot's left side instead of directly under the machine as in the Calvert system. At the moment, they are flying DC-3's but next year they are getting Nord 2501's in which the Decca Navigator will be a production fitting. Their assessment of Decca has been going on for 6 to 8 months now  and the Chief Pilot, Captain Georges Clement has given the system a most favourable report when his aircraft was first fitted with the system early in 1954.

Never resting on present accomplishments, Vanier now wants to carry passengers with his new fleet in the daytime when it is not delivering the mail. He contemplates that with his Nords, a night flight from Paris carrying mail and a day flight back meant he could charge second class fares thus keep his machines on a 24 hour schedule instead of standing them down during the day. He also believes that with the opening of a Decca chain in the southern part of France he will be able to fly with a crew of only two, leaving the Flight Log to give the necessary navigational and approach information.

Everything that Vanier has done in his long life of aeronautical experience has been bold and far sighted. That is why he finds himself at the head of the best most efficient , most profitable, most envied air-mail system in the world.

This is how the French chain 8B looked in 1957. Sometime between then and 1973, the Green slave had been shut down since it was of no real use for marine coverage in the Bay of Biscay. (Map graphic courtesy of Perry Castañeda Library Map Collection. University of Texas On-line Library. Modified by Jerry Proc)

 

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SOUTH FRENCH CHAIN

The South French Chain was first announced in the April 1955 edition of Decca Navigator News.

Since the opening of the French Chain 8B in October of 1953, constant use has been made of it by the French Night Airmail service. As a result , the Night Postal Service ordered a chain for the southern part of France which will provide extended coverage over the Basses-Alps and well out into the Mediterranean as far as the Italian border. The chain  will be used by the postal aircraft on the last leg of their nightly trip to the southeast. It will also be of benefit to other aircraft who will obtain valuable navigation assistance in the difficult mountain area stretching from the Southern Alps to the Riveria Coast. In regards to shipping, the new chain will also serve the ports of Marseilles and Toulon. The chain was never built.

This is the map which appeared in the April 1955 issue of Decca Navigator News announcing the new chain.  The Green slave (Slave 1) of the Southern chain  was going to shared with the Purple slave of chain 8B at Aurillac. Slave 2's location at  Perpignan is a best estimate.  The Master station 'M' would have been in the Montpellier area. Slave 3's location  is unknown. The chain was never built.  (Map courtesy Decca Navigator Company)

Stan Smith recalls his service at the Purple station of the South French chain. "I  worked on the South French Chain at the Purple(?) Slave Station from about October 1955 to about April 1956 with Don Matheson (from Ullapool) and André Lux of Société Française Radio-Electrique (from Paris). André was replaced by another SFR employee before I left. Don and I were about 22 and André was 36. Decca rather flattered us with the title of Engineer which impressed André who was merely a technicien! I had been a Radar Mechanic in the RAF.

I know that the station was in operation when I arrived and when I left. I always understood that it was "on trial" as an extension of coverage for the French night postal service. I don't have precise information about when it closed though I worked for DNC until Sept 1957 and during Univ vacations into the 1960s. I have always assumed the trials were not successful enough.

The outfit consisted of two trailers. One contained the two Control Racks (unlike the three on permanent stations) and the other the transmitters. I seem to recall that the transmitting aerial was a single mast. It was not continuous operation. There may have been a rather inadequate RT but we rather charmingly received switch on instructions by telegram from the Master station near Montpellier (which I also visited). The telegrams were delivered by anyone passing by the post office and us! The "on" hours were mainly at night, of course. Also on site was a caravan which we declined to live in. January had record low temps! The 'van served as a rest room. We stayed in a basic hotel in Elne some 7km away and got around on the thoughtfully provided Vespa scooter.

The outfit was in a field only a matter of a couple of hundred metres from the Med at St Cyprien-Plage on the road from the village of St Cyprien. I have never been back but I know the place is now a big holiday resort. Then it consisted of a few houses and two restaurants - one was Hotel Les Glycines. The construction of the coast road from Canet-Plage had been started but there was no work on it during my six months.  A colony of gypsies(?) lived in rush houses near the beach.

I think it was the South French Green Slave which shared site with the main French purple slave at Aurillac I have no recall of the third (Red) station and rather think it never existed.

Later in 1956 I worked for six weeks on the German chain near Coburg. There was some dispute between Decca and the German operators. They had understood the slave stations to be automatic (esp at night). That did not give enough assurance of continuity of service for Decca and they sent three of us to man the slaves at night. Telephone contact with the station at Zeven was hilarious. This was in the days of operator connected calls. Try making it clear that Zeven is not the same as the German sieben (seven) but is the telephone exchange (fernsprechamt).

All my other time with Decca was on UK stations. South to North - Jersey; Bolberry Down (Kingsbridge); Scillies; Puckeridge (Warwick); Neston (Wirral); Kidsdale (Whithorn); Earl's HIll (Stirling); Butt of Lewis (Outer Hebrides); Shetland.

In the winter at Earl's Hill the situation of the station meant little sunshine in winter and a 500m climb up to the aerial cabin. Ropes on posts were provided for use in fog!

On the butt of Lewis we were deemed to be providing a vital service so working on a Sunday was tolerated. But try whistling on a Sunday when on the way to one's lodging after a 24 hour shift.

Life took me in very different directions but It was mostly fun. I got around. And I was young".

Ron Poole worked for Decca Navigator in 1956-57. Ron recalls. " I started with an interview at High Wycombe and was sent to France after a very brief introduction to the equipment. There were four of us based at Laroque Timbaut, Lot et Garrone, in the village's only hotel. There were only a couple of upstairs rooms, no baths and outdoor toilets. The master station was in a trailer in a very muddy field with a diesel generator in another trailer. I believe one of the slaves was at Perigord".

Webmaster's comment: All these locations are in south-western France. Contributor Tony Tranfield indicates stations at Agen , Lacaneau Surf Ocean and Lannemezan, -  again, all in Southwestern France. Could this have been a Decca evaluation chain ?

This rendering might suggest a hitherto unknown Decca evaluation chain.

The March 1953 edition of Decca Navigator News reported on the use of low power transportable Decca chains by the French Navy. Transportable Chains worked on exactly the same principle as the permanent type but with a lower power output, smaller, easily dismantled aerials and earth mats, and other equipment scaled down for transportation. Generally, they covered a few thousand square miles against the more-or-less quarter-million of a permanent chain. Charts were computed and drawn specially by the user or by the Decca Navigator Company to cover the area being immediately worked.

Since 1951, the French Government become keen users of the transportable chains when the French Air Force, through the French Hydrographic Office, called for demonstrations off the coast of Brittany. The Decca agents, Société Fransçaise Radio-Electrique, arranged the demonstrations and later built much of the installations under licence. When the first trial Chain was working, the French Navy joined in the tests and they were so impressed with the possibilities that they ordered a transportable chain for their own use. Initially it was to be sited in the Bordeaux district. Here, the trials were even more successful and the French Admiralty decreed the use of Decca
Transportables for more serious work.

Minesweepers exercised with it, and manoeuvres were carried out by other classes of vessel to familiarize officers and crews. with its workings. The Chain was next moved to Casablanca to cover North African waters, where more naval exercises were held and some serious productive work carried out in hydrography. Here too, experiments were begun with a special marine version of the Flight Log which the French had been anxious to develop for use at sea. This instrument, essentially an automatic plotter, enabled a ship to be steered across a Decca lattice with very great precision, and eliminates the continuous manual plotting which was the only alternative method of accurate cross-lattice tracking.

The automatic plotter could also record the track made good, and proving a valuable addition to the Decca equipment when the latter is used for survey work and similar specialized operations. After Casablanca, the chain was moved to Tunisia, where it assumed a role of semi-permanancy. But wherever it has been in operation it had, on removal, left a vacuum which the French Navy abhorred. In 1952, negotiations were in progress for the provision of ten new transportable chains, some of which would cover new parts of France and some of the French overseas possessions.

The equipment, as already indicated, was part British and part French, and much of the preliminary work and siting was combined French and British too, carried out in a spirit of the closest co-operation, Some of the siting had been interesting. One of the early monitor stations for instance, being perched on the thickness of a mediaeval castle wall. A Master was erected in the grounds of a fortress once used to defend the Bordeaux countryside against incursions by the piratical British, while a Slave was sited on the lovely Belle Ile-en-Mer where Sarah Bernhardt long had her home. Other strange sites were found among the mosques and palm groves of Morocco.

Although these transportable chains were small, and run with only two slaves instead of the usual three, their range and their accuracy were remarkable. The later versions, with a single umbrella-type transmitting mast, improved slave-phase control, large earth mat and hydrographic-survey type receivers of high sensitivity, produced a repeatability-accuracy of 4 to 20 metres, 80 kilometres out at sea. Furthermore, decometer torque of usefully high level had been obtained at a point 300 kilometres distant from a Master station, even in the high level of atmospheric noise prevailing in Northwest Africa.

A most interesting report on the sea trials in the Bordeaux region was given in a paper by Professor Hugon, Chief Professor of Hydrography, published in La Revue Maritime. Professor Hugon's data all came from minesweeper trials, but his conclusions are general and very complimentary. He likens Decca's ability to guide a ship on a desired track to 'a veritable "rail" along the sea bottom'.

For these trials, the Master Station was sited at Fouras, the Red Slave at La Tranche 48 km. away, and the Green Slave at Soulac 53 km. from the Master. Eight minesweepers took part, but for some of the trials only the two leaders were equipped with receivers in order that 'following' techniques by the other six could be carried out. Overall, it proved very successful.

Among other manoeuvres mentioned by Professor Hugon was the recording of a 'dog-leg' track, steering visually on a buoy and plotting on Decca. By tracing the track on the sea bottom chart, a measure of the strength of the tide was obtained visually and continuously for the first time in this area. A 'Boutakoff' (closed loop) track described in the same area closed precisely on a 1:12,500 chart.

In formation keeping between ships, a helmsman responding to one-hundredth of a Decca Lane could keep station easily within 5 metres. 'The training of helmsmen was carried on without difficulty,' remarks the Professor, 'and was aided by the ability of the Officer-in-Charge to correct excessive track deviations by reference to the Decometers on the bridge.' Finally, in addition to open-sea trials such as these, Professor Hugon reported on the movement of ships in busy estuaries such as the approach to Bordeaux. Here he stressed the importance of the relative rather than the absolute accuracy of Decca, and the value of making permanent recordings of Decca readings in such a channel.

Such recordings were in fact made, from Verdon to Bordeaux on the Gentiane, Decca co-ordinates being noted every few minutes. 'Indications were of irreproachable stability and the signals of a very useful strength right up to the anchorage in Richelieu Harbour', the Professor said, and ' ... if the Decca co-ordinates of different fixed points in a swept channel are found initially, it is only necessary to repeat these co-ordinates in order to keep in safe water. It is noteworthy that this type of guidance can be achieved with a relative accuracy of about half a hundredth of a lane, which means that a spatial accuracy of about 7 metres is available. There is no need to worry with shore beacons in any absolute sense, it being only necessary to define a safe channel in terms of its observed Decca coordinates.'

Professor Hugon made the usual reservations about not expecting too much of mechanical or electrical substitutes for human care and forethought, but his general opinion on the 'Little Chains' of France was most encouraging.

Meanwhile, the first of the Big Chains of France, the next of the European family of Permanent Decca Chains, approached completion under the able guidance of Société Fransçaise Radio-Electrique with a scheduled opening ceremony in the summer of 1953.
 

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Contributors and Credits:

1) Walter Blanchard <wb(at)g3jkv.co.uk >
2) Stan Smith <s.e.smith(at)dsl.pipex.com>

Oct 29/18