The Aerotrain Story

The following text was written by Stéphane Bastien, a french journalist, in 1987.

Thanks to M. Jacques Laframboise for the translation and adaptation.

If I said "AEROTRAIN" what would you think?

This question, I have often asked it during my research on Aérotrain. I received many wrong, or sometimes fanciful, answers. People old enough to have followed technical events between 1965 and 1974 should remember this name.
Indeed, the name describes a process which, when it was applied to a means of transportation, created a revolution.
To begin, one must introduce the man who, with his research team, has conceived and developed this process.

Jean BERTIN, a graduate from Ecole Polytechnique, France, worked as an engineer at SNECMA. In 1956, he left SNECMA it to establish a research and development company, Société Bertin. Its aim was to apply the latest scientific developments to industrial processes.     
Initial projects concerned silencers for jet engines.

In 1957, Louis DUTHION, a BERTIN engineer, observed an unexpected force increase while measuring pressure losses in silencers. This was due to ground effect intervening in the experimental rig.
Ground effect was discovered at the end of the 18 century by Young, an English scientist. However, only in 1916 was the idea put to work in a vessel which attained 75 km/h.

In 1958 société BERTIN learned that in England, Christopher COCKERELL had applied this idea to an amphibious vehicle : thus there was a simultaneous discovery, or rather a simultaneous rediscovery.

The French group first applied the technique to overland transportation.

Financial partners showing little interest, it was the army that ordered a vehicle able to move over unprepared surfaces. It was named "TERRAPLANE BC4" and was first tested on January 7, 1962.
It was for this vehicle that the BERTIN team developped the first flexible cushion skirts.

This work led to other applications of flexible skirts, such as high speed tracked vehicles. It was surmised that, when equipped with an air cushion, a vehicle moving over a flat surface would operate with a fairly small gap. Hence, the idea of a guideway providing support and guidance. The inverted "T" guideway was chosen as it provided safety and simplified implementation. A scale model was then built : 1,25m in length and 0,25m wide, electrically powered, it operated on a 20m elevated guideway.

Tests started in February 1963, and were witnessed by a number of French and foreign personalities. These tests having been completely successful, it became essential to build a prototype able to carry a few persons.

Prospections began with SNCF and RATP, in order to define a commercial application. RATP quickly indicated that their needs were satisfied with the "wheel on rail" system. As for SNCF, after an in depth study, indicated that they were not interested in a system that would, for instance, put Paris within an hour and a half of Lyon.

The promoters thereafter went to a new organism, the "Délégation à l’Aménagement du Territoire" (Territory Planning Commission), directed by Olivier GUICHARD. He was enthralled by the idea and granted funds to implement a half-scale test vehicle, which could carry a few passengers.

The Transportation Ministry could not, due to lack of research funds, support the design team of the "Société d’Etude de l’Aérotrain" created in April 1965.

In May of the same year, design and construction of the guideway were going on in earnest. The guideway was built on an unused section of the Paris-Chartes line, without any level crossing, using prefabricated concrete sections that were levelled on blocks about thirty centimetre high.

The experimental vehicle was completed December 16, 1965 when there was only one kilometre of guideway ready of the planned 6,7 kilometre. Nevertheless, it was brought to the site in order to carry out a test run at the end of December.

AEROTRAIN 01, 10,11m long and weighing 2,6 tonnes, is guided and supported by lightly compressed air produced by two fans, each powered by 50 hp Renault Gordini engines. Propulsion is provided by a 260 hp aircraft engine driving a three bladed reversible pitch propeller.
The control cabin sits two technician, while the passenger cabin, immediately behind, accommodates four persons.
After putting the vehicle astride its track and starting the Renault engines, it lifted up with an air gap of 2 to 3mm, creating the air cushion. To move the vehicle a simple push by hand sufficed since the AEROTRAIN did not touch the guideway.

The propulsive engine was started and the 01 made a to and fro run on, or rather, over the one kilometre of concrete guideway available. It easily attained 90 km/h, a high speed for such a short length.

The guideway was completed in mid-February. The wait was trying for the team as there was no modification needed, the vehicle having operated perfectly.

On February 21, 1966, the guideway and the vehicle were inaugurated officially. It attained 100 km/h in front of the Press. It attained 200 km/h a few days later, without modifications.

The "Aircraft without wings", a nickname given by Jean BERTIN, was even presented on Eurovision. At that time, SNCF wanted to increase luxury train speed from 140 to 160 km/h, a curious quest when one could travel at 200 km/h in a vehicle that was both simple and inexpensive !

Visitors came to Gometz, the guideway head station, where the AEROTRAIN operated every day. Ministers, reporters, curious peoples, all wanted to see the train of the future…

In order to verify operation of the air cushions at higher speeds, the 01 was fitted with an auxiliary rocket in addition to the aircraft engine, bringing the effective power to 1700 hp.
It attained 303 km/h on December 23, 1966 in the presence of Olivier GUICHARD and André SEGALA, president of SNCF.    

At that time SNCF was launching project C03, a code name for "railroad possibilities over new substructures". Genesis of the TGV was on its way...

Modified again with a Fouga Magister jet engine, the 01 attained 345 km/h on November 1, 1967.

Such results, coupled with rapid progress, prompted the Transport Minister, Edgard PISANI, to propose a link between Lyon-Bron and Grenoble, for the Olympic Games.
A study was rapidly carried out, involving an 86 km single line, covered in 30 minutes at a cruising speed of 200 km/h. Unfortunately, government decisions having been taken too late, it became evident that the line could not be completed in time.
Thus the first occasion for AEROTRAIN to carry real travellers was missed.

Nevertheless, the impressive results obtained with the 01 led Edgard PISANI to order on December 18, 1967, the construction of a full-size 18 kilometre test guideway, which could be afterward integrated in a Paris-Orléans line.

The contract was for an 80 passengers vehicle able to maintain a 250 km/h cruising speed on a line designed for 400.
Work quickly started and in December 1968, 10 km of guideway were installed.

The Gometz test track would see another record broken by the "AEROTRAIN 02" prototype. Built to an order of March 1967, this was a two-place vehicle, with fine lines and propelled with a Pratt & Whitney jet engine of 1250 kg thrust.
It attained 300 km/h in the initial tests in May 1968 and, with the help of an auxiliary rocket, broke the 01 record by attaining 422 km/h on January 22, 1969.

AEROTRAIN I-80 for the Orléans project, has its public presentation at Le Bourget, on July 7, 1969.
A few days later it was moved to the Orléans test base.

AEROTRAIN I-80 was on its guideway September 10. On the 12, I-80 attained 200 km/h and on the 13, 250 km/h. This is the maximum speed to be attained on the 18 km guideway with its ducted propulsive fan and its two 2200 hp gas turbines. Progress went as fast as the AEROTRAIN !

On November 13, 1969, preliminary trials were completed in the presence of the Transport Minister and of the delegate from the Territory Planning Commission.

In October 1973, I-80 was modified for higher speeds : an aircraft jet engine was installed instead of the ducted fan. A speed of 400 km/h was attained rapidly.

If you had been among the 2900 passengers that were carried at more than 350 km/h during its numerous tests, you would have certainly been surprised to be able to deal with your mail aboard I-80 as well as at your own office.
As to operators filming the tests, they could do it in the control cabin without special support, the guideway flowing by at 110 m/s.

The world speed record for overland air cushion vehicle was established on March 5, 1974 with a mean speed of 417.6 km/h, with a peak speed of 430 km/h, thus demonstrating the viability of the concept.

It must be noted that such speeds are not, in a commercial sense, competitive ; this is true for all transport modes. To go from 200 to 400 km/h thrust must be quadrupled to counter air resistance, thus requiring an 8-fold increase in power.
Jean BERTIN concluded early on that an economically reasonable speed for ground transportation should not exceed 350 km/h.

Because of these impressive results, a number of aerotrain links were proposed, such as : Paris-Orléans, Paris-Lyon, Orly-Etoile, Bruxelles-Genève through Luxembourg and Basel, Calais-Fourmies by Dunkerque and Maubeuge, Aix en Provence-Marseille, Orly-Roissy, La Défense-Cergy Pontoise.
These two were very close to implementation. The first one would have linked Orly and Roissy airports through Joinville le Pont, over a distance of 56 km, covered in only 20 minutes. Orly would have been 20 minutes from the Opéra through an interconnection with the RER. This project, which will be sorely missed later on, was put aside in order to build the La Défense-Cergy link.

Again the study was carried out rapidly, leaving many choices for the propulsion mode.

The contract was signed June 21, 1974. AEROTRAIN would thus be able to prove its worth and this link would become a showcase for French innovation.
But on July 17, the government let it be known that it did not want to build the line anymore.

All these years of research, tests and successes were annulled. Other attempts to implement AEROTRAIN lines were made, but the announcement, September 1975, of a TGV line between Paris and Lyon was the deathblow. Jean BERTIN, worn out by all these years of hard work, died December 21, 1975.

However, the ideas are still here.

Nevertheless, the AEROTRAIN concept has not aged. The qualities evidenced through the tests are still at the forefront : economy, speed, frequency, environmental respect and comfort.