Les indigènes de la 709

Collective defense action against air base 709 nuisances


The 709 air base located in Cognac and its military pilot school has for long attracted anger. Earlier, as it was stationed in Tours in the 705 base, the school motivated numerous reactions, relayed by elected representatives:

"On December 21st 2006, Mrs Beaufils, the Indre-et-Loire senator, in a written question to the minister for defence (JO Sénat du 16/11/2006), warns the minister on the delicate living conditions for some inhabitants of Saint-Pierre-des-Corps. The senator underlines a 'huge anger from the habitants and associations from cities surrounding the 705 base of Tours' as well as serious troubles and sonic pollutions caused by the base and its daily over flights of Alphajets as well as sporadic Mirage missions."

In December 2016, 17 advanced training planes Pilatus PC-21 were ordered to replace the AlphaJet ones in Tours. They are used to train, over one year, about 30 apprentices, 10 flying officers in charge of weapons, 10 flying apprentices from the navy, and 10 flight simulator trainers. The transfer to Cognac of the pilot school was achieved at spring 2020.

The training in Cognac of fighter pilots starts on Grob 120 (phase 2), takes over on the swiss planes Pilatus 21 for the ones who orient to fighting, during 26 months (23 scheduled at 2025). It ends on Mirage 2000.


Training of pilots and flying servants (Air actualités n° 732 - 2020)

The working zones in 2006    

In 2006, the working zones for the school were occupying two zones extending over 18 000 sq km. Each of the 20 sectors building the zone held each 4 aerobatics axes, concentrating nuisances. In 2020, colonel Nicolas Lyautey would mention the existence of 13 000 sq km, suggesting a focusing of disturbances since then.
The existence of fixed spots for manoeuvers is particularly worrying, if it continues, as it implies a concentration of nuisances on the same spots.blement sur les mêmes zones.

Commanding BA 709: a 2 years-long job

Each commanding officer of the Cognac-Châteaubernard base is in charge invariably 2 years. From the follow-up point of view, and especially the assurances which can be given to the population, this is obviously a bit regrettable (though we all hope that military practices are not dependent upon individuals)...

Last mandates were :

- Colonel Etienne Faury (2014 - 2016) -> Promoted brigadier general in 2020
- Colonel Vincent Coste (2016 - 2018) -> Adviser for foreign trade in 2018
- Colonel Arnaud Gary (2018 - 2020) -> Auditeur et IHEDN since 2020
- Colonel Nicolas Lyautey (since september 2020)

A typical exercice near Niort, a morning in june.

An afternoon in November 2021. According to the base commander (letter dated 21/07/21 to the mayor of Niort):
"The homgeneous spread of the activity on the whole zone volume... is a true leitmotiv" 

The much talked-about sonic level
of Pilatus PC-21

There are strong indications that the noise emissions from the Pilatus PC-21 chosen by the french air army to replace Alphajet were not a real matter of concern for the swiss maker, nor the one of its clients.

Indeed, while the invitation to tender for new planes was lauched 2015, while the contract was signed december 2016 with the ministry, the accoustic data for the engine - the so-called 'Noise Power Curves' - were not available from the swiss company.

Actually, the Royal Australian Air Force (RAAF) was the first one to order such data in 2016, from the Marshall Day Accoustics company. These data are intended to feed the RAAF modeling, to elaborate noise maps before 2035, that will include the new training plane PC-21 and military pilot schools reorganisation.

However, it is possible to judge that the Pilatus PC-21 is one of the most noisy planes in its range. It is indeed fit with the Pratt & Whittney PT6A-68B turbopropulsor, and its noise level rated by the EASA is 83 dB(A), placing this plane at the top noisier plane in the less than 9 tons category. To compare, the Grob 120 or the Cessna 170 exhibit a 72 dB level (that is, a twice lower perception level). One cannot plead that it would only replace the Alpha Jets, as it is alreay propose to replace the Grob 120 used in the first stage of training.

Then, the conclusion sounds the following: while the Australian army would meticulously investigate the accoustic impacts to be expected for its pilot school, the french minister would order those planes while no data was available, and therefore no serious modeling could be made.

The ministry could very simply lift the ambiguity, by publishing the environmental impact assessment that was made prior to the air bases restructuration, if any.

Image bleaching: a proven technique

What should be done when a public image may reveal conflictual ? Publicists have for long proposed to associate the concerned activity to others, conveying a strong, positive emotionnal charge. Decoding with the "Mustang X-Ray" inauguration.

Harassing zones for PC-21 (may 2021)

The analysis of PC-21 trajectories, between may 2020 and may 2021, reveals the training sectors for the base. The effective area is only 11 000 km2, less than the 18 000 km2 initially available for the base (see above), or the announced 13 000 km2. Excepted the transit zones around Cognac, a dozain of zones is more intensively exploited, mainly north of Cognac. The littoral is largely unexploited, and ocean ones are almost inexistant (a zone at the height of Hourtin is very rarely used). The inhomogeneous character of impacts if even more impressive when one examines the Grob 120 trajectories, which flight over a limited number of spots. In particular, they heavily impact Angouleme and its south region.

With some 250 flyings days a year, 11 000 flying hours a year and 10 Pilatus planes generally working as pairs, it is easy to compute that each zone is used in average 1h30 per day, quite far from the 40 minutes claimed by the military administration. If 5000 hours are transfered from the Cazaux base without enlarging the working area, this would rise to more than 2 hours a day !

The option to bring together bases can only have deleterious consequences for the impacts of the training exercices. Indeed, with a reduced autonomy of 1300 km / 2h20 flight, the Pilatus PC-21 cannot fly very much away from its base. Assuming that, over these 2h20, 2 x 15 minutes are devoted to reaching and coming back from the training zone, this defines a radius from Cognac to Châtellerault, or even smaller to Poitiers. This is about what is observed north of Cognac. If littoral zones and Bordeaux area are excluded, the conclusion is that there is little possibility to dilute the impact. Decisions made to close bases thus have serious consequences for the population, as they necessarily imply a concentration for the nuisances, that no available range of action can mitigate. They have no other justification than economic (in particular, the gathering of the maintenance made by the private society Babcock on a single spot), with no visible consideration for the population..

Fly over density for Pilatus PC-21 (one year).
The training zone impacts 560 000 inhabitants.

Fly over density for Grob 120 (one year)

Pilot school : this is only the beginning

With 17 Pilatus PC21 planes, the military pilot scholl has already fully proved its great powers of nuisance. But the army has, for base 709, much bigger ambitions and - but should we be surprised - it did not show any other concern than the economical ones.

So, they will add to the existing planes 8 to 10 others, which will potentially contribute 5000 more flying hours, to the 11000 ones done by the 17 planes. These planes will replace the Alphajet on the Cazaux base, which will be transfered to Cognac. The so-called transition" phase will thus be now be operated in Cognac, using Pilatus PC21. The maintenance of these planes will be provided there by the british supplier Babcock (a 11 years long contract, estimated 500 M€), which is another, economical, motivation for the concentration. While the belgium pilots, which were trained in Cazaux, are now located in the USA, there is a great temptation to train foreign pilots on our territory, while Rafales are sold abroad (Greece, Egypt, India, Quatar...). The Cazaux training zones went from the south of Bordeaux to the Pyrénées. Does the military administration intend to move these now to Poitou-Charentes ?

In such a context, the lack of any prevention scheme, of any dialogue prior to these major changes is distressing. One hesitates, to understand this methodology, between contempt and incompetence. Both are not excluded.

* "Training of foreign pilots by the air army is a strong political and industrial stake. Experienced by the french-belgium trainings and mltiple bilateral actions, Cognac 2016 will naturally be open to several cooperations. The future school will, indeed, be empowered to train pilots for the benefit of our european partners... and also to the one of other nations which would like to benefit of the french knowledge." (headquarters of the air force, 2014).

Increase of trafic from/to Cognac-Chateaubernard (2019-20-21)


The true / false of BA709 (dated May 2021)

• "Not more than 40 min. on the same district" (commander, april 2020): FALSE We have got multiple testimonies and radar tracks showing that planes or pair of planes could manoeuvre the whole morning and/or the whole afternoon on the same district, sometimes for every day in the week.

• "The activity is spread uniformly" (commander, april 2020): FALSE Cumlated radar tracks at april 2021 show, at odds with this, that the base elaborates training scenarios that repeatedly impact specific zones. Moreover, these zones have now been reduced to 11 000 km2, to be compared with 13 000 km2 initially available, mainly for the benefit of costal areas.

• "There is no impact on tourism. Anyway, there is no activity during august" (a deputy assistant, april 2021): FALSE In 2020, the missions from the school were almost normal. We received multiple testimonies from touristic facilty owners who tell how desperate they are. This assistant must have had in mind the coast fair he is used to.

• "This new propeller plane is not noisier; it just makes a higher-pitched sound" (commander, 2020): FALSE The fact that this plane has a screw propeller does not help concerning its two exhausts turboprop without silencers.When the army chose this plane, the regular data to evaluate noise - the so-called NPD curves - were not available from the manfacturer. None of these curves has ever been produced by the army to justify such sayings. Finally, in dec. 2020 (Charente Libre), the commander concedes that his planes are "noisier". A nice example that the army administration tells the truth only when forced to.

• "Starting recently, we now manoeuver on the ocean" (commander, dec. 2020): MARGINAL The training scenarios elaborated by the base only make use of very rare maritim transits and, very recently, of also very episodic manoeuvres by Hourtin. The overwhelming majority of missions are done over ground. In 2020, only between 1 and 2% of the missions where over sea.

• "One cannot disclose the training spots: that would be too dangerous owing to terrorism" (a deputy assistant, april 2021): RIDICULOUS First, such spots are shown on maps that are sent to individuals who complain about the nuisance. Second, everyone may follow the planes trajectories on the web. Third, it would be much more simple for a terrorist to target a big commercial plane, than these tiny acrobatic Pilatus. And finally, what would be the problem, as the activity is officially spread 'uniformly' ?

• "When they fly at 3000 meters, you do not hear them" (a deputy assistant, april 2021): FALSE We could observe that a PILATUS PC21 manoeuvring 3000 meters ahead, in particular as it makes sharp turns, does produce a heavy sound comparable to a sander on a floor above one's head. At this altitude, depending on weather conditions and manoeuvres, the impact distance is 5 to 10 km. For these largest distance, the impact can be comparable to the one of a loud motorbike in the distance.

• "They dont fly during week-ends": TRUE Not sure, however, this is to spare inhabitants rather than pilots..


Pilatus PC-21: a specific impact

The evaluation of sonic impact relies mostly on two noise figures.
First, the intensity, of course. For the Pilatus PC-21, this overcomes easily 45 dB for 3000-4000 meters altitude at the vertical.
Second, the spectral purity, that is to say the concentration of the noise power in a narrow frequency band. Opposite to white noise, with a uniform repartition of power over frequencies (such as sea shore noise), the frequency concentration of pure noise makes itparticularly perceptible and detremental. The following graph shows that the Pilatus PC-21 noise power is highly concentrated on a narrow frenqcy range and some harmonics (here, 250 Hz, 500 Hz, 750 Hz). Thus, this is a high purity noise. This characteristic allows the motor noise to be heard up to 10 km away from the source. A high altitude jet, although it is also perceptible, shows drastically different chracteristics: the noise powe is spread uniformly over the range 0-400 Hz.