mercredi 29 février 2012

The Breguet 690: A good design, better suited for recce than the still fair Potez 630... (revised 01 / 07 / 2014)

The French twin-engined fighters program, a characteristic fossil of the 30's

Like the Potez 630 and the Hanriot 220, the Bréguet 690 was an answer to the multi-engined fighters program of 1934 published by the French Armée de l'Air

This program was asking for a twin-engined fighter with 3 crew members and a maximum weight of 3,500 kg (7,715 lb)

One might wonder: Why as much as 3 men for such a lightweight plane and why a so drastically limited loaded weight, forbidding any use of powerful engines? 

The engines initially chosen by the deciders (as usual in the 1935 France) for these planes were the Hispano-Suiza 14 Ha, later designed as 14 AB, at their very early prototype stage (!).

The Potez 630, first ready to fly

The Potez being first ready to fly in 1936, received the first engines, which were, of course, completely unreliable. 

During that year, nevertheless the Potez showed outstanding flying qualities, reaching its contractual speed (460 kph) and climbing fast (4000 m in 7 minutes). 

Obviously, an official order followed in 1937 and, thanks to the good engineering process of the Potez team, began to be really mass produced by the mid of the 1938 year. 

The main part of the Potez production was dedicated to the recce with two subtypes: Potez 637 and 63.11. 

A recco variant, the Potez 637, à peine plus lent que le chasseur à cause de la petite gondole ventrale réservée à l'officier observateur. 

A la masse de 4121.5 kg au décollage, les vitesse en étaient : 367 km/h           au niveau de la mer, 403 km/h             à 2 000 m,439 km/h             à 4 000 m,448 km/h             à  5 000 m,446 km/h             à 6 000 m,428 km/h             à 8 000 m,  La vitesse de croisière économique de 320 km/h permettait de franchir 1435 km. Plein gaz, donc à 448 km/h, il pouvait franchir 740 km. A 80 % de la puissance maximale, il pouvait franchir 1390 km à 415 km/h. Les temps de montée étaient tout à fait corrects :    3' 02"             pour 2 000 m,  6' 09"             pour 4 000 m,  9' 14"             pour 6 000 m,16' 48"             pour 8 000 m,

Le plafond dépassait 9500 m. Cet avion était irrattrapable pour des Bf 109 B, C ou D. Sa maniabilité en faisait une cible difficile à très basse altitude par la variante Emil.

Unfortunately, both were insufficiently fast to do safely such a job! 

Among the 730 Potez 63.11 produced, 220 were destroyed by the Jagdwaffe...

The Bréguet 690second to fly...

It resulted - from the weak stage of perfecting of the Hispano-Suiza engines - one full year of waiting before the Bréguet fighter can receive her engines and fly!

Finally, with these so lately provided engines, the Bréguet 690 fighter demonstrated also very good flying qualities and very better performances: 
  • 390 kph at        0 m, 
  • 430 kph at  2000 m,
  • 475 kph at  4000 m,
  • 490 kph at  5000 m.

These motors were not sufficiently reliable, so it was necessary to change them for Gnome-Rhône (SNECMA) 14 M - 0.96 m in diameter - which impressed the Germans so much so that they used them for the Henschel 129 B and C tank busters. 

The new plane was designated as the Br. 693.

Bréguet 693 - the fastest of the lightweight multipurpose twin-engined French planes

Dedicated to ground attack

An order followed to create a ground strike force completely new for France, with resulted in a true efficient experience on the hedge-hopping flight, but without any clear awareness about the German AA fires (Flak) capacities. 

The Bréguet had self sealing tanks and light armor plates.

A grand total of 225 were produced before the June, 14, when the German troops entered in Paris.

The released planes fought gallantly against the Panzer columns until the last days. Little by little, their tactics became more safe and more dangerous for the enemy.

Unfortunately, they were among the first (with numerous Fairey Battle) to learn the awful efficiency of the 20 mm Flak. 

Even at the end of the conflict, Allied pilots have lost their precious life while trying a second firing flight over Flak protected areas. 

But, at the very beginning of the Battle of France, this lesson was a complete surprise.

A wasted chance

If the Bréguet team had used the wasted year to adapt their beautiful plane to the liquid-cooled inline Hispano-Suiza 12 X engines, the history would have been completely different. 

These "unbreakable" engines, slightly more powerful, allowed a much more aerodynamic cowling. 

The Br. 690 would have reached at least 510 - 520 kph and a higher service ceiling. 

As a recce plane, she would be more successful with less casualties than both the Potez 637 and the Potez 63-11. 

The fore fuselage allowed a more interesting place for an observer. 

The considerably better speed would have induced shorter mission time, this being an efficient protection against the German fighters.

May be, her derivatives with more powerful engines, as the dreadful Br 700, could have issued some true valuable long range fighters, culminating in the the Br. 820, to see here ( of the lovely De Haviland Hornet.

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