In 1928, the company Lioré
& Olivier responded to a program for a four-seater night bomber
with the LéO 25 project. This one, in continuity with the
company's previous achievements, the LéO 12 and LéO
20, is a twin-engine biplane. large, heavy and not very fast, but
with great autonomy.
Naval Aeronautics will soon
be interested in this aircraft, which after modification to "navalize",
could be an excellent bomber or torpedo maker with a large radius
of action.. This cell will receive multiple motorizations which
explains the large number of variants; You will find details in
the version section below.
The Leo 25 is making its
first flight in November 1928. Its performance is modest: it reaches
only 215 km / h and the various evolutions tried to make it faster
will not be retained, and the 6 prototypes will be abandoned (Léo
25 , LeO 252 (2 Ex.) And LéO253 (3 Ex.)
The following versions, modified
for their new Hydravion Bomber / Torpedo Boat mission, are now designated
Leo H-250 and following. Again, the details of the versions are
described below. Among these versions, the Leo H256 prefigures the
future model series Leo H257. It has an enlarged wingspan at 25.50m,
and the wing / float link is largely simplified. His essays begin
in October 1932.
The Prototype Leo H257 powered
by two Gnome & Rhone 14Kbrs star of 700ch starts his official
tests in Saint-Raphael from April 10, 1933. He will become the Leo
H257-Bis receiving Gnome & Rhone 14 Kirs of 870ch. 60 Copies
will be ordered by the Navy and the Air Force, the latter receiving
the first 21 copies. The first serial Leo H257-Bis takes to the
air in April 1936. The aircraft has a reinforced structure. Additional
tanks are arranged in the floats. These can be replaced by a fixed,
conventional landing gear. The crew of 4 is fully housed in a closed
cabin containing six separate positions. A 7.5mm mobile machine
gun is installed under a glass turret at the front of the fuselage
and complements the strong defensive armament of two other 7.5mm
machine guns. It can carry either a torpedo of 670 kgs or 500 kgs
of bombs. The first aircrafts are manufactured in the plant Lioré
& Olivier de Rochefort sur Mer, and delivered to Saint Raphael
to receive their floats. The manufacture will be transferred to
the SNCASE factory in Berre after nationalization.
Naval Aviation, wishing to
replace its aging Farman 168 as soon as possible, ordered as early
as 1932, an intermediate version, the Leo H258, pending delivery
of the first H257-Bis. This version differs from the future Leo
H257-Bis by its engine: it is indeed equipped with liquid-cooled
engines Hispano-Suiza 12 Nbr dec 650hp. These aircraft will be manufactured
in the Argenteuil plant and will be delivered from 1935. They will
take part in the Battle of France within squadrons 2S2 and 4S2 in
particular. Used as bombers, their slowness will make them very
vulnerable to enemy hunting. The eight H.258s that survived after
the Armistice were rehabilitated at the SNCASE plant in Marignane.
Three seaplanes entered the 2S4 squadron, based in Brittany, and
the rest in 4S2 in Karuba. After the invasion of the Free Zone in
November 1942, three H258 LéOs seized by the Germans will
be ceded to the Italians who will quickly abandon them.
The Leo H257-Bis will be
assigned to the 3 coastal bombing squadrons, B1, B2 and B3 of the
F1B bombardment flotilla. These units, based in Lanvéoc-Poulmic,
at Berre pond and Port-Liautey are each equipped with 6 copies,
to which we must add 6 spare aircrafts. These squadrons carried
out missions of anti-submarine and protection of convoys. The H257-Bis
will also perform night bombardment missions on enemy armored columns.
Note that GB II / 25, an
Air Force unit based in Karouba, had H257-Bis land-based. In June
1940, 18 of these copies, retransformed in seaplanes, will be yielded
to Escadrille E7 which lost a large majority of its Loiré
70 during the Italian attack of June 12th. Three more copies of
GB II / 25 will be paid to squadron 4S1 who will benefit little
since dissolved in July 1940!
After the Armistice, some
H257-Bis will be transferred to North Africa to the 1E squadron
stationed at Karouba, which will use them until 1942.
Three copies will be transferred
to the flying school of Saint-Raphael where it will also serve until
1942. In early 1943, all surviving aircraft in North Africa will
be donated to the new school of flying staff created in Morocco
by free French forces.
Pieces of spare parts, the
H257-Bis will be gradually reformed and the last Leo H257-Bis will
fly until 1945.
The dozen copies remaining
in metropolis on the pond of Berre, will be seized by the Germans
and "offered" to the Italians. They will never use them,
and the French planes will be destroyed in 1943.
