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Letord Let.1 / Let.2 / Let.3 / Let.4 / Let.5 / Let.6 / Let.7
In early 1916 the contemporary reconnaissance aircraft of the Aéronautique Militaire, such as the Caudron G.6, Morane-Saulnier T and Salmson-Moineau SM.1 were proving to be less than sparkling in operations and testing. To provide a suitable replacement The STAé, its Director Colonel Dorand and Établissements Letord, formulated the A3 specification and co-operated in the design of the only respondent, the Letord Let.1.
In 1916, the Letord "Let", in prototype form, recorded its first flight and this three-man, twin-engined platform was developed along the lines extended-range reconnaissance. To cover the distances required of the type, a multi-engine arrangement was used and this fitted to a relatively large airframe.
The aircraft relied on a traditional biplane wing arrangement for lift and control and the crew required to man its various systems numbered three. "Negative wing stagger" was present in the over-under wing arrangement where the lower planes were set well-forward of the upper sections, making the parallel struts angle rearwards.
Power was from 2 x engines of various makes and models throughout the service life of the aircraft and each was charged with driving two-bladed propellers. The engines were held outboard of the fuselage and atop the lower wing assembly. Each of the three crewmen sat in separate open-air cockpits so communication between them was limited. The undercarriage showcased double-wheeled main legs and a tail skid though a nose leg was usually added to prevent "nose-over" accidents when ground-running (common to larger aircraft of the war). The tail unit was marked by a single vertical fin and low-mounted horizontal planes.
Design of this aircraft was attributed to Emile Dorand.

The Letord A3 reconnaissance bomber family, the Let.1 to Let.7, were essentially similar biplanes with, variously unequal span or equal span wings, with prominent and characteristic negative stagger on their wings, powered by two tractor engines in nacelles mounted short struts or directly on the lower wings and had a fixed tailskid undercarriage. Some aircraft were equipped with a strut-mounted nosewheel to protect the aircraft and its crew from "nosing-over" accidents while landing. The pilot sat in an open cockpit under the upper wing trailing edge, with a gunner in an open position immediately aft, and a third crew-member in an open position in the nose where he could act as gunner, observer, and bomb-aimer.
Aircraft were completed, variously, with equal span 4-bay wings or unequal span 3-bay wings with longer span upper wings braced by an A-frame king-post and wires. All the Letord reconnaissance bombers shared similar plywood covered wooden structure fuselages and wooden structure wings and conventional tail-unit.
Of the 250-300 built, the Letord Let.5 was probably the most numerous of a family of 3-seat reconnaissance bombers, designed and built in France from 1916, originally to an A3 (reconnaissance aircraft 3-seat) specification from the STAé (Service Technique d'Aéronautique).
The Letord reconnaissance bombers saw widespread service throughout the Aéronautique Militaire, from mid-1917, with 121 operational on the Western Front by November 1917. Most were no longer in front-line use by the Armistice in November 1918.
A Letord Let.1
Let.1 A.3
initial reconnaissance version
three bay wing.
Engines: two 150 hp (110 kW) Hispano-Suiza 8A
Let.2 A.3
reconnaissance aircraft similar to Let.1
three bay wing.
Engines: two 200 hp (150 kW) Hispano-Suiza 8Ba
Let.3 Bn.3
night bomber
four bay wing.
Engines: two 200 hp (150 kW) Hispano-Suiza 8Ba
Let.4 A.3
reconnaissance aircraft also used as a bomber
three bay wing.
Engines: two 160 hp (120 kW) Lorraine-Dietrich 8A
Let.5 A.3
reconnaissance aircraft
three bay wing and missing the nosewheel.
Engines: two 240 hp (180 kW) Lorraine-Dietrich 8B
Propeller: 2-bladed wooden fixed-pitch
Wingspan: 18.06 m (59 ft 3 in)
Wing area: 62.3 sq.m (671 sq ft)
Length: 11.17 m (36 ft 8 in)
Height: 3.66 m (12 ft 0 in)
Empty weight: 1,660 kg (3,660 lb)
Gross weight: 2,445 kg (5,390 lb)
Maximum speed: 170 km/h (110 mph, 92 kn) at 2,000 m (6,600 ft)
Maximum speed: 152 km/h (94 mph; 82 kn) at 3,000 m (9,800 ft)
Range: 455 km (283 mi, 246 nmi)
Endurance: 3 hours
Service ceiling: 4,900 m (16,100 ft)
Time to altitude: 2,000 m (6,600 ft) in 10 minutes
Time to altitude: 4,000 m (13,000 ft) in 20 minutes
Armament: Up to 4 7.70 mm (0.303 in) Lewis machine-guns on single or double T.O.3 flexible mounts.
Bombload: 130–150 kg (290–330 lb)
Crew: 3
Let.6 Ca.3
fighter based on the Let.3
four bay wing.
Engines: two 220 hp (160 kW) Hispano-Suiza 8Be
Armament: 37 mm (1.5 in) cannon
Let.7 Bn.3
night bomber
four bay wing of increased span.
Engines: two 275 hp (205 kW) Lorraine-Dietrich 8B engines

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