Blackburn L.1 Bluebird

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Contents

Type Description

• L.1 Bluebird I
• Low-powered two-seat, wooden single-bay biplane, with folding wings, designed as a competitor in the 1924 Lympne light aircraft trials. The fuselage was of rectangular section with rounded corners, the front portion being plywood box structure, while the rear was a coventional fabric covered wire braced structure of wooden longerons and struts. The side-by-side cockpit was located under the upper centre section leading edge, featuring a central bridge member between the two occupants, with a fireproof bulkhead between it and the the engine. The fabric covered wings, set with considerable dihedral and a moderate amount of sweepback, featured spruce spars and Warren girder ribs, with duralumin drag struts. The interplane stuts were also of duralumin. Ailerons were fitted to all four mainplanes. The strut braced tailplane was unbalanced and featured a rounded profile, as did the fin and rudder. Due to its narrow undercarriage track, small hoops were fitted below the outer wing to protect the wingtips. Initially powered by 1,100 c.c. Blackburne Thrush powerplant, it was later fitted with a 60 h.p. Armstrong Siddeley Genet I.

• L.1A Bluebird II
• Production and strengthened version. The position of the engine was been lowered, giving the top and bottom curves of the nose a more symmetrical shape. In the cockpit, a central bridge member which used to interfere between the heads of the pilot and passenger was removed, and the side structure considerably lowered, allowing deeper side doors. The gap between the wings was increased, and part of the top centre section was been cut away at the trailing edge to improve the view. Certain detail modifications were made in the wing structure, including heavier spars, and the upper and lower ailerons were interconnected by rods. A wider, split, undercarriage was fitted, eliminating the need for the underwing hoops, and both standard undercarriage and seaplane floats were available and were interchangeable, the attachments being made at the same joints on the fuselage. One 80 h.p. Genet II powerplant.

• L.1B Bluebird III
• Modified internal structure. One 90 h.p. Genet III powerplant.

• L.1C Bluebird IV
• Completely redesigned with a fabric covered all metal structure. The fuselage was in three sections, and for simplicity only one size of steel tube was used throughout, with the exception of a tube in the engine bearer and one or two others elsewhere. The first extended from the engine bulkhead to just aft of the cockpit, with longerons and side panel struts of steel tube, with Duralumin frames and side panel bracing by diagonal tubes. The rear fuselage was perfectly symmetrical, so all four longerons were of the same length. The vertical and horizontal struts are of the same diameter and gauge as the longerons, with diagonal bracing is by threaded tie rods. The final section formed the stern post, tail and skid attachment. The fuselage structure was of rectangular section, which changed into a rounded one by the addition of fairings consisting of Duralumin stringers carried on short stubs clamped to the fuselage struts.
  The folding wings had dihedral and slight sweepback. The steel spars consisting of two identical halves, of rolled flat steel strip, joined by riveting along the neutral axis. The Duralumin ribs had flanges made from rolled strip attached to webs of Duralumin sheet. Frise type ailerons were fitted to the lower plane only, and Handley Page automatic wing tip slots on the top plane were available as an option. The tail surfaces were of steel tube, with light ribs of Duralumin. A nearly rectangular balanced rudder, without a fixed fin, replaced the rounded fin and rudder assembly of the wooden Bluebirds. Various powerplants of 90-135 h.p. as noted.

Production Details

Notes

1. Blackburn used a series of Works Order Numbers rather than Constructors Numbers to identify individual airframes, but referred to here as C/n's for consistency.
2. All Blackburn-built aircraft were built at the Olympia Works, Leeds, but erected and flown from Brough Aerodrome, East Yorkshire.
3. Registration not applied; flew under Class B conditions as B-10.

Production References

1. Blackburn Aircraft Since 1909, A.J. Jackson (Putnam, 1968 and 1989)
2. British Isles Civil Aircraft Register 1919-2011 (LAAS International)
3. British Civil Aircraft Registers 1919-1928, Peter W. Moss (Air Britain Publications, 1969
4. British Civil Aircraft Registers G-FAAA-'FAAZ (1920-1928) and G-AAAA-'AAZZ (1928-1930) Peter W. Moss (Air Britain Publications, 1971)