The Air Ministry sponsored trials at Lympne in late September 1924 with a view to encouraging the development of an all-British two-seat lightplane, for possible use by flying clubs. A critical constraint was that entrants should be powered by an engine of not more than 1,100 cc capacity.
The Blackburn Aeroplane & Motor Co offering was the L1 Bluebird, a two-seat side-by-side biplane powered by an 1,100cc Blackburne Thrush engine, nominally of 37 hp.
Equipped with folding wings (a requirement for the trials), the Bluebird was of all-wood construction. The type was designed with slow take-off and landing speeds in mind, as these characteristics would be favourably assessed in the trials.
The Bluebird was completed in time for the competition but suffered from teething problems with its Thrush engine. As a result, Blackburn withdrew it from the trials whilst continuing its development at Brough.
When test flown in October 1924, the Bluebird showed excellent short take-off and landing performance. Nevertheless, it was clear that a practical two-seat light aircraft would require more power. This was acknowledged in the rules for the Daily Mail-sponsored 1926 Lympne Trials, where the weight of the engine was limited to 170 lb, consistent with engines up to around 60 hp.
The Bluebird was therefore re-engined with an Armstrong Siddeley Genet I 60 hp five cylinder radial engine. After being registered (G-EBKD) the revised aircraft was flown for the first time on 4th June 1926.
During the 1926 trials, repairs to a bent undercarriage were deemed to have been enough to have disqualified the Bluebird although but its pilot (Sqn Ldr AH Longton) spent two days flying virtually continuously, covering some 800 miles.
To cap this, he then won the Grosvenor Trophy Race held on the day after the end of the trials with an average speed of 85 mph over the 75 mile course.
Sadly in June 1926, the Bluebird was destroyed in a fatal mid-air collision at Bournemouth with the prototype Westland Widgeon III where both pilots lost their lives.
The promise showed by the Bluebird led to the decision to put it into production as the L1A Bluebird II. powered by the 80 hp Armstrong Siddeley Genet II engine. The aircraft was offered in both land and seaplane configuration, with thirteen aircraft being built.
The first Bluebird II (G-EBRE) received its Certificate of Airworthiness on 25th August 1927.
The first three aircraft went to the Suffolk Aero Club with three more being delivered to the Yorkshire Aero Club. One aircraft (G-EBSW) was built as a seaplane and used for demonstration flights by Col the Master of Semphill, who landed this aircraft on the River Thames at Westminster on 1st August 1928.
On 5th August 1928, he then set off on a 3,000 mile trip around the coast of Britain, taking in Cape Wrath, Belfast, Wexford and Falmouth.
In October of the same year, he then flew the float equipped aircraft to Berlin, via Felixstowe and Amsterdam. The aircraft later reverted to its landplane configuration in mid-1929.
The final wooden variant of the Bluebird was the L1B Bluebird III with a plywood-skinned top to the rear fuselage.
The first prototype (G-EBWE) was certificated in March 1928 and was powered by an 80 hp Genet II engine. By May 1928, it had been re-engined with a 90 hp ADC Cirrus III in-line engine, the only Bluebird III to use this engine.
Five further Genet II-powered Bluebird IIIs were sold (together with one additional airframe, which was laid down but not completed).
Production then moved on to the substantially revised all-metal Blackburn L1C Bluebird IV, which is described separately.
Variants & Numbers Built
|L1 Bluebird I||One only, Blackburne Thrush, then Genet I engine. Competition No 12 (1924), No 1 (1926), registered as G-EBKD|
|L1A Bluebird II||13 production aircraft with Genet II engine|
|L1B Bluebird III||Improved version with plywood rear decking and revised fuel system. Prototype G-EBWE and six production aircraft, one of which was not completed.|
|20 aircraft (1 L1, 13 L1A, 6 L1B)|
|L1 Bluebird||L1A Bluebird II||L1B Bluebird III|
|Powerplant||One 1,100cc Blackburne Thrush then 60 hp AS Genet I||One 80 hp Armstrong Siddeley Genet II five cylinder radial engine.|
|Span||28 ft 3 in||28 ft 0 in|
|Maximum Weight||875 lb (Thrush) 1,150 lb (Genet I)||1,400 lb||1,465 lb|
|Capacity||Pilot and passenger|
|Maximum Speed||74 mph (Thrush) 85 mph (Genet I)||88 mph at sea level, 86 mph at 5,000 ft|
|Cruise speed||60-65 mph (Thrush), 70 mph (Genet I)||75 mph|
No Blackburn Bluebird I-III aircraft survive.