Vickers EFB6 and FB9
Gunbus developments

Two developments of the Vickers EFB5 Gunbus, the EFB6 and the FB9, of which the FB9 entered production and was mainly used as a trainer.
Vickers EFB6 sole example at Brooklands The one-off Vickers EFB6 with extended upper wings at Brooklands.
 
The Vickers EFB6 (about which little is known) and the FB9 (which is sometimes known as the streamlined Gunbus) were two developments of the well-known Vickers EFB5 Gunbus.
 
The EFB6 was similar to the EFB5 but with extended upper wings, supported by king posts and bracing wires. It also lacked any top decking between the two crew seats and only had ailerons on the upper wings. The increased wing area was presumably intended to increase the payload by comparison with that of the FB5.
 
The EFB6 was first flown at Brooklands, Weybridge on 14th July 1914 and it was taken on strength by the Royal Flying Corps (RFC) at the start of the First World War, although no further development of the type ever took place thereafter.
 
The Vickers FB9 was in essence a modified version of the EFB5 with modifications to 'clean up the design' and improve its performance. The main differences were a modified nacelle with a smoother, more pointed, nose and the use of a cleaner undercarriage supported on V-struts. Streamlined RAF wires replaced the twisted, stranded cables whilst the wing tips were rounded rather than retaining the rectangular plan-form used on the EFB5 Gunbus.
 
Vickers FB9 early version stbd front 16X9 An early production Vickers FB9 'Streamlined Gunbus' showing its comparatively clean lines.
 
The FB9 prototype was powered by a 100 hp Gnome Monosoupape rotary engine, driving a two blade pusher propeller and it was first flown in December 1915.
 
It was armed with a single 0.303 Vickers machine gun, mounted on the front cockpit. The top speed achieved at 82.6 mph was more than 10 mph faster than that of the EFB5.
 
With the appearance of tractor biplane fighters with gun synchronisation (such as the Sopwith Pup which was capable of 110 mph) the FB9 was declared not suitable for use as a front-line fighter. It had excellent flying qualities however, and some 119 production aircraft were ordered for use as trainers. One aircraft was later modified with an armoured nacelle with a view to being used for trench strafing, but the type was never used operationally.
 
Vickers FB9 modified armoured nose A modified FB9 built at Bexleyheath with an armoured nose.
 
At least fifty aircraft saw service with Nos 6 and 10 Reserve Squadrons and with No 187 Training Squadron in the UK.
 

Variants & Numbers

EFB6
One aircraft only, modified EFB5 with extended upper wings, flying in mid-1914. No production
FB9 Mk II
One prototype and 119 production aircraft. Serials 5271-5290, 7812-7835, A1411-A1460 and A8601-A8625.
 

Specifications (Vickers FB9)

 
Powerplant
One 100 hp Gnome Monosoupape
Span
33 ft 9 in
Maximum Weight
1,820 lb
Capacity
Pilot and gunner; one Vickers gun mounted on the front cockpit
Maximum Speed
82.6 mph at sea level
Range
250 miles

 

Survivors

No examples of the Vickers EFB6 or FB19 survive.

Other information