1. Design

2. Specifications (projected)

3. References
    Bibliography 

The Avro 684 was a proposed British high altitude heavy bomber of the Second World War, based on Avro's successful Lancaster.^[1]

Design

Due to the increasing vulnerability of contemporary heavy bombers, the need to fly at ever higher altitudes to avoid Anti-aircraft fire and fighter interception became paramount. Avro developed the Lancaster to fulfil the requirement for such a high altitude bomber completing a brochure in August 1941, for the Avro 684 Stratosphere Bomber. Chadwick decided to design a bomber that would dispense with defensive armament and rely on altitude and speed to evade enemy defences and was essentially a Lancaster with the nose section containing a pressure cabin (similar to the cabin from the Vickers Wellington B Mark X) and a large 'chin' mounted air intake and heat exchanger assembly. Pressure in the cabin was to be maintained at the {{convert|10,000|ft|m|abbr=on|0}} equivalent up to {{convert|40,000|ft|m|abbr=on|0}}.^[1]

To achieve this performance, Chadwick used an engine arrangement called the 'Master-Slave' layout. The four wing-mounted Rolls-Royce Merlin XX engines driving four-bladed {{convert|13|ft|m|abbr=on|0}} diameter Rotol propellers, were to be supercharged by a fuselage-mounted slave Rolls-Royce Merlin 45 engine driving a large supercharger supplying pressurised air via an intercooler. The output from the slave engine was to be controlled to supply air at {{convert|20,000|ft|m|abbr=on|0}} equivalent pressure between {{convert|20,000|ft|m|abbr=on|0}} and {{convert|40,000|ft|m|abbr=on|0}}.^[1]

Due to the pressure of constant developments to the Lancaster and design work on the York, the 684 was abandoned.^[1]

Specifications (projected)

|genhide=
|crew=
|capacity=
|length m=
|length ft=
|length in=
|length note=
|span m=
|span ft=
|span in=
|span note=
|upper span m=
|upper span ft=
|upper span in=
|upper span note=
|mid span m=
|mid span ft=
|mid span in=
|mid span note=
|lower span m=
|lower span ft=
|lower span in=
|lower span note=
|swept m=
|swept ft=
|swept in=
|swept note=
|dia m=
|dia ft=
|dia in=
|dia note=
|width m=
|width ft=
|width in=
|width note=
|height m=
|height ft=
|height in=
|height note=
|wing area sqm=
|wing area sqft=
|wing area note=
|swept area sqm=
|swept area sqft=
|swept area note=
|volume m3=
|volume ft3=
|volume note=
|aspect ratio=
|airfoil=
|empty weight kg=
|empty weight lb=
|empty weight note=
|gross weight kg=
|gross weight lb=
|gross weight note=
|max takeoff weight kg=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity={{convert|2,130|impgal|l|abbr=on|0}}
|lift kg=
|lift lb=
|lift note=
|more general=

|eng1 number=4
|eng1 name=Rolls-Royce Merlin XX
|eng1 type=V-12 liquid-cooled supercharged piston engines
|eng1 kw=
|eng1 hp=1,480
|eng1 shp=
|eng1 kn=
|eng1 lbf=
|eng1 note=at 3,000 rpm at {{convert|6,000|ft|m|abbr=on|0}} (un-boosted by slave engine)
|power original=
|thrust original=
|eng1 kn-ab=
|eng1 lbf-ab=
|eng2 number=1
|eng2 name=Rolls-Royce Merlin 45
|eng2 type=V-12 liquid-cooled supercharged piston engine
|eng2 kw=
|eng2 hp=1,515
|eng2 shp=
|eng2 kn=
|eng2 lbf=
|eng2 note=at 3,000 rpm at {{convert|11,000|ft|m|abbr=on|0}} driving a large supercharger delivering pressurised air to the wing mounted engines via an intercooler.
|eng2 kn-ab=
|eng2 lbf-ab=
|eng3 number=
|eng3 name=
|eng3 type=
|eng3 kw=
|eng3 hp=
|eng3 shp=
|eng3 kn=
|eng3 lbf=
|eng3 note=
|eng3 kn-ab=
|eng3 lbf-ab=
|more power=
|prop blade number=4
|prop name=Rotol
|prop dia m=
|prop dia ft=13
|prop dia in=
|prop dia note=fully feathering constant-speed propellers
|rot number=
|rot dia m=
|rot dia ft=
|rot dia in=
|rot area sqm=
|rot area sqft=
|rot area note=

|perfhide=
|max speed kmh=
|max speed mph=410
|max speed kts=
|max speed note=at {{convert|42,000|ft|m|abbr=on|0}}
|max speed mach=
|cruise speed kmh=
|cruise speed mph=330
|cruise speed kts=
|cruise speed note=at {{convert|42,000|ft|m|abbr=on|0}}
|stall speed kmh=
|stall speed mph=300
|stall speed kts=
|stall speed note=
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|never exceed speed note=
|minimum control speed kmh=
|minimum control speed mph=
|minimum control speed kts=
|minimum control speed note=
|range km=
|range miles=2,300
|range nmi=
|range note=
|combat range km=
|combat range miles=
|combat range nmi=
|combat range note=
|ferry range km=
|ferry range miles=
|ferry range nmi=
|ferry range note=
|endurance=
|ceiling m=
|ceiling ft=50,300
|ceiling note=absolute at {{convert|38,492|lb|kg|abbr=on|0}}
|g limits=
|roll rate=
|glide ratio=
|climb rate ms=
|climb rate ftmin=940
|climb rate note=
|time to altitude=time to {{convert|40,000|ft|m|abbr=on|0}} - 57 minutes
|sink rate ms=
|sink rate ftmin=
|sink rate note=
|lift to drag=
|wing loading kg/m2=
|wing loading lb/sqft=
|wing loading note=
|disk loading kg/m2=
|disk loading lb/sqft=
|disk loading note=
|fuel consumption kg/km=
|fuel consumption lb/mi=
|power/mass=
|thrust/weight=
|more performance=

|armament=* {{convert|12,000|lb|kg|abbr=on|0}} of bombs
|rockets=
|missiles=
|hardpoints=
|hardpoint capacity=
|hardpoint rockets=
|hardpoint missiles=
|hardpoint bombs=
|hardpoint other=
|avionics=
}}

References

Bibliography

• Butler, Tony. British Secret Projects. Fighters & Bombers 1935 - 1950. Hickney, England: Midland Publishing. 2004 {{ISBN|1-85780-179-2}}.
• Holmes, Harry. Avro Lancaster. The Definitive Record 2nd Edition. Shrewsbury, UK: Airlife Publishing Ltd, 2001. {{ISBN|1-84037-288-5}}.

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