Friday 31 December 2010

Future British Combat Aircraft Bases


Since the recent Strategic Defence and Security Review the subject of bases for combat aircraft has been in the news a great deal.

It has been announced that some bases are to close and local communities are rallying round to protect their own flying stations.

Here we shall consider how many bases British combat aircraft require and where they should be located.

First let us look at the current situation.


The above map shows the locations of Royal Air Force bases in the United Kingdom.

Flying stations are shown in red.


Note the cluster of bases in the South East which is a legacy of the Second World War.

This map can be looked at in more detail by clicking on the bases at this link.



This map shows the locations of current Royal Air Force combat aircraft flying stations.


Cottesmore and Wittering are bases for Harrier aircraft.

Harriers were at one time relocating from Wittering to Cottesmore but both bases are now likely to close folowing the Strategic Defence and Security review.


Marham and Lossiemouth are the current bases for the Tornado G.R.4 fleet.

It is expected that at least one of these bases will close.


Typhoons are currently stationed at Coningsby and Leuchars.

There have recently been some questions over the future of the base at Leuchars.



The British combat aircraft fleet numbered about 330 aircraft in 2009.

Under current plans,over the next decade the Royal Air Force will receive 160 new Typhoons and 96 refurbished Tornados for a total fleet of 256 aircraft.

This reduction in aircraft numbers has reduced the number of bases which are required.


There are a number of factors to be considered regarding the number and location of air bases.


As all potential basing options for British combat aircraft are on existing established air bases we need not address many of those factors here.


For example,if we were choosing a greenfield site,we would have to be certain that there was space for an adequately long runway,but that is not a factor when we are considering the use of existing airfields with existing runways.


We shall confine this discussion to cost effectiveness,redundancy,and time to intercept.




The most cost effective basing option is to have all combat aircraft at a single location.


However,that would require a base far larger than any currently available,most current bases are built to accommodate a wing of several squadrons.


It would also leave no redundancy.




Redundancy is important as an airfield can be closed by a number of factors such as weather,engineering work or enemy action.


Maximising redundancy would entail having small numbers of aircraft dispersed amongst a large number of air bases but this would be very expensive.




Another important factor is the need to police British air space.


Distance is a critical factor in air combat.


Close bases increase both the combat effectiveness and cost effectiveness of air assets.


 In air defence operations a shorter distance from the base to the operating area results in shorter time to intercept and longer time on station.


It also reduces the number of aircraft required to maintain a constant patrol and the amount of tanker aircraft which are needed.


Therefore,it is desirable to have a number of bases distributed about the country for air defence purposes.




What is needed for financial reasons is the practical minimum number of air bases.

That number must allow an adequate degree of redundancy.

It must also allow adequate air defence coverage.



At present there is a cluster of 4 bases in the East of England and another 2 bases in Scotland.

There are no combat aircraft stationed in the South or West of the United Kingdom.

The South West of England has no air defences at all.


This leaves the Royal Navy's bases open to attack from cruise missile firing submarines.

Aircraft which will operate on the future Queen Elizabeth class aircraft carriers are expected to be based in Scotland,far from the ships they will fly from.

The current situation is clearly unsatisfactory.

The current number of 6 airfields is far more than the future 3 wing combat aircraft fleet will require.

There is excessive redundancy in the East of England.

There is no base to provide air defence to the South West.

There is no nearby base to support the South coast based aircraft carriers.



The above map also shows the two former Nimrod bases at St.Mawgan and Kinloss and the former Sea Harrier base at Yeovilton.


Kinloss and St.Mawgan were both considered as bases for the F35C Lightning II.


All three of these bases could accommodate combat aircraft.




The bases in the South West would allow carrier capable F35Cs to be based near to the aircraft carriers they will fly from.


They would also allow provision of air defence in this area.


In addition,given the often significant disparity in weather between the South West and other parts of the country,they would provide useful divert locations for combat aircraft from other areas.


There is currently some uncertainty about the future of the former Nimrod base at St.Mawgan.


It's runway has been given over to civilian use.


However,the former Sea Harrier base at Yeovilton has a secure future as a Helicopter base and consequently,basing F35s there would be highly cost effective as it would allow an additional air base to be closed.


St.Mawgan is positioned furthest West which is useful for air defence operations,though the threat from this direction is very low at present.




There is clearly a need for a fast jet base in the East of England and another in Scotland.


It is difficult to see any justification for more than a single combat aircraft base in each of these areas in future.


Either Cottesmore,Coningsby,Wittering or Marham could provide the East of England air base for a wing of Typhoons.


Only one of those bases would be required,the most appropriate being retained and the other 3 bases can then be closed.


As a current Typhoon base,Coningsby appears the most likely to be retained.




In Scotland,Leuchars,Lossiemouth and the recently ex-Nimrod base at Kinloss are all potential combat aircraft bases.


Lossiemouth and Kinloss have the advantage of being further North which is beneficial for air defence purposes given the direction of likely threats from Russia.


Kinloss was intended as a base for the F35C Lightning II.


Leuchars is already a base for Typhoon aircraft.


By retaining a single Scottish site for Typhoon aircraft we can close the other 2 of these bases.




By retaining a single combat aircraft base in the South West,East and North,Britain can retain adequate redundancy and air defence coverage.


Retaining these 3 bases will allow the closure of 6 other bases including the 2 former Nimrod bases.


This will result in significant long term cost savings.


The even distribution of bases around the country provides significant redundancy and ensures that aircraft can be based close to where they are needed for air defence purposes.

Sunday 26 December 2010

Warship Weapon And Sensor Arcs





In the days when a warship's armament consisted almost entirely of turret mounted guns,firing arcs were a subject of great importance.




Today weapon firing arcs are still important but ship designers must also consider sensor arcs.


As targets must be detected and tracked before they may be engaged,sensor positioning takes precedence over weapon positioning.


Many weapons can fire over the horizon but most sensors are directional and must be mounted high in the ship to extend their horizon.




Fortunately,sensors are usually lighter than weapons and consequently can often be carried on tall masts which give them both all round coverage and a distant horizon.




There are also some weapons to which firing arcs do not apply such as some missiles fired upwards from vertical launch systems.


These may rise high enough to clear a ship's masts before manoeuvring towards the target.


On board a warship,weapons and sensors must compete for space with communications and electronic warfare systems.


Some of these are directional and need clear arcs while others,such as satellite and High Frequency communications are less affected by such constraints in the horizontal plane as they receive signals largely from above.


For the sake of simplicity we shall not consider such systems further here.


We shall also neglect discussion of underwater systems for the sake of brevity.



A modern warship is likely to carry a helicopter and this requires an unimpeded approach.



In the event of a mishap,a stern mounted flightdeck is desirable as this is safer for both the ship and helicopter.

Notice how the helicopter sets the flightdeck on fire in the above video,all of the crew survived this accident.



The layout of a typical surface combatant,the British Type 22 Frigate Her Majesty's Ship (H.M.S.) Cumberland,can be seen above.



The ship's major weapon systems can be seen above.


In the days when a ships weapons consisted primarily of turreted guns,the Royal Navy used a system to label warship gun turrets.

The above picture illustrates this system as applied to the modern frigate H.M.S.Cumberland.

Forward positions were labelled A,B,C etc. starting at the bows and working back.

Positions aft were labelled Y,X,W etc. working forward from the stern.

In the centre of the ship positions were labelled P,Q,R, etc. working back from the bridge.

Positions on the port side of the ship were labelled P1,P2,P3 working backwards from the bows.

Positions on the starboard side of the ship were labelled S1,S2,S3 etc. working back from the bows.

Here we have applied the system not only to gun turrets but also to sensor turrets,missile launchers and the helicopter flightdeck.



The unobstructed all round coverage of a radar mounted on a tall mast is illustrated above.


The ship's helicopter can approach from astern or alongside giving it a 180 degree approach arc to the flight deck.


The firing arc of the Goalkeeper Close In Weapon System (C.I.W.S.) is restricted by it's close proximity to the forward mast.

It is also restricted by the Sea Wolf tracker mounted in front of it.


Side mounted 20mm cannons have very poor firing arcs restricted by the ship's superstructure.

Earlier Batches of Type 22 frigates had their cannons mounted on the bridge wings where they had slightly better firing arcs.


Firing arcs for the main gun are significantly restricted by the ship's superstructure..

The forward superstructure is slightly chamfered at the sides which reduces this restriction to some extent.

The ship's freedom to manoeuvre in combat is reduced by this restriction as it must keep targets within it's firing arc.


The arcs of the forward Sea Wolf missile launcher are similarly restricted by superstructure.

It can be seen from this picture that the superstructure has been chamfered specifically to increase the Sea Wolf firing arc.


The superstructure forward of the aft Sea Wolf launcher also has chamfered edges to mitigate it's restriction on missile firing arcs.

Note how chamfers have to be asymmetrical due to the launcher being mounted off the centre line.


This picture shows the combined firing arcs of the forward and aft Sea Wolf missile launchers.

It is evident that,together,both launchers provide excellent all round coverage to well within the missile's minimum engagement range.



However,if any launcher ran out of missiles (they only have 6 ready rounds each),suffered a technical failure or was damaged by enemy action,the lack of overlap would leave a substantial undefended sector.

In the event of an attack the ship would have to conduct substantial manoeuvres to keep incoming targets within it's firing arc.


The Sea Wolf missile's trackers are mounted higher in the ship,above the superstructure.

This allows them to cover very wide arcs as they are obstructed only by narrow masts and funnels which they are mounted well away from. 


The aft tracker has a similarly wide arc.


The two Sea Wolf trackers together have perfect all round coverage.

Coverage is so good that even in the event that one tracker was not available,the ship would only need to make a minor change to it's course to keep targets within the arc of the other tracker.

This clearly illustrates the advantages of mounting weapons and sensors above the ship's superstructure.


This picture illustrates the combined weapon and sensor arcs of the Batch 3 Type 22 frigate.

Note how there is far better weapon and sensor coverage abeam of the ship than ahead or astern of it.

The ship must receive threats "beam on" to maximise it's weapon and sensor capabilities but this has the adverse effect of presenting a larger target with increased signature.

If the ship was designed to receive attacks from ahead,it's weapons and sensors would be distributed laterally to create overlaps forward and astern.

However,as ships are long and thin,this would create smaller arcs and less overall overlap.

The most practical solution is to design the vessel to receive attacks at an angle off centreline,allowing forward and aft weapons and sensors to be brought on target without presenting a broadside.


The above picture illustrates the combined sensor arcs of the Batch 3 Type 22 frigate.


The above picture illustrates the combined weapon firing arcs of the Batch 3 Type 22 frigate.

While every weapon system can fire abeam of the frigates,only the main gun and forward Sea Wolf system can fire ahead.

While the only weapon which can fire astern is the after Sea Wolf launcher.


The above picture illustrates the combined arcs of the complete Sea Wolf system air search radar.


This picture illustrates the firing arcs of the ship's guns.

While all guns can fire on the ship's beam,only the main gun can fire forward and no guns can fire aft.


This image illustrates the blind arc created by the unavailability of the aft Sea Wolf launcher.

Overlapping weapon and sensor arcs create redundancy which is an important aspect of survivability.


This image illustrates how the Sea Wolf tracker's higher position permits it a wider arc thanks to the narrower structures at higher levels.


This picture demonstrates how placing a weapon or sensor close to an obstruction,such as a mast,reduces it's arc.

Unlike the Goalkeeper,the Sea Wolf Tracker is mounted well forward of any obstruction and has a wide unobstructed arc.


Here we can again see the advantage gained by mounting weapons and sensors higher up where the ship's structures are narrower.


The Sea Wolf launcher has it's arc restricted by the width of the deck house atop the helicopter hangar,despite that structure having chamfered corners to minimise obstruction.


The higher mounted Sea Wolf tracker is obstructed only by the narrow masts and uptakes and consequently has a much wider arc.




Note how any mast,uptake or other structure positioned inside the red area will not further restrict weapon or sensor arcs.


To maximise weapon and sensor arcs,structures on a level which may cause obstruction to weapons and sensors should ideally be designed within a diamond plan form.


Due to advances in missile guidance,there will be no need for missile trackers on future warships.


A modern Stand Alone Defensive System may replace both Close In Weapon Systems and light cannon.


Most missiles will be carried in a vertical launch system with all round coverage.




The layout of a modern frigate might look like the above illustration.




This illustration shows the weapon and sensor arcs for such a warship.


Thanks to the vertical launch system,all bearings are covered by at least 2 weapon systems.


Most bearings are covered by 4 weapon systems.


This gives a very high degree of redundancy and reduces the ship's need to manoeuvre in combat.




This illustrations shows what such a vessel might look like from the side.