We have discussed the over capacity if the Royal Air Force's Future Strategic Tanker Aircraft (F.S.T.A) project in an earlier post.
We pointed out that demand for tanker aircraft was declining significantly while F.S.T.A. was committing the British taxpayer to fund massive overcapacity at vast expense until 2035.
We suggested that Britain needed only 6 or 7 A330 tanker transport aircraft.
We also suggested that these should have been bought outright.
We did not go into detail about that number.
We shall do so here.
The cost to the taxpayer of the air refuelling fleet is defined by the capacity which must be maintained in peacetime.
The air refuelling capacity must satisfy peak air refuelling demand.
Peak air refuelling demand occurs during major war fighting operations.
The last time Britain was engaged in a major war fighting operation was during the 2003 invasion of Iraq,known as Operation Telic or Iraqi Freedom.
Developments in weapons and sensors,the Royal Navy's new aircraft carriers,reductions in the size of British military aircraft fleet and longer ranged aircraft entering service all suggest that future peak air refuelling demand will be significantly less than it was in 2003.
Let us look at what was needed in 2003.
Let us look at what was needed in 2003.
The United States Air Force (U.S.A.F.) publication "Operation IRAQI FREEDOM – By The Numbers" gives statistics for the 31 days of the air war during the Iraq invasion.
It says that the Royal Air Force deployed 12 air refuelling tankers for Operation Telic/Iraqi Freedom,these flew 359 sorties and offloaded 18,884,000 pounds of fuel.
The latter figure is listed under the phrase "coalition" but as no other coalition country is listed as providing aerial refuelling aircraft this must presumably have been delivered by the Royal Air Force.
In Chapter 6 of a "Short History of the Royal Air Force","RETURN TO EXPEDITIONARY WARFARE",the following figures were given for the British aerial refuelling effort during the Iraq invasion:
"The AAR (Air to Air Refuelling) capability contributed by the RAF was highly valued,particularly by the
Americans.
VC10s and Tristars flew 355 sorties dispensing nearly 19 million lbs of fuel.
Over 40% of this was given to US Navy and Marine Corps aircraft.*"
*Aircraft of the United States Air Force are unable to receive fuel from the "hose and drogue" equipped British tanker aircraft.
These numbers are almost identical to those given by the United States Air Force.
The Royal Air Force contribution amounted to about 4.5% of the coalition aerial refuelling effort which offloaded a total of 417,137,233 pounds of fuel.
A summary of the relevant figures is as follows:
Number of refuelling aircraft.
United States Air Force 182
United States Marine Corps 22
United States Navy 52
Royal Air Force 12 (4.5%)
Total 268
Number of Refuelling Sorties Flown.
United States Air Force 6,193
United States Marine Corps 454
United States Navy 2,058
United States Navy 2,058
Royal Air Force 359 (4%)
Total 9,064
Pounds of fuel offloaded.
United States Air Force 376,391,000
United States Marine Corps 12,545,786
United States Marine Corps 12,545,786
United States Navy 9,316,447
Coalition (Royal Air Force) 18,884,000 (4.5%)
Total 417,137,233
Using the more precise American figures we get a total of 8,584 tonnes of fuel offloaded by British tanker aircraft in 359 sorties during 31 days of combat operations.
An average of 277 tonnes offloaded per day by an average of 11.6 daily tanker sorties.
This is an average of 0.97 sorties per tanker aircraft per day*.
An average of 23.9 tonnes of fuel was offloaded per sortie.
An average of 23.1 tonnes of fuel was offloaded per aircraft per day.
Only 60% of the above was offloaded to British military aircraft.
*This figure is higher than that achieved by Royal Air Force combat aircraft during operation Telic.
The Royal Air Force often generates far lower sortie rates than other air arms and air forces.
However,Royal Air Force tanker aircraft often generate far higher sortie rates than other elements of the Royal Air Force.
Unfortunately none of the above figures gives any indication of where the fuel was offloaded.
For the receiving aircraft,the important metric in aerial refuelling is the weight of fuel received and the distance from the operating area at which it is received.
Fuel received close to the operating area is of more benefit than fuel received far from the combat area.
It is important to note that the range from the tanker aircraft's base is of no relevance at all to this.
This gives us a problem when comparing the performance of aerial refuelling aircraft.
The most obvious and easily compared metric is the fuel the tanker aircraft can offload at a given range from it's base.
But as it is the distance from the combat aircraft's operating area at which the fuel is transferred which is important,this figure is of no benefit.
A smaller tanker aircraft which can generate a large number of daily sorties from an aircraft carrier or shorter runway on a base closer to where the fuel offload is needed may be of more benefit than a large tanker aircraft which can fly fewer sorties from a more distant base with a long runway.
It is essential to consider where the tanker aircraft can operate from and where the fuel offload is needed.
This dictates how far the tanker aircraft must fly on each sortie and thus how many sorties it can generate in a day,how much fuel it will burn on each sortie and how much it will have left to transfer to the receiving aircraft.
For example,an A400M tanker may carry only half as much fuel as an A330 tanker (58 tonnes versus 111 tonnes) but it might be based much closer to it's tanker track as it does not require a 10,000 foot runway.
Thus a small carrier based tanker aircraft or a rough field capable tanker convertible A400M might be more cost effective options than a large long runway A330 tanker aircraft - depending on the basing options available.
However,as the A330 tankers are already in production,we shall consider only them here.
During the Iraq invasion,British tanker aircraft (probably 4 Tristars and 8 VC10s) operated from Al Udeid in Qatar,as did most British military aircraft.
Al Udeid is about 400 miles from the border of Iraq.
As orbiting tanker aircraft are highly vulnerable we may assume that the tanker orbits (an image of a tanker orbit can be seen here) were some distance South of the Iraqi border during initial combat operations at least.
They later moved further North as the threat declined later on.
This would place the tanker orbits perhaps about 350 nautical miles North of Al Udeid initially,distances increasing later in the conflict.
An A330 tanker can deliver 60 tonnes of fuel at 500 nautical miles from base with 5 hours on station.
At shorter ranges it can offload far more fuel than that.
The average of 277 tonnes offloaded per day by the Royal Air Force Tristars and VC10s could probably be delivered by about 4 daily A330 tanker sorties.
Assuming the A330 generates the same sortie rates as the Tristars and VC10s managed,we would probably require only 4 A330 tanker aircraft to generate the offload capacity delivered by 12 tanker aircraft in 2003.
Assuming 80% availability of the A330 fleet,we would require a fleet of just 5 A330s to satisfy peak tanker demand during major war fighting operations.
If we were to exclude the 40% of the British tanker capacity which was not offloaded to British aircraft in 2003,the requirement would be for about 2.5 A330 tanker sorties per day.
This could be provided by a total fleet of just 3 A330 tankers.
As we said earlier,future tanker demand is likely to be far lower than it was in 2003,with longer ranged aircraft like F35C replacing the short ranged Harrier and new aircraft carriers usually allowing them to be based closer to the combat area.
Buying tanker conversion kits for A400Ms and F35Cs would reduce demand for dedicated tanker aircraft still further.
Even allowing for aircraft undergoing maintenance,and on transport tasks,there appears to be no need for more than half the 14 A330 tankers which will be provided under the F.S.T.A. contract.
Unfortunately none of the above figures gives any indication of where the fuel was offloaded.
For the receiving aircraft,the important metric in aerial refuelling is the weight of fuel received and the distance from the operating area at which it is received.
Fuel received close to the operating area is of more benefit than fuel received far from the combat area.
It is important to note that the range from the tanker aircraft's base is of no relevance at all to this.
This gives us a problem when comparing the performance of aerial refuelling aircraft.
The most obvious and easily compared metric is the fuel the tanker aircraft can offload at a given range from it's base.
But as it is the distance from the combat aircraft's operating area at which the fuel is transferred which is important,this figure is of no benefit.
A smaller tanker aircraft which can generate a large number of daily sorties from an aircraft carrier or shorter runway on a base closer to where the fuel offload is needed may be of more benefit than a large tanker aircraft which can fly fewer sorties from a more distant base with a long runway.
It is essential to consider where the tanker aircraft can operate from and where the fuel offload is needed.
This dictates how far the tanker aircraft must fly on each sortie and thus how many sorties it can generate in a day,how much fuel it will burn on each sortie and how much it will have left to transfer to the receiving aircraft.
For example,an A400M tanker may carry only half as much fuel as an A330 tanker (58 tonnes versus 111 tonnes) but it might be based much closer to it's tanker track as it does not require a 10,000 foot runway.
This reduces fuel burn in transit,and fuel burn on station for the smaller A400M is also less leaving more fuel for offloading.
With each sortie taking less time,more sorties can be flown in a day,off setting the capacity deficit of the smaller aircraft.
The lower overall fuel consumption also reduces the logistical burden on the ground.
Thus a small carrier based tanker aircraft or a rough field capable tanker convertible A400M might be more cost effective options than a large long runway A330 tanker aircraft - depending on the basing options available.
However,as the A330 tankers are already in production,we shall consider only them here.
During the Iraq invasion,British tanker aircraft (probably 4 Tristars and 8 VC10s) operated from Al Udeid in Qatar,as did most British military aircraft.
Al Udeid is about 400 miles from the border of Iraq.
As orbiting tanker aircraft are highly vulnerable we may assume that the tanker orbits (an image of a tanker orbit can be seen here) were some distance South of the Iraqi border during initial combat operations at least.
They later moved further North as the threat declined later on.
This would place the tanker orbits perhaps about 350 nautical miles North of Al Udeid initially,distances increasing later in the conflict.
An A330 tanker can deliver 60 tonnes of fuel at 500 nautical miles from base with 5 hours on station.
At shorter ranges it can offload far more fuel than that.
The average of 277 tonnes offloaded per day by the Royal Air Force Tristars and VC10s could probably be delivered by about 4 daily A330 tanker sorties.
Assuming the A330 generates the same sortie rates as the Tristars and VC10s managed,we would probably require only 4 A330 tanker aircraft to generate the offload capacity delivered by 12 tanker aircraft in 2003.
Assuming 80% availability of the A330 fleet,we would require a fleet of just 5 A330s to satisfy peak tanker demand during major war fighting operations.
If we were to exclude the 40% of the British tanker capacity which was not offloaded to British aircraft in 2003,the requirement would be for about 2.5 A330 tanker sorties per day.
This could be provided by a total fleet of just 3 A330 tankers.
As we said earlier,future tanker demand is likely to be far lower than it was in 2003,with longer ranged aircraft like F35C replacing the short ranged Harrier and new aircraft carriers usually allowing them to be based closer to the combat area.
Buying tanker conversion kits for A400Ms and F35Cs would reduce demand for dedicated tanker aircraft still further.
Even allowing for aircraft undergoing maintenance,and on transport tasks,there appears to be no need for more than half the 14 A330 tankers which will be provided under the F.S.T.A. contract.
