A sortie represents one flight by one aircraft.
A sortie rate is the number of sorties which an aircraft (or a group of aircraft) can fly in a day.
The lower the sortie rate,the greater the number of aircraft that will be needed to generate the required number of sorties in a given time.
The greater the number of aircraft needed,the greater the cost.
Sorties flown by combat aircraft may be split into two types,delivery sorties and persistent sorties.
Delivery sorties may include bombing sorties,transport sorties,reconnaissance sorties and tanker sorties.
The objective of a delivery sortie is to deliver bombs,cargo or fuel or gather intelligence and then return to base.
The shorter the time it takes to fly a delivery sortie and turn the aircraft round for the next sortie,the greater the number of sorties which may be flown in a day by a given number of aircraft.
Flying more delivery sorties per aircraft delivers more bombs,cargo,fuel or gathers more intelligence for a given expenditure on aircraft.
The objective of persistent sorties is to keep an aircraft on station for a given period of time.
Persistent sorties may include,surveillance sorties,fighter patrol sorties and close air support sorties.
Time on station is the the duration of the sortie minus the time taken to transit to and from the operational area.
Longer sortie duration and shorter transit times give more aircraft on station in the operational area for a given number of aircraft and hence for a given cost.
Note that reducing the distance between the operating base and the operational area both increases sortie rates for delivery sorties and increases time on station for persistent sorties.
For the basic mathematics associated with sortie generation see here:
www.rand.org/pubs/monograph_reports/MR1028/MR1028.appb.pdf
It will be noted that the sortie rate is determined by both the length of time it takes to fly the sortie,flight time,and the time it takes to prepare the aircraft for the next sortie,ground time.
We shall refer to the combination of these two factors as cycle time.
Ground time can be divided into the time taken to perform routine tasks between sorties,turn around time,and the time taken to perform maintenance to the aircraft,maintenance time.
The flight time is a factor of the speed of the aircraft,the distance to the target and the time on station.
A slow aircraft flying a long distance to the operational area and spending a long time on station will result in a long flight time.
A fast aircraft flying a short distance to the operational area and spending little time on station will result in a short flight time.
The maintenance time depends on the flight time,the aircraft type and the environment in which the maintenance is being done.
An aircraft which flies long sorties,requires many maintenance hours per flight hour and is maintained by unmotivated,tired personnel working in difficult conditions is going to spend a long time undergoing maintenance between sorties.
An aircraft which flies short sorties,requires few maintenance hours per flight hour and is maintained by well motivated,energetic personnel working in ideal conditions is going to spend very little time undergoing maintenance between sorties.
The turnaround time is a factor of the base from which the aircraft is operating and the armament which muct be loaded on the aircraft.
An aircraft at a large crowded,improvised expeditionary airfield (expeditionary airfields are neccessarily two dimensional,dispersed,unsuited to automattion and hence manpower intensive),requiring a large complex weapon load may spend a lot of time taxiing,waiting and being armed.
An aircraft on a purpose built aircraft carrying ship (aircraft carriers are neccessarily compact,three dimensional,well suited to automation and hence can be very manpower efficient),requiring a minimal weapon load may spend very little time taxiing,waiting and being armed.
It follows from the above that aircraft flying from aircraft carriers stationed close to the operational area will generate higher sortie rates than those based at expeditionary airfield further away.
However,if the expeditionary airfield is significantly closer to the operational area than the aircraft carrier then shorter flight times may offset the generally longer turnaround times of the land base.
Whichever basing option which,through it's combination of efficiency and shorter distance to target,offers the higher sortie rate will allow more air power to be delivered by fewer aircraft.
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