7-1 design of uav systems sorties ratesc 2002 lm corporation lesson objective - to discuss sortie...

7-1

Design of UAV Systems

Sorties rates c 2002 LM Corporation

Lesson objective - to discuss

Sortie rate analysis

including …

- Mission planning and preparation - Aircraft preparation and maintenance - Preflight / execution / debrief- Crew considerations

Expectations - You will understand the basic elements of a sortie and be able to make sortie rate estimates

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Definitions

Sortie (Webster’s New Collegiate Dictionary) – One mission by a single aircraft

Sortie rate (The RAND Corporation*) – The number of missions one aircraft can fly in

one day including time in the air and on the ground or

SR = 24hours/[FT + GT]where

FT = flight time 2target distance/block speedGT = ground time = TAT + MT

andTAT = turn around time 3 hoursMT = maintenance time

* http://www.rand.org/publications/MR/MR1028/

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Sortie elements

Mission planning and preparation time

• Military - time required to plan and communicate an overall air operation and translate it into individual aircraft flight plans that everybody understands

- Typically planned for days or weeks and conducted daily

• Civilian - time required to prepare and file a flight plan and receive a clearance- Manned aircraft can plan a simple flight and get an IFR clearance in a minimum of an hour- VFR flight preparations could be done in minutes

- Unmanned aircraft may have to negotiate approvals far in advance (varies by country and region)

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Sortie elements

Aircraft maintenance and preparation time

• All aircraft require servicing (fuel, oil, etc.), loading and scheduled maintenance (oil and filter change, etc)

- Servicing can often be done during mission planning- Loading time varies widely

- Military aircraft require special preparations to include weapons assembly and check out

- Minimum “turn time” is typically 15-30 minutes

• Unscheduled maintenance also occurs and often must be done before flights can be resumed

- Flight critical items must be fixed, others can be “placarded’ and fixed later

- Many operators do phase maintenance (periodic replacement) to minimize schedule disruptions

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Sortie elements

Pre-flight, loading and system checks

• All aircraft require external pre-flight ground checks

- From simple “walk-around” to thorough inspection- Typically takes 5 to 10 minutes

• All manned aircraft require loading

- Includes pilot, crew and passengers- Time varies from 1 minute (pilot only) to 30 minutes

• Non-perishable cargo can be loaded during aircraft maintenance and preparation

• All aircraft require pre-start system checks

- Unmanned aircraft require the most time - Minutes to hours

- Manned aircraft time varies from 1 to 15 minutes

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Sortie elements

Flying the mission….• Start/check the engine(s) - 1 to 5 minutes• Get ground clearances - seconds to minutes• Taxi to active runway - 2 to 15 minutes• Perform pre-takeoff checks - 0 to 5 minutes• Takeoff - 1 minute• Climb - Seconds to 10s of minutes• Cruise/ingress - function of mission distance & speed• Pre-penetration refuel - 15 to 30 minutes• Loiter/surveil - minutes to hours• Engage in combat - 2 to 5 minutes• Deliver cargo - minutes (drop) to hours (land)• Post-penetration refuel - 15 to 30 minutes

Cruise/egress - function of mission distance & speed• Get clearances and land - 1 to 10s of minutes• Post mission checks (military aircraft) - 0 to 5 minutes• Taxi and shut down - 2 to 15 minutes

oror

“UsefulWork”

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Sortie elements

Debrief - the time required to report and/or document the results of a mission

• Civilian debriefs focus on record keeping and incident and maintenance reports - 2 to 30 minutes

• Military debriefs are extensive- Everything included in civil debriefs plus …

- Mission assessments- Intelligence information- Procedures- Etc.

- Can take hours

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Crew considerations

• Civilian and peacetime military ground crews typically operate 8 hours per day, 5 days per week.

• Civilian air crews operate on flight hour basis• Air transport crews are typically limited to a 14 hour

duty day or 10 flight hours for reasons of safety- Duty day includes air and ground time

• On deployments, military air and ground crews operate 12 hours per day, 7 days per week- Crew:aircraft ratio usually > 1, e.g. 1.25 for fighters

• UAV crews (ground and flight) operate on 8 or 12 hour duty day basis

Aircraft sortie rates typically are limited by crew considerations - most aircraft can fly more hours than their crews can work - including UAVs

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Figures of merit

• Civilian figures of merit (FOM) are typically expressed in terms of numbers of revenue flights per day

• Military figures of merit are typically expressed in terms of numbers of sorties generated per day per aircraft (strike missions) or sorties for required coverage (surveillance missions) under 2 conditions:• Surge - what can be done in an “all-out” effort for

short periods of time• Sustained - what can be done in continuous effort

over long periods of time• Cost is an important part of military FOMs also

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Sortie rate example

Above completed in advance

Ground crew Mission ControlMission Planning and Preparation - min 180

Intelligence update 60Flight plan 60Clearances 60

Aircraft Preparation and Maintenance (parallel activity) - min 180

Scheduled maintenance 120Fuel/oil and roll out 30Ground checks 30

Above completed in advancePreflight - min 6 6

Load mission 2 2Mission verification 2 2

Walk around inspection and system checks 2 2

Mission execution - min 20 241Start engine 1 1Clearances 1 1Taxi 5 5

End of runway/pre-take off checks 3 3Takeoff 1Climb 10Cruise out 10

Loiter/surveillance 180Cruise back 10Hold for landing 5Land 5

Taxi 5 5Shut down 2 2

Quick turn - min 15 15“Thru flight” inspection and refuel 15

Reports 15

Sortie requirement (hr) 0.68 4.37

End of runway inspection and safing 33

SR = 24/7.37 = 3.3 FT = 3.6 hrs

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RAND data

* http://www.rand.org/publications/MR/MR1028/

Therefore:SR 24hours/[1.68FT + 6.4]

TAT 3 hrs

SR (previous example) = 1.9

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Intermission

7-1 design of uav systems sorties ratesc 2002 lm corporation lesson objective - to discuss sortie...

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