2 AimTo identify operational considerations for flight planning, and demonstrate the use of calculating Critical Points & Points of No-Return
3 Objectives Define the Critical Point Demonstrate method of Critical PointDefine the Point of No-ReturnDemonstrate method of PNRSummary of the above
4 1. Define Critical Point What is a Critical Point? Also known as Equi-Time Point - ETPIt is the point between departure & destination where it would take the same amount of time to proceed to destination or turn back.45min45minDepartureCritical PointDestinationIn nil wind where would the critical point be?In the middle!If there is wind, this will move the critical point into wind.
5 1. Define Critical Point What is a Critical Point? The equation for the critical point is:𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝐶𝑃= 𝑇𝑜𝑡𝑎𝑙 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ×𝐺𝑟𝑜𝑢𝑛𝑑 𝑆𝑝𝑒𝑒𝑑 𝐻𝑂𝑀𝐸 𝐺𝑆 𝑂𝑈𝑇+𝐺𝑆 𝐻𝑂𝑀𝐸Remember, ground speed will be affected with wind.Calculations for accurate ground speeds out & back must be calculated.Critical PointGS HomeGS OUTDepartureTotal DistanceDestination
7 2. Use of the CP Method Flying from YPPF to YMIA Total distance is 210nm20kt tail wind outbound from YPPF to YMIATAS = 120kts𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝐶𝑃= 𝑇𝑜𝑡𝑎𝑙 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ×𝐺𝑟𝑜𝑢𝑛𝑑 𝑆𝑝𝑒𝑒𝑑 𝐻𝑂𝑀𝐸 𝐺𝑆 𝑂𝑈𝑇+𝐺𝑆 𝐻𝑂𝑀𝐸𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝐶𝑃= 210× =87.5 𝑛𝑚Critical Point = 87.5nm from YPPFGS Home = 100 ktGS out = 140 ktYPPFTotal Distance = 210YMIA
8 2. Use of the CP When can we use this? Flights over water Flights in remote areasLong distance flightsDiversions due to weatherIncrease in situational awareness
9 3. Define the PNR What is the Point of No-Return? Also known as PNR, it is the point where there is insufficient fuel to return to departure aerodrome with reserves infact.The calculation is crucial on flights where aerodromes are limited such as remote areas or waterBeyond this point, if the aircraft turns back it will not be able to land with reserves infactdeparturePNRdestination
10 3. Define the PNR Considerations? The PNR is independent of the CP, as PNR is fuel consideration.The PNR will always be beyond the CP, because at the CP there must be fuel to either proceed or return, this is not the case with the PNRAny wind will reduce the dist to the PNR as in a tailwind due extra fuel burn to return, and in a headwind due extra fuel burn to go against winddepartureCPPNRdestination
12 𝑻 𝒐𝒖𝒕 𝒕𝒐 𝑷𝑵𝑹 = 𝑺 𝒉𝒐𝒎𝒆 𝑬𝒏𝒅 𝑺 𝒐𝒖𝒕 + 𝑺 𝒉𝒐𝒎𝒆 4. Demonstrating PNRPlanning method𝑻 𝒐𝒖𝒕 𝒕𝒐 𝑷𝑵𝑹 = 𝑺 𝒉𝒐𝒎𝒆 𝑬𝒏𝒅 𝑺 𝒐𝒖𝒕 + 𝑺 𝒉𝒐𝒎𝒆The Endurance is the amount of flight time left after having subtracted reserves, holding, taxi.Eg: 590 Lt total, 90lt FR, 15lt taxi, 0Lt holding, variable reserve 15%Total Fuel AVAILABLE for flight = 421 Litres to use for a 100lt/hr = 4.2hoursIf TAS is 180kts, wind is 20kt tailwind outbound, fuel flow is 100lt/hr how long will it take to reach the PNR?𝑻 𝒐𝒖𝒕 𝒕𝒐 𝑷𝑵𝑹 = 𝟏𝟔𝟎×𝟒.𝟐 𝟐𝟎𝟎+𝟏𝟔𝟎 =𝟏.𝟖𝟕 𝒉𝒐𝒖𝒓𝒔 𝒕𝒐 𝑷𝑵𝑹With the above, how many nautical miles is the PNR from departure?Distance to PNR = 1.87 hrs X 200 kts outbound = 374 nmGS out =200ktWind +20kts taildepartureGS home =160ktPNRdestination
13 4. Demonstrating PNR Practical method The previous example is useful for planning purposes. However this is not always the case for ‘actual flight’Why is this?Fuel flows may change depending on the operationsEg: If the pilot changes cruise settings, altitudes due unexpected weather, go arounds, the overall fuel flows will be different!Eg: Flying at 180kts, with 20kts tailwind outbound, fuel available for PNR = 340 Lt, fuel flow 100lt/hr𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 𝑜𝑢𝑡 = 100 𝑙𝑡/ℎ𝑟 200𝑘𝑡𝑠 =0.5 𝑙𝑡/𝑔𝑛𝑚Therefore, for every ground nautical mile flown, the aircraft burns 0.5 litres outbound𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 ℎ𝑜𝑚𝑒 = 100 𝑙𝑡/ℎ𝑟 160𝑘𝑡𝑠 =0.625 𝑙𝑡/𝑔𝑛𝑚𝑫𝒊𝒔𝒕 𝒕𝒐 𝑷𝑵𝑹 𝒏𝒎 = 𝑭𝒖𝒆𝒍 𝑨𝒗𝒂𝒊𝒍𝒂𝒃𝒍𝒆 (𝒍𝒕) 𝑻𝒐𝒕𝒂𝒍 𝑩𝒖𝒓𝒏 𝒓𝒂𝒕𝒆𝒔 𝑮𝑺 𝒐𝒖𝒕 + 𝑮𝑺 𝒉𝒐𝒎𝒆 𝒍𝒕/𝒈𝒏𝒎= =302𝑛𝑚
14 4. Demonstrating PNR Practical method – Engine failure Eg: Outbound TAS = 180kts, fuel flow 100lt/hr, total fuel 500lt, wind 30kts headwind outboundEngine failure TAS = 120kts, fuel flow 60lt/hrHow far from departure is the PNR?Fuel available for PNR = 500 – 90rsv – 15taxi – 15%vbr = 343 Litres𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 𝑜𝑢𝑡 = 100 𝑙𝑡/ℎ𝑟 150𝑘𝑡𝑠 =0.667 𝑙𝑡/𝑔𝑛𝑚𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 ℎ𝑜𝑚𝑒 = 60 𝑙𝑡/ℎ𝑟 150𝑘𝑡𝑠 =0.4 𝑙𝑡/𝑔𝑛𝑚𝑫𝒊𝒔𝒕 𝒕𝒐 𝑷𝑵𝑹 𝒏𝒎 = 𝑭𝒖𝒆𝒍 𝑨𝒗𝒂𝒊𝒍𝒂𝒃𝒍𝒆 (𝒍𝒕) 𝑻𝒐𝒕𝒂𝒍 𝑩𝒖𝒓𝒏 𝒓𝒂𝒕𝒆𝒔 𝑮𝑺 𝒐𝒖𝒕 + 𝑮𝑺 𝒉𝒐𝒎𝒆 𝒍𝒕/𝒈𝒏𝒎 = =321𝑛𝑚 from departureGS out =150ktWind – 30kts headdepartureGS home =150ktPNRdestination
15 4. Demonstrating PNR Practical method – Climbing considerations If climbing, take into account the fuel used in climb/descent.Eg: Outbound TAS = 180kts, fuel flow 100lt/hr, total fuel 516lt, wind 30kts tailwind outboundEngine failure TAS = 120kts, fuel flow 60lt/hrClimb fuel = 20lt & 35nmHow far from departure is the PNR?Fuel available for PNR =516 – 90rsv – 15taxi – 15%vbr = 358 Lt for flightSubtract the climb & descent fuelDescent (approx) = (0.667 x 35nm) = 24lt358 – 20lt climb – 24lt descent = 314 lt for PNR277nm + 35nm = 312nm from departure aerodrome𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 𝑜𝑢𝑡 = 100 𝑙𝑡/ℎ𝑟 210𝑘𝑡𝑠 =0.476 𝑙𝑡/𝑔𝑛𝑚𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 ℎ𝑜𝑚𝑒 = 60 𝑙𝑡/ℎ𝑟 90𝑘𝑡𝑠 =0.667 𝑙𝑡/𝑔𝑛𝑚𝑫𝒊𝒔𝒕 𝒕𝒐 𝑷𝑵𝑹 𝒏𝒎 = 𝑭𝒖𝒆𝒍 𝑨𝒗𝒂𝒊𝒍𝒂𝒃𝒍𝒆 (𝒍𝒕) 𝑻𝒐𝒕𝒂𝒍 𝑩𝒖𝒓𝒏 𝒓𝒂𝒕𝒆𝒔 𝑮𝑺 𝒐𝒖𝒕 + 𝑮𝑺 𝒉𝒐𝒎𝒆 𝒍𝒕/𝒈𝒏𝒎==277𝑛𝑚 from TopCGS out =210kt20ltWind +30kts tailGS home =90ktdeparture277nmPNRdestination35nm
16 4. Demonstrating PNR Practical method – Enroute Enroute made from a positive fix & similar to the climb/descent, subtract the outbound/inbound fuel.Eg: Outbound/inbound TAS = 180kts, fuel flow 100lt/hr, total fuel 516lt, wind 20kts tailwind outboundPositive fix = 80nm from departureHow far from departure is the PNR?Fuel available for PNR =516 – 90rsv – 15taxi – 15%vbr = 358 Lt for flightSubtract outbound & inbound fueloutbound (approx) = (0.5 x 80nm) = 40ltInbound (approx) = (0.588 x 80nm) = 47lt358 – 40 – 47 = 271lt for PNR from fix249nm + 80nm = 329nm from departure aerodrome𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 𝑜𝑢𝑡 = 100 𝑙𝑡/ℎ𝑟 200𝑘𝑡𝑠 =0. 5𝑙𝑡/𝑔𝑛𝑚𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤 𝐺𝑆 ℎ𝑜𝑚𝑒 = 100 𝑙𝑡/ℎ𝑟 170𝑘𝑡𝑠 =0. 588𝑙𝑡/𝑔𝑛𝑚𝑫𝒊𝒔𝒕 𝒕𝒐 𝑷𝑵𝑹 𝒏𝒎 = 𝑭𝒖𝒆𝒍 𝑨𝒗𝒂𝒊𝒍𝒂𝒃𝒍𝒆 (𝒍𝒕) 𝑻𝒐𝒕𝒂𝒍 𝑩𝒖𝒓𝒏 𝒓𝒂𝒕𝒆𝒔 𝑮𝑺 𝒐𝒖𝒕 + 𝑮𝑺 𝒉𝒐𝒎𝒆 𝒍𝒕/𝒈𝒏𝒎==249𝑛𝑚 from fixGS out =200ktWind +20kts tail40 ltGS home =170ktdeparture47 lt249nmPNRdestination80nm
17 4. Demonstrating PNR Summary of PNR departure PNR destination Cruise out & back PNR for planningdeparturePNRdestinationCruise out return asymmetric (lower alt)departurePNRdestinationTopCPlanned PNR out & return with climb/descentTopDdeparturePNRdestinationOutbound fuelInflight PNR out & return from positive fixdepartureInbound fuelPNRdestination
18 5. Summary Summary of PNR vs CP/ETP The distance to the PNR depends on the flight fuel available Changes to reserves, variable reserves, holding, airwork etcDistance to the CP/ETP is independent of flight fuel.The only time fuel is to be considered is if the pilot wishes to know how much fuel will be burnt passed the ETPOnce past the PNR the aircraft will not be able to return to the departure airport with full reserves/fuel intactIf the aircraft returns to departure at the ETP he/she will have reserves & excess fuel intact
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