Critical Pts & Pts of No Return ATC Chapter 5 Aim To identify operational considerations for flight planning, and demonstrate the use of calculating Critical.
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Critical Pts & Pts of No Return ATC Chapter 5 Aim To identify operational considerations for flight planning, and demonstrate the use of calculating Critical Points & Points of No-Return Objectives 1. 2. 3. 4. 5. Define the Critical Point Demonstrate method of Critical Point Define the Point of No-Return Demonstrate method of PNR Summary of the above 1. Define Critical Point What is a Critical Point? Also known as Equi-Time Point - ETP It is the point between departure & destination where it would take the same amount of time to proceed to destination or turn back. 45min 45min Departure Critical Point In nil wind where would the critical point be? In the middle! If there is wind, this will move the critical point into wind. Destination 1. Define Critical Point What is a Critical Point? The equation for the critical point is: ๐๐๐ก๐๐ ๐ท๐๐ ๐ก๐๐๐๐ × ๐บ๐๐๐ข๐๐ ๐๐๐๐๐ ๐ป๐๐๐ธ ๐ท๐๐ ๐ก๐๐๐๐ ๐ก๐ ๐ถ๐ = ๐บ๐ ๐๐๐ + ๐บ๐ ๐ป๐๐๐ธ Remember, ground speed will be affected with wind. Calculations for accurate ground speeds out & back must be calculated. Critical Point GS OUT GS Home Departure Total Distance Destination 1. Define Critical Point How is the CP derived? The CP is the point where; ๐๐ป๐๐๐ธ = ๐๐๐๐ ๐ท๐ด ๐โ๐๐๐ = ๐ท๐ต ๐๐๐ข๐ก ๐ท๐ด ๐โ๐๐๐ , where DB = Dtotal โ DA = ๐ท๐๐๐ก๐๐ โ ๐ท๐ด ๐๐๐ข๐ก multiply both sides by Shome & Sout ๐ท๐ด ๐โ๐๐๐ ๐โ๐๐๐ . ๐๐๐ข๐ก = ๐ท๐๐๐ก๐๐ โ ๐ท๐ด ๐โ๐๐๐ . ๐๐๐ข๐ก ๐๐๐ข๐ก ๐ท๐ด . ๐๐๐ข๐ก = ๐ท๐๐๐ก๐๐ . ๐โ๐๐๐ โ๐ท๐ด . ๐โ๐๐๐ ๐ท๐ด . ๐๐๐ข๐ก +๐ท๐ด . ๐โ๐๐๐ = ๐ท๐๐๐ก๐๐ . ๐โ๐๐๐ ๐ท๐ด (๐๐๐ข๐ก +๐โ๐๐๐ ) = ๐ท๐๐๐ก๐๐ . ๐โ๐๐๐ ๐ซ๐จ = (๐ซ๐ป๐๐๐๐ × ๐บ๐๐๐๐ ) (๐บ๐๐๐ +๐บ๐๐๐๐ ) 2. Use of the CP Method Flying from YPPF to YMIA Total distance is 210nm 20kt tail wind outbound from YPPF to YMIA TAS = 120kts ๐ท๐๐ ๐ก๐๐๐๐ ๐ก๐ ๐ถ๐ = ๐๐๐ก๐๐ ๐ท๐๐ ๐ก๐๐๐๐ × ๐บ๐๐๐ข๐๐ ๐๐๐๐๐ ๐ป๐๐๐ธ ๐บ๐ ๐๐๐ + ๐บ๐ ๐ป๐๐๐ธ ๐ท๐๐ ๐ก๐๐๐๐ ๐ก๐ ๐ถ๐ = 210 × 100 = 87.5 ๐๐ 140 + 100 Critical Point = 87.5nm from YPPF GS Home = 100 kt YPPF GS out = 140 kt Total Distance = 210 YMIA 2. Use of the CP When can we use this? โข โข โข โข โข Flights over water Flights in remote areas Long distance flights Diversions due to weather Increase in situational awareness 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 water Beyond this point, if the aircraft turns back it will not be able to land with reserves infact departure PNR destination 3. Define the PNR Considerations? โข The PNR is independent of the CP, as PNR is fuel consideration. โข 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 PNR โข Any 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 wind departure CP PNR destination 3. Define the PNR How is the PNR derived? The PNR is the point where; ๐ท๐๐ข๐ก ๐ก๐ ๐๐๐ = ๐ทโ๐๐๐ ๐ก๐ ๐๐๐ ๐๐๐ข๐ก × ๐๐๐ข๐ก = ๐โ๐๐๐ × ๐โ๐๐๐ where THome = Endurance Available โ TOUT ๐๐๐ข๐ก × ๐๐๐ข๐ก = ๐โ๐๐๐ ๐ธ๐๐ โ ๐๐๐ข๐ก ๐๐๐ข๐ก ๐๐๐ข๐ก = ๐โ๐๐๐ ๐ธ๐๐ โ ๐โ๐๐๐ ๐๐๐ข๐ก ๐๐๐ข๐ก ๐๐๐ข๐ก + ๐โ๐๐๐ ๐๐๐ข๐ก = ๐โ๐๐๐ ๐ธ๐๐ ๐๐๐ข๐ก ๐๐๐ข๐ก + ๐โ๐๐๐ = ๐โ๐๐๐ ๐ธ๐๐ ๐ป๐๐๐ ๐๐ ๐ท๐ต๐น = ๐บ๐๐๐๐ ๐ฌ๐๐ ๐บ๐๐๐ + ๐บ๐๐๐๐ 4. Demonstrating PNR Planning method ๐ป๐๐๐ ๐๐ ๐ท๐ต๐น = ๐บ๐๐๐๐ ๐ฌ๐๐ ๐บ๐๐๐ + ๐บ๐๐๐๐ The 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 PNR, @ 100lt/hr = 4.2hours If TAS is 180kts, wind is 20kt tailwind outbound, fuel flow is 100lt/hr how long will it take to reach the PNR? ๐๐๐ × ๐. ๐ ๐ป๐๐๐ ๐๐ ๐ท๐ต๐น = = ๐. ๐๐ ๐๐๐๐๐ ๐๐ ๐ท๐ต๐น ๐๐๐ + ๐๐๐ With the above, how many nautical miles is the PNR from departure? Distance to PNR = 1.87 hrs X 200 kts outbound = 374 nm GS out =200kt Wind ๏ +20kts tail departure GS home =160kt PNR destination 4. Demonstrating PNR Practical method The previous example is useful for planning purposes. However this is not always the case for โactual flightโ Why is this? โข Fuel flows may change depending on the operations o Eg: 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/hr ๐น๐ข๐๐ ๐น๐๐๐ค 100 ๐๐ก/โ๐ = = 0.5 ๐๐ก/๐๐๐ ๐บ๐๐๐ข๐ก 200๐๐ก๐ Therefore, for every ground nautical mile flown, the aircraft burns 0.5 litres outbound ๐น๐ข๐๐ ๐น๐๐๐ค 100 ๐๐ก/โ๐ = = 0.625 ๐๐ก/๐๐๐ ๐บ๐โ๐๐๐ 160๐๐ก๐ ๐ซ๐๐๐ ๐๐ ๐ท๐ต๐น ๐๐ = ๐ญ๐๐๐ ๐จ๐๐๐๐๐๐๐๐ (๐๐) ๐ป๐๐๐๐ ๐ฉ๐๐๐ ๐๐๐๐๐ ๐ฎ๐บ๐๐๐ + ๐ฎ๐บ๐๐๐๐ ๐๐/๐๐๐ = 340 = 302๐๐ 0.5 + 0.625 4. Demonstrating PNR Practical method โ Engine failure Eg: Outbound TAS = 180kts, fuel flow 100lt/hr, total fuel 500lt, wind 30kts headwind outbound Engine failure TAS = 120kts, fuel flow 60lt/hr How far from departure is the PNR? Fuel available for PNR = 500 โ 90rsv โ 15taxi โ 15%vbr = 343 Litres ๐น๐ข๐๐ ๐น๐๐๐ค ๐บ๐๐๐ข๐ก = 100 ๐๐ก/โ๐ 150๐๐ก๐ = 0.667 ๐๐ก/๐๐๐ ๐น๐ข๐๐ ๐น๐๐๐ค 60 ๐๐ก/โ๐ = = 0.4 ๐๐ก/๐๐๐ ๐บ๐โ๐๐๐ 150๐๐ก๐ ๐ซ๐๐๐ ๐๐ ๐ท๐ต๐น ๐๐ = ๐ญ๐๐๐ ๐จ๐๐๐๐๐๐๐๐ (๐๐) ๐ป๐๐๐๐ ๐ฉ๐๐๐ ๐๐๐๐๐ ๐ฎ๐บ๐๐๐ +๐ฎ๐บ๐๐๐๐ ๐๐/๐๐๐ GS out =150kt departure GS home =150kt = 343 0.667+0.4 = 321๐๐ from departure Wind ๏ โ 30kts head PNR destination 4. Demonstrating PNR Practical method โ 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 outbound Engine failure TAS = 120kts, fuel flow 60lt/hr ๐น๐ข๐๐ ๐น๐๐๐ค 100 ๐๐ก/โ๐ Climb fuel = 20lt & 35nm = = 0.476 ๐๐ก/๐๐๐ ๐บ๐๐๐ข๐ก 210๐๐ก๐ How far from departure is the PNR? ๐น๐ข๐๐ ๐น๐๐๐ค 60 ๐๐ก/โ๐ = = 0.667 ๐๐ก/๐๐๐ ๐บ๐โ๐๐๐ 90๐๐ก๐ Fuel available for PNR = 516 โ 90rsv โ 15taxi โ 15%vbr = 358 Lt for flight ๐ซ๐๐๐ ๐๐ ๐ท๐ต๐น ๐๐ = Subtract the climb & descent fuel Descent (approx) = (0.667 x 35nm) = 24lt 358 โ 20lt climb โ 24lt descent = 314 lt for PNR 277nm + 35nm = 312nm from departure aerodrome GS out =210kt 20lt ๐ญ๐๐๐ ๐จ๐๐๐๐๐๐๐๐ (๐๐) ๐ป๐๐๐๐ ๐ฉ๐๐๐ ๐๐๐๐๐ ๐ฎ๐บ๐๐๐ + ๐ฎ๐บ๐๐๐๐ ๐๐/๐๐๐ 314 0.476 + 0.667 = 277๐๐ from TopC = Wind ๏ +30kts tail GS home =90kt departure 277nm 35nm PNR destination 4. Demonstrating PNR Practical method โ 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 outbound Positive fix = 80nm from departure ๐น๐ข๐๐ ๐น๐๐๐ค 100 ๐๐ก/โ๐ = 200๐๐ก๐ = 0. 5๐๐ก/๐๐๐ ๐บ๐ ๐๐ข๐ก How far from departure is the PNR? ๐น๐ข๐๐ ๐น๐๐๐ค 100 ๐๐ก/โ๐ = = 0. 588๐๐ก/๐๐๐ ๐บ๐โ๐๐๐ 170๐๐ก๐ Fuel available for PNR = 516 โ 90rsv โ 15taxi โ 15%vbr = 358 Lt for flight ๐ซ๐๐๐ ๐๐ ๐ท๐ต๐น ๐๐ = Subtract outbound & inbound fuel outbound (approx) = (0.5 x 80nm) = 40lt Inbound (approx) = (0.588 x 80nm) = 47lt 358 โ 40 โ 47 = 271lt for PNR from fix 249nm + 80nm = 329nm from departure aerodrome GS out =200kt 40 lt departure 47 lt 80nm ๐ญ๐๐๐ ๐จ๐๐๐๐๐๐๐๐ (๐๐) ๐ป๐๐๐๐ ๐ฉ๐๐๐ ๐๐๐๐๐ ๐ฎ๐บ๐๐๐ + ๐ฎ๐บ๐๐๐๐ ๐๐/๐๐๐ 271 0.5 + 0.588 = 249๐๐ from fix = Wind ๏ +20kts tail GS home =170kt 249nm PNR destination 4. Demonstrating PNR Summary of PNR Cruise out & back PNR for planning departure PNR destination Cruise out return asymmetric (lower alt) departure PNR destination TopC Planned PNR out & return with climb/descent TopD departure PNR Inflight PNR out & return from positive fix Outbound fuel departure Inbound fuel destination PNR destination 5. Summary Summary of PNR vs CP/ETP โข โข โข The distance to the PNR depends on the flight fuel available Changes to reserves, variable reserves, holding, airwork etc Distance to the CP/ETP is independent of flight fuel. โข The only time fuel is to be considered is if the pilot wishes to know how much fuel will be burnt passed the ETP Once past the PNR the aircraft will not be able to return to the departure airport with full reserves/fuel intact โข If the aircraft returns to departure at the ETP he/she will have reserves & excess fuel intact Questions?