PPRuNe Forums > PPRuNe Worldwide > South Asia and the Far East > Nav Questions help !! PDA View Full Version : Nav Questions help !! ginaviator10th Apr 2012, 14:27Hello Aviators, Please help me to solve few Nav Questions. I am preparing for the DGCA CPL Exams. I have a answers, but not able to solve the given questions. Q1. F/L 350, TAT -11 C, Temp dev from ISA +20, Find out OAT & TAS? Answer : OAT - 35 & TAS = 490 Q2. F/L 350, TAS 450 K, TAT -11C, Find the Temp dev from ISA? Answer : +24 Degree C Q3. On a Cross country you are flying on Magnetic Track of 090, Var is 2 W, The Flt level to fly is ? Answer : 75 Q4. Earth Convergency btw two points 8 deg long apart is 7.2 deg on the same parallel of lat P is 173W & Q is 176 E Find. a) G/C bearing of P from Q in NH b) G/C bearing of Q from P in SH Answer : 085 & 265 Thanks gAMbl311th Apr 2012, 08:20Q1. F/L 350, TAT -11 C, Temp dev from ISA +20, Find out OAT & TAS? In ISA temp at FL 360 = -56.5 C and lapse rate = 2 C/ 1000 ft. So temp at FL 350 in ISA = -56.5 + 2 = -54.5 C Temp deviation = ISA + 20 Therefore temp at FL 350 (OAT) = -54.5 + 20 = -34.5 C OAT = TAT - (TAS/100)^2 -34.5 = -11 - (TAS/100)^2 23.5 = (TAS/100)^2 TAS = 485 kts. gAMbl311th Apr 2012, 08:27Q2. F/L 350, TAS 450 K, TAT -11C, Find the Temp dev from ISA? OAT = TAT - (TAS/100)^2 OAT = -11 - (450/100)^2 = -11 - 20.3 = -31.3 C Temp at Fl 350 in ISA = -54.5 C So OAT at FL 350 is warmer than that in ISA Therefore Temp deviation = + (54.5-31.3) = + 23.3 C gAMbl311th Apr 2012, 09:26Q4. Earth Convergency btw two points 8 deg long apart is 7.2 deg on the same parallel of lat P is 173W & Q is 176 E Find. a) G/C bearing of P from Q in NH b) G/C bearing of Q from P in SH Convergency = d.long x Sin Lat 7.2 = 8 x Sin Lat Sin Lat = 0.9 Lat = Sin inverse 0.9 = 64*10' d.long between P and Q = 11 deg Convergency = 11 x 0.9 = 9.9 deg Conversion angle = 5 deg approx GC is near to the pole and RL is near to the equator (GC curved concave to the equator). a) In Northern Hemisphere http://img821.imageshack.us/img821/1305/prob4.jpg RL bearing of P from Q = 090 GC bearing = RL - CA = 090 - 5 = 085 b) In Southern Hemisphere http://img821.imageshack.us/img821/1834/prob4b.jpg RL bearing of Q from P = 270 GC bearing = RL - CA = 270 - 5 = 265 pilotbaba11th Apr 2012, 20:28@ This is a great thread, we should keep it open for nav questions.... @ Great explanations, thanks for helping.... Sorry to side track, But can anyone speculate when will the April 2012 session exams happen & also, does anyone know when does the online portal opens for filling DGCA forms online. I am trying to plan my travel but it is very hard without knowing the dates....