Hello 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

Q1. 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.

Q2. 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

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


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

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This is a great thread, we should keep it open for nav questions....

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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....