Atpl Gen Navigation Questions

[HF13]

I need some help with some questions of general navigation...with the full explaination...if it's possible.
thank you all!

1)
The constant of cone of a Lambert conformal conic chart is quoted as 0.3955.
At what latitude on the chart is earth convergency correctly represented?

a) 66°42'
b) 23°18'
c) 68°25'
d) 21°35'

2)
The constant of the cone, on a Lambert chart where the convergence angle between longitudes 010°E and 030°W is 30°, is:

a) 0.40
b) 0.75
c) 0.50
d) 0.64

3)
Distance A to B = 120 NM,
After 30 NM aircraft is 3 NM to the left of course.
What heading alteration should be made in order to arrive at point 'B'?
a) 8° L
b) 6° R
c)4° R
d) 8 R°
THANKS AGAIN

[Streety]

1) The constant of cone of a Lambert conformal conic chart is quoted as 0.3955. At what latitude on the chart is earth convergency correctly represented?

a) 66°42'
b) 23°18'
c) 68°25'
d) 21°35'

Constant of the cone is the same as the sin of the parallel of origin. So inverse sin of 0.3955 equals 23.297, which if you convert to degrees and minutes is 23° 17.5' Answer (B)


2)
The constant of the cone, on a Lambert chart where the convergence angle between longitudes 010°E and 030°W is 30°, is:

a) 0.40
b) 0.75
c) 0.50
d) 0.64

Convergence angle = change in longitude X constant of the cone.

Or,

30° = 40° X constant of the cone --> 3/4 or 0.75 Answer (B)


3) Distance A to B = 120 NM, After 30 NM aircraft is 3 NM to the left of course. What heading alteration should be made in order to arrive at point 'B'?

a) 8° L
b) 6° R
c)4° R
d) 8 R°

Ok, we're 3NM off track after 30NM so after 60NM we would be 6NM off track which we know from the 1 in 60 means we have 6 degrees of track error.

To close back onto track we need to regain 3NM in 90, which is the same as 2NM in 60 if you divide both numbers by 1.5. So our closing angle equals 2 degrees.

Track error plus closing angle is the number we want, which is 8 degrees, and now we just have to decide left or right. If we're left of track then we're going to have to turn right to get back to it. Answer (D)

Hope this helps,

Streety.

[Nozwaldo]

Hope this makes sense.

Q1. Parallel of origin is where convergence is correct.
Constant of cone = sin parallel of origin
inv sin 0.3955 = 23.2971 = answer b

Q2. Convergence = ch long x sin parallel of origin(constant of cone)

Sin parallel of origin = convergence/ch long = 30/40 = 0.75
answer b

Q3. 3nm off track at 30nm = 6 degree track error relative to start
3nm off track at 90nm = 2 degree track error relative to destination
If track error is measured from both ends simultaneously then alteration toward destination by sum of track errors is the way ahead which is 8 degrees R, answer d.

If track error is measured relative to destination then alter towards heading by amount of error, this would be 2 degrees R but that is not given as an answer.
If track error is measured from start then alter heading by twice the error which would be 12 degrees R, also not given.

I think is right, any other explanations would help me also.

Noz

[HF13]

Streety, Noz thanks so much for the detailed and super fast answers...

...gen nav is killing me but i hope to help you out with other questions in the future!
thanks guys:ok: