ATPL Nav Exam - HELP ME!

[hsvrox]

Gidday Guys,

Sitting ATPL Nav very soon and need a help with a couple of things, instructors cant ehlp me so there must be someone out there!!! I'll buy ya a drink!!

Here goes...

1) DME arcs and the use of the 1:60 rule... apparently theres a formula for this, noone's quite sure what it is, something about 5 degrees of arc at 12 miles equals one mile distnace

2) Long range course indication on HSI for VOR track?? What's the difference?

3) Effect of earth convergency on aircraft heading when flying a great circle??

4) Multi-sector fuel calculations? Whats the deal?

5) Fuel Density? i remember this question and it used big jet plane flight plans tht little me in my cessna isn't use to...

Cheers Guys!!!

[swh]

Hi ..

1) Circumference of a circle is 2πr where π is 3.14.

For the 1:60 rule, it is an approximation of cos of one degree, saying that opposite side of a triangle at 60 nm is equal to one mile. This is due to the properties of a circle, i.e. the circumference being 2πr, and one degree therefore being 2πr/360 ≈ 2x3.14xr/360≈6.28xr/360, so you can see for a radius r of 60 nm, one degree is equal to 6.28*60/360 ≈ 1 nm

Now for a DME arc….you can use 6xr/360, so

DME, 1 deg, 5 deg (nm)

9 0.15 0.75
10 0.17 0.83
11 0.18 0.92
12 0.20 1.00
13 0.22 1.08
14 0.23 1.17
15 0.25 1.25
16 0.27 1.33
17 0.28 1.42
18 0.30 1.50
19 0.32 1.58
20 0.33 1.67
21 0.35 1.75
22 0.37 1.83
23 0.38 1.92
24 0.40 2.00
25 0.42 2.08

2) The only thing I can think of that they are asking the difference between the rhumb line and GC for the track, the convergence angle between the two will be the change of longitude by the sine of the mean latitude.

3) That depends on the chart, on a Mercator the rhumb line is straight and the GC is curved, on a lambert or polar the GC is close enough to a straight line. On a Lambert the convergency is same over the chart, on a Mercator half of the change of longitude by the sine of the mean latitude (½ ch long sin (φ))

4) Need to know more on what your asking, you asking about a multi sector PNR, CP, or howgozit ?

5) Specific gravity is normally given to you, 0.8 kg/l is a common number
KG to LT = times 1.25
LT to KG = times 0.8
LB to LT = times 0.57
LB to LT = times 1.76

or just use your CRP3

:ok:

[vh-oja]

1. Just think back to you're ppl training, 1 mile off track at 60 miles distance is 1 degree of error, exactly the same with DME. For you're example, you are 5 degree's off at 12 DME, it will still be 5 degrees at 60 miles and using the one in 60 rule also gives 5nm distance. As you are at 12Nm, not 60, simply divide by 5. (60 divided by 12) giving you the answer of 1Nm.

2. What the ?????

3. Depends on Direction of flight, latitude, and hemisphere, Diagrams are a useful aid.

4. Multi sector fuel calcs are in Flight Planning

5. Not in the Nav Exam

[swh]

Should have added for the DME arc question ...

on your CR3/CR5 line up the DME arc distance on the outside scale to 60 on the inside scale, the read off the outside scale the distance corresponding to the angle on the inside scale ...

eg
12 outside : 60 inside
5 inside : 1 outside

:ok: