Gen Nav Problem
 

*An aircraft at FL350 is required to cross a VOR/DME facility at FL110 and to commence descent when 100 NM from the facility. If the mean GS for the descent is 335 kt, the minimum rate of descent required is:


Correct answer : 1340 FT/MIN
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I cannot seem to find the way to calculate this !! WHY ??

Can anyone point out the "how" in this example.

Thanks in advance.

Proxus

If you are interrested I have another one that I can't complete:
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An aircraft is flying TAS 180 knots and tracking 090°T. The W/V is 045/50. How far can the aircraft fly out from its base and return within 1 hour?



Correct answer : 85 nm
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>> here's yet another one I can't figure out:

*An aircraft at FL330 is rerquired to commence descent when 65 NM from a VOR and to cross the VOR at FL100. The mean GS during the descent is 330 kt. What is the minimum rate of descent required?



Correct answer : 1950 FT/MIN

Problem 1 - First of all you need to find how many minutes it's going to take to get to your Vor.

100nm / 335kts * 60 = 17.9nm per minute

Then you need to calculate how much altitude you have to descend in that time.

35000' - 11000' = 24000'

Divide 24000' by 17.9nm per minute = 1340 Ft/min


Problem 2 is a psr question I think (can't work it out because I don't have my CRP with me).


Problem 3 is the same as the first problem

65nm / 330kts * 60 = 11.8nm per minute

33000' - 10000' = 23000'

23000' / 11.8nm = 1949 Ft/min


Hope this helps you out.

Thanks a lot,
 

Don't know why I could not calculate it, Hope this doesn't happen again at the test tomorrow :O

Maths in public
 

3D, Never do maths in public. OR if you do use the correct figures.

ill give question 2 a shot...

An aircraft is flying TAS 180 knots and tracking 090°T. The W/V is 045/50. How far can the aircraft fly out from its base and return within 1 hour?

Using these figures in my crp, the aircraft will fly at a GS of 141kts outbound, and return with a ground speed of 211kts

If t is measured in hrs

141 x t = 211 x (1-t)

141t/211 = (1-t)

0.668 t = 1-t

1.668 t = 1

t = 0.599

so the ac flys at 141kts for 0.599 of an hr

so travels for 0.599 x 141 = 84.5 NM

we can check this as the aircraft will return for (1-0.599) hrs at 211kts

= 0.401 x 211

= 84.6NM (rounding errors as im only using 3 dp for calcs)

regards

NB

edited beacuse i cant read my CRP very well!!

unowho , I've now changed the typo error from 355kts to 335kts. I can see how this would have totally thrown you off track regarding the question Mr Simpleton. I hope this is satisfactory for you, if not, just let me know!

An aircraft is flying TAS 180 knots and tracking 090°T. The W/V is 045/50. How far can the aircraft fly out from its base and return within 1 hour?

Formula:

EOH / O+H

E = endurance which is 1hr
O = groundspeed out
H = groundspeed home

You need to work out the ground speed using your whiz wheel or CRP

Add it to the formula just to be on the safe side I would do E x O x H then press equals

Add O + H then divide first figure by second figure to avoid any calculator errors, good luck!!




An aircraft at FL330 is rerquired to commence descent when 65 NM from a VOR and to cross the VOR at FL100. The mean GS during the descent is 330 kt. What is the minimum rate of descent required?

Height to loose
____________

distance / speed x 60

height to loose = 330 - 100 = 23,000ft

distance is 65nm
Speed is 330kt

so,


23,000
--------
65 / 330 x 60

Answer is 1946ft/min

Jinks

The formula is E*H / O+H

Too many O's in there mate.

:ok:

Afraid not my NH

2 formulas:

D x H / O + H

E x O x H / O + H

Sorry you are wrong :ok:

Jinkster

Id of gone with NH as well Mr Jinkster sir, this formula is the one taught by BGS.

However if the other formula works then it’s a new one on me?

YYZ

Guys, Jinx's forumula answers a different question. How far can you go in one hour. YYZ and NH, your formula is: How long till the PNR?

DOH !!

*smacks oneself round the head*

sorry Jinks :ok:

No worries NH

Will let you of this time....!!!!!!!!!! ;)

My method stops you being confused by Es and Os, and can be done on a calculator in 30 seconds, if you dont write it out.

Well.. You live and learn:D

go on ninja , let us now.....:confused: :ok:

cheers

RMM