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Tips And Rules Of Thumb

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Thanks for your input CAP, was looking for just that, anything I have not heard before or simply things I have forgotten. Was recently in a discussion about point of no return and it led us to suns true bearing and onto the use of astro compass. I found it amazing how much you forget when you don't use it.

I have a database of tips and rule of thumb, but I just wanted to send this out and see what I was missing, as it has been a while since I have used some, (GPS how wonderful). So if anyone can help would be appreciated!

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maxtorc -------you bet "you loose it if you don't use it". May I assume that you are also aware that Ottawa doesn't publish "Navigating By The Sun's True Bearing " anymore? If you didn't, then consider you copy of that manuscript as a rarity. Their reason....get this......."with the proliferous use of GPS, the demand for this document had lessened greatly and therefore any further publishing will cease".



Winnie------better explain further what you're looking for because I don't think you are looking for the answer I have in mind.......or maybe you are.

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What I'm looking for are "simple" formulas to calculate Point of No Return (PNR) and point of Equal Time (PET, also kown as Critical point or Radius of action).


I need it in a simple format, so that I can punch the numbers into my calculator and come out with a good/correct result.


I have a deal for my E-6B, but it is hard to memorize, and they won't let me bring the sleeve in to do the test (written on the sleeve).




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H + O


E = Endurance O = Normal GS out H = normal GS home




PET..........(or distance to Critical point)




O + H


D = total distance from dep to des


or....Time to CP


CP = D (distance to critical point)



O (full groundspeed out)




....hope it helps, got more if ya want'em.

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Just as a slight variation to what RDM wrote


You can drop the last H in the PNR depending on wether you want the result in time od distance.


The current ATPs also talk of PSR (point of safe return), in which the E for endurance time is reduced by your minimums, so you don't plan to arrive dry tanks.


Also for multi eng heli. PNR / PSR OEI problem


Fuel flow out + Fuel flow home (OEI)

Gnd speed out Gnd speed home (OEI) = X



Available fuel

X =Distance to PSR/PNR



Distance over Gnd speed out = Time to PSR/PNR


Rate of descent.....

Glide path angle x Gnd speed[/u]

60x60 x 6080



max radar range............

constant (1&8 zeros meters per second)

2 x pulse repition frequncy


Obviously I use these every damned day. post if you have any particular needs, got loads of silly formula :o



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Current ATPs..... don't arrive dry tanks.....


Yikes, I was teaching that years ago!


The PNR is the same as radius of action, where the edge of the radius is your limit to use the same fuel to get back to base, useful in the Arctic, over water, or in similar hostile territory.


If you have to calculate PNR after an engine failure (in real life, not the exam), calculate the Specific Ground Range and add the fuel used per mile out and back together. Then divide the result into the endurance.


Don't forget that the CP has nothing to do with fuel, so just because you have one, it doesn't mean you have the range.


You can do CP (and PNR) on the whizzwheel by placing the groundspeed home on the inner scale against groundspeed out on the outer scale. Then look for two numbers which, when added together, comprise the distance or Time To Turn, as appropriate.


Other essential formulae (yeah, right) include the output of an AC generator:


Power factor = KW ÷ KVA


Or the one for calculating VHF line of sight range:


NM = 1.25 X <sq root>Height AGL


(height is both antennae)


Time to station:


Time (mins) = Mins x 60 ÷ Degrees




Time (mins) = Mins x GS ÷ Degrees


ADF bearing to station:




DMA Slant rage:


Range = Time (ms) ÷ 12.4


and Doppler shift:


fD = fT x V ÷ C


where V is aircraft speed in metres/second.


Oh yeah, the most useful, density altitude:


DA = PA ± (120 x ISA Dev)



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Hey guys,


Here is one that I actually use if fuel is becoming a concern.


Fuel burn in lbs/NM = Fuel Flow in lbs/hr divided by Groundspeed in NM/hr


Try it at a few different torque settings and use the one with the least fuel burn per nautical mile.


Also range is improved by increasing cruise speed into wind and decreasing it downwind.




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