Originally Posted by
jsfBoat
I'm curious to know if there is, and what is, the method to solve fix to fix navigation problems. I found something in Thai but couldn't translate it. Basically an airplane is on a certain radial at a certain distance and needs to figure out what direct heading will take the airplane to a different radial of the same VOR at a different distance. Appreciate any useful replies. Is there a way to do this on paper without looking at a HSI?
The only way I've ever done it is looking at an HSI while flying in an airplane. Isn't that the best way to do it since you need to do it while you're actually flying? You can practice on paper to get comfortable with the method, but how often are you going to know the exact fixes you'll be using when you're not in the airplane? When I was going through UPT in the USAF, our instructors would just give us a fix to fly to and we had to figure it out on the spot while flying the jet.
This method is no-wind and the heading you determine must be adjusted for any known winds. In basic terms, you use your HSI as a god's eye view of the situation and picture each fix on the HSI using a relative scale based on their DME. Then you turn to line up the fixes vertically so your heading is toward the destination fix. I'll assume you have some kind of bearing pointer available on your HSI or RMI to locate the radial you're currently on.
Example: You're on the 120/30 and you want to go to the 030/60 and you're currently heading West. You take the fix with the biggest DME and locate that on the edge of the HSI on the appropriate radial. So, looking at your HSI, the fix you want to go to (030/60) would be around the 4 o'clock position on the HSI at the outer edge. Using that scale, your current position will be on the tail of the bearing pointer half-way between the outer edge and the center since the DME is half of the larger. So, you're halfway from the middle on the 7 o'clock line. Once you have the two fixes located on the HSI, draw an imaginary line between them or even hold a pencil up to line them up. Now move the pencil (without changing its orientation) to the middle of the HSI and read the required heading based on the direction you need to turn (in this case a right turn). My guess would be the heading would be in the ballpark of North, no wind (I'm laying in bed and don't feel like drawing it out).
It's good to update as you fly toward the fix in case your first heading was a little off or winds are a factor. It's best to make your updates at whole number DMEs that are multiples of the larger DME (in this case, 10, 15, 20, etc) that make the math to set the relative scale easier.