Question about intercepting distant NBD's

Problem: I want to fly over Siberia to complete my world tour. There are mostly NBD's and no VOR's in the area (I know how to navigate with NBD's, it's not a problem.). One leg is 440nm long. When I calculated "blind navigation" distance between NBD's (HH class so 75nm of signal around) is about 300nm. It's an hour and 20 minutes of flight (L-749), and I'm afraid that I can miss NBD and get lost. I calculated that I have 5 degrees off course to intercept. Winds are unknown, aircraft like to turn slowly left, I observed it on map when over Atlantic. All realism settings are maxed, so can't navigate with compass because of gyro slide. Also no GPS - only on board instruments.

Can someone experienced give any advice?

An NDB (not NBD), or Non-Directional Beacon is such that if there is a crosswind as you attempt to fly to (or directly from) the station you'll fly an arc, thus your heading will change constantly (perhaps very slowly with little wind) in order to keep pointed at the station. The secret is to adjust your heading a little (comparing relative bearing to the NDB and heading) to try to compensate for the wind that you guess might be there. Check the results after a short time and, if the heading isn't changing as much then you're changing in the right direction. So make a further adjustment in your heading until you can hold a constant heading, though it may not point directly at the station. You're now flying a crabbed heading, but it should result in a straight path over the ground.

When going from the NDB, you can make the same kind of adjustments, though you probably already have a good idea of the wind (until it changes, of course), which gives you clues about how to proceed when you need to change to the next NDB.

I agree with Inuss. If you have been tracking on course from the NDB on the leg preceeding the 440nm leg, you can solve for the wind direction and velocity on the first leg. Then apply that wind to the track required to the second NDB on the 440nm mile leg to find the heading required to stay on course.

Art

Also thanks for advice

RK

Problem: I want to fly over Siberia to complete my world tour. There are mostly NBD's and no VOR's in the area (I know how to navigate with NBD's, it's not a problem.). One leg is 440nm long. When I calculated "blind navigation" distance between NBD's (HH class so 75nm of signal around) is about 300nm. It's an hour and 20 minutes of flight (L-749), and I'm afraid that I can miss NBD and get lost. I calculated that I have 5 degrees off course to intercept. Winds are unknown, aircraft like to turn slowly left, I observed it on map when over Atlantic. All realism settings are maxed, so can't navigate with compass because of gyro slide. Also no GPS - only on board instruments.

 

Can someone experienced give any advice?

1. You can navigate with the compass .

Every fifteen minutes read a steady compass heading , then set that heading to your Gyro direction indicator , that compensates for Gyro precession , it is the standard procedure commonly used by pilots , read any text on navigation and that will be in it !

2. Maintain a written flight log , at regular time intervals of either 10 or 15 minutes make entries into it , on your map mark your route for those time intervals , check against prominant ground detail , roads , railway , rivers , lakes , towns , significant mountains , then recalculate groundspeed and winds . Adjust to get back on track.

3. Fly as high as possible to maximise the NDB range as range varies (increases) with height increases.

4. As usual the most direct straight line route is not always the best or safest , study maps to find cultural objects , again the roads , railways , rivers , etc .

Choose those that you can positively identify from the air , lines that cross at 90 degrees are good , try to have other features that confirm it as a positive fix .

Then choose a route that enables you to get positive fixes at a couple of points between your departure and destination , this lessens the possibility of drifting too far off track and getting lost.

5. Use line features (roads , railways) to recalculate your current winds , then update your steering heading .

These are all part of normal flight planning procedures.

Cheers

Karol

(HH class so 75nm of signal around) is about 300nm. It's an hour and 20 minutes of flight (L-749), and I'm afraid that I can miss NBD and get lost. I calculated that I have 5 degrees off

How do you calculate your 300nm from the 75nm service range?

The real problem exists because you are trying to fly a great circle route using a "flat Earth" dead reckoning procedure. In reality, calculating what are known as arrival and departure angles from any fix is a complicated math procedure without computer help.

One easy procedure might be to use the built in FS Flight Planner and enter incremental waypoints along the direct line between the two NDBs about every 50 nm, then look at the Nav Log that the planner calculates. You will see the gradual required change in the needed course as you proceed to the next NDB.

This is also why you see a difference in course out/in between two VORs on an airway, because FS uses great circle nav, which is different than what you might see on an airways chart. GPS and INS use great circle nav as the basis for their calculations as well.

I cannot see how you calculated the 5 degrees off figure ? !

Your destination NDB broadcasts out to 75 nm , that gives a circular coverage that is 150 nm in diameter .

Basically your target is 150 nm wide , so you can be +/- 75 nm either side of your destination aimpoint (the NDB) off and your still will receive it's signal , that is a big track error.

1. Your worst case is , 75 nm off over the full 400 nm track , to miss by more than 75 nm your track error would have to be greater than 11 degrees .

2. As you have a NDB at the departure point , it will enable you to maintain track precisely for the first 75 nm , also it will give you the Drift angle for the current winds ,

thus making at least a reasonable portion of the leg precise as you will be laying off that drift , so your situation now is ,

400 - 75 = 325 nm to run after leaving the initial NDB coverage.

so now you can have up to 75 nm Track error over the 325 nm ,

to miss the destination NDB coverage your Track Error would have to be greater than 13 degrees.

A 13 degree TE is alarmingly big.

I can see no problems in flying the 400 nm leg and arriving within 75 nm of the destination NDB .

As soon as you start getting the destination NDB signals just turn and fly to that NDB.

Cheers

Karol