Flight Unlimited III
Instrument Navigation without Autopilot
By Ian Boys

 
 
Go to a Discussion of this article here

Modern planes have magic GPS and autopilot systems to get them to where they want to go.  Let's face it, the Cessna Trainer found in FU3 isn't one of them. So how are we going to find a small uncontrolled airfield many miles away?

Well first off we are NOT going to use the "satellite" cheat on the map. If we were that sort of person we would just go back to playing Doom instead. (Or am I terribly out of date?)

Nor are we going to try this in the dark. We are going to use the radio direction finding equipment to guide us in as straight a line as possible but we will check our progress against landmarks we can spot.

The flight plan (see above map) calls for us to leave Shady Acres and fly up to Apex Airpark. We are going to find Apex Airpark by flying to the nearest VOR beacon to it (SEA 116.8) and then by flying a backbearing from it to find our landing strip. Flying to the VOR will be easy. Flying away from it will be harder.

Before take-off there are a number of things we can do:



Changing the Nav Frequency

OK - Take-off. Using ALT F7 helps us find the runway. Take off and turn to head north-ish. Fine tune the VOR locator until the yellow arrow is a straight line (if you tuned it on the ground it should still be close). You are 22 miles from the VOR and it is aneasy conventional flight along the bearing shown on your instruments. Climb to 2000 feet or so then level off with enough trim to keep your speed up.

As we approach Seattle our ILS system will tell us we are bisecting a glidepath for Sea-Tac Intl. Ignore this, just keep an eye out for big flying metal things.


Inbound to SEA VORTAC - level flight, 14 miles to go

About two miles out from the VOR end slightly to port and dial in either 280-285 or 100-105 on your VOR locator. The green light in the bottom left hand corner will show whether or not the arrow is pointing to or from the VOR, in case common sense fails to provide the answer. In the picture below I have dialled in 100 and am flying along the backbearing (in the direction of the small arrow). Although the TO/FROM lamp shows TO, clearly I am flying along the backbearing.

So how do I find the correct bearing?  Using the VOR overlay on the map gives us compass bearings (warning: North is not straight up). Using a straight edge I establish the bearing from the VOR to the destination. For the backbearing just add or subtract 180.

We now have to fly until we meet the 280 radial from SEA VOR, to we leave the VOR out to our right, flying on a heading of about 310 until we meet the radial. Turn left onto the radial and try to fly it as precisely as possible.

We fly down the backbearing from the VOR, checking our position against visual landmark checks where possible. Knowing that the landing strip is 22 miles from the SEA VOR allows us to spot it when we get that far. We make a normal landing, taking the altitude of the destination airport into account.

Any Questions?