Hi Everyone, i'm new in 727 world, i've spent a lot on 767 and now i would exp the old navigation style, vor by vor, but with this plane (fantastic plane) i'm getting nervous. when trying to intercept a vor radial and ride it for miles (with AP active) i overshoot the path many times.

so i've searched here for answers but still have the problem. is there a aircraft.cfg value to edit or tweak? 

if i try to intercept radial with 30° 3-4 miles away from path or simple activate AP when i'm ON THE PATH plane will start turning left right like crazy bunny for miles till stabilize on it   

hope sombody will help me. thanks have a nice day

These old babies need some delicate handling.The 30 degree rule is good ,but you need to also watch the intercept speed,otherwise I've found you tend to "see-saw" across the glide slope until she settles down.
Need some practice,but lots of fun,when you can grease it.LOL
Ron

when i try to land everything goes nicely because i'm used to align with runway manually looking instruments, so i land 9 times of 10 manually. my question was refered to simple vor navigation and intercepting radials. For example flying heading 015 and intercept vor radial course 355. if i let the autopilot to track the path he overshoot 3 or more times the path, seems like autopilot has a latency turning into radial, on my example the 727 will fly 015 till crossing 355 radial then he turn left trying to intercept path like a normal vor nav, but here is starting my question. Passing 355 radial and turning left i get into a 330 heading, then 010, then 340, 360, and finally my desired 355 and sometimes with high bank angle.

so i edited aircraft.cfg in the autopilot section

nav_proportional_control=12.00
nav_integrator_control=0.25
nav_derivative_control=0.00
nav_integrator_boundary=2.50
nav_derivative_boundary=0.00

these are now my settings and overshoot problem is very weak

so my question is: When a real plane intercept with AP ON a VOR RADIAL does he start turning BEFORE, ON or AFTER crossing the desired radial?

Wich nav_xxxx_xxxx=nnn setting in aircraft.cfg is related to this?

Or is the pilot in real navigation that couple a vor radial?


thanks to everyone

sorry for language

hi all, take a look

start KLAX 7L no wind, heading runway, to intercept SMO VOR on 90° course.
i've tried to edit aircraft.cfg and take screenshots.

i've edited only nav_proportional_control and set it to, 1 5 10 20 50 to see what happend


now u can see that with low values intercepting starts very very soft turning immediatly right but ends with heavy overshoot. with value 1 bank angle is poor and u will go really far away
with high values plane will intercept hardly the track, (with 20 and 50 it start turning LEFT) but ends in a soft course track.

I've set my value to 13, unluky number  

nav 5

nav 20

Some basics on the VOR.

The VOR is a pretty old nav system, but it works just fine if you understand the limits.

When in close to the station the radial is very narrow and thus more sensitive. At 60 miles from the station one degree is one mile wide so much less sensitive. If you fly a glass plane using VOR's observe how the computer leads the turn to intercept a radial. You will see that the computer will adjust the bank angle and lead time depending on radial movement. Do the same manually in the older planes (727, 707) and you will see better results. Most of the time in the 727 & 707 we would use either manual turn knob, or heading select to track the radial since the nav mode would produce too many zig zags.

Lou

Yesterday while doing EPRZ - EDDT i have decided to check A\P VOR tracking one more time. It worked right as it should! intercepting radial closer than 60 nm produces a lot of zigzags, but intercept it from 100 or more, and it works flawlessly! It tracks radial steady and integrates into it without zig-zags. I used small interception angles, like 10-15 degrees. It keeps aircraft oncourse up to beacon. within 10 nm i switching to HDG hold, set new beacon on nav1, turn AC to new course for interception, and turnig on VOR hold. Again, it gets new radial, and keeps the plane oncourse without any problems.

Never tried ILS loc tracking. I'll try it later, but i think it is better to hand fly it, if LOC interception point less then 10 nm of rwy. tight approaches might be "too fast" for "slow" A\P.

So i think we need to pay more attention and respect to classic tech