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Finding your way around in the Su25


Fish
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Navigation Guide for the Su25, (or any other aircraft without visible waypoint cues)

If you struggle with finding your way around in the Su25, because of its lack of a waypoint number indicator, then here's a 'fairly' fool proof procedure to find your 'bearings' if you get lost, or you loose the sequence of your waypoints.

 

It does require pre-planning, and a documented knowledge of the route you are going to follow, so for some online situations this may not be practical. (Maybe the online mission planners will consider this and give us some waypoint data for the different flights).

 

The HSI

Ok first i want to talk about the HSI in the su25, which is a little different in symbology to the 't' but works the same way. (If you're struggling with what the HSI is, or where it is, or you are looking at it for a different aircraft, then you probably need to do some work with the manual). There's two needles of interest, on here and we're only interested in one end of each. The 'waypoint' indicator is the one with the circle on the end, and a point on top of it. The other is the 'flight path indicator, or marker, and the end we're interested in on this is the one with the larger box shaped arrow on the end. This end always points in same direction as the flight path between the previous waypoint, and the currently selected WP (the one you WP indicator is pointing to). So that’s the WP indicator, and the FP indicator. And for the record, the outer HSI underlying dial rotates, so the 12 o'clock position is always the heading of your aircraft. Lastly is the dial to the immediate left of the HSI, it displays a 3 digit number representing the distance in Kms from the selected WP.

So now we know how to read WP bearing, the FP direction, and the distance from WP.

 

The Nav modes.

There are 4 submodes for the nav mode, one of which does nothing, but it does help us know which submode we are currently in. It is different from the other modes, in that it is 'passive' i.e. does nothing, and it shows two red marker symbols at the 10 and 2 o'clock positions on the HSI. You cycle the submodes with the '1' key. The submodes cycle in the sequence

nav/en-route,

nav/return,

nav/landing, and

Nav/Passive.

So for example if you want the landing submode, simply click 1 until the 'red markers appear on the HSI, then press the '1' key three further times.

Now we know how to get to the nav/en-route mode (or any other nav submodes for that matter)

 

Pre planning.

This is where the tedious work comes in. But all RL pilots must do this, and a lot more. And by the time you've done it you’re gonna feel much more comfortable with what you are about to do. It will also make the flight much more fun, and rewarding, as you will know where you are going, and what’s ahead. What were gonna do is measure the direction and distance from each WP to the next one, and document it. We will end up with a table of WP id's, starting at 1, a direction and a distance. The direction is the direction of the line from the previous WP, to the listed one. That’s why we start at 1 (normally take off is 0). The table would look something like:

WP Heading Distance

0 - -

1 15 35

2 32 10

3 07 15

You could (and probably should) add another column, with a brief description of what is to happen at that WP!). Also note I’m only using 2 digits for bearing, so 068 is expressed as 07(this is more than adequate for what we need it for). Note that the HSI plots your course much more accurately, but this info is used to get you back on track. I also like to take a screen dump of the mission map, and make this available on another machine, or print it. Picture and 1000 words etc.....

 

Getting onto the correct flight path.

This is like lining up for an ILS approach. So think of the WP you're approaching as a 'runway', and the flight path direction from the previous WP, like the runway direction. If you are pointing at the runway, but the you are left of the runway line, i.e. the runway line is pointing over your right shoulder somewhere, then the flight path marker will be to the left of the WP heading (which in this case is at 12 o’clock). So how would you get back on the flight line?. Yes, you would turn right to intercept the flightline, until you were in front of the runway line, then turn back left to get the runway in front of you. Now not only are you heading to the runway, but you are on the correct flight path. This is indicated with the WP marker and the FP marker both at the 12 o'clock position. Same applies for any other waypoint. Line your WP marker at 12'oclock, If the FP marker is pointing to the right, then turn left maybe 20/30 degs. and wait until the WP and FP markers align. Then turn back to the WP heading. So if you can do this, and you have your waypoint listing, you're 95% there in finding your way, once your HSI is working.

 

Now Finding your way.

So you are lost. But you should have some sense of where you were when you got lost. Have a look at the List details of the WP you think you should be heading to, and get the flight path heading for it (don't forget 32 means approx. 320 deg.). Now make sure your in nav/en-route submode. Cycle the wp (~) until the FP marker aligns with this direction. direction (the one on the list). Now you are in good shape and you can try two different approaches (pardon the pun). You are now pretty sure that the selected WP is the one you're heading for. You can go directly (no brainer), or using the procedure above, get quickly back onto the Flight path, then head for the WP (this might be important if you path is weaving the best course through ground threats, or through valleys to use terrain masking). So now you're pretty certain this is the correct WP.

 

But if you know the number of the waypoint.

A good thing with the Nav/en-route mode, is when you return to it from another mode/submode, it always goes back to Nav point 1. So if you know what WP you are looking for, simply cycle through the modes until you get to the Nav/en-route mode again, and press ~ key the appropriate number of times. Be careful though, it does not work this way with the Nav/return or Nav/landing modes. In these modes, it remembers what airbase or return point it was set to.

 

And if there two legs with the same headings

What if there are two legs of the route with the same headings, or close enough so there not distinguishable?. Well here's where a little concentration, piloting skills, and common sense comes in handy. You should be able to distinguish them with the distances you currently are from each. So its important to get back on the track as soon as possible, and be aware all the time of where you are. If you get lost, then you've need to address it straight away. Slow the jet to give you some breathing space. Its no good continuing, thinking you know this mountain or that valley (unless you absolutely do). And if don’t have confidence that the flight path you should be following is the correct one, then your problems started long before you got into the pit.

 

And finally

We have got to pick up the ILS for the runway at the mission end. If your last waypoint is a landing one, then it will get you to the approach approx. 17km from one end of the runway. If you pass the runway on route to this point, don’t forget to put some offset between you and this point, allowing you room to turn 'onto the 'glide path'.

 

But if you’re out of fuel and simply have to land.

Get into nav/landing mode (as described above). Cycle through the 22 known airfields (~ key), and pick the one which is closest (read the distance indicator beside the HSI), then cycle back to nav/en-route mode, and follow the above landing procedure, if you wish to do ILS landing.

 

And now,

You are totally confused.


Edited by Fish

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Guest IguanaKing
Navigation Guide for the Su25, (or any other aircraft without visible waypoint cues)

 

If you struggle with finding your way around in the Su25, because of its lack of a waypoint number indicator, then here's a 'fairly' fool proof procedure to find your 'bearings' if you get lost, or you loose the sequence of your waypoints.

 

It does require pre-planning, and a documented knowledge of the route you are going to follow, so for some online situations this may not be practical. (Maybe the online mission planners will consider this and give us some waypoint data for the different flights).

 

The HSI

Ok first i want to talk about the HSI in the su25, which is a little different in symbology to the 't' but works the same way. (If you're struggling with what the HSI is, or where it is then you probably need to do some work with the manual). There's two needles of interest, on here and we're only interested in one end of each. The 'waypoint' indicator is the one with the circle on the end, and a point on top of it. The other is the 'flight path indicator, or marker, and the end we're interested in on this is the one with the larger box shaped arrow on the end. This end always points in same direction as the flight path between the previous waypoint, and the currently selected WP (the one you WP indicator is pointing to). So that’s the WP indicator, and the FP indicator. And for the record, the outer HSI underlying dial rotates, so the 12 o'clock position is always the heading of your aircraft. Lastly is the dial to the immediate left of the HSI, it displays a 3 digit number representing the distance in Kms from the selected WP.

So now we know how to read WP bearing, the FP direction, and the distance from WP.

 

Don't forget the CDI (course deviation indicator), ideally, you should fly from point to point with your CDI centered. This imaginary point is called "course datum". The card on the HSI is usually indicating your magnetic heading...this comes from the flux detector on your aircraft and the stepper motor drive is slaved so that the flux detector has a direct effect on the synchro in the HSI system. However, the HSI can also be in "free" mode, which means it just attempts to keep up with the heading rate of the aircraft. Even the pilots of LOMACs western aircraft should learn how to use the HSI, the HUD only gives you a bearing, it doesn't give course datum information.

 

Welcome to the forum, Fish...no jab intended here, just wanted to add a few details. ;)

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Don't forget the CDI (course deviation indicator), ...............

 

Thanks for the comments.

 

There's no CDI in the Su25. The book calls it the programmed course needle.

I called it the flight path indicator, to help people understand. The symbology for the HSI is different for different jets, and thats why i ask them to refer to the manual.

 

I hope the point is not missed. The guide is for finding where you are if you get lost, in the su25, i added the paragraph of the HSI, for those who dont unserstand it, or those who don't understand it on the russian jets. Suffice it to say that if they can get the hang of the navigation in the su25, they can easily get it in all other aircraft in the sim. Or if they understand how to get back on course using the HSI, then the rest is easy.

 

 

Welcome to the forum.................. ;)

 

Thanks for the welcome

Fish's Flight Sim Videos

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Guest IguanaKing

The CDI is still there, its just on the AI in the Eastern aircraft. Its also sort of on the HSI, but its resolution is very course. The resolution of the CDI on the AI, on the other hand...well its a little too sensitive. Nope...not a dig against FC...this is the way it is IRL, I just don't happen to like it much...the course width is WAY too narrow. ;)

 

I have a bit of time in Eastern cockpits IRL too...L-39s mostly. :D

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Indeed. It's very well written nd easy to understand. Hopefully this will debunk the myths about the stock Su-25 being useless, overly complicated, or troublesome to fly. ;)

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Real men fly ground attack :pilotfly: where EVERYTHING wants a piece of you :D
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