SU-27 on glideslope what exactly do the circles represent?

[fitness88]

Using ILS, I thought 1 circle on the HUD represented the Localizer and the other circle represented the glideslope. Get them superimposed upon each other with the datrum centred and you are on glideslope. If that is how it works which circle represents what?

Thank you.

[Ironhand]

Using ILS, I thought 1 circle on the HUD represented the Localizer and the other circle represented the glideslope. Get them superimposed upon each other with the datrum centred and you are on glideslope. If that is how it works which circle represents what?

Thank you.

The large circle is, as always, the navigation mode's flight director. In the landing submode, it is telling you where to fly to, first, capture and, then, keep yourself on the glideslope. The smaller circle represents the glideslope itself. Once they are both centered and stay centered, you have the glideslope centered with the proper sink rate dialed in. If, OTOH, the large circle should start to drift to the left, for example, then you need to steer a bit left to recenter yourself, etc, etc. Or, should the large circle start to drift up, then you are sinking too fast and need to adjust your throttles to reduce your sink rate, etc, etc.

 

So the large circle is always telling your where to fly. And, if you follow it, the small circle will always end up centered inside it.

 

Rich

[fitness88]

Ironhand thank you for your response.

You stated that the small circle represents the glideslope but you also stated that if the large circle drifts up I need to reduce sink rate...shouldn't that be if the 'small circle' drifts up I should reduce sink rate since the small box represent the glideslope.

[Vekkinho]

No, small circle doesn't "move" as it represents a glideslope that's pretty fixed on most runways! So it's a big circle (or You) moving in relation to glideslope!

 

Adjust the sink rate and heading in order to stay on the glideslope (circle within circle) and practice instrument finals with dense fog to make it perfect!

 

Remember that during finals throttle controls sink rate and AoA and pitch controls approach and touchdown speed.

[fitness88]

No, small circle doesn't "move" as it represents a glideslope that's pretty fixed on most runways! So it's a big circle (or You) moving in relation to glideslope!

 

Adjust the sink rate and heading in order to stay on the glideslope (circle within circle) and practice instrument finals with dense fog to make it perfect!

 

Remember that during finals throttle controls sink rate and AoA and pitch controls approach and touchdown speed.

 

Thank you for your response.

Edited December 17, 2008 by fitness88

[Ironhand]

As Vekkinho notes, always follow the flight director circle (large circle). That's the one that is telling you what you need to do to get to where you want to go.

 

If you haven't already, just for fun, follow the flight director circle when in the main navigation mode. You'll see how it works without the distraction of the small circle. And you'll end up on the right course at the designated altitude according to your flight plan (WPs).

 

Rich

[fitness88]

Ironhand:

If the large circle is all you need why have the small circle at all if all the small circle does is just to confirm where you should be?

Thank you.

[Bearitall]

Ironhand:

If the large circle is all you need why have the small circle at all if all the small circle does is just to confirm where you should be?

Thank you.

 

 

Tower tells you whether you are on correct glide path..trust me..this comes in handy..especially trying to land on Carrier..

 

But Ironhand will correct me if I am wrong..I take what he says with great value...

 

:joystick:

[Ironhand]

Ironhand:

If the large circle is all you need why have the small circle at all if all the small circle does is just to confirm where you should be?

Thank you.

In the general nav mode, the large circle is sufficient because being a bit off isn't critical. An ILS landing is another matter completely. Accuracy is paramount. The small circle is there so that you know you are precisely centered. Even small deviations are easily and quickly noticeable.

 

Rich

[fitness88]

In the general nav mode, the large circle is sufficient because being a bit off isn't critical. An ILS landing is another matter completely. Accuracy is paramount. The small circle is there so that you know you are precisely centered. Even small deviations are easily and quickly noticeable.

 

Rich

 

Ironhand:

Yes that makes good sense because in bad visibility when you're relying on the ILS, being off just a bit from dead center of circle could easily cause you to be wide and miss the runway...I've done that. I will pay more attention to having the circles dead center of each other.

Thank you again.

Edited December 18, 2008 by fitness88

[DPS]

If you find the Flight Director circles on the HUD a bit tricky, you will find more conventional ILS fly up/down left/right indications down below on the instrument panel HSI.

 

The Su-33 has the same set-up but bear in mind that when landing on the carrier there is a big off-set angle as it will line you up with the landing on deck rather than the ship's Course Over Ground.

[fitness88]

If you find the Flight Director circles on the HUD a bit tricky, you will find more conventional ILS fly up/down left/right indications down below on the instrument panel HSI.

 

The Su-33 has the same set-up but bear in mind that when landing on the carrier there is a big off-set angle as it will line you up with the landing on deck rather than the ship's Course Over Ground.

 

Yes I am familiar with the HSI and ADI indicators as I used them on the F15 but I find on the su27 the flight director on the HUD is much easier to follow and hold.

Thanks again