ILS landing questions...last 10 seconds before touchdown

[Gun Jam]

Hey

 

During an ILS approach the ILS bars should ideally be crossed at the dot in the center of the ADI right?

 

What I have noticed is during the last 10 seconds before touchdown it seems the ILS changes pattern and wants you to dive at the runway and then pull up quickly to flare. The bar indicating proper pitch dives very rapidly and then climbs very rapidly.

 

What am I doing wrong.

 

-Gun

[effte]

First off, stow the yellow bars in the ADI. In the A-10A they are command steering bars, giving you steering commands rather than ILS indication. No information has been found stating a change in function in the C, and they were (bugged) command steering bars in the betas. The fact that they are acting as ILS repeaters in the current versions is probably a placeholder pending implementation of working command steering, so you'll be doing yourself a disservice learning to fly using them. Use the caret on the left of the ADI (the caret, not the triangular pointer which is always centered) and the central bar on the HSI instead (see attached picture). Setting the inbound course on the HSI will of course help a lot there.

 

Second, the A-10C is only certified for CAT I ILS approaches. This means that the lowest altitude you can fly an approach to is usually to approximately 200 feet above the touch down zone (your decision altitude). That is long before your ten seconds prior to touchdown. If you do not have the runway in sight to enable you to transition to landing using visual references (i e by looking outside) at that point, you have to go around and try again or go to an alternate field - it's mandatory.

 

Below the decision altitude, the glide path is not reliable and will in fact be severely distorted, due to the way the signal is constructed. For lower minima, higher quality ILS installations are required and aircraft will have to be suitably equipped to transfer vertical guidance to the inertial navigation system, radio altimeter or a combination thereof.

 

Checking the specs of the modelled ILS's and doing a bit of flight testing to determine their characteristics, I've noticed that someone at ED has been digging deep into the serious reference documentation on the systems in order to model them correctly - far beyond the documentation those who are in professional aviation outside of the radio nav field ever see. This is further proof of this - well done, ED!

 

Cheers,

Fred

Edited March 18, 2012 by effte
Added picture

[Speedbrake]

The ILS system is set up to a glide slope that gives you a touchdown point about 800 - 1000 feet doen the runway. That is a lot of distance when you normally try to land on the nubers.

[BlueRidgeDx]

The glideslope transmitter is located adjacent to the touchdown zone, so as you approach the threshold, the glideslope becomes increasingly sensitive to even small deviations.

 

You should not use the glideslope below about 100-150 feet, since the sensitivity will lead to overcontrolling. If you don't see the runway at 200ft, you should go around.

 

Assuming you see the runway at or before DA and you go visual, keep the glideslope in your instrument scan until you pick up the VASI or PAPI, then fly that until you acquire your touchdown aimpoint. You should aim at a point 1000ft beyond the threshold. You will drive high on the PAPI as you approach the flare, but by then, you should be focused solely on placing the TVV on the far end of the runway as you touchdown.

 

Edit: Grabbed a bite to eat in the middle of posting, and got sniped...

[Gun Jam]

okay so based on all the above.

 

1) As of now and maybe forever the a-10 in real life and in the sim is not capable of a full ILS in 0/0

 

2) the pitch steering bar should be ignored and the caret used instead

 

3) the a10 must be landed visually

[BlueRidgeDx]

Correct, the A-10 has no onboard capability to perform a "0/0" landing. You must land visually following an instrument approach.

 

At present, the pitch and roll steering bars are not implemented properly in DCS. It's best to just turn them off for now.

[Gun Jam]

okay at least not just me.

 

The pitch and roll steer bars do seem to be the best method of actually getting close enough to acquire the runway but as I already found they aren't for landing as a single tool.

[Inseckt]

I've heard about the steering bars beeing bugged, but I want to ask, what is bugged about them? How are they supposed to work contra how they work now?

[BlueRidgeDx]

The subject was beaten to death in another thread (I'm on my iPhone, so I'm not going to search for a link), but the long and short of it is, the pitch and roll bars are presently acting as repeaters of the deviation needles. That is, they show the angular deviation from the centerline of the localizer and glideslope paths.

 

What they SHOULD do, is provide pitch and roll steering commands that if followed, will establish or maintain the desired path. It is literally a "dual-cue flight director", google it for pics and video.

 

At various points of DCS development, they worked properly albeit with incorrect sensitivity. Since then, they've turned into simple repeaters. It's a known issue, but I have no idea when or if it will be addressed.

[Tucano_uy]

3) the a10 must be landed visually

 

On a CAT I ILS approach, A10C, B747, or whatever, the last phase of the approach and landing is always done visually as explained above. So yes, you need visual references to continue the approach below decission altitude and land.

 

It may not be only a limitation of the aircraft but also the ground equipment. (An acft may be certified for CAT III approaches but the installed ILS at a given airport may be only CAT I, so CAT I app may only be done)

[FreeFall]

The subject was beaten to death in another thread (I'm on my iPhone, so I'm not going to search for a link)

 

I think you mean this thread:

http://forums.eagle.ru/showthread.php?p=1141393#post1141393