Hi all, doing a flight last night YSSY-NFFN. All looked rosey and sweet. Was established on the G/S and LOC ILS 02 at around 165kt, the aircraft appeared to be following the ILS/LOC (Both Magenta diamonds centred) but it suddendly looked like I was still too far from the threshold (around 2-300 meters) and was going to land short. Neither diamond moved from the centres of the PFD. needless to say, disaster occured as my throttle and buttons stopped responding (separate issue)

 

I did notice a G/S inhibit light illuminate, but was at the last minute, so not sure why that happened or why it came down short, when all appeared to be good.. I also notice when I select the Nav 1 and 2 ILS freq (109.90) it says G/P on the PFD. Not sure

 

Just out of curiosity, I used the program called FS Instant Approach, with the FSX 737 and it followed the G/S perfectly, so i guess its not a scenery issue.

 

Any advice would be appreciated.

 

Cheers  Chris

Sounds a bit like this incident:

http://www.youtube.com/watch?v=GelRBhJ4gm

Thanks for the reply hopskip, but says video unavailable :mellow:

G/S inhibit light should work as a button to silence GPWS "Glideslope" verbal warning.

 

Are you sure you were in ILS approach mode as opposed to IAN approach mode? i.e. did the vertical mode show G/S or G/P?

Hi Fabo, Um not sure now. I had APP mode engaged on MCP, but have a feeling that G/P showed up just below the annunciators. To be honest, I'm a newbie at this ILS business but have done many ILS approaches, but never seen the G/P indicator come up on the PFD. The Chart is at:

 

http://www.cyberair-yssy.com/NFFNALL.pdf

 

(Page 14) if thats any help. I am going to do this flight again tonight, and take some screenies if it happens again.

 

If I was in IAN approach mode, then I need to do some more reading up

 

Thanks  Chris

Just thought I would update on this. I did the flight again yesterday, this time without high drama. I changed 2 things, and would like to know if either would have made the difference. Firstly I noticed that when the aircraft captured the G/S, it showed "G/P" on the annunciator. I slowed the aircraft down to 150kts (was 165kts) and it captured the G/P as before.

 

The other thing I did was checked AS2012 for the baro reading, which was 29.80, so I set the baro to 29.80. Previously it was set at 29.92. Would this have affected the botched landing previously?

 

I think I need to read up on the differnce between G/P and G/S as there is obviously a difference.

 

Cheers Chris

Hi Chris,

 

G/S and G/P are indeed quite different. Look up IAN approach in the fcom for information on the G/P annunciation.

 

Essentially ILS approaches use the NAV radio to receive the LOC and GS signal to feed the flight director with cues to follow the approach including the GLIDESLOPE (G/S). An IAN approach uses info in the FMC to guide the aircraft along a computer generated GLIDEPATH (G/P).

 

Be sure that you select an ILS approach in the FMC when selecting your arrival and that (I think it's called G/P) in the FMC is off. If you are flying an ILS you don't need the FMC to calculate the 3deg slope for you.

 

Also, the barometer setting will definitely affect your altimeter reading if using an IAN approach as the aircraft's instruments think you are several hundred feet from your actual altitude. Setting the Baro to QNH (or the pressure read at the arrival field) is set and checked as part of the Approach Checklist. For Nadi transition level is FL130 so that's where you should change your barometer to local.

 

Good luck.

Previously it was set at 29.92. Would this have affected the botched landing previously?

 

 

Yes

 

 

 

 

I think I need to read up on the differnce between G/P and G/S as there is obviously a difference.

 

Cheers

 

 

Yes

 

The Glide slope (G/S) is ground equipment which is independant to your aircraft. Glide path (G/P) part of the IAN approach uses no external equipment and relies on correct baro settings.

 

I Usually intercept the LOC before hitting APP to arm the G/S. On occasion I have had a IAN approach come up instead when I arm earlier but I clear it and make sure LOC and G/S arm and/or capture instead.

Thankyou both for your valuable input!!l

 

Viper writes:

 

"On occasion I have had a IAN approach come up instead when I arm earlier but I clear it and make sure LOC and G/S arm and/or capture instead."

 

Yes I may have selected the LOC button a bit early (No LOC light came up on the annunciator). As for the G/S G/P, I'll have a closer look at the FMC again tonight as I'll be doing that sector again. Anyway, I have some reading to do, but I have been changing the baro @ 18000, which is incorrect (For Nadi), so I learnt something there.

 

Many thanks,

 

Chris

Hi Chris,

 

Glad I (we) could help. When you arm LOC you should see VOR/LOC annunciation in white below the active mode (green is active, white is armed). When LOC intercept occurs the active mode will change and VOR/LOC will change to green.

 

You will find the transition alt at the top of approach charts. Unfortunately I cannot find (only searched for a few minutes though) a free source of Nadi approach plates for you though.

Thanks Barbs, yes I now understand the green/white on the annunciators. So pressing the VOR/LOC early (ie; out of range) wouldnt have done anything (system wise), as there was no green or white VOR/LOC illuminated on the annunciator when it was pressed?

 

There is a few charts here:

 

http://www.cyberair-yssy.com/charts.html

 

Nadi is at      http://www.cyberair-yssy.com/NFFNALL.pdf

 

Cheers Chris

Hi Chris,

 

That's correct. I believe if the ILS LOC is not being received by the NAV systems, then pressing the LOC button will have no effect.  So potentially you were trying to arm LOC mode far too early.  Generally this would be done once established on an intercept heading.

 

Regards

Greg

Cheers Greg for that Viper. did the same flight again yesterday and everyone survived :-)