A question on ILS.
Thread Starter
Join Date: Sep 2002
Location: Scotland
Posts: 63
Likes: 0
Received 0 Likes
on
0 Posts
A question on ILS.
Hi All, just a quick Q on the ILS.
I use MSFS 2K (my lappy cant handle the newer versions).
anyway when im on final approach and i'm locked into the ILS, if i leave the ILS to control the complete landing to the point of touchdown, it brings the aircraft down nose first on that final last few seconds before touchdown, resulting in a crash.
I was just wondering in the real world, if the ILS system actually brings the plane down to complete touch, or if the pilot takes back control just before touch and brings it down to ensure a smooth landing?
Another note, are the ILS systems in real life as touch and go as they appear to be in FS2K? for instance, i just flew from Mcarran Intl to San francisco INTL, and the ILS completey screwed up, it was as if it was inverted, and was telling me to turn the opposite directions than i should have been. (course and freq were triple checked) So i had to to end up emergancy landing VFR :/.
any info on this would be appreaciated.
also, is the ILS transmitter from the runway the same type of hardware as VOR beacons? just wondered what they look like.
thanks alot
-tibbz
=====peep my beatz=====
http://mjtibbz.iuma.com
====================
I use MSFS 2K (my lappy cant handle the newer versions).
anyway when im on final approach and i'm locked into the ILS, if i leave the ILS to control the complete landing to the point of touchdown, it brings the aircraft down nose first on that final last few seconds before touchdown, resulting in a crash.
I was just wondering in the real world, if the ILS system actually brings the plane down to complete touch, or if the pilot takes back control just before touch and brings it down to ensure a smooth landing?
Another note, are the ILS systems in real life as touch and go as they appear to be in FS2K? for instance, i just flew from Mcarran Intl to San francisco INTL, and the ILS completey screwed up, it was as if it was inverted, and was telling me to turn the opposite directions than i should have been. (course and freq were triple checked) So i had to to end up emergancy landing VFR :/.
any info on this would be appreaciated.
also, is the ILS transmitter from the runway the same type of hardware as VOR beacons? just wondered what they look like.
thanks alot
-tibbz
=====peep my beatz=====
http://mjtibbz.iuma.com
====================
Join Date: May 2001
Posts: 10,815
Likes: 0
Received 0 Likes
on
0 Posts
Depends on the aircraft type and equipment fit if its capable of autoland.
And unless the wx is on the deck its normal to do manual landings anyway. The lowest I can go with the autopilot in is 200ft agl but normaly I will fly the intercept as well because the flight director takes more effort making sure its doing what you want than hand flying it.
As to what micro****e does on its approaches I don't know.
Proberly you would be better in the computer forum.
MJ
And unless the wx is on the deck its normal to do manual landings anyway. The lowest I can go with the autopilot in is 200ft agl but normaly I will fly the intercept as well because the flight director takes more effort making sure its doing what you want than hand flying it.
As to what micro****e does on its approaches I don't know.
Proberly you would be better in the computer forum.
MJ
Join Date: Jun 2002
Location: Kilmacolm
Age: 47
Posts: 740
Likes: 0
Received 0 Likes
on
0 Posts
Hi,
Although the ILS uses the same instruments and nav equipment as the VOR on the flight deck, the equipment on the ground is completely different.
Put simply:
The equipment uses a couple of localizer beams on different frequencies which overlap one another. The NAV equipment in the aeroplane uses those beams to determine whether the airplane is in relation to the centreline by interpoling the two beams and then outputting the result to the OBS instrument on the flight deck.
Thus, in effect the ILS Localizer only sends out a signal on one course only, ie 123 degrees or 051 degrees, or any one of the 360 degrees possible. Thus if your OBS inbound course on the instrument in the flight deck is set wrong this will NOT matter to the NAV equipment as it disregards the OBS setting.
The ILS Localizer transmits on the lower band of frequencies that cover the ILS and VOR stations. Ie, 110.70 being an ILS frequency and 117.45 being a VOR frequency. So the NAV equipment knows what sort of equipment to expect...
The Glideslope transmits on a seperate frequency but is automatically tuned into the NAV equipment onboard the aeroplane when the appropriate Localizer frequency is dialled in.
The Glideslope itself also has two "beams" sent from a seperate transmitter to the side of the runway and abeam the touchdown of the touch down markers on the runway. The reason for for so far down the runway is to give the pilot enough clearance over the fence.
The NAV box in the aeroplane works out from these two beams (again varying frequencies) as to where the aeroplane is located on the glideslope and then transmits this through to the instrument display.
Normal Glideslopes are at a 3 degree angle. But they do vary, ie Exeter has one at 3.5 degrees. At 60 knots groundspeed this could give you a convenient 300' per minute descent rate.
The reason why you could have had "reverse" sensing of the ILS is that you could have been flying a back course... ie an ILS beam for the opposite runway which one can use for an approach to the other runway. This, however doesn't give you a glideslope.
If you want all of the technical information such as frequencies used etc then let me know and I'll provide it.
One of the best ways to fly an ILS is to work out an inbound heading taking into account the wind. So say you worked out you need a 10 degree correction to the left and the inbound course is 050 degrees, you would initially intercept 040 and see if the ILS Localizer needle moved. If it doesn't then good you're on the centreline but if it does turn left or right (depending) two degrees or so to see if that brings the ILS back into the centre. If it does then either ammend your original correction heading (known at the reference heading) or keep it the same (ie 040). Remember the localiser gets very sensitive near the runway. Use a max of 5 degrees correction at say 10 miles out but near the runway use one or two degrees at any one time maximum.
The glideslope is easily maintained by working out your groundspeed (IAS taking into account the wind) roughly and use the following formula: (Groundspeed / 2) * 10 - this will give you the approximate decent rate in feet per minute that you can obtain on your VSI... if the decent rate isn't enough or is too much then change it by 50 feet per minute or so... the glideslope is very sensitive...
Just a quick note that the instrument in the flight deck is 10 degrees wide either side of the centreline using a VOR but the same instrument using the ILS is only 2.5 degrees wide either side of the centrline.
I'm sure an IR instructor would give you a better explanation for flying ILSs than myself though.
Best wishes,
Charlie Zulu.
Although the ILS uses the same instruments and nav equipment as the VOR on the flight deck, the equipment on the ground is completely different.
Put simply:
The equipment uses a couple of localizer beams on different frequencies which overlap one another. The NAV equipment in the aeroplane uses those beams to determine whether the airplane is in relation to the centreline by interpoling the two beams and then outputting the result to the OBS instrument on the flight deck.
Thus, in effect the ILS Localizer only sends out a signal on one course only, ie 123 degrees or 051 degrees, or any one of the 360 degrees possible. Thus if your OBS inbound course on the instrument in the flight deck is set wrong this will NOT matter to the NAV equipment as it disregards the OBS setting.
The ILS Localizer transmits on the lower band of frequencies that cover the ILS and VOR stations. Ie, 110.70 being an ILS frequency and 117.45 being a VOR frequency. So the NAV equipment knows what sort of equipment to expect...
The Glideslope transmits on a seperate frequency but is automatically tuned into the NAV equipment onboard the aeroplane when the appropriate Localizer frequency is dialled in.
The Glideslope itself also has two "beams" sent from a seperate transmitter to the side of the runway and abeam the touchdown of the touch down markers on the runway. The reason for for so far down the runway is to give the pilot enough clearance over the fence.
The NAV box in the aeroplane works out from these two beams (again varying frequencies) as to where the aeroplane is located on the glideslope and then transmits this through to the instrument display.
Normal Glideslopes are at a 3 degree angle. But they do vary, ie Exeter has one at 3.5 degrees. At 60 knots groundspeed this could give you a convenient 300' per minute descent rate.
The reason why you could have had "reverse" sensing of the ILS is that you could have been flying a back course... ie an ILS beam for the opposite runway which one can use for an approach to the other runway. This, however doesn't give you a glideslope.
If you want all of the technical information such as frequencies used etc then let me know and I'll provide it.
One of the best ways to fly an ILS is to work out an inbound heading taking into account the wind. So say you worked out you need a 10 degree correction to the left and the inbound course is 050 degrees, you would initially intercept 040 and see if the ILS Localizer needle moved. If it doesn't then good you're on the centreline but if it does turn left or right (depending) two degrees or so to see if that brings the ILS back into the centre. If it does then either ammend your original correction heading (known at the reference heading) or keep it the same (ie 040). Remember the localiser gets very sensitive near the runway. Use a max of 5 degrees correction at say 10 miles out but near the runway use one or two degrees at any one time maximum.
The glideslope is easily maintained by working out your groundspeed (IAS taking into account the wind) roughly and use the following formula: (Groundspeed / 2) * 10 - this will give you the approximate decent rate in feet per minute that you can obtain on your VSI... if the decent rate isn't enough or is too much then change it by 50 feet per minute or so... the glideslope is very sensitive...
Just a quick note that the instrument in the flight deck is 10 degrees wide either side of the centreline using a VOR but the same instrument using the ILS is only 2.5 degrees wide either side of the centrline.
I'm sure an IR instructor would give you a better explanation for flying ILSs than myself though.
Best wishes,
Charlie Zulu.
Thread Starter
Join Date: Sep 2002
Location: Scotland
Posts: 63
Likes: 0
Received 0 Likes
on
0 Posts
Hi, thanks for the replies.
Zulu, you said
The glideslope is easily maintained by working out your groundspeed (IAS taking into account the wind) roughly and use the following formula: (Groundspeed / 2) * 10 - this will give you the approximate decent rate in feet per minute that you can obtain on your VSI... if the decent rate isn't enough or is too much then change it by 50 feet per minute or so... the glideslope is very sensitive...
so it is possible to change the GS decent rate? i cant find anywhere on the flight deck and option to do this.
From what you said I have a feeling i may have been flying the backcourse during that flight, because there was no GS.
cheers
-mj
Zulu, you said
The glideslope is easily maintained by working out your groundspeed (IAS taking into account the wind) roughly and use the following formula: (Groundspeed / 2) * 10 - this will give you the approximate decent rate in feet per minute that you can obtain on your VSI... if the decent rate isn't enough or is too much then change it by 50 feet per minute or so... the glideslope is very sensitive...
so it is possible to change the GS decent rate? i cant find anywhere on the flight deck and option to do this.
From what you said I have a feeling i may have been flying the backcourse during that flight, because there was no GS.
cheers
-mj
Join Date: Mar 2000
Location: All over the show like a madwomans crap
Posts: 494
Received 0 Likes
on
0 Posts
ILS
mjtibbs
The formula for the glideslope is only a guide, albiet a good one, as to what you will need to descend at on the approach in order to keep the glideslope needle centered. Just half your groundspeed and add a zero. ie. 160 kts = 80 plus 0 = 800.......
That should get you there, and if all else fails, set 750fpm ROD and adjust as neccesary.
You cannot change the Glideslope descent rate from the flight deck as it is a fixed transmitter on the ground, usually set at about 3.3 degrees. I am certain you were flying a backcourse approach as well, judging by what you said the needles were doing.
Happy flying
The formula for the glideslope is only a guide, albiet a good one, as to what you will need to descend at on the approach in order to keep the glideslope needle centered. Just half your groundspeed and add a zero. ie. 160 kts = 80 plus 0 = 800.......
That should get you there, and if all else fails, set 750fpm ROD and adjust as neccesary.
You cannot change the Glideslope descent rate from the flight deck as it is a fixed transmitter on the ground, usually set at about 3.3 degrees. I am certain you were flying a backcourse approach as well, judging by what you said the needles were doing.
Happy flying
Join Date: Dec 2002
Location: 'Merica
Posts: 129
Likes: 0
Received 0 Likes
on
0 Posts
Hi Y'all,
Believe Londion City is towards 6* GS angle! Ok, my thoughts on Ground Station Equipment.
Localiser and Glideslope equipments are very similar, and only slightly different. Their frequencies are related and by setting the LOC frequency in the cockpit, the GS part of the equipment will also be on the correct freq.
The GS groundstation transmits the two beams stacked one ontop of the other, and the LOC sends them out side by side.
The 'two beams' sent out are modulated at 90 and 150 Hz respectively. So you can see that when you fly in the centre of the two beams there is '0' difference - hence a 'centre' reading on the cockpit instrument.
The position of the LOC ground equipment is at the distant end of the runway you are trying to land on. This means that the centre of the beams will be on the centre of the runway along its entire length. There are a few places with offset LOC's but we won't get confusing with that today!
The position of the GS ground equipment is relative to that runway's touchdown point. Follow the needle = land at touchdown.
Hope thats an simple explanation.
mjtibbs - sorry, it's just MS FS that cannot auto-flare correctly!
Cheers
Bear 555
(Pilot and ATC Systems/Navaids Engineer)
Believe Londion City is towards 6* GS angle! Ok, my thoughts on Ground Station Equipment.
Localiser and Glideslope equipments are very similar, and only slightly different. Their frequencies are related and by setting the LOC frequency in the cockpit, the GS part of the equipment will also be on the correct freq.
The GS groundstation transmits the two beams stacked one ontop of the other, and the LOC sends them out side by side.
The 'two beams' sent out are modulated at 90 and 150 Hz respectively. So you can see that when you fly in the centre of the two beams there is '0' difference - hence a 'centre' reading on the cockpit instrument.
The position of the LOC ground equipment is at the distant end of the runway you are trying to land on. This means that the centre of the beams will be on the centre of the runway along its entire length. There are a few places with offset LOC's but we won't get confusing with that today!
The position of the GS ground equipment is relative to that runway's touchdown point. Follow the needle = land at touchdown.
Hope thats an simple explanation.
mjtibbs - sorry, it's just MS FS that cannot auto-flare correctly!
Cheers
Bear 555
(Pilot and ATC Systems/Navaids Engineer)
Join Date: Mar 2000
Location: All over the show like a madwomans crap
Posts: 494
Received 0 Likes
on
0 Posts
G'day Bear, well explained. Can you tell me, London City at 6 deg. what would be the ROD required for that ILS? I am thinking that it would be around 1200 to 1300 fpm?
Cheers mate
Nosey
Cheers mate
Nosey
Join Date: May 2001
Posts: 10,815
Likes: 0
Received 0 Likes
on
0 Posts
It would be double whats required for a 3deg 
I have jumped seated on a 146 into city and its like going down a rollercoaster ride. And it feels bloody steep, tiny runway and water all around you.
MJ
I have jumped seated on a 146 into city and its like going down a rollercoaster ride. And it feels bloody steep, tiny runway and water all around you.
MJ
Join Date: Dec 2002
Location: 'Merica
Posts: 129
Likes: 0
Received 0 Likes
on
0 Posts
Hi Folks,
Yeah, my guestimation would be somewhere around 1200fpm.
Just checked the AIP for City - it is 5.5* for 10/28 ILS procedure, with the cautionary note attached " Non standard glide path at 5.5*. Procedure only valid for aircraft certified to carry out approaches at 5.5*."
Still, for the unfortunate few who have flown with me, then a rollercoaster could be considered an easy ride!! :-)
Cheers,
Bear 555
Yeah, my guestimation would be somewhere around 1200fpm.
Just checked the AIP for City - it is 5.5* for 10/28 ILS procedure, with the cautionary note attached " Non standard glide path at 5.5*. Procedure only valid for aircraft certified to carry out approaches at 5.5*."
Still, for the unfortunate few who have flown with me, then a rollercoaster could be considered an easy ride!! :-)
Cheers,
Bear 555
