Basic ILS Question

[Guest dakrisht]

I have one or two questions regarding using the ILS / Approach feature of certain aircraft.Basically, when should you push the APP (Approach) button on the aircraft your flying to enable the auto-land / auto-descent ?Today I was flying the stock Learjet from KLAX-KSJC and began my descent about 80 miles out, I had the ILS frequency tuned and the ILS heading set as well. (The visibility on this bird is just plain awful by the way).I guess the same would apply for the 737NG and other auto-land capable planes... Perhaps I'll do the tutorial in FSX but I wanted to get some frequent flyers to weigh in on the ILS approaches.Thanks

[brucek 38]

I have one or two questions regarding using the ILS / Approach feature of certain aircraft.Basically, when should you push the APP (Approach) button on the aircraft your flying to enable the auto-land / auto-descent ?Today I was flying the stock Learjet from KLAX-KSJC and began my descent about 80 miles out, I had the ILS frequency tuned and the ILS heading set as well. (The visibility on this bird is just plain awful by the way).I guess the same would apply for the 737NG and other auto-land capable planes... Perhaps I'll do the tutorial in FSX but I wanted to get some frequent flyers to weigh in on the ILS approaches.Thanks

In real life (I am IR), you intercept the localizer first, then descend as allowed to maintain terrain clearance to what is called the "FAF (Final Approach Fix) altitude", where you will intercept the glideslope. Typically at that point you are about 2,000 above the touch-down elevation, so for a 3 degree glideslope you will be about 5 miles out at the FAF.The reason that you do it this way is that there are false glideslopes that result from the radio beam being relected from the ground, and the false ones will not bring you down correctly.I don't know if you have access to instrument charts, a lot of this info is on them. You could also use the FSX ATC, although it does vector you around a bit.Assuming that you could replicate real world IFR ops in FSX, you would only use the LOC/VOR (lateral only) autopilot mode until established on the localizer and below the glideslope, then activate APP. What concerns me about your OP is that you are intercepting something 80 miles out, which would be a disaster in real life unless you perhaps were flying something with a V-NAV capability, but even then I have never heard of an approach comemncing that far out.Good luck, Bruce.Bruce.

[OldMaintChief 7]

The 737 is a good aircraft to practice with. Fuel load 30% wings, others empty.Assume landing on runway 36. Fly to a point 30 mi. south of the field 5,000 ft., HDG 360.With AP on HDG and ALT HOLD, slow to 200 kts.The vert needle will become active at 25 miles. Adjust HDG 5 degrees to the needle.When needle centers, adjust HDG to 360. Call tower for touch and go.You can press APP and the aircraft will fly the vert needle, and hold 5,000 ft.The GS needle will become active at 20 miles and start moving down the scale.When the needle centers, the aircraft will pitch up/down and lock on the GS.Reduce power and drop 10 degrees flaps.At 8 miles blue MM light on drop gear.In increments, drop more flaps and slow to 135 kts with full flaps at white IM light.Disconnect AUTO THROTTLE, if used. Not tied to AP.Press APP and flare.Set flaps to 10 and take off. Turn left to 180, climb to 5,000 ft.At 23 mi. turn left to 360 and try it again and again.Not RL but good practice in FS.Have Fun!DaveSystem:Dell XPS 720 H2CIntel Quad Core Extreme QX6800 @ 3.73GHz4GB (2x2GB) Corsair Dominator EPP 8500C5D FSB 800MHz @ 1066MHz2x160GB WD SATA Raptors, Sound Blaster X-FiNvidia 2x8800GTX 768MB SLI, Dell 2407WFP PanelXP driver: 169.21, Vista driver: 169.25Logitech Z680 5.1 Speakers, G5 Mouse, Saitek X52WinXP Media Edition SP3 on C: (SATA 0) w/ Internet/AV/Office/FS9/Falcon4 AFVista SP1 on D: (SATA 1) (Dual Boot) w/FSX3DMark06: 17,018/6992/7123/5667

[RickY 3]

... when should you push the APP (Approach) button on the aircraft your flying to enable the auto-land / auto-descent ?

My rule of thumb that has served me well since FS2002 days is to press APP only after BOTH the Localizer and Glideslope indicators or needles are displayed, checking that the aircraft is still below the glideslope so it can intercept it reliably. In addition, success is more consistent when the aircraft is still below the glideslope at the time the Localizer is intercepted and the aircraft begins to turn. This procedure is for reliable operation in the sim, of course, and may or may not reflect real world operations.Rick

[Guest PPSFA]

Plan your approach so that you intercept the localizer at no more than a 30-45 degree angle, using heading mode or hand flying. Using an approach plate, descend to the altitude shown at the IAF, usually around 20 miles out. As soon as you see the LOC needle start to move, enable APPR mode. This will track the LOC inbound and when you intercept the GS at the FAF, the plane should begin a descent and track it. Some planes work better than others, but thats the basics. www.airnav.com has every chart, plate, etc you need for the US, and it's all current and free.

[rhodges 6]

Hi:One other thought unique to some FlightSim aircraft which is not applicable to real world approaches. In times long past, some aircraft would react strangly for me if the Approach Mode was initiated before the glideslope became active even though the localizer is within range. Therefore long ago I established the habit of initiating the "Nav" or "Loc" mode as soon as the localizer needle begins to move. Then I wait until the glideslope needle becomes active and begins to move down to switch to the "App" mode. It has been a long time since I tested an approach without useing this method, so possibly this is overkill now days. However, if you see something strange when you select "app" you might keep this hint in mind. It has worked flawlessy for years over several FS versions for me, so I just adopted it on a permanent basis.It is hard for me to believe that you were receiving a localizer signal 80 miles out. I strongly suspect that you were picking up a VOR signal with the same freq. as your desired localizer. Somewhere between 20 and 30 miles out is the maximum range I have ever experienced. Out of curiosity, what airport, runway, and frequency were you useing?Good luck:RTH

[Guest PPSFA]

It is hard for me to believe that you were receiving a localizer signal 80 miles out. I strongly suspect that you were picking up a VOR signal with the same freq. as your desired localizer. Somewhere between 20 and 30 miles out is the maximum range I have ever experienced. Out of curiosity, what airport, runway, and frequency were you useing?Good luck:RTH

ILS and VOR's freq's are in different bands, however it could have been an ILS from another airport, as these are duplicated, although usually not that close.

[pontiuspilotus 6]

Bear in mind not all aircraft has autoland modelled, so check the craft you're flying first to see if this feature is available (ok, most modern Boeings and Airbuses do). From 80 miles out you wouldn't be able to see the glideslope come alive. Someone correct me if I'm wrong but I don't believe the FSX stock Learjet has autoland implemented.

[scott967 62]

I guess there are different SOPs but what I have seen is when the localizer needle is alive, activate NAV or LOC mode, and when glideslope needle is one - one and a half dot above activate APP or GS mode. In some cases they might hit the landing gear as glideslope captures, to maintain approach speed while descending. After GS capture reset MCP altitude to missed approach alt.At some locations there is interest in "continuous descent" approaches. I don't know when you would activate the APP/GS mode for this.The FAA standard service volume for a localizer is 18 nm and for ICAO it's 25 nm. FAA certifies some localizers to an extended service volume (altitude dependent). FS defaults localizers to 27nm with backcourse enabled.scott s..

[Geofa 108]

The problem is autopilots work differently depending on the model and the fs one is a generic no model one from what I can tell.On the autopilots I fly-the appr is just really a much more sensitive nav mode. You can actually use it instead of nav mode to track a vor for instance in normal navigation.With an stec 50 autopilot for approaches-you would use the heading mode and fly the plane till it was pretty much on the final approach course-then press appr. Doing so earlier than established would not work.With my present autopilot-a century IV- you can press the heading/appr buttons at the same time when given the final intercept. The autopilot will capture/engage automatically approach mode when appropriate, and then engage the glideslope mode automatically when it comes in.From what I have seen-flying the fs autopilot like an stec 50 will work better-use the heading mode and bug to get yourself established first.

[OldMaintChief 7]

What happened to the guy who started all this? Did he get it?I don't think any FSX aircraft have AUTOLAND capability.Have funDave

[brucek 38]

ILS and VOR's freq's are in different bands, however it could have been an ILS from another airport, as these are duplicated, although usually not that close.

Yes- one sure way to know if you are receiving a VOR or ILS (LOC) is that the decimal point is even for VOR and odd for ILS/LOC. So, at my home airport of KBJC, the ILS for 29R (I-BJC) is 111.7, and the onsite VOR ( BJC) is 115.4Also- as mentioned here, the localizers are usually in the lower portion of the aviation band, followed by VOR's, then speech, although that does not always apply.Bruce.

[OldMaintChief 7]

I just tested the AUTOLAND feature in the B737. It did flare over the numbers, but the AT did not reduce power since it is not tied to the AP. I turn off AT and APP and do my own flare and power adjustment so I hadn't noticed.The first aircraft I flew/maintained was R-4D-3 and SNB. They had VOR only ARN-30 hand-cranked freq selectors (coffee grinder). The later R-5D aircraft had ARN-14 digital freq seletor. They were VOR/LOC receiver with a seperate GS receiver/ant. The ARN-21 Tacan was added to get DME. Now you have VORTAC receivers with ILS and DME built in. I once put in a small DME set in some helos, without Tacan, so the pilots could have DME with the VOR.The VOR freq is 108 to 118, above is comms. The VOR tunes in .050 steps. The odd .5 steps from 108 to 112 is reserved for ILS/LOC, GS freqs are auto selected.I fly the MAAM R-4D-6 since it was a sister ship to the -3 and -5's I first flew.Have funDave