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Can B 737 NG 600/700 Flay a Back Course ILS?

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Zurich (LSZH), has six runways but only two with ILS approach. These are #14, and #16. I was planning to do an ILS landing on Rwy 16 on a heading of 156, when the ATC assigned me to Rwy 34 on a heading of 336. Rwy #34 has no ILS.In the FS 9 Boeings, one can tune the Nav1 radio to the ILS Rwy 16, and fly in to Rwy 34 using the Rwy 16 ILS by activating the BC (back course) button.There is no BC button on the PMDG B 737NG7 600/700. I had to do a manual alignment with the runway, and landing. Is there anyway to do a BC ILS landing on the PMDG B 737NG 600/700?Also in the ND (navigational display) map mode,when descending for a landing, I note a vertical line bar on the right hand side with a red diamond. If I am descending according to the flight plan in the FMC, the red diamond remains in the middle of the vertical line. If not,it goes to the top of the vertical line, and a number appears at the top of the vertical line. What does this number represent?Thanks. Stanner

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dont know about your question, but I can say this; during my IFR training in '98 I 'flayed' a few backcourse approaches amoung others.:-)(cant help it, its late here)

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I can't answer the back course question for you but I know the numbers above that vertical line indicate how far off from your altitude you are. IE GS at 4000' y'r at 10000' you should see the diamond at the bottom of the line with 6000' at top. That is my interpretation of it. But I think this information also must be programmed in your FMC because I never see it if I fly blind (hehe one of those load an go flights)Bretthttp://www.precisionmanuals.com/images/forum/800driver.jpg

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>Also in the ND (navigational display) map mode,when descending>for a landing, I note a vertical line bar on the right hand>side with a red diamond. If I am descending according to the>flight plan in the FMC, the red diamond remains in the middle>of the vertical line. If not,>it goes to the top of the vertical line, and a number appears>at the top of the vertical line. What does this number>represent?>>Thanks.> >Stanner>Back course ILSs are flown in the NG by using LNAV to track the lateral course (there's no REV mode) and using VNAV or VS or LVL CHG to manage the vertical profile.As for the vertical deviation indicator in the ND, the number represents how many feet above or below the computed vertical path you are. This is discussed in the PMDG manual, which I strongly suggest you read many times.Best wishes,

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Tim.Thank you for your reply. Regarding the back course I am confused.Are you saying that if I use the LNAV and VNAV I will pick up the ILS signal of the oppsite runway approach, or are you in essence saying I must do a manual approach?Stanner

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A backcourse is the backside of the ILS, on the otherside of the runway. As I understand it, there is enough of a signal that a plane can fly the lateral course keeping lined up with the runway. But there is no signal that guides the plane vertically, it is up to the pilot to bring the plane down safely. WHY of WHY would any airport have ILS only on one side??? WHAT are they too cheap??!! Well one good example would be KSAN, RW 27. The approach comes straight through the city buildings, and the buildings interfer with the signal. So if they had ILS for 27, the signal might get borked and a plane might zoom right into someones apartment.John Palmeri

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Hi John,Your correct that a Back-Course is the other side of the runway. In the real world, an ILS (Instrument Landing System) is composed of two transmitters, and a few beacons.The first transmitter is the "Localizer" which provides lateral navigation and is much more accurate than a VOR signal. The specific limits of this beam vary between ICAO and USA but good rule of thumb is a localizer spans a 10 degree arc (each side) from runway centerline to a range of about 25NM, and widens to about 35 degrees inside 17NM. The second is the "Glide-Slope" which is normally at a 3 degree angle leading to the touch-down zone of that runway. This signal is normally usable within 10NM, but certain locations can increase this distance.Other components of an ILS are the Outer Marker usualy found at the Final Approach Fix, the "Middle Marker" about 3500 feet from the threshold (or about 200' AGL) and for ILS Cat II/III "Inner Marker"(bingo time!!).The backcourse uses the localizer signal only, (with other optional nav-aids). >WHY of WHY would any airport have ILS only on one side??? WHAT are they too cheap??!! Because of terrain and other considerations (money too!) If you want more information, the Airmans Information Manual (AIM) is a good place to start, as well as TERPs manual, available from our friendly folks at the FAA. (USA)Cheers!Gerry

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All very informative, but nobody has answered Stanner (and my :) question. How do you properly fly a BC ILS approach? There is nothing in the manuals and LNAV doesn't work on most airports. By tuning into the opposite LOC signal you get the display right and can land manually, but is there no way for the PMDG models to lock on to opposite runway's LOC??? and if the answer is no ... is that realistic? do the 737, 747s have no BC option?Marten Weber

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You fly the back course ILS by loading the approach in the FMC, and use LNAV mode for lateral guidance. Use VNAV or VS or LVL CHG for pitch, whichever you like. There is NO glideslope on a back courseIf you have the SU3 updates, you would tune the localizer frequency into the radios and monitor the CDI - this is called watching the raw data, and even though your autopilot is following the FMC computed course in LNAV, you still monitor the raw data and if you deviate significantly you are expected to execute the missed approach.The Boeings do NOT have a "reverse tracking" mode for coupling to a localizer - the nav systems (GPS, INS, DME/DME) on board are more than precise enough to fly the approaches without locking on to the radio signal.-Tim

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A LOC BC can be flown with any airplane that has a nav receiver and OBS indicator. The 737 certainly qualifies. Without any computer-aided guidance, a BC is flown just like the "front" course except the logic is reversed as far as the indication of left or right of course is concerned. Normally, one can view the CDI needle as the desired course and aircraft is in the center...therefore, if the needle is left then you fly towards the needle and turn left a little. The reverse logic of the BC means that if the needle is left then you turn right a little. This is really difficult without practice, my instructor taught me to look at it as though the aircraft is now on the needle instead of in the center of the dial.. so if the needle is to the left then you need to turn right to return to the center. Having a BC button electronically reverses the sense so you don't have to play this mental game. Having a FMC is even better, you just let the computer track the course.

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Another example would be for example Curacao's Hato.With strong prevailing winds blowing in the same direction for over 90% of the year, the other end of the runway is rarely if ever used so why invest a lot of money installing the equipment?Or Schiphol, some runways are almost never used for landing, so it makes no sense installing ILS equipment on them.It's not that the airport authorities are cheap, they're pragmatic. Installation and maintenance of an ILS system costs millions, and that cuts into the bottom line.

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Hello Stanner:I know this doesn't answer your specific question, but just in case you were interested, LSZH now does have an ILS for Runway 34. You can find the specific scenery file in avsim as lszh-ils34-izs-mli.zip.If you can't find it this way, do a search for lszh ils 34 and it will be the first one on the list.Cheers,Walter MeierKPDX

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...and in case you don't have the ILS34 installed in your flight sim you can always fly the VOR/DME approach for RWY 34. This is a published approach but of course nothing for bad visibility or low cloud bases.If you don't have Jeppesen or something similar at your hands I'm sure you can find the charts on VATSIM.Regards,Markus

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>A LOC BC can be flown with any airplane that has a nav>receiver and OBS indicator. The 737 certainly qualifies.>Without any computer-aided guidance, a BC is flown just like>the "front" course except the logic is reversed as far as the>indication of left or right of course is concerned. Normally,>one can view the CDI needle as the desired course and aircraft>is in the center...therefore, if the needle is left then you>fly towards the needle and turn left a little. >>The reverse logic of the BC means that if the needle is left>then you turn right a little. This is really difficult without>practice, my instructor taught me to look at it as though the>aircraft is now on the needle instead of in the center of the>dial.. so if the needle is to the left then you need to turn>right to return to the center. >>Having a BC button electronically reverses the sense so you>don't have to play this mental game. Having a FMC is even>better, you just let the computer track the course.Not quite correct:Setting the course pointer to the front course (i.e. 090 for a BC to 27) allows the CDI to behave properly on an HSI - meaning you'll still fly "towards" the needle to correct. This is what one should do on the 737. On an airplane without an HSI, you'll have to play the mental "fly AWAY from the needle" game, regardless of the BC button.The "BC" button reverses the sensing logic for the AUTOPILOT, essentially telling it to fly away from the needle. This is useful on BC approaches, as well as when one has to fly outbound on a localizer as part of an approach procedure.Of course, as I said before, the Boeings do not have a BC button in real life. Set up the HSI to the front course so you can track the raw data, and use LNAV to direct the airplane.-Tim

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