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Guest itnomert

Capturing the Glideslope

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OK HELLO THIS IS MY FIRST POST HERE AND IM NOT SURE IF IM POSTING IN THE RIGHT AREA, OR IF MY QUESTION WILL BE LAUGHED AT BUT HERE GOES.IM USING FSX STANDARD EDITION AND FOR SOME REASON, WHEN FLYING AN ILS APPROACH THE AIRCRAFT (ALWAYS THE DEFAULT 738, I JUST LIKE IT) NEVER CATCHES THE GLIDESLOPE, NEVER! I HAVE TRIES AT DIFFERENT AIRPORTS USING DIFFERENT CAT ILS', NOTHING. ALSO ID LIKE TO POINT OUT THAT IVE NEVER HAD THIS PROBLEM BEFORE, I KNOW PRETTY MUCH WHAT IM DOING AND HAVE BEEN PLAYIN FS SINCE 2002 EDITION, EVEN THEN IT WORKED! I APPROACH THE LOCALISER AS GUIDED BY ATC ALWAYS AT AROUND 145 KNOTS AND AT THE HEIGHT IVE BEEN CLEARED TO, THE GLIDESLOPE INDICATOR ON THE PFD MOVES DOWN, FILLS FROM HOLLOW PINK TO SOLID PINK, BUT JUST KEEPS GOING DOWN , YET THE PLANE STAYS LEVEL, i HAVE THE NAV/GPS SET TO NAVCAN ANYONE GIVE ME ANY IDEAS? MAYBE SOMEONE WILL READ THIS N THINK WHAT AN IDIOT, BUT I USE FS PURELY FOR PLEASURE N I AM PROBABLY MISSING OUT SOME IMPORTANT POINT!ANY HELP WILL BE APPRECIATED! STEVEN

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Posting in capitals is the forum equivalent of shouting... not good netiquette... ;) Please post your question only once as well... ;)I assume you have the autopilot active. Generally, the capabilities of autopilots in commercial jets allow you to arm the approach prior to capture of the localizer (LOC) and glideslope (G/S). To arm the autopilot for the localizer, a LOC button normally on the dash (marked VOR LOC), above the primary flight display and navigation display (the two main displays in a 737 in front of the pilots), needs to be pressed. When the localizer becomes active (the indicator starts to move across the display), the autopilots manoeuvres the aircraft to intercept and hold the localizer. You should be at an altitude below the glideslope of course...You may now arm the approach mode by pressing the APP button marked APP and below the VOR LOC button mentioned above. As the glideslope becomes active, you will see the indicator begin to move downwards. When the indicator is 1 notch above the ideal (ie 1 notch below G/S), you should lower the gear if you haven't done so already and set approach thrust to the correct setting for the flaps setting you have. When the aircraft intercepts G/S, the aircraft will then descend on the glide, but ONLY IF you have armed APP mode... :)Hope this helps...Andrew

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You should be at an altitude below the glideslope of course...
As Andrew pointed out , you have to fly into the GlideSlopeTas

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What is the localizer needle doing while the glideslope needle is sinking? You will normally intercept the localizer before the GS.

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Thanks...I failed to mention that you should be established on the localizer prior to G/S capture...Good point, my bad :DAndrew

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aentwis put it succinctly. Whether we're on our own nav or taking vectors to the Final Approach Course, it's standard (obligatory in most SOPs) to get established laterally (tracking the localizer), and then vertically (commencing a stabilized descent on, or slightly above the glideslope). Intercepting/tracking the localizer and then the glideslope (from below) reduces the workload tremendously, because we are stabilizing one avigational dimension at a time. The most common way that I see approaches unravel is when pilots don't get stabilized well outside the Final Approach Fix. Getting stabilized smartly requires anticipating with accuracy what the required numbers will be and making them so- then making a few minimal but deliberate corrections thereafter. Reference Heading (the heading that results in a ground track parallel to the Approach Course) and Descent Rate (5x groundspeed in knots gives a good Ft/min approximation). Stir in generous amounts of situational awareness (where are you, what's next, then what & what ifs) and your approaches will start getting consistently satisfying.It's more effective to defer learning glideslope-tracking until localizer tracking is mastered. The ability to fly a straight line over the ground in various conditions is an essential skill that is best learned with a lot of comparison between visual and instrument flying. If flying straight lines over the ground is neglected in early training, it comes back to haunt an advancing pilot. But once you have that down, consistent, managed descent rates come relatively easy. The two form a tightening funnel along the narrowing "beam" of the ILS - Imagine sending a ball down a funnel the least bit crooked, and you can visualize how the error accelerates as the way tightens- a wayward ball in a funnel begins to curve and accelerate, and so do unwelcome events in a bad, unstabilized approach- to the point of busting out of the ILS "funnel" (a fragile thing of electronics and thoughts) into embarrassment, or even (IRL) oblivion. Learn to do it right, step by step- make sure you can walk straight, before doing the limbo.

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Hi,This may seem weird but is the glideslope the green arrow/triangle i see on the gps? What does it do? Does it provide you with info to line up with the runway? Can it make the plane descend and touchdown on it's own or does it enable it to center itself with the runway using the APPR button?Thanks!

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The green thing you see on a GPS (and the map too in FS if you select the option to display it) is known as the ILS feather, this is essentially a representation of the 'cone' area extending from the runway's centreline, that you fly into in order to commence an ILS approach to a runway.An ILS (instrument landing system) consists of two basic elements, the 'localiser' and the 'glideslope'. Basically, these are two very tightly focused radio signals, which are fired out from the runway along its length, up at the angle which an aircraft descends when coming in for a landing. So, you fly into the feather area, typically at less than thirty degrees off alignment of the runway's extended centreline, by commencing your flight toward the feather from a known starting location (this starting location is called an initial approach fix). If you have the runway's ILS radio frequency tuned in correctly on your navigation radio and the LOC button engaged on your autopilot, when you are within range of the localiser signal, your aircraft's autopilot will lock onto it and will line you up with the runway. You can then fly along nicely lined up with the runway's centreline, and at some point you will also fly into the upward-angled glideslope radio beam (typically you will be at somewhere between 3,000 and 1,500 feet and around 6 miles from touchdown to capture the glideslope effectively). If you have the APP button engaged on your autopilot, your autopilot will then also capture the glideslope signal and begin to descend your aircraft down the slope toward the source of the signal and consequently, on to the runway, usually at an angle of about 3 degrees, although airports in city centres, such as London City Airport have a system which uses a much steeper descent angle, in order to avoid tall buildings on the way in. Being locked onto the ILS system's localiser properly is referred to as being 'established', which is why you will hear air traffic control telling aircraft to 'maintain XXXX altitude until fully established'.To do all that, obviously you need the autopilot to be engaged (CMD) as well as having the LOC and APP buttons engaged, which are slaved to the navigation radio picking up the ILS signal. You can have other things on the autopilot such as the HEADING or NAV buttons in use too, but typically they will disengage and be overridden when the ILS signals are captured. In reality, there are several different degrees of ILS at airports, these being known as ILS categories, (CAT). Their quality of signal, how susceptible they are to interference and how many back up systems are in place at the airport (should a signal transmitter fail) are the factors which determine the category of the ILS system and how much it can be relied on in poor conditions. Major airports obviously have high category ILS systems which can be used in poor weather and for autolands right down to the point where the wheels touch the runway, but the systems on board the aircraft and the training the crews have on using those systems are also factors which affect how and whether they can be used to their fullest extent. For example, the autopilot has to be sophisticated enough to automatically flare the aircraft for touchdown and retard the throttles for a full automatic landing, and often more than one autopilot will be on board the aircraft, which is why you can see more than one CMD (command) button on the autopilot panel in an airliner. Since the localiser signal is actually transmitted from the far end of the runway, sophisticated modern airliners can continue to use the localiser signal as they decelerate down the runway to a halt and it will keep the aircraft in the middle of the runway, which means aircraft equipped with that level of sophisicated equipment can actually perform a full automatic landing and roll out in zero visibility. In most cases however, aircraft tend to perform a lower category ILS landing, where they use the ILS to get them near the point of touchdown, whereupon the autopilot is disengaged and the pilots do the last bit themselves, this is what 'decision heights' and the signals your receive from the outer, middle and inner markers are all about.ILS systems are of course ground based systems consisting of a number of radio transmitters at the airport, and whilst this system works well, several avionics companies are currently working on systems for automated landings which are independent of ground facilities. Most of these technologies are based on the aircraft knowing where it is (via GPS) and using that knowledge of its location to perform essentially the same thing as the autopilot does with a more traditional ILS system. The main problem which is slowing development of such systems is that they are fairly reliant on military satellites in order for the GPS to get a fix, and military satellites are often subject to shutdown without warning when air forces do military exercises and practice jamming them and that sort of thing.Al

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