microwave Landing systems are pretty Advanced bits of kit but unfortunately you're probably never going to see one why is that let's find [Music] out hi I'm Grant and welcome to the seventh class in the radio navigation Series today we're going to be having a look at the microwave Landing system this was a brand new bit of kit that was about to replace all the ilss of the world that didn't happen though for various regions which we're about to explore and nowadays we don't really see any microwave Landing systems in use anywhere in the world not any major airports or any Regional smaller airports either but unfortunately we still have to learn about them for the HL exams so we're going to have a quick look at them today so the microwave Landing system is not used practically anywhere in the world so why the hell are we even learning about it well I don't really know but it's still in the ATL syllabus so that's why we're going to have a look at it the main reason it's not used is that GPS and navigating using satellites has become very accurate and reliable this GPS way of navigating also requires no equipment on the ground to make an approach whereas installing a fancy new microwave Landing system would be expensive to upgrade existing ILS systems for example so it microwave Landing system kind of suffers from the wrong timing it was just a little bit too late and not worth the upgrade cost for from ILS to MLS and the GPS came in and sort of blew out the water anyway it works using microwaves which are in the super high frequency range from 3 to 30 GHz more specifically between 5 031 and 5090 mahz or you know 5.31 GHz to 5.09 GHz it uses two beams one for the vertical called the elev and one for the horizontal called the aimus both use the same frequency but are distinguisher Bill through something called multiplexing This is where multiple signals are sent out at the same time and are given each a little identifier code so it is obvious where one signal ends and the new one begins there's also a Precision DME used in a microwave Landing system which gives the distance to go to the runway which is the same as a normal DME but it is much more accurate so using the vertical and horizontal and the distance to go information it's possible to create complicated approach procedures that follow curved routes and way points in space created by this 3D uh sort of wedge that is created in the microwave Landing system this 3D approach in space can be followed by an onboard computer and it makes it much better than a standard instrument Landing system as it would allow tracks around mountains and down into valleys for example unfortunately for the MLS GPS systems and GPS prams can do the same thing as well so it's one of the ma it makes one of its major selling points a bit obsolete the horizontal guidance is provided by a fan-shaped vertical beam that sweeps back and forth within the coverage limits and an accurately timed sequence the coverage range is 40° either side of the center line out to 20 nautical miles as the beam sweeps back and forth it will hit the aircraft twice as it passes over it and returns to the starting position for example an aircraft close to the right hand side of this range we'd have the beam pass over it and hit bounce back and hit with both hits occurring very close together if the aircraft is over to the left then and the Gap in between the hits is a lot bigger it sweeps it hits it goes all the way it bounces it comes back and it hits again so by measuring these gaps and knowing the precise timing of the sweep the aircraft's position in Azimuth or the horizontal can be detected the vertical or elevation transmitter Works using the same principle a horizontal fan-shaped beam sweeps up and down within the coverage range it measures the gaps in between the passes and the precise timing of the sweep will indicate a vertical position so for example if you're at the top the beeps you the hits or the pulses the feedback it's going to be nice and close together as it sweeps it goes beep beep whereas if you're down here it's beep beep so that's how they get the position in terms of vertical space exactly the same as they do with the horizontal the vertical coverage starts from 0.9 de up to 20° up out to 20 nautical miles in distance so along with that horizontal Azimuth transmitter sort of a pizza slice shaped uh wedge is made which is slightly tipped up and approaches can be designed within this space using curves and stuff like that if possible and if there's a Precision DME a Precision DME is accurate to put in plus or minus 100 ft then that's when you can use the curved and multiple way points for the approaches if there's not a precision DME it's only straighten approaches available and slightly offset approaches which are available uh offset being just offset of the center line maybe like 2 or 3° offset from the runway and that's something that ILS systems can do another blow for the microwave Landing system in that case so the microwave Landing system suffers from the same issues that an ILS does in terms of the beams bouncing and reflecting of vehicles or mountains which means that unreliable information can be given so what we do is we set up a safe range around the transmitters just like the ILS so you get uh no vehicles or aircraft allowed into a certain area on the runway to help with that disruption and those reflection and bending of signals that can happen one of the benefits of a microwave Landing system though is that the sweeping wave can be switched off as it sweeps making an interruption so say there was a prominent mountain in the approach area the signal could be switched off briefly as it sweeps over the mountain so it does not create a reflection making a more reliable signal that is less susceptible to bending or Reflections and again if you've got that Precision DME you could even make it curve round this hill for example all in all though the biggest error of the microwave L Landing system is its timing and that GPS is cheaper and better than it hence this class being quite short and in future we'll look at GPS systems and the study of that is going to be a lot more in depth because they are way more prominent I've never seen a microwave Landing system never even heard of anybody doing a microwave landling system approach I don't know what they look like in the plane I don't know what sort of indications you would get they're just very rare but they're still in the syllabus which is why I've touched on them today but I'm not going to spend too much time on them we'll move on to the GPS stuff and have a good look at that instead no