Archived

This topic is now archived and is closed to further replies.

Guest IanSmith

MLS

Recommended Posts

Help AVSIM continue to serve you!
Please donate today!

I used to teach at KMWH which is one of the only US airports with this system and was used for testing systems on Boeing jets before they were sent overseas.I'm not sure how wide spread this technology will be used right now because they are subjected to the same rules as ILS approaches in terms of holding short a further distance away from the runway. Also GPS approaches are becoming so precise with WAAS and LAAS that we might see them replacing ILS instead of MLS. 1-1-11. Microwave Landing System (MLS) a. General 1. The MLS provides precision navigation guidance for exact alignment and descent of aircraft on approach to a runway. It provides azimuth, elevation, and distance. 2. Both lateral and vertical guidance may be displayed on conventional course deviation indicators or incorporated into multipurpose cockpit displays. Range information can be displayed by conventional DME indicators and also incorporated into multipurpose displays. 3. The MLS supplements the ILS as the standard landing system in the U.S. for civil, military, and international civil aviation. At international airports, ILS service is protected to 2010. 4. The system may be divided into five functions: (a) Approach azimuth; (b) Back azimuth; © Approach elevation; (d) Range; and (e) Data communications. 5. The standard configuration of MLS ground equipment includes: (a) An azimuth station to perform functions (a) and (e) above. In addition to providing azimuth navigation guidance, the station transmits basic data which consists of information associated directly with the operation of the landing system, as well as advisory data on the performance of the ground equipment. (b) An elevation station to perform function ©. © Distance Measuring Equipment (DME) to perform range guidance, both standard DME (DME/N) and precision DME (DME/P). 6. MLS Expansion Capabilities. The standard configuration can be expanded by adding one or more of the following functions or characteristics. (a) Back azimuth. Provides lateral guidance for missed approach and departure navigation. (b) Auxiliary data transmissions. Provides additional data, including refined airborne positioning, meteorological information, runway status, and other supplementary information. © Expanded Service Volume (ESV) proportional guidance to 60 degrees. 7. MLS identification is a four-letter designation starting with the letter M. It is transmitted in International Morse Code at least six times per minute by the approach azimuth (and back azimuth) ground equipment. b. Approach Azimuth Guidance 1. The azimuth station transmits MLS angle and data on one of 200 channels within the frequency range of 5031 to 5091 MHz. 2. The equipment is normally located about 1,000 feet beyond the stop end of the runway, but there is considerable flexibility in selecting sites. For example, for heliport operations the azimuth transmitter can be collocated with the elevation transmitter. 3. The azimuth coverage extends:(See FIG 1-1-8.) (a) Laterally, at least 40 degrees on either side of the runway centerline in a standard configuration, (b) In elevation, up to an angle of 15 degrees and to at least 20,000 feet, and © In range, to at least 20 NM. FIG 1-1-8Coverage VolumeAzimuth c. Elevation Guidance 1. The elevation station transmits signals on the same frequency as the azimuth station. A single frequency is time-shared between angle and data functions. 2. The elevation transmitter is normally located about 400 feet from the side of the runway between runway threshold and the touchdown zone. 3. Elevation coverage is provided in the same airspace as the azimuth guidance signals: (a) In elevation, to at least +15 degrees; (b) Laterally, to fill the Azimuth lateral coverage; and © In range, to at least 20 NM.(See FIG 1-1-9.) FIG 1-1-9Coverage VolumesElevation d. Range Guidance 1. The MLS Precision Distance Measuring Equipment (DME/P) functions the same as the navigation DME described in paragraph 1-1-7, Distance Measuring Equipment (DME), but there are some technical differences. The beacon transponder operates in the frequency band 962 to 1105 MHz and responds to an aircraft interrogator. The MLS DME/P accuracy is improved to be consistent with the accuracy provided by the MLS azimuth and elevation stations. 2. A DME/P channel is paired with the azimuth and elevation channel. A complete listing of the 200 paired channels of the DME/P with the angle functions is contained in FAA Standard 022 (MLS Interoperability and Performance Requirements). 3. The DME/N or DME/P is an integral part of the MLS and is installed at all MLS facilities unless a waiver is obtained. This occurs infrequently and only at outlying, low density airports where marker beacons or compass locators are already in place. e. Data Communications 1. The data transmission can include both the basic and auxiliary data words. All MLS facilities transmit basic data. Where needed, auxiliary data can be transmitted. 2. Coverage limits. MLS data are transmitted throughout the azimuth (and back azimuth when provided) coverage sectors. 3. Basic data content. Representative data include: (a) Station identification; (b) Exact locations of azimuth, elevation and DME/P stations (for MLS receiver processing functions); © Ground equipment performance level; and (d) DME/P channel and status. 4. Auxiliary data content: Representative data include: (a) 3-D locations of MLS equipment; (b) Waypoint coordinates; © Runway conditions; and (d) Weather (e.g., RVR, ceiling, altimeter setting, wind, wake vortex, wind shear). f. Operational Flexibility 1. The MLS has the capability to fulfill a variety of needs in the approach, landing, missed approach and departure phases of flight. For example: (a) Curved and segmented approaches; (b) Selectable glide path angles; © Accurate 3-D positioning of the aircraft in space; and (d) The establishment of boundaries to ensure clearance from obstructions in the terminal area. 2. While many of these capabilities are available to any MLS-equipped aircraft, the more sophisticated capabilities (such as curved and segmented approaches) are dependent upon the particular capabilities of the airborne equipment. g. Summary 1. Accuracy. The MLS provides precision three-dimensional navigation guidance accurate enough for all approach and landing maneuvers. 2. Coverage. Accuracy is consistent throughout the coverage volumes. (See FIG 1-1-10.) FIG 1-1-10Coverage Volumes3-D Representation 3. Environment. The system has low susceptibility to interference from weather conditions and airport ground traffic. 4. Channels. MLS has 200 channels- enough for any foreseeable need. 5. Data. The MLS transmits ground-air data messages associated with the systems operation. 6. Range information. Continuous range information is provided with an accuracy of about 100 feet.

Share this post


Link to post
Share on other sites

Yup, like CessnaFlyer said, this is VERY new technology and will take a while, although the ILS systems in the US are supported till 2010 like the FAA Aeronatical Information Manual says. All the info of the microwave landing system is in the very beginning (Chapter 1) of the FAA Aeronautial Information Manual. Google "FAA AIM" and you will get the whole enchilada, the real AIM which will go in depth on the MLS. I think this will be great technology to use, and will make aviation safer, because it is more immune than an ILS and it also can give data (exp. computer data, 0s and 1s :() to aircraft telling them the weather conditions, airport info, etc. which will reduce pilot load. I'm just hoping by the time this stuff becomes mainstream, there will be less use of autopilot and autoland, and hopefully the economy will get better which is contributing to the use of autopilot because airlines think that autopilot can fly more "efficiently" than the pilot. With the help of an FMC, the pilot can fly the plan very well, and not get bored staring at screens on those long hauls. What ever happened to flying over the Atlantic by hand (if you wanted) in the 20th century???, or maybe everyone should just look towards southwest... anyway that is a discussion for another time. But ya, this is great for aviation, but I just think for enthusiastic airline pilots, and ATP that LOVE flying it won't make landing any more exciting for airline pilots if they do all this autoland, LOC Hold, autopilot, etc, things, due to the greediness of airlines for money, because they think that AP is the best. I understand the use of AP in bad weather though... especially if you don't want to lose your license in CATIII conditions.

Share this post


Link to post
Share on other sites

I'm guessing I'm missing something - MLS - Microwave Landing System is actually old technology. The few MLS approach facilities that did exist in the US have been decomissioned. Two MLS approaches that I am aware of were installed at Savannah Georgia and Wilmington Delaware.I remember reading about MLS in a 1977 issue of National Geographic. I don't remember the date but I think in the mid-1980's to early-1990's the US was trying to develop MLS as a successor to ILS, and was trying to get Europe to come onboard to help with development. Europe reluctantly joined with the US, just as the US abandoned MLS development in favor of GPS. And now that the US is pressing Europe for support for its NAVSTAR GPS program, Europe is understandably reluctant and is trying to develop its own GNSS technology with Galileo.I don't see MLS replacing ILS, but RNAV (RNP) replacing ILS where terrain, political topography, or other reasons require aircraft to fly other than straight-in ILS approaches, like in airports in Lahasa China, Washington Reagan, Palm Springs Calif.

Share this post


Link to post
Share on other sites

MLS is indeed an "ancient" system, the initial experimentation of which began in Australia in 1972, with the FAA not entering the picture in the U.S. until 1975...http://en.wikipedia.org/wiki/Microwave_Landing_SystemThe last paragraph says it all (emphasis mine)...

Even before the upgrades to GPS, plans to install MLS systems quickly disappeared. The few experimental stations and those systems commissioned by FAA for public use were turned off during the late 1990s and early 2000s, much to the relief of the aircraft operators, who no longer had to install an MLS receiver. Many of these already had GPS receivers for long-distance navigation, and many have optional inputs that allow a low-cost WAAS receiver to be added.

Share this post


Link to post
Share on other sites
What ever happened to flying over the Atlantic by hand (if you wanted) in the 20th century???
Do you know how tiring that would be? :(

Share this post


Link to post
Share on other sites

Last TERPS standards published stated that all civil MLS systems have been decommissioned and that they would no longer design IAPs for them. I wish I had kept some of my old approach plates from 2001-2002, that still had the plates for the SAV MLS.There is still a MLS system in use at the shuttle landing facility and NASA has a privately designed IAP for it. I have a copy of it at home if anyone wants to see it.

Share this post


Link to post
Share on other sites

I think the shuttle used a US Navy SPN-41 system. Currently I guess the SPN-46 is the standard, which utilizes Link 4 uplink (or maybe Link 16 but I don't know). If you're landing at sea I guess you don't need TERPS :)scott s..

Share this post


Link to post
Share on other sites

I think the BBC report is more a case of a BAA PR job than anything else, and one can understand why with all the fiascos British airports and the UK's ATC system have endured in recent years.As far as 'will it ever be implemented in FS', it pretty much is already if you think about it: Apart from a few black boxes behind the dashboard, there's very little difference in how it works from the pilot's standpoint, so there's really nothing stopping a developer from utilising the ILS simulation capabilities of FS to emulate an MLS, since neither of them are using radio interception in reality, which means it's only going to be about eye candy to emulate such a receiver it in an FS cockpit.As others have noted, MLS is nothing new - in fact it's no more cutting edge than ground based stuff like Omega VLF - the real cutting edge stuff is GPS landing equipment which can use both Navstar and GLONASS satellites to effect a landing without ground-based aids, at any airport in any visibility, regardless of what they have there beside the runway. Development is progressing on GPS landing systems, in fact I was working on something for a company developing a GPS landing system well over two years ago, so you could argue even that isn't the very latest thing. Getting it approved for use by the JAA is going to be the real trick :( Al

Share this post


Link to post
Share on other sites
MLS is indeed an "ancient" system, the initial experimentation of which began in Australia in 1972, with the FAA not entering the picture in the U.S. until 1975...http://en.wikipedia.org/wiki/Microwave_Landing_SystemThe last paragraph says it all (emphasis mine)...
The following link to an ICA paper gives the background to the Heathrow installation.http://www.icao.int/icao/en/anb/meetings/a...p040_app_en.pdfIt is worth a read.

Share this post


Link to post
Share on other sites
I think the shuttle used a US Navy SPN-41 system. Currently I guess the SPN-46 is the standard, which utilizes Link 4 uplink (or maybe Link 16 but I don't know). If you're landing at sea I guess you don't need TERPS :)scott s..
Nope. :DJust looking at it, the SPN-41/46 appears to be more related to a PAR radar than the microwave system used by the shuttle. The shuttle actually uses (after a little extra research) a Microwave Scanning Beam Landing System, or MSBLS, which is fairly similar to the civil MLS system. From what info I can find, it operates at a higher frequency, more flexible placement of the ground transmitters, and greater accuracy than civil MLS. Per the FAA, it was tested to be accurate within 5cm!Here is the IAP for the shuttle MLS.

Share this post


Link to post
Share on other sites
I think the shuttle used a US Navy SPN-41 system. Currently I guess the SPN-46 is the standard, which utilizes Link 4 uplink (or maybe Link 16 but I don't know). If you're landing at sea I guess you don't need TERPS :)scott s..
As someone else noted, SPN-41 is a shipboard PAR. Link 4 and Link 16 have nothing to do with actual control or maneuvering of aircraft for landing. Link 4 is a one-way data link between a fighter control unit (either a ship or an E-2) and a fighter to vector a fighter to an intercept, and Link 16 allows ships/E-2's/E-3's/land based units to share track information with other units.There are TACAN approach plates for ships at sea, not really for terrain purposes but for setting up the marshall stacks where aircraft hold for their turn to make their approach on the carrier/ship (even then the marshall stack can get promulgated on the fly just like a land based controller can give you an unpublished hold clearance). And every ship practices the smokelight approach with its air det during workups, basically the ship throws over a smokeflare over the side every 15 seconds - the helicopter flys along until it sees a smokeflare and follows the trail of flares back to the ship.

Share this post


Link to post
Share on other sites