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JWMuller

The ILS and the Course select

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@Billcoke, please don't quote messages in full when responding. For users with mobile phones it means unnecessary data consumption. Tagging the poster you are answering like I have done here is usually sifficient unless there is a specific statement you wish to refer to.

Thanks.


Ray (Cheshire, England).
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6 hours ago, Ray Proudfoot said:

@Billcoke, please don't quote messages in full when responding. For users with mobile phones it means unnecessary data consumption. Tagging the poster you are answering like I have done here is usually sifficient unless there is a specific statement you wish to refer to.

Thanks.

Is this a new rule Ray?  I've not seen it mentioned before and WE'VE been doing it for years...

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7 minutes ago, trumpetfrazz1 said:

Is this a new rule Ray?  I've not seen it mentioned before and WE'VE been doing it for years...

It’s not so much a rule as having consideration for those on phones etc. who don’t have a generous package. Quoting is only relevant if you refer to it in your reply. But quoting a long post and giving a brief reply doesn’t benefit anyone.

Probably because the poster is new. Just a polite request not to quote in full  unnecessarily.


Ray (Cheshire, England).
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I would much prefer for folks to simply highlight a short portion and then use the popup "Quote selection" button:

G7R7G.png

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Fr. Bill    

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12 hours ago, Ray Proudfoot said:

@Billcoke, please don't quote messages in full when responding. For users with mobile phones it means unnecessary data consumption. Tagging the poster you are answering like I have done here is usually sifficient unless there is a specific statement you wish to refer to.

Thanks.

noted, thanks

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On 7/15/2020 at 8:20 PM, Chock said:

 

The most common method for approaches where there is no ILS, is to use a VOR/DME Approach. VOR beacons can be tuned into, then you can select a course to or from that beacon which an autopilot can lock onto if need be. In other words, if I am landing at an airport with a runway on heading 09 degrees, and there is a VOR/DME beacon on that airport, if I tune it in and select a course heading of 090, I can use my avionics to line me up on the correct heading for an approach to that runway although I will need to look at the charts for that approach to ensure I am clear of terrain etc.

Airports such as TNCM (Princess Juliana ) publish VOR/DME charts to assist with the correct course to fly and the correct altitudes to be at to fly a VOR/DME Approach. You can see some of those here.

 

I notice those airports that use VOR/DME approach, why don't they install the VOR/DME right infront of the runway, so that the bearing is align perfectly with the runway, rather than install at the side of the runway, which is 2-3 degree offset.

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3 hours ago, Billcoke said:

I notice those airports that use VOR/DME approach, why don't they install the VOR/DME right infront of the runway, so that the bearing is align perfectly with the runway, rather than install at the side of the runway, which is 2-3 degree offset.

You would think so wouldn't you? However, VOR/DMEs are pretty big, since they have to have a series of radial antennas in order to be able to do what they do. So it's not always practical to put them anywhere you like purely for the size of the things. Here is a picture of one below, this is fairly typical of what they look like, but sometimes they have taller antennas which would of course mean there's an obstacle near the runway if you put one right at the end of a runway. I'm not sure how tall the one in the pic is, but I would guess the tip of the pole antenna is about 60 feet tall:

Warburg_-_2018-04-19_-_Drehfunkfeuer_DVO

Beyond this, you might have noticed at the hold point on the taxiway just before you turn onto a runway with an ILS, that there are in fact two hold points. There is one right near the edge of the runway, but there is another one which is called the ILS hold point that is normally quite a bit further back away from the runway. This is where aircraft hold position if something is coming in for an ILS approach, and they stop at this point because the metal in the aircraft which is holding can interfere with the ILS antennas, so you would want the aircraft to be far enough away from the antennas to not have this happen.

The same can be true for VOR/DMEs. They are usually well away from other stuff such as big dense structures so that they do not get interference from these structures and they are often placed at the highest available point so that their signal is not blocked by terrain in any of the 360 degree directions which their signal is being transmitted. An ILS signal does not have this problem and only really needs to transmit a single beam a few degrees wide out in one specific direction, so there is basically less of a problem in achieving that because most runways are of course aligned so that they have a path in toward them which is clear of terrain for obvious reasons.

Sometimes there are runways which cannot easily have an ILS for this reason, for example, they might have some high terrain around them which requires a somewhat offset approach. Or sometimes there might be a high amount of iron ore in surrounding hills or some kind of local magnetic anomaly which precludes the ability to have a clear signal from an ILS. Occasionally, the reason could be that the surrounding terrain creates difficult gusts or weird localised wind anomalies.

The most famous (now defunct) example of one such runway which necessitated some fancy trickery with its ILS system owing to terrain clearance issues, was the approach onto runway 13 at Hong Kong's Kai Tak Airport, known as the Chequerboard Approach. This used a heavily modified ILS system for part of the approach (the system was called the IGS - Instrument Guidance System - to make it clear that it was not intended to be used for the entire approach) and it would allow the pilots to line up with the famous big painted Chequerboard on the side of the hill above Kowloon Tsai Park, whereupon the aircraft had to then make a 47 degree turn to align visually with the runway. It did offer some glideslope and localiser guidance, but not so that an autopilot could fly it.

The chances are, something like the old Kai Tak Chequerboard approach would never be approved these days though, it  kind of evolved with the airport and was tolerated because with the winds at Hong Kong being the way they are and technology being waht it was at the time, there was no other real option other than to come in for the Stonecutter DME approach to the runway, which did not use any of the localiser or glideslope guidance that the IGS offered for the Chequerboard Approach.

With the advent of more accurate and sophisticated systems such as GPS and GLONASS, ILS-like approach can now be implemented without there actually being dedicated glideslope and localiser antennas, since the GPS can replicate these, so we may in the future see more of this kind of thing, but this sort of stuff takes years to become commonplace in something like aviation when there is already an infrastructure which everything is geared towards in terms of avionics and radios.

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Alan Bradbury

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2 hours ago, Chock said:

You would think so wouldn't you? However, VOR/DMEs are pretty big, since they have to have a series of radial antennas in order to be able to do what they do. So it's not always practical to put them anywhere you like purely for the size of the things. Here is a picture of one below, this is fairly typical of what they look like, but sometimes they have taller antennas which would of course mean there's an obstacle near the runway if you put one right at the end of a runway. I'm not sure how tall the one in the pic is, but I would guess the tip of the pole antenna is about 60 feet tall:

Nice photo! That particular VOR is larger than some, but all VORs take up too much horizontal and vertical real estate to be placed right at the end of a runway. 

DME is different, as a DME only requires a single vertical radiator, and many ILS installations do have a DME installation at the runway threshold. The tall mast on the left side of the photo is probably the DME associated with this particular VOR.


Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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5 hours ago, Chock said:

 

The most famous (now defunct) example of one such runway which necessitated some fancy trickery with its ILS system owing to terrain clearance issues, was the approach onto runway 13 at Hong Kong's Kai Tak Airport, known as the Chequerboard Approach. This used a heavily modified ILS system for part of the approach (the system was called the IGS - Instrument Guidance System - to make it clear that it was not intended to be used for the entire approach) and it would allow the pilots to line up with the famous big painted Chequerboard on the side of the hill above Kowloon Tsai Park, whereupon the aircraft had to then make a 47 degree turn to align visually with the runway. It did offer some glideslope and localiser guidance, but not so that an autopilot could fly it.

 

Another airport I can think of is VNKT - Kathmandu Tribhuvan Intl Airport. Given the high terrain, it is impossible to install ILS

 

500460209_VNKT-NavigraphChartsRNP.thumb.

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Show the chart to a pilot of a piston powered single engine STOL GA. Yeah, yeah,, bit of a tight airport to get into.... hills all around, no biggie, I got STOL, baby. I get in anywhere ......HOLY C...  :blink:look at the minimum safe altitude diagram.. :unsure:

(I know, I know the airport elevation is only 4395 feet and a 172 can manage it, but it's still an interesting chart!)

:cool: Cheers, Bill.

 


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A few years ago we had the Boeing test and product pilots Come over to  us to deliver a safety symposium.

I remember them talking about the future of these sorts of GPS based approaches and saying “never make a DIRECT TO  a Waypoint inside the IAF....you only get to do that once “

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15 hours ago, Chock said:

 

The most famous (now defunct) example of one such runway which necessitated some fancy trickery with its ILS system owing to terrain clearance issues, was the approach onto runway 13 at Hong Kong's Kai Tak Airport, known as the Chequerboard Approach. This used a heavily modified ILS system for part of the approach (the system was called the IGS - Instrument Guidance System - to make it clear that it was not intended to be used for the entire approach) and it would allow the pilots to line up with the famous big painted Chequerboard on the side of the hill above Kowloon Tsai Park, whereupon the aircraft had to then make a 47 degree turn to align visually with the runway. It did offer some glideslope and localiser guidance, but not so that an autopilot could fly it.

 

Princess Juliana TNCM is a busy airport, often see many big jetliners, like 747, 777, A320 land on this airport. Is there a reason why they choose to install VOR/DME instead on ILS, easier for the pilot to align the plane to the runway and perform autoland too.

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8 hours ago, HighBypass said:

Show the chart to a pilot of a piston powered single engine STOL GA. Yeah, yeah,, bit of a tight airport to get into.... hills all around, no biggie, I got STOL, baby. I get in anywhere ......HOLY C...  :blink:look at the minimum safe altitude diagram.. :unsure:

(I know, I know the airport elevation is only 4395 feet and a 172 can manage it, but it's still an interesting chart!)

:cool: Cheers, Bill.

 

What is the consequence if the pilot set the BARO lower ( eg: 3000ft) than the correct minimum safe altitude during the approach?

Edited by Billcoke

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