ILS question

Why are so many runways equipped with only one ILS? Just how expensive are ILSs? After all, it's just a radio transmitter, correct? They don't even need the markers.

After all, it's just a radio transmitter, correct?

Yes and no. Helpful answer, huh?

It's a radio transmitter, yes. JUST a radio Tx, no. The radio part has got to be weather proof, and the frequency has to be very precise. Not only that, it has to transmit 24/7. Hard on radios, considering most spend most of their time NOT transmitting, so the receiver can "listen". Hard on the higher power portions of a transmitter. It must also be kept cool, as transmitting a signal like an ILS takes some power, meaning heat in the transmitter section that has to be removed to prevent damage.

The antenna is fairly unique, as well. Most radio's have omni-directional antennas. They transmit in all directions at once. ILS have a directional antenna, and it has to shape the beam pattern in a very specific manner. Not the cheapest piece of equipment.

So far so good, yes? Now comes the expensive part. I don't know for sure, but knowing the FAA, I'll wager they require the ILS to be aligned on a certain interval. That's frequency AND beam pattern. Frequency isn't hard, although a frequency counter and O-Scope is a fairly expensive investment. The expensive part is getting them aligned, again, on a specific interval. That must be done by specific companies, and they must be re-certified and inspected on a specific interval. Not cheap.

Aligning the beam pattern, honestly, probably requires a couple spirit levels to accomplish. Not super expensive.

The really expensive part is the tech's time. We don't come cheap, and the better we are, the more we cost. We get a ton of training to get to a decent level of expertise, though, and THAT isn't cheap either. Yes, I was a techie, both in and after The Corps. Obviously, while I was in, my wages were no higher than any other Sergeant's (E-5), but once I got out, they doubled, and kept on rising from there. And to top it all off, the tech must be FAA certified every so often, and if they are under contract to a specific airport, or variety of airports in a certain area, the entity the hires the tech pays for the certification.

 

So, an ILS IS a radio, yes, but a very unique type, with some expensive requirements. The more ILS an airport has, the more expensive it gets.

 

Does this help any?

Pat☺

It's two transmitters and antennae, localizer and glide slope. Three if you add DME. Plus upgraded runway markings and lights, possibly, plus approach lights. It can add up quickly.

 

IIRC, I was once told an airport spent $175,000/year just on ILS maintenance. I will try to verify that.

 

It can be quite a bit of cash, especially if it is not needed very often. Most places have prevailing winds that bring bad weather, negating the need for additional ILS.

 

With the future being in GPS approaches, adding an ILS these days is probably not economically feasible.

 

peace,

the Bean

Pat gave you most of the technical details, and String added extremely relevant information, completing the picture. If you add in the fact that an ILS was actually developed during WW II (old technology), and that it's a very low volume system (meaning that they don't have the economies of scale that you find in, say, a TV), as well as the very specialized requirements that Pat described (for EACH transmitter/antenna/support eqpt), you get expense quickly. Perhaps that also helps you understand why the back course approaches came into use, and why most non-airline airports don't have ILS.

 

Oh, yes -- the FAA must periodically check-fly each instrument approach of any kind, including ILS, so to have more would also increase the government expense and work load, as well as that of the airport.

It's two transmitters and antennae, localizer and glide slope. Three if you add DME.

 

Very true, Mr. Bean, sir. And they all three have the alignment requirements I mentioned. Maybe not the DME, as long as it's functional.

The localizer and glideslope radios can be placed in the same weather-proof box, but this just increases the cooling requirements for it. The more transmitters operating in the same box, the hotter they get. Now, you not only have the actual electronic side of the house, but you need an AC specialist. Electronics just don't get along with heat at all.

Even more expensive to maintain and align.

Alternatively, they can be placed remotely, perhaps in a small building, with an AC unit on it, and a cable run to the antennae. Now, though, every cable connection is subject to corrosion, water intrusion, dirt, insects and so on, and they must be maintained. AND the AC must be operational 24/7. Costs to operate and maintain. AND the electronics. Maybe a back-up for each item. Transmitters, AC unit(s), and so on.

The costs just keep adding up...

 

Pat☺

I have read that Louis Armstrong airport was the first to use an ILS.

 

This all pretty much answers my question. Thanks.

 

I have one more. How many watts do the ILS systems put out? I'm sure glideslope, LOC and DME all put out the same wattage.

 

Just in case, I'm a radio communications enthusiast. I almost got my Ham radio licensee. LOL Haven't tried again in years. That was back in high I now dabble in scanners mostly.

Just as further info, this Ind. Univ. site provides a bunch of good info.

 

An ILS (and many other facilities) is required to have backup power, in addition to the normal power operation (generator, etc.), as well as failure monitoring.

 

Marker beacons are also part of the ILS. Outer, Middle and, sometimes, Inner markers are 75 MHz fan markers. Then there is the LOM (Locator Outer Marker), an NDB band transmitter.

 

At least one reference I come across says the localizer (which is in the VHF band) runs up to 17W and the glideslope (in the UHF band) runs up to 5W, while the fan markers run as low as 3W, but the LOM may run as high as 400W if it can also serve for weather broadcasting.

 

And finally, if you were to search on Wikipedia you'd find most of the information you've had here. Try this web page.

The localizer and glideslope radios can be placed in the same weather-proof box,

 

As the antennae are separated by a mile or two (opposite ends of the runway) I find this highly unlikely.

 

peace,

the Bean

 

[added]yes, DME is omnidirectional[/added]

Thanks. Do pilots generally match the Morse code with the ILS?

Yes, unless they're foolish.

Notice that every now and then you read/hear about a plane landing at the wrong airport. A C-17 did it recently, although they got it out by unloading it, and really running the engines up before they started the take-off roll. I can't recall the commercial passenger plane that did it recently. It landed at an airport that looks a lot like the one they were aiming for, and was on the same approach path.

I'll wager neither of those two PIC's listened to the Morse Code transmitted by their target airport's ILS. I'd also wager, after those incidents, a lot of pilot briefings included the company/squadron's requirements to listen to the Morse of the ILS they were on...

Has to be pretty embarrassing!

Not to mention expensive. The company had to send a crew in to fly the bird out to it's proper airport, and if the squadron hadn't had a Sierra Hotel pilot (female, by chance, IIRC), they would have had to send in an entire crew to disassemble the C-17, truck out the parts on special trucks, then reassemble it at an airport it could get out of. Not to mention, they'd probably have to get it re-certified airworthy once they got it all back together. Talk about COSTS the squadron doesn't have in it's budget!! They still had to send a crew and some equipment, like forklifts, to unload it before they could try to get it out. Costs again. I'll wager the CO was a little dis-satisfied with the crew of the plane.

 

IOW: LISTEN to the Morse Code you're getting! You don't have to have it running constantly, but verify what you're receiving vs what's on the approach plate. Yes, this is a sim, and you land at the wrong airport, who cares? But a lot of us like to at least TRY and get things as correct as possible.

 

And have fun :D

Pat☺

Thank you for the answers! Much appreciated. I asked this real-world pilot who has a YouTube channel and a Facebook page called FlightDeck2Sim and he never answered.

 

 

Yeah, since it's the Sim, I really don't care if I match the Morse code with a plate. I don't even use plates unless I'm in a PMDG 737 in VATSIM, but that's been years. I mostly just use the ol' GPS in my Lear 45 and F22. I do turn on the Morse code audio as it's cool to hear what it sounds like and it gives me an audible que that I'm withen range of the LOC.

I suspect most 'wrong airport' landings are visual landings, not ILS.

 

Pat, if you are referring to the C-17 incident at Tampa, that was most definitely a visual landing as Peter O'Knight is not equipped with an ILS.

 

I would think the most dangerous situation where ID-ing the ILS would be most critical would be during parallel runway ops.

 

Bottom line, if you want to pass your checkride verify ID on all navaids. ;)

 

peace,

the Bean