ILS and Distance

[Schnyd]

I was curios as to why some ILS don't give you a distance readout. For example I frequently fly out of KBLI and the ILS there does not tell me how far away I am. Where as a larger airport such as KSEA does.

[Brett_Henderson]

Some ILS have DME, some don't.

It's semi-redundant information; because once you're established on an ILS, you already know how far out you are. It's not like a VOR/DME where distance is important data.

I can be comforting to know how far out you are, before becoming established, but 99 times out of 100 ATC has vectored you in and will tell you. Plus, you'll have the approach plate in front of you... AND between outer, middle and inner markers.. AND knowing where the IAF (initial approach fix)  is, on top of knowing where the FAF (final approach fix) is... AND your missed approach point ...  there's never any doubt how far out you are....

[Mobius]

You forgot timing Brett.

My DE got on me a bit on my checkride because I didn't start my timer at the FAF in case the glide slope went out of commission.  That way you would be able to continue the approach down to the localizer minimums and find the MAP with timing (no DME).  Still strange though, there wasn't even timing on the IAP for the localizer approach that I was flying, which I asked the DE about, but he didn't really have an answer.  Oh well, I passed...

[Brett_Henderson]

Oh gosh.. there's so much ambiguity there, that you'll likely get as many answers to those questions, as you will people you ask

[Mobius]

I totally agree Brett.

The approach was the ILS 36 into Madison (http://204.108.4.16/d-tpp/0710/00245ILD36.PDF).  I agree, I've never flown an approach and held 90 kts exactly, maybe once or twice when there's no wind or turbulence or anything.  Whenever I would time an approach I would check the time at the physical MAP and I would always be off, sometimes by almost a minute.  It can be dangerous; imagine flying an approach and you depend on timing for the MAP, but you have a hefty tailwind that you try to account for, but don't get exactly right (because you can't, no matter how hard you try), so you're at the MDA still in the clouds, waiting for your time to come up, but you could already be past the MAP, even by a mile or two, which could put you into the side of a mountain.  No thanks, I'll rely on my DME and GPS and VOR intersections and whatever else I can before I trust my life with estimating wind and my ability to hold an exact airspeed.  Not to mention the situation when the controller says the magic words , "maintain best forward speed", now what?  Do you have to go missed because you're timing is off?  That's probably not a good idea.  It's just one of those things they teach you and you have to know, but never really use.

[Nexus]

I have yet to come across an ILS apporach here which allows us to actually use timing to define the MAPt whenever the GP is inop.
We're simply not authorized to do it.
And if we dont have ILS DME the MM usually acts as MAPt.

I learned a nifty trick when I flew (this only works if you have groundspeed readout)
: Instead of looking the chart for appropiate descent rate whenever your GS changes, simply multiply it by 5 in order to get a fairly precise descent rate.
Only works on standard glidepaths (3.0 degrees, 5,2%gradient)

But in general, we (in my country) cant use timing in order to define the MAPt on an ILS approach incase loss of glidepath signal. We suck.

[Mobius]

I have yet to come across an ILS apporach here which allows us to actually use timing to define the MAPt whenever the GP is inop.

That's because an ILS approach becomes a localizer approach when there is no glideslope.  No ILS uses timing to define the MAP.  DH is the only thing that defines the MAP on an ILS approach.  Sorry, I had to do it because it's been done to me so many times....

One of those stupid terminology things that seem to pop up so often in aviation...

[Brett_Henderson]

I just looked at that plate...

[Nexus]

I have yet to come across an ILS apporach here which allows us to actually use timing to define the MAPt whenever the GP is inop.

That's because an ILS approach becomes a localizer approach when there is no glideslope.

[Mobius]

I have yet to come across an ILS apporach here which allows us to actually use timing to define the MAPt whenever the GP is inop.

That's because an ILS approach becomes a localizer approach when there is no glideslope.  No ILS uses timing to define the MAP.  DH is the only thing that defines the MAP on an ILS approach.  Sorry, I had to do it because it's been done to me so many times....

One of those stupid terminology things that seem to pop up so often in aviation...

Maybe it's a misunderstanding of terms, but during those 3 years that I've been flying, I've never heard it like you described it. I feel a little embarassed  :-[

No, no, it's completely a misunderstanding of terms.  You were correct in what you said, it's just one of those  things where you can call it 10 different things and everyone will know what exactly what you're talking about.