Approach Question.

[desertdog71]

This is one that always kind of confused me a little bit. It probably shouldn't be a big deal but just something I noticed.

Lets say we are shooting an ILS approach. Plane has no DME or GPS. It is stated that the GS Intercept altitude (denoted by the little lightnig bolt) is the FAF for a precision approach. However the LOM (maltese cross) indicates the FAF if its a non precision approach. Now lets say for example you intercept the glideslope and start your timer. Which point would you want to start your timer? This is just for redundancy of course but do you use the LOM or the GS Intercept?

I always use the LOM because that is the FAF for non-precision and the point of using the timer is because of loss of GS. Therefore making it a non-precision approach? If anybody has some thoughts on this please post them. Thanks.

[SteveC]

Easy - I don't time on an ILS (normally).

[desertdog71]

Originally Posted by SteveC

Easy - I don't time on an ILS (normally).

That is probably the real world answer. Not the way I was taught though.

[meritflyer]

It varies. There are no specific places to start your timer as its unique to each approach. Jepp plates tell you where to start it. Somtimes it is the LOM and sometimes its a DME fix.

If there is a LOM, its usually started there. If not, then its usually a DME fix.

[VDEE7]

If you don't have a GPS or DME It's hard to estimate your Ground speed based on 40mins old ATIS, not to mention surface friction as you descend, if you're category A, time over the LOM by iterpolating between 100k and 120k and try to use an earlier time to stay on the safe side, if you're approaching at higher speed time when you intercept the GS.

[tgrayson]

Originally Posted by desertdog71

This is just for redundancy of course but do you use the LOM or the GS Intercept?

It's meaningless to start a timer at the GS intercept, unless it happens to coincide with the NP FAF. If they're close, and they usually are, then it doesn't matter much. In the interests of task management, timing from the GS is good enough, considering that the method is sloppy anyway.

The only real benefit from timing an ILS that I see is that it reinforces to the student to start a timer at the FAF....some approaches *require* this, otherwise there is no way to detect the MAP. It's a hard habit to instill in a student, and allowing them to skip this step creates negative interference with prior training.

[MidlifeFlyer]

The only good reasons to time on an ILS I can think of are

(1) to create a habit of hitting the timer on an approach so it's one less thing to think about.

(2) in the case of a glideslope failure or circle to land, to identify the MAP based on timing (probably don't really need it even then if there's a MM colocated with DA).

In either case, the timing would be based on the Maltese Cross - as the approach chart itself tells you.

(tgrayson, I didn't notice your answer before I started typing)

[desertdog71]

I am sure this was to develop the habit of timing my approaches. It has been said that I can use work on my procedure instead of flying by feel all the time.

Thanks for the input guys. I figured the LOM was the correct answer since that is generally the FAF on an ILS.

Merit I did say no DME or GPS. Since most of the flying I do is slant uniform. DME would make things much easier and our Twin has DME but the primary instrument training aircraft does not. That is temporary but nevertheless a reality right now.

[meritflyer]

Originally Posted by desertdog71

Merit I did say no DME or GPS. Since most of the flying I do is slant uniform. DME would make things much easier and our Twin has DME but the primary instrument training aircraft does not. That is temporary but nevertheless a reality right now.

My bad... My bad...

[planejay]

Being as the main reason for starting time on an ILS is to identify the MAP in case of GS failure or circling, I teach my students to start the time at the maltese cross whether it is a DME fix, LOM, Int, etc. I teach this mainly for consistency of procedures and technicality (LOC approach use LOC FAF). As mentioned before, time isn't the most accurate way to identify the MAP and normally the FAF for LOC and ILS are pretty close. With that being said, In the real world I don't think it is extremely important where the time is started, as long as it is near the FAF. Forgive me for sounding contradictory.

[BuickCFI]

when do i do 5T's and/or TUPPL? as soon as i begin descent because that is glideslope intercept

[ananoman]

If there is a GS failure, you should just go missed. I don't think it is really that good of an idea to have anyone try to do a non-precision approach after briefing and starting a precision approach. You are better off going missed, rebriefing the non-precision approach and trying again.

[E6BAV8R]

Personally, I always do/taught to start it at the LOM. Either way, they are very close.

[Blackhawk]

Originally Posted by ananoman

If there is a GS failure, you should just go missed. I don't think it is really that good of an idea to have anyone try to do a non-precision approach after briefing and starting a precision approach. You are better off going missed, rebriefing the non-precision approach and trying again.

I agree, but you still need to ID the missed approach point in some cases... such as where to start a turn, if called for.

[nosehair]

Originally Posted by ananoman

If there is a GS failure, you should just go missed. I don't think it is really that good of an idea to have anyone try to do a non-precision approach after briefing and starting a precision approach.

I disagree. Standard ILS briefing: "...and if we lose the glideslope, we will continue on the localizer to MDA and xx minutes and xx seconds before missed approach."

[meritflyer]

Originally Posted by nosehair

I disagree. Standard ILS briefing: "...and if we lose the glideslope, we will continue on the localizer to MDA and xx minutes and xx seconds before missed approach."

I agree with ananoman in theory. If the GS fails, you'd go missed. If you were cleared for the ILS, you weren't cleared for the LOC approach. They are two seperate approaches and are now being assigned on two seperate approach plates.

If you're flying a PA, you cant just decide to fly a NPA. The LOC approach typically has several step down fixes so to descend down to your MDA after GS failure, may set off a MSAW. I'd suggest going missed and setting up for the NPA (LOC) approach.

[nosehair]

Originally Posted by meritflyer

If you're flying a PA, you cant just decide to fly a NPA.

OK, let me break it down into smaller elements.
IF there was nothing different, or special, or whatever, and in the briefing, I could see that the LOC and ILS are one in the same, except for the glideslope, and I am Part 91 in a small slow aircraft which I am handflying, it would be an unsafe act, IMOH, to leave a perfectly good centered LOC needle to go back up into possibly more dangerous conditions, to get re-established on this centered LOC needle and I have already prepared for this event.

And what is this deal about the 'being cleared' technicality? ATC has cleared you for the airspace - it's the same.

I've seen this trend before on these aviation forums. Looks like the 'system' is flying us. Probably comes from the complex gadrety out there which is not handflying. You gotta re-set the automatic equipment to do it for you, don'cha?

[meritflyer]

Originally Posted by nosehair

And what is this deal about the 'being cleared' technicality? ATC has cleared you for the airspace - it's the same.

No its not the same. You must be cleared for an approach. If a VOR approach has the same FAC as an ILS approach and you're cleared for the ILS, are you okay to shoot the VOR? By your logic, the airspace is cleared for you to do whatever you want.

With that logic, you're asking for a violation, IMO.

I can see your point in proceeding inbound on the LOC from a safety and situational standpoint but when you're discussing legality vs. reality, they're not the same approach and are designated on two seperate forms by the FAA. They now even have seperate approach plates. The ILS goes on form 8260-3 and the LOC goes on form 8260-5.

Conclusion? They're not the same approach and a clearance for one doesnt automatically clear you for the other.

[BuickCFI]

what if you call up "we just had a glideslope failure, continuing in on LOC only" would that be incorrect? i have done that before, once on ILS once on a GPS overlay of a VOR approach (RAIM failure)

both times ATC ok'd

[E6BAV8R]

Originally Posted by meritflyer

I agree with ananoman in theory. If the GS fails, you'd go missed. If you were cleared for the ILS, you weren't cleared for the LOC approach. They are two seperate approaches and are now being assigned on two seperate approach plates.

If you're flying a PA, you cant just decide to fly a NPA. The LOC approach typically has several step down fixes so to descend down to your MDA after GS failure, may set off a MSAW. I'd suggest going missed and setting up for the NPA (LOC) approach.

But the ILS to LOC wasn't assigned, nor planned. Yes, they are 2 different approaches and you were assigned the ILS, but I would continue the approach. It's not like your cleared for the ILS and then secretly saying your going to do the LOC approach - based under the circumstances your required to the LOC approach because the GS failed in the middle of the approach.

I would continue the approach - its not like its a big juncture here to compensate for it; one should be starting the times and planning for a GS failure anyway.

[SteveC]

Originally Posted by E6BAV8R

I would continue the approach - its not like its a big juncture here to compensate for it; one should be starting the times and planning for a GS failure anyway.

I would tend to agree if we are only talking about "handflying small, slow Part 91" aircraft. (Someone added that caveat later in the conversation) Larger/faster equipment brings some additional factors into consideration.

[ananoman]

It's not so much what you are cleared for, I don't think this is much of an issue. I have been cleared for an ILS approach even when the GS is inop. That is the title of the approach plate and I don't think ATC cares which one you do.

The issue is the briefing. If you are briefing an ILS and are going to configure for an ILS, you should probably not try to reconfigure after a GS failure and then worry about any stepdown fixes or what the MDA/MAP is now that you are not doing an ILS. The more you complicate things close to the ground, the more you are asking for trouble.

If you are flying a simple single and are using the same config. for either an ILS or a LOC, and there are no step downs, it may be ok. But, then again it really depends on who your student is. If they are going to be a professional pilot and are going to be flying a lot, it is probably safe for them to do this, but is a bad habbit that could bite them later as they move up to faster and more complex equipment. If they are the average private pilot that will not be flying that often, then you are teaching them to do something that is potentially very hazardous. A GS failure is a rare event. Doing a go around is not dangerous and we train for it. Changing approaches in the middle of the game is not something we train for (at least I don't) and only a little mistake can be fatal.

[E6BAV8R]

Originally Posted by SteveC

I would tend to agree if we are only talking about "handflying small, slow Part 91" aircraft. (Someone added that caveat later in the conversation) Larger/faster equipment brings some additional factors into consideration.

...and I would agree with that I thought we were refering to "Part 91" aircraft.

[SteveC]

Originally Posted by E6BAV8R

...and I would agree with that I thought we were refering to "Part 91" aircraft.

Like a Citation X or Falcon 2000 or G-V or Embraer Legacy or...?

[dc3flyer]

I agree with nosehair... Start the time just in case and SHOULD the glideslope fail prior to LOC MDA, shoot the LOC. Almost every ILS also has a LOC, when cleared for the approach, ATC doesn't care which one you do. As long as you know what to do, you can do the LOC.

It is a good thing to teach that you should go missed, but if you are burning someone else's money in gas (like in a Citation, Falcon, Lear, etc...), they don't want you to go missed if you don't have to.