Questions on IAP profile view

[Sam D]

I saw Kent post that he wanted to hear more from students, so here goes:

I'm taking an instrument ground course and I'm having some trouble understanding the profile view on IAP's, specifically with ILS approaches. Take this one for instance (http://204.108.4.16/d-tpp/0612/00696I32.PDF). (If the link doesn't work, it's the ILS RWY 32 at STS)

I understand that the distance from FAF to MAP is 5.3NM and that this is describing the LOC approach. I think what I don't understand is why the profile view shows going missed at the MM (or 4.8NM from the FAF). Is this saying that on the ILS you would be at DH at the MM? Therefore, you would go missed earlier if on the ILS. However, even though you'd go missed "later" on the LOC approach, you'd be at a higher elevation and still end up in approximately the same spot going missed under the LOC or the ILS.

Hope that makes sense!

 

[TMetzinger]

Yes, in this case, the middle marker is .5 NM from the threshold, and if you track the glideslope, you would be at DA there. If you were localizer only, you'd be higher, but would go missed a little later.

However, since you have to be able to descend to the runway making normal manuevers, you pretty much would have decided to go missed on the localizer earlier, but you would not actually execute the procedure until you were at the MAP.

Hope that helps.

 

[Dave Siciliano]

Let me see if I can explain it; these aren't supposed to be hard, but some are!

You didn't ask about the procedure turn, so, I won't discuss it. I would like to mention that some autopilot equiped planes need to intercept the glideslope from below it. Therefore, if using the AP, one would want to be at 3,000 at COATI or to get down to 1900 before MONES to intercept.

Decision height on the approach is 200 AGL. If you had a radar altimiter, you would set it to that. The msl height is 319, which is where you would set the altimeter. You should reach that altitude at the middle marker. From that point, at 200 AGL, you would be in a position to land in the approach area if you continued your descent at the same rate. If you don't have the runway environment in sight at this point, you would initiate the missed approach.

Note in the upper left hand corner, the indication that the mininimums are not standard if you intend to use this as an alternate.

Best,

Dave

 

[midlifeflyer]

I think you understand it just fine. The profile view is showing you the ILS - where the DA is usually co-located with the MM. And yes, while the straight-in LOC MAP is at the runway threshhold, the ILS DA is 1/2 mile before it.

 

[Sam D]

Thanks, all. This makes sense. I think my misunderstanding stemmed from some idea or assumption that since the ILS is the precision approach vs. the LOC that somehow it would bring you closer in (as well as farther down) before going missed.

Dave -- Is there something about the procedure turn that is interesting here that I should be noting? If I was, say, coming from the north, I would pick up the 141 radial of the STS VOR (or the LOC?). Once at COATI (and cleared for the approach?), I could begin a descent to 3000. The procedure turn would begin with a 45* turn to the right (heading 186), fly for (1 min?) and then turn left to intercept the LOC -- all within 10NM of COATI (based on distance if DME or GPS or time if without DME). If coming from Scaggs, Point Reyes or Sausalito VORs as the IAF, there would be no procedure turn.

 

[gismo]

Is there something about the procedure turn that is interesting here that I should be noting? If I was, say, coming from the north, I would pick up the 141 radial of the STS VOR (or the LOC?). Once at COATI (and cleared for the approach?), I could begin a descent to 3000.

Sounds good so far, assuming you realize that the route from STS to COATI is not part of the approach, just a feeder route. That means that were you told to maintain 4000 until established, you couldn't descend to 3600 at STS.

The procedure turn would begin with a 45* turn to the right (heading 186), fly for (1 min?) and then turn left to intercept the LOC -- all within 10NM of COATI (based on distance if DME or GPS or time if without DME). If coming from Scaggs, Point Reyes or Sausalito VORs as the IAF, there would be no procedure turn.

That's correct except that with the standard PT barb, you are free to reverse course via any method you want provided you stay on the barbed side. Common choices are the one you described, the reverse of that (turn right 45, fly 1 min, turn right 180, intercept, a 90-270 or a teardrop.

 

[TMetzinger]

Decision height on the approach is 200 AGL. If you had a radar altimiter, you would set it to that.

One caveat - you only use the radar altimeter for CATII or some III approaches. On Category I approaches (which I think this is), your decision comes at a specific barometric altitude, regardless of your radar altimeter (which is advisory in this case).

That's because CAT II and III airports have specific requirements for a more or less level plane extending from the touchdown zone. Using a radar altimeter in some places where the terrain varies widely around the airport could result in you delaying your decision or making it too early.

 

[Dave Siciliano]

Of course Tom. One has to know the strengths and weaknesses of all the sytems they employ.

I still set the radar altimeter because I have one and it gives me a sound warning as I hit the altitiude set on it. I'm big into backup systems. Use everything I have.

I really like hearing the radar warning go off as I hit DH on the altimeter, or to set the radar a bit higher and get confirmation I'm about to hit DH.

Best,

Dave

 

[flyersfan31]

Sounds good so far, assuming you realize that the route from STS to COATI is not part of the approach, just a feeder route. That means that were you told to maintain 4000 until established, you couldn't descend to 3600 at STS.

That's an interesting feeder, overlying the final approach course. Good point.

 

[Fast n' Furious]

Of course Tom. One has to know the strengths and weaknesses of all the sytems they employ.

I still set the radar altimeter because I have one and it gives me a sound warning as I hit the altitiude set on it. I'm big into backup systems. Use everything I have.

I really like hearing the radar warning go off as I hit DH on the altimeter, or to set the radar a bit higher and get confirmation I'm about to hit DH.

Best,

Dave

Dave,
Fine gentleman that you are, I humbly request you arrive at DA. Please do not hit anything....especially DA. Hitting anything on an approach is bad. Bad, bad, bad. Setting the rad-alt is good, good, good.
John

 

[TMetzinger]

Of course Tom. One has to know the strengths and weaknesses of all the sytems they employ.

I still set the radar altimeter because I have one and it gives me a sound warning as I hit the altitiude set on it. I'm big into backup systems. Use everything I have.

I really like hearing the radar warning go off as I hit DH on the altimeter, or to set the radar a bit higher and get confirmation I'm about to hit DH.

Best,

Dave

That's a really good use of the RA, as a sort of early warning on terrain - if it goes off when you're still a ways out, you know something is amiss.

Best wishes,

 

[Dave Siciliano]

Dave,
Fine gentleman that you are, I humbly request you arrive at DA. Please do not hit anything....especially DA. Hitting anything on an approach is bad. Bad, bad, bad. Setting the rad-alt is good, good, good.
John

Thanks John; I like to arrive <g>

 

[Dave Siciliano]

Sounds good so far, assuming you realize that the route from STS to COATI is not part of the approach, just a feeder route. That means that were you told to maintain 4000 until established, you couldn't descend to 3600 at STS.



That's correct except that with the standard PT barb, you are free to reverse course via any method you want provided you stay on the barbed side. Common choices are the one you described, the reverse of that (turn right 45, fly 1 min, turn right 180, intercept, a 90-270 or a teardrop.

Lance:

I'm having a little trouble with this; help me out. Why are you referring to 3600 at STS? I see a reference to 3000 with a line under it. Do you just mean you couldn't descend below 4,000 feet--period and chose that as an arbitrary number?

Also, I didn't see where you addressed his question about the need for a procedure turn from the other entry points. My understanding is the procedure turn is required unless provided vectors to final or unless the approach chart states no PT required. Perhaps someone can chime in if I've overlooked something.


Best,

Dave

 

[Dave Siciliano]

That's a really good use of the RA, as a sort of early warning on terrain - if it goes off when you're still a ways out, you know something is amiss.

Best wishes,

Thanks. There are times I have gotten a reading on the RA that made me question what was happening, but it is another tool I have in the kit bag and I like using it. Most places aren't an issue, as you said, big changes in terrain make a difference. I usually set it 25 feet above DH. That way I get a little oral warning just before I have to make that decision. I do have altitude intercept in the Baron but can't set it to the exact altitude.

Best,

Dave

 

[TMetzinger]

I was doing a sim session last week where I was flying a Caravan into Williamsport-Lycoming, and the "ATC" put me down to 3000, and like an idiot I complied, even though the MSA on the approach plate plainly showed 3700. There be some significant hills along the way, and the RA showing 400 feet 15 miles from the runway got my attention in a hurry. Won't make that mistake again, I hope.

 

[Dave Siciliano]

I was doing a sim session last week where I was flying a Caravan into Williamsport-Lycoming, and the "ATC" put me down to 3000, and like an idiot I complied, even though the MSA on the approach plate plainly showed 3700. There be some significant hills along the way, and the RA showing 400 feet 15 miles from the runway got my attention in a hurry. Won't make that mistake again, I hope.

We had a big debate on another board discussing whether MVAs should be available to pilots. Many times, we are vectored at an altitude we have no way to check against since they currently aren't provided. Most GA guys don't have TAWS. The Garmin 396 I have on board will give me a terrain alert when within 1,000 feet but would be little help in warning me of a significant obstacle directly ahead; no annunciator or audio alarm I would hear and it would come up pretty fast on there.


Best,

Dave

 

[TMetzinger]

Well as it turns out, ATC was wrong, MVA where we were was 4000, not 3000. I always thought that the MSA on the charts was generally lower than MVA, since MSA is terrain and MVA is radar coverage. In any case, if I'm not in good VMC I ain't excepting a clearance below MSA again unless I'm established on the approach.

 

[flyersfan31]

{quote}I'm having a little trouble with this; help me out. Why are you referring to 3600 at STS? I see a reference to 3000 with a line under it. Do you just mean you couldn't descend below 4,000 feet--period and chose that as an arbitrary number? {end quote}

Look closely at the MM -- there's a little feeder arrow and "3600 to COATI int 141deg"

My assumption was that Lance's 4000ft was, as you say, an arbitrary assumption of an ATC assigned altitude until on the "published approach."

 

[Dave Siciliano]

Well as it turns out, ATC was wrong, MVA where we were was 4000, not 3000. I always thought that the MSA on the charts was generally lower than MVA, since MSA is terrain and MVA is radar coverage. In any case, if I'm not in good VMC I ain't excepting a clearance below MSA again unless I'm established on the approach.

Wow! You're lucky to be walking around. How did you find out it was an error. Because you didn't have minimum terrain clearance? Or did you call and discuss it with someone?

I believe we are in agreement. Problem is, I am often given an MVA that conflicts with MSA. I'm often vectored to final and, of couse, we know the MSA is safe, but if there is an MVA below it, how are we to know? Maybe one of the ATC guys can chime in, but I know I have been given MVAs in areas below the MSA. One of the guys on AvSig has been a big advocate of getting this info released to the pilot, becaue, in your case, all you could go by was MSA. You can ask the controller to check, but have nothing to look at youself.

Best,

Dave

 

[flyersfan31]

Tim - was that part of the test, having ATC blow the MVA? One way or another, quite a learning experience. Better in a sim than in the real world.

 

[gismo]

Lance:

I'm having a little trouble with this; help me out. Why are you referring to 3600 at STS? I see a reference to 3000 with a line under it. Do you just mean you couldn't descend below 4,000 feet--period and chose that as an arbitrary number?

On the approach chart posted the altitude for the feeder from STS is 3600 not 3000. Were you wearing your reading glasses?

http://www.pilotsofamerica.com/forum/newreply.php?do=newreply&p=135146

Also, I didn't see where you addressed his question about the need for a procedure turn from the other entry points. My understanding is the procedure turn is required unless provided vectors to final or unless the approach chart states no PT required. Perhaps someone can chime in if I've overlooked something.

I didn't address it because Sam had it correct. And what you just said is correct except no PT is required if there isn't one depicted on the plan view. That's "shorthand" for NOPT from every IAF.

 

[HPNPilot1200]

Wow! You're lucky to be walking around. How did you find out it was an error. Because you didn't have minimum terrain clearance? Or did you call and discuss it with someone?

I believe we are in agreement. Problem is, I am often given an MVA that conflicts with MSA. I'm often vectored to final and, of couse, we know the MSA is safe, but if there is an MVA below it, how are we to know? Maybe one of the ATC guys can chime in, but I know I have been given MVAs in areas below the MSA. One of the guys on AvSig has been a big advocate of getting this info released to the pilot, becaue, in your case, all you could go by was MSA. You can ask the controller to check, but have nothing to look at youself.

Best,

Dave

I've seen many cases where MVAs are lower than MSAs. Take a look at the MSA for the ILS 27 into KBOS and compare it to this video map depicting MVAs for the area. These video maps can be displayed on radar scopes in the various facilities equipped to do so; however, there is no way to easily obtain the maps, which is unfortunate.

I suppose that since ATC is using radar vectors [when vectoring you for the approach], the MVA is what counts because the MVA meets IFR obstacle clearance (as long as the controller is vectoring you). In a non-radar situation, then the controller would have to issue clearances in accordance with the MSAs as he cannot verify your terrain clearance as accurately due to the lack of radar.

Here's what the P/CG says regarding MVA:

MINIMUM VECTORING ALTITUDE (MVA)- The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J-route segment. It may be utilized for radar vectoring only upon the controller's determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots.

It's getting late, so I haven't verified all of this with the 7110.65R yet.

Jason

 

[Sam D]

Thanks everybody. This is really helpful. I may have one or two more before I sharpen up for the written.

Sam

 

[Dave Siciliano]

Thanks Jason. That's what I've been saying, I think. In the cockpit, we can be vectored below the MSA and have no way to check the safety of that lower altitude unless we have some terrain awareness system aboard.

Best,

Dave

 

[Dave Siciliano]

On the approach chart posted the altitude for the feeder from STS is 3600 not 3000. Were you wearing your reading glasses?

http://www.pilotsofamerica.com/forum/newreply.php?do=newreply&p=135146


I guess it's just the way I read it; 'excusa me'. I think you said something like one couldn't go below 4,000; then, the 3,600 came in. I was thinking if you couldn't go below 4,000; you couldn't go below it--period. 3,600 didn't seem relavent. But I now see what you meant.



I didn't address it because Sam had it correct. And what you just said is correct except no PT is required if there isn't one depicted on the plan view. That's "shorthand" for NOPT from every IAF.

Thanks,

Dave

 

[Dave Siciliano]

Thanks everybody. This is really helpful. I may have one or two more before I sharpen up for the written.

Sam

Sam:

It helps all of us practice our skills and stay sharp. We enjoy it. It's always interesting to me to hear other people's thoughts on these. If you fly instruments, you always have something to learn.

Best,

Dave

 

[flyingcheesehead]

We had a big debate on another board discussing whether MVAs should be available to pilots. Many times, we are vectored at an altitude we have no way to check against since they currently aren't provided. Most GA guys don't have TAWS.

It sure would be nice, as history has proven that ATC'ers are not perfect.

Just curious, what were the arguments against providing MVA's to pilots?

Also... We have terrain (not certified TAWS though) in the 182. It was a $600 upgrade for the G430, and well worth it! I'd recommend that anyone flying a plane with a 430 get this upgrade.

 

[flyingcheesehead]

Well as it turns out, ATC was wrong, MVA where we were was 4000, not 3000. I always thought that the MSA on the charts was generally lower than MVA, since MSA is terrain and MVA is radar coverage. In any case, if I'm not in good VMC I ain't excepting a clearance below MSA again unless I'm established on the approach.

MSA around MSN is 3600 to the west (due to some large TV towers) and 3100 to the east. MVA is 2700 for most of the area, though I obviously don't know the exact boundaries. The highest tower is at 2549 MSL.

Since I know this area very well, I'll go below the MSA, but I do confirm if asked to go below the FAF/glideslope intercept altitude before established. (Some of the ILS's intercept at 2700, others at 2800). A couple times they've changed their mind and given me the higher altitude. Once, they just said that minimum vectoring altitude was 2700 so go ahead and descend.

I'd sure like to be able to know the MVA's, just as one extra cross-check to make sure I'm not gonna run into cumulogranite.

 

[flyingcheesehead]

I saw Kent post that he wanted to hear more from students, so here goes:

And an instrument question too! Excellent!

I understand that the distance from FAF to MAP is 5.3NM and that this is describing the LOC approach. I think what I don't understand is why the profile view shows going missed at the MM (or 4.8NM from the FAF). Is this saying that on the ILS you would be at DH at the MM? Therefore, you would go missed earlier if on the ILS. However, even though you'd go missed "later" on the LOC approach, you'd be at a higher elevation and still end up in approximately the same spot going missed under the LOC or the ILS.

Hope that makes sense!

Sounds like you understand it just fine to me.

Keep 'em coming!

 

[Dave Siciliano]

Kent:

I don't worry a lot about this around Dallas. Where I get concerned is mainly around SoCal when I go in there. Lots of mountains and times you have radar coverage and times you don't. When they start vectoring me IMC, sometimes before I'm even within 25 miles of the airport.

What's being said is these change and each TRACON has their own. They would have to report them and report all changes. They just don't want to do all that. I'm also finding this with STARS in some cases. What TRACON is actually using is not what's published. If you fly the area often, you will know what to expect, but if you don't, you'll be making some adjustments that one may not expect. Just anouther thing that can get one behind the plane if a lot is going on that one shouldn't have to deal with.

Best,

Dave

 

[Everskyward]

I think at least one of the reasons that MVAs are somtimes lower than MSAs is that the MSAs are depicted in circles that are, what, about and inch and a half in diameter? Also the angular width of each sector has to be at least a certain amount which I can't remember. ATC has a much more detailed map showing obtacles and terrain like the one in Jason's post so they can make finer altitude adjustments with the MVAs.

 

[Sam D]

And an instrument question too! Excellent!



Sounds like you understand it just fine to me.

Keep 'em coming!

Thanks, Kent. I've got another one on determining the distance on the low altitude en route chart (where no distances shown) that I'll ask the next time I'm in front of the test supplement.

 

[gismo]

I guess it's just the way I read it; 'excusa me'. I think you said something like one couldn't go below 4,000; then, the 3,600 came in. I was thinking if you couldn't go below 4,000; you couldn't go below it--period. 3,600 didn't seem relavent. But I now see what you meant.

Just jivin ya Dave, I should have pointed out where the 3600 ft altitude came from in the first post as it was not obvious at all.

 

[Dave Siciliano]

No problemo. It seems a lot of this is just communication. There's a lot of information on these puppies and sometimes my fingers just don't pound out what my brain is thinking <g>

Best,

Dave

 

[vontresc]

After reading this thread I have a question about the missed proc. There seems to be no published hold at the PYE VORTAC. I have never seen as far as I can remember a missed proc without a hold. I realize that one normally is in contact with ATC at that point, and they will usually provide instructions. So what is expected of you once you reach PYE? Also how common is it to not have a published hold on the missed?

Pete

 

[Dave Siciliano]

Pete:

I apprears the missed procedure brings you back to PYE VOR which is also the IAF to transition back to the approach.

Therefore, the missed procedure really sets you up to begin another approach attempt.

If traffic was stacked up, you might be given a hold somewhere, but none is published. I would think a hold would be likely at the IAF if approach couldn't get you right back in.

Look at the terrain in the area also; looks as if they are bringing you back out near the coast; away from the high stuff.

Best,

Dave

 

[flyingcheesehead]

Therefore, the missed procedure really sets you up to begin another approach attempt.

If traffic was stacked up, you might be given a hold somewhere, but none is published. I would think a hold would be likely at the IAF if approach couldn't get you right back in.

Wow... That really is odd though. I've never seen a miss without a published hold before, even those that are at an IAF.

Maybe there is a published hold at PYE but it's on the low enroute and not the plate? Anyone with a chart for that area care to take a look?

John, can you enlighten us? What are the TERPS requirements for showing a hold or not on the miss?

 

[Dave Siciliano]

Kent:

I'm not sure of the hold requirements: PYE is on the low altitude airway.

I often fly out of an airport farther south, near the coast: San Diego Gillespie (KSEE). Same sort of situation, in a valley near the coast. They like to take one out toward the coast to MZB (Mission Bay). If you look at that approach chart, there is no published hold on the missed there either (at MZB). What they do at MZB, is vector you back for an approach. If traffic were really backed up, you could expect a hold there even though none is shown.

If you look at the published DP for Gillespie, there is a published hold at MZB when departing if you lose com.

All of this has to work together: arrival, missed, transition to and from airways, and it has to do it for all the airports in that one area. When there are several airports in one place (like San Diego, Gillespie), each has to have a place to put folks when things back up.

My guess, and I love to hear from someone that flies here, is they can normally space you but putting you a little farther out over the water with vectors or by changing your speed unless things get real backed up. In the later case, they would give you a hold.

Best,

Dave

 

[Dave Siciliano]

Kent:

I don't have my charts at the house, but pulled up AOPA's Real Time Planner. The missed off STS appears to join a Victor Airway west of the field. V25-27 goes north from the PYE VOR on the 335 radial which is what the missed puts you on. So, after the missed, you would be joining the airway again to feed back to PYE for another approach.

As San Diego Gillespie (KSEE) they do much the same thing. The missed takes you to Mission Bay (MZB); from there, you would be brought down V66 to the Baret intersection for another approach into KSEE.

Hope this helps.

Best,

Dave

 

[Fast n' Furious]

Kent,
I think you meant this question for me. Missed approaches come in two flavors: you go to a fix and hold or you are returned to the enroute structure. This is a return to the enroute. Thanks for asking....hope this helps.

Wow... That really is odd though. I've never seen a miss without a published hold before, even those that are at an IAF.

Maybe there is a published hold at PYE but it's on the low enroute and not the plate? Anyone with a chart for that area care to take a look?

John, can you enlighten us? What are the TERPS requirements for showing a hold or not on the miss?