I admit it, I'm stumped. Can't figure out why DME is required for that approach, other than the fact the plate has "DME required" printed on it. Help?http://155.178.201.160/d-tpp/1605/06210IL9.PDF
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I admit it, I'm stumped. Can't figure out why DME is required for that approach, other than the fact the plate has "DME required" printed on it. Help?http://155.178.201.160/d-tpp/1605/06210IL9.PDF
I THINK it's due to the DME requirement on the missed. Can't see any other reason...Quote:
Originally Posted by Mike M
It appears to be for the missed approach procedure.
Radar &or outer marker define BROAD and EBELS. The middle marker &or glideslope+DA &or timing define the missed approach point depending on ILS or LOC approach. So DME isn't used for the approach. So I thought DME was just to find DADES intersection for the missed approach. Until it was pointed out to me that GPS can substitute for DME. But it doesn't have to. DADES is defined by either the LAL 330@25.8 DME or the intersection of the LAL 330 and the PIE 045. Is there some other reason for DME than defining DADES? I know when y'all point it out I'll go DDDDUUUUUHHHHH but I am stuck on stupid right now.
GPS substituting for DME won't affect DME Required (or DME being in the name of the approach).
I'm stumped as well. Can't see why you can't find DADES with the PIE 045 radial. You're going to be on the LAL 330 anyhow by the time you're looking for it.
I'm not so sure about that. If what you say is a true statement, the missed approach procedure language would be:Quote:
Originally Posted by Mike M
MISSED APPROACH: Climb to 3000 on heading 090 and LAL R-330 to DADES and hold.
That would give the option to use any authorized method to identify DADES.
But it doesn't say that. They purposely included a radial / DME fix in addition to DADES intersection. That would trigger the DME required note.
Appears to be a technicality with using DME to identify DADES so they essentially overlayed a DME fix. Definitely worthy of research but I need a real computer :(
One problem I see is 10th of a mile increments are never used to identify enroute fixes.
Someone could pop over to POA and see if Wally can make a read on this.
Marty, you're on the right track. IMHO, the intersection is not defined by two radials. DME is more accurate, and its only 25DME from Lakeland Vortac. If the radial from St Pete Vortac were used to ID the int. you could have a sizeable error. PIE is almost twice the distance as LAL is. Service volume of PIE is about 40 miles. Allowing for max error for a VOR ck of six deg. it could make an error of 4 to 5 nm. (Just doing mental calcs.) And a "slash G" gps has been approved as a substitute for a decade or two.
With the smarter stuff you guys put out I looked up DADES more carefully. FAA JO 7350.9E defines it as: GNV*C*183.21/79.57 LAL*C*329.77/25.83 ORL*C*257.70/49.69PIE*C*045.00/35.59 28-21-45.6200N 082-15-07.8000W The 35.59 nm from PIE is close enough to be within the service volume of both low or high VORs but not a terminal VOR. And PIE is a H VOR. Should be close enough to use radials, so why not? Wait, there's more! "PIE Remarks: VOR PORTION UNUSBL 025-054 BYD 21 NM BLO 5000 FT, 233-250 BYD 20 NM." Well, well, well. That's why PIE and LAL radials don't define DADES. So even though the missed approach is sequentially shown on the side view of the procedure as going to DADES, the expanded verbiage in the upper right hand corner tells which of the 5 ways to define DADES must be used for this SIAP. And that requires DME or a suitable substitute but the plate would still say "DME Required." Thanks, folks. Anything else?
Yep MikeM is mostly right. Not only is the radial from PIE unusable for this purpose by the published information, there are problems with this plate design. From the guys over on POA quoting the TERPS:
Holding Fixes. Any terminal area fix except overheading a TACAN may be used for holding. The following conditions shall exist when the fix is an intersection formed by courses or radials:
(1) The angle of divergence of the intersecting courses or radials shall not be less than 45°.(a) If an NDB facility is involved, 1° for each mile over 30 miles.
(2) If the facility which provides the crossing courses is NOT an NDB, it may be as much as 45 miles from the point of intersection.
(3) If the facility which provides the crossing course is an NDB, it must be within 30 miles of the intersection point.
(4) If distances stated in paragraphs 287b(2) or (3) are exceeded, the minimum angle of divergence of the intersecting courses must be increased at the following rate:
(b) If an NDB facility is NOT involved, 1/2° for each mile over 45 miles.
Holding Fixes. Any terminal area fix except overheading a TACAN may be used for holding. The following conditions shall exist when the fix is an intersection formed by courses or radials:
(1) The angle of divergence of the intersecting courses or radials shall not be less than 45°.(a) If an NDB facility is involved, 1° for each mile over 30 miles.
(2) If the facility which provides the crossing courses is NOT an NDB, it may be as much as 45 miles from the point of intersection.
(3) If the facility which provides the crossing course is an NDB, it must be within 30 miles of the intersection point.
(4) If distances stated in paragraphs 287b(2) or (3) are exceeded, the minimum angle of divergence of the intersecting courses must be increased at the following rate:
(b) If an NDB facility is NOT involved, 1/2° for each mile over 45 miles.
The consensus is the MRA precludes using PIE's radial to identify the fix and further, the TERPS would forbid it even if the PIE radial was legally usable (no MRA). The fact that a PIE radial is shown going to DADES is a massive red herring. It should NOT be there.
You're no fun if you are going to answer your own questions :(Quote:
Originally Posted by Mike M
Great job on the investigation Mike!!!
I think it's SOP to show the fix as depicted because it is part of the low altitude route structure. The IAP chart specifically limits how the fix can be defined for terminal procedures.Quote:
The consensus is the MRA precludes using PIE's radial to identify the fix and further, the TERPS would forbid it even if the PIE radial was legally usable (no MRA). The fact that a PIE radial is shown going to DADES is a massive red herring. It should NOT be there.
Marty, I didn't know where to look until people started helping out. And I still don't know if that's all of it! Somebody always seems to know "the rest of the story"........Quote:
Originally Posted by martymayes