DME Required?

flyingron

flyingron

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OK, terpsters, here's one that has been bouncing around the EAA forums.

On this plate:
http://155.178.201.160/d-tpp/1605/06210IL9.PDF

The notes start with DME Required. The only DME on the entire chart is the missed approach hold intersection, though that seems to be easily indentified by the two radials depicted (one of which you're already tracking as part of the procedure). Why not allow DADES to be identified by the cross radial? Is there significance to the fact that the missed approach procedure mentions the hold as "DADES/LAL 25.8 DME."
 
I believe if it says DME required then it means DME is required to fly that approach. That would be my answer in a check ride. But real world?
 
I suppose it could say "DME or dual navigation receivers required", but maybe the government is trying to economize in their use of ink?
 
Could always just use a IFR GPS too.

But per the question if it says you need DME, you need DME or a IFR GPS in lieu

Meat a potatoes, from looking at it you could shoot it with dual nav heads, or a EHSI/RMI, but for whatever reason the FAA gods said you need DME, so..
 
I've seen this is a few other approaches and have always wondered about it. I'm definitely not a terpster, so proverbial grain of salt:

Ron, I agree that DADES is the only one that needs DME. But there are some other clues. BROAD, which could also be identified by the intersection of a PIE radial and the localizer, requires radar. And a quick look at the en route chart* indicates the MEA is 5,000 but 2000 is acceptable for GPS, and, at least for the crossing airway, the MRA is 5,000'

Put that together and it looks like there are reception issues off PIE in that area precluding its use for identifying DADES.

[*I have discovered through the years that a very large percentage of "why" questions about an approach can be answered by remembering they don't exist in a vacuum and looking at the en route chart]
 
PIE is unusuable on that radial at that distance, at the specified missed approach hold altitude. Therefore, DME is the only way to identify the missed approach holding fix.

Screen Shot 2016-05-22 at 11.43.56 AM.png
 
dmspilot said:
PIE is unusuable on that radial at that distance, at the specified missed approach hold altitude. Therefore, DME is the only way to identify the missed approach holding fix.

View attachment 45502
Click to expand...
Which dovetails nicely with what I saw on the en route chart. Hadn't thought of checking the Chart Supplement. Nice job!
 
flyingron said:
OK, terpsters, here's one that has been bouncing around the EAA forums.

On this plate:
http://155.178.201.160/d-tpp/1605/06210IL9.PDF

The notes start with DME Required. The only DME on the entire chart is the missed approach hold intersection, though that seems to be easily indentified by the two radials depicted (one of which you're already tracking as part of the procedure). Why not allow DADES to be identified by the cross radial? Is there significance to the fact that the missed approach procedure mentions the hold as "DADES/LAL 25.8 DME."
Click to expand...

DADES is an intersection but has an MRA of 5000' when LAL R-330 is the tracked course. The missed approach procedure has aircraft holding at 3000' on that radial so DME is required. Methinks it would have been better to leave the PIE R-045 off of the plate.
 
flyingron said:
OK, terpsters, here's one that has been bouncing around the EAA forums.

On this plate:
http://155.178.201.160/d-tpp/1605/06210IL9.PDF

The notes start with DME Required. The only DME on the entire chart is the missed approach hold intersection, though that seems to be easily indentified by the two radials depicted (one of which you're already tracking as part of the procedure). Why not allow DADES to be identified by the cross radial? Is there significance to the fact that the missed approach procedure mentions the hold as "DADES/LAL 25.8 DME."
Click to expand...

As Ron says, the MRA from PIE is 5,000. The distance from ORL is 49.5 miles. TERPs, Chapter 2 limits a VOR that forms a holding intersection to a max of 45 miles and a minimum angle of 45 degrees. So, nothing qualifies except for the DME fix shown.
 

Attachments

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aterpster said:
TERPs, Chapter 2 limits a VOR that forms a holding intersection to a max of 45 miles and a minimum angle of 45 degrees.
Click to expand...
Ah! That's the TERPS piece. Thanks.

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°.
(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:
(a) If an NDB facility is involved, 1° for each mile over 30 miles.
(b) If an NDB facility is NOT involved, 1/2° for each mile over 45 miles.​
 
The logic of the chart is: The note states DME Required. The pilot doesn't question the note, he doesn't fly the approach unless he has DME (or GPS substitution). If he flies the missed approach the presumption the FAA makes is that he will use DME rathen that try to use an intersection. Sure, they could have a note at the missed approach fix, "Use DME for DADES." But, using that logic notes would become endless.
 
aterpster said:
The logic of the chart is: The note states DME Required. The pilot doesn't question the note, he doesn't fly the approach unless he has DME (or GPS substitution). If he flies the missed approach the presumption the FAA makes is that he will use DME rathen that try to use an intersection. Sure, they could have a note at the missed approach fix, "Use DME for DADES." But, using that logic notes would become endless.
Click to expand...
I think most everyone realizes that when we are flying, "I need that," is the only consideration. When not flying, it's more interesting to some than to others the reason why.

Of course, using the logic in reverse gets us to another existing discussion: why not only one nice big DME REQUIRED on a chart? (well, maybe two, since the DME required by being in the title of an approach has some additional meaning).
 
aterpster said:
The logic of the chart is: The note states DME Required. The pilot doesn't question the note, he doesn't fly the approach unless he has DME (or GPS substitution). If he flies the missed approach the presumption the FAA makes is that he will use DME rathen that try to use an intersection. Sure, they could have a note at the missed approach fix, "Use DME for DADES." But, using that logic notes would become endless.
Click to expand...

If they used logic the PIE R-045 would not appear on the approach plate.
 
roncachamp said:
If they used logic the PIE R-045 would not appear on the approach plate.
Click to expand...

They do use that logic and the PIE R-045 appears on the chart because that is the way it is composed on the 8260-2 DADES has other uses as well. I suppose the AIS designer, though, could have instructed the charting entities "Do not chart the PIE R-045 at DADES."

It's not a perfect world, though.
 
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