2 Questions

[stillaboo]

So I guess the real question is "where did Peter Dogan find the reg that allows us to descend?"

All it took was one guy to write something in a book . . . and all it will take is another guy to find something in a book (a regs book).

Just so you know, I'm running this on 2 ATC boards as well, and they are right with us, stumpted.

-Boo!

 

[A Squared]

I asked Don Brown about this, Don is a controller and Safety Rep at Atlanta Center and writes an ATC column for Avweb. He couldn't provide any definitive references, but did confirm my statement that if you have been issued an approach clearence in this situation, all IFR traffic conflicts have been resolved. Essentially his position is he doesn't know if descending to the MEA is legal, but it won't cause any problems for him. I've copied his response below.


>>>>>>Just so you know, I'm running this on 2 ATC boards as well, and they are right with us, stumpted.

you wouldn't happen to have links for these boards would you?


regards



Don Brown responds:

The short answer is I don't really know. In my mind, you're actually asking a "pilot" question instead of an "ATC" question. After a controller clears you for this type of an approach, terrain becomes your problem (and your decision.)

One thing I do want to make sure you're aware of (I think you already are) is that a controller shouldn't give you an approach clearance without either an altitude to maintain until established on a published section of the approach or...making sure that you are already established on a published section. You are correct that all traffic conflictions should be resolved prior to the issuance of the approach clearance. Therefore, I don't see an operational problem from a controller standpoiint. Unless it sets off the low altitude alert. But that would be a local computer adaptation. The big worry of course is staying out of the rocks.

There should be someone in the FAA that could answer your question. The legal part should be covered in the FARs. The technical part should be in the TERPs manual. Figuring it out will be the fun part. <G>

Thanks for reading.

Don Brown

 

[stillaboo]

I concede defeat

I recently wrote the editors of IFR Magazine (if you've read it, you know ATC/FAR questions are their specialty). Their reply:

We say yes. "Cleared approach" allows you down to all the mins. ATC should not have anyone below.
--Paul Berge
IFR

---
So, from an ATC perspective it is VERY clear that nobody is below you (if an ATL safety rep and IFR Magazine editiors say so, it is so). If you descend down to the MEA/MOCA, then you'll have IFR separation all the way through the en route descent, the approach, and the missed.

While I'd like to see the reg that makes it legal for a pilot to descend w/o a specific ATC altitude change (or, if not that, the one for ATC to clear the area before authorizing the approach) . . . . it looks like the descent to MEA after the approach clearance is ok.

I'm warming up my piece of humble pie in the 1st class galley oven right now.

-Boo!

 

[A Squared]

Re: I concede defeat

I don't know if I'd concede defeat if I were you Stillaboo. I think the question of legality still stands.

I think that we can agree that there's no danger of running into another airplane, but we're still missing that regulatory blessing.


91.179(a) requires us to maintain the altitude assigned by ATC. Using the AIM, we can show pretty clearly that cleared for the approach allows us to descend to any altitude published on an IAP or published feeder route ...... however, it is still unclear that the approach clearence allows us to descend from the last cleared altitude while enroute.

Look at it a different way, suppose that you got a Letter of investigation alleging a violation of 91.179(a) for doing this. What are you going to point to to defend your actions. While I agree with Don Brown and the IFR editors, that it *should* be allowed, and it's not unsafe, nither of those sources would carry much weight in an FAA enforcement.



>>>>>>I'm warming up my piece of humble pie in the 1st class galley oven right now.


I started munching my humble pie a few days ago when I had to admit I couldn't back up my stance with a reference.

regards

 

[172driver]

Interesting thread. I have another question along the same lines. We've had many debates on this one.

91.177(i) states that once established on a segment of a published route or instrument approach procedure, published altitudes apply to descent within each succeeding route or segment unless a different altitude is assigned by ATC.

Usually, minimum altitudes are published for each segment. Once established, can the pilot stay high or must he descend to the published altitude? Common examples are...maintain 3000 until established, cleared for the approach.
1. Published alt on a DME arc is 2000'. Obviously, no hurry to descend if you don't have to. But do you?
2. GS intercept alt is 2500'. Intercept at 3000 or descend to 2500 and intercept?

Some say that the published altitude is a minimum altitude and that you are complying with it as long as you are above it...even if thousands of ft above.

Others, including our DPE, say that because the reg reads, "published altitudes apply to descent," you must come down to the published altitude.

 

[Singlecoil]

Well, I'll chime in on that one. They are minimum altitudes. You don't have to descend to them immediately, it is entirely at your discretion. There are plenty of times when you don't want to go down there, like descending into a low cloud layer that has ice in it. It is absolutely OK not to descend into that.

Also, in cold weather ops in mountainous areas you are going to want to stay high on things like DME arcs or non-precision approaches because your altimeter will be lying to you. You can add the appropriate correction to published altitudes and fly that. On the approach, you don't have to advise ATC you are doing that, but you do if you would like a fudge factor on an airway, obviously. Something else to think about, minimum vectoring altitudes are down to 1000 agl even in mountainous areas. On a -30 day, you could only be 400 agl even though you and ATC think you are 1000 agl.

 

[stillaboo]

As the unofficial 'reg' guy of this post, I'll chime in one last time. I'm with Singlecoil here. "Published altitudes apply to descent" means just that, the published altitude applies to descents. To go any lower than the minimum altitude would require a descent. But you aren't allowed to. Simple. I'd say your DPE, '172driver' is, how do we say this delicately . . . WRONG! I'd advise that you (rather than one of your students) take him up on this.

Singlecoil points out some benefits of remaining high. Here's another. The safest approach is a stablized approach, one which doesn't consist of descent, level-off, descent, like an ILS. On many ILS's, the GS intercept is 500-800 ft. below the intermediate approach altitude. "The glideslope is normally useable to the distance of 10 NM. However, at some locations, the glideslope has been certified for an extended service volume which exceeds 10 NM." (AIM 1-1-9d3) Interestingly, there appears to be no height restrictions mentioned, though there are for localizers (any comments on the lack of GS height restriction, other than the false GS's above the real one?). So, my point is, if you remain at the intermediate altitude (coming off the arc or PT), you are only required to make one descent configuration at GS intercept (even if it's outside the OM/FAF), rather than multiple ones, provided you're within 10 NM of the antenna (which is at most 1250 ft from the approach end of the runway (is the end the threshold, or what?). This method is usually safer than the 'dive and drive' method, and is the reason that VDP's exist for the big tin with VNAV vertical path computers, so that they make 1 descent to the runway from the FAF, rather than diving down to a low altitude with a high rate of sink in IMC only to level off at MDA(H) on non-percision approaches (What most pilots call VDP's are actually not, as a VDP is the DA(H) on a non-percision approach for VNAV equiped aircraft. See the note on Jepp plate for details)

So, fly higher and make less configuation changes (aka, fly safer) and intercept the GS at the intermediate altitude. It's easier too! I did it on my instrument and multi-instrument commercial rides and passed both. Just explain to the examiner why you're not descending.

Now, the issue of MVA's. MVAC (MVA charts, the ones controllers use to vector pilots) are supposed to provide 1000 ft and 3 miles in Part 95 non-mountainious areas and 2000/3 in DMA (FAR 95 designated moutainious areas). These can be reduced down to as low as 1000/3 to help controllers radar vector smoothly onto approaches. It has been found that many tracons have simply bypassed TERPS regulations in constructing their MVAC's (ATL Center reduced the required 2000 ft clearance in ther DMA's to 1500 w/o approval from anyone, and is now under an NTSB investigation for it) to make their lives easier, putting pilots at risk. One example, ILS 16 in Ashville, NC, shows an inital approach segment that the FAA says requires a minimum altitude of 6800 ft. for proper FAR 91.177 obstacle clearance. The MVA for this same area, which is in a DMA and has a 4,858 ft mountain in it, not to mention the additional height of any trees . . . 5,300 ft.! In short, if you are about 1 mile east of the depicted course and are maintaining your altitude EXACTLY, you're less than 450' above the ground, and likely less than 350' above the trees in an area where you are required to have 2000' ft b/t you and terra firma. And I didn't even mention the 5339 ft. mountain that's about 3 miles east of you (and 39 ft. above you!). And that's if it's not a colder than standard day. Hope you have radar altimeters, boys.
MVA's are not held to the same standards as instrument approaches are in reality, though they are legally. If you're flying into Ashville under vectors, you just busted FAR 91.177a2, while your controller just violated the ATC Handbook (7110.65). Neither of you knew it, but that's cold comfort when the FAA comes calling.
[Note: all info about MVA's was blatently plagerized from the April 2003 IFR Mag. article by Wally Roberts, former chairman of ALPA's TERPS Committee]

A Squared - you're right. After further review, my pie is still uneaten. I don't think we'll ever have an answer on the descent w/o authorization issue. I'm always asking for a descent clearance from ATC (not to MVA though!) and putting my pie in the freezer so it doesn't get stale.

-Boo!