100 Above TDZE Prior to MAP on LOC/DME???

[Xav8tor]

I know you’re just being facetious, but that’s one of the things that drove me nuts on the news reports after this, and similar accidents. I don’t think that an NP approach is inherently more dangerous, or difficult, than an ILS. FLOWN PROPERLY, as far as I’m concerned, one approach is a good as the other, the only difference being the probability of a miss. Other than island flying, my absolute favorite is handflying approaches, even NDB’s, down to mins.

Do a Google on 5966 and approach. You’ll see all sorts of statements inferring that the reason the plane went down was because IRK doesn’t have an ILS. And guess what? The town had been trying for months, maybe years, to get funding for a GS approved. Shortly after the crash, they got the approval.

Plenty of people would be satisfied with that as the probable cause and the proper remedial action too.

 

[Xav8tor]

For those who requested to see the interviews “in context” which I took to mean the whole report, converted from a pdf to txt, it is over 100,000 characters and this board has a 10,000 character limit per post. I don’t think the mods or most readers would appreciate that. The excerpts I posted were not cut/pasted with any alteration to advance a position in mind. I just posted the parts from those interviews that illustrated the issue. I did delete names.

If someone knows of a way to post attachments here, or can provide a public free host, I’ll upload the entire docket. It needs to be a server that doesn’t require registration for people to view and download the documents. The entire set of reports is 34 mb. Group Factuals are very different from the final reports most pilots are familiar with and contain more info than “accident reports” and would help those who really are interested in the nuts and bolts of how theories of causation/contributing factors are derived.

I won’t get around to posting my research summary on 91.175/VDP/Obstacles, etc. tonight, I’m tired and getting a little burnt out on this thread (as many are). However in reviewing the posts and integrating what I learned, I did see a nice AIM quote Clutch already posted that was mentioned by one expert I spoke with. It at least infers (to me it is pretty darn clear) that, if you want to play it safe, and you are deciding if it is OK to leave MDA yet, the absence of a VDP on the chart should be a heads up that premature descent from MDA is ill-advised due to (among other things) a potential obstacle danger (e.g., tall trees growing on rolling terrain):

“Approaches without VDPs have not been assessed for terrain clearance below the MDA, and may not provide a clear vertical path to the runway at the normally expected descent angle. Therefore, pilots must be especially vigilant when descending below the MDA at locations without VDPs.” (AIM 5-4-5)


More later.

 

[Xav8tor]

This issue apparently has burnt out here, and things are hitting the fan for me, so I don't know if I'll ever get around to writing what amounts to an accident analysis or factual brief, but here is a brief summary of what I learned and have concluded for myself. Your mileage may vary.

First as to whether a pilot considering when it is safe to leave MDA under IMC at a distance greater than where the VGSI intersects MDA, the obvious answer should be "don't do it" even if you do see other 91.175 visual clues (except of course the VASI/PAPI). Unless you are on a VGSI or at/above MDA, you are on your own for obstacle avoidance.

Assuming you are a pilot who knows that other things like no DME preclude publishing a VDP, and IMHO even if you don't, if you are for any reason thinking about leaving MDA on the basis of the ALS without more (i.e., until you are on the VASI) solely based upon 91.175 as written, again, don't do it, but if you do bother considering the lack of a published VDP when deciding, it is very reasonable to assume that an obstacle is a real possibility/reason for no "V" and you may hit it. In addition to the AIM cite above, elsewhere in the same section is the following:

f. Visual Portion of the Final Segment. Instrument procedures designers perform a visual area obstruction evaluation off the approach end of each runway authorized for instrument landing, straight-in, or circling. Restrictions to instrument operations are imposed if penetrations of the obstruction clearance surfaces exist. These restrictions vary based on the severity of the penetrations, and may include increasing required visibility, denying VDP's and prohibiting night instrument operations to the runway.


8260.19C CHG 3 7/14/03 Flight Procedures and
Airspace

SECTION 3. VISUAL DESCENT POINT (VDP)
430. ESTABLISHMENT. The VDP defines a
point on a straight-in nonprecision approach where a
normal descent from the MDA would commence if
the required visual references were acquired.

a. Establish a VDP provided the SIAP meets
the requirements of TERPS Volume 1, paragraphs
251, 252, and 253.

b. For chart clarity, a VDP should be no less
than (1 mile OPTIMUM) (0.5 miles MINIMUM)
from a final segment fix or MAP. If proximity closer
than 0.5 miles is required, consider one of the
following actions:
(1) Do NOT establish a VDP.
(2) Relocate the fix to the VDP location,
and do NOT establish a VDP.
(3) Relocate the fix to accommodate the 0.5
mile (or greater) requirement.
NOTE: Option (2) above increases MDA and
descent angle. Option (3) increases S/D
altitude.

c. Do NOT adjust visibility minimums to
accommodate a VDP.
d. Where used, the DME source must be the
same as the DME source for DME fixes in the final
segment.

431. FAA FORM 8260-9 ENTRIES. To facilitate
review, entries may be required in the REMARKS
section. Where a VDP is not established, give the
reason; e.g., obstacles penetrate VDP surface,
descent gradient, proximity to final approach
segment (FAS) fix, etc. (see paragraphs 857q and
860c).
432-439. RESERVED.

Now here is where it again gets complicated. In the 5966 example, were they in the visual segment at the relevant point/time? Well, that takes some math, a lot of TERPS steps, and graphing/charting, etc. and I don't have the time to do it. Also it is irrelevant. The point I wanted to suggest is that if you don't see a VDP charted and there is DME and a VASI (which you don't yet see), etc., the, or at least, a, safe assumption is that there is an obstacle out there. It is another reason to stay put at MDA regardless of what 91.175 says is "legal." The folks I spoke to agreed. Is it the only possibility? No...it might be that that approach simply hasn't been evaluated for a VDP yet, but I wouldn't bet my life on it.

That about sums it up for what one might consider if you don't see a 'V" and aren't doing a constant rate descent (another topic for another time). Since I did quote an “unverified” web source the first time I said it this and it was too broad a statement, I’ll take some “crow” on my salad. I still say it is a safety conscious way to think in the cockpit, and if I ever get in one again, I’ll try to remember it.

Next, the missing +/-1059 trees about between where they left MDA and the threshold. This was not their exact point of impact, which was a little further out, but that isn't my point. I stand on my opinion that if you insist you are going to leave MDA for 100 above TDZE on the basis of seeing the ALS alone because you think 91.175 says OK, and an obstacle is between you and the runway within 5 feet of your intended altitude, and close to the LOC course centerline, you're asking for trouble. But in fairness to Jepp users, you can't consider it if it isn't on the chart. No one I spoke with disagreed with that.

Should there be a change or clarification to 91.175? Forget my opinion, your opinion, or the "number" of people who think the ALS alone means you are good to go from MDA to 100 TDZE. Some do and within that group there are those that either don't consider distance from the threshold at all, or are uncertain about where the "safe" point is.

My research and calls to various people “in the loop/know” confirmed that it is already "under consideration" at various levels. There is evidence that the example operator is/was not the only one that permitted the procedure/profile in question. Whether the reg gets changed or the topic gets any other consideration is anyone's guess. Most of the time, the number of lives lost and amount of media attention seems to control whether a reg is changed/made in response to an air crash. That is just an opinion, but I did write a long paper for a legislation class on the subject and that is what my impression was 7 years ago.

Even though the FAA dual mandate has since then been eliminated (something I called for in that paper and still only got a B), the rulemaking process continues to have as much to do with money, perhaps more so, as it does safety. As a matter of fact, that too is the law. Oh yeah, toss in “politics.” I don't know if a single person can make a difference, but I do know that one is already trying to get 91.175 changed and it isn't me. He beat me to the punch by months. Personally, I wish him luck and hope that the NTSB makes an official recommendation to help push it through.

Thanks again for everyone's input. Business is bad and the horizon is obscured at best. If things get any worse, come see me at Home Depot. It sure doesn’t look like it’s going to be in aviation ever again.

Xav8tor

 

[TonyC]

Xav8tor,


Thanks for your calm, reasoned post. As I said in my very first post on this thread, I apprecaiate your zeal. You've certainly devoted a lot of time, energy, and thought to this subject, and it has been a healthy exercise for all. I'm sure we've all learned something here.

My caution against reading too much into a single statement or even a conversation taken out of context stands, but I think you understand that. A stark example of that caution can be seen when contrasting the title of this thread with the thoughtful discussion of VDP construction offered in your last post. If I were to put too much weight on the title alone, I might think you're of the opinion that one must remain at the MDA until the MAP. Given that the vast majority (at least in my limited experience) of MAPs are located at the end of the runway, and remaining at the MDA until then would make it impossible to land in the touchdown zone using normal maneuvers and normal rates of descent, such a practice would render non-precision approaches useless to me. The discussion in your last post makes it clear that this is by no means how you interpret the situation. Similarly, each voice should be given the same fair hearing.

Thank you for posts - - as I said, I think we've all learned a bit. I'm sure there are many who've read but not spoken that have learned more than we can know. And that's what it's all about, anyway - - learning.





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[Xav8tor]

Tony,

Thanks for the kind words, I can use them. Just got word for sure (saw it coming for a week or two) that I lost out on a position I’ve been chasing for over two years: perfect locale, great people, decent salary & benefits, stability, and getting to do a little bit of everything I’m good at. They had me thinking I was a shoe in. Maybe that’s why I’ve been a little “intolerant.”

Funny you should mention the thread title as a problem. I’ve been thinking about finally writing a book or TV/screenplay about some of my experiences, focusing on CVR’s and the “dark side” of air crash investigation. I chose the title first, before even doing an outline. I was chatting with someone who has been pretty successful at it and he said I broke a cardinal rule: NEVER write the title before you write the book. I knew that from writing papers in school, research, and briefs too, but it applies here too I guess.

If anyone ever has a question about CVR’s, ATC tapes, cockpit communications, language issues, etc., please start a thread, I’d love to participate. If any of you ever need professional advice in the area, I’ll give pilots a professional discount! I’ve done a bunch of them, including some of the big ones in the last ten years, so let me know.

Keep the blue side up (unless you are fortunate enough to do aerobatics) and keep your eyes open for changes/recommended procedures on non-precision approaches. It’s still early to say whether some of what was discussed would have changed things on 5966, but modern theory is, if only one relevant factor had been different, removed, defended against, etc., then the accident would not have occurred. If our discussion, even the “ranting,” makes one pilot think twice someday about ducking down a little low/too soon to get in, then it was all worth it.

Thanks again to all for the stimulating discussion and chance to talk shop.

X

PS - Wishing I could drop that “x”. This discussion helped make me miss the airline biz and the cockpit more than ever. If you’re still in the game, one last piece of advice/opinion: no matter how bad it gets (to a point of course), a crappy day on the line, or just about any position in aviation aside from lav service, is better than a great day at most other places you could be.