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View Full Version : ILS that only goes down to 400AGL


Wingbreaker
06-12-2017, 02:23 PM
Question from some hangar talk with a friend earlier. They maintain that there are ILS approaches "out west" that only bring you down to 400ft. agl instead of the standard. Also that there is not a category tied to these ILS's.
Now this doesn't sound too unusual, but i've never come across anything like this. Are there full ILS approaches that don't bring you down to at least 200?
Thanks in advance for the enlightenment.


Ohlsan
06-12-2017, 02:55 PM
Yes there are, KBOI 28r ILS brings you down to 250 AGL

USMCFLYR
06-12-2017, 03:02 PM
Question from some hangar talk with a friend earlier. They maintain that there are ILS approaches "out west" that only bring you down to 400ft. agl instead of the standard. Also that there is not a category tied to these ILS's.
Now this doesn't sound too unusual, but i've never come across anything like this. Are there full ILS approaches that don't bring you down to at least 200?
Thanks in advance for the enlightenment.
Yes.

There are many reasons why an ILS may have higher than standard
minimums to include an obstacle or signal irregularities. If you can give me the airport or ILS identifier I'll see what I can find out for you.


deadstick35
06-12-2017, 03:15 PM
Yes there are, KBOI 28r ILS brings you down to 250 AGL

And I bet most have at least 3/4 mile vis requirement too.

TonyC
06-12-2017, 03:21 PM
Question from some hangar talk with a friend earlier. They maintain that there are ILS approaches "out west" that only bring you down to 400ft. agl instead of the standard. Also that there is not a category tied to these ILS's.
Now this doesn't sound too unusual, but i've never come across anything like this. Are there full ILS approaches that don't bring you down to at least 200?
Thanks in advance for the enlightenment.




Not exactly "out west", but KBOS ILS RWY 27 has a CAT I Decision Altitude of 460', which is 443' above the TDZE of 17'.






.

point432
06-12-2017, 03:42 PM
KYIP...250, 3/4?


Sent from my iPhone using Tapatalk

JamesNoBrakes
06-12-2017, 04:36 PM
Yes.

There are many reasons why an ILS may have higher than standard
minimums to include an obstacle or signal irregularities. If you can give me the airport or ILS identifier I'll see what I can find out for you.

Yes, this.

There even used to be LDA+glideslope approaches. All the hardware of an ILS, but you just couldn't call it an ILS. I think those are all gone now. The old definition of "a precision approach is one with vertical guidance" was obsolete decades ago, the FAA just never got around to fixing that until recently.

Tweetdrvr
06-12-2017, 05:47 PM
LDA/GS at AMA

http://155.178.201.160/d-tpp/1706/00019LDAD22.PDF

LOC transmitter offset to side of runway, due to its location doesn't meet criteria to be an ILS

Wingbreaker
06-12-2017, 07:14 PM
I thought there may be a few. Show's what I know!
Thanks for the replies everyone.

C130driver
06-12-2017, 07:36 PM
It's usually due to obstacles that penetrate the standard protections of the 200-1/2 transition to visual segment. Not sure exactly what it is but TERPS/FAA has a specific criteria for obstacle protection on various segments of an approach. Similarly, instead of or including higher HATT you'll see a steeper glidepath.

On a similar note, if you ever see a non precision approach without a VDP published, it means there are obstacles protruding the protection area for a normal 3* glidepath, meaning depart the MDA at your own risk at night or IMC even with the runway clearly in sight.

USMCFLYR
06-13-2017, 03:02 AM
It's usually due to obstacles that penetrate the standard protections of the 200-1/2 transition to visual segment. Not sure exactly what it is but TERPS/FAA has a specific criteria for obstacle protection on various segments of an approach. Similarly, instead of or including higher HATT you'll see a steeper glidepath.

On a similar note, if you ever see a non precision approach without a VDP published, it means there are obstacles protruding the protection area for a normal 3* glidepath, meaning depart the MDA at your own risk at night or IMC even with the runway clearly in sight.
Do you mean VDA instead of VDP?

rickair7777
06-13-2017, 03:57 AM
200' and 1/2 are the lowest authorized mins for generic cat I, but that doesn't mean they all have to go that low.

C130driver
06-13-2017, 08:37 AM
Do you mean VDA instead of VDP?

Nope, VDP (visual decent point,) often published on a non precision approach indicating the point from which you should start your decent from MDA to assume a normal glidepath to the runway. Lack of a VDP means that there are obstacles in the protected zone of that glide path. It's a lawyerism for sure.

joepilot
06-13-2017, 09:38 AM
ILS 16R at KRNO has DH of 2,000' and min visibility of 7 miles.

Joe

C130driver
06-13-2017, 01:40 PM
ILS 16R at KRNO has DH of 2,000' and min visibility of 7 miles.

Joe

And for good reason, the airport sits in a bowl surrounded by 10k peaks...makes for interesting weather in the winter...but some of the best skiing in the world :)

EMAW
06-13-2017, 07:54 PM
ILS 26 Rifle, CO. used to require 7 miles. Now it's 4 sm vis and 1263 AGL. Fairly common in mountainous areas.

JamesNoBrakes
06-13-2017, 08:29 PM
Sat-based and AR approaches are making many of these a thing of the past. There are still plenty, like the examples given, but technology is starting to be leveraged. It started with those LPV approaches years ago to 250 and 200' minimums. Even at 300 feet you suddenly had capability at airports that had either nothing or crazy high mins. At some point RNAV RNP approaches using curving paths will be available to more aircraft and systems.

deadstick35
06-14-2017, 06:30 AM
I seem to recall once a TREE grew too tall between surveys and made it necessary to issue an FDC NOTAM for new mins of 275' / 3/4.This tree was in the missed approach segment.

grnclvrs
06-14-2017, 09:09 AM
Last year sometime, the LOC to one of the runways in CKB got you lower than the ILS to the same runway.

CaptSwift
06-14-2017, 09:31 PM
ILS 16R at KRNO has DH of 2,000' and min visibility of 7 miles.



Joe



They changed the approaches last year now they are 200 and 1/2... you do need a 390'/nm climb to 8k, however.

TonyC
06-15-2017, 09:18 AM
ILS 16R at KRNO has DH of 2,000' and min visibility of 7 miles.

Joe




Do we need a mini-clinic on DA, DH, and HAT?






.

USMCFLYR
06-15-2017, 10:12 AM
Nope, VDP (visual decent point,) often published on a non precision approach indicating the point from which you should start your decent from MDA to assume a normal glidepath to the runway. Lack of a VDP means that there are obstacles in the protected zone of that glide path. It's a lawyerism for sure.
Just to be sure that everyone else reading this thread gets the difference too:

VDP (from the 8260.3G TERPS)


253. VISUAL DESCENT POINT (VDP). The VDP
defines a point on an NPA procedure from which
normal descent from the MDA may be commenced
provided the required visual references have been
acquired.
ESTABLISH A VDP FOR ALLSTRAIGHT-IN NPA PROCEDURES (to include those combined with a PA/APV procedure), with the
following exceptions/limitations:

�� Do not publish a VDP when the primary
altimeter setting comes from a remote
source.

�� Do not publish a VDP located prior to a
stepdown fix.

�� If the VDP is between the MAP and the
runway, do not publish a VDP.

�� Do not publish a VDP when the 20:1 surface
is penetrated (Vol. 1, chapter 3, paragraph
3.3.2d).

�� When feasible, the VDP should be ≥ 1NM
from any other final segment fix (e.g., MAP,
stepdown). When not feasible, the VDP
must be at least 0.5 NM from any other final
segment fix. If < 0.5 NM and the other fix
cannot be relocated, do not publish a VDP.
DO NOT increase the MDA to achieve the
≥ 0.5 NM distance.

Also - limitations:
3.3.2 c. (2) (b) 20:1 OIS. If penetrated, take the following action:

Lighted Obstacles: Do not publish a VDP and limit visibility to no lower than 5000 RVR or 1 SM.

Unlighted Obstacles: Do not publish a VDP, limit visibility to no lower than
5000 RVR or 1 SM, and annotate the chart denying the approach or applicable
minimums at night.
VDA (from the same reference)


252. VERTICAL DESCENT ANGLE. Vertical
descent angle (VDA) is normally used in this segment
for non-precision procedures. Determine the VDA for
all NPA procedures except those published in
conjunction with vertically-guided minima or no-FAF
procedures w/out stepdown fix(es). See applicable
chapters/directives for guidance on no-FAF or
procedures published with PA and APV minima.
Optimum VDA is 3.00 degrees. Where operationally
feasible, design straight-in NPA procedures (all CATs)
to achieve a VDA equal to the commissioned angle of
an installed visual glideslope indicator (VGSI) if within
the standard VDA range. When a VGSI is not
installed or not within the standard range, or final is
circling aligned, design procedures at the optimum
VDA when possible or within the following range:
STANDARD VERTICAL DESCENT ANGLES
FAA 2.75-3.77 (IAPS w/ ≤ CAT C mins)
2.75-3.50 (IAPS w/ CAT D/E mins)
USAF 2.50-3.50 (All IAPS)
USN 2.50-3.77 (All IAPS)

Note 1: Minimum VDA N/A to circling only
procedures.

Realize that these VDA are mathematical calculations and do not necessarily provide obstacle clearances in the visual segment of the approach.

From the 8260.19G
(a) Do not publish a VDA/TCH when Flight Inspection has requested that one not be established due to an obstacle that would require an aircraft to deviate from its vertical flight path prior to reaching the TCH.
(b) When the condition in paragraph 8-6-8.s(1)(a) has occurred, a chart note must be placed in the profile view of the chart to alert the pilot that should an avionics manufacturer provide an advisory vertical angle in the database, the path below the MDA to the runway is not clear of obstacles; use "Chart profile note: Visual Segment Obstacles."
Note that the VDA will still be coded into the database, but the requirement (which it always was) to avoid obstacles is the pilot's responsibility.

CrimsonEclipse
06-17-2017, 12:08 PM
The most common reason for higher minimums is an obstacle or obstacles in the protected areas calculated by the FAR 77 (i think)

It's been a while.

Cut down a few trees, level a mountain, eliminate magnetic anomalies, and you're right back to 200 and 1/2 SM

BizJet
06-27-2017, 07:24 PM
CLT RWY 23 ILS has mins at 350' AGL. I think it has something to do with railroad tracks and interstate on short final.

Triggs
07-07-2017, 04:07 PM
KLEB in NH has a DH of 350'



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