Straight-in approach

[jeya]

Can You help me define me what is really straight-in in ICAO rules? In 8168 I ve found only that non-circling are straight-in. Any changes to minima or procudures for ILS straight in?

[Rainboe]

Note your airline procedures for confirming glideslope altitude at a point before commencing descent relying on glideslope alone. A suitable fix off a VOR radial, an NDB fix or a valid INS position usually is enough. Note MSA, but apart from that, no special restrictions.

[SNS3Guppy]

In the US, a straight-in procedure is one aligned within 30 degrees of the runway, and beyond that only circling minimums are published. I believe ICAO follows the same guideline. (ICAO states not more than 30 degrees between runway centerline and final approach course alignment for category A and B aircraft, and I believe 15 degrees for all other aircraft, with not less than 900 meters between the point of intersection of the approach track and runway centerline). Lack of straight in minimums doesn't preclude a landing straight in if one is able to see the runway in time to maneuver normally and align one's self with the runway (depending on specific procedure restrictions).

The term straight-in approach is also used in conjunction with procedures not requiring course reversal such as a procedure turn.

[punkalouver]

In the US, a straight-in procedure is one aligned within 30 degrees of the runway, and beyond that only circling minimums are published.

It actually is possible to have circling only minimums when the approach is within 30° of the runway, if the descent angle between the FAF and the runway is more than 400' per nautical mile, there are only circling minimums, although you are allowed to continue for a straight in landing if all requirements are met.

http://www.terps.com/ifrr/nov97.pdf

[SEV]

last radar vector from ATC to intercept the FAF/P and continue the approach normally.
Thank´s.

[Henry VIII]

As far as I remember circle to land procedure is mandatory when final approach segment track differs more than 30° from QFU (rwy track).
When within 30° whe have the opportunity to proceed straight in or circling according to wind direction and intensity.

[Port Strobe]

Slight thread creep here but one of the diagrams in the pdf document linked from post 4 rasied a question.
If you look at page 4 figure 6 of the pdf, the scenario is conducting an IAP for rwy 36 with the intention to circle to land on rwy 29. The circling minima can be obtained from the plate for whatever IAP you're executing for rwy 36, fair enough. However say there's an IAP for rwy 29 (the aid could be u/s hence why you're circling, in theory) and the circling minima attached to that IAP are higher, do you still use the rwy 36 minima or the higher rwy 29 minima? Does a higher MDA suggest another obstacle not considered for rwy 36 or do circling minima for any IAP consider the same area regardless of which runway you're intending to land on? If that's the case then why have different minima? Does the approach aid have a bearing on this?

An example of this I found here for Cat A aircraft;

http://www.nats-uk.ead-it.com/aip/current/ad/EGPK/EG_AD_2_EGPK_8-7_en.pdf
http://www.nats-uk.ead-it.com/aip/current/ad/EGPK/EG_AD_2_EGPK_8-6_en.pdf

Granted it's only 20' but I don't understand why there is a difference, any thoughts?

[Dan Winterland]

Forget the US. The question was with regards to DOC8168 which relates to PANSOPS. The US uses TERPS which are different in most aspects.

[SNS3Guppy]

PANS OPS still uses 30 degrees of runway alignment (and other criteria spelled out in my previous post) to determine if the procedure qualifies as straight-in, as well as particular obstacle clearance plane considerations.

However say there's an IAP for rwy 29 (the aid could be u/s hence why you're circling, in theory) and the circling minima attached to that IAP are higher, do you still use the rwy 36 minima or the higher rwy 29 minima? Does a higher MDA suggest another obstacle not considered for rwy 36 or do circling minima for any IAP consider the same area regardless of which runway you're intending to land on?


If you're flying an approach to runway 29, then you use the minimum criteria for runway 29, regardless of the runway to which you're circling. If restrictions exist for circling to a different runway, they'll be spelled out in the procedure you're flying. You do not need to look to the procedure for another runway, to determine your course of action for the procedure you're flying now.

If you're flying an approach to runway 36, use the runway 36 minimums. If you're going to be circling to runway 29, you need to stay within the obstacle protection area developed for the particular approach categoryin the circling minimums applicable to the published procedure for runway 36. You do not need to look up the procedure for runway 29 and attempt to superimpose the minimums published for that procedure...because you're not flying it.

The minimums for the runway to which you're circling may be higher...but these aren't runway minimums, they're approach minimums. You're not flying the approach to runway 29...you're flying the approach to runway 36. Therefore, the only minimums with which you need concern yourself are those to runway 36. If you were flying the approach to 29, then you could worry about the minimums applicable to that procedure...but you're not.

If there are issues with obstacle protection, this will be spelled out in the procedure notes (eg, no circling west, etc...the procedure will spell out any particular terms or conditions by which you must abide).

[Port Strobe]

If you're flying an approach to runway 29, then you use the minimum criteria for runway 29, regardless of the runway to which you're circling.

Understood thanks :ok:

The minimums for the runway to which you're circling may be higher...but these aren't runway minimums, they're approach minimums.

Any ideas why they're different? I was under the impression the circling area considered would be the same no matter what IAP you execute to get to it, hence all the obstacles are common no?

[SNS3Guppy]

Any ideas why they're different? I was under the impression the circling area considered would be the same no matter what IAP you execute to get to it, hence all the obstacles are common no?


The obstacles which affect the approach minimums aren't just what's around the airport in the protected circling area...you've got to consider the approach path. Minimums are determined based on obstacle clearance criteria, as well as what's called an "obstacle clearance plane," or an imaginary surface or plane through which no obstacles can penetrate. If obstacles do penetrate this plane, then it's angle must be raised, or floors raised for a particular segment of the procedure. The reasons for the slightly higher minimums may have nothing to do with actually circling...because you'll reach the MDA for that procedure well before you actually start circling. It may have to do with obstacles farther out between the last step-down fix or FAF and the missed approach point...which don't affect the other procedure. It's very possible to having circling approaches to a runway complex with different approach minimums...because obstacle protection while actually circling is only part of the picture.

Think of it this way: by the time you get to the circling part of the approach, you've already flown the procedure...and the minimums apply to the procedure itself...The minimums are established where they are for a good reason. We may not know what it is, and it may have nothing to do with the circling areas...but may well have to do with obstacles, airspace, or other considerations that were a factor during the final approach.

[bookworm]

An example of this I found here for Cat A aircraft;

http://www.nats-uk.ead-it.com/aip/cu...GPK_8-7_en.pdf
http://www.nats-uk.ead-it.com/aip/cu...GPK_8-6_en.pdf

Granted it's only 20' but I don't understand why there is a difference, any thoughts?

For the NDB21 there's an obstacle of 570 amsl about 1.8 miles from the threshold just to the left of track. This, with 250 ft minimum obstacle clearance, dictates the OCA of 820 amsl for all approach speed categories.

For the ILS31 VM(C) minima, for different cats, different radii of turn are used to determine the area in which obstacles are relevant. For Cat A, the area does not include the 570 amsl obstacle, and so the VM(C) MDA can be 800 amsl. For cat B, the obstacle is within the area considered, and the MDA has to be 300 ft above the obstacle, presumably rounded to 900 amsl. For Cats C and D, it looks like the further 671 amsl obstacle is relevant, and with 400 ft obstacle clearance, the VM(C) MDA becomes 1100 amsl.

[Port Strobe]

Thanks guys, very helpful of you :ok: