PPRuNe Forums - Max angle to commence an approach (Europe)

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Max angle to commence an approach (Europe)

I have found in PANS-OPS that the maximum angle of the initial approach track to the IF is 90 degrees for a precision approach and 120 degrees for a non precision approach. However I am struggling to find the maximum angle of intercept to the initial approach track which would allow the aircraft to commence an approach which does not feature a reversal procedure and is based on VOR/DME fixes. Is this also 90 degrees? Can anyone shed some light on this? Thank you.

Do you mean what is referred to as a "Dead Reckoning Segment"? This is where the IF would be too distant or at the wrong angle (outside the 90degree or 120 degree angle) and at a greater distance.dead-reckoning segment. In this case you use a DR Fix and the max intercept angle to the localizer from the DR Fix is 45degrees.

A segment of an instrument approach procedure where no track guidance is available between the initial approach segment and the intermediate fix. Where an operational advantage can be obtained, an ILS (instrument landing system) procedure may include a dead-reckoning (DR) segment from a fix to the localizer. The DR track intersects the localizer at 45° and is not more than 10 NM (19 km) in length. The point of interception is the beginning of the intermediate segment and allows for proper glidepath interpretation.http://aviation_dictionary.enacademi...y/f0200-01.gif

Thank you Wasaloadie.

The bit I can't find any information about is the intercept of the initial approach track. Considering your diagram above, VOR (IAF) to the DR segment is, say, a track of 030. If I were to be cleared to the VOR on a track of 180, could I proceed immediately outbound on the procedure or would I need to enter a hold to align myself with the outbound track?

You would fly outbound from the beacon to a fix (Bearing and distance from the beacon). This would be the DR Fix, then turn to intercept the ILS localiser. Max intercept angle of 45degrees and a max distance on 10Nm from the FAF. This is covered in the Air Law Instrument Approaches part of the syllabus. CAE OAA have better, colour diagrams in their notes. (I used to be SME for Air Law there).
If you take a look at the Instrument approach plate for London Heathrow for runway 27, IIRC the "Ockham" is the IF and the track (something like 065) flies outbound to a fix before turning turning northerly to then intercept the ILS.

Quote:

Originally Posted by Needles Crossed (Post 10182626)

8168 mentions we should arrive within +/- 30° of the initial approach track in case of base and procedure turns but does not mention specifically DR legs.

If it was me I'd only continue if I was within +/-30. So if I arrived from Radial 000 (Track 180) I'd enter the hold at the VOR, then continue. But that's rather an opinion.

I'd only continue the approach if arriving via r180-240.

Problem is that some holds aren't even within 30 degrees of the outbound track themselves.. Various examples come to mind: In the EDDB ILS07L procedure for instance, the hold axis (020/200) is 68 degrees off the outbound track (312 degrees). In EDDF ILS 07C, the hold axis is 046/226 whilst the outbound is 177 degrees which is 49 degrees off. They must be working to some different maximum angle for such a procedure design.. any ideas?

Sometimes when a procedure doesn't meet ICAO standards, even if it's just one leg, there is a note, comment box or footnote.
Can't check those approaches you mention.

Quote:

Originally Posted by Needles Crossed (Post 10183613)

yes, you're right you should fly into the 30° of the outbound track (from IAF) so you have 2 possibilities :

- for example, if you're from north as you said, you may ask ATC to deviate from your track by doing a kind of "unpublished DME ARC" variation to intercept the outbound track under a better angle.
difficult to explain like this, but let's say you're on track 180 to VOR. about 10NM before, you may ask to open to the right (track 210) and then close 10° each 10° (radial VOR) . Then , to intercept the 030° Inbound at about 5NM from VOR, then, you'll be in position before flying over the VOR.

- or you just have to enter a hold...as you said. It's longer but ATC will understand.

It's very european actually and complicated. In FAA's world they don't bother. Wherever you come from, they fly to IAF and turn outbound track then. They don't care about the angle , they considere you'll be still inside protection ! simple and efficient isn't ? no need to think more...