Non-Precision Approach Profile (ICAO)

[Vertolot]

Hi,

On the Jeppesen approach plates you can se for an non-precision approach altitides given at a specific distance, with a continuos descent profile on the chart (no step down). Are these altitudes absolute minima descent altitudes at this specific DME (for obtaining required obstacle clearance) or only altitudes for depicting the correct approach angle? In the Jeppesen it says "Minimum altitudes unless otherwise specified".

My other question is about timing in a holding. In the Oxford aviation Training Air Law book it says, "The still air time for flying the outbound entry heading should not exceed one minute if at or below 14 000 ft" I used to adjust the outbound leg so I got a 1 minute inbound leg, what is the correct procedure?

Thanks in advance,

Vertolot

[Non-PC Plod]

I do not consider myself an expert, so I stand ready to be corrected, but I think if there is no step-down fix specified, you can descend at any angle to your MDA. The heights and distances are simply an illustration of a notional glidepath.
For flying the hold, you are correct that you adjust the outbound leg for wind, so you can achieve a 4 minute hold. That is why it specifies "still air" times. Obviously, if there is no wind, there is no adjustment to make.

[Mark Six]

Vertolot, in Australia, (and presumably most other countries), you fly a 1 minute outbound leg (adjusted for wind), however I did some flying in the US recently and was told to adjust my outbound timing in order to achieve a 1 minute inbound leg. I assume this variation is peculiar to the US but stand to be corrected.

[gribbs]

Step-down fixes, as they're called, are mandatory on a non-precision approach. They're put there because of an obstacle in the final approach segment, which is why you don't see them on all approaches, only those where a specific obstacle is an issue. In the UK they always used to be underlined, ie NOT BELOW, but of late the AIS charts are produced to a different standard and you might well see them not underlined. There's also potential for confusion since the AIP sometimes now shows only the absolute minimum altitude (shown as a grey shaded rectangle under the approach segment in question) and not the altitude at the step, in which case you're supposed to follow the advisory altitudes shown (ie at 4d you should be at 1200 etc) and you're not allowed below the altitude shown for the shaded box.

Note also that there's nothing wrong with being higher than the step, and by that I mean more than 100ft above it; the important thing is that you're not below it; there are still some examiners out there who think that you have to be within 100ft of a step. Also, the concept of 'dive and drive', ie descending to the step altitude immediately after passing the previous fix, is legal but not recommended. In actual fact there's a 15% slope under fixes to consider but that's the realm of procedure design and since no aircraft is likely to descend at more than a 15% angle it's only important for theorists and procedure designers.

The hold is no longer flown as a 4-minute hold, although it normally works out like that. ICAO (PANS-OPS 8168) says only that the outbound leg must be 1 still air minute, ie adjusted for wind. The CAA examine a hold such that the outbound leg is correctly adjusted and that the inbound track is established for 'a reasonable time', normally a minimum of about 15 seconds. You shouldn't fail a hold if your total time is not 4 minutes.

If you want more info on either of these please PM me.