step down fix

[winch launch]

Used to know what it is but can t remember.
What is it for?
Is it only on final approach segments?
I am encountering it on a VOR DME appoach plate. It looks like it alters the MDA.

Thanks in advance

Winch

[pilot-320]

The step down fixes are used along approach segments to allow the pilot to descend to lower altitudes over obstacles when not equiped with DME to follow the SDF u have to use the minimum altitude prescribed prior to the fix. Between the FAF and MAP only one SDF is prermitted.

hope that helps.. i was wondering in which approach did u see it? i have only seen it once as im not ir rated yet but asked my instructor about it.

:ok:

[winch launch]

Thanks a lot.

What are the conditions to continue approach to MDA when at the SDF?
Have a the obstacle in sight?

[pilot-320]

To be legal i dont think u are allowed to descend below the SDF. Although when visibility permits u are allowed to descend below MDA . I havent heard the rule about having the obstacle in sight but if it was i wouldnt do it! Maybe im wrong !:ugh:

[winch launch]

I saw that on the Charleroi (EBCI) VOR DME Rwy 25 (4 Dec 04)
It seems like it s like an MDA but I don t really understand the point of having that in the middle of a segment.

[tescoapp]

A step down fix is due to some sort of obstacle in the approach segment or some sort of political thing eg flying over built up areas etc.

It is usually defined as an altitude with a distance from an approach aid or another aid.

It means while you decend on your approach your not allowed to decend below that altitude until after that distance/aid has been reached. After you have met the restriction and past the distance defined or aid on the plate you can then decend to the next restriction which could then be the MDA or missed approach pt or another step down. But there is only meant to be one between FAF and MDA/missed apt point.

There is no need to see the offending obstacle you just have to make sure you don't decend until after the restriction. Its a not below restriction so it is possible to go over the top of it with several hundred feet to spare.

http://edj.net/cgi-bin/echoplate.pl?SouthEast/MCO_vdr18R.gif

use this plate if you have any more questions then everyone can see what you are on about. As you can see from that plate you have three step down restrictions from the platform height but only one after the final approach fix which is the wee cross.

It doesn't help that there are 3 different flavours of plates in the uk and they all display the information differently