Hi Bob,
I've got 2 questions regarding the Armidale Rwy 05 NDB/DME and NDB approaches that are used as an example in your IREX book.

The first question is about the DME Arc Arrival procedure (pls bear in mind I am using Jepps instead of DAPS). From the explanation in the book and what I can see in the schematic drawing of the approach, an aircraft can descend to 5000 once it passes the lead bearing as it turns onto final approach. However, the decent profile diagram makes it appear that the aircraft maintains 5100 until 5.2DME at which time a 3 degree descent is commenced. This matches up with the distance/altitude table which has 5100 at 5.2DME. Am I correct in assuming that during this approach, the pilot has the option to descend to 5000 once past the lead bearing? In practice, would you just maintain 5100 until 5.2DME?

The second question is for the reversal procedure. The procedure begins over the aid at 5800ft. I am assuming that 5800ft is maintained on the outbound leg until the turn onto finals when descent to 5000 can be made (indicated by the '5000(NDB)' pointing to the FAF on the descent profile diagram). Is this correct?

Hopefully I haven't made a dogs breakfast of this!

Thanks very much.

Mark

G'day Mark, welcome aboard.

I reckon you're right on both counts.

The underlined altitudes are all "at or above" values and that the distance/altitude table values are ideal values for the 3 degree approach path.

For your first question, you would have to remain at or above 5100' while on the arc and then once turning inbound you may descend to not below 5000'. You could just stay at 5100' until 5.2 DME if you wished and then intercept the described 3 degree approach slope.

As to what's best in practice? Good question! I reckon as long as you try to follow the ideal descent path and descend at 3 degrees it doesn't matter whether you join it at 5.2 nm from 5100 or at 4.8nm at 5000'.

Another question thrown out to the forum though: what about the idea of descending to MDA straight after passing the FAF on an NPA (like they do in the UK to maximise time at MDA to get visual)? Is that a problem here? I mean on the Armidale chart theoretically your descent path would be 1.8 nm earlier than the ideal one profiled!

What do you reckon Bob?

As for the reversal procedure, yep, maintain not below 5800' until you commence your descending turn inbound to cross the FAF at not below 5000' after which you can continue the descent.

Cheers

Rich

The approach caters for aircraft equipped with NDB only or NDB plus DME. If you had no DME you would of course be doing the reversal procedure. You would remain at 5800 outbound for 2.5 mins then not below 5000 until established on final [042 inbound]. There is no reason why you could not then descend to the MDA of 4150 and hope for a break for visual circling.

If you were DME equipped, it would not be illegal to descend to 5000 after passing the lead bearing, then, at 7 DME descend to MDA as above. The 3° approach path is designed for RPT type aircraft that wish to establish a stable approach profile. They would remain at 5100 until 5.2 DME, then set up a descent rate equal to five times the ground speed to maintain the 3° approach profile. That would get you to MDA with room for a level segment of about 2nm to the missed approach point.

Bob

Thanks very much Richard and Bob for your replies. All cleared up!