NDB approach

[flywatcher]

I vaguely remember seeing somewhere that in a DME/GPS equipped aircraft it is legal to manoeuvre within 5 miles of the NDB to establish within the 30 degree arc for direct entry into the approach. If this is correct, and not a figment of my imagination can anyone point me to the reference? ps Never done it, just wondering if I can. Thank you.

[psycho joe]

As long as you're within the aplicable 25/10 nm msa and not below specified alt, you can manoeuvre as you like to establish direct entry.:ok:

[bentleg]

I vaguely remember seeing somewhere that in a DME/GPS equipped aircraft it is legal to manoeuvre within 5 miles of the NDB to establish within the 30 degree arc for direct entry into the approach. If this is correct, and not a figment of my imagination can anyone point me to the reference?


ENR 1.5 2.4.1 (3), may be what you are looking for.


2.4
Procedure Entry

2.4.1 An aircraft which is not required to hold or to lose height in a holding

pattern may commence the approach without entering the holding

pattern if:
a. in controlled airspace, ATC has cleared the aircraft to do so;
b. in any airspace, for procedures using radio navaids:
(1) the reversal procedure entry requirements of para


2.7


are satisfied; or

(2) the DME arc entry requirements of para

2.8 are satisfied;
or

(3) the en route track to the procedure’s commencement fix

or facility is within 30

° either side of the first track of the



procedure; or

[ZappBrannigan]

As stated, you can, however it can be a little hard to safely fly the approach if the MSA is significantly above the published initial altitude for the approach, as you can't begin descent from MSA until you're over the aid. Sometimes a couple of hundred feet makes all the difference between struggling to maintain a reasonable descent profile or not. I suppose it would be legal to descend on the DGA steps if available, to position you for a direct-entry approach at the correct altitude, but if you're doing this you might as well just fly the DGA (can't think of too many NDB/VOR approaches where the MDA is significantly lower than that for the DGA - correct me if I'm wrong).

[The Green Goblin]

On an NDB/VOR style approach with a published reversal I would generally divert from 25nm to pick up the straight in track of the reversal procedure.

It is my understanding that you can manoeuvre as required until you pass overhead the aid (within the 25nm MSA) which then determines what you are required to do (sector entry/holding pattern/ outbound on the reversal etc) Having said that If there was known traffic I would hold my inbound track at a safe height above the MSA (1000 feet separation +) and conduct the appropriate sector entry and a holding pattern if required until the traffic is clear.

If you are conducting the GPS/DME arrival you can track as required until you arrive at the FAF from which you must track direct to the aid following the published procedure.

Hope this helps :)

[ReverseFlight]

By way of example of what ZappBrannigan mentioned, the 10 nm MSA for the YSHT NDB-A is 2800' with holding MIN ALT at 1900' and a MDA (circling) of 1030', so I'd overfly the aid at 2800' and lose height in the holding to start the initial approach at 1900' rather than barrow down too early.

[grrowler]

I haven't got the latest YSHT charts, but from the ones I have, why wouldn't you just go straight into the approach? 2 minutes out plus the turn back in to lose 1000 feet (from 2800 10MSA to 1800 till established inbound) isn't exactly difficult to achieve.

I'd be maneuvering to make a direct entry, planning descent to arrive over the top a bit over 3000 and keeping a constant descent right through.

[ZappBrannigan]

Yeah SHT isn't the best example as you're only losing 100 feet outbound.

[ReverseFlight]

Agreed ZB and I wonder why the SHT plate wasn't designed as 2800' MSA straight down to the base turn at 1800' - it's a full 2 minuter - I'd hate wasting time in the holding too.

How about LTV ? 10 NM MSA is 3900' (assume you're not tracking or sidestepping due east), holding at 3000', initial approach is a 2-minuter down to the base turn at 1700' and then final approach down to 980' circling MDA. Now you'd probably won't be losing 2200' in the 2 minutes ? Might be a bit too steep and uncomfortable for some.

Just trying to help come up with some examples.

[grrowler]

I wonder why the SHT plate wasn't designed as 2800' MSA straight down to the base turn at 1800' Isn't that exactly how it is designed?

I understand the point you are trying to make, but even with YLTV, if you're anywhere near a direct entry, you're going to be (or would easily maneuver to be) in the 3000' MSA sector, and you've got more like 3 minutes to lose the 1300' (2 minutes outbound plus descending in the turn inbound). If you need to do a parallel or teardrop you've got an additional 3 minutes to lose the 900 feet.

[ZappBrannigan]

RF, if you're asking why the initial approach altitude is 1900 and not 2800 at SHT, that's because the 25nm MSA to the NW is 1900, and it's logical to have your holding/approach entry altitude equal to or less than the lowest MSA on the chart. If you're approaching from the NW you're going to step down to 1900 to get clear of cloud if possible and conduct a visual approach - and if you're not clear at 1900, it's silly to have to climb 900 feet to conduct the NDB approach. As it's published now, we can step down to 1900 from the NW, and if not visual, manoeuver for a direct entry to the approach at 1900.

Growler is right, LTV is another one where a chunk of the 25 MSA is lower than the 10 MSA, and the slice of the 25 MSA to the W allows you to make a nice direct entry at 3000.

I'll try and find an example. My Jepp amendments just arrived in the mail, damn that's a fat one.

Edit: the Innisfail NDB is probably a reasonable example - approaching from the N, to make a direct entry you'd have to lose 4200 feet by the end of the base turn - maybe a bit steep.

[grrowler]

Depends on what aircraft you are flying, but another couple are maybe Cairns NDB-B from the south (5600' - 2000' in 3 (cat c/d) or 4 (cat a/b) min) or Tamworth NDB-A from the south (5000' - 2700' in 2/2.5 min).

[ReverseFlight]

Thanks for all the comments which I agree.

ZB, I was imagining approaching SHT on say B-220, but the 25 NM MSA is 1900' only up to B-208 which is not technically in my sector, although in practice I would sidestep to within +/- 30 degrees of 170 (say 200) to go straight into the initial approach 170.

On the same theme for LTV, grrowler, I can't imagine anyone not sidestepping into the 3000' MSA sector to track within +/- 30 degrees of the 047 initial approach (say 077) even if I were tracking B-100+ coming in, again avoiding time in the holding.

As for IFL I presume ZB is talking about arriving from the NW and tracking say 120 (arriving from the north would require a sector 1 entry with reversal, what a pain). The straight-in might work with Cat A/B (3.5 mins) but probably not with Cat C (2.5 mins) but then again the 2300' limit on the base turn is a floor, not a designated height, and there's only another 1370' to lose on final approach. If you allow a full minute for a rate one base turn, you'd be descending a total of 5570' in 8 mins which means the RoD is less than 700 fpm, quite manageable for Cat A/B at least. To summarise:

Innisfail
A/B (6500 - 930) / 8 mins = 696 fpm OK
C (6500 - 1480) / 6 mins = 836 fpm - depends ?

Cairns
A/B (5600 - 1360) / 7 mins = 605 fpm OK
C/D (5600 - 1720) / 5 mins = 776 fpm OK

Tamworth
A/B (5000 - 2100) / 4 mins = 725 fpm OK
C/D (5000 - 2500) / 3 mins = 833 fpm - depends ?

[grrowler]

Descending like that is going to have you reaching the MDA way too close to the NDB (MAP) IMHO. Just look at whether you can achieve the outbound altitude limit by the time you get established inbound, in a stable manner, and if so just aim for that. This means you have the maximum time at the MDA to spot the runway, determine where you're going to circle, etc. If the MSA has you too high to achieve that, then just lose height in the hold.

NDB's should all be #%*$ed off anyway!:}

[ReverseFlight]

Just a postscript to this thread - something I discovered while revising for my IR renewal. It's under ENR 1.5 para 1.19.2, which states that an aircraft may commence a segment in excess of the specified commencement altitude (subject to any upper altitude limitation) but the rate of descent after the FAF should not normally exceed 1,000 fpm. :ok: