Descent below MSA in an instrument approach

[JulieFlyGal]

I remember reading in the AIP a while back, that a descent can be made below your MSA (or holding altitude limit?) during an instrument approach once you have confirmed your fix over the aid. It said something along the lines that once you're established outbound, or turning towards your outbound track, you may commence your descent below the MSA to your MDA.

Can someone give me the AIP reference to this? I can't seem to find it in the AIP anymore, and yes, I've searched both the hard copy and the online version.

[pylet]

Julie,

AIP ENR 1.20.2, or for the online version click on the 'Approach Procedures, Use of Navaids' in the Index.

What you have said is correct, except that descent to the approach MDA after the initial fix is allowed only if no other altitude requirement exists - which they usually do in a comman reversal procedure for an NDB or VOR approach, with descent to the final MDA allowed once established inbound.

[JulieFlyGal]

well there you go, thanks pylet! :ok: much appreciated.

as its written, it seems to imply that you only need to turn to intercept the outbound track to commence descent. or do you have to be established on the outbound track before descent? it's not 100% clear.

now, as for the reference numbering system of the AIP, is there any logic to it all? what a mess!!

[desmotronic]

You do not have to be established outbound to descend, but you do inbound. Once upon a time you did but no longer.

[ZappBrannigan]

From Jepp Terminal 3.5.2 (which will be word for word from AIP) - "for an approach which incorporates a reversal procedure, if an outbound descent is specified, the descent to the specified altitude may be commenced after the aircraft has crossed the fix or facility and is established on the specified track or has turned to a heading to intercept the specified outbound track".

So you need to be established or on a heading to intercept. If you're entering the approach directly from the hold (or from a procedure turn after the hold), i.e. the inbound track in the hold/procedure turn is the same as the outbound track in the approach, you can commence descent on station passage. If you're directly entering the approach, i.e. approaching the aid +/- 30 degrees to the outbound track of the approach and immediately commencing the approach on initially reaching the aid (i.e. skipping the sector entry/hold/etc.), then you need to have turned onto a heading to intercept the outbound track before you can descend.

So to answer your question specifically, no, you don't need to be established, only on a heading to intercept.

[The Green Goblin]

You do not have to be established outbound to descend, but you do inbound. Once upon a time you did but no longer.

You don't have to be on track inbound to descend, just within tolerance i.e 5 degrees :ok:

[ZappBrannigan]

You don't have to be on track inbound to descend, just within tolerance i.e 5 degrees http://static.pprune.org/images/smilies/thumbs.gifGetting technical here, but I believe as far as most procedures are concerned, within tolerance (+/- 5 deg or half scale deflection) = established, so you're both right :)

[UnderneathTheRadar]

So, back to the original question - when can you descend to the minimum holding altitude when that is less than the MSA? (Refer YPID for example - MSA2100 - Min Holding alt - 2000).

I don't think I've ever seen a reference for that.......

UTR

[AussieNick]

you'd think when established in the holding pattern

[ZappBrannigan]

So, back to the original question - when can you descend to the minimum holding altitude when that is less than the MSA? (Refer YPID for example - MSA2100 - Min Holding alt - 2000)Assuming enroute LSALT > 2100 - you can descend to 2100 within 25nm, then commence descent to 2000 when overhead the aid, whether entering the approach directly or not.

YPID is not the best example for further descent in this case as there is no descent during the outbound leg of the approach - you remain at 2000 until established inbound. In all cases though, when MSA > min holding altitude, descent to holding altitude can be commenced once overhead the aid.

Have a look at the YSHT NDB plate - if we're approaching from the south with an enroute LSALT of 4000, we can descend to 4000 any time along the route, 3800 within 25nm MSA, 2800 within 10nm MSA, 1900 once initially overhead the aid, 1800 once established outbound on the approach, or on a heading to intercept outbound track, and MDA once established inbound on the approach.

[ZappBrannigan]

you'd think when established in the holding patternThe procedures only state you must have arrived over the fix or facility/navaid. So descent to min. holding altitude can be commenced once overhead the aid, regardless of whether you're established in the hold or not. So in the Shepparton case, if you're arriving from the south-east, you can descend to the 2800 MSA at 10nm, then overhead the aid commence a sector 2 (teardrop) entry and descent to 1900, setting you up for the approach entry at 1900 without flying a holding pattern.

[JulieFlyGal]

thanks for the responses. so outbound i don't need to be established to descend, only inbound as stated by;

desmotronic:
You do not have to be established outbound to descend, but you do inbound. Once upon a time you did but no longer.

ZappBrannigan:
So to answer your question specifically, no, you don't need to be established, only on a heading to intercept.

The Green Goblin:
You don't have to be on track inbound to descend, just within tolerance i.e 5 degrees

i just hope the ato agrees when I do my test! lol!

[ZappBrannigan]

i just hope the ato agrees when I do my test! lol!If this is for a flight test, then I'd make the pretty safe assumption you won't be doing any direct-entry approaches (i.e. you'll always be flying a sector entry and probably at least one pattern), so when entering the approach, you should already be within tolerance, or just outside and making small heading changes to intercept - either way, you can descend in the outbound leg. As mentioned, inbound, you have to be established to descend, i.e. within 5 deg of track on the NDB, half-scale on the VOR.

It's good to have all these little details nailed down for test day, they're the kind of things that are likely to crop up in the oral exam.

The biggest bit of advice I can give you when flying these approaches in your test - don't stress out and fall to pieces if you're slightly outside tolerances now and again, but do something about it when it happens. Most ATOs won't fail you if you're suddenly 7 deg out when the test criteria requires 5 deg max, as long as you don't sit there for 15 seconds staring at the ADF, wondering what the hell you should do next.

[AerocatS2A]

The procedures only state you must have arrived over the fix or facility/navaid. So descent to min. holding altitude can be commenced once overhead the aid, regardless of whether you're established in the hold or not. So in the Shepparton case, if you're arriving from the south-east, you can descend to the 2800 MSA at 10nm, then overhead the aid commence a sector 2 (teardrop) entry and descent to 1900, setting you up for the approach entry at 1900 without flying a holding pattern.
That's reasonable. All of the sector entry procedures have you flying over the same patch of ground as the actual holding pattern, so in terms of terrain clearance, it doesn't matter if you're in a sector entry or in the hold itself.

[blackburn]

May I draw attention to the following extract from CAO 40.2.1 Appendix 1 (Instrument Rating Test)

(a) NDB ± 5 degrees of nominated track; for NDB procedure,
descent shall not be commenced unless established
within this tolerance; and
(b) VOR ± 5 degrees of nominated track; for VOR procedure,
descent shall not be commenced unless established
within this tolerance; and etc etc

This clearly says that descent shall not be commenced unless established within the stated tolerance!!

I recall some years ago that the statement in the AIP re being on a heading to intercept the outbound track, was to be followed by a re-wording of the CAO but it never happened. Therefore the AIP statement does not have a "head of power".
Note that the following extract from the Instrument Rating Test form still shows:

31 - NDB - entry and holding pattern correctly flown ± 100’
32 - tracking within ± 5 degrees
33 - altitude +100’ - 0’ at minima
34 - ident monitored during approach
35 - VOR - entry and holding pattern correctly flown ± 100’
36 - tracking within 1/2 scale deflection
37 - altitude +100’ - 0’ at minima

I was at a CASA Professional Development Program workshop for ATO's last week and no mention was made of any deviation from the stated tolerances on the test form. I guess this subject will continue to be one of mis-interpretations for some time! (Note that Jepps is a direct copy of the AIP info)

Blackburn

[ZappBrannigan]

Blackburn - interesting. I don't see any of this as a "deviation from the stated tolerances" - the tolerances are still always +/- 5 degrees, the only real question is whether you can commence descent on the outbound leg of the approach before you're technically "established", i.e. on a heading to intercept. What I'm saying is, the tolerances themselves aren't relaxed.

The CAO reference is interesting, seems to conflict. The later info you quoted from the test form doesn't seem to conflict too much in my opinion - the tracking tolerances are still +/- 5 degrees, and this isn't changed by allowing an early descent.

The only time this should be really significant (assuming an accurately flown entry/hold) is when commencing the approach immediately over the aid (i.e. no sector entry or hold), where you may be up to 30 degrees off the outbound track as you turn to intercept. So shouldn't be an issue on test day.

[muffman]

Yes, my understanding is that during a flight test you are being assessed in accordance with Appendix I of the CAO and therefore shouldn't descend unless you're 'established'.

"Flight within the tolerances specified is necessary for the applicant to be
judged proficient in the required flying manoeuvres"
-CAO 40.2.1 Appendix I para. 3.1

Outside of your flight test/renewal, I can't see any reason why you need to refer to that appendix and could therefore follow the AIP instruction and descend once on a heading to intercept the outbound track.

:ugh:

Edited to add: The situation could potentially arise after a parallel entry if you elected to track back to the aid without intercepting the inbound track of the holding pattern. You may end up commencing the approach from the limit of the 30 deg.

[ZappBrannigan]

As usual, now I'm questioning myself. Yes I tend to agree muffman.

JulieFlyGal, I'd probably go an ask my instructor for the official line on this little conundrum - at least that way you've got a proper source to blame :)

[desmotronic]

Blackburn if you tried that bollox on me i would smack you in the mouth with the AIP and then not pay you.

[AerocatS2A]

The trick is to confirm the requirements of the test with the testing officer (if he's any good he'll brief you on the specific requirements of the test). In my experience, all testers have considered descent on the outbound leg to be when established on an intercept heading. Of course, in addition to this, you can't descend INBOUND until established on track, which is probably what the intention of the CAO is.

My experience is also that SUSTAINED flight outside the tolerances is a no no, however if you get outside tolerances, immediately recognise and correct the situation then that has been ok.

[UnderneathTheRadar]

I think that CAO40.2.1 hasn't been changed since the AIP was changed.

However as that's what you're getting assessed on you'd better make sure your clear with your ATO prior to the flight - you'd hate for them to fail you for not knowing what was in the AIP!

[Zoomy]

Just my little say, regardless of the conflict between CAo and AIP and the differences of opinion, may I suggest you fly as accurately as you can the hold, the outbound and inbound leg.