MDA correction for area QNH

[Agent86]

Can anyone point me to the Jepp reference to this?
AIP DAP 1-3 (https://www.airservicesaustralia.com/aip/current/dap/GINNO04-131.pdf) states

1.11 -AIP ENR 1.5 para 5.3.3 advises that "Where the forecast area QNH is used, the minima used must be increased by 50FT".
All ASA instrument approach procedures include this adjustment where a regular TAF service is not available(AIP GEN 3.5 para 16). No adjustment is necessary to meet the requirement of AIP for those aerodromes.
When an aerodrome receives a regular TAF service and the TAF is not available the AlP paragraph is applicable.

(For info AIP GEN 3.5 para 16 lists those aerodromes that DO have a TAF available)

And if no reference is provided in Jepp does this mean that the 50 ft need not be applied as the Jepp forecast minima is the same as the DAP minima?

[kalavo]

Switched to Jeppview which doesn't keep the same format, however notes from way back when suggest it should be in Terminal, AU, Instrument Approach / Take off Procedures, Paragraph 5.3 (specifically 5.3.3). It was page AU-26 but this may have changed.

Same requirements apply, Jeppesen has just copied the Airservices data, but in their format.

[compressor stall]

Doesn't it tell you on each chart?

[HappyBandit]

compressor stall

I think you might be getting a little confused with TAF/TTF etc forecast and an aerodrome with no TAF. If forecast TAF with no AWIS/AWIB/ATIS/approvoved observer eg tower, then yes minima is on the charts and is typically 100ft above the lower minima with actual.

If no TAF and only have AREA forecast then 50ft added.

[Agent86]

Kalavo and HappyBandit.
Both of you allude to the same point as I have used so far , ie No TAF or actual QNH means use area and add 50 ft.

However I regularly go to places that do not have a TAF service as opposed to no TAF available. In this case AIP states that the adjustment need not be applied.
The Jepp ref 5.3.3 is the "add 50ft if using area" as per AIP.
What I am looking for in Jepps is the caveat as quoted in DAP.

[Agent86]

VNAV_PTH,

What I am questioning is Airfields that have an approach but no regular TAF service.
The original quote from DAPS states that these plates already have this "adjustment" included in the minima so there is no requirement to add the 50 ft.

I can not find this caveat in Jepp but as the forecast/actual minima in Jepp are the same as in DAP for these airfields, I can see no reason to add the 50 ft.

[Bograt]

Slightly OT but can't AWIS/AWIB/ATIS/approved observer within 100NM be used for an accurate QNH?

AIP ENR 1.7-2 para 2.1.2 refers.

ie You don't need one on the field in question.

[Agent86]

Bograt,
You can use that QNH for a local QNH. However for instrument approaches. AIP ENR 1.5 -33 para 5.3.1 (QNH sources) specifies

a. the actual aerodrome QNH from an approved source, or
b. the forecast Terminal QNH, or
c. the forecast area QNH.

No mention of local QNH so we are back to forecast area QNH as the only applicable QNH.

[scavenger]

Slightly OT but can't AWIS/AWIB/ATIS/approved observer within 100NM be used for an accurate QNH?

AIP ENR 1.7-2 para 2.1.2 refers.

ie You don't need one on the field in question.

I have noticed this idea becoming more common. The altimeter is the most important instrument for IFR and to use a QNH for an aerodrome 100 NM away is lunacy, especially if it is treated as an approved QNH for the purpose of reducing the MDA/DA.

Agent86 is completely correct.:ok:

[kalavo]

Agent 86, take a break for five minutes and have another read of it.

All approaches in Australia are designed as if you are using Forecast Terminal QNH.


If you have an actual QNH (ATC, ATIS, AWIS or CASA approved met observer and valid for 15 minutes) you can reduce the Forecast Terminal QNH minima by 100'.


If you do not have a TAF or TTF and hence no forecast Terminal QNH, you can use Area QNH, but you must increase the Forecast Terminal QNH minima by 50'.


It makes no difference whether your aerodrome has a regular TAF service or not. Though my understanding is BOM will provide a TAF on request for any aerodrome with an approach.

The only difference between DAPS and Jepps is the way they display the same data. Jepps likes to show the minima for Forecast and Actual QNH (but not Area), DAPS only shows Forecast. My guess is their reasoning is approach design varies a little worldwide, and they don't want people doing something dumb at 4am after a long overseas flight, because their country of origin's approaches are designed to actual QNH.




Edit:

Sorry reread your original question. You should find the places you are going to do not have the shading next to the minima on AIP charts. On Jepp charts they will only have one minima displayed. In both cases you should be adding 50' if using an Area. If this still doesnt make sense, let me know the aerodrome/chart and we'll try and pick apart the difference properly for you.

An example of where a regular TAF service is not AVAILABLE (different to provided) is Bromelton in Brisbane. ASA charts not shaded (can't reduce the minima), Jepp's only provides one minima.

[Agent86]

Kavalo,
I have read and reread it. That's why I am asking the question.

Refer to YBRY
https://www.airservicesaustralia.com/aip/current/dap/BRYGN03-133.pdf
The Jep chart also has actual and forecast minima. However there is no regular TAF service.

Again even if you get a special on request TAF the para in DAP I qouted means you do not add the 50 feet. There is no corresponding (that I can find) dap introduction notes 1.11 in Jepp. Now that is probably a Jepp translation error and not an error in the source AIP.

[morno]

Hmmmm, it appears this has changed recently (black mark next to the paragraph, meaning it's been changed in the latest ammendment).

What I used to believe was the case, was any approach you did using Area QNH (regardless of the weather services provided), you added 50ft to the minima that did NOT account for accurate QNH.

What it now appears to say, is if the aerodrome you are conducting the approach into, is NOT subject to any weather service (TAF, TTF, METAR, AWIS/B) at any time, then it assumes that you will always be conducting an approach using Area QNH, therefore the minima has been worked out based on that assertion.

BUT, if the aerodrome DOES receive a weather service (even if not full time), if you shoot an approach using the Area QNH, then throw another 50ft onto the minima that doesn't allow for an accurate QNH.

There, clear as mud, :}. And thank you for alerting me to this piece of useful information that has changed, :ok:.

morno

[kalavo]

Nice find, it is an inconsistency.

Obviously losing it in my old age and failing to RTFQ.

Your next step is probably...
https://www.airservicesaustralia.com/contact-us/contact-form

They're generally more than happy to help, and given they're the primary publishers of the information can explain exactly what they mean, and speak to Jepps if Jepps don't have it (that we can find) or have it wrong.

Old copy of DAPS got binned so cant even look up a previous verison to see if it made more sense for you.

[Bograt]

@scavenger:


I have noticed this idea becoming more common. The altimeter is the most important instrument for IFR and to use a QNH for an aerodrome 100 NM away is lunacy, especially if it is treated as an approved QNH for the purpose of reducing the MDA/DA.


I was told this by the Head of Standards for a very reputable operator.

[alphacentauri]

I was told this by the Head of Standards for a very reputable operator. I would suggest that Head of Standards needs some further education.

The ICAO documents consider a remote altimeter setting source as being a source greater than 5nm from the intended landing aerodrome, up to a maximum of 75nm. There is an adjustment to MDA required of 5ft per NM greater than 5NM.

I would suggest that if you are using a remote setting source 100nm away then a 475ft correction needs to be applied to the minima. So this assertion that you can use setting sources great distances from aerodrome is plainly incorrect. Even a source 10nm away will need a correction of 25ft.

As to the questions regarding the use of Area QNH. As part of the procedure design process we are required to check if the aerodrome has a TAF service. If no TAF service available then we incorporate the extra 50ft into the published minima.

Alpha

[Wally Mk2]

An actual QNH can only be from the spoken word:-)

Wmk2

[Agent86]

AlphaCentauri As to the questions regarding the use of Area QNH. As part of the procedure design process we are required to check if the aerodrome has a TAF service. If no TAF service available then we incorporate the extra 50ft into the published minima.

By "we" I assume you are talking ASA and that is what the DAP intro para 1.11 refers to.

Any chance of the "we" letting Jeppesen know so they can add that little note into their "interpretation" of the AIP/DAP.

[ANCPER]

ATC AU-501
1.2 Altimeter Setting Rules
1.2.1.2 For ALL OPERATIONS at or below Transition alt (in the alt setting region), (see fig 1 pg AU 502), the alt reference will be:

a) the current Local QNH of a station along the route within 100nm of the a/c; or

b) the current Area Forecast QNH IF the current Local QNH is not known.

the above means on clb and desc.

AU-501
1.2.3. Local QNH
1.2.3.1. Local QNH, whether providedby ATS, AWS, or TAF or by using the alt subscale to indicate airfield elevation, is used as shown in figure 1. (AU 501)

In addition see MET AU-37, 4.3.1 & 4.3.5 (.......Therefore QNH from these AWSs may be used in accordance with TERMINAL INSTRUMENT APPROACH/TAKEOFF PROCDEDURES, QNH SOURCES.

Almost finally, see TERM AU-29, 5.3 QNH SOURCES, 5.3.1. Prior to passing the IAF, the pilots are required to set either,

a) the actual aerodrome QNH from an approved source, or

b) the forecast Terminal QNH, or

c) the forecast area QNH

Using common sense, does anyone think that Area F/cast QNH is more valid than a "live" actual qnh from within 100nm and is no more than 15 mins old, when the Area F/cast Qnh within that area only has to be within 5mbs and covers how many sq kms, and some think 100nm is too far. ICAO reference to distance and qnh for Oz has nothing to do with us.

WALLY, there is no definition of 'actual' qnh in Jepps that I can find which is why is isn't in caps, other than a dictionary definition of actual (actual |ˈak ch oōəl|
adjective
1 existing in fact; typically as contrasted with what was intended, expected, or believed : the estimate was much less than the actual cost | those were his actual words.
That means real, live, not f/cast!

[AerocatS2A]

Some of you guys are getting this bit wrong. You may use an actual QNH within 100nm of you in lieu of the area QNH, BUT all of the area QNH limitations still apply. You can not use the 100nm QNH to reduce any minimas or to waive the requirement to add 50' to the forecast QNH approach minima (Agent86's discovery aside.)

Example: You are going to aerodrome A and although it has a TAF service, there is no TAF available for your arrival. Normally you'd be required to use the area QNH and add 50' to the forecast QNH minima. However, if the area QNH covers a large area, as many do, and there is an aerodrome "B" only 40 nm away that has an AWIS, you may use the aerodrome B's QNH in lieu of the area QNH. The chances are it will be more relevant to the aerodrome you are going to than the area QNH would be. BUT you must still add the 50' to the minima, it doesn't allow you to use the TAF QNH minima or the actual QNH minima.

[DraggieDriver]

An actual QNH can only be from the spoken word:-)
Not if you get ATIS via ACARS and print it out :)

[Wally Mk2]

Ok "DD" (gee I hope yr not a sheila:-):) that's a fair comment although the source is still from the spoken word just written on bark with charcoal:ok:

'catS2A' that's good advice:ok:


Wmk2

[Rogan82]

It is my understanding, from consultations with Jeppesen while trying to get an approach published somewhere else in the world, that they just re format an existing approach. They do no survey work them selves and rely on the originators calculations for safety (please correct this statement if not accurate) Therefore all requirements of DAPs in ENR 1.5 must be applied to assure the same level of safety. If these requirements can't be found in Jep pubs then this may be a problem? I believe a USAF 737 crash highlighted the risk of relying on Jep re formatted approaches with appropriate supporting documentation.

[AerocatS2A]

Rogan, that is essentially correct. Jeppesen take the data and reformat it. Almost all of the AIP is contained in the Jepp manual verbatim. The only real differences are where the paragraphs refer directly to the format of the charts.

The problem here is that the DAPs have been formatted such that the area QNH correction is not needed if there is no TAF service for the aerodrome. The reason being that the only possible QNH you may use is the area one and therefore there is only one minimum you can use.

Jeppesen have reproduced the same minima from the DAPs but because this little quirk is effectively associated with the formatting of the DAPs, Jepp don't seem to have picked up that those charts already have the area QNH correction applied. The result is that if you read and use the Jepps exclusively you will add a further 50' to the minimum when it appears that this isn't actually required as the Jepp minimum is a duplicate of the DAP minimum.

[Agent86]

The interesting part will come next year when YBRY and YCWA get an AWIS but still no TAF service.

So you can use the Actual Minima (or take 100 ft if you use DAPs). However you should ALSO be able to take an additional 50 ft off as you are NOT using an area forecast.

For you boys/girls who fly to YFDF this should already apply!
Time for the Ops Support Departments to earn their money.


Alphacentauri, does my logic seem ... logical?

[alphacentauri]

Alphacentauri, does my logic seem ... logical? Yep, makes sense to me :ok:

I would have thought that if the aerodrome had an AWIS/AWIB then surely its not a too far stretch of the imagination that a TAF service could be provided....but hey it seems some people forget that a certain corporate business name has the word "Services" in it. :E

To be honest, I think all this is a dogs breakfast, but I don't make the rules I just have to follow them

[Agent86]

Jepps have finally caught up with AIP in the 1 Mar 2013 revision. See Terminal 5.3.3

[Icarus2001]

The interesting part will come next year when YBRY and YCWA get an AWIS but still no TAF service.

Well it just got interesting then...

I would have thought that if the aerodrome had an AWIS/AWIB then surely its not a too far stretch of the imagination that a TAF service could be provided

YBRY and YCWA now have TAF and AWIS, hence a METAR (AUTO).

No details NOTAM wise about frequency or phone number to access.

WA - WAIT AWHILE.

[Agent86]

I have forwarded a request to ASA asking if we can expect a reduction in the minima of the approaches by 50 feet.

Let's see if the "design" team are in tune with the "law" team :O

No details NOTAM wise about frequency or phone number to access

Without these it's not much help.
Metar doesn't help much and with TSO129 the alternate Req is still there.

It is nice to see that the BOM is not just cut and pasting TAFs for YFDF,YBRY,YCWA. Today YFDF has TS (Prob) but YBRY des not.

[FGD135]

Agent86,


What makes you think that the MDA for some approaches has the 50 foot correction "built in"?


Whilst it may seem logical for that to have happened - at those places served by neither a TAF nor an AWIS - it is also just as logical that this has not happened.

[AerocatS2A]

FGD, because the AIP says it has been built in.

[Icarus2001]

Let's see if the "design" team are in tune with the "law" team

"Hello, we're from the government we're here to help."

Probably bump the thread in another six months when left hand and right hand discover their mutual existence.

[alphacentauri]

I have forwarded a request to ASA asking if we can expect a reduction in the minima of the approaches by 50 feet.

This will be good. To whom did you forward the request? There are only about half a dozen guys in the company who would have any clue what you are talking about. If your email doesn't end up with one of those guys, you could be holding your breath a while....

The other thing to consider is that the rule in the MOS requiring this extra 50ft has only been around since 2006. Prior to this it wasn't applied. If these approaches were published pre-MOS then I am sorry to say that there will be no expected 50ft drop in minima....but I will check it out for ya

[Sqwark2000]

FYI, in NZ, if an aerodrome doesn't have a published QNH, then you use the nearest reported QNH, take the distance between the reported QNH and the aerodrome where you want to conduct an approach, subtract 5nm, then add 5ft for every mile remaining to the approach MDA.

Example:
Aerodrome A, with no published QNH, is 50Nm from controlled Aerodrome B.
50-5 = 45nm x 5ft = 225ft to add to the approach MDA for Aerodrome A whilst using the QNH from Aerodrome B .

[FGD135]

FGD, because the AIP says it has been built in.


Thanks AerocatS2A!


Well, that was a thoroughly dopey thing for them to do. Could you please give me an AIP reference on this. I am incredulous.

[Agent86]

FGD135. Read the initial post for the AIP ref :E

That's what started this thread :}

[AerocatS2A]

Well, that was a thoroughly dopey thing for them to do. Could you please give me an AIP reference on this. I am incredulous.

It's not that dopey. If you have an aerodrome that doesn't have a TAF, ever, nor an AWIS, then there can only be one MDA so you may as well publish the MDA that everyone is required to use.

[Oktas8]

If you have an aerodrome that doesn't have a TAF, ever, nor an AWIS, then there can only be one MDA so you may as well publish the MDA that everyone is required to use.

I beg to differ. It's that kind of thinking ("hey let's make it easy for the pilots by introducing an extra set of complexities into AIP") that has led to this two-page thread. What MDA shall I use if I have a privately-commissioned TAF? What if there's an airfield 8nm away with an ATIS, although this one has neither a TAF nor ATIS? What if this place has always had a TAF service, but last update BOM stopped providing the service?

'Twould be better IMO to follow the rest of the world. One MDA and only one on each plate, always surveyed for accurate local QNH source. If you don't have a local QNH... refer to these rules regarding adding xxx feet.

[kimwestt]

If there is no TAF, then the area QNH prevails.
Given that the area QNH is guaranteed to be within +/- 5 Mb, and at 30' per Mb, you then add 150' to the minima, unless your chart has a correction factor built in. Check for PANS-OPS.
If the area QNH is going to vary by more than5 Mb, then a speci would be issued.
QED?
:confused:

[Capn Bloggs]

I beg to differ. It's that kind of thinking ("hey let's make it easy for the pilots by introducing an extra set of complexities into AIP") that has led to this two-page thread. What MDA shall I use if I have a privately-commissioned TAF? What if there's an airfield 8nm away with an ATIS, although this one has neither a TAF nor ATIS? What if this place has always had a TAF service, but last update BOM stopped providing the service?

'Twould be better IMO to follow the rest of the world. One MDA and only one on each plate, always surveyed for accurate local QNH source. If you don't have a local QNH... refer to these rules regarding adding xxx feet.
That's illogical. What you're saying is print the absolute lowest MDA and let pilots adjust it up if they don't have a real-time QNH (applying "an extra set of complexities/rules"). The fail-safe method would be as is done now in AIP ("one MDA and only one on each plate"); print the higher and if you can go lower by applying rules and complexities, then it's up to you to do so. At least if you do nothing you won't be lower than you should be at the MDA.

[FGD135]

It's not that dopey. If you have an aerodrome that doesn't have a TAF, ever, nor an AWIS, then there can only be one MDA so you may as well publish the MDA that everyone is required to use.Here is why it is dopey to build the 50' correction in:

1.Let's say you are about to make an instrument approach to a place. Looking through the briefing material you printed before flight, you find that there is no TAF for the place.


So, you will be using the area QNH, but must you add on 50' to the published MDA or not? To answer that, you now need to delve into the Met section of the AIP (or check the ERSA entry) to find out whether the place has a TAF service or not. If not, then you don't add the 50'. If it does, then you do add the 50'.
2.If the IAL charts for a place have the 50' correction built in, then each time the TAF service status of the place changes, those charts must be amended and reissued.


Yes, I know that the TAF status for any one particular place doesn't change frequently, but over the course of a year, you may have one or two dozen places where the TAF status changes. That would then be one or two dozen lots of amendments to IAL charts that didn't need to happen.




The simplest approach, as others on this thread have alluded to, is to just have one published MDA, with no "built-in" corrections. That MDA could be the highest of the three possible, with the following corrections to be operationally applied:

1. Reduce MDA by 50' when the QNH is obtained from the TAF;
2. Reduce MDA by 150' when an actual aerodrome QNH has been obtained;

Alternative logic, that still keeps things as simple as possible, would be to have a published figure that assumes you have a TAF QNH. Then, if necessary, you:

1. Add 50' if using area QNH;
2. Reduce it by 100' if using an actual aerodrome QNH.

[Hempy]

Jeppesens pay ASA for their documents, reformat them and then resell the same information at a profit. Considering thats their business I think it's a bit rough to expect ASA to keep track on Jepps to make sure their documents marry to the official line (AIP)......surely thats Jepps job?

[Capn Bloggs]

I think it's a bit rough to expect ASA to keep track on Jepps to make sure their documents marry to the official line (AIP)......surely thats Jepps job?
My understanding is that it is CASA that approves Jepp (and others) to re-publish AsA stuff, so CASA should be oversighting Jepp.

Alternative logic, that still keeps things as simple as possible, would be to have a published figure that assumes you have a TAF QNH. Then, if necessary, you:

1. Add 50' if using area QNH;
2. Reduce it by 100' if using an actual aerodrome QNH.
I like it. Make it happen! :D

[Lasiorhinus]

Yes, I know that the TAF status for any one particular place doesn't change frequently, but over the course of a year, you may have one or two dozen places where the TAF status changes. That would then be one or two dozen lots of amendments to IAL charts that didn't need to happen.

How often does an aerodrome change from TAF to No-TAF? If we're talking about superfluous amendments to the plates, then let's take a look at tomorrows Jeppesen revision cycle, 20 Dec 13. Remember that this is not even a revision date at all for the AIP DAP.


Adelaide One SID amended due to "initial climb text".
Albury DME arrivals (all of them) amended due to Cat C Minimums.
Albury Aerodrome chart amended due to changed alternate minima.
All the other Albury approaches amended due to changed circling minima.
Amberley aerodrome chart amended due to "note added".
Ballina aerodrome chart amended due to alternate minimums.
Coondewanna aerodrome chart amended due to "note added"
Hughenden (all plates) amended due to AWIB added.
Leinster aerodrome chart amended due to runway length.
Lismore RNAV 33 amended due to mandatory altitudes.
Mackay aerodrome chart amended due to parking bays.
Mansfield RNAV 115° amended due to MSA
Melbourne aerodrome chart amended due to Note Added
Moorabbin NDB-A amended due to missed approach training note
Mildura(all plates) amended due to AWIS removed, AWIB added.
Mt Gambier aerodrome chart amended due to takeoff minima, lighting
Naracoorte GPS Arrival amended due to MSA and profile depiction
Naracoorte RNAV and NDB amended due to MSA
Osborne Mine aerodrome chart amended due to RWY 30 lighting
Osborne Mine RNAV 30 amended due to PAPI added
Sunshine Coast aerodrome chart amended due to RNAV-X alternate minima
Sydney aerodrome chart amended due to parking bays renumbered
Sydney ILS-Z 16R CAT II amended due to RA added
Sydney ILS-Z PRM 16R CAT II amended due to RA added
Sydney ILS-Z 34L CAT II amended due to RA added
Sydney ILS-Z PRM 34L CAT II amended due to RA added
Sydney VOR 16R amended due to straight-in minima deleted, altitude table
Tennant Creek all plates amended due to AWIS added.

I'd say the occasional once or twice a year an airport changes landing minima to be pretty minor in the grand scheme of things.



Alternative logic, that still keeps things as simple as possible, would be to have a published figure that assumes you have a TAF QNH. Then, if necessary, you:

1. Add 50' if using area QNH;
2. Reduce it by 100' if using an actual aerodrome QNH.

Perhaps I missed the sarcasm if there was any, but that is exactly how the current charts work. The published minima assumes you have a TAF QNH. If you are using Area QNH, then you do indeed raise the published minima by 50 feet. If you do have an actual aerodrome QNH, then you do indeed lower the published minima by 100 feet. That's what the shaded background indicates!

[FGD135]

Perhaps I missed the sarcasm if there was any, but that is exactly how the current charts work.


No, that is not exactly how the current charts work - hence the existence of this thread.


If you're using area QNH for an instrument approach, you may or may not have to add 50' to the MDA. Refer my previous post.

[noclue]

My understanding was this.

If the airport normally gets a TAF, but for some reason on the day you go it isn't available, then you must add 50'.

If the airport never normally gets a TAF, then you would have to use the area QNH anyway and as a result you don't need to add 50'.

[Oktas8]

Alternative logic, that still keeps things as simple as possible, would be to have a published figure that assumes you have a TAF QNH. Then, if necessary, you: ...

Point taken FGD. As you say, that would be simpler than the current.

However, I'm a very simple guy. I want a system that defaults to the experience of most pilots, most of the time. And that, of course, is ATIS or equivalent. (Not to forget pilots operating at remote and/or poorly equipped airfields. But take the total number of instrument approaches flown each year in Australia: much more than half are to airfields with approved QNH sources.)

Hence my wish that the default scenario is for an accurate local QNH. When I'm flying somewhere without local QNH (as all do sometimes and some do all the time) I know I have to apply an MDA correction.

If you need local knowledge to interpret the plate MDA correctly, it's less safe than it could be.

[Capn Bloggs]

If you need local knowledge to interpret the plate MDA correctly, it's less safe than it could be.
If you need local knowledge to increase the MDA, it's less safe than it could be. ;)

[Capn Bloggs]

So, you will be using the area QNH, but must you add on 50' to the published MDA or not? To answer that, you now need to delve into the Met section of the AIP (or check the ERSA entry) to find out whether the place has a TAF service or not. If not, then you don't add the 50'. If it does, then you do add the 50'.
Where's your reference for this? ENR 1.5 5.3.3 merely says:
Where the forecast area QNH is used, the minima used must be increased by 50FT.
No mention of the status of the aerodrome regarding a TAF service.

[Mr.Buzzy]

Meanwhile, in Australia, we have 3 pages devoted to a topic that is supposed to be clear, simple and unambiguous!
Well done Australia, if we can't go to the moon, let's at least make everything else a shot at it.

Bzbbzzbbzbzbzbzbzbzzzzzzzz

[Oktas8]

If you need local knowledge to increase the MDA, it's less safe than it could be.

That would be the current system Bloggs. The one where I arrive over an airfield with TAF QNH and wonder whether the place usually has a regular TAF service or not. What is the plate MDA based on? Head scratching. (Of course, local pilots would know.)

[FGD135]

Where's your reference for this? ENR 1.5 5.3.3 merely says: ...
Bloggsy, please take a look at the first post of this thread (by Agent86). It gives those references and asks the very good question about whether AIP differs from JEPPs with regard to the addition of the 50'.

[Capn Bloggs]

Yeh sorry FGD. One to you. :D Don't worry, I'll get ya next time!!

What MDA is Father Christmas going to use when he pulls into West Angelas next week on his Cat 3 C RNP AR WAAS night approach and landing??

http://www.smilies.our-local.co.uk/index_files/xmassleigh.gif

[Agent86]

Notam out for YBRY and YCWA

AIP DEP AND APCH (DAP) WEST YBRY AMD
TO ALIGN WITH DAP 1-1 GENERAL INFORMATION PARA 1.11, THE INTRODUCTION
OF THE NEW REGULAR TAF SERVICE ALLOWS THE PUBLISHED MINIMA TO BE 50FT
LOWER. WHEN THIS TAF SERVICE IS NOT AVAILABLE THE MINIMA MUST BE
INCREASED BY 50FT IN ACCORDANCE WITH AIP ENR 1.5 PARA 5.3.3.
NEW MINIMA IS AS FOLLOWS:
RNAV-Z(GNSS) RWY 10 S-I GNSS MINIMA 2950(894-5.0)
RNAV-Z(GNSS) RWY 28 S-I GNSS MINIMA 2700(644-3.7)
CIRCLING CAT A/B 3080(998-2.4) ALTERNATE CAT A/B (1498-4.4)
CIRCLING CAT C 3240(1158-4.0) ALTERNATE CAT C (1658-6.0)
FROM 01 100132 TO 04 100500 EST


The system works. Now for those of you who go to YFDF you had better go ask the same question of Airservices.

[AerocatS2A]

That would be the current system Bloggs. The one where I arrive over an airfield with TAF QNH and wonder whether the place usually has a regular TAF service or not. What is the plate MDA based on? Head scratching. (Of course, local pilots would know.)
How would you have a TAF QNH for somewhere that doesn't get a TAF?

I'd suggest that local knowledge isn't a major factor. When you plan your flight you will request a TAF from NAIPS and when it doesn't give you one you will investigate why.

The worst that will happen is you won't investigate and just assume the place normally has a TAF but doesn't today. You will get there, use area QNH or AWIS QNH from somewhere within 100NM and you will add 50' when you didn't have to.

[Car RAMROD]

You will get there, use area QNH or AWIS QNH from somewhere within 100NM and you will add 50' when you didn't have to.My bolding...


Was mentioned previously but obviously some people haven't been picking up on it or are being told incorrect things (not having a go AS2A, I just want to point it out again as I still hear lots of people getting this thing mixed up), but for an Instrument Approach you cannot use QNH from a place within 100nm; doing this is for all other operations is an altimeter setting rule. The Application of Aerodrome Meteorological Minima section "supersedes" this:


ENR 1.5-5.3.1
Prior to passing the IAF, pilots are required to set either:
a) the actual aerodrome QNH from an approved source, or
b) the forecast Terminal QNH, or
c) the forecast area QNH.


Absolutely ZERO mention of QNH from within 100nm for your approach.


Is it likely to kill you? No, but it isn't the correct way to fly the approach.

[Oktas8]

Aerocat, in my example I was thinking of a place which has not had a regular TAF, but now has one issued. It happens occasionally.

Usually, if you have a TAF, there is no ambiguity. As FGD pointed out above (post 41), a more common problem is when NAIPS cannot provide a TAF for YXXX and you must decide whether that is a one-off or a regular thing. As a commercial pilot, I'm not interested in adding 50' to an MDA without strict necessity.

At the risk of being repetitive, I think a good system is one that defaults to the correct option for most users, most of the time. That would be an MDA based on an accurate local QNH. (I wonder why Jeppesen charts provide exactly that as the primary or default option? Hmm.)

Cheers, O8

[Agent86]

Reviving an old thread.
The 2 Mar 2017 revision to AIP has removed Para 1.11 which started this off:
DAP-Reference (http://www.airservicesaustralia.com/aip/current/dap/GINNO04-150.pdf)

1.11 -AIP ENR 1.5 para 5.3.3 advises that "Where the forecast area QNH is used, the minima used must be increased by 50FT".
All ASA instrument approach procedures include this adjustment where a regular TAF service is not available(AIP GEN 3.5 para 16). No adjustment is necessary to meet the requirement of AIP for those aerodromes.
When an aerodrome receives a regular TAF service and the TAF is not available the AlP paragraph is applicable.
There is a subtle change bar with a D.

I asked ASA about this and they advised that CASA had requested that charts in the DAP (and hence Jeppesen) Effective 2 MAR 2017 don't include an extra 50ft in accordance with AIP ENR 1.5 par 5.3.4.

However ...the charts in question at any port that does not receive a TAF have not been revised to remove the 50ft :ugh:
So in accordance the aforementioned AIP Enroute ref we have to add 50ft to the published minima even though the data already includes it!

I was advised that "cyclical maintenance" would reduce the minima ...so expect another raft of revisions. Until then we are much safer being that much higher above the hard bits :suspect:

Just catching up with Worlds Best Practice I guess.

[Capn Bloggs]

...so expect another raft of revisions
More inconvenienced electrons! :{

[alphacentauri]

Um, its already been done. We took the 50ft off where it was applied at all locations over 12 months ago.

[MooseLoose]

Just been reading this post before my IPC and noticed that “Forecast QNH” is written, opposed to area QNH assuming within the 15 minutes. So would argue that adding 50 ft is not required with a valid area QNH.
What do you guys think?

[Capn Bloggs]

WHAT is an IPC?? Do you mean Instrument Rating Renewal?? :{ Speak Strine will ya?! :ok:

that “Forecast QNH” is written, opposed to area QNH assuming within the 15 minutes.
??
Neither the (Aerodrome) Forecast QNH or Area QNH have anything to do with the 15 minutes.

If you are using the Area QNH (there's no such thing as an "actual" area QNH) you have to add 50ft to the shaded MDA (DAP) or the Jepp "Forecast Terminal QNH" MDA. AIP ENR 1.5 section 5.3.4 refers. I will not even attempt to find the ref in the useless Jepp Airway Manual.

If you are using an Aerodrome Forecast QNH ie from a TAF, you don't need to add the 50ft. Just use the shaded MDA (DAP) or the "forecast Terminal QNH" (Jepp). AIP ENR 5.3.2 refers.

[Icarus2001]

Come on Bloggs, keep up, an IPC is strine, we have a world leading licence system now, Part 61 and all, no radio licence to show off overseas...

https://www.casa.gov.au/standard-page/changes-instrument-proficiency-checks

[Capn Bloggs]

Overseas? Where's that?! :}

[Icarus2001]

You know, where your car, electronics, aeroplanes, movies and tv come from.