G'day Stuart

In reference to your previous post … " I'll have to ask Gavin about that one "

No need - I found the answer in AD MoS 6.2.30.1 (see below).



Sorry about the red herring guys!

Loved the discussion always good to analyse everything as we are always challenged by CASA and Air Services with trying to present some sort of coherence of the concepts that is supposed to be presented by the legislation


Cheers

Answer back from the CASA airports engineering guru -

Firstly, the comment in the current MOS 139, para 5.2.2.1 (b) about stopway not being involved is incorrect and has been edited out of the new MOS 139 document which is due to be come into effect next year. The diagram at 5.2.2.2 is correct.

TORA is the length up to the white runway end line that stretches across the runway at the keys. Beyond this point you are expected to be airborne but at least in ground effect accelerating to climb speed.

TODA is the TORA plus all of the available distance to the end of the runway strip by which point you are expected to be at no less than 35 ft.

The stopway is not a mandatory inclusion but if it is provided it needs to be the same surface as the runway proper so that an aborted takeoff will see you hopefully stop on the bitumen.

The clearway is very commonly a grassed area beyond the end of the bitumen and up to the white gable markers. It is not required to have the same strength as the runway and is not required to be 100% level but the land itself must not exceed a 1.25% slope starting at the end of the TORA and climbing away from the runway.

So, the TODA will include stopway and clearway to the white gable markers which mark the boundaries of the runway strip.

The comments revolving around the ICAO difference refers to the Australian practice of allowing the airport operator to declare the grassed area between the runway end and the gable markers as clearway. The last sentence in the paragraph about stopway has been tacked on and is incorrect and does not relate to the ICAO difference.

There you have it.

Firstly, the comment in the current MOS 139, para 5.2.2.1 (b) about stopway not being involved is incorrect and has been edited out of the new MOS 139 document which is due to be come into effect next year.

That removes the ambiguity nicely!

The diagram at 5.2.2.2 is correct.

From the diagram at 5.2.2.2 (below) we now have three definitions for TODA in Australia

1) TODA = TORA + EOS (End of Strip)
2) TODA = TORA + Stopway + EOS
3) TODA = TORA + Clearway (The training text book definition)

Obviously 1 & 2 can be combined to TODA = TORA + distance to end of strip (something that you do not see in the training text books)



Thanks for clearing this matter up!

Answer back from the CASA airports engineering guru -

Firstly, the comment in the current MOS 139, para 5.2.2.1 (b) about stopway not being involved is incorrect and has been edited out of the new MOS 139 document which is due to be come into effect next year. The diagram at 5.2.2.2 is correct.

I would appear that the error was not edited out - how frustrating!

The new Aerodrome MoS dated, "July 2020", still contains the same error - see below.



FYI only!

As the wise men say "the best laid plans of men and mice ..."

However, while we may presume that the matter will be addressed at some stage, it really is not a problem. The words, as they are written, ought not to be read and interpreted other than in a manner which identifies the final sentence as being irrelevant and quite out of place.

The bits I note are

(a) the document principally is concerned with heavy aircraft operations, hence the reference to a screen of 35 ft rather than 50 ft as is appropriate for light aircraft. However, perhaps we can put that to one side for the discussion ...

(b) when it comes to the clearway bit, we have a two branch decision path -

(i) if there be a clearway declared, then the clearway is part of the TODA - that's easy enough.

(ii) if there is no clearway declared, then the local (ie Australian) practice, which is registered in accordance with Australia's responsibilities (as a Convention Signatory) under ICAO requirements, is that the distance remaining beyond the TORA until the end of the strip is part of the TODA.

The final sentence "Any stopway is not involved", by any rational linguistic interpretation, is nonsense. Why ? Simple.

(a) if there is a clearway declared and stopway, then the stopway is part of the TODA and lies under the post TORA section of the TODA. No other interpretation makes any logical sense ?

(b) if there is no clearway declared, then any stopway, necessarily, must lie under the defacto clearway existing per the local practice between the end of TORA and EOS.

Or am I just being difficult ?

Out of curiosity, I did a little digging into the registered ICAO difference that the Aerodrome MoS 5.2.2.1 (b) references - i.e. the Australian practice of including the grassed area at the end of the runway in the TODA.

That led me to www.airservicesaustralia.com/aip/pending...o/icao_standards.asp - annex 14
Reading through annex 14 - volume 1, I could find no reference to the so called registered ICAO difference that the Aerodrome MoS alluded to. I could be that I am looking in all the wrong places!

the document principally is concerned with heavy aircraft operations, hence the reference to a screen of 35 ft rather than 50 ft as is appropriate for light aircraft. However, perhaps we can put that to one side for the discussion ...

I don't think aerodrome surveyors are concerned with the operational matters like screen height. That being said, it can be put aside.

(a) if there is a clearway declared and stopway, then the stopway is part of the TODA and lies under the post TORA section of the TODA. No other interpretation makes any logical sense ?

To my mind, the Stopway in this scenario is redundant. The Stopway lies under the Clearway, hence TODA = TORA+Clearway. This is the ICAO/Australian convention when a clearway is provided.

(b) if there is no clearway declared, then any stopway, necessarily, must lie under the defacto clearway existing per the local practice between the end of TORA and EOS.

This is premised on the assumption of "(a)" above being correct.

---

To my mind, the Australian registered difference (that I can't find) has created a problem for CASA. In particular, the Australian difference impacts on the ICAO definition of TODA where the runway is served by a Stopway only - ref to diagram "C" below.



The final sentence "Any stopway is not involved", by any rational linguistic interpretation, is nonsense.

This would suggest that this sentence is a band-aid solution to the problem. It brings the Australian practice back into line with the ICAO practice.

But then again, I could be dreaming.

It's a tad frustrating, of course ...

We need to keep in mind -

(a) Australia has moved to align more closely with ICAO over the past few years

(b) however, ICAO recommendations don't become prescriptive in a Contracting State until the State adopts them. The State is perfectly entitled to adopt varying procedures but has an obligation to publish such variations. We really should maintain an awareness of the ICAO bits but still keep in mind that it is the Australian rules which will get you hung out to dry in court ....

(c) I don't claim expertise on just where every variation is published so I will need to go back to Canberra and ask the question.

(d) I don't think aerodrome surveyors are concerned with the operational matters like screen height. Probably not relevant as the surveyors are well down the chain. The Canberra group gets to play with the rules.

(e) To my mind, the Stopway in this scenario is redundant. Of course that is the case so far as TODA is concerned. Stopway never has any prescribed relevance to TODA except by association with any overlying clearway considerations.

(f) This is premised on the assumption of "(a)" above being correct. I remain a simple-minded engineering chap. Functionally, I don't see any real pilot difference in the two cases cited.

so I will need to go back to Canberra and ask the question.

Email sent. Will advise when an answer arrives back in due course.

I'm not sure how we did it but we both appear to have been looking at the superseded document. How ?, I've absolutely no idea ! I downloaded it again earlier this morning before my previous posts so I am totally at a loss to know what happened or whence came the document to which I was referring. My error in not double checking that I had the current version .... Guess I will just have to drop a tear into my beer tonight in atonement.

My contact came back, somewhat perplexed with my questions. I downloaded the MOS, again, and, lo and behold, it is different to what I was reading this morning ? Indeed, it is a very different document.

Anyway, points to note, I suggest -

(a) The new Aerodrome MoS dated, "July 2020", still contains the same error - see below.

The present version is 2019, not 2020 ?

Part 139 (Aerodromes) Manual of Standards 2019

I, GRAEME MILLS CRAWFORD, Acting Director of Aviation Safety, on behalf of CASA, make this instrument under regulation 139.005 of the Civil Aviation Safety Regulations 1998, and section 4 of the Acts Interpretation Act 1901.

[Signed G.M. Crawford]

Graeme M. Crawford
Acting Director of Aviation Safety

5 September 2019


(b) 5.2.2.1 doesn't exist any more.

(c) the previous reference certainly appears to have disappeared.

(d) Differences are at www.airservicesaustralia.com/aip/pending...o/icao_standards.asp. However, my contact advises that the relevant section has yet to be updated post the new MOS 139 so, I guess, we will need to stand by for developments, there.