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PCN, Subgrade Strength, Tyre KPa, Runway Length...  
User currently offlineNZ8800 From New Zealand, joined May 2006, 425 posts, RR: 2
Posted (8 years 4 months 3 weeks 2 days 20 hours ago) and read 9984 times:

Quite a bit of data here, and quite a few questions about runway strength, subgrade strengths, tyre pressure, certification, non-certification and allowable aircraft size!

To start with - a question about PCN/ACN/LCN. Firstly, what do they stand for?
Secondly - what is the difference between them? I think they're to do with the runway strength but I have a feeling that a high number on the PCN does not necessarily mean a stronger runway - is that right?
Is there a minimum PCN etc for certain aircraft to be operated into the airport?

Does the subgrade strength = weight of aircraft that can land on it? The data following seems to conflict a little.

The following information is from airport charts. 7 airports selected have regular airline service (Whenuapai being the exception), the first 3 with SF3 and DH3 aircraft (AT7 as well for Napier), the last 4 (including certificated Westport) with BEH aircraft).
The certificated airports mean aircraft with 30+ passenger seats can be operated regularly - this might be common all over the world.

These particular airports were chosen as Napier, Nelson, and New Plymouth are among the busier regional airports, with similar aircraft but rather different runways (although length is fairly similar). Westport was chosen due to a different formula (LCN) and I wondered how this translated to runway strength, as was (to a point) Whakatane.
Whenuapai was added in as I can't work out how low subgrade strength can mean no limit on the tyre pressure - I would have thought a high subgrade strength would be needed.
If >PCN = >runway strength I wonder why New Plymouth's is so high, compared to Napier and Nelson. (Hamilton and Palmerston North which both take 737s regularly to/from Australia, are PCN 39 and 35, respectively).
Where does maximum tyre pressure come into the equation?

For all airports, ASDA is the same as the runway length, unless otherwise noted.

I'm wondering why Hokitika, with similar data to Napier is not certificated and Napier is, and what Hokitika's runway would need to have done to it, in order for larger aircraft to fly in.

When I ask maximum aircraft size to each airport - I mean fully loaded with passengers and baggage. Full fuel would probably not be required as by far the vast majority of flights within New Zealand are under 400 nautical miles.

I am thinking max for all the non-certificated ones apart from Whenuapai would be a Beech 1900 or a Metroliner... for Nelson/Napier/New Plymouth.... perhaps an ATR-72? Air New Zealand did operate 737-200s to Napier for a few years but they were weight restricted and the service was uneconomic.
But I might be wrong (re BEHs and AT7s), and if I am right, I don't know why I'm right!!!

How big is an aircraft that weighs 5700kg at MCTOW? Are we talking Piper Navajo size? When it says they must turn in the turning bays, is that because the turning bays can take greater weight as well as having more pavement available to turn on, or is it just that the runway is too narrow for a turn to be done?

All airports are below 150ft elevation, and are in a temperate climate - average daytime temperatures generally not above 25C (77F ) or below 10C (50F).
New Plymouth has notorious crosswinds, and Whenuapai has high terrain nearby.


Anyway, here is the data:


Napier: (Certificated)

PCN 22
Flexible Pavement
Medium Subgrade Strength
Medium tyre pressure - maximum 1500kPa
Aircraft experience has proven the pavement strength to be adequate.

1310 x 45m Bitumen (4298 x 148ft).


Nelson: (Certificated)

PCN 19
Flexible Pavement
Medium Subgrade Strength
Medium tyre pressure - max 1500 kPa
Technical evaluation completed.

1347 x 45m Bitumen (4419 x 148ft)


New Plymouth: (Certificated)

PCN 45
Flexible Pavement
Low subgrade strength
Low tyre pressure - max 1000 kPa
Technical evaluation completed.

1310 x 45m Bitumen (4298 x 148ft).
(NB: as a bit of trivia, New Plymouth's runway also slopes up 0.35 from thresholds to centre, making seeing other aeroplanes during take-off and ground manouvres difficult!)


Westport: (Certificated)

LCN 35 H=30

1280 x 30m - with turning bays so 45m wide at threshold. (4199 x 98ft).


Whakatane (non-certificated)

PCN 17 (ACN 23 acceptable infrequently, max tyre pressure 500kpA)
Flexible Pavement
High subgrade strength
Low maximum tyre pressure - 1000 kPa
Technical evaluation completed.

1280 x 30.5m (4199 x 100ft).

Aircraft 5700kg and over MCTOW must do U turns in turning bays at runway ends.

Hokitika (non certificated)

PCN 20
Flexible Pavement
High subgrade strength
Medium tyre pressure - max pressure 1500kPa
Technical evaluation has been done.

1314 x 30m (4311 x 98ft).

Aircraft 5700kg and over MCTOW must do U turns in turning bays at runway ends.


Whenuapai (non-Certificated). Military Aerodrome.

Royal New Zealand Airforce Base, and from 1946-66, Auckland International Airport. Unlike all the airports above with one runway each, Whenuapai has two (three on the map, but one had to be closed). When 12/30 was open, only 818m of its 1446m could be used - I suspect due to deterioration in the runway surface. 1346-1365m of runway 03/21 is usable for takeoffs and landings, while it's ASDA is 2031m! AND I do not see any displaced thresholds on the aerodrome chart.

03/21

PCN 40
Rigid Pavement
Ultra low subgrade strength
High maximum tyre pressure - no limit.
Aircraft experience has proven the pavement strength to be adequate.
(In this case (!) to the last point - if it had more frequent operations I doubt it would be.)

2031 x 45m Bitumen (6663 x 148ft).


08/26

PCN 36
Rigid Pavement
Ultra low subgrade strength
High maximum tyre pressure - no limit.
Aircraft experience has proven the pavement strength to be adequate.
(As above, for this last point.)

1581 x 45m Concrete (5187 x 148ft).

The RNZAF operate Orions, Hercules, and 757s from Whenuapai, but of course, the frequency is not the same as that of a civilian airport.
There is some controversy over Whenuapai at present - the runways are in poor shape, and the concrete pads laid to stop the runways cracking up if they were bombed are starting to separate. Waitakere City Council hopes to convert the place into Auckland International Airport Mk II and attract a host of LCCs when the RNZAF base closes in a few years time - and if it gets its way, it will try. But what will it have to do, to get the runways up to scratch?

(PS: If you are wondering if New Zealand's runways are on the short side, yes they are - 2 aerodromes in the country (AKL + CHC) have runways over 3000m/9842ft, and they have one each.)

Thanks for any help on all these questions - they've been simmering in the back of my head for a while!


MDZWTA ~ Mobile Disaster Zone When Travelling Abroad
6 replies: All unread, jump to last
 
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 1, posted (8 years 4 months 3 weeks 2 days 19 hours ago) and read 9977 times:
AIRLINERS.NET CREW
DATABASE EDITOR




Quoting NZ8800 (Thread starter):
all these questions - they've been simmering in the back of my head for a while!

Bloody hell....all of that? I recommend very powerful drugs.

 Wink




2H4





Intentionally Left Blank
User currently offlineMandala499 From Indonesia, joined Aug 2001, 6957 posts, RR: 76
Reply 2, posted (8 years 4 months 3 weeks 2 days 2 hours ago) and read 9956 times:

Sorry, I'm rather confused about the questions because it got trodded allover by the examples of PCNs in NZ... and it wasn't simply worded... ANYWAYS...

PCN = Pavement Classification Number...

## A/B/C/D

## = Strength grade.
A = Surface type. F = Flexible (Asphalt, FlexCon, etc), R = Rigid (concrete usually)
B = Subgrade (A = High, B = Medium, C = Low, D = Very Low)
C = Max Tyre pressure. Usually W,X,Y,Z
D = Method of determining the Strength grade. T= Tests, U = Usage experience.

To learn why the classification is structured as such, I suggest you look at Boeing Airport Compatibility files of say, the 737-200 or 733/4/5 aircraft (yes, it'll give a better picture than the NGs IMHO), and see what kind of PCN examples will give you what kind of restriction as to your aircraft weight and tyre pressure operating in and out of a particular airport. I found this to be the best way to figure it out.

When you combine this with the sections on performance, you'll begin to see the viability of one aircraft comparing with another in terms of revenue potential when operating a route...

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineZeke From Hong Kong, joined Dec 2006, 9210 posts, RR: 76
Reply 3, posted (8 years 4 months 3 weeks 1 day 7 hours ago) and read 9934 times:

Posted this before in RE: What's The Biggest Jet Can Takeoff In 2700m Runway (by Zeke Mar 12 2006 in Tech Ops)


PCN 40 - The Pavement Classification Number: The reported PCN indicates that an aircraft with an ACN equal to or less than the reported PCN can operate on the pavement subject to any limitation on the tire pressure.
F-The type of pavement:R - Rigid, F - Flexible
C-The subgrade strength category: A - High, B - Medium, C - Low, D - Ultra-low
Y-The tire pressure category: W - High, no pressure limit, X - Medium, limited to 1.50MPa (218psi), Y - Low, limited to 1.0MPa (145psi), Z - Very low, limited to 0.50MPa (73psi)
T-Pavement calculation method: T - Technical evaluation, U - Using aircraft experience

Transport Canada has some good gen on this, for example http://www.tc.gc.ca/CivilAviation/International/Technical/Images/ACN_Table.jpg

Further information http://www.tc.gc.ca/CivilAviation/In...Pavement/management/operations.htm

You can download the ACN for most aircraft for free http://www.tc.gc.ca/CivilAviation/In...Pavement/Downloads/ACN_Table_e.pdf



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineNZ8800 From New Zealand, joined May 2006, 425 posts, RR: 2
Reply 4, posted (8 years 4 months 3 weeks 18 hours ago) and read 9920 times:

Thanks for the replies  Smile
I PM'd a pilot re: certification and he kindly reminded me that there is more to it than having a runway strong enough to land the larger aeroplane on, important though that is!

It sounds like we could not fly even a fully loaded Fokker 70 into Nelson or Napier then - or a DC9, even if their runways were longer.

Yet New Plymouth, if it's runway were longer (and the demand was there!) could take a fully loaded A320 - if they're able to lower the tyre pressure a little. Is that able to be done - or too dangerous?
I'm still wondering why NPL has such a high PCN when the runway is so short.

Pretty sure Dash8-400s might be considered for NPL in the next few years - but as the tyre pressure is well over what the runway can take, I wonder what they'll do to fix it - lower operating weight of the aircraft, maybe?



MDZWTA ~ Mobile Disaster Zone When Travelling Abroad
User currently offlineMandala499 From Indonesia, joined Aug 2001, 6957 posts, RR: 76
Reply 5, posted (8 years 4 months 3 weeks 7 hours ago) and read 9904 times:

NPL has a high PCN number, but low subgrade... Net effect, low weights only...

But I gotta check the charts again to see what can go on it...

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineZkpilot From New Zealand, joined Mar 2006, 4844 posts, RR: 9
Reply 6, posted (8 years 4 months 3 weeks 6 hours ago) and read 9897 times:

Quoting NZ8800 (Reply 4):
I PM'd a pilot re: certification and he kindly reminded me that there is more to it than having a runway strong enough to land the larger aeroplane on, important though that is!

pleased to be of assistance  Wink

I think Mandala and Zeke covered off the rest of it pretty well however.  Smile

more specifically (from an old IFG btw) NPL was:

Rwy...SFC...Strength...Gp...Slope...ASDA...T/O dist 1:62.5...LDG dist
05......B......PCN 45.....8.....0.35Di...1310.....1371............1310
23.............F/C/Y/T............0.35Ui
i) RWY 05/23 slopes up from thresholds to centre.



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