How can a surface created with asphalt be considered "Rigid" and not "Flexible"? Isn't concrete that is rigid and asphalt that is flexible? This was also stated in the answer to another question. I also share the sample image for understanding. However, such a table is given on the Turkey AIP AIRCRAFT PARKING/DOCKING CHART (AD 2 LTAF PRKG-1). Shouldn't the letter in the first digit of the series given for the apron D, which is asphalt here, be "F" instead of "R"?

enter image description here ---> This text was taken from the answer to the question at this link: https://aviation.stackexchange.com/a/33444/65367

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2 Answers 2


I would change that definition as "Asphalt is usually a flexible surface, Concrete is usually a rigid surface".

I do not have specific knowledge of that airport, but it may be that the surface is a composite asphalt+concrete:

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In such case, the upper layer is asphalt, and this is why the indication in the chart is probably Asphalt (this is a my guess).

A composite material may be rigid or flexible depending on the ratio between asphalt and concrete used:

The choice of the pavement type, i.e. rigid (R) of flexible (F), should be based on the chart used for the evaluation.

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Source: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/552405/DMG_27.pdf


It is possible that either the surface type or PCN classification for this particular apron is either incorrect or out of date. While this is not the usual thing that you would first suspect when viewing an official aviation document, I think it might be plausible in this case if we put this particular piece of pavement into perspective.

The apron being discussed is at Adana Sakirpasa Airport (ADA, LTAF) in the city of Adana in southern Turkey. Opened in 1937, Adana Airport is Turkey's oldest commercial airport and its sixth largest. The airport is located in the middle of developed areas of the city, and is expected to operate only until the completion of the Cukurova Regional Airport located 20 km outside of the city, which is currently scheduled to open sometime in 2023, although the project seems to have been delayed.

The two pavements being compared, Apron A and Apron D, can be seen in Google Maps satellite view.

Adana airport Adana Airport (source: Google Maps, imagery: CNES/Airbus, Landsat / Copernicus, Maxar Technologies)

Apron A is located at the passenger terminals, and looking at some random online photos it appears to see mostly 737 and A320 sized airliners. Although the terminal gates can handle aircraft up to A300 (and even 747!), as seen in the DHMI (Turkish Airport Authority) document which also contains the PCN information shown in the question.

LTAF Parking LTAF Parking Diagram (source: www.dhmi.gov.tr)

The comparatively tiny Apron D, which is in question because of its confusing surface type designation in the DHMI documents, appears to be sized to hold a small number of general aviation aircraft. Looking at a close-up satellite view it appears that the east section of Apron D can handle up to eight small aircraft, similar in size to the five aircraft seen parked there in the satellite photo, which seems to include a small twin-engine plane.

Apron D Apron D (source: Google Maps, imagery: CNES/Airbus, Landsat / Copernicus, Maxar Technologies)

Meanwhile it appears that a hangar has been built on the west section of Apron D. Although it can be noted that the DHMI document still shows eight parking spots in that section, the markings for four of them can still be seen in the photo.

The lack of any apparent facilities at Apron D would seem to indicate that this apron is mainly used for longer term small aircraft storage. A larger general aviation apron with facilities, Apron C, is located on the north side of the airport next to Apron D which is a military apron.

Another DHMI document for Adana Airport lists surface information for all of the taxiways and aprons.

Pavement information LTAF Apron, Taxiway Information (source: www.dhmi.gov.tr)

This document appears to be current as of January 2023.

It can be noted that all of the taxiways are listed as asphalt except for A1 and E, which go to aprons B and C respectively. Apron D is the only apron listed as asphalt on the document. It can also be noted that Apron D has the exact same PCN values as Apron A, with the only difference being that the surface for Apron D is listed as asphalt. This could be an indication that either the surface type or PCN values listed for Apron D is incorrect or out of date.

It can also be noted that while Wikipedia lists the Adana Airport runway as asphalt, the DAFIF (Digital Aeronautical Flight Information File) information that Wikipedia references was current only as of 2006, which is when DAFIF stopped being available publicly. An unofficial source which appears to be current as of 2016 shows the Adana runway as being composite, a surface type mentioned in another answer.

Looking at all of this in context, it seems possible that since Apron D seems to be used by only a small number of small plane owners, that any errors or inconsistencies as far as surface type classification in the DHMI documents have likely gone unnoticed, or ignored. Especially considering that the Adana airport is expected to close in the relatively near future.

  • $\begingroup$ First of all, thank you very much for your detailed answer. However, while the shared documents are created and made available by authorized professionals, I do not understand the idea of not correcting the errors and republishing them in the same way. It shouldn't be too difficult to correct something that is known and publish it. As you know, aviation is a serious business and everything must be carried out meticulously. Even if your answer is correct, my inner self cannot accept this ignoring. Thanks again for the answer.. $\endgroup$
    – pilot162
    Sep 8, 2023 at 7:41
  • $\begingroup$ In general I agree, most things on aviation charts can have important implications. Considering how heavy many airplanes are, surface strength is important for the safety of the aircraft using the surfaces. But primarily it's important for the service life of the pavements. Airplanes too heavy for a particular surface will cause it to wear prematurely and/or require more frequent repairs. In this case however this is a tiny apron used to park a few small lightweight planes for storage. There is little chance that anyone even looks at the PCN numbers on the documents for this particular apron. $\endgroup$ Sep 8, 2023 at 12:33
  • $\begingroup$ I have to look at these charts because I fly the small planes in the image you get from Google Maps :) Anyway, as you said, the authorities who prepared the chart may not pay much attention to it. $\endgroup$
    – pilot162
    Sep 8, 2023 at 13:11
  • $\begingroup$ Not sure if you interpreted my comment to mean that no one looks at the charts. I was only referring to the surface classification for Apron D. If you were flying into LTAF in a small plane you would likely not be looking at surface classifications on the charts other than maybe to see if they are paved or not. PCN is important for larger planes, but it's doubtful that anyone flying into LTAF will be directed to park in Apron D, the people who park there probably have leases. I doubt any of them care if it was not classified correctly on the chart, or worry whether the PCN numbers are correct. $\endgroup$ Sep 8, 2023 at 13:43

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