EDI 06/24 74/R/C/W/T Grooved Asphalt
Parallel taxiway 06/24: Width: 23 m. Surface: Asphalt Strength: 74/R/C/W/T
Terminal Stands: Surface: Concrete Strength: 72/R/C/W/T
My interpretation is that the runway has an asphalt overlay, on top of a concrete (rigid) pavement. If I sharpen the pencil and calculate deeply, the weight limit is closer to 605,000 lb or 274.4 t (rather than 610,000 lbs).
In response to earlier questions, no tyre pressure reduction is done on these or most aircraft nowadays – it dropped out of fashion as an option after the 1980's once the old runways built for propeller aircraft had been all been strengthened.
That pavement rating at EDI 06/24 is good enough for fully laden Boeing 747-400 territory. Gee guys – that's pretty generous already. Running a Boeing 747 off that short 2556m long runway is almost over-servicing the airport.
The
AN124 with its 100+ tonnes payload – well the ACN is 73 at maximum takeoff weight, so no concession was needed (the Russians build very pavement-friendly aircraft).
Overload guidance CAP 168 gives:
12.4.1 Individual aerodrome authorities are free to decide their own criteria for permitting overload operations as long as pavements remain safe for use by aircraft. The PCN value does include a safety factor so that a 10% increase of ACN over PCN is generally acceptable for pavements that are well consolidated and in good condition.
I have an unreferenced guide, purportedly about UK practice, that an overload by an aircraft with an ACN of more than 10 percent but not exceeding 25 percent of the reported PCN requires regular inspections of the pavement by a competent person and there should be an immediate curtailment of such overload operations as soon as distress becomes evident. [It doesn't say so directly, but only a few operations would be permitted at this level]. An overload by aircraft with an ACN great than 25 percent but not exceeding 50 percent of the reported ACN may be undertaken under special circumstances including scrutiny of available pavement construction records and test data by a qualified pavement engineer; and a thorough inspection by a pavement. [It doesn't say so directly, but this is more the one-off event]. This is a very reasonable approach to overloads, and I use that myself (even if I can't find the reference).
Having said all that, the 777-300ER (and A340-600) are particularly nasty beasts in terms of pavement loading, and they do damage seemingly disproportionate to their size. There is a growing body of opinion that for these particular aircraft, all manner of concessions need to be rethought, limited or withdrawn (including even the various equivalencies in pavement thicknesses). So discussions about permitting overloads for the 777-300ER should be appropriately constrained, and only very small overloads permitted.
As an aside, but I'm not going to let this one get past unmentioned because of the many frustrations it has caused me in the past, as tom775257 noted earlier:
places like Corfu and Zakinthos, they aren't man enough for an A321 WRT PCN, but still we operate into them with an A321.
Ah, Greek Airports. The finest overload that money can buy.
Cost to upgrade Edinburgh The EDI pavement PCN rating has been done on a technical basis (the "T" in the rating), so I'm guessing the EDI probably have a reasonable idea of what is needed and the cost. I can give a ballpark estimate, but it is very much subject to adjustment based on the actual pavement. To move the runway rating for the 777-300ER from 274.4 tonnes to 352.2 tonnes, simplistically needs another 200mm of asphalt. The runway, parallel taxiway, stub taxiways and some of the apron all need to be overlaid. The cost will be loaded for (a) night work, constructing in limited hours to MOWP, temporary ramps and grooving, etc; (b) many runway lighting changes and re-cabling, matching in the geometric levels at all shoulders and all intersections, new markings; and (c) compliance with noise, environmental, and all manner of constraints.
I'm guessing that the whole project might run to GBP150 per tonne of laid asphalt. That would put the project at about GBP 15 million. However these projects can take on a life of their own (especially some of the UK ones I've seen), so figures going skywards up to GBP 50 million could be thrown around.
Cheers
Overrun