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Boulder Municipal Airport (KBDU) has runways 8 / 26 and also runways 8G / 26G. What is the significance of the letter G following the runway numbers?

slantalpha
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    Possible duplicate of How are runways numbered? – GdD May 17 '18 at 07:33
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    @GdD I don't agree on the duplicate, there is no mention of any "G" in that linked question/answers. – Federico May 17 '18 at 09:05
  • It is in there @Federico, look at Airhead's answer. – GdD May 17 '18 at 09:06
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    @GdD ok, missed it. I'm evaluating editing to make it a bit more prominent, now it is really buried and hidden. – Federico May 17 '18 at 09:09
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    @GdD one paragraph in the 4th answer hardly makes it a dupe. SE is supposed to make it easy to find the right answer, not a puzzle. – Notts90 May 17 '18 at 13:30
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    I marked it as a duplicate because it had comprehensive information on runway numbering, and included an answer to the OP's question, but I'm happy to go with the community on this one. – GdD May 17 '18 at 13:47
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    For completeness' sake: This looks like a US-ism. As counterexamples, my Swedish airport directory lists for example Karlskoga ESKK with a 1499 x 30 m asphalt runway and a 900 x 40 m grass runway, both designated 03/21; or Gävle ESSK with a 2000 x 45 m asphalt runway and a 730 x 30 m grass runway, both 18/36. Not even any R/L designators with either of these; just two different, parallell runways with different surface characteristics and the same designations. – user May 17 '18 at 17:17
  • @MichaelKjörling That sounds crazy. I could understand using L/R, but using the same designator for two different runways at the same airport sounds crazy. Seems like it could lead to errors, especially in IMC and/or at night where it's not easy to see the difference between surface types from a distance. – reirab May 18 '18 at 18:45
  • @reirab I could be wrong, but I very strongly suspect that few grass strips (at least around here) are used in practice in IMC or at night, so the issue may be mostly academic. My local airport has three parallell landing/takeoff areas; one asphalt runway with one grass strip on each side of it, all technically known as 04/22. The distinction is made by specifying e.g. "runway 22" or "eastern strip 04" or "western strip 22". Maybe "22C" or "04R" or "22L" would be clearer for outsiders, but given that the airport doesn't even have the equipment to support instrument approaches... – user May 18 '18 at 20:19
  • @MichaelKjörling Oh, I agree that someone wouldn't likely intentionally be using a grass strip in IMC. My concern was more for unintentionally lining up on the grass when the asphalt was intended if they had the same runway designation (e.g. accidentally selecting the wrong one in a GPS system or similar.) – reirab May 18 '18 at 21:49
  • @reirab -- the grass strips wouldn't be programmed into GPS or FMS databases to begin with, though (as they aren't instrument runways at all) – UnrecognizedFallingObject May 19 '18 at 12:57

2 Answers2

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For runways with other than hard surfaces it is common to list the runways with a letter G for grass or in the case of a seaplane base, with W for water.

An example of this is runway 8G at Boulder (KBDU) and runway 35W at David Wayne Hooks (KDWH).

You can see this information in the Chart Supplement pages and diagrams for each airport.

Pugz
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    Such as 21W in Manhattan. Once, USAir served it. – Harper - Reinstate Monica May 18 '18 at 05:34
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    This answer is not technically correct, the surface type of the runway is not indicated in the designation. It is a coincidence that "W" type runways are water, the suffix indicates type of runway not surface type. S = STOL runway, G = glider runway, W = water sealane or waterway, and U = ultralight runway. I would have commented sooner but I needed to build up some reputation, so I made my own answer. – PlaneGuy May 18 '18 at 21:16
  • For a moment, when reading this, I thought you cited a suffix that meant that the runway had boulders. Took me a moment to realize my mistake, but it did lead me to think up some really amusing airports before I realized it! – Cort Ammon May 19 '18 at 04:24
  • @Harper I suspect they quickly realized that it would be difficult to turn a profit on that particular one. Also, I imagine the landing fees were kind of stiff in the end. – user May 19 '18 at 08:13
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The "G" suffix refers to a Glider runway.

The following verbiage is used in Advisory Circular: AC No: 150/5200-35 Page 15 RUNWAY IDENT

"The following suffixes can be used in conjunction with runway identification numbers even if the runway is not painted accordingly: S = STOL runway, G = glider runway, W = water sealane or waterway, and U = ultralight runway"

Interestingly runway 8G / 26G is actually a dual surface runway with part of it being paved and the remainder grass.

The following is the description of that runway: Found here AirNav: KBDU

Runway 8G/26G Dimensions: 4100 x 20 ft. / 1250 x 6 m
Surface: asphalt/turf, in fair condition
RWY 08G/26G 3,000X20 FT CHIP AND SEAL ON WEST END; EAST 1,100 FT IS GRASS.
Gradient: W
Operational restrictions: RWY 08G/26G LNDG AREA UNDEFINED.
RUNWAY 8G RUNWAY 26G
Latitude: 40-02.378333N 40-02.378333N
Longitude: 105-14.001500W 105-13.122833W
Elevation: 5287.0 ft. 5274.0 ft.
Gradient: 0.3% UP
Traffic pattern: left right
Obstructions: 60 ft. trees, 200 ft. from runway, 126 ft. left of centerline, 3:1 slope to clear none

fooot
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PlaneGuy
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    Welcome to Aviation.SE! Nice answer. We hope to continue seeing you around providing more of them! – reirab May 18 '18 at 18:52