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?

  • 1
    $\begingroup$ Possible duplicate of How are runways numbered? $\endgroup$
    – GdD
    Commented May 17, 2018 at 7:33
  • 8
    $\begingroup$ @GdD I don't agree on the duplicate, there is no mention of any "G" in that linked question/answers. $\endgroup$
    – Federico
    Commented May 17, 2018 at 9:05
  • 2
    $\begingroup$ @GdD ok, missed it. I'm evaluating editing to make it a bit more prominent, now it is really buried and hidden. $\endgroup$
    – Federico
    Commented May 17, 2018 at 9:09
  • 12
    $\begingroup$ @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. $\endgroup$
    – Notts90
    Commented May 17, 2018 at 13:30
  • 2
    $\begingroup$ 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. $\endgroup$
    – user
    Commented May 17, 2018 at 17:17

2 Answers 2


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.

  • 12
    $\begingroup$ Such as 21W in Manhattan. Once, USAir served it. $\endgroup$ Commented May 18, 2018 at 5:34
  • 5
    $\begingroup$ 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. $\endgroup$
    – PlaneGuy
    Commented May 18, 2018 at 21:16
  • $\begingroup$ 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! $\endgroup$
    – Cort Ammon
    Commented May 19, 2018 at 4:24
  • $\begingroup$ @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. $\endgroup$
    – user
    Commented May 19, 2018 at 8:13

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
Gradient: W
Operational restrictions: RWY 08G/26G LNDG AREA UNDEFINED.
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

  • 6
    $\begingroup$ Welcome to Aviation.SE! Nice answer. We hope to continue seeing you around providing more of them! $\endgroup$
    – reirab
    Commented May 18, 2018 at 18:52

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .