I was watching a video and realised that this airport operates both grass and paved runways. What would the benefit of grass versus hardened runways?
On the plus side, for the airport operator, grass runways are (obviously) much cheaper when you price out the cost of pavement. A lawn is cheaper to build than a paved parking lot. An airport operator can have the luxury of much wider runways. You do have to do work to control drainage to be able to operate in spring and control water flow during storms etc, but still way cheaper than asphalt.
For the airplane owner, the main benefits of grass are tire wear, and propeller damage. Propellers pick up lots of fine stones even on what looks like smooth pavement. Doing runups and starting takoff on grass just about eliminates prop dings.
If you're flying taildraggers, the lower traction of grass makes the airplane much less twitchy in its attempts to switch ends while rolling (like pushing a shopping cart backwards). Taildragger pilots who learn and become proficient with ground handling on grass often almost go back to square one the first time they land on a paved runway.
The main downside of grass other, than the massive lawn care task, and limitations on surface load bearing ability that varies with the moisture content and composition of the soil, is inaccessibility during spring thaw (better or worse, depending on how well drained it is), and very poor traction and braking when it's wet. Wet grass is not unlike operating from hard compacted snow.
3$\begingroup$ I suggest to add the possibility to take off in any direction. Early airports were round for exactly that reason, and paving a large round area is out of the question. The faster speeds of modern planes made this less attractive, though. $\endgroup$ Dec 7, 2022 at 8:03
1$\begingroup$ But the question is mostly a practical one about modern airports and omnidirectional grass strips are unheard of nowadays. However, overall surface area is a practical consideration and I'll add something about that. $\endgroup$– John KDec 7, 2022 at 13:22
1$\begingroup$ In the Northern US and Canada with the freeze/thaw annual cycles, a grass field is severely limiting and may force a flying school to close down for most of April and May. If there is a commercial operation, they will almost certainly find a way to pay for paving at least one runway. If a grass field is really busy, mud becomes a problem as well. $\endgroup$– John KDec 7, 2022 at 20:12
There are various reasons to have grass runways, one note to put this in context, at one point in history all runways were grass/unpaved in some capacity so some of this is a legacy thing. A few reasons
- Allowing for cross wind landings without a second paved surface (e.g. KCRS)
- Practice for people who want to go to and from smaller grass-only strips elsewhere
- Some pilots just like flying their old piper cubs from grass
- Maintaining pavement can be expensive
- Soft field landings are still on the ACS so why not...
- Your weird uncle can build one
- They are kept as they are for environmental reasons
$\begingroup$ Other than requiring a second oversized bag of money that can't entirely be replaced with sweat equity, is there anything that would stop the weird uncle from being able to build a paved runway instead? $\endgroup$ Dec 6, 2022 at 18:44
$\begingroup$ @DanIsFiddlingByFirelight I guess it depends if he can fit the steamroller down his driveway. That aside there is no regulatory prohibition against it, plenty of private airports have paved strips that are build by the owners. The FAA does not much care about it unless you go to have it charted or want to put an official procedure into it etc. $\endgroup$– DaveDec 6, 2022 at 18:54
1$\begingroup$ As an Air Training Cadet, I did some gliding at RAF Benson (Oxford, UK), where they have a grass strip with a static glider tow winch. I was told that the strip was held ready to be used as a diversionary landing for heavy aircraft with failed undercarriages, mainly because grass minimises fire risk. $\endgroup$ Dec 6, 2022 at 21:53
2$\begingroup$ +1 just for the weird uncle link, but all the rest is also fine. $\endgroup$ Dec 7, 2022 at 17:50
Depending on the location, grass runways count as "green space" for the purposes of carbon credits. So do the Runway End Safety Areas.
Airports/clubs have a significant carbon cost, so financially anything that helps offset pollution taxes helps.
Yes, this is definitely a minor reason, but accountants will use whatever loopholes they can, and a grass runway of 500mx20m is 10k square metres of land or ~20 domestic sections.
I have near 400 hours of conventional gear (tail wheel) time and love to fly them off grass runways since the tail wheel/grass combination is much more forgiving. As noted above, the tires hook up with a paved surface more positively and therefore takeoffs, and even more so, landings require much more concentration. Downside of grass is that a good grass runway requires a lot of attention to stay that way. Correct and frequent mowing, fertilization, and over seeding needs to be done every year. Even the type of tires on the lawn equipment influences the quality of the surface. Lastly, keep street vehicles OFF THE GRASS!