This picks up from here
What size runway? If we could make our currently “ok” grass runway “very good” for 30k, it is likely that we would.
About 10 years ago, when Shoreham was going bust (yet again) I looked closely at a project which would be 750m x 25m.
The first stage is to level the surface, which may involve ploughing, rolling and seeding. Then mole-draining it, which is drilling holes underneath which drain into a ditch. The ditch can be left open (usually it is, because it’s cheaper, and grass strips are mostly all about being as cheap as possible) or you can cover it with slabs, or it can be constructed with a big pipe which is then buried (the last two options are good if somebody goes off the runway). Obviously that ditch has to slope appropriately and at the end you have to drain it, which may involve a mains powered pump with a level switch. That will give you a very nice runway, provided you look after it, which means no twins and no ops for a few days after it gets soaked. The strips which are unusable for months (the majority) are thus because they are not drained, and/or are mismanaged.
There goes about 30k.
The next stage, which is normally done covertly because it is provocative to the “there will be 747s flying in here” local idiot brigade, is to reinforce the surface with the interlocked green (obviously green) plastic matting. This is proper stuff, about 3cm thick, and a specialist installs it. It is rolled into the ground. Very few strips have done this and rather more use it on taxi areas which otherwise get damaged quickest. People who have done this won’t discuss it on forums, obviously.
I got an estimate from the firm exhibiting at EDNY for about GBP 80k, 2 years ago.
Incidentally I was also intending to get full planning permission, from Day 1. The estimate, up to an appeal through the various steps all the way to the Department of the Environment, would be budgeted at 100k. Obviously if in the UK you are fairly remote then there is the 28 day rule which is adequate provided you keep visitors out as far as possible!
Seems expensive but you would end up with a TBM700-grade facility.
However we have many grass flyers here and I am sure others can fill in more detail from actual scenarios.
My gliding club airfield is on top a limestone plateau with very little soil. That mainly sorts the drainage for you. A few area have been filled-up and get boggy in the winter. Wheel brake application needs to be gentle in the winter.
Maintenance is a lot of mowing, some strategically-timed rolling (ground not too soft nor too hard) and repairing damage from the badgers or landings with too much brake.
Can’t you talk to DEFRA, they will sort the badgers out.
Very few strips have done this and rather more use it on taxi areas which otherwise get damaged quickest. People who have done this won’t discuss it on forums, obviously.
I know two, Speck and Buttwil, which have them.
I did land on the runway at Speck in winter time with a runway condition they limited to one arrival and one departure. It was ok, but braking action was close to zero. Together with the mud however, stopping was no problem.
The main problem however was the amount of dirt after landing. The whole underside, gear wells, gear doors, elevators e.t.c. looked like a motorcycle after a cross race. As I went there for maintenance, they took care of it and we coose a slightly dryer day for redeparture.
To own a place like this, either have an airplane which really likes grass (like an AN2, Pilatus Porter or similar) or go for concrete in the beginning. The major hassle with grass definitly is the fact that despite the plastic stuff it is usable for 1/3rd to 3/4 of the time, depending on where you live. In our rain-sogged climate, they are next to useless.
That’s interesting. I wonder if it means that the plastic matting merely prevents ruts forming, but does nothing to stop the ground turning into mud if it is wet.
How would plastic stop the ground turning to mud? As long as earth is exposed to moisture it will turn into mud. This is a well known problem even for PSP runways.
What is PSP?
One approach would be to not have any soil above the upper surface of the plastic. Only blades of grass.
I wonder if it means that the plastic matting merely prevents ruts forming, but does nothing to stop the ground turning into mud if it is wet.
What it does is to give a stable underground. You won’t have the planes sink in or have deep traces dug by wheels. What covers it will still turn into mud or rather soapy underground in rainy weather. But of course by the time the top layer has dried out it is well ready to be used again, unlike untreated surfaces which can stay unusable for weeks.
If I had to work with a runway like that, this is one way to make it a lot more durable.
I’ve been involved in the creation/improvement of half a dozen runways over the past five years. Drainage is the most critical aspect. Some just required mowing to define the strip, but can be soft in winter. Another needed 10,000 tonnes of rock to be excavated and re-distributed, but that resulted in a true all-weather facility.
The worst case would be a flat field on clay subsoil, like some Kentish airfields. Then you need to mole plough and install a lot of field drains.
It’s worth talking to a seed merchant about grass varieties, the object being minimum leaf growth with maximum self-repairing by rhisomes.