Frustrations of a Grass Runway... [Archive]

tiggermoth

16th Dec 2006, 22:21

I woke up this morning to a blue sky with a few clouds just minding their own business, checked the wind, not even windy enough to be worth putting the washing on the line... so off I tootled to the local grass strip (Barton). Good day for flying.

"Oh here we go, the optimist" I was greeted with (big smiles) "Have you got your water wings?"

The runway (aka 'Rugby Pitch') was waterlogged. No flying. Aerodrome closed. Probably a good day to dig up worms, but not much else.

Back I jumped in the car, headed for home, and bought a couple of Christmas presents on th eway home instead.

Frustrations of a grass runway...

tiggermoth

16th Dec 2006, 22:58

Ah yes, it's mud covered with a thin green coating :bored:

Genghis the Engineer

17th Dec 2006, 05:46

IO540

17th Dec 2006, 06:58

Out of interest, does this kind of work, and especially digging ditches, affect the use under the 28-day rule, or does it make getting full planning harder?

From what I have read, the local authority prefers runways to be unusable much of the year, which is one reason hard runways are resisted so much even if the # of movements sought isn't increasing.

Genghis the Engineer

17th Dec 2006, 09:46

tonyhalsall

17th Dec 2006, 10:26

Should be unnecessary.
There are plenty of grass runways around the country which operate every day of the year. But it takes care, drainage, spiking, reinforcing of the dodgier bits, rolling, clover mix...
And occasionally banning touch-and-goes when the runway is wet.
A lot of work, which needs to be continuous and takes several years to make an impact. But if you want continuous use of a grass runway in the UK, necessary.
G

I am not sure that it is the grass which is the problem - more what is underneath.
The last ice age is the culprit for the whole of Northern England having an almost impermeable boulder clay sub surface which traps water in a thin layer of grass and topsoil. Further south where the ice didn't reach you still have the natural subsurface of chalk and surface water very quickly dissipates away. Effective draining of a grass runway which is on top of clay would probably be hugely expensive.

Genghis the Engineer

17th Dec 2006, 14:22

I am not sure that it is the grass which is the problem - more what is underneath.
The last ice age is the culprit for the whole of Northern England having an almost impermeable boulder clay sub surface which traps water in a thin layer of grass and topsoil. Further south where the ice didn't reach you still have the natural subsurface of chalk and surface water very quickly dissipates away. Effective draining of a grass runway which is on top of clay would probably be hugely expensive.

I don't think it's that clearcut.

Down my way, for example, we have for example Compton Abbas (top of a chalk hill, regular quagmire), Popham (used to be an utter quagmire until they started re-inforcing and spiking, now useable throughout the year, albeit with an occasional caution and touch-and-go ban), White Waltham (heavily used, slippery but never quite unusable), Redlands (I've sunk a nosewheel to the cowling) or Chilbolton (built by the RAF originally, very well drained, lots of clover permanently useable - albeit with much less use than the others).

So, yes what's underneath should definitely make a difference, but I think that treatment can still make huge differences.

G

Lucy Lastic

17th Dec 2006, 14:51

I was going to try for Compton Abbas, but didn't fancy washing more of its mud off afterwards.

Whilst I like the airfield and the people, the runway state isn't the best, especially after a long wet period

FullyFlapped

17th Dec 2006, 16:32

Can't you lay some sort of "mesh" on grass which makes it usable in wet conditions ? Sure I've seen something advertised in one of the mags - some sort of plastic matting with hexagonal-shaped holes ?

Or perhaps I just need more medication, nurse ?

FF :ok:

shortstripper

18th Dec 2006, 04:39

I flew into Goodwood Saturday and whilst they do a pretty good job of keeping their runways going, I can't understand the inflexibility shown? As I was taxiing to take off, I called up and offered to pull onto the runway where I was (half way between the tower and the hold) to save the grass at the threshold. There was one other on downwind in the circuit and I stated I was STOL ... but no :rolleyes: I was told to taxy to the hold as usual and take off from the bit of grass that is getting increasingly muddy.

Is there a law or something at a licenced field that says everyone must take off from the same bit of runway and make it more and more muddy? :ugh:

IO540, I see no reason that draining a field with an airstrip on a 28 day rule would affect anything. It is good agricultural practice to have good drainage ... a more usable airstrip is just a fringe benifit :ok:

Clay soils are a bugger to drain, but do have the advantage of being "mole" drainable. This is where a bullet shaped lump of metal is pulled through the clay and a "tube" is formed in the clay itself. With mole drains there is no digging up of the runway required and all that is visible afterwards is slots which can be gently rolled down. Of course they have to be orientated with any natural slope, but as long as the slope isn't 90 degrees to the R/W any slight undulation caused wouldn't be a problem.

The above, and any other drainage methods all have to take account of where you are draining the water too as well!

My strip is relatively dry, but there is a nasty wet area between it and my hangar. It wasn't there last year but we've added a new silage clamp and the natural drainage has been effected by that :mad: ... I'll have to leave it to next summer to do anything about it now though :ugh:

SS

742-xx

18th Dec 2006, 05:26

In light of recent 'events' at Barton you would think the often lack of servicibility of the runway(s) could be used as a baraining tool by LAC ?

I have lost count of the ammount of lessons I have lost due to the place being shut at short notice.

Lister Noble

18th Dec 2006, 18:04

Mole draining is excellent value for money although may have to be done every ten years or so,but combined with a rudimentary permanent drainage system would give very good results.
I'm sure there must be high wear resistant,low growth rate,resilient grass species , you could enquire from the Grassland Research bods (if it still exists!)
There are also honeycomb plastic mats that allow the grass to grow through and provide an excellent wear resitant surface in wet conditions.
Unfortunately most of these things require dosh in varying quantities.
Lister:)

IO540

18th Dec 2006, 18:11

How would honeycomb mats affect planning issues?

Presumably they would prevent mole draining?

Much of where I am looking is on clay, so this is interesting.

Abbeville

18th Dec 2006, 18:20

I would appreciate feedback on honeycomb matting too.

Standing by.

Cricket23

18th Dec 2006, 18:51

Redhill suffers badly too in the wet weather, although there is the alternative of landing on the taxiway, although it is a little narrow and is rather bannana shaped! However, it does sharpen up your landing techniques - no more adding a few knots for your granny!

C23

tiggermoth

18th Dec 2006, 18:55

I've enquired with a supplier of this material, and I'm awaiting a quote for supply, suitable for a runway 620 ft by 32 ft. It does come with different loading ratings from Car (occasional use) all the way to Articulated Lorries (regular use). So, just to get an idea, getting a quote suitable for "Car (regular use)".

I suppose we could work out a proper loading for it, but the price should hopefully give us a rough idea of what sort of outlay we're talking about.

Hoping to get the quote tomorrow, so I'll post in on here when I get it.

T.

Monocock

19th Dec 2006, 08:55

I have recently done the same (enquired about re-inforcement).

The company is www.tenax.co.uk

I calculated on their prices that to do a 600x20m grass runway the cost would be......................

Are you sitting down?

£58,500:eek:

Unless my maths ae incorrect this is based on £195 per 20x2m roll.

I'm sure a 20% discount could be negotiated which would make it a far more acceptable £46,800.....

It would be cheaper to put a lake in and buy a Maule with floats

combineharvester

19th Dec 2006, 10:21

It's not just grass airfields that suffer this fate. I used to instruct at sandtoft, which like most of north lincolnshire should by rights be either underwater or marsh land! it only takes a reasonable downpour and the runway had two puddles across the full width (a staggering 18m i may add..;) ) about 18 inches deep in places! In fact the new grass taxiway/unlicenced grass (not in pooleys) is usually far more useable!

Established Localiser

19th Dec 2006, 10:36

5000 landings !!
Cheap at half the price, put the instructors on a bonus per landing !! (no don't !) :ugh:
EL

IO540

19th Dec 2006, 10:49

tonyhalsall

19th Dec 2006, 11:29

What is the drawback of digging a ditch, say 1ft deep, either side of the runway, and having a pump pumping the water out of the ditch to some location say 100m away?

Regarding reinforcement, the place where this is really needed is in the taxiing areas and the part of the runway where one moves slowly. Most planes can get their nosewheel off the ground pretty fast - in the TB20 I can have the nosewheel off after about 100m, even if it needs another 500m after that before one can climb away.

Actually, I am going to suggest this very thing to our farmer. The 'runway' (ha ha) strip already has a down slope and I thought that the most cost effective drainage solution would be to 'ditch' either side of the runway - the only problem with this is that the mown strip itself is only about 3 metres wide so good drainage will be at the price of very accurate future landings or risk of a bent undercarriage

tiggermoth

19th Dec 2006, 13:54

Right, I have a quote back. £4,000 +VAT for a 620 ft by 32 ft runway. It's been stressed to me that this does not include fitting (but it was worth asking...)

That comes on a total of 40 rolls (25m length by 2m wide). So this means we're talking 5 rolls wide, with eight sets of rolls down the length of the runway.

For more details:

Sarah Davies
McArthur Group
01772 556042

(This contact is based in Preston, but they have branches around the country)

T.

tiggermoth

19th Dec 2006, 14:08

I have recently done the same (enquired about re-inforcement).

£58,500:eek:

Unless my maths ae incorrect this is based on £195 per 20x2m roll.

I'm sure a 20% discount could be negotiated which would make it a far more acceptable £46,800.....

It would be cheaper to put a lake in and buy a Maule with floats

I've just looked again at your figures, and I think (correct me if I'm wrong here), if they're 20x2m rolls, then you need 40 of them (I think there's been a feet to metres problem here). So that's 40 x £195, which is a reasonable £7,800.

Both figures are in the same order of magnitude, I can only assume that McArthur has quoted us on the bulk order amount.

IO540

19th Dec 2006, 15:17

That previous price did seem a bit high, since I have recently come across a case where re-tarmacing a 600m+ runway would have cost "only" £60k or so.

tiggermoth

20th Dec 2006, 09:39

I suppose there is a reasonable amount of downtime after preparing a grass runway (or even retarmacing it)?

MikeJ

20th Dec 2006, 13:45

Just picked up on this thread. IO540 is quite right that lifting the nose wheel early in 'sticky' conditions reduces wheel drag. This is not only by not ploughing a furrow through the mire with the nose wheel, but even early in the run, some lift will be obtained from the increased AoA, reducing the drag of the mains.
I learnt on a grass strip in a C150, and on my 4th or 5th solo take off, it got to about 30kts, when it would go no faster ploughing through the mud. Feeling that I could drive it like that to end of the strip, instinct caused me to jerk the stick back momentarily, which lifted me an inch or so to be aquaplaning on top of the mud, when I then accelerated normally to lift off.

A word of warning. Even on a hard runway, lifting the nose early also increases drag from the increased AoA and angled fuselage, so acceleration will be slower, and take off run greater. As IO says, this can be much better than the even more reduced acceleration caused by ploughing through mud.

However risks are that you will get off early in ground effect, without enough power to go anywhere whilst on the back side of the drag curve (not much likelihood in a TB20!), or the oncoming hedge at the end causes you to pull back even further, which prevents you getting airborne at all. AAIB reports have both of these cases. Several years ago, an aircraft trying to depart Bodmin lifted its nose early, finished up scraping its tail on the ground, failing to get off as it went into the hedge.

Muddy strips almost preclude confidence in take off run calculations, especially as its going to be different at various point along the strip.

MikeJ

IO540

20th Dec 2006, 15:16

Yes, I think there is a lot of misconceptions going around takeoff techniques and how they relate to the figures in the POH.

The POH figure is for a dry hard runway, unless otherwise stated.

A "soft field" takeoff is going to use a lot more runway than the hard runway figure. Even doing a soft field takeoff on a hard runway (pointless except when doing an FAA checkride perhaps) will use a lot more runway because of the extra elevator drag, acting like a giant air brake.

I suppose that in a low powered type (e.g. a C150) a soft field takeoff may be the only way to get off the ground so one cannot even do a comparison with a normal takeoff off the same muddy grass, but the resulting takeoff run is going to bear little resemblance to what is in the POH :)

I did a soft field takeoff the other day in the TB20, off a hard runway, and the run, including the bit in the ground effect, was about 600m. Whereas a normal takeoff is about 350m, both cases about 10% below MTOW. It was staggering how much extra drag there is due to the elevator being all the way back. A soft field takeoff may keep the mud collection down but that's not much use if you don't get off the runway. And this is a TB20 which has loads of power.

Those flyers that get handed out about grass taking 30% more than tarmac, etc, are meaningless in so many cases, IMHO.

RatherBeFlying

20th Dec 2006, 15:44

I once had the occasion to take 4 people up in a C-172 from a sand strip. First had a talk with the local CFI/operator to see if this was at all possible. His advice was not to keep the wheel all the way back once rolling.

Taxi took considerable power. Picked a point where I would abort if not airborne -- in the sand, 100 yards was plenty;)

Full power, wheel all the way back got me to about 40 kt and no more; so, eased off on the wheel. The a/c accelerated and I lifted off, built speed in ground effect and climbed away:ok:

The trick is to keep the nose wheel just clear of the ground once you have 30 kt or so as you now have lift taking the load off the mains.

Blasting all the way down a soft runway with the wheel/stick all the way back can add you to the statistics as before mentioned:uhoh:

HAL-26

20th Dec 2006, 15:51

Our home airfield stayed drained and perfectly servicable.

but....

CAVOK this morning - only on this side of the Chilterns.

Freezing fog on t'other side of the hills, all the way across Oxfordshire it seems.

Grounded. Grrrrrr! :ugh:

Riverboat

20th Dec 2006, 22:12

Shortstripper - haven't seen a response to your query, but it seems to me that iff Goodwood has an A/G service, it is you who are in charge, and you can, theoretically, do what you want. They might not invite you back if you do something silly, but taking off half way down a runway in a STOL aircraft wouldn't really constitute that.

If it is AFIS, they have the power to give instructions to ground movements (I think), but if you say you are lining up for take-off and then take off, you can do it, because they have no authority to grant you approval for take-off or refuse it.

Why not have a word with the aerodrome manager? They are probably concerned about noise, and you might be able to discuss the whole thing and reach a common sense answer (although in my experience, common sense is not common at airports!)

tonyhalsall

27th Dec 2006, 15:12

What a fantastic 'solution' - and even if it in't - what a great idea anyway.

Just heard that one of the guys at a local Club that is notorious for getting claggy and saturated has invested in a racing hovercraft which he bombs up and down the runway when it is completely sodden:

1) It's great fun
2) It doesn't damage the surface
3) Allegedly it dries the surface out

Ebay - here I come............................................

SlipSlider

29th Dec 2006, 21:46

Shortstripper wrote:
I flew into Goodwood Saturday and whilst they do a pretty good job of keeping their runways going, I can't understand the inflexibility shown? As I was taxiing to take off, I called up and offered to pull onto the runway where I was (half way between the tower and the hold) to save the grass at the threshold. There was one other on downwind in the circuit and I stated I was STOL ... but no I was told to taxy to the hold as usual and take off from the bit of grass that is getting increasingly muddy.
Hi SS. I was intrigued by this as I have seen occasional mid-point departures, including a friend visiting in a Rans S6 who was not keen to taxi downwind to the hold in a 20 knot breeze. Also the FISOs at Gwd are an excellent bunch, always helpful, and always friendly! :ok:
So, I spoke with the FISO yesterday, and he recalled the occasion immediately .... it seems that on that particular day it was felt that the threshold was actually preferable being less wet than the area where you suggested departing from; apparently there is a tendency to standing water near the runway intersection. Agree or not, that was the reason, and with the best of intentions.
Regards
Slip

shortstripper

30th Dec 2006, 07:09

Fair enough!

I'm familiar with Goodwood and wasn't near the point you say, however, in a drafty open cockpit it's not always possible to see the bigger picture :)

SS

ChampChump

30th Dec 2006, 08:13

"I spoke with the FISO yesterday, and he recalled the occasion immediately .... it seems that on that particular day it was felt that the threshold was actually preferable being less wet than the area where you suggested departing from; apparently there is a tendency to standing water near the runway intersection. Agree or not, that was the reason, and with the best of intentions."
Slip, reassure me you were merely talking to the FISO and not airing that wonderful machine?
This isn't thread drift because in this wind, one doesn't need a runway...:sad:

matelot

30th Dec 2006, 08:34

Water-logging is not a problem with our 1000m strip - it's the wild boar digging holes and ruts...

niknak

30th Dec 2006, 16:18

We recently had to withdraw our (tarmac)cross runway due to significant subsidence which would not have been cost effective to re instate.
However, I am convinced that the land adjacent to it is more than capable of supporting a 800 to 1000m grass runway.
I am aware of the CAA (CAP168) requirements, but any support for this from operators and how I could present this as a low cost alternative for G/A at our place would be gratefully recieved.
Ta.
niknak.

SlipSlider

30th Dec 2006, 17:05

ChampChump wrote:
Slip, reassure me you were merely talking to the FISO and not airing that wonderful machine?

Indeed I was merely talking to the FISO! I was all set to meet with others at Henstridge, but the cloudbase at Gwd was around <500' all day. I hung around to see if a short local might be on, but sadly not. That's it for 2006 it would seem.

Back to the thread ... maybe the threshold is in any case the best place to start from on a muddy runway, especially in a stol aeroplane, as most touchdowns (thumpdowns?) which damage the surface are much further down the runway! :)

Slip