Grass field - use when wet or no?

flhrci

flhrci

Final Approach
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David
I was supposed to go have another TW lesson today in the champ but rescheduled for tomorrow due to really low ceilings.

Anyways, we had a lot of rain over nigh and I got to thinking, are grass strips useable when they have been wetted down? Can a 65hp Champ takeoff on that with two people?

Or is it best to let the grass dry out first?

Supposed to go tomorrow and it is gonna get chilly. Should be fun flying the "pioneer pilot" way. lol :yikes:

Thanks,

David
 
Depends, Dave. We had a gulley washer at Gastons a couple of years ago and after a few hours it was fine.

The answer to your question is that it depends on how well the runway drains, how much rain over a period of time, and... well I forgot the third thing.
 
Insufficient information. Airport dimensions? How much rain is "a lot" Is runway crowned? How long is the grass? When mowed last? Was it wet prior to the recent rain? How much pax weight? and more.

flhrci said:
I was supposed to go have another TW lesson today in the champ but rescheduled for tomorrow due to really low ceilings.

Anyways, we had a lot of rain over nigh and I got to thinking, are grass strips useable when they have been wetted down? Can a 65hp Champ takeoff on that with two people?

Or is it best to let the grass dry out first?

Supposed to go tomorrow and it is gonna get chilly. Should be fun flying the "pioneer pilot" way. lol :yikes:

Thanks,

David
Click to expand...
 
We really need:
-is it crowned at all?
-does it have buried drainage?
-what soil type? (sand or clay)
-grass length

Could be fine or could be a bog.
 
There are only two concerns with wet grass runways:

  1. Sinking in (damage to surface and/or airplane)
  2. No traction
The first is a function of ground saturation -- you can't see this from the air. Someone on the ground must test then verify it's suitable for landing. The second requires some basic research (did it rain last night? is there a heavy dew this morning?)

I have a post on this topic here.
 
dmccormack said:
There are only two concerns with wet grass runways:

  1. Sinking in (damage to surface and/or airplane)
  2. No traction
The first is a function of ground saturation -- you can't see this from the air. Someone on the ground must test then verify it's suitable for landing. The second requires some basic research (did it rain last night? is there a heavy dew this morning?)

I have a post on this topic here.
Click to expand...

How can take-off distance be omitted from the list of concerns?
 
In Dave's case I'd ask the guys who rent the aircraft and own the field. It's their airplanes on the line, so if they think it's good enough I'm OK.
 
steingar said:
In Dave's case I'd ask the guys who rent the aircraft and own the field. It's their airplanes on the line, so if they think it's good enough I'm OK.
Click to expand...

Going to do that as I have to drive down there. This was just a question of how to make that decision. Never really came up in the past.

David
 
wabower said:
How can take-off distance be omitted from the list of concerns?
Click to expand...
I would guess Dan is probably conservative enough about taking off in minimal distance situations with the Chief that it did not even come to mind. :D
But I have to call foul on "traction"... unless the wheels are powered, that doesn't apply. :rolleyes: The key word here is "friction"... but friction is not always reduced when rolling in wet grass; sometimes it's increased.

I don't know a whole lot about grass runways, but I do know that wet grass basically slows you down when you don't want to, and keeps you from slowing down when you don't want to. :D
Wet grass is generally "stickier"- if it's tall enough, it will cling to the wheels more as you roll, creating friction. This can extend the takeoff roll distance, and shorten the landing rollout distance. But curiously, when you try to brake (and sometimes when you try to turn or use the wheels to stop a drift or turn) on wet grass, the friction seems to disappear. I guess an airplane can sort of hydroplane on wet grass... the grass compacted directly under the wheels releases water, maybe?
 
My grass strip never gets "soft," the substrate is pretty much gravel underneath (well, rotten granite properly). What does happen when it is wet is it gets slippery. Hard breaking will be fun. Fortunately at 3000' I could coast to a stop well before the end even if I never touchéd the brakes.
 
rottydaddy said:
I would guess Dan is probably conservative enough about taking off in minimal distance situations with the Chief that it did not even come to mind. :D
But I have to call foul on "traction"... unless the wheels are powered, that doesn't apply. :rolleyes: The key word here is "friction"... but friction is not always reduced when rolling in wet grass; sometimes it's increased.

I don't know a whole lot about grass runways, but I do know that wet grass basically slows you down when you don't want to, and keeps you from slowing down when you don't want to. :D
Wet grass is generally "stickier"- if it's tall enough, it will cling to the wheels more as you roll, creating friction. This can extend the takeoff roll distance, and shorten the landing rollout distance. But curiously, when you try to brake (and sometimes when you try to turn or use the wheels to stop a drift or turn) on wet grass, the friction seems to disappear. I guess an airplane can sort of hydroplane on wet grass... the grass compacted directly under the wheels releases water, maybe?
Click to expand...

Yes, friction is a better word. The problem on wet grass is the sudden change in friction from none to lots that can cause real problems.
 
This thread should have started on 4/20.

Grass. Haha. Sorry, just thought of that.
 
Greg Bockelman said:
Depends, Dave. We had a gulley washer at Gastons a couple of years ago and after a few hours it was fine.

The answer to your question is that it depends on how well the runway drains, how much rain over a period of time, and... well I forgot the third thing.
Click to expand...

And it's the third thing that is really critical here....

denverpilot said:
This thread should have started on 4/20.

Grass. Haha. Sorry, just thought of that.
Click to expand...

Now, now, he's just trying to get the straight dope on the topic!
 
flhrci said:
I was supposed to go have another TW lesson today in the champ but rescheduled for tomorrow due to really low ceilings.

Anyways, we had a lot of rain over nigh and I got to thinking, are grass strips useable when they have been wetted down? Can a 65hp Champ takeoff on that with two people?

Or is it best to let the grass dry out first?

Supposed to go tomorrow and it is gonna get chilly. Should be fun flying the "pioneer pilot" way. lol :yikes:

Thanks,

David
Click to expand...

If you are wondering about flying on wet grass like dew go for it. TW 's love the slipping and slidding on slick surfaces like wet grass.
 
dmccormack said:
There are only two concerns with wet grass runways:

  1. Sinking in (damage to surface and/or airplane)
  2. No traction
Click to expand...

wabower said:
How can take-off distance be omitted from the list of concerns?
Click to expand...

Actually, it is listed, indirectly. If you're not sinking in then your take-off distance will be minimally affected if at all. (affected? effected?, I can't keep those two straight).
 
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timwinters said:
Actually, it is listed, indirectly. If you're not sinking in then your take-off distance will be minimally affected if at all. (affected? effected?, I can't keep those two straight).
Click to expand...

Very true.

When I have the option, I take off from pavement and land on turf (I have that option now at S37 and had it before at KWAY, except in winter).

I always taxi around on the grass before takeoff if it's been wet recently, just to check for sink-in.
 
Wanna make a little bet on that?

timwinters said:
Actually, it is listed, indirectly. If you're not sinking in then your take-off distance will be minimally affected if at all. (affected? effected?, I can't keep those two straight).
Click to expand...
 
jpower said:
Generally speaking, "to affect" is a verb, and "an effect" is a noun. I always think of an aardvark being shot with an arrow--"the arrow affected the aardvark." Got that from here: http://grammar.quickanddirtytips.com/affect-versus-effect.aspx
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Generally speaking, both words are both nouns and verbs. (Don't get me started on the abuse of the word generally).

The issue is that the that the verb "effect" leads to the noun "affect."
However, "effect" is a perfectly good verb and "affect" is a perfectly good noun.
 
flyingron said:
Generally speaking, both words are both nouns and verbs. (Don't get me started on the abuse of the word generally).

The issue is that the that the verb "effect" leads to the noun "affect."
However, "effect" is a perfectly good verb and "affect" is a perfectly good noun.
Click to expand...

Oh yes I know that both are perfectly good nouns and verbs. Just that the more common use of "effect" is as a noun and the more common use of "affect" is as a verb. No need for grammar battles here, though. Just thought I'd try to be helpful.
 
When landing on wet or flooded grass, remember the "CAT" rule.
 
jpower said:
Oh yes I know that both are perfectly good nouns and verbs. Just that the more common use of "effect" is as a noun and the more common use of "affect" is as a verb. No need for grammar battles here, though. Just thought I'd try to be helpful.
Click to expand...

Then you do need to look up what generally means then.
 
wabower said:
Wanna make a little bet on that?
Click to expand...

Well, take-off distance on a grass strip is always a crap shoot anyway. Better have plenty of safety factor but if a rain doesn't significantly "soften" the surface then, no, it shouldn't increase take-off distance.

In some cases, a hard driving rain may actually decrease take-off distance on a well drained field if the driving rain lays down the grass that hasn't been cut recently.

I've also been on sandy strips down on the gulf coast that a good rain actually "firms up" and shortens the take-off roll.

Every strip is different so, yes, while sometimes take-off roll may be increased, sometimes it may be decreased also.

Rain has no negative effect on my field during the 7 to 9 months of the year when the grass is growing...in the winter it's a different story.
 
flyingron said:
Then you do need to look up what generally means then.
Click to expand...

Done! According to the Oxford English Dictionary:

With respect to the majority of individuals or cases; for the most part; widely, extensively.
Click to expand...
Here, a "majority of cases" is "a majority of uses of affect and effect." I really don't want to start a war, so I'll stop here. Feel free to tell me I'm wrong again, though.
 
So if the grass hasn't been mowed for a week prior to the rain, the take-off distance is the same whether wet or dry?

timwinters said:
Well, take-off distance on a grass strip is always a crap shoot anyway. Better have plenty of safety factor but if a rain doesn't significantly "soften" the surface then, no, it shouldn't increase take-off distance.

In some cases, a hard driving rain may actually decrease take-off distance on a well drained field if the driving rain lays down the grass that hasn't been cut recently.

I've also been on sandy strips down on the gulf coast that a good rain actually "firms up" and shortens the take-off roll.

Every strip is different so, yes, while sometimes take-off roll may be increased, sometimes it may be decreased also.

Rain has no negative effect on my field during the 7 to 9 months of the year when the grass is growing...in the winter it's a different story.
Click to expand...
 
wabower said:
So if the grass hasn't been mowed for a week prior to the rain, the take-off distance is the same whether wet or dry?
Click to expand...

No, yes, maybe.

It can be longer if the grass is still standing up.

It can be shorter if the grass was "laid down" by the rain.

It can be longer if the grass is "laid down" but the soil is "fat" clay.

It can be a lot longer if the grass is standing and the soil is "fat" clay.

It can be shorter if the grass is still standing but the soil is sandy.

It can be a lot shorter if the grass is laid down and the soil is sandy.

There are too many variables to answer the question and the above variables don't even include the time of year, type of grass or growth rate of specific species in specific seasons.

If you're asking specifically of my field then the answer is:

Yes, in April, May, September & October if the grass wasn't laid down.

No, if it was.

No, in June, July & August whether the grass wasn't laid down or not (because the cool season grasses don't grow much in a week).
 
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timwinters said:
No, yes, maybe.

It can be longer if the grass is still standing up.

It can be shorter if the grass was "laid down" by the rain.

It can be longer if the grass is "laid down" but the soil is "fat" clay.

It can be a lot longer if the grass is standing and the soil is "fat" clay.

It can be shorter if the grass is still standing but the soil is sandy.

It can be a lot shorter if the grass is laid down and the soil is sandy.

There are too many variables to answer the question and the above variables don't even include the time of year, type of grass or growth rate of specific species in specific seasons.

If you're asking specifically of my field then the answer is:

Yes, in April, May, September & October if the grass wasn't laid down.

No, if it was.

No, in June, July & August whether the grass wasn't laid down or not (because the cool season grasses don't grow much in a week).
Click to expand...

Excellent answer. Local knowledge rules. If you don't know the field, ask.
 
Threefingeredjack said:
Excellent answer. Local knowledge rules. If you don't know the field, ask.
Click to expand...

Agreed... Tim gave a great answer to a complex question... As a owner /operator of my own grass strip it can feel his pain when conditions are not "dry"..:yesnod::eek:
 
Same answer if it's their field and your airplane is on the line?

steingar said:
In Dave's case I'd ask the guys who rent the aircraft and own the field. It's their airplanes on the line, so if they think it's good enough I'm OK.
Click to expand...
 
wabower said:
So if the grass hasn't been mowed for a week prior to the rain, the take-off distance is the same whether wet or dry?
Click to expand...
That depends upon how far your aircraft will slide while on its back.
 
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