How wet is wet grass?
 

With the weather of the last few weeks, my grass strip is as sodden as I've ever seen it. How do you tell whether it's too soggy to fly from?

I've tried driving the car down the strip. It dug deep furrows and hit unseen puddles so I decided that was too wet. But how do I test it next time without adding more furrows at each test? By the time it dries out it'll look like a potato field!

An interesting point!

I notice that the North Weald parallel grass runway 02/20 has been closed pro tem, as a Sea Hurricane sank into it and had to be dug out. So I guess one (belated) way of judging is if you start to slow down and the grss looks a bit closer than usual. (If the world takes on a green huse, you're in deep doo - metaphorically and literally!)

Does this mean that the test is: Have a look at your strip and see if there are any Sea Hurricanes sticking out of the surface. If there are, you know it's too wet.

There's a rule of thumb I believe that if you haven't got half your take-off speed in a quarter of the runway, you aren't going to make it and should abort.

Personally I start off walking the runway. If I get wet turn-ups or can hear the squelch it's too wet to try the other test.

G

I think Geghis has the best ad hoc method. I recall that long wet grass can have a dramatic effect on takeoff run required, an increase of up to 30% may occur. (CAA Safety Regulation Group Accident Survey study 1991)

If you can't walk the length of the strip without squelching, or if water starts to seep up beside your foot when standing still it's definitely best to leave the aircraft parked.

If you really have to make the attempt (in a light aircraft, I assume), try taxying the full length before takeoff. If you don't bog the wheels then you have to make the difficult decision whether to go or not. If you bog it, the decision's already made!

It's a cliche but "takeoff's are optional, landings are mandatory."

I think the Sea Hurricane test ought to do it for sure. I landed once in a wet field (in for my annual - I knew I didn't have to get out again for several weeks). First up, the owners told me to stay to the right of the centre line as left = very very wet, then my landing roll was very short ( a product of a nervy and slow approach, then no shortage of friction (ie mud) to drag me to a halt). Followed by almost full power to turn around and backtrack to the hangar... not recommended. Moved my annual from January to November (and tell me, how has the weather been this November...?)

Redhill has had a Sea Hurricane sticking out of it for about two months now. While waiting for the mud (sorry Grass) to dry out, they occasionally let us use the southern taxiway. This is rather unusual as it has a distinct kink to the left about halfway down and the take-off technique sometimes resembles the tethered one used on the “short field” thread.