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Loss of performance on grass

Reading the end of Stick & Rudder…

“Tall grass has 15x as much drag on the wheels as concete”

Obviously it depends on the “tall” and it depends on the grass height relative to the wheel radius (large wheels will be less affected).

But it’s worth a thought. I have seen a TB20 get off in 300m tarmac, 400m very short grass, or 1000m of 20cm tall grass. The last one was a shock to me, especially as the owner of the “runway” told me it is in great condition.

Administrator
Shoreham EGKA, United Kingdom

I had no problems so far with gras runway and I like airfield with gras runway very much. Only about 2 years ago when we visited Konstanz for the Aero trade fair, the ground was very soft so it was hard to get out of the field with only 2 person, half of fuel and my plane with 180hp on a 760m runway. Never had this before in this way. 20cm gras is too much and I think you had cut the gras with the propeller. Cleaning the aircraft took at least half a day after this event I suppose.

EDWF, Germany

I don’t know about 15x, but longish wet grass can certainly surprise you, that’s for sure!

Tököl LHTL

Common misconception; it’s not so much the length of the grass which matters; it’s the degree of “softness” of the underlying soil.

Mainz (EDFZ) & Egelsbach (EDFE), Germany

“Grass” is a very general term. I’m hardly a botanist, but I do know that some “grass” is much more robust that other, and therefore more likely to affect performance. I once had my 150 into grass so high, that when I closed the cabin door, it pinched a whole bunch that was higher than the door sill. That really did affect takeoff performance! And. I agree that the underlying soil can really be a big factor too. It is worthwhile to practice soft field technique, and to have a good sense of when performance has been limited to the point that a takeoff attempt should be abandoned.

Home runway, in central Ontario, Canada, Canada

In long grass the streamlined fairings would help and if no lawnmover the modification of fairings with razorblades could be an idea. The taildraggers are home in grass but others keep on paved runways.

Matti
EFHV

20cm gras is too much and I think you had cut the gras with the propeller. Cleaning the aircraft took at least half a day after this event I suppose.

It took somebody a whole day and cost me £200 The grass cuttings are very hard to remove from the airframe; they don’t wash off easily after they have dried.

Administrator
Shoreham EGKA, United Kingdom
7 Posts
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