Will the f18 and the f15 fly from a 100 meter grass strip with a 22lb turbine?

Do they slow up easily? What sort of landing speeds are attainable?

Both should be OK with that much thrust. Probably would with even less. Check Air Pac link at the top of this forum .

This F-15 can be slowed down to 40/60 prop trainer speed for landing. 100 meters runway is plenty with 22lbs thrust provided that you don't have obstacle at the end. Try this short field takeoff technique: hold the elevator up at least 50% on takeoff roll and the nose will rise shortly then you can release the up elevator for shallow climb to build speed. With this technique, the F-15 will not "jump" off the runway but rather climb out at slow and controllable speed. This is spectacular when the liftoff is right in front of you!!....big and slow...great for photo shots

B777

The F-15 will be fine but I know the F-18 will struggle a bit. It really depends on the overall weight of the model and the state of the grass.
In general the F-15 is far better suited to constant grass field use