Dead trees, dry trees
Dry trees caused by infestation or forest fire, for example, should only be felled when there are many of them. A few dead trees are valuable to ecological diversity and should be left untouched.
Dry trees are solid, hard and brittle and have poor strength at the hinge. They also weigh less and therefore may be harder to fell.
As the timber is greatly weakened, you should fell the tree in the natural direction of felling. Make the directional notch deeper than normal (up to 1/5 of the diameter of the tree is a decent depth). If the tree is very thick, you can reduce the amount of timber at the hinge with a bore in the directional notch.
Saw the felling cut as usual. Use a breaking bar where possible. If you use felling wedges, be careful to ensure the load on the hinge is not too great when you knock them in.
Beware of dry, falling branches and be aware that the top of the tree could break and fall back when the tree falls.
Safety first! Felling a dead tree is particularly hazardous and should only be performed by a person with sufficient knowledge and experience. Plan the felling thoroughly and consider all the risks involved.
To fell a weakened tree in a controlled manner, apply the same technique as for the directional felling of healthy trees with the directional notch, felling cut and hinge. But as the timber is greatly weakened, or partially missing at the hinge, you should either fell a tree in its natural felling direction or secure with ropes.