It may sound unusual, but in a few apple varieties some fruit drop is to be expected. Do the fruit grow in bunches on the tree branches? If so, as fruit grow, some fruit will be pushed from the bunch. This is because the tree produces more flowers than the number of fruit it can actually bear to full ripening. The overproduction of flowers acts like an insurance in the face of possible issues such as poor pollination or pest pressure.

Insect or pest pressure could also cause premature fruit drop, and it is worth noting that you may find pests in the fruit, but also possibly on the leaves or branches. Pests that feed on other parts of the tree (such as leaf-eating insects or mites) may stress the plant, causing it to prematurely drop fruit. You may wish to check for and identify these pests so you can treat for them and reduce fruit loss. If you find pests, please share your pictures here to see if others can help!