Échoir is a defective verb. It can not be conjugated in all possible forms.
Here are several examples of defectives verbs:
paître.
Échoir verb is conjugated in negative form. The placement of the negative adverb follow the following rules:
- the adverb
« ne » is placed after the pronoun and before the verb.
- in simple tenses, the adverbs (
« ne ...pas »,
« ne...plus »,
« ne...jamais », etc...) surround the verb
échoir.
- in compound tenses or in ive voice, the negative adverbs surround the auxiliary.