The spellcheck feature can be activated in AutoSpellchecker mode. This AutoSpellchecker mode enables queries with 0 result to be relaunched using the spellchecker's suggestions.
Usage example
If the "topcs" query returns 0 result, the spellchecker might suggest to search for the "topics" term. In AutoSpellchecker mode, instead of simply suggesting to launch a new query with the "topics" term, the query engine automatically indicates that there is no result for the "topcs" query and suggests results for the "topics" query.