Why publish an unusable airway?

Question

If an airway is marked unusable, why publish it?

Secondary question, can RNAV still be used?

Answer 1

Short answer: only part of the airway is unusable, and even then it's usable with GPS.

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Your image shows V522 between FAILS intersection and the ERI VOR but you have to look at the full airway, which runs from the DJB VOR in the south-west to MYPAL intersection in the north-east:

As you can see, only some parts of it are marked unusable, even if they're very large parts in this case. But you can still use the rest of V522 apart from those sections; the NOTAMs say the ERI VOR's signal is unusable beyond 20nm until December:

FDC 6/6576 (A0050/16) - OH..ROUTE ZOB. V522 FAILS, OH TO ERIE (ERI) VORTAC, PA NA ; ERIE (ERI) VOR R-264 UNUSABLE BEYOND 20NM. 19 MAY 11:59 2016 UNTIL 29 DEC 11:59 2016 ESTIMATED. CREATED:19 MAY 11:59 2016

A 7-month 'outage' covers several of the FAA's 28 or 56 days chart cycles, so I guess they decided it was worth charting in addition to the NOTAMs. Removing the sections completely from the chart would mean decommissioning or redesigning the full V522 airway, which is presumably a much bigger task than just marking it unusable.

Finally, the ATC orders give some instructions on this and if part of an airway is unusable because of a NAVAID issue they still expect RNAV-equipped aircraft to be able to use it:

4−4−4. ALTERNATIVE ROUTES

When any part of an airway or route is unusable because of NAVAID status, clear aircraft that are not RNAV capable via one of the following alternative routes:

So the only aircraft that can't use those parts of V522 are ones that have to use the ERI VOR signal for navigation and even then they can expect ATC to give them an alternative route.