A disabled president?

Brit Hume, at Fox News, cites an LA Times report that John McCain is receiving about $58K/year, tax-free, because he is 100% disabled from wounds sustained during the Vietnam war, including his time as a POW.

It's my understanding that 100% disability means that you are unable to work. The federal definition of disability, as reported in First Draft: 100%? Really?: "Total disability will be considered to exist when there is present any impairment of mind or body which is sufficient to render it impossible for the average person to follow a substantially gainful occupation;"

McCain himself has claimed that he's healthy enough to hike the Grand Canyon. A spokesman for McCain, senior adviser Mark Salter, reiterated that the senator is entitled to his pension. "Tortured for his country -- that is how he acquired his disability," Salter said.

So, he's in good health, even though he's 100% disabled. If a truck driver who was receiving a disability payment was seen hiking the Grand Canyon, how long do think it would be before the disability claim was reviewed and then overturned.