Wings doesn't always go to the closest hospital or their base if they have a patient on board. If they need a Level 3 trauma center they'll go to the closest one which seems to be either Johnson City Medical Center or Holston Valley in Kingsport most of the time. I've heard them coming back to JCMC from scene calls close to Boone,NC and Greene County. It also depends on how many patients they have from 1 scene call if the distance is about equal. For example scene call on interstate 81 in Greene County may take some patients to Holston and some to JCMC. I have heard 3 Wings all coming to JCMC from 1 scene call in Carter County. The first one back in does a hot offload and then moves to the maintenance hanger. The next one does the same thing to make room for the 3rd one. Holston Valley has an upper and lower pad, so do something similar there. This all gets even more complicated when you have other chopper transports coming in at the same time using different air rescue services. Wings also does transports between hospitals such as getting a patient from Mountain City Hospital going to JCMC.
Wings are based in several different areas. This is how they're based according the their website: Mountain States Health Alliance | Service Area
Wings I - Elizabethton, TN
Wings II - Greeneville, TN
Wings III - Jenkins, KY
Wings IV - Marion, VA
I don't know if these are still accurate. I'm pretty sure Wings 1 and 2 are right. And I know there is a Wings V but it's not listed above so not sure where it's based unless it's Johnson City. I'm pretty sure there is a chopper based there because I always see it sitting on the pad outside the ER and they have a maintenance hanger for them.
I've also found out the 2 frequencies (857.1375 91.5 PL, 855.5625 82.5 PL) receive the same transmissions. They are just different towers. One tower is High Knob (maybe on Holston Mtn ?), the other I think they said is Black Knob. Not sure where it's at but definitely further away from me.