It's situation dependent. In 49 out of 50 states, you would only need a CDL for that vehicle if it were either a bus designed to transport more than 15 persons (including the driver) or if it were carrying a quantity of hazardous materials which required hazmat placards to be displayed.
New York state, however, requires a CDL for intrastate commercial use vehicles with a GVWR in excess of 18,000 lbs. IMO, it's a good policy. I don't think someone without an upgraded license of some sort should be able to drive anything larger than a Class 4 truck.
There are some exceptions under the FMCSR, and to which even New York grants exceptions:
When a vehicle falls under such exemptions, licencing requirements are left to individual states. Some states may have non-CDL Class A and B licenses, some states may categorise them under the Chauffeur's Licence system with endorsements for the vehicle type, and, in some states, you could operate a tractor-trailer which falls under these exemptions with the same licence you'd need to drive a regular passenger car. As you did not list a state, it's impossible to tell what your state's laws are on this matter.
Air brakes have absolutely ZERO determination in whether or not a vehicle requires a CDL.
Only if it's a vehicle equipped with air brakes.
No. Air brakes are not a parameter in determining whether or not a vehicle needs a CDL.
Air brakes are entirely irrelevant as far as whether or not that vehicle needs a CDL is concerned. The only time you need a CDL to drive an RV is when you're operating it on a for-hire basis, either as a driver for hire or as a transporter.
brakes.
The air brakes don't matter, insofar as whether or not a CDL is required. As for the GVW being over 26,000 lbs., yes, unless your vehicle falls in criteria for the farm vehicle, military vehicle, emergency vehicle, or recreational vehicle exemptions.
Only if it's a: transporting hazardous materials or b: a bus designed to transport more than 15 persons (including the driver).
Only if it's hauling hazmat or is a bus designed to transport more than 15 passengers (including the driver). Air brakes have absolutely nothing to do with whether or not a vehicle requires a CDL.
If it's not a firefighting or first response vehicle, recreational vehicle, registered farm vehicle, or military vehicle (operated by military personnel in the course of their duties), then yes - not because of the the air brakes, but because of the weight rating of more than 26,000 lbs. GVWR.
To answer you we need to know what country's traffic regulations you are asking about.
Only if it's transporting 16 or more persons (including the driver) or sufficient quantities of hazardous material to require placarding with HAZMAT warning signs.
No, unless you're hauling something which requires a hazmat endorsement, such as contaminated soil.