Scenario: SQL Server 2014 CU6. 1 AG with 2 databases (compatibility level 100). Failover Cluster with 3 nodes on Windows Server 2012 R2. Primary Availability Replica on node 1 and node 2. Secondary Availability Replica on node 3 (no votes). Async commit, manual failover, readable secondary. Node 3 is used to run reports on these 2 databases (out of 8 databases running outside AG on node 1 and 2). 

Problem: Looking to patch these from SQL 2014 to SP1 and latest CU. Not my build and no experience with AG or FC so far. My "test" environment is also used for development, so no room for mistakes. 

Questions:

What's the best order to patch the 3 nodes ? 

Do I first have to remove the databases from AG on the node I'm patching ?

Do I need to take the Secondary out when patching it ?

No experience on this, and I can't find clear answers for my scenario (maybe not supported?) in the docs: <https://msdn.microsoft.com/en-us/library/dn178483(v=sql.120).aspx>