HX-21. Air Test and Evaluation Squadron TWO ONE

via Wikipedia...

Air Test and Evaluation Squadron TWO ONE (HX-21) "Blackjack" is a U.S. Navy aircraft squadron located at Naval Air Station Patuxent River, Maryland on the Chesapeake Bay. As part of the Naval Air Warfare Center Aircraft Division (NAWC-AD), Naval Test Wing Atlantic (NTWL), HX-21 is responsible for the Developmental Test and Evaluation of Navy and Marine Corps rotary-wing/tilt-rotor aircraft, airborne systems, and Unmanned Aircraft Systems (UAS) in support of acquisition decisions that improve the Navy and Marine Corps' war fighting capability. Additionally, HX-21 tests and evaluates new mission systems to integrate legacy aircraft into the constantly evolving fighting force.

Ok, I'm at ease now.  In that formation, I saw a CH-53E in what appeared to be perfect condition along with two AH-1Z's and a UH-1Y.

First thought was...why aren't they operating with the fleet.

Now it makes sense.