Treaty-exempt sloops become early helicopter escorts

The first service generation arrives around 1929-30 in this counterfactual, just as the London Naval Treaty shapes which hulls can absorb the new aircraft. Destroyers already balance guns, torpedoes, speed, and treaty tonnage, leaving little room for an immature air group. Treaty-exempt sloops are a better laboratory because they can reach about 2,000 tons, need not exceed 20 knots, and cannot carry torpedoes. They are inexpensive enough for repeated experiments and already perform convoy escort, anti-submarine, mine-warfare, and presence missions. A broader stern, a hangar, and guns concentrated forward could support the new role without sacrificing the ship's basic purpose. Carrying at least two helicopters, and perhaps as many as four, would also compensate for low interwar aircraft serviceability by keeping one available while another is under maintenance.