Aurigny Trilander Aircraft

[depolox4]

I have occasion to fly to Alderney now and again, and as always in a Trilander. This last trip I was sitting in the row just behind the pilot, and at the top of the climb I noticed he adjusted the throttle then adjusted the RPM levers (to synchronise the RPM of each engine maybe?), my question is: How can the RPM change without the throttles being altered. Does the RPM lever alter the pitch of the propellers thus taking more or less "bite" of the air, or are the throttle and RPM controls interconnected.

Thanks