We also had a nicer permanently installed loran C in the L-1011's though still manual. We used it on JFK SJU. The flights frequently flew through the dusk hours when the loran C transitioned from ground wave to sky wave. If you matched a skywave slave signal to a groundwave base signal or vice-versa your position error was tens of miles. You had to take fixes every fifteen minutes or so to make sure you were on the right waves. Most of the Captains didn't care because of you take off from JFK and head 180 you arrive in SJU. They'd done that in DC 4s, 6s, 7s and Connies for years. You just hold that 180 heading. The westerlies that push you off course are cancelled by the trades that push you back. They usually equaled out. There was a rumor from the '40's that a JFK SJU DC-4 got lost and had to fly back NORTH an hour to get to SJU.