History point
When the Electra was originaly designed it was intended to have just the two seats and no engineer. However at the time the FAA were looking at the new fangled jets such as the 707 and 727 and felt that these complex types should have an engineer station and passed rules to govern this. The L188 was included, so late in the design stage the third seat was added a few switches were added to give him somthing to do and conformity with regualstions was achiedved. If the L188 had been a true three crew aircraft it would not have been possible for Atlantic to do away with the third seat.