Barrett hints

• See also SECTION_FF3:_CONTROL_CABLES
• Barett has had issues in Q1/2023 sourcing IO-540-D4A5 crank cases (at least for rebuilt engines) and has at least for one order substituted the case with an O-540-P1A5 one. This case has the oil filler tube at the lower rear end of the engine which requires several modifications to make the dip stick and oil filler opening accessible though the cowl. Barrett took the engine back for exchange / modification.