BV234
The commercial Chinook Flight Manual contained some very ambitious claims for operating speeds. At MAUW, rarely WAT limited, the book might say 130-135 knots. The aircraft vibrated a lot and each pilot seat and the entire 44 pax cabin were mounted on vibration absorbers, the left-hand seat being the worst for vibration.
With each flight from Aberdeen scheduled for 5-6 hours, on occasion 8.50hrs, one didn't wish to tarry so sought the maximum practical cruise. This meant accelerating once level using the 'cocked hat' until the co-pilot began to look blurred then reducing speed by a few knots until he came back into focus and stopped complaining produced the cruise speed, typically 115 knots.