two questions Boeing 747
I have two questions regarding the Boeing 747 and would appreciate if another forum member could answer them.
1. Why does the 747 have a lower and upper rudder and an inboard and outboard elevator respectively. As they move simultaneously, why not have only one control surface?
2. The 747 is designed to cruise around Mach 0,85. In this context, what is the Mach crit for the 747?
Thank you in advance for your help.