in my aircraft operation manual it is written that climb speed till 5000 feet indicated is 80 knots and above 5000 feet indicated is 75 knots. plz someone guide me regarding the following points:-
1. why climb speed should be kept less than normal above 5000 feet indicated?
2. why climb spleed has been mentioned in relation to indicated altitude rather than density altitude which is applicable for performance and aerodynamics of normally aspirated engine?
3. why this indicted altitude is 5000? why not 4000 or 6000?