Inverted flight as a part of manouveres, dogfights, acrobatics is fairly common but my question is:
Are any aircraft capable of sustained inverted flight without losing altitude? e.g. Could you fly 10 mins inverted at the same flight level?
To clarify: I'm not wondering about engines, fuel systems, air-frame strength etc. Fundamentally there's no reason why those systems cannot be engineered to be robust against inverted flight.
What I'm curious about is specifically the aerofoil itself.
i.e. As far as I can see, you'd need to balance the gravity vector with lift.
Ergo, are aircraft wings generally capable of providing enough compensating lift in the "wrong" direction to balance gravity? Are all / most fighters / arerobatic certified craft capable of this?
We'd need an aerofoil that can provide a lift vector pointed in the +z direction normally but changable to a large vector pointing in the -z direction in response to a flight surface deflection?