To protect the engine from blowing up as it is easy to open the throttles to far during take off at sea level.

The speed is too low for an indication.

Because the specific gravity can change with temperature.

They are aerodynamically efficient surfaces located at the wing tips, designed to reduce induced drag and increase fuel efficiency.

They increase efficiency by reducing the size of the wingtip vortices, which are created by the difference between the pressure on the upper surface of the wing and that on the lower surface.

The Dry Operating Mass (DOM) is the Basic Empty Mass and the Variable Load, also called the Aircraft Prepared for Service (APS) weight.

NDB’s are stations emitting a signal. There is nothing for them to be accurate about. ADF's on the other hand, when tuned to an NDB need to be accurate within +/- 5 degrees.

You can go through a DA, but not a MDA.

A Decision Height, used in precision approaches, defines the point where a go around should be performed. It accounts for the altitude loss during the initial seconds of the go around maneuver.

The MDA does not account for this and assumes the pilot will never go below this altitude. When performing a CDFA most operators establish a Derived Decision altitude (DDA) to account for the extra lost altitude.

NDB’s can suffer from a lot of errors.

A line across the surface of the earth that cuts all meridians at the same angle. i.e. a track of constant direction.

A straight line on a Mercator chart.