3-12 Aviation

Hot-air balloons were the first aircraft that allowed man to fly.  Today, the balloon is used primarily for sport.  A hot-air balloon is make of a large, air-tight cloth or plastic bag filled with air.  Hot air is lighter than cool air.  The balloon rises because the heated air inside is lighter than the cool air outside.  When the heated air cools, the balloon will stop rising and come down.

Blimps are wingless, have an engine or engines, and can be steered with a rudder.  Large corporations, such as the Goodyear Rubber Company, own and maintain blimps for advertising purposes.  A blimp has a rigid piece of metal or wood that runs along the bottom of the helium-filled envelope, to which a control car or cabin is attached.

Hot-air balloons and blimps belong to a group of aircraft group called lighter-than-air.  This is because they are lifted into the air by a gas that weighs less than air.

Directions: Answer the questions below about lighter-than-air aircrafts.

Which of the following aircraft is used for sport today?

hot-air balloon
blimp

Which of the following aircraft is used for advertising today?

hot-air balloon
blimp

air is lighter than air.

When will a hot-air balloon stop rising and come down?

When the heated air cools.
When the cool air heats up.

Blimps are wingless and are steered with a .

A blimp is filled with the gas .

Which of the following statements is true?

Lighter-than-air aircrafts are lifted into the air by a gas that weighs more than air.
Lighter-than-air aircrafts are lifted into the air by a gas that weighs less than air.