Blind Approach Beacon System facts for kids

A blind approach beacon system (BABS) was an early type of radar system. It helped aircraft land safely, especially when pilots couldn't see the runway. This system was developed in the early 1940s during World War II.

What is BABS?

BABS stands for Blind Approach Beacon System. It was a special kind of radar that worked like a helper for planes. Imagine a guide that tells a pilot exactly where to go, even in bad weather. That's what BABS did for landing aircraft.

How did BABS work?

The BABS system used two main parts. One part was on the ground, and the other was in the airplane.

• The ground part was a special radio device called a transponder. It was often set up in a Hillman van near the end of the runway. Later, some permanent stations were built.
• The airplane had a device called a Rebecca unit. This unit would send out a signal to the BABS transponder on the ground.

When the BABS transponder received the airplane's signal, it sent back its own message. This message was sent using Morse code. It sent short "dot" signals on one side of the runway and long "dash" signals on the other side.

The airplane's Rebecca unit would listen to these dots and dashes. It could tell how strong the dot signals were compared to the dash signals. This helped the pilot know if the plane was too far left or too far right of the runway's center. It was like a radio path guiding the plane straight down the middle.

BABS vs. Modern Systems

BABS was a very important step in aviation history. It was an early version of what we now call a localizer. A localizer is a key part of the modern instrument landing system (ILS).

Today's ILS is much more advanced. It uses different radio signals to guide planes. These signals tell the pilot not only if they are left or right, but also if they are too high or too low. You can see the antennas for these systems at almost all airports. They are usually at the end of the runway.

The ILS helps pilots land safely in almost any weather. It gives them precise information to guide the aircraft right onto the runway.

See also

• Precision approach radar
• Instrument approach
• Ground-controlled approach