Tag: air traffic control

What is a “radar reflector” and how does it work, why do we need one;

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This is the radar reflector we will attach time our balloon train

What is a Radar Reflector?

Radar reflectors are simple devices that are used to make something more visible to radars. For example, kayakers in foggy areas use radar reflectors to avoid being run over by bigger boats, weather balloons have reflectors that allow them to appear in Air Traffic Control radars, and so on.

 

How do they work?

They are built to have reflective surfaces (typically of metal) in 3D at 90-degrees at each other. Incoming radar waves bounce off one, two, three surfaces and head back to the source direction. The principle behind them is similar to the one that makes you always see your ‘eye’ in the point where two mirrors cross each other at 90 degrees.

 

Can we build our own?

We need a radar reflector is extremely light. Typical DIY reflectors use tin foil sheets. Commercial ones are available for £30 and above but are quite heavy. There are options to build them e.g. by wireframes and mylar sheets; which could be lighter than this construction but are also more complex to build.

 

Why do we need one?

We require a radar reflector as it makes our balloon visible to Air Traffic Control radars, which simply means people know where the balloon is at all times which enables people to avoid the balloon rather than causing an accident.

 

References:

https://www.instructables.com/id/Lightweight-Radar-Reflector/#:~:text=Radar%20reflectors%20are%20simple%20devices,Control%20radars%2C%20and%20so%20on.

https://www.overlookhorizon.com/how-to-launch-weather-balloons/radar-reflectors/

 

 

 

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What arrangements do we need to have with the CAA and ATC (Civil Aviation Authority and Air Traffic Control)?

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The Civil Aviation Authority (CAA) is responsible for the regulation of aviation safety in the UK. (UK government)

 

Air traffic control aims to move aircraft safely and efficiently through the airspace system. (CAA)

 

We will need to notify the CAA via a NOTAM requesting permission to launch a balloon on a certain date, and after we have assessed all risks.

 

NOTAM- a written notification issued to pilots before a flight, advising them of circumstances relating to the state of flying. (oxford dictionary)

 

NOTAM request:

https://notaminfo.com

 

NOTAM map:

 

How to make a NOTAM submission – guidance

 

NOTAM guidance

 

Aeronautical Information Service

 

Risks:

Pre-flight, we will need to check:

  • airfield restrictions including checking airfield restrictions – military and civilian danger areas, restricted areas, airports and restricted airspace;
  • identifying the local ATCU (Air Traffic Control Unit- Carlisle) and make a note of their contact details;
  • permissions to take off via a NOTAM, and make a risk assessment of the launch;
  • a list of emergency numbers.

 

[Download the Drone Assist App which has all interactive map of airspace used by commercial air traffic so that you can see areas to avoid, as well as ground hazards that may pose safety, security or privacy risks when you’re out flying your drone.]

 

A few days before and on the Day, we will need to check weather conditions by using a site such as www.metoffice.co.uk for:

  • Weather conditions
  • Temperature
  • Wind speed & direction
  • Cloud type and cover

References:

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What heights do civilian and military aircrafts usually fly at?

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Civilian aircrafts usually fly between 9,000 metres and 13,000 metres above sea level (30,000 feet to 42,000 feet- the aircraft industry still use feet and inches). This height is known as a ‘sweet spot’. As you increase in height, the air resistance gets lower but so does the abundance of oxygen. Between this range, there is a relatively low air resistance, yet still enough oxygen to fuel the engines. Of course, the exact height of planes changes depending on weight, fuel or cost. When planes are ascending or descending they follow special flight paths cleared by air traffic control.

 

Fun fact: the highest ever commercial airliner actually flew at 60,000 feet. Anyone know the name of the aircraft? (no cheating)

 

Military aircrafts can fly at many different heights with a minimum of 200 metres (500 feet) to the highest military engine flying at 27,000 metres (90,000 feet). However, generally military jets fly at around 15,000 metres above sea level (50,000 feet).

 

Also, I wanted to mention the SR71 Blackbird which flew at 26000 metres (85,000 feet) and had a clever variable cone on the front used to slow the speed of the air entering from supersonic speed to subsonic speed before entering the engine. The air passes through a conical shock wave that forms on the apex of the cone then passes through a strong normal shock wave and exits at subsonic speed.

References:

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