Tag Archives: military

Pylon Turns and Long Line Loitering

A pylon turn is a manoeuvre in which an aeroplane flies in a circle, banked with one wing pointed towards a fixed point on the ground.

Pylon turns were originally used in air racing, and are used extensively by military aircraft, as it allows them to easily and accurately direct fire onto targets on the ground for a long period of time.


In the photograph above an AC-130 Spectre gunship is executing a pylon turn. The aircraft’s GAU-2/A miniguns and L/60 Bofors cannon are visible on the aircraft’s left-hand side, pointing towards the centre of the pylon turn.


An AC-47 Spooky gunship executing a pylon turn whilst directing tracer fire against a target on the ground.

The physics of a pylon turn depend on the bank angle, the speed of the aircraft and the aircraft’s altitude, but these are intrinsically linked. You can pick two, but the third is then fixed: a pylon turn can only occur at a certain bank angle for a given speed and altitude; or at a certain speed for a given bank angle and altitude; or at a certain altitude for a given bank angle and speed.

A pylon turn also allows for a procedure called long-line loitering, in which a container can be lowered to the ground from a moving aircraft, remaining stationary on the ground in the process. This enables delivery and retrieval of material without the aircraft having to land.


Patent drawings from US patent US3724817 A. Click to enlarge.

A drag cone (a small parachute) helps to pull the line into a loop, keeping it relatively stationary and allowing the far end of the line to drop to the ground. This technique has been used to retrieve personnel and even to deliver mail.



The Boomerang Shooter Detection System is a gunfire locator system, designed for use against snipers, that tells its user the location of a source of gunfire, allowing those under attack to return fire. The Boomerang system can be mounted to vehicles, and works at speeds up to 60 mph, or can be used in a stationary perimeter defence role.

boomerang-mountedBoomerang mounted to an armoured vehicle.

When a bullet is fired it makes two types of noise: a muzzle blast as the round exits the barrel, and a supersonic shockwave as it moves through the air. By measuring the differences in volume and in time between these sounds reaching each of its seven microphones, Boomerang is able to calculate the range, elevation and azimuth of the shooter’s (or shooters’) position and then displays this information to its user.

This method is the one that humans use to locate sounds, though we do not have the benefit of seven ears. The algorithms that Boomerang uses are more complex than humans’, as it has to differentiate between incoming and outgoing fire, and between gunfire and other noises such as cars fireworks or cars backfiring.


The Boomerang display panel is shown above. Range and elevation are displayed on the green digital readout, and the azimuth is indicated on the clock display. This data is combined on the small circular LED panel in the bottom right-hand corner.

National Radio Quiet Zone

The US National Radio Quiet Zone (NRQZ) is a rectangle of land, approximately thirty-four thousand square kilometres in area, that crosses into Virginia, West Virginia and Maryland and contains the National Radio Astronomy Observatory at Green Bank and the Sugar Grove Research Facility at Sugar Grove (part of the US Navy’s Information Operations Command and said to be an important part of the NSA’s ECHELON system).


The Green Bank Telescope, the world’s largest steerable radio telescope.

Within the NRQZ radio emissions are highly restricted; conventional television and radio  transmitters do not operates and people who (incorrectly) believe that they are sensitive to electromagnetic emissions have flocked there in order to deal with their “problem”. Electric fences, electric blankets, car electronics and even radio-tagged animals have all caused problems in the NRQZ and all on-site vehicles must have diesel engines rather than petrol engines, as diesel engines use the heat generated by compressing petrol vapour rather than spark plugs to ignite their fuel.

Computer designed camouflage

In 1996 Canada became the first country to adopt battledress with a camouflage pattern generated by a computer, also known as digital camouflage.

L-R: Simulated CADPAT (Canadian Disruptive Pattern) for temperate, arid and arctic regions.

It is not the pixellated appearance of the pattern from which digital camouflage gets its name. There are a number of pixellated patterns that are not digital camouflage (e.g. Soviet “Birch Leaf”), and a number of digital camouflage patterns that are not pixellated (e.g. Italian “Vegetato”).

Rather the term “digital camouflage” comes from the computer-aided process by which the pattern is developed, using computer models of how human vision works and applying complicated computer techniques such as fractal generation and recursive algorithms employing both macro- and micro-patterns. The hope is that this more scientific approach will result in camouflage patterns with lower detectability, and this seems borne out by the fact that most militaries are now adapting digital camouflage patterns.