# Twisting Puzzles

Helicopter Cube - Solution

## Introduction

There are two types of turn on the helicopter cube.

**Normal turns**- 180° turn swapping two adjacent corners and 2 pairs of centres.**Jumble turns**- Any turn which changes the shape of the puzzle.

This solution is for a puzzle which has been scrambled using normal turns only. Jumble turns result in the puzzle changing shape. When restored to the cube shape without solving the colours, it's possible to have the puzzle in a state that cannot be solved with normal turns.

## A Moment Of Reflection

The helicopter cube is actually quite easy to solve if it isn't jumbled. It's worth thinking about how the puzzle works before going any further. Start with the image below.

The dark grey pieces in the image are the ones which are turned through 180° when you do a UF turn (see notation below). The pieces you see coloured grey in this image are in fact the **only** ones that are moved with this turn. It's obvious that the corners swap and that they get twisted. The arrows show what happens to the centres.

The way that the pieces move is important, particularly the centres. There are 24 centre pieces in total. Each centre follows one of 4 **orbits**. An orbit is the list of positions that a piece can be in. On this puzzle the orbits contain 6 pieces. Pieces cannot be swapped between orbits with normal turns. Each of the orbits contains exactly one centre of each colour. If you have two of the same colour in a single orbit, the cube has been scrambled with jumble turns and then restored to a cube shape.

## Notation

Moves of the bottom layer are in the form DF, DR etc.

## Step 1 - Solve The Centres On One Face

The image shows what you are trying to achieve in this stage. You should be able to do this intuitively. Work on them one at a time. In the image below, looking at the puzzle in the direction of the arrow, you can do the algorithm to join two centres together.

**UR FR UR**

## Step 2 - Solve The Corners On One Face

In this step, you need to place the corners so the whole of one face is solved. You should be able to do this quite easily. If a corner is twisted when you place it, take it for a ride around the whole puzzle and try again.

## Step 3 - Place Centres For One Layer

The two centres marked pink in this image will need to have pieces which match up with the colours on the corner. This step is all about placing those centres so that whole of the first layer is solved. You can set up the situations shown in the images below by turning only on the bottom layer.

**DF FR DR DF DR FR**

**DR FR DF DR DF FR**

When you are finished with all 4 corners, your cube should look something like this,

## Step 4 - Bottom Layer Corners

Turn the cube over so the solved layer is now on the bottom. Your next job is to orient the bottom corners. As long as you only use UF, UR, UB & UL moves, you can't mess up the pieces you have solved. You should be able to do this, don't worry about the positions of the corners, just orienting them.

Once you have the corners oriented, you can place them using the algorithms shown,

**UF UB UL UF UB**

**UF UL UF UR UB UR UF UL UF**

## Step 5 - Solve Centres

This is the last stage of the solution. The aim is to place all of the centre pieces in their correct locations. There are 3 algorithms to use. Each one is longer than the previous. Start by seeing what you can solve with the first one before moving on. It is possible to end up with centres that can't be rotated into place using the second pair of algorithms. For that case, the third algorithm works a treat.

**UR UF UR UF UR UF**

**CW: UF FR UR FR UF FR UR FR**

**ACW: UR FR UF FR UR FR UF FR**

**UR FR UF UR FR UR FR UR FR UF FR UR**