SIFT key terms

A picture made only of lines that shows an object's outline and main edges, with no shading or color. Simple Drawings items ask you to compare such figures quickly.

Turning a figure in your imagination by some angle without changing its shape or proportions, so you can judge whether two drawings show the same object.

The reversed copy of a figure made by flipping it left to right or top to bottom. A mirror image is not the same thing as a rotated copy.

How quickly and correctly you can compare and match visual shapes. On timed items, fast simple comparisons score better than slow, overly careful ones.

A drawing that looks almost like the target but differs in one detail, such as a missing line or a changed angle. Spotting that small difference is the task.

A simple shape drawn inside a busier pattern so its outlines merge with the surrounding lines. You must trace the shape out of the clutter.

The ability to separate a target shape (the figure) from the background pattern (the ground) when both are drawn in similar line weight.

Mentally filling in gaps so a partly hidden or broken outline is still seen as a complete shape. Hidden Figures items often require it when the target's lines are interrupted.

The control stick in a helicopter. Moving it tilts the whole rotor disc, which changes the direction and size of thrust so the aircraft climbs, dives, or moves sideways.

The lever, usually at the pilot's left, that changes blade pitch on all main rotor blades at once, raising or lowering total lift without tilting the disc.

Foot controls that vary tail rotor thrust to swing the helicopter's nose left or right and to hold heading against main rotor torque.

Extra lift a helicopter gains as forward airspeed carries it out of its own downwash into clean air, making flight more efficient and reducing the power needed.

A powerless descent in which air flowing up through the rotor keeps the blades turning, letting the pilot glide and cushion the landing with a flare.

Loss of lift on the blade moving backward relative to the airflow. It appears at high forward speed or high load and causes the nose to pitch up and the aircraft to roll.

Unequal lift on the advancing and retreating halves of the rotor disc because each blade meets a different airspeed. Blade flapping and pitch changes even it out.

Extra lift and lower power demand when a helicopter hovers within about one rotor diameter of the surface, where the downwash is slowed and thrust becomes more effective.

The fuselage's tendency to rotate opposite to the main rotor, since the engine turns the rotor one way and the body the other. Tail rotor thrust or pedals correct it.

The angle between a blade's chord line and the relative wind. Raising it increases lift until the stall angle, past which lift falls sharply.

An instrument that shows pitch and bank against a fixed horizon symbol, so a pilot can read climb, dive, and turn from the display alone.

The reference line dividing sky from ground on an attitude display. Nose position and wing tilt are judged against it.

How far the wings are tilted from level, measured in degrees. On the display it is the angle between the wing line and the horizon.

The nose-up or nose-down angle of the aircraft relative to the horizon, read from where the nose sits above or below the horizon line.

The direction the nose points, usually stated in degrees clockwise from north. Turn questions ask what heading results after a given turn.

The central point a passage is built around. Every paragraph supports or explains it, so it is broader than any single fact in the text.

A conclusion that follows from what a passage says even though the passage never states it outright. It must be supported by the text, not by guesswork.

A specific fact, example, or reason inside a passage that backs up the main idea or answers a question about who, what, when, or why.

The writer's attitude toward the subject, revealed through word choice and sentence style rather than stated directly. Words like 'fortunately' or 'reckless' signal it.

Words or phrases near an unfamiliar term that hint at its meaning, such as a definition, an example, or a contrast with something else.

A comparison of two quantities by division, written like 3:4 or 3/4. It tells how much of one quantity exists for each unit of the other.

An equation saying two ratios are equal. Setting one up lets you scale a mixture, a map distance, or a recipe up or down.

The agreed sequence for evaluating an expression: parentheses, then exponents, then multiplication and division, then addition and subtraction, working left to right within each step.

The average of a set of numbers: add all the values together, then divide by how many values there are.

A ratio that compares quantities with different units, such as miles per hour, dollars per gallon, or words per minute.

Changing a measurement into a different unit by multiplying by a fraction that equals one, such as 12 inches over 1 foot.

A rigid bar that pivots on a fulcrum. Effort applied at one point moves a load at another, and the distances from the fulcrum set the mechanical advantage.

How many times a machine multiplies the effort you put in. It equals output force divided by input force, and extra force always comes at the cost of extra distance.

The number of teeth on the driven gear divided by the number on the driving gear. It sets the trade-off between turning speed and turning force.

Resistance to sliding when two surfaces touch. It turns some motion into heat, so part of the effort in any machine is wasted overcoming it.

Force spread over an area, such as pounds per square inch. The same force acting over a smaller area produces a higher pressure.