What does 'elevator rigging' mean for aircraft?

Question

What does 'elevator rigging' mean for aircraft?

Answer 1

You have to rig the evevator cables to the elevator and the control wheel/stick/yolk.  The controls need to be all the way back when the elevator is fully up to the stops.  The rudder and elevator need to be rigged to hit the stops when the pedals and controls are fully deflected in small airplanes.  Larger airplanes its hydraulic and thats a WHOLE nother world.

Answer 2

Rigging for an aircraft means the adjustment of a system to meet its designed movement characteristics.

The rigging of the elevator system on a modern commercial aircraft is to ensure that the elevator is in the neutral position when the yoke or side stick in the cockpit is centered. As the yoke or side stick is moved through its full range of movement so should the elevator. Any deviation or mis alignment must be adjusted.

Elevators or any flight control system must be rigged after work has been carried out on that system.

On older generations of aircraft with a mechanical control system. The cables are adjusted in length to raise or lower the elevator according. Stops within the yoke can be adjusted to control the maximum movement.

On fly by wire systems such as the A320 family the yellow/green hydraulic actuator is rigged followed by the blue hydraulic actuator to ensure both systems are symmetrical and work together, and you must ensure the computers on the aircraft are recording the correct amount of movement.

The process used in elevator rigging is also used for aileron and rudder rigging.

Answer 3

In mechanical push/pull systems for operating the elevators, where flexible cables are used; the attachment of the cables at the control cloumn and elevator, routing of the cables and centering the system is collectively known as 'elevator rigging'.

Answer 4

hey averifan, flexible cables are used in "push/pull" mechanical systems now? thought those were where push/pull rigid aluminum tubes were used. how does a flexible cable push anything?

Answer 5

it could mean the assembly of pulleys, wires, mounts to move the elevator with the control column

or--

it means rigging, adjusting, making sure that the assembly of pulleys, cables, mountings are all properly adjusted to the required tension so that when the yoke is moved, the elevator moves to the corresponding position.

there have been cases where the tension and the adjustments were wrong and the aircraft's elevator could only pitch up a few degrees but could pitch down by more than 20.

Answer 6

If you are not familiar with aircraft flight controls please keep reading and I will try and explain it for you.

Assembly and rigging must be done in accordance with the requirements prescribed by the aircraft manufacturer. These procedures are usually detailed in the applicable maintenance or service manuals. The Aircraft Specification or Type Certificate Data Sheets also provide valuable information regarding control surface travel.

The rigging of control systems varies with each type of aircraft; therefore, it would be impracticable to define a precise procedure. However, certain principles apply in all situations . It is essential that the aircraft manufacturer's instructions be followed when rigging an aircraft.

Control surfaces should move a certain distance in either direction from the neutral position.  These movements must be synchronized with the movement of the cockpit controls.  The flight control system must be adjusted (rigged) to obtain these requirements.

Generally speaking, the rigging consists of the following: (1) Positioning the flight control system in neutral and temporarily locking it there with rig pins or blocks, and (2) adjusting surface travel, system cable tension, linkages, and adjustable stops to the aircraft manufacturer's specifications.

When rigging flight control systems, certain items of rigging equipment are needed. Primarily, this equipment consists of tensiometers, cable rigging tension charts, protractors, rigging fixtures, contour templates, and rulers.

Measuring Cable Tension

To determine the amount of tension on a cable, a tensiometer is used. When properly maintained, a tensiometer is 98% accurate. Cable tension is determined by measuring the amount of force needed to make an offset in the cable between two hardened steel blocks, called anvils. A riser or plunger is pressed against the cable to form the offset. Several manufacturers make a variety of tensiometers, each type designed for different kinds of cable, cable sizes, and cable tensions.

Surface Travel Measurement

The tools for measuring surface travel primarily include protractors, rigging fixtures, contour templates, and rulers. These tools are used when rigging flight control systems to assure that the desired travel has been obtained.

Protractors are tools for measuring angles in degrees. Various types of protractors are used to determine the travel of flight control surfaces. One protractor that can be used to measure aileron, elevator, or wing flap travel is the universal propeller protractor. Notice that this protractor is made up of a frame, a disk, a ring, and two spirit levels. The disk and ring turn independently of each other and of the frame. The center spirit level is used to position the disk when measuring control surface travel. A disk-to-ring lock is provided to secure the disk and ring together when the zero on the ring vernier scale and the zero on the disk degree scale align.

ADJUSTMENT OF CONTROL SURFACES

In order for a control system to function properly, it must be correctly adjusted. Correctly rigged control surfaces will move through a prescribed arc (surface-throw) and be synchronized with the movement of the cockpit controls.

Rigging any system requires that the step-by-step procedures be followed as outlined in the aircraft maintenance manual. Although the complete rigging procedure for most aircraft is of a detailed nature that requires several adjustments, the basic method follows three steps:

(1) Lock the cockpit control, bellcranks, and the control surfaces in the neutral position.

(2) Adjust the cable tension, maintaining the rudder, elevators, or ailerons in the neutral position.

(3) Adjust the control stops to limit the control surface travel to the dimensions given for the aircraft being rigged.

The range of movement of the controls and control surfaces should be checked in both directions from neutral.

The rigging of the trim tab systems is performed in a similar manner. The trim tab control is set to the neutral (no trim) position, and the surface tab is usually adjusted to streamline with the control surface. However, on some aircraft the trim tabs may be offset a degree or two from streamline when in the "neutral" position. After the tab and tab control are in the neutral position, adjust the control cable tension.

Pins, usually called rig pins, are sometimes used to simplify the setting of pulleys, levers, bellcranks, etc., in their neutral positions. A rig pin is a small metallic pin or clip. When rig pins are not provided, the neutral positions can be established by means of alignment marks, by special templates, or by taking linear measurements.

If the final alignment and adjustment of a system are correct, it should be possible to withdraw the rigging pins easily. Any undue tightness of the pins in the rigging holes indicates incorrect tensioning or misalignment of the system.

After a system has been adjusted, the full and synchronized movement of the controls should be checked. When checking the range of movement of the control surface, the controls must be operated from the cockpit and not by moving the control surfaces. During the checking of control surface travel, ensure that chains, cables, etc., have not reached the limit of their travel when the controls are against their respective stops. Where dual controls are installed, they must be synchronized and function satisfactorily when operated from both positions.

After determining that the control system functions properly and is correctly rigged, it should be thoroughly inspected to determine that the system is correctly assembled, and will operate freely over the specified range of movement. Make certain that all turnbuckles, rod ends, and attaching nuts and bolts are correctly safetied.