Assy Rigging

04/10/23 Author: Harry L. Whitehead 1

AVAF 209 -AVAF 209 -IV. Assembly and RiggingIV. Assembly and Rigging

AVAF 209 -AVAF 209 -IV. Assembly and RiggingIV. Assembly and Rigging

A. Rigging Specifications

B. Airplane Assembly

C. Flight Control Systems

D. Control Surface Balancing

E. Biplanes


Rigging SpecificationsRigging Specifications

Should check “Rigging” during all required inspections and anytime any control or major assembly (I.e. wing) is removed and reinstalled

“Rigging” = check systems and control surface travel and adjust as necessary

Test fly aircraft after reinstallation and adjust as necessary

IV. Assembly & Rigging Rigging Specifications Airplane Assembly Flight Control Systems Control Surface Balancing Biplanes



Type Certificate Data Sheets (or Aircraft Specifications) are best source

Is most accurate for details

Includes:–Leveling means–Control surface travel–Weight and balance information




Manufacturer’s ManualsGive installation and procedures

Don’t believe the details, go to the TCDS

MM usually cover more than one model or Ser. No. range = details may not be accurate for your specific aircraft



Airplane AssemblyAirplane Assembly

Most airplanes are fully cantilever or with a minimum of external bracing so assembly is pretty straight-forward

Follow manufacturer’s instructions




General Assembly procedures:






Level fuselage–Laterally and longitudinally–Inside hangar to minimize wind currents

If must be outside = point into windUse manufacturer’s level point(s) and plumb bob or spirit level





Install wings and torque boltsInstall Hor. Stab. And Vert. Stab. And torque bolts





Perform Alignment Check (next area)

Install movable control surfaces

Install and rig control systems

Test fly to verify control responses and flight stability/attitude



Alignment Check:


Wings•Most modern wings have very little adjustments available•Usually only angle of incidence

•Wing mounting bolts are on eccentric bushing or serrated bushings

•= rotate to change angle



Alignment Check:


Wings

•May need to use special Incidence Board or just Universal Propeller Protractor for initial settings•Either must be installed at manufacturer specified location



Alignment Check:


Wings with V-struts:•Piper Tri-Pacer, Piper Cub

•Can usually adjust Dihedral and Angle of Incidence•Procedure

•Level fuselage laterally & longitudinally•Check and adjust Dihedral



Alignment Check:



•Check and adjust Dihedral•Use Dihedral Board•Position at manufacturer specified position•Adjust length of struts until bubble is centered



Alignment Check:



•Check and adjust Dihedral•Some aircraft use string stretched between the wingtips at specified chord location•Adjust struts to get specified dimension between string and wing root



Alignment Check:



•Check and adjust Angle of Incidence•Use Incidence Board or just measure angle with Prop Protractor or Protractor Head of Combination Square•Adjust Rear strut to get proper angle



Alignment Check:


Engines•Use manufacturer’s specs.•Usually parallel to longitudinal axis•Mounts usually just bolt on with no adjustment provisions

•Be sure to use proper shimming (washers), bolts, torques, etc. as specified



Alignment Check:


Empennage:•General

•Most are cantilever with fixed positions•Insure all bolts are proper Part Number and torqued in proper sequence so is not cocked

Author: Harry L. Whitehead 20


Alignment Check:


Empennage:•If Wire-Braced

•Uses Streamlined wires so insure have proper tension (use Datum Board) and is flat with airflow (decreases vibrations and drag)•Must replace streamlined wires with streamlined wires only

•DO NOT use round cable as replacement = vibes and different expansion rates



Alignment Check:


Empennage:•Check Hor. Stab. Dihedral & Angle of Incidence

•Basically same as wings•May or may not be adjustable



Alignment Check:


Empennage:•Check Vert. Stab. (Fin) Verticality

•Measure from like points on both Hor. Stabs. and should be equal measurement•Fin may be offset slightly to compensate for Spiraling Slipstream



Alignment Check:


Empennage:•If suspicious, run string through control hinges

•Should be able to be centered in all hinges•If not = hinges are misaligned and will bind control movement•NOTE: applies to all control surface hinge lines, not just empennage



Alignment Check:


Symmetry Check:•To insure entire aircraft is aligned properly (is Symmetrical)•Measure between specified points on aircraft•Use steel tape with 5 pound pull (for consistency)•Like measurements should be equal within manufacturer’s tolerances•May need to use plumb bob from points, mark on floor, and then measure (especially large aircraft)



Flight Controls Installation & Rigging:


Ailerons:•Be sure to only use manufacturer’s parts combinations and torque specs to prevent binding

•Should be free to pivot with no binding and no looseness





Ailerons:

•System:•Stick or wheel connected to cables





Ailerons:

•System:•Up cable goes to each aileron•“Through” or “Balance” cable connects down side of both ailerons

THROUGH CABLE

UP CABLES





Ailerons:

•System:•Stick or wheel connected to cables•Up cable goes to each aileron•“Through” or “Balance” cable connects down side of both ailerons





Ailerons:

•System:•To combat adverse yaw = differential travel•Also use Frise ailerons•Also some use Rudder-Aileron Interconnect Spring(s)

•When wheel/stick is moved = also moves rudder in appropriate direction to combat adverse yaw





Ailerons Rigging:•Install all cables and check and adjust tension (most are cable systems)

•Lock in neutral position first•Put clamps or control locks on stick/wheel•Put clamps or battens on control surfaces•Some have holes for Rigging Pins to go into to hold in neutral position





Ailerons Rigging:•Check and adjust travel

•Remove locks•Use Prop Protractor, Control Surface Protractor, or Protractor Head of Combination Square•Check up and down movement as specified in TCDS



Alignment Check:


Ailerons Rigging:

Prop Protractor Review

Propeller Protractor



Alignment Check:


Ailerons Rigging:





Alignment Check:


Ailerons Rigging:

Control Surface Protractor:•Adjust disk to zero when surface is in neutral•Move surface to limits and read angle at pointer






•Adjust stops at ailerons•Make sure they hit the stops at ailerons before running out of stick/wheel movement•Should have small amount of movement of stick/wheel left to give pilot “springback” feel or “cushion” so he/she knows they’re at end of travel





Ailerons Rigging:






•Some are “Drooped”•When in neutral position = trailing edges are slightly lower than wing or Flap trailing edges (must be equal droop on each wing)•During flight = ailerons are forced to streamlined position to take up any slack or wear in system (mostly cable systems)





Ailerons Rigging:•After adjustment

•Move stick/wheel through entire range of movement

•Check for ease of movement, no binding, hits stops at aileron first, and AILERONS MOVE IN PROPER DIRECTION

•Check entire system for proper installation (pulleys, cables, bolts, safeties, etc.)





Flaps:

•System:•Actuated by mechanical handle or electrical

•Handle manually positioned by pilot and connected to cables•Electric switch connected to reversible motor in wing which is connected to cables

•Both sides connected to same cables to insure equal extension and retraction





Flaps Rigging:•Generally same as ailerons•Lock in retracted position

•Adjust cable tension•Check and adjust travel as per TCDS

•Hit stops at flaps first•BOTH MUST EXTEND EQUALLY!

•If different = extreme roll force•Check indicator system matches flap movement and positions





Elevators:

•System:•Wheel/stick connected to cables•Cables go through belly to bellcrank on or near Elevator





Elevators:•System:

•Most modern airplanes can be loaded with CG too far aft•Lots of seats, baggage compartments in back, etc.

•When this airplane is slowed down for landing:•Trim tab working hard to keep nose down with Elevators in slightly down position•If turbulence = Trim Tab may loose effectiveness = Elevators streamline = nose pitches up and trim tab can’t compensate = possible stall





Elevators:

•System:•Down Spring in system puts load on Elevator working against Trim Tab•If turbulence causes loss of trim tab effectiveness = Down Spring pulls Elevator down to keep nose down until Trim tab can take over again





Elevators:•Rigging generally same as ailerons•Lock in neutral

•Trailing edge in line with Hor. Stab. trailing edge•Clamp wheel/stick and elevator

•Adjust cable tension•Adjust travel•Check operations and system for problems





•System:•Wheel/stick connected to cables very similar to Elevator except connects to counterweight (or Balance Arm) on front of stabilator inside fuselage

Stabilators:





Stabilators Rigging:•Rigging generally same as others•Lock in neutral

•Must use stabilator rigging tool similar to incidence board to find neutral

•Adjust cable tension•Adjust travel•Check operations and system for problems





Rudder:

•System:•Cables connected to pedals and through belly to rudder •On Tricycle gear aircraft = also connect to Nose Wheel steering mechanism





Rudder Rigging:•Generally same as others•Lock in neutral

•Clamp pedals





Rudder Rigging:•Generally same as others•Lock in neutral

•Clamp pedals•Clamp rudder in line with Vert. Stab.

•Adjust cable tension





Rudder Rigging:•Adjust travel

•Can’t use bubble type protractors•Measure distance moved from specified point

•May need to make drawing protractor•Or measure distance from hinge to trailing edge (= radius of movement), calculate circumference of movement, divide by 360, multiply by necessary degrees of travel, measure travel

•Check operations and system for problems





Control Tabs:•Typical System (Aileron):

•Control wheel in cockpit•Turns cable drum or chain sprockets connected to cables •Includes position indicator mechanism





Control Tabs Rigging:•Generally same as others•Lock in neutral

•In line with control surface installed on•Adjust cable tension•Adjust travel•Check operations and system for problems•Check indicator for proper operation•Insure is moving in proper direction





Final Check:•Test fly and readjust as necessary to fly “hands off” at cruise and most common loading•If flying with constant bank (“heavy wing”)

•Need to adjust angle of incidence of wing(s)•Need to “Wash IN” heavy wing by INcreasing angle of incidence on low side

•Turn rear bolt (if serrated or eccentric)•shorten rear strut length

•Could also Wash Out light (or high) wing





Final Check:•If in sideslip = rudder

•Reset in-flight adjustable trim tab or bend fixed trim tab to compensate

•If nose low or high = elevator•Reset trim tab(s) accordingly

•All are Trial and Error adjustments so re-test fly to verify and keep trying until it’s right



Flight Controls Systems:


Cable Systems:•Types of Cable

•CRES or carbon steel•Carbon steel cheaper and stronger

•Preformed•Must be at least 1/8 inch diameter for Primary Controls






•Non-flexible•1x7 or 1x19•1 strand of 7 or 19 wires•Only for straight runs with no change in direction






•Flexible•7x7

•Straight runs or with large pulleys for small direction changes

•7x19 (formerly Extra Flex.)•Use on any system•Is most common






•Also:•3 x 7

•only used on very small cable runs for non-critical applications•usually only for control surface position indicators

•6 x 19•for larger than 3/8” diameters






•Nylon-coated•Made by extruding a nylon coating over CRES cable•Increases service life as keeps clean and less vibration (= less work hardening)






•LockClad•On some older aircraft for high altitude flight•Is regular cable surrounded by Aluminum tube swaged on entire length•Temperature affects length less





Cable Systems:•Termination

•Woven•Army-Navy 5-tuck splice or Roebling Roll•Very time consuming to make•Only produce 75% of cable strength






•Nicopress•Copper sleeves squeezed onto cable•Squeezes:

•1. Center•2. Terminal end•3. Cable end

•Check with Go-NoGo gauge•Develops 100% of cable strength






•Nicopress•Can use 2 sleeves in series for splice = also 100% of cable strength•Be sure to place slippage mark on edge of sleeve(s) and cable when done






•Swaged•Most common•Terminal Swaged (squeezed) onto cable•Develops 100% of cable strength






•Swaged•Use Go-NoGo gauge to check•Apply slippage marks after






•Proof Load Test•After assembly•Pull with 60% of cable strength

•see AC 43.13-1B for strengths•Apply gradually and hold for 3 minutes•OK = no slippage in terminal(s)






•Proof Load Test•After assembly•Pull with 60% of cable strength•Apply gradually and hold for 3 minutes•OK = no slippage in terminal(s)

From AC 43.13-1B





Cable Systems:•Cable Inspection

•Inspect for wear, corrosion, breakage, distortion, or any damage

•Some damage is hidden = should periodically remove cable and inspect thoroughly

•Especially look at where passes over pulleys or through fairleads or within 1 foot of swaged-on terminal






•Wear•Replace when is worn 40-50% of outer wires

•Visual to see if wear of wires is blending together = 40-50%•Gaps between wires = excess of 50% wear and must be replaced






•Don’t confuse wear with manufacturer’s splice•Splice OK






•Wear•If LockClad or Nylon Coated

•Replace if outer cover is worn through






•Damage or Corrosion•Pass rag over length and will snag on broken wires•DON’T USE HAND!






•If suspect = remove and bend in loop to make broken wires stand out = replace






•Damage or Corrosion•Corrosion is especially prevalent in battery compartments, lavatories, wheel wells•Anywhere a concentration of vapors, fumes or liquids can occur•Exterior corrosion is not bad but probably also has internal corrosion = replace






•If cable is kinked or twisted wrong•Replace as wires/strands will not return to original position and strength is less

•Make sure no splice is closer than 2 inches to any pulley or fairlead





Cable Systems:•Other Components:

•Pulleys•Are phenolic with sealed bearings

•No lubrication necessary•Replace if bearing is rough or dry

•Use for direction change over 3o






•Pulleys•Check for wear patterns•Periodically rotate any which don’t normally rotate much = loosens and evens wear






•Pulleys•Make sure cable or pulley guards are used to help keep cable on pulley






•Fairleads•To prevent cable chafing on structure•Maximum deflection allowed is 3o

•Phenolic, plastic, or nylon (= soft material) so fairlead wears instead of cable

Author: Harry L. Whitehead 90





•Pressure Seals•Used on pressurized aircraft where cable passes through pressure vessel•Are filled with special grease and shaped so cable passes through but not air pressure•Inspect for proper lube and insure all snap rings are in place (or might jam cable)






•Cable Connectors•Some aircraft use spring-loaded “quick disconnects”•Allows “quick” removal of cable section for inspection and/or replacement






•Bellcranks and Quadrants•Bellcranks transmit lateral movements

•Increase range or mechanical advantage in system






•Bellcranks and Quadrants•Bellcranks transmit lateral movements

•Increase range or mechanical advantage in system

•Quadrants convert cable to push-pull movement





Cable Systems:•Travel Adjustment & Tension:






•Tension varies with temperture as Aluminum structure changes size more than steel cable






•Some aircraft have chart to give proper tension (in pounds) for the ambient temperature at time of checking•Small aircraft usually give range of acceptable tensions (for flexibility of temperatures)






•Use Tensiometer to check tension•Make sure Riser is proper for cable size•Hook on cable in middle of as long a run as is accessible•Squeeze trigger and read scale






•Use Tensiometer to check tension•Use chart to convert scale reading to pounds of tension






•Use Tensiometer to check tension•Some large aircraft use automatic tension devices

•Keeps tension constant regardless of temperature






•Use Turnbuckles to adjust•Has threaded ends into barrel•One end is left hand thread, one end is right hand thread = turn barrel to change overall length•Barrels available in short and long versions to give some flexibility in installations






•Use Turnbuckles to adjust•Don’t lube threads•Must have no more than 3 threads sticking out of barrel or 4 threads into barrel when properly tensioned•Safety with wire or clips





Push-pull Systems:

•General:•Uses all direct mechanical linkages instead of cables•Overall has less play or slop in systems than cable





Push-pull Systems:





Push-pull Systems:•General:

•Uses seamless Aluminum tubes•Each end has fitting

•Usually riveted into tube•Have replaceable bearing (rod ends) or fork•If replace make sure Witness Hole (Check Hole) is blocked

•Can’t put wire through•Insures enough threads are engaged





Push-pull Systems:•General:

•Inspect for condition carefully•Dents, scratches, gouges, etc. in tube bad as is thin walled and will then crack or fail easily (= monocoque structure)•Check bearings/rod ends for wear

•Small amount in each = large amount in system





Push-pull Systems:

•Bellcranks, Torque Tubes:•Systems use Bellcranks and Torque Tubes to change motion directions or convert from lateral motion to rotary motion





Push-pull Systems Rigging:•Rigging usually accomplished by adjusting the length(s) of various tubes in the system•Needs to be checked anytime any tube or rod end is replaced or any control surface is replaced





Push-pull Systems Rigging:•Installation of tubes:

•Center rod ends in forks and tighten check nuts•Allows tubes to rotate slightly during ops with minimal damage to rod ends and forks





Push-pull Systems Rigging:•Installation of tubes:

•If installing on a bolt or stud•Put open end of rod end away from structure or put large area washer under nut•If bearing comes out of rod end = won’t disconnect tube completely



Control Surface Balancing:


General





General

•If surface is out-of-balance = flutter or buffeting of surface = control problems, uncomfortable ride, premature and extreme wear •Need to check after repairs or painting





General

•Basically we want the Moments fore and aft of the surface hinge line to be equal

•Think Weight and Balance with the hinge line as CG

•Generally adjusted by adding weight forward of the hinge line as most repairs and paint are aft





Procedure

•Balance is checked and adjusted Statically•= the surface is not in motion

•The surface is removed from the aircraft and installed on a balance fixture using the hinge bolts

•Usually 2 knife-edges •Must be level and in draft-free environment





Procedure





Procedure

•All trim tabs should be in a neutral position•The surface must be level





Procedure

•Measure whether is Overbalanced or Underbalanced and how much

•Overbalance = chord angles down at the leading edge (nose heavy)•Underbalance = chord angles down at the trailing edge (TE heavy or nose light)•Generally want surface to be somewhat Overbalanced





Procedure

•Measure whether is Overbalanced or Underbalanced and how much

•Manufacturer will give figures and formulas to determine value•Need to measure force and calculate moment (like Wt. & Bal. problem)•May need special tool (like Cessna 310)





Procedure

•If necessary to add weight, only do so at specified locations and check again after

Assy Rigging

Business

Transcript of Assy Rigging