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COL $ + at , AM ET Careers Investor Relations Worldwide Locations · Rockwell Collins – Building Trust Every Day. Search. Home. Hard Chromium Boeing SOPM , Messier-Dowty PCS, Repair limitations as contained in the. Plating. DCPM, AMS , QQ-C and. BAC , Boeing SOPM , MIL-A Type 1 or 1B, MIL-A Type 3, Safran Section Repair limitations as contained.

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Operational advantages are realized when these high- strength, high-heat-treated materials are used in limited-space envelopes. To reap the benefits of high-strength alloy steel components and avoid potential safety issues resulting from damage, airline maintenance and overhaul personnel need to follow proper maintenance procedures and rework practices, checklists, and guidelines during component maintenance and overhaul. M any landing gear, flap operators achieve the benefits asso- factors that cause damage in service track, flap carriage, and ciated with high-strength alloy steels or during overhaul.

Most can be other flap actuating components and avoid potential safety issues attributed to a lack of familiarity on Boeing airplanes are made of resulting from damage caused by with high-strength alloy steels. Other steels in maintenance or overhaul. These use, including 9Ni-4Co High- ment, and notch sensitivity, can strength alloy steels referenced lead to rapid crack growth in in this article generally have some load environments.

Benefits of high-strength Airline personnel should alloy steel. Importance of proper rework practices, checklists, inspection and rework. Guidelines for reworking these components. This will help high-strength alloy steel components. Standard Overhaul require less space to house than compo- during maintenance and overhaul are Practices Manual SOPM nents made of lower strength alloys.

SOPM – Definition by AcronymFinder

For repair of high-strength, M steel When properly maintained and parts on DC and MD airplanes, overhauled, high-strength alloy steel Airline personnel who participate in use CMM ; for DC-9, components demonstrate high levels of component rework, maintenance, and MD, MD, and airplanes, service reliability. Common techniques include for other uses. Improper rework practices can result detailed visual inspections and other in unscheduled maintenance or surface nondestructive inspection methods, The use of high-strength alloy steel damage that causes crack initiation.

See SOPMs and efficient aerodynamic surfaces and normal checks for wear and free play. Ultrasonic or eddy current providing the potential for increased inspections also may be useful for payload and fuel. High-strength alloy steels can ex- in situ inspections. Therefore, surface damage plemental, specialized techniques, high-strength alloy steel flap tracks, detection is important during overhaul such as the Barkhausen inspection, to flap carriages, and flap actuating com- and on components in service.

This technique can be used meeting or improving aerodynamic a C-check helps prevent conditions successfully to screen components with requirements. This also optimizes wing that can lead to crack initiation. For example, if an axle shape and reduces the potential need for best safeguard against corrosion is fractures as a result soom chrome-grinding bulging aerodynamic surfaces, which to ensure that finishes conform to the heat damage during manufacture or in turn reduces drag and increases design and that design improvements overhaul, the Barkhausen inspection airplane performance.

Spot face depressions typi- reworking high-strength alloy steel Boeing SOPM guidelines should be fol- cally are not filled with plating to components and describes some of lowed for the rework of any component restore the dimension but instead aopm the implications of improper slpm and for all types of plating or coating.

Rework or overhaul of components original design. The following are shot-peening on all reworked areas During component design, eliminating examples of stress concentrations that and permit complete seating of bush- or minimizing areas of stress concentra- can lead to cracking.

Special atten- tion is given to protective finish runouts Transitions or radii that are sharper Abrupt changes in sections, holes, adjacent to stress concentration details.

When removing and sharp-cornered keyways should In addition, all stress concentration damaged material from part surfaces be avoided. Finer surface fin- a part. Any rework or repair must not location or degrade the original design ishes also may be needed to eliminate increase stress concentrations that features.

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When locally machining out unnecessary stress concentrations, degrade component durability. Overhaul should reflect High-strength alloy steel components depression is necessary. This layer helps to boeeing that all discrepant material is trols that are not in accordance with removed and the original design design standards. There are few options to restore these completely stripped to replace nickel machined depressions to meet interface and chrome plating. One type of rework or these repairs involve rework of the crack growth caused by fatigue or overhaul, sulfamate-nickel plating, is base metal.

The new plating deposits stress corrosion. This diameter surfaces and outer cylinder will ensure that the restored plating When a surface is machined or inner diameter surfaces often are is of high quality and that it does not ground to remove damage, the filled with sulfamate-nickel plating terminate with an abrupt edge.

Through- reworked area should be shot-peened to restore them to dimensions that thickness cracks in chrome plate gen- with proper overlap onto the existing are suitable for subsequent chrome erally present where there is evidence shot-peened surface. During overhaul, plate application. Corrosion for overhaul, all evidence of corrosion Visual evidence of chicken-wire and pitting. As provided in CMMs, damage. Chicken-wire cracking noted the pit forms, and These edge, the techniques must be well con- grows through fractures may be caused by a combina- trolled to avoid damaging the adjacent the compressive tion of degraded protective finishes on base zopm.

Improper blending can layer, and the the truck inner diameter, poor drainage, remove the required shot-peened layer change in resid- and contact with the corrosive chemi- or create undercuts or grooves at the ual stress state cals bieing washing solutions or deicing edge of the plating that can cause and the pit compounds.

Truck fractures most often cracking in service. Several in-service fractures have cracking. This type of cracking most been attributed to improper plating often occurs on surfaces that are both Figures 4 and 5 show a drag brace technique, poor-quality plating, prone to corrosion and exposed to sus- from which corrosion was not removed improper runout conditions, and base tained tensile stresses while in service, completely during overhaul.

The part metal damage caused by poor blending such as the lower surface of landing gear was subsequently shot-peened, solm or machining control.

Proper use of special plating tech- This resulted in crack initiation boein niques, such as conforming anodes and Corrosion pitting also can lead to propagation while in service and the robbers, can control plating thicknesses fatigue crack initiation depending on eventual fracture of the component.

This can reduce the possi- the component, the location of pitting, bility of chrome chicken-wire cracking and cyclic loading conditions. In these Mechanical damage. Stress and poor runout details. The degree the protective finishes and alters the transition or undercut will create a of cracking tolerated before fracture compressive shot-peen layer.

This stress concentration that can cause varies by component, crack location, crack initiation. For example, figure 1 and component loading conditions.

Touching up damage to ac- FIGURE cessible enamel and primer in a timely manner can prevent the formation of corrosion pits and reduce the need for excessive rework during overhaul. Rework that requires low-hydrogen- embrittlement LHE cadmium stylus plating should be performed when the component is not loaded. Although high-strength alloy steels are FIGURE hard and resist dents, scratches, and nicks, stress concentrations caused by mechanical damage can dramatically reduce the service life of a component.

High-strength alloy steel components also can be damaged by mishandling during shop rework e. Possible mechani- cal damage to a high-strength alloy steel component should be evaluated by the operator and repaired as needed. If the damage is local and widespread deformations are not evident, repair may be similar to that required for corrosion and pitting. All deformed material boring be removed before refinishing; deformed high-strength steel alloy components must not be straightened.

Contact Boeing for assistance, if needed. After overhaul Overheating of components can change operations are completed, the compo- the original steel temper and mechani- FIGURE cal properties of the affected area. Any visible evidence of chrome plate distress can The degree to which the indicate the likelihood of base boeinb properties are changed depends on the tempera- metal heat damage.

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Figures 12 ture and duration of exposure. SOPM and Both conditions can be detected by a temper etch i. UTM indications show white and provide guide- during temper etch inspections and often are found within lines that indicate when patches of OTM, which show dark gray to black during temper chrome must be removed etch inspection. SOPM provides details about the during overhaul. Some heat damage is so Heat damage generally is severe that the heat-treat con- removed by carefully machin- ing the base metal.

Afterward, dition of material is altered in another temper etch inspection is done to ensure that the adjacent areas. This widespread boeinf did not create more heat damage. Figures 6 and 7 show nent cannot be salvaged. Axle service-induced heat damage on the inside diameter of a main gear outer heat damage caused by a wheel cylinder.

MAINTENANCE HIGH-STRENGTH – Boeing

This component developed extensive frictional heat damage boeig fracture may lead to in the upper bearing contact area such a condition. Shop procedures such as magnetic particle inspection and LHE cadmium stylus plating can cause arc burns if appropriate precautions are not maintained during processing.

Figures 14 and boeimg show a as a result of improper clamp-up. Salvage was mium plating. In this article, not possible. This dam- treat conditions of the base metal if age, which occurs on a more frequent the temperatures are below the original basis, is caused by vertical motion tempering temperature.

However, the against the lower bearing surfaces. This may result practice is to initiate baking as soon as crack or become brittle or discolored in a shorter than planned possible following a plating operation. Boekng Boeing The delay time between plating These situations often occur when for assistance with ques- completion and baking start typically is components are tions about repairing or salvaging observed.

The part is e. The infused during overhaul unless retained by hydrogen migrates to areas of high specific CMM requirements. When the component is installed avoid bushing-to-bore interface degra- on an airplane, this internal damage dation during bake cycles. Design fin- can lead to crack initiation and propa- ishes are restored and new bushings gation, resulting in component fracture.

These effects on the may be a candidate for salvage. The microstructural plating was not heated to the extent internal residual stresses are sufficient- anomalies resulting from cadmium that cadmium embrittlement would ly high to cause cracking even embrittlement can lead to component be suspected. Boeing can assist in before the part is installed.

If these alloy steel by cadmium, resulting components have been overheated, in cadmium diffusion into the steel salvage may not be possible. Solid-metal if high-temperature exposure was Second-Quarter — April. Some cleaners and chemicals may accelerate finish degradation and lead to corrosion.

This allows a thorough strip intensitythe surface should then before use in accordance with Boeing inspection of the base metal a primary be shot-peened to CMM requirements. All portions of a component determine whether a cleaner or coating, are restored to the original that are to be shot-peened should first chemical is detrimental to protective design requirements. This is addressed be completely stripped; no cadmium finishes or base metal.

However, in an all-model Boeing service letter residue should remain on the surface. Restoration of the shot-peened layer during over- haul is important to ensure that the shot-peen com- pressive residual stresses are main- tained or restored. FIGURE accomplish the intended task verified Discontinuous shot-peening can lead by the material provider or operator. All reworked surfaces must be specifies the materials for use in repair.