Aircraft Maintenance Standard Practices

Removal of components and accessories

Protect components and accessories against mechanical contact with metallic tools before removal.
Protect openings with clean covers/caps, as required during removal of a component or accessory.
Protect the electrical connections when electrical systems are disconnected.
Protect all protruding ends such as the gearshafts and connections when removing components.

Use two wrenches to remove or install the tube coupling nuts: one wrench to hold the union, and one to loosen or tighten the coupling nut. This prevents damage to the parts.
Record the type and the serial number before installing a component.
Visually check the general condition of the component and ensure that it has not sustained any damage before installation.
Check that the mounting faces and the seal grooves are clean and not deteriorated.
Remove all the covers/caps installed to protect the openings.
Use only the tools designed specifically for the operation.
Check that the threaded sections protrude by one thread relative to the nuts and chamfers at completion of the final torquing.
Comply with all the tightening torque values specified in the relevant sequence of operations.
Use the gloves to handle bearings and any other parts prone to oxidation.
Cold shrink installation of bearings (chilling in liquid nitrogen or any other medium) is strictly prohibited.

Do not remove the seals with a sharp or pointed tool (knife-blade or a scriber) which could cause damage to the surface of the parts.
Lubricate the seals with lubricants recommended in the installation procedure.
Apply a light layer of engine oil to the O-rings.
If you apply too much lubricant, you can prevent the correct seal installation and can cause contamination.
Use only new seals and rubber items during installation operations.
Make sure the seals are in good condition and free from cuts or gouges.
During the seal installation, be careful to install the seal correctly.
Make sure the seal groove (recess) is free from sharp edges.
For O-rings that must be installed over threads or splines, you must use a conical sleeve, without burrs or sharp edges, to prevent damage to the seal.
Continued use of the gaskets – These are not permitted.
- Examine for nicks, cuts, gouges or openings across the surface of the seal material.
- Examine for hard or britted seal material.
- Examine the surface of the seal material for deformation that could cause a blockage of the seal.

Verify that the orientation of the gasket is checked and verified before installation.
Always install the gasket independently, and never by placing it on the face of the other component to be installed.
After placement of the gasket and the mating component, the installation has to be properly supported by hand or by the installation jig or equipment to prevent uneven force on the gasket face, which shall damage the embedded seals or the plate as a whole.
Every hardware after the gasket and component placement shall be installed individually i.e, washer first and then the nut (if this is the combination of installation). If it is the bolt and washer, place the washer on the bolt and install the bolt.
After the initial installation of the hardware, cross verify the placement and installation before proceeding for the tightening and torquing sequence (in inaccessible areas usage of inspection mirror (dentist mirror) etc., are advised.

When tightening nuts, specified torque values must be applied. These torque values are given to ensure an optimum tightening for safety purposes.
On flanges where there are a great number of bolts and nuts, the tightening sequence must be performed in pairs of bolts diametrically opposed.
On these same flanges, it is recommended to proceed to a final check, clockwise, to ensure that all the nuts have been tightened to the specified torque values.
Tighten at a uniform rate until the specified torque is obtained. In some cases, where gaskets or other parts cause a slow permanent set, be sure to recheck the torque at the desired value after the material is seated.
Do not tighten to the final torque value during the first draw-down; uneven tension can cause distortion or over-stressing of parts. Seat mating parts by drawing down the bolts in gradual increments until the parts are firmly seated. Complete the tightening procedure by loosening each fastener separately, then tighten to the specified torque value. Do not exceed the maximum torque values specified by this manual.

Tighten at a uniform rate, in a criss-cross sequence if necessary, to the specified torque value.
Loosen by 1/4 to 1/2 turn, and re-tighten, one by one in sequence to the specified torque value. Do not tighten more than the specified torque value.
Clean unwanted lubricant, if necessary.
Make sure that you get the specified torque value with the torque wrench already used.