Preliminary Requirements

Procedure

1. SUBTASK 70-02-04-200-001 Abnormal Operational Circumstances - Engines and Engine Parts Which are Not Satisfactory for Continued Aircraft Use

   NOTE

   It is possible for an aircraft to be damaged too much to be repaired, but with no damage to the engines. In such incidents the engines and engine parts are "Not Included" in the Abnormal Operational Circumstances.

   1. International Aero Engines AG have specified that engines and engine parts, used during the incidents that follow, are not satisfactory for continued aircraft use:

      1. Engines and engine parts installed in an aircraft which was fully damaged by fire.

      2. Engines and engine parts which were burned in a fire so that the outer cases changed color, or became twisted. Also, other internal or external heat damage, to large areas.

      3. Engines and engine parts installed in an aircraft, which was fully damaged when it hit something.

2. SUBTASK 70-02-04-200-002 Abnormal Operational Circumstances - Engines and Engine Parts Which Will Possibly be Satisfactory for Continued Aircraft Use

   1. International Aero Engines AG have specified that engines and engine parts, used during the incidents that follow, will possibly be satisfactory for continued aircraft use:

      1. Engines and engine parts that were in an accident, in which the nacelles and engines were not damaged.

      2. Engines and parts that were in a fire, where a part of the aircraft was damaged, but the engines were not damaged by the fire.

      3. Engines and engine parts that were in an accident, but where the engine can turn freely, although the cases and other parts are damaged where they were hit.

      4. Damaged engines which will not turn freely, because of light damage to the cases or other parts.

      5. Engines that were fully, or not fully, soaked in clean or salt water for a short time only.

   2. Conditions that can be accepted for engines or engine parts specified in step A:

      1. NOTE

         Owners who can not do the necessary tests, or do not know if they are to accept or reject a part, can go to International Aero Engines AG for aid.

         Engines and engine parts that were used during the incidents specified in Step and Step are "Not Included" in the Abnormal Operational Circumstances.

      2. Engines and engine parts that were used during the incidents specified in Step to Step must be fully disassembled for inspection. Refer to Step, for the general instructions to be used with the FAA approved instructions.

3. SUBTASK 70-02-04-200-003 Dangerous Operational Incidents

   1. NOTE

      International Aero Engines AG permit some engines and engine parts, used during dangerous operational incidents, to be accepted for continued aircraft use if the conditions specified are obeyed.

      NOTE

      A single fan blade that breaks, outboard of 50 percent span, can cause different levels of engine damage. Refer to the Engine Manual for bird or object entry inspection procedures and damage limits. In general, the inspection procedures that follow will apply to incidents where a single fan blade has broken outboard of 50 percent span.

      A single fan blade break, outboard of the part span shroud:

      1. Examine for signs of entry into the core.

      2. Examine the fan rub-strip for damage that is more than the specified limits.

      3. Examine the fan exit guide vanes for damage.

      4. Examine the engine externally, for brackets and case flanges that are broken or have cracks.

      5. NOTE

         When a single fan blade breaks, inboard of 50 percent span (Or more than one fan blade breaks), it causes too much rotor vibration. A full inspection, with a disassembled N1 rotor module will then be the minimum inspection procedure necessary. More parts can then be disassembled, if found necessary, as a result of the initial inspection procedure.

         Examine the compressor with a boroscope, for too much blade tip rub and blade-to-vane clash.

   2. A single fan blade break, inboard of 50 percent span, or more than one fan blade breaks:

      1. Discard the N1 rotor main shaft bearings and the N2 rotor main shaft roller bearings.

      2. Examine the N1 rotor shaft (Front compressor turbine drive shaft), for rub with the N2 rotor shaft.

      3. Examine the cases, the bearing supports and the fan ducts, for distortion and cracks, specially at the engine mount locations.

      4. Examine the chip detectors and main oil filter.

      5. Examine the gearbox mounts.

      6. Examine all external components, tubes and wires for cracks and wear damage.

      7. Make a visual and boroscope inspection of the modules, that are not disassembled, for object entry damage, too much blade tip rub or blade-to-vane clash.

   3. Heavy damage to engine modules and assembled groups:

      1. Broken primary rotary parts:

         1. Different types of damage can result from broken compressor or turbine blades. As a minimum procedure, the damaged module must be disassembled for inspection. Also a full visual and boroscope inspection must be made of those modules which were not disassembled. The other modules must also be disassembled if damage to the gas path, or spatter on parts in the hot areas, are found. If the broken blade is a result of object entry damage, the forward modules must also be disassembled. This is to find all upstream damage and the object or source of damage.

         2. A broken disk, spacer or rotary air seal, usually causes heavy damage which results in a high level of engine vibration. In such incidents the complete engine must be disassembled to carefully examine the shafts and cases for signs of cracks and distortion.

      2. Broken primary static parts:

         1. Most broken static parts are usually related to the compressor stators. HP compressor stator failures usually result in heavy engine damage and, in most incidents, the temperatures of the hot area parts become too high. This makes it necessary for the damaged modules to be fully disassembled. Examine the disks for cracks, specially in the blade slot and blade edge areas. Also, examine all blades for cracks and damage.

         2. If metal spatter or other signs of high temperatures are found on down stream module parts, the down stream modules must also be fully disassembled for inspection. Examine all main shaft bearings.

   4. Main shaft bearing or gearbox damage:

      1. An engine with a broken main shaft bearing must be disassembled to a level sufficient to examine the compartment area. This includes the journal surfaces, the compartment seals and the scavenge pump. The gearbox and angle gearbox must also be disassembled for inspection. This is because they are an important part of the oil system where broken pieces of bearing can collect. If the damaged compartment is drained through the gearbox drive or tower shaft system, disassemble and examine the drive system components.

      2. When an engine has a broken shaft or bearing (In the gearbox drive or the tower drive system) the gearbox drive system, the gearbox and angle gearbox must all be disassembled for inspection.

      3. When all the damage is contained in the gearbox, only the gearbox and its parts are disassembled for inspection. When there are signs of damage to the bearing, gear or spline, a step-by-step inspection (Through the gearbox drive and tower shaft system) must be made until all the damage is found.

   5. Engines that suddenly stop:

      1. If an engine suddenly stops it is usually caused by object entry damage. After all such incidents the engine must be fully disassembled, for a 100 percent engine part inspection. During the inspection procedures examine all cases and bearing supports for distortion. Examine all rotor shafts and hubs for twist and examine all splines for wear and distortion. Examine the main shaft bearings and, if necessary, replace them.

      2. When an engine suddenly stops the oil flow also stops, which can then cause heat soak damage to the bearings. Discard all bearings that show signs of such damage, as shown by a color change.

   6. Engines that have had operational fires (For example, burnthrough and bearing compartment fires):

      1. Engines that have had operational fires must be fully disassembled for all parts to be examined. Contact IAE for additional support.

      2. When an engine fire is chemically extinguished, refer to the SPM TASK 70-11-56-110-501.

4. SUBTASK 70-02-04-200-004 Engines that are Hit or have Fallen

   1. The damage or the conditions that result from a Hit or Fallen engine include: An engine that hits the ground or other hard object. An engine that drags along the ground or other object, is also a Hit engine. While an engine that has fallen on to the ground, or on one end only, is a Fallen engine.

   2. The inspection procedures for Hit and Fallen engines are almost the same and are progressive in scope. Continue to disassemble the engine if damage is found at each level of inspection.

   3. For engines installed on aircraft where damage to the pylon or nacelle has occurred, examine the engine mount flanges. Also examine the cases, the external components and pipes, the gearbox housing and the mounts. If the damage is such that unwanted material has got into the front of the engine, examine the engine for object entry. Then examine the bleed system filters and valves, for unwanted material. If no damage is found, no more inspection procedures are necessary. If damage is found on the external components and pipes, the damaged parts must be replaced. If damage is found on the engine mount flanges, or the gearbox cases in the gearbox mounts, the engine must be removed. Examine the front and rear N1 rotor main shaft bearings for damage and brinelling. Examine the engine with a boroscope and make sure that the rotors move freely, then listen for unusual mechanical sounds. If the N1 main shaft bearings are damaged, remove and examine all the main shaft bearings. Monitor the chip detectors and oil filter more frequently, during initial operation of the engine, when it is used again.

   4. If an engine has fallen, remove and examine the front and rear N1 rotor main shaft bearings for damage and brinelling. If the bearings are damaged, remove and examine all main shaft bearings. Make visual and boroscope inspections and make sure that the N1 and N2 rotors move freely, then listen for unusual mechanical sounds. Monitor the chip detectors and oil filter more frequently, during initial operation of the engine, when it is used again.

5. SUBTASK 70-02-04-200-005 Tail Pipe Fires

   1. Tail pipe fires which are quickly extinguished when the engine is motored do not usually cause too much damage to the exhaust area. Examine the exhaust area for signs of surface burns. All parts that have surface burns, which include the fan duct acoustic liners if installed, must be replaced.

   2. Engines that have had many tail pipe fires, or which have become too hot when started, will be more stressed. They must be removed and disassembled sufficiently to see if the hot area parts have become too hot or if the turbine disks have become burned. Examine carefully areas that show signs of corrosion, cracking, thermal shock, changes in color, blistering, metal splatter, distortion and important dimensional tolerances specially primary supporting structures Step.

6. SUBTASK 70-02-04-200-006 General Inspection Instructions for Accident Damaged Engines

   1. 
      CAUTION
      IT IS IMPORTANT THAT ALL THE BEARINGS (OTHER THAN SLEEVE OR PLAIN BEARINGS) AND MAIN SHAFT CARBON SEALS ARE REPLACED. THEIR APPARENT CONDITION IS NOT IMPORTANT.

      NOTE

      All inspection procedures must be made as specified in the FAA approved data for engine parts (That is the Engine Manual, Standard Practices Manual and Component Maintenance Manual).

      Disassemble, clean, then make a general and visual inspection:

      1. Fully disassemble and examine all engine parts because, in general, it is not possible to find out how much the engine was stressed. When applicable, some more engine part repairs will be necessary.

      2. NOTE

         A special inspection, for the effects of corrosion, must be applied to all engine parts that were soaked with salt water.

         It is necessary to fully clean all engine parts, because it is possible that dirty materials (Which can cause corrosion) have got into the engine. It is also very important to fully clean the engine parts, after a fire was extinguished with chemical agents. Refer to the applicable Engine Manual procedures, specified for each engine part.

      3. Engine parts that became wet (When the engine was fully soaked in water), must be carefully examined for the effects of corrosion and cracks caused by thermal shock. Hot engine parts that were soaked in water can also have distortion and crack damage.

      4. Make a careful visual inspection of each engine part, to get an initial decision of its condition. All engine parts that are damaged, more than the repair limits specified in the Engine Manual, must be discarded.

      5. Engines which have had unusual conditions of operation during an accident will have unusual internal damage. It is important to be very careful when these parts are to be examined. Signs of higher than usual temperatures must be fully examined. Internal fires could have occurred with no signs of fire damage on external surfaces.

      6. If the blades, disks, cases or other engine parts (But not the compressor stator assemblies specified in paragraph D.) are a different color, or there are signs that the engine parts were used at higher than usual temperatures, the parts must be discarded. There are no nondestructive test procedures that can give a positive result as to the condition of the materials. Also, repair procedures that use heat are not usually used; because the higher than usual temperatures which are used, can result in distortion of the parts.

   2. Dimensional inspections:

      1. Together with the usual part inspection, it is necessary to make sure that all cases and bearing supports are in the permitted dimensional tolerances. Excessive loads can cause distortion of the case areas at the engine attachment points, support structures and attachment flanges.

      2. NOTE

         It is thought that a detail inspection of all engine parts will be done. But, if you are not sure if an engine part is serviceable, the data which follows is supplied. It will help you make a decision, to see if an engine part is satisfactory.

         Inspection for roundness, squareness and concentricity, of diameters will show if distortion has occurred. If the necessary dimensions are not given in the applicable Engine Manual, see the local International Aero Engines AG field service representative.

   3. Special detail areas:

   4. Disks, hubs and blades:

      1. In general, an unusual change of color, blistering, metal spatter or melting is a problem which shows higher than usual temperatures. An overtemperature or overspeed condition can cause the part to become larger and can be found by dimensional inspection. Disks must also be examined for dishing, which can result from an overtemperature condition.

      2. NOTE

         International Aero Engines AG will not usually permit the use of disks and hubs which are metal sprayed by upstream failure, because of the material property differences in the heat damaged areas.

         A careful visual inspection of the disk, hub and blade surfaces is necessary to find if hot metal particle impingement has occurred. The metal particles are caused by upstream failures and usually bond to the surfaces. A circular area of temperature color change is usually around the particles. This shows that this condition can lower the fatigue strength in this local area.

      3. Engine parts, other than disks and hubs, with not too many impingement areas can be repaired, if the heat damage areas can be polished out. All polished areas must be followed by a visual inspection, to make sure that they are in line with the metallurgical accepted data.

      4. Nickel-cadmium plated compressor disks and hubs will show the removal of the plated surface if the temperature is more that 1050 deg F (566 deg C). All disks and hubs in this group must be discarded. Disks and hubs that do not show a high temperature condition could have gone through their elastic limit. This can result in stress marks on the high stressed areas. A careful visual inspection, with 3x to 10x magnification for unusual surface marks, must be made on all disks and hubs.

      5. A disk or hub must be discarded, if there are signs of material deterioration or possible part damage.

      6. It is recommended that all disks and hubs, with less than 30 percent of their cycle or hour life remaining, will be replaced because their condition is not important.

      7. Air-cooled engine parts must always be examined to see if a blockage of the cooling air passages has occurred. When necessary, do flow checks as specified in the related Engine Manual instructions.

      8. Make a metallurgical overtemperature analysis on sample turbine blades if you think that they were used at unusual temperatures. Discard all the blades, in that stage, if signs of high temperatures are found. Then continue with an overtemperature inspection of a selection of blades from the stages that follow. Use the data specified in the related Engine Manual instructions.

   5. Vanes and stator assemblies:

      1. Make a detail part inspection of the turbine vanes and the compressor stator assemblies for cracks and dimensional tolerances.

      2. Compressor stator assemblies that show signs of high temperature use can usually be repaired. Only approved repair procedures, with correct installation equipment and heat treat cycles to put back the material properties, are to be used.

   6. Case and Supports:

      1. After the usual dimensional checks, all cases and supports must be examined for color changes and distortion caused by high temperatures. All cases and supports that show signs of high temperature use, must be discarded.

7. SUBTASK 70-02-04-200-007 Engine Contamination - Fire Extinguishing Agents

   1. NOTE

      This general data is given to help operators make a decision on the applicable procedure for engines which have had fire extinguishing agents put into them. This data is applicable where fires are confined to burner and gas path areas. The higher temperatures must not be more than the overtemperature limits.

      The applicable Engine Manuals give the full gas path cleaning procedures for engines contaminated by fire extinguishing agents. They also give the instructions for disassembly, cleaning and inspection procedures.

      Many tests were done to find the effects of fire extinguishing agents (sodium bicarbonate, potassium bicarbonate and bromotrifluoreomethane) on turbine engine parts.

   2. The problem with dry powder chemicals in an engine, is corrosion; during the operation of the engine. These chemicals can cause damage to the hot areas of the engine. Bicarbonate compound changes to carbonates (A very corrosive liquid flux), when the engine is in operation.

   3. Test results show that chemical corrosion will occur on stainless steels, nickel base alloys (coated or uncoated) and cobalt base alloys. The corrosion can occur at temperatures below the engine temperature of approximately 1200 deg F (649 deg C). Bicarbonate compounds do not cause corrosion on titanium, aluminium, magnesium, cadmium plated and nickel-cadmium plated low alloy steels; when the engine is in operation at the usual temperatures.

   4. Bromotrifluoreomethane is used as an inflight fire extinguishing agent. The company which makes the compound will supply the necessary precautions about the acids in the mixture which can cause corrosion on metals that get hot.

   5. There is no test done on the effects extinguishing agents have on the oil system. The oil system must be looked at because the agents could get into the system through the labyrinth seals.

   6. The procedures to clean the parts are given in the applicable Engine Manuals for the engines which have had fire extinguishing agents put into them. The manual must be read, and obeyed, to keep to a minimum the damage which could occur.

8. SUBTASK 70-02-04-200-008 Repair of Disks, Hubs, or Other Parts that Turn

   1. After the blend, weld, or other repairs to the parts that turn: Examine the parts, to make sure that there are no cracks or damage.