Rotor Maintenance Practices and Procedures PDF 2020

2 HELICOPTER AMT OPERATION FINAL AND 2104 MAINTENANCE LEARNING MODULE NUMBER ROTOR MAINT...

2 HELICOPTER AMT OPERATION FINAL AND 2104 MAINTENANCE LEARNING MODULE NUMBER ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS Institute of Engineering and Technology REVISION 2020 PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT 2 HELICOPTER AMT OPERATION AND FINAL 2104 MAINTENANCE LEARNING MODULE NUMBER ROTOR MAINTENANCE PRACTICES AND PROCEDURES CARL MICHAEL R. AGUILAR, MEAM NO PART OF THIS MODULE CAN BE USED AS A MAINTENANCE GUIDELINE FOR ANY ROTORCRAFT. ALWAYS REFER TO APPLICABLE UPDATED TECHNICAL MANUALS FOR INSTRUCTIONAL PURPOSES ONLY FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 1 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT This module discusses the general provisions for rotor maintenance practices and procedures. The laboratory module with the same title will discuss instead the assembly and disassembly procedures for Main Rotor and Tail Rotor as based on appropriate technical manuals. LEARNING OUTCOMES COURSE LEARNING OUTCOMES [CLO] MODULE LEARNING OUTCOMES [MLO] CLO 3 Distinguish parts, components and controls of helicopter. TOPIC LEARNING MLO 1. Identify different practices OUTCOMES [TLO] CLO 4 Discuss the functions of and techniques on Helicopter main different parts, components and controls and tail rotor. of helicopter. TLO 11. Discuss and identify MLO 2. Discuss on how to perform rotor installation, removal, cleaning, proper helicopter maintenance CLO 5 Apply the basic practices based on Manuals. and inspection. maintenance practices based on prescribed MLO 3. Identify the blade alignment manuals. techniques, Blade Tracking, Preservation and Storage. CLO 6 Discuss Helicopter operation limitations. MLO 4. Identify Helicopter Maintenance Checks. CLO 7 Identify the process on preparing certifications needed by a helicopter MLO 5. Identify certifications needed operator to conduct flying by helicopter operator to conduct operations flying operation FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 2 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT TABLE OF CONTENTS Description Page INTRODUCTION 5 ROTOR REMOVAL, CLEANING, AND INSPECTION 8 Rotor Blade Repair 8 Assessment Question 8 Rotor Blade Painting 9 Pain Spray Gun Techniques 11 Main Rotor Painting 13 Tail Rotor Painting 14 Assessment Question 18 Rotor Blade Alignment 19 Rotor Blade Tracking 20 Assessment Exercise 26 LIST OF FIGURES 4 REFERENCES 27 FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 3 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES  PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT LIST OF FIGURES Figure No. Description Page No. 1 Rights and Methods of Spraying 12 2 Fifty Percent Overlap 12 3 Optimum High Visibility Paint Scheme, Two Blade, Exposed Hub 15 4 Optimum High Visibility Paint Scheme, Two Blades With Spinner 16 5 Optimum High Visibility Paint Scheme, Four Blades, Exposed Hub 17 6 Rotor Blade Tracking 22 7 Electronic Blade Tracking Equipment 23 8 Reflector Blade Tracking 24 9 Tail Rotor Tracking 25 FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 4 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT INTRODUCTION The rotor maintenance practices and procedures discussed in this module represents of those in widespread use. No attempt has been made to include detailed maintenance procedures or guidelines for a specific helicopter rotor. As always, refer to the applicable maintenance manual for specific maintenance procedures. The practices and procedures described in this module pertain to the repair functions of aviation activities and are applicable to all levels of maintenance; because of the many types of Army aircraft, each shop within the manufacturing and repair section must, of necessity, have personnel trained in general practices and procedures to the extent that different type and model aircraft do not upset a smooth running shop: a. Responsibility. All supervisory personnel in the manufacturing section are responsible for a continuing and effective shop safety program. To implement and maintain this program, shop supervisors shall utilize bulletin boards, signs, and any other effective method. Shop personnel shall cooperate in the shop safety program by making helpful recommendations, and continually exercising care and caution in the operation of all shop equipment. All shop personnel shall strive to improve the safety program and be especially alert to observe and correct hazardous conditions and unsafe shop practices. All accidents, no matter how minor, shall be reported to the shop supervisor, and all published instructions regarding safety shall be strictly adhered to. b. Shop Housekeeping. Housekeeping is the yardstick by which the shops in the manufacturing section are judged. A clean, well arranged shop is a safe shop and reflects credit on all personnel concerned with its operation. The following shop practices shall be observed: 1. Oil pans or drip pans shall be used where leaking oil, grease, and similar materials may cause hazardous accumulations on equipment or floors. All spills shall be cleaned up immediately. Approved sweeping compound may be used to remove these materials from the floor. 2. Floors shall be maintained smooth and clean, free of all obstructions and slippery substances. Holes and irregularities in floors shall be repaired to maintain a level surface free from tripping hazards. 3. All unnecessary materials on walls shall be removed and projections shall be kept to a minimum. 4. Aisles shall be clearly defined and kept free of hazardous obstructions. Where possible, aisles shall be suitably marked by painting. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 5 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT 5. All machines, work benches, aisles, etc., shall be adequately illuminated. c. Shop Safety. Unsafe equipment and fire hazards are the main factors to be observed while planning safety procedures. 1. Equipment safety. Unsafe equipment shall be reported immediately. The following equipment safety practices shall be observed: (a) Machines shall be located to provide operators with sufficient space to handle materials and perform job operations without interference. (b) Bolt down all machinery that can move or walk due to vibration (drill press, bench grinder, etc.). (c) Substantial low resistance conductors shall be used to ground all stationary and portable machines, equipment, or other devices in which static charges may be generated, or which require electrical circuits of a hazardous nature. (d) Shop machinery shall be operated only by qualified personnel observing safe practices. (e) Safety devices, such as guards, interlocks, automatic releases, and stops, shall always be kept in operating condition. (f) Ensure that all unauthorized personnel are clear of area before opening valves or energizing electrical circuits for starting machinery. (g) Suitable mechanical guards, such as enclosures or barricades, shall be permanently installed on all machinery not already equipped with such to eliminate danger of injury from moving parts. (h) Machinery shall not be adjusted, repaired, oiled, or cleaned while machine is in operation or power is on. (i) Personnel operating machinery shall wear protective clothing as prescribed. A protective face shield or goggles shall be worn when operating a grinder regardless of whether grinder is equipped with attached shields. (j) Jewelry shall not be worn while performing any maintenance. 2. Fire safety. A constant vigilance shall be maintained to seek out fire hazards. Fire hazards are constantly present in the shop where sparks, friction, or careless handling can cause an explosion that may destroy equipment or buildings, and injure or kill personnel: FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 6 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT (a) NO SMOKING signs shall be placed in areas where smoking could create a fire hazard. (b) Personnel shall be trained in the use, knowledge, and location of shop fire fighting equipment. (c) Each shop shall be equipped with fire extinguishers suited for type of fire most likely to occur. (d) Use correct fire extinguisher for class of fire as follows:  Class A fire (wood, paper, trash, etc) Use water or soda-acid fire extinquisher.  Class B fire (oil, paint, fuel, grease, etc. ). Use bromotrifluoromethane or carbon dioxide fire extinguisher.  Class C fire (electrical equipment). Use bromotrifluoromethane or carbon dioxide fire extinguisher.  Class D fire (combustible metals-magnesium, titanium, zirconium, sodium, lithium, and potassium). Use dry powder type fire extinguisher. (e) Oily waste, rags, and similar combustible materials shall be discarded in self- closing metal containers which shall be emptied daily. (f) Flammable materials shall not be stored in the shop. (g) Use only approved cleaning solvents. d. Shop Tools and Materials. Handling tools and materials require observance of the following common safety practices: 1. Do not leave tools or objects in elevated positions from which they can fall or be knocked off. 2. Do not point a compressed airstream toward any part of the body. 3. All unserviceable tools shall be plainly marked and removed from service. 4. Electrical cables and air hoses to portable units shall be laid out so there is no danger of tripping. 5. Electrical tools shall be connected to a low resistance ground. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 7 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT 6. Keep bench tops covered with material hard enough to prevent chips and other foreign material from becoming imbedded. Keep bench tops clean and free from chips and filings. 7. Keep vise jaws covered with soft metal jaw caps. ASSESSMENT QUESTION 1. What would be the outcome if an inappropriate fire extinguisher was used? FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 8 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT ROTOR REMOVAL, CLEANING, AND INSPECTION For actual rotor removal, cleaning, and inspection procedures are explained in the applicable Maintenance Manuals (see Final Laboratory Module 2L). Rotor Blade Repair General procedures for metal and fiberglass rotor blade repair are described in the following paragraphs. Refer to the applicable maintenance manual for specific procedures: a. Metal Blade Repair. General procedures for metal blade repair are described in the following Paragraphs. 1. Negligible damage can be defined as a nick a scratch, a dent, or a gouge, depending on the type of helicopter and the construction of the rotor blade. The location of the damage on the blade, i.e. top, trailing edge, root area, by the tip, also has a bearing on being called negligible damage. Consult the applicable maintenance manual for specific definitions and corrective actions, if any. 2. Typical patching procedures for damaged rotors are explained in the following steps. Refer to applicable maintenance manual for specific procedures. (a) Remove paint from area to be patched. Protect core if exposed, so as not to contaminate while cleaning. (b) Draw a circle around damaged area large enough to encompass damage. (c) Cut out skin around damaged area. This may be accomplished by using a hole saw or scribing through skin with a sharp instrument (d) Remove skin in cut-out area, disturbing core as little as possible. (e) Deburr edges of hole, ensuring skin is free of scratches and nicks. (f) Prepare a patch of the same type of metal. Patch shall be large enough to overlap hole at least 0.75 inch all around perimeter. Deburr edges of patch. (g) Sand mating surfaces of blade and patch, using No. 400 grit paper. All paint and primer shall be removed from bond surface of blade. Wipe both FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 9 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT surfaces clean with a rag soaked in methylethylketone, Federal Specification TT-M-261. Dry with clean cloth. (h) Apply adhesive to bond areas of patch and blade. (i) Apply patch to blade, moving patch slightly back and forth under pressure, to seat properly and expel air pockets in adhesive. Blend out excess adhesive around edges. (j) Patch may be held in place while curing with rubber bands made from inner tube or other mechanical means. (k) Refinish patch and adjacent area. 3. Holes in blade pocket skin shall be repaired, as applicable, with aluminum tape, a bonded aluminum patch, or with urethane foam and aluminum tape. Refer to the applicable maintenance manual for specific repair procedures. 4. Inspect the tip cap for nicks, cracks, and corrosion. Check the balance weights for security of attachment. Refer to the applicable maintenance manual for specific repair procedures. 5. Remove corrosion from skin using abrasive cloth. Refer to the applicable maintenance manual for specific removal procedures. 6. Any voids not in excess of the allowable limits as shown by the applicable maintenance manual are to be sealed with adhesive. Blades with voids which exceed allowable limits shall be forwarded to depot for evaluation and repair. b. For fiberglass repairs, refer to the applicable maintenance manual. Rotor Blade Painting Main and tail rotor painting is explained in the following paragraphs. After complete repainting or extensive touch-up, rotor blades shall be rebalanced in an intermediate or overhaul maintenance facility. NOTE CAUTION Complete repainting of main and tail rotor blades on UH- 60, UH-1, OH-58, AH-1, AH- 64, OH-6, and CH-47 Painting of main rotor and tail rotor blades may create out- aircraft is normally accomplished during blade overhaul of-balance and unacceptable vibration conditions. Strict only. Main and tail rotor blades are individually balanced adherence to instructions is required to reduce the (spanwise and chordwise) to master blades during probability of creating these out-of-balance conditions. Care overhaul after painting to insure interchangeability must be exercised to apply proportionate amounts of paint between blades of the same configuration. Painting of to each blade to maintain proper balance. blades in the field may cause subsequent interchangeability problems. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 10 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT PAINT SPRAY GUN TECHNIQUES When manual spray applications are employed, techniques must be used which ensure the most uniform and proper dry thin coating. Spray guns (and spray coatings) are designed to be used with certain spraying techniques. Quality of finish will depend on how well these techniques are used. Spraying techniques include the following: a. Distance. Depending on the desired width of the spray pattern. The gun is held six to ten inches from the work (see figure1). If all other adjustments are correct. Greater distance will result in dry spray or dusting and excessive overspray. Holding the gun too close to the work will result in coatings which are too heavy and have a tendency to sag or run. b. Stroking. The essence of proper stroking is maintaining the same distance of the gun from the work, the same speed, and as near to a right angle to the surface as possible throughout the entire pass. The natural tendency for spray painters, particularly when fatigued or in an uncomfortable position, is to arc or wave the gun (see figure 1).This practice must be avoided at all costs, In general, wrist movement must be eliminated in stroking. A flexible wrist almost inevitably causes the gun to describe a curve instead of remaining parallel to the surface. This causes a thicker coating to be applied in the middle of the stroke than at the end. (An exception to the rules is in spotting during touch up. It is permissible to fan the gun to lay down a spot which is thinner at the edges in order to blend into the larger painted area.) Touch up here applies only to painting occuring in an approved facility and not open air touch up, Special pains must be taken, particularly when applying dense coating materials with poor flow characteristics (such as MIL-C- 46168), that the gun is held perpendicular to all surfaces (flat or contoured as they are passed).If this is not done, the irregular spray pattern formed will lay down uneven thicknesses. Uneven thickness will cause uneven drying when using single component paint. Uneven thickness, when MI L-C-46168 paints are used may cause sagging. Protrusions such as screw heads, etc., present surfaces that will require facing the gun in several directions to completely coat them. It may be advisable to spot paint these in advance. The rate of the stroke should be uniform and such as to lay down a full wet coat of material. Stroking should be in parallel passes with each stroke aimed for a 50 percent overlay, or so that the middle of the spray strikes the wet bottom edge of the previous stroke (see figure 2). FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 11 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 1. Rights and Methods of Spraying Figure 2. Fifty Percent Overlap FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 12 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT c. Triggering. Proper triggering of the gun is difficult to learn and can only be developed by practice. It is a matter of judgement and sensitivity of touch and variations of triggering technique may be called for in special situations. In general. The painter should begin his stroke before triggering the gun and release the trigger before stopping the stroke. It is intended to feather out the end of a stroke so that the end of a succeeding overlapping stroke will blend into it (see figure 1). Main Rotor Painting Tactical and non-tactical aircraft rotor blade painting are described in the following paragraphs: a. For tactical aircraft. The upper and lower surface of main rotor blades shall be finished in Aircraft Black, MIL-C-46168, No. 37038. b. For non-tactical aircraft: 1. The under surface of the blades shall be finished in aircraft black. 2. The upper surface of the blades will be painted with stripes per figure 3 to 5. Take note that the outer two stripes are the same on all blades. 3. For additional visibility in arctic areas, the outer 25% of the blades may be painted fluorescent red orange. The remaining portion of blades will be divided into 15% black and white segments as shown in the figures. 4. The CH-54 shall not have the striped paint scheme because the size of this aircraft make sit visible without the striped paint scheme. 5. The rotor and hubs and control mechanisms shall be painted aircraft black except for mating, load bearing or dynamic surfaces. c. Identifying dots of various colors will be installed by the contractor on mounted blades for the purpose of matching blade with identifying color on the hub. Blades ordered individually will not have identifying dots installed by the contractor, but will be added by field personnel as required. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 13 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Tail Rotor Painting Note: Complete repainting of rotor blades should be accomplished at an approved overhaul facility or depot activity. The weight and balance of blades is critical and complete repainting is not allowed by field units. Refer to applicable maintenance manual for extent of painting blades. a. For tactical aircraft. 1. Prime blade surfaces epoxy typeMIL-P-23377 or MIL-P-85582. 2. Both sides of the blades will be painted Aircraft Black, MIL-C-46168, No. 37038. 3. The rotor hubs and control mechanism shall be painted aircraft black, except for mating, Ioad bearing or dynamic surfaces. b. For non-tactical aircraft. 1. Prime blade surfaces with primer MIL-P-23377 or MIL-P-85582. 2. Both sides of the blades may be painted with stripes per figure 3 and 5. Note that the outer two stripes are the same on all blades in figure 5. 3. Application of stripes to tail rotor blades involves a 20% offset of non- concentric sections so as to provide concentric rings during rotation. Careful attention should be given to figures 3 and 5 when applying this paint scheme. 4. The rotor hubs and control mechanism shaft be painted aircraft black, except for mating, lOad bearing or dynamic surface. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 14 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 3. Optimum High Visibility Paint Scheme, Two Blade, Exposed Hub FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 15 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 4. Optimum High Visibility Paint Scheme, Two Blades With Spinner FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 16 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 5. Optimum High Visibility Paint Scheme, Four Blades, Exposed Hub FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 17 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Assessment Questions: 1. How aircraft painting does affect the Weight and Balance of a rotorcraft? 2. How to determine if your rotor blade is damaged? FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 18 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Rotor Blade Alignment Methods used to align rotor blades are described in the following paragraphs: a. Telescopic Method. The telescopic method of blade alignment is done with the rotor hub and blade assembly removed from the helicopter. The main rotor hub and blade assembly is placed on stands which will allow a blade to move horizontally if it needs to be adjusted. An alignment scope is positioned on the hub and is used to sight on the alignment screw on the blade tip. Alignment adjustments are made by adjusting the drag brace. Consult the applicable maintenance manual for detailed instructions. b. String Method. This method has been used for about 25 years and is considered good and accurate. A string is stretched between the alignment screws at the blade tips. The string should cross the rotor hub at the center of rotation. Consult the applicable maintenance manual for detailed guidance. Troubleshooting Procedures (Rotor Systems). Reference applicable maintenance manual (see Final Laboratory Module No. 2L). Helicopter Vibrations The following paragraphs describe the various types of vibrations. Table 1 shows the general frequencies into which frequencies are divided. a. Extreme Low Frequency Vibration. Extreme low frequency vibration is pretty well limited to pylon rock. Pylon rocking two to three cycles per second is inherent with the rotor, mast, and transmission system. To keep the vibration from reaching noticeable levels transmission mount dampening is incorporated to absorb the rocking. b. Low Frequency Vibration. Low frequency vibrations, 1/rev and 2/rev, are caused by the rotor itself. 1 /rev vibrations are of two basic types, vertical or lateral. A 1/rev is caused simply by one blade developing more lift at a given point than the other blade develops at the same point. c. Medium Frequency Vibration. Medium frequency vibrations at frequencies of 4/rev and 6/rev are another inherent vibration associated with most rotors. An increase in the level of these vibrations is caused by a change in the capability of the fuselage to absorb vibration, or a loose airframe component, such as the skids, vibrating at that frequency. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 19 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT d. High Frequency Vibration. High frequency vibrations can be caused by anything in the ship that rotates or vibrates at extremely high speeds. The most common and obvious causes; loose elevator linkage at swashplate horn, loose elevator, or tail rotor balance and track. Frequency level Vibration Extreme low frequency Less than 1/rev PYLON ROCK Low frequency 1/rev or 2/rev type vibration Medium frequency Generally 4, 5, or 6/rev High frequency Tail rotor speed or faster Table 1. Helicopter Vibration Types Rotor Blade Tracking Blade tracking is the process of determining the positions of the tips of the rotor blade relative to each other while the rotor head is turning, and of determining the corrections necessary to hold these positions within certain tolerances. The blades should all track one another as closely as possible. The purpose of blade tracking is to bring the tips of all blades into the same tip path throughout their entire cycle of rotation. Various methods of blade tracking are explained in the following paragraphs. a. Flag and Pole. The flag and pole method, as shown in figure 6, shows the relative positions of the rotor blades. The blade tips are marked with chalk or grease pencil. Each blade tip should be marked with a different color so that it will be easy to determine the relationship of the other tips of the rotor blades to each other. This method can be used on all types of helicopters that do not have jet propulsion at the blade tips. Refer to the applicable maintenance manual for specific procedures. b. Electronic Blade Tracker. The most common electronic blade tracker consists of a Balancer/Phazor, Strobex Tracker, and VIBREX Tester (see figure 7). The Strobex blade tracker permits blade tracking from inside or outside the helicopter while on the ground or inside the helicopter in flight. The system uses a highly concentrated light beam flashing in sequence with the rotation of the main rotor blades so that a fixed target at the blade tips will appear to be stopped. Each blade is identified by an elongated retro-reflective number taped or attached to the underside of the blade in a uniform location. When viewed at an angle from inside the helicopter, the taped numbers will appear normal. Tracking can be accomplished with tracking tip cap reflectors and a strobe light. The tip caps are temporarily attached to the tip of each blade. The high- intensity strobe light flashes in-time with the rotating blades. The strobe light operates from the aircraft electrical power supply. By observing the reflected tip cap image, it is possible to view the track of the rotating blades. Tracking is FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 20 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT accomplished in a sequence of four separate steps: ground tracking, hover verification, forward flight tracking, and auto rotation rpm adjustment (see figure 8). c. Tail Rotor Tracking. The marking and electronic methods of tail rotor tracking are explained in the following paragraphs. 1. Marking Method. Procedures for tail rotor tracking using the marking method, as shown in figure 9, are as follows: NOTE: After replacement or installation of tail rotor hub, blades, or pitch change system, check tail rotor rigging and track tail rotor blades. Tail rotor tip clearance shall be set before tracking and checked again after tracking. The strobe-type tracking device may be used if available. Instructions for use are provided with the device. a. Attach a piece of soft rubber hose six inches long on the end of a 1/2 x 1/2 inch pine stick or other flexible device. Cover rubber hose with Prussian blue or similar type of coloring thinned with oil. b. Start engine in accordance with Applicable maintenance manual. Run engine with pedals in neutral position. Reset marking device on underside of tailboom assembly. Slowly move marking device into disk of tail rotor approximately one inch from tip. c. When near blade is marked, stop engine and allow rotor to stop. Repeat this procedure until tracking mark crosses over to the other blade, then extend pitch control link of unmarked blade one half turn. 2. Electronic method. The electronic VIBREX balancing and tracking kit is housed in a carrying case and consists of a Model 177M-6A Balancer, a Model 135M- 11 Strobex, track and balance charts, an accelerometer, cables, and attaching brackets. The VIBREX balancing kit is used to measure and indicate the level of vibration induced by the main rotor and tail rotor of a helicopter. The VIBREX analyzes the vibration induced by out-of-track or out-of-balance rotors, and then by plotting vibration amplitude and clock angle on a chart the amount and location of rotor track or weight change is determined. In addition, the VIBREX is used in troubleshooting by measuring the vibration levels and frequencies or revolutions per minute (RPM) of unknown disturbances. The main units of the VIBREX are the Balancer/Phazor 177M6A, Strobex Tracker 135M11, and VIBREX Tester II. The primary airframe mounted components are three Accelerometers 4177B and two Magnetic Pickups 3030AN. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 21 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 6. Rotor Blade Tracking FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 22 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 7. Electronic Blade Tracking Equipment FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 23 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 8. Reflector Blade Tracking FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 24 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Figure 9. Tail Rotor Tracking FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 25 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 26 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT Assessment Exercise Research about updated techniques on blade tracking of Main and Tail Rotor. FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 27 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT REFERENCES Department of Army (1992), Technical Manual, Aviation Unit Maintenance (Avum) and Aviation Intermediate Maintenance (Avim) Manual, (Propeller, Rotor, and Powertrain Maintenance Practices) Volume 5 Helicopter Pilot Flying Handbook, Federal Aviation Authority FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 28 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT RUBRICS FOR ESSAY/RESEARCH CONTENT (70%) KNOWLEDGE ON THE TOPIC C1 35 INFORMATION BASED ON TECHNICAL C2 25 MANUALS/JOURNALS/BOOKS QUALITY OF INFORMATION C3 10 70 FORMAT (30%) F1 5 FORMAT BASED ON THE GIVEN INSTRUCTIONS GRAMMAR, USAGE, SPELLING F2 5 WORD COUNT& QUALITY OF F3 20 WRITING 30 100 FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 29 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES PHILIPPINE STATE COLLEGE OF AERONAUTICS INSTITUTE OF ENGINEERING AND TECHNOLOGY AIRCRAFT MAINTENANCE TECHNOLOGY DEPARTMENT THIS PAGE IS INTENTIONALLY LEFT BLANK FOR VILLAMOR CAMPUS FINAL LEARNING MODULE NO. 2 30 COPY ONLY ROTOR MAINTENANCE PRACTICES AND PROCEDURES