Aviation Mechanics Bulletin January-February 1991

Photograph not available.

How to Work Safely With Composite Materials by Robert A. Feeler, Maintenance Consultant

The use of composite materials for In working with sheet metal, about aircraft fairings and secondary struc- all you needed to worry about was tures has been fairly common for cutting your finger on a sharp edge many years. These composites were and keeping drill chips out of your mostly what is commonly referred eyes. As you shift into working with to as fiberglass. composites, your exposure to potentially harmful materials will be mul- More recent advancements in tech- tiplied. nology have brought about newer technology composite materials that A composite is an engineering term are lighter, stronger and much easier for a material consisting of various to fabricate than metallic structures, combinations of alloys, fibers, res- and they are finding more widespread ins, fillers, plastics, solvents, and ad- use as metal replacements than fi- hesives, combined to produce the de- berglass. As more of these exotic sired strength and characteristics materials come into use, however, needed for the application. It is the the technician will be increasingly harmful side effects of these various called upon to repair and maintain components that present additional these materials. hazards and risks for the technician

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 1 working with composite materials. Working Safely with The technician who comes in con- New Materials tact with composites has to be con- cerned with: While these hazards may seem too much to handle at first, just remember a few basic rules and stick with ¥ inhaling vapors or fumes from them. volatile solvents, adhesives and coatings; ¥ Know what you are working with. ¥ inhaling fumes created by sanding or cutting of ¥ Use the proper tools and equip- materials; ment.

¥ inhaling dust and fibers cre- ¥ Use the appropriate protective ated by sanding or cutting of equipment. materials; ¥ Have appropriate first aid and ¥ eye damage from antidote/treatment materials on - fumes and vapors hand with personnel available - fibers and chips; who are trained in their use and application. ¥ absorption of harmful chemicals into the body through the skin; Dealing with the Risks

¥ absorption of harmful chemi- Inhalation — We have all been ac- cals or fibers into the blood customed to using a paint mask or a stream through cuts or scratches dust mask for various operations in on the hands; the past, and many of you will have a mask in your toolbox. But, just a ¥ direct ingestion of chemicals mask is not enough. Be safe and or fibers through inadvertent refrain from using an old mask or swallowing or eating food con- one that was not specifically designed taminated with such materials; for the hazards associated with com- and posite materials. Find out which composite you will be working with ¥ burns from heating pads or and secure the proper protective mask chemical reactions. for working with that material.

2 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 Proper Fitting of Respiratory Protection

The main point in wearing a face mask is to ensure that all air ingested into the lungs is filtered; consequently, the initial fitting must ensure that no air bypasses the filter.

The process of fitting a face mask involves three basic steps: cupping the mask under the chin with the nose piece up, pulling the headband up to the back of the head and pressing the soft metal nosepiece to conform snugly with the contours of the nose.

The 3M Occupational Health and Environmental Safety Division includes more detail on fitting the dust and mist respirators it produces, reproduced here with the permission of 3M:

Photograph not available.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 3 Assure that the mask conforms to face masks are strongly recom- your face; most good masks will have mended. Contact lenses should never wire embedded in the sealing lips to be worn while working with solvents bend and conform to your facial con- because fumes could actually “melt” tours. This may necessitate shaving the contact lens to the eye. off a beard or mustache in order to get a proper seal and assure that you Dust, fibers and particles that can get the intended protection of the become irritants or carcinogens if mask. An industrial mask approved inhaled into the breathing passages for “airborne fiber” protection must and lungs are also of concern to com- be used whenever sawing, grinding posite workers. If at all possible, or sanding composite materials. Re- work on a “downdraft table” which place the mask or any filter cartridges draws most of the potentially harm- frequently, and clean the straps and ful by-products away from the worker sealing lips daily to ensure a good as they are created. At the very least, fit. have another suitably protected indi- vidual hold a portable vacuum unit Become familiar with the properties close to the cutting area to collect of all chemicals, solvents and adhe- the majority of the fibers. sives which you will be using. Re- view container labels and the Mate- Eye Protection — Aramid fibers can rial Safety Data Sheet (MSDS) that scratch the eyeball. Dust and fibers accompanies the shipment of haz- can cause infections. Chips and ardous chemicals to determine ac- scraps can damage sensitive tissues. ceptable exposure and assure that Fumes and vapors can irritate tissue proper masks or breathing hoods are and even melt contact lenses. The provided. A face shield is an excel- message is clear — protect your eyes. lent form of protection only if there is adequate ventilation to preclude If ventilation is adequate, a good face the hazard of fumes being trapped shield is an excellent form of eye under it. A safety hood with clean protection. For protection from dust air flowing in from an outside source and airborne fibers, safety goggles may be necessary in some instances. with close fitting side panels are of- In other cases, a special mask can be ten used. provided to filter out harmful components or fumes. If in doubt, use the best protective device you can obtain. Do not skimp Potential damage to sensitive eye tis- on eye protection. If harmful vapors sues from fumes and vapors must be or fumes are a factor, use a full hood considered, and safety goggles or with a fresh air source.

4 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 Last, but not least, keep your eye “scrubbed into” your skin. protection clean. Store your mask away from areas that are contami- Absorption — Many technicians do nated with chips and dust. Clean it not recognize the harm that can re- before you put it on, especially the sult when certain chemicals enter the edges where it contacts your face so blood stream. Although healthy skin that harmful fibers or dust are not is a natural barrier to many harmful

Understanding the Material Safety Data Sheet (MSDS)

There are an estimated 575,000 exist- emergency treatment of each product. ing chemical products used in various work places, and hundreds of new ones The data on each MSDS is usually self are introduced annually. Chemical ex- explanatory; however, if you are in doubt posure may cause or contribute to many about any aspect of the product, contact serious health effects such as heart ail- the manufacturer or your company medi- ments, kidney and lung damage, steril- cal office to clarify any concern you may ity, cancer, burns, and rashes. Because have. Be especially alert in studying the of the seriousness of these safety and “Health Hazard Data” section and re- health problems, the U.S. Occupational view your emergency and first aid equip- Safety and Health Administration ment to assure that you have the materi- (OSHA) has issued a rule called “Haz- als and understand their use. ard Communication,” the basic intent of which is to ensure that employers and In the “Hazardous Ingredients/Identity In- employees are informed about work haz- formation” section of the MSDS you will ards associated with each chemical and note two acronyms with which you may how to protect themselves. not be familiar:

The hazard communication standard es- OSHA PEL — This is the OSHA Permis- tablishes uniform requirements to en- sible Exposure Limit which may be ex- sure that the hazards of all chemicals pressed as a time-weighted average or imported into, produced, or used in U.S. as a ceiling exposure limit. work places are evaluated, and that this hazard information is transmitted to in- ACGIH TLV — This is the American Con- volved persons. Chemical manufactur- ference of Governmental Industrial Hy- ers and importers must convey the haz- gienists Threshold Limit Value which is ard information by means of labels on the ceiling exposure limit or the concen- containers and material safety data tration that should not be exceeded even sheets (MSDS). Manufacturers and dis- momentarily. tributors are required by law to provide the MSDS with the product. The ACGIH annually publishes a book which explains and lists the TLVs for It is important to understand the terms various chemicals. This publication is and limitations stated on the MSDS so available from ACGIH, 6500 Glenway that you may take the proper precau- Ave., Bldg. D7, Cincinnati, OH 45211 tions and be aware of the first aid and U.S. Telephone (513) 661-7881.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 5 substances, there are few technicians fungus infection or skin rashes. who are without any cuts or scratches on their hands. Even the most mun- Hands should be rinsed thoroughly dane solvents can be very dangerous before and after work, before eating if held in contact with the skin for or smoking, and before putting on prolonged periods, and others are so gloves. Avoid extensive use of soaps potentially toxic that even a tiny that remove natural skin oils. Spe- amount can do irreparable damage cial “waterless” cleaners formulated to internal organs if allowed to enter for use with epoxies and solvents, the blood stream. which contain skin emollients that soften the skin, are recommended. If, after researching the characteristics of the substances you will be Do not use solvents to clean your working with, you remain in doubt skin. Methyl ethyl ketone (MEK) about the proper protection to be should never be used to clean your used, contact your company medical hands, or objects with which your office or the manufacturer of the hands come in contact. product. Tools which become contaminated Many epoxy resin systems can dam- with epoxy resins, or clothing which age eyes, face and exposed skin. Face becomes saturated with resins, should shields should be worn whenever be either discarded or thoroughly mixing and using such compounds. cleaned before further use. Gloves should extend well beyond your cuffs, and long sleeved cloth- If skin becomes itchy or shows red- ing, coveralls, or protective sleeves ness or scaling, refrain from further should be used whenever handling exposure until it returns to normal. A epoxy compounds. Protection of good routine for treatment to protect arms can be accomplished with plas- or restore your hands is: tic sleeving; however, orthopedic stocking net is recommended to pre- ¥ Soak your hands in lukewarm vent perspiration and reduce irrita- water for 20 minutes. tion. ¥ While hands are still wet, mas- Cloth-lined rubber gloves are prefer- sage them with white petrola- able because they absorb perspira- tum jelly (Vaseline). tion. If they are to be re-used, gloves should be turned inside-out to allow ¥ Allow the ointment to remain drying. Discard gloves after heavy on your hands for 20 minutes, usage to preclude being exposed to then remove with a clean towel.

6 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 ¥ Treatment may be repeated once Burns — The exposure to burns is or twice daily. a hazard not often present in working with sheet metal materials. Ingestion — It is unlikely that you Heat is used however, in the curing will swallow solvents or chemicals of composite materials, and the used in composite repair. However, temperatures can be injurious to if you should somehow allow any of unprotected skin. Insulated mitts or these compounds to enter your di- pads should always be available gestive tract, immediate treatment is and used to handle heat curing com- imperative. Here again, know what ponents. you are working with. Review the MSDS and keep it convenient to the The chemical reaction of certain ep- work area so that you know the oxy components when mixed is an proper treatment if the material is additional concern for technicians. swallowed. The temperatures reached during the curing of some epoxy mixes can be The emergency treatment for swal- sufficient to cause serious burns. lowing various chemicals varies Avoid the temptation to “see if it is widely. Some call for you to induce done yet” by touching with an un- vomiting while others specifically protected finger. You might find your prohibit that procedure but, instead, finger tip glued to the piece and you call for drinking large quantities of can lose some skin in the process of water. Be aware of the recommended separating it. first aid treatment and get the affected person qualified medical at- Shop Conditions — General house- tention as quickly as possible. keeping is especially important in a composite repair area, and directly The risk of ingestion through eating, impacts the safety of technicians in- drinking or smoking while there is a volved. A few of these basic rules residue of toxic chemicals on the bear repeating: hands is a more common concern for technicians working with compos- ¥ Aisles and areas around equip- ites. Be sure that you remove your ment should be kept clear and gloves and rinse your hands thor- accessible. oughly prior to eating or drinking. Keep lunch containers away from ¥ Maintain unblocked access to sources of possible contamination safety equipment such as eye and do not eat or take your break in wash and fire extinguishers. work areas where chemicals, dust or Remember that eye wash sta- vapors are present. tions are not trash receptacles.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 7 ¥ Keep storage areas neat and tainers clean and supplied with orderly. fresh solvent.

¥ Keep materials measuring and ¥ Around sanding booths and dispensing areas clean and neat. downdraft tables, keep tables Wipe up spillage immediately, and surrounding areas clean and keep container lids closed and keep screens and filters clear labels intact, and keep trash of debris. receptacles emptied. ¥ Keep all work benches clean, ¥ In lamination areas, discard neat and orderly. mixing containers after use, keep fiberglass and bagging remnants ¥ Assure that first aid equipment swept up and keep solvent con- is maintained and ready to use.o

NEWS & TIPS

New AMB Editorial Coordinator Appointed

Photograph Photograph not available. not available.

Robert A. Feeler Robert B. Phillips

Robert A. Feeler has been appointed Feeler is an independent mainte- editorial coordinator of the Flight nance consultant working with FSF Safety Foundation (FSF) Aviation and other organizations. His avia- Mechanics Bulletin. He succeeds tion career spans 38 years and in- Robert B. Phillips, AMB editorial cludes experience as a mechanic to coordinator since 1980, who has a vice president. retired from active direction of the publication. Feeler served as vice president of

8 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 technical services for Aspen Airways tury. He began with the acquisition and director of maintenance and en- of both pilot and mechanic certifi- gineering for the Metro Express Di- cates in 1938. He worked initially vision of Allegheny Airlines. He was with William Lear, who was then director of quality control for Lake developing aviation radio and auto- Central and Allegheny Airlines, after pilot equipment, and Bernarr working his way up from mechanic MacFadden, an early aviation- to lead mechanic to inspector. minded publisher. During World War II, he taught at a U.S. Naval Air At Aspen Airways, Feeler reorga- Service School in Florida. nized the maintenance and quality control sections. He originated and Following the war, Phillips taught directed an in-house safety and ac- aeronautics in public schools until cident prevention program at Allegh- 1949, when he joined National Air- eny Airlines and directed safety in- lines and became director of train- spections of work procedures and ing. In 1960, Phillips was employed facilities. He also participated in by the U.S. Federal Aviation Ad- accident investigations as a member ministration (FAA) and served in the of the U.S. National Transportation Flight Standards Service at the Safety Board (NTSB) team as a rep- agency’s Washington, D.C., head- resentative of the operator. quarters. After retiring from the FAA in 1980, he began his association He also has participated in FSF avia- with Flight Safety Foundation as a tion safety audits with emphasis on writer and editorial coordinator for maintenance, quality control, facili- the Aviation Mechanics Bulletin. ties and support equipment. Under Phillips’ direction, the bulle- Feeler is the author of more than 30 tin was dedicated to recognizing the articles for various industry publi- role played by the air carrier and cations, including the Aviation Me- general aviation technician in avia- chanics Bulletin. As a consultant, tion safety, and its editorial content he has participated in more than 50 offered practical information and ad- aviation safety audits and related vice that emphasized safety in main- projects with corporate and air car- tenance practices. Phillips has con- rier operators throughout the world. tinued his involvement with the Avia- tion Mechanic Safety Awards Pro- As he leaves active involvement in gram which he helped develop when the Aviation Mechanics Bulletin, Bob he worked with the FAA. Phillips looks back upon an aviation career that has spanned a half cen- Far from retiring to a rocking chair,

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 9 Phillips plans to continue his travels In honor of the exposition, and to with his wife, Soula, in their Air- recognize all professionals in the stream travel trailer. His word aviation maintenance and ground processer will not be put to pasture, support equipment industry, the either; Phillips already has begun mayor of Orlando, Bill Frederick, work on some personal writing has declared the week of April 14- projects he has “finally found time 20 as “Aviation Maintenance Tech- for.” nology Week.”

Anyone interested in participating AMTECH 91 should contact Alan Wallace with Andry Montgomery & Associates Moves to Orlando Inc. 6100 Dutchmans Lane, Louis- ville, KY 40205 U.S. Telephone AMTECH 91, the aviation mainte- (502) 473-1992. nance technology exposition spon- sored by Aviation Equipment Mainte- nance magazine, is moving from its Corrosion Prevention previous convention location in Dal- Program Affects las, Texas, U.S., to Orlando, Florida this year. The event will be held April Nearly 3,000 Aircraft 16-18, 1991, at the Orange County Convention/Civic Center in Orlando. The U.S. Federal Aviation Adminis- tration (FAA) has issued directives In moving the show to Florida, the for monitoring and correcting cor- sponsors are hoping to give the event rosion on 2,989 Boeing aircraft, of a new appeal and make it more ac- which 1,512 are registered in the cessible to a larger percentage of the United States. The directives affect potential attendees by virtue of its Boeing 707, 727, 737 and 747 air- easy access to international air travel craft models. and lower air fares. The airlines operating the aircraft are Among numerous topics that will be required to develop corrosion preven- covered during the three-day confer- tion and control programs to prevent ence program are technical strategies, structural degradation due to corro- international training programs, new sion and a combination of corrosion and advanced methods and repair pro- and fatigue. The deadline for com- cedures, computer-based training and pliance is December 12, 1991. trend monitoring for PT6 and JT15 engines. In a related action, similar corrosion

10 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 control programs were proposed by has announced that it will proceed the FAA in a notice of proposed rule with the long-awaited Boeing 777 making (NPRM) that would affect aircraft with the receipt of an order McDonnell Douglas DC-8, DC-9 from United Airlines for 34 firm de- and DC-10 aircraft. livery positions and 34 options.

The long-range, twin-engine Minnesota Holds widebody jetliner is sized between Technicians the company’s 767-300 and 747-400, with seating proposed for 360 to 390 Conference passengers.

The Minnesota Department of Trans- Working closely with United and portation (MDOT), Office of Aero- other major carriers in the design nautics, in cooperation with the U.S. process, Boeing has worked to aim Federal Aviation Administration the aircraft at the broadest possible (FAA), will hold the 1991 Minne- market. Among the developments sota Aviation Maintenance Techni- emerging from discussions with the cians Conference March 11-12, carriers are: 1991, at the Thunderbird Hotel in Bloomington, Minnesota, U.S. ¥ A wing optimized for range and takeoff performance that The seminar is intended for licensed provides the ability to take off mechanics, students, repairmen, air- and climb quickly from high- craft refueling technicians and in- elevation, high-temperature air- terested pilots. The program will ports with full passenger loads. include educational and safety pre- sentations, industry exhibits and rec- ¥ Compatibility with existing gate ognition of the outstanding aviation and taxiway space. This was maintenance technician of the year. accomplished by developing up- ward-folding wing tips as an For more information, contact optional feature which reduces Donald Goserud, Office of Aeronau- the span and allows the 777 tics, at (612) 296-7285. to use gates and ramps sized for the shorter wings of DC- Go-ahead Given 10s, L-1011s and Boeing 767s. For Boeing 777 ¥ Fly-by-wire control systems with a Boeing-patented two-way Boeing Commercial Airplane Group digital data bus that will allow

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 11 flight computers, instruments proposed 777 family of air- and systems to communicate craft. with one another through a common wire path. The object, Boeing claims that new design and from a maintenance standpoint, testing initiatives will help assure is to simplify assembly, save higher levels of service readiness and weight and increase reliability reliability on the very first 777 com- through a reduction in wiring pared to what has been possible on and connectors. previous jetliner introductions. Ini- tial deliveries are targeted for May 1995. o

Photograph not available. MAINTENANCE ALERTS

¥ Portions of the primary struc- This information is intended to pro- ture will be made of new com- vide an awareness of problem areas posite materials in place of metal through which such occurrences may to save weight. These are for- be prevented in the future. Maintenance mulated for greater strength than alerts are based upon preliminary in- present composites and will be formation from government agencies, used in the horizontal and ver- aviation organizations, press information tical tails and in the floor beams and other sources. The information may of the passenger cabin. not be accurate.

¥ New flat panel cockpit display screens for flight, navigation and engine information. Exhaust Pipe Failures ¥ Initial maximum takeoff weight Result in Inflight Fires of 506,000 pounds (229,520 kg) and a range up to 4,800 Any reciprocating engine exhaust statute miles (7,700 km), with system is subject to fatigue cracks as the capability to stretch the fu- a result of the heat and vibration in- selage for future versions in a herent in these installations. Inspec-

12 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 tion of exhaust systems should al- 04) calling for frequent inspections ways be included in the preventive and eventual modification to install maintenance scheduled for any such improved parts. All of the aircraft aircraft. Certain aircraft however, are involved in the accidents during 1990 subject to abnormal cracking and had been modified in accordance must receive special attention to en- with the AD. It appears, from the sure continued airworthiness. continuing incidents of exhaust system failures, that this modification is Failure of exhaust components can not an effective fix. result in overheating and damage to adjacent structures and in some cases, Technicians involved in the mainte- in-flight fires. U.S. National Trans- nance and inspection of PA-32RT- portation Safety Board (NTSB) ac- 300T and PA-32R-301T aircraft cident records show that Piper mod- should be especially alert when in- els PA-32RT-300T and PA-32R-301T specting these exhaust systems. The have been involved in four accidents, NTSB has issued a safety recom- two of which involved fatalities, since mendation calling for the FAA to February 3, 1990, as a result of in- issue an AD applicable to Textron flight engine fires. Other service dif- Lycoming Model TIO-540-S1AD ficulty reports (SDRs) have been sub- engines requiring within the next 10 mitted to the FAA involving similar hours of flight, and at appropriate failures on this aircraft. recurring intervals thereafter, an inspection and alignment of the cross- Investigation of the recent accidents over exhaust assembly in accordance has disclosed that the engine fires with Part I of Service Bulletin Num- in each instance resulted from fa- ber 484. tigue cracking of the left intermediate exhaust pipe attachment flange. The manufacturer is requested to is- Cracking of the flange allows ex- sue a service bulletin incorporating a cessive movement of the pipe and new, improved design modification may result in separation at the aft to the engine exhaust system in or- slip joint connection to the cross- der to prevent inflight engine fires over tube. resulting from failure or separation of the left intermediate exhaust pipe. This same installation was the subject of an earlier NTSB investigation The NTSB recommendation also in 1988. Following this earlier in- calls for the FAA to issue an AD vestigation, the U.S. Federal Avia- mandating the installation of the im- tion Administration (FAA) issued an proved parts developed as a result of airworthiness directive (AD 89-12- the service bulletin.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 13 Loose Actuator Fitting quence condition as a result of loose bolts was substantiated during land- Jams Landing Gear ing gear retraction tests previously conducted by the U.S. National The Boeing 727 landed with the right Transportation Safety Board (NTSB) main landing gear partially extended on Boeing 727 airplanes in connec- after repeated attempts by the crew tion with a similar landing gear mal- to extend the gear with the normal function incident. system, manually and by inflight maneuvers. Although no passengers The Boeing Commercial Airplane or crew members were injured in the Group earlier had concluded that that emergency landing, the aircraft was a loose actuator fitting can prevent substantially damaged. retraction of the affected main landing gear, and issued Service Letter It was found that the right main land- Number 727-SL-32-47 in 1983. As ing gear had jammed against the in- a result of this latest incident, Boe- board landing gear door, apparently ing issued an notice to all operators because of an out-of-sequence con- of Boeing 727s, re-emphasizing the dition. need to inspect the fittings in accordance with the service letter. The landing gear door actuators on the Boeing 727 are attached through The installation of new, improved a serrated plate (for rigging adjust- landing gear safety bars provides ad- ments) to the inboard door. Proper ditional protection against interfer- operation of the doors is critical be- ence between the doors and the land- cause the doors must be actuated to ing gear in the event of an out-of- their full travel before hydraulic pres- sequence condition. However, only sure can be routed to the actuators about 20 percent of the Boeing 727 for the landing gear. fleet has had this modification installed. Investigation of this incident disclosed that the bolts securing the As a result of this situation, the NTSB landing gear door actuator fitting has recommended that the FAA is- were undertorqued. One bolt was sue an airworthiness directive (AD) tightened to only 10 foot-pounds and requiring immediate inspection of the the other two could be turned by landing gear door actuator fittings hand. The manufacturer’s manual for security and proper bolt torque, calls for these bolts to be torqued to and a subsequent modification of the 25 to 42 foot-pounds after door rig- fittings to ensure that they remain ging is completed. An out-of-se- correctly and securely fastened.

14 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 Technicians involved with the main- ¥ Drill 1/2-inch holes in the cabin tenance and servicing of Boeing 727 top skin on seven-inch centers aircraft should review Service Letter along the center line of the hat- 727-SL-32-47 and the appropriate shaped section. The first hole sections of the maintenance manual should be on the fuselage cen- to assure that they are familiar with terline. Do not drill holes in the affected installations. the area of the spar bearing blocks. After completion of the inspection, smooth the edges Corrosion a Concern of holes and apply a protective coating. Close the holes In Older Cessnas with grommets, fabric patches, or other suitable methods. The U.S. Federal Aviation Adminis- tration (FAA) has issued an alert, NOTE: If holes are drilled into the based upon malfunction and defect spar channel, reinforce the channel reports, that concern corrosion in the to provide equivalent strength. fuselage front and rear spar assem- blies of Cessna Models 120, 140, 150 and 170 series aircraft with more Elevator Hinge Pin than 10 years since date of manufac- Suspected as Cause of ture. Inflight Breakup Based upon reports of corrosion in the fuselage front and rear spar wing There were no survivors among the carry-through structure of these air- 50 passengers and three crew mem- craft, it is recommended that the hat- bers when the Convair 580 crashed shaped channel across the top of the off the coast of Denmark. The fuselage be checked at every annual aircraft had departed Oslo, Norway, inspection. The manufacturer rec- for Hamburg, Germany, and while ommends one of the following pro- cruising at 22,000 feet, the aircraft cedures: disappeared from air traffic control radar over the North Sea. Most of ¥ Remove either wing and re- the wreckage was recovered and move the spar bearing block. transported to a facility near Oslo Inspect the interior of the hat for examination. section for corrosion or other discrepancies. The accident is being investigated under the authority of the Aircraft OR Accident Investigation Board of

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 15 Norway and the U.S. National The NTSB however, is convinced that Transportation Safety Board the Convair service bulletins are of (NTSB). Preliminary indications are major significance and that compli- that the airplane experienced an ance should be mandatory. The inflight breakup while in cruise agency has therefore recommended flight. During reconstruction of the that the FAA issue an airworthiness wreckage, the accident investigators directive (AD) mandating compli- noted that one of the four right-hand ance with Convair Alert Service Bul- elevator hinge pins was missing. letin Number 640 (340D) No. 55-A5 Damage surrounding the location of for all CV-340/440/580/640 aircraft the missing pin indicated that the and 600 (240D) No. 55-A4 for all pin was missing prior to the flight CV-240/600 aircraft. or was lost in flight.

The manufacturer, Convair Division Take Care with Those of General Dynamics, is currently examining the effect of a missing Cabin Windows pin or pins on aircraft stability and control. Field service reports re- A Boeing 727 cabin outer window ceived by Convair indicate that other pane recently experienced a crack operators performing inspections through a routed radius (mounting during routine maintenance have flange). The crack appeared to have found evidence of bearing rotation, started with a mark, or scoring, most binding and wear on the elevator likely made while trimming the seal hinge pins. If these conditions con- upon installation. The manufacturer tinue undetected, the loss of an el- cautions technicians to make sure the evator hinge pin may occur that could routed radius is free of stress-raising possibly cause an inflight separation marks, and to use care when trim- of the elevator and loss of control of ming the seal to avoid surface dam- the airplane. age.

The manufacturer has issued an alert A major U.S. airline reports that service bulletin requiring a one-time cabin window damage has cost the inspection of the elevator hinge pins, airline $73,050 in just six months; a bushings, nuts, bearing plates and single DC-10 window can cost as bearings, plus the replacement of any much as $630. worn or damaged parts. These inspections are recommended to be Damage occurs in several ways, but performed within the next 50 hours a significant portion of it has been of aircraft operation. found to be due to mishandling dur-

16 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 ing shipping. Careful attention to by a report of extensive fatigue crack- packaging and use of the proper ship- ing and resultant distortion of the ping container can greatly reduce this nose wheel well vertical beams on a problem. Most of the damage, how- Boeing 747, which if not corrected, ever, occurs when the windows are could result in rapid decompression outside the container while handling of the aircraft. during removal or installation. The second AD, applicable to Boe- Prying with screwdrivers or other in- ing 767-200/300 models, requires the struments is a definite no-no. Win- installation of a mechanical power dows that have been removed usu- transfer unit between the left and ally can be salvaged, and should be right hydraulic power systems of each treated with the same care as a new airplane. one. This action was prompted by analy- sis that indicates airplane pitch con- Airworthiness trol capability is marginal with ad- Directives Issued for verse center-of-gravity and gross weight combinations when both left Boeing 747s and 767s and right hydraulic systems become inoperative. The U.S. Federal Aviation Adminis- tration (FAA) has issued three air- The third AD applies to all models worthiness directives (ADs) that re- of the 767. It requires modification quire inspection, modification and of the vertical stabilizer forward clo- replacement of parts in areas critical sure rib by the installation of a cover to maintaining structural integrity in plate and a panel assembly over light- certain Boeing 747 and 767 aircraft. ening and access holes to provide an air flow path to the vertical stabi- The first AD, affecting all 747s, is a lizer. follow-up to a telegraphic AD that requires inspection and repair, if nec- This action is necessary to prevent essary, of the nose wheel well top over-pressurization of the vertical sta- panel sections, vertical beam webs bilizer, which could cause structural and clips, and the adjacent sidewall failure in the event of a rupture of panel web. This AD was prompted the fuselage under the dorsal fin.o

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 17 offer manpower savings as well, since NEW PRODUCTS one man can attach the towbar to the aircraft quickly. In operation, the Reference Book towbar operator pulls up to the aircraft to within six inches of the tow For Composites point, removes the tow bar from the tug and attaches it to the aircraft. The ASTM (American Society for The tow coupler is then released and Testing and Materials) has published telescoped out to attach the tow bar ASTM Standards and Literature Ref- to the tug. erences for Composite Materials, 2nd Edition. The newly revised publication includes standard test methods for high modulus fibers and for com- Photograph posite materials reinforced by high not available. modulus fibers, as well as applicable standards used to support standard tests on high modulus fibers and composites. The operator then returns to the driv- The publication is available in soft ing position, pulls the tug forward to cover or loose-leaf format from lock the hitch in place and is ready ASTM, 1916 Race Street, Philadel- to tow. No mirrors are needed and phia, PA 19103 U.S. Telephone (215) the exposure to operator back inju- 299-5400. ries is greatly reduced, according to the manufacturer.

Telescoping Towbar For more information, contact Ron Dossat, Tronair Inc., 1740 Eber Road, For Safer Operation Holland, OH 43528 U.S. Telephone (800) 426-6301. Fax (419) 867- Tronair Inc., manufacturer of ground 0634. support equipment, has developed two telescoping tow couplers, one designed for aircraft weighing less Combination Socket than 100,000 pounds and a larger Fits Square and model for heavier aircraft. Hex Fasteners The telescoping coupler is said by the manufacturer to be safer and to The Wright Tool Co. has developed

18 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 an eight-point combination socket payout boxes for ease of use in main- that can be used on both square and tenance applications.

Heli-Tube Cable Wrap is an expand- able plastic cable harness and abrasion protector which is recognized by Underwriters Laboratories (UL) for specific temperature and flam- Photograph mability ratings. Technicians can not available. protect exposed wiring runs or flex-

hex fasteners of the same size. The dual-purpose sockets can reduce the number of tools required for technicians involved in maintaining ground Photograph equipment in addition to aircraft. not available. The manufacturer states that these sockets provide full bearing and snug fit on both types of fasteners. Sock- ets are available in 1/4-, 3/8-, and 1/2-inch drive sizes.

More information is available from the Wright Tool Co., One Wright ible hoses from abrasion and chaff- Place, Barberton, OH 44203 U.S. ing by the installation of the proper type of wrapping. The spiral cut of the wrap allows it to be installed Spiral Wrap around existing wire runs and installed plumbing without disconnect- Protects Wiring ing or disturbing the installation.

The M.M. Newman Corp. supplies For more information contact the spirally cut cable wrap in six materi- M.M. Newman Corp., 24 Tioga Way, als and seven sizes. The materials P.O. Box 615, Marblehead, MA can be supplied on spools or in 01945 U.S.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991 19 Temperature age from overheating. The manufacturer claims that the decals stick Monitoring Decals to most clean surfaces and resist ex- Detect Overheats posure to solvents, fuels, grease, oil, water and steam. Wahl Instruments Inc. has developed a line of high temperature decals that Temp-Plates are lot tested for accu- are capable of measuring surface racy and can be used to detect tem- temperatures as high as 500 degrees peratures from 80 to 340 degrees F F. The Temp-Plate decals are avail- in Mylar material and from 350 to able in a variety of shapes and sizes 500 degrees F in Kapton material. with from one to 15 separate tem- Stainless steel decals can be used at perature increments. temperatures up to 1,100 degrees F.

Technicians can use these irrevers- For additional information, contact ible temperature decals to monitor Wahl Instruments, Temp-Plate Divi- the temperature of bearing housings, sion, 5750 Hannum Avenue, Culver heat exchangers, avionics or any City, CA 90231 U.S. Telephone (800) component which is subject to dam- 421-2853. Fax (213) 670-2840. o

Photograph not available.

20 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ JANUARY/FEBRUARY 1991