Foreign Object Damage: Elimination Should Be a Priority to Reduce Risks to Personnel and Equipment

by John F. O’Neill Jr. JAYFON Enterprises Aerospace Consultants

Foreign object damage (FOD) costs been damaged by foreign objects. the U.S. aviation industry alone more than US$1.25 million in damages One of the classic turboprop FOD each year, but the problem is shared events occurred some years ago at by non-U.S. airlines worldwide. what was then Allegheny Airlines. The inaugural flight of the Convair 540, Contrary to general opinion, FOD is which was to have initiated prop-jet not just a jet engine problem. Tur- service between Pittsburgh and Phila- bine jets, turbo-props, reciprocating delphia, Pennsylvania, taxied from the engine aircraft and rotorcraft are all gate with a full load of executive pas- subject to varying degrees of FOD. sengers and media representatives If an aircraft has an engine or a pro- when the left prop lifted an improp- peller, it is susceptible to FOD. Even erly secured fueling pit manhole cover, auxiliary power units (APUs) have resulting in major damage to prop and

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 1 engine. The total length of the inaugu- involving ingestion of parts of the ral “flight” was about 50 feet. aircraft such as fueling caps and ac- cess panels secured improperly. Also Damage to turboprop engines is not hazardous are chunks of ice formed as common as in jet engines, be- from leaking water service fittings or cause the inlets are generally smaller from in-flight ice buildup that breaks and the propeller serves as a first away into the airstream and the “blue line of defense. Nevertheless, first- ice” buildup that results from leaking stage impeller nicks and scratches lavatory servicing fittings. are caused when small stones and debris are picked up from the run- A Boeing 727 lost its right engine way during propeller reverse pitch during flight when the torque result- operation after landing. ing from the almost instantaneous freeze-up of the engine, following the ingestion of a large chunk of FOD Is Rough blue ice, exceeded the shear rating of the engine mounting bolts. On Turbines While little can be done to prevent Turbofan engines are not nearly as in-flight bird ingestion and the shed- forgiving as turboprops. While cases ding of routine ice buildup, we can of in-flight engine ingestion are more improve inspection and maintenance plentiful, the most serious incidents practices regarding fuel caps, access generally occur on the ground. panels, and water and lavatory ser- vice panels. Figure 1 (page 3) shows The most common in-flight FOD is six days’ of trash collected during caused by birds. Hundreds of in- consecutive sweepings on the ramp stances of in-flight bird ingestion area of a major airport. It is an as- have been reported, ranging from a sortment typical of what can be single bird in a single engine to sev- found on almost any airport ramp — eral birds in more than one engine. soft drink cans, a smokeless tobacco In some cases, pilots elected to re- can, valet bag hang-up hooks, a turn to the departure airport. Other wheel from a suitcase, tags, snaps, incidents resulted in an in-flight buckles and straps from luggage shut-down of one engine. But in the items, coat hangers, nuts, bolts, a majority of reports, the flight con- spoon, cotter keys, safety wire scraps tinued to its normal destination. and miscellaneous metallic junk that could destroy an engine or tire. Less common, but more dangerous, are the occasional in-flight incidents Figure 2 (page 3) shows some un-

2 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 Photo not available.

Figure 1 usual trash picked up from the ramp Figure 3 shows a bolt that has com- and deposited in an FOD box at- pletely pierced the blade. Figures 4 tached to a tug. The quantity of and 5 (page 4) show how extensive unsqueezed pop rivets testify to poor fan blades can be damaged by foreign FOD awareness and lack of concern object ingestion. Foreign object de- for maintenance costs. bris may come from a number of sources, as the examples show, but The following illustrations demon- one often-overlooked area of poten- strate what these bits of trash can do tial FOD trouble is sometimes right to the turbine blades of an engine. underfoot — loose blacktop patching.

Photo Photo not available. not available.

Figure 2 Figure 3

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 3 The source was a poorly stabilized gravel roof on an adjacent building.

Photo Reports indicate that not available. small stones, soil par- ticles and pieces of paving are more prevalent on opera- tional surfaces after a heavy rain or a sus- tained period of rain. Figure 4 This situation is be- lieved to result from Inspect ramps and taxiways. Check water-loosened debris from surface all patches for security and integrity. cracks and grassy areas being forced Check the joints between concrete to the surface where strong winds, slabs for loose or bubbled asphalt. It jet or prop blasts can blow them onto is possible for large chunks of as- runways and taxiways. phalt to stick to tires as heavy jets taxi across joints on a hot summer day. In an incident involving a DC-9, the asphalt came loose and flew into the suction pattern of the engine and was immediately ingested, causing more than $250,000 in damage.

Other common sources of FOD are dumpsters and trash containers Photo placed (with good intentions) on not available. ramps or at gate areas, but later al- lowed to fill to overflowing because of inadequate pickup schedules.

One need not look far or wait long to find FOD incidents waiting to hap- pen. The ramp area at one airport was frequently strewn with gravel, particu- Figure 5 larly after strong winds or heavy rains.

4 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 Even a mechanic’s uniform jacket too close to the inlet of a wing- (complete with his name patch) was mounted jet engine. According to recently retrieved from an active run- the report, “the suction force pulled way. Investigation revealed that he him toward the inlet. His hat and had placed it on the landing gear headphones were ingested, but for- while working on an aircraft and for- tunately he was able to save himself got to remove it before the aircraft by hooking his elbow around the departed. nose cowl lip.”

These near tragedies are a reminder Ground Personnel Also that the suction forces of a jet engine constitute a danger to anyone who is Exposed to Risk present in the area of an operating engine. A lack of awareness or un- Ground personnel risk being injured derstanding of the invisible forces sur- by turbofan engines if simple pre- rounding the engine inlet fosters com- cautions are not followed. placency among ramp personnel who work in the vicinity of engine inlets According to Boeing Co. data, 13 while engines are running. instances of ingestions associated with ground personnel were reported Figure 6 (page 6) illustrates the for the B-737 aircraft alone in a four- strength of the pulling forces near year period. Eight incidents involved the inlet of a wing-mounted engine personnel while troubleshooting en- operating at takeoff thrust. While the gine oil leaks, three while perform- forces listed in this chart are based ing engine trim, one while adjusting on a DC-10 engine, forces of this engine oil pressure and one during magnitude are typical for most wing- refueling operations. mounted engines.

In one incident, a mechanic was The pulling force felt by a person sucked backwards into an engine but too close to a jet inlet is the same managed to hang on to the nacelle force felt in a strong wind, except inlet. Although his coat was burned that a wind of 25 mph (40 kilometers from the friction of the spinner on per hour) only exerts a force of 20 his back, he emerged from the inci- pounds (9 kg) on a person of average dent frightened but uninjured. size. By comparison, a force of about 1,000 pounds (450 kg) is exerted on The McDonnell Douglas Service a person standing about a foot in Magazine reported on the experience front of a turbine engine operating at of an airline employee who ventured takeoff thrust. Even with the engine

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 5 tance between the inlet 1,000 (4.45) lip and the object de- 900 creases. Moving from a (4.00) point three feet (91 cm) 800 (3.56) from the lip to half this 700 distance increases the (3.11) pulling force from about 600 150 pounds 67.5 kg) to (2.67) 600 pounds (267 kg), or 500 (2.22) four times greater. 400 Merely turning the body (1.78) from profile to full face 300 (1.33) can double the force, and

Pulling Force in Pounds (Kilograms) 200 standing up from a (0.89) crouched position can

Pulling or Suction Force as a Function of Distance 100 triple the effects. (0.44)

6 5 4 3 2 1 0 Not only do the pulling (1.83) (1.52) (1.22) (0.91) (0.61) (0.30) forces increase rapidly as Distance from Inlet in Feet (Meters) an object moves toward Source: Boeing Co. the inlet, but airflow di- Figure 6 rections change rapidly around the inlet and can at idle, the pulling force is greater cause a body passing through the dif- than 300 pounds (135 kg). ferent directions of airflow to twist and tumble out of control. In addi- Considering that a person with noth- tion to these dangers, natural winds ing to hold onto can offer only about and uneven forces caused by sudden 95 pounds (42.75 kg) of resistance gusts can expand the normal danger by skidding on the bottom of his or area. Moreover, buildings, fences, and her shoes, the force of an idling en- the aircraft fuselage and wings can gine is sufficient to pull someone create highly localized wind forces into the spinning compressor blades. and unpredictable shears that will add It is certainly enough to pull in loose to the inlet-induced flow field, re- articles of clothing, hats, rags and quiring additional safety margins. even small notebooks from shirt or jacket pockets. The fact that an engine is small or running at idle is no excuse for a As Figure 6 illustrates, the pulling casual attitude. Although the airflow force increases rapidly as the dis- of a smaller engine is less, the suc-

6 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 tion forces are just as powerful as power units and radio test sets ingested those produced by larger engines. are well known to most ground per- Even though engines are not usually sonnel. Consider the following: run at high thrust in maintenance, ramp or terminal areas, the throttles ¥ An aircraft from Argentina re- could be advanced without warning quired extensive repairs following ground personnel. a collision with a horse. The engine manufacturer’s local rep- Never leave an auto throttle system resentative said in his report that activated while running an aircraft the engine had ingested parts of engine on the ground. Pull circuit the animal and a “large quan- breakers and install lockout rings, tity of pre-processed hay.” or remove units or connectors and tag the controls with red warning ¥ In another incident, a turbo-prop tags. Many acts can cause uninten- aircraft tangled with a pheas- tional throttle advancement. ant. The remains of the bird passed through the propeller and Every aircraft manufacturer publishes both impellers and wedged be- data outlining the dangerous areas tween the turbine plenum and around engine inlets. Know these ar- the combustor, causing a flame- eas for all aircraft that you normally out. The aircraft landed safely handle or service. Make sure that all and the engine was removed and personnel with ramp access know and sent to the manufacturer for re- understand these hazards. If you have pair. But it sat in its sealed ship- a normal run-up area, paint wheel ping container for a couple of locator marks on the ramp and out- weeks in 110-degree F (43.3- line the engine hazard areas. Also degree C) weather. When the have personnel oversee visitors or container was opened no one strangers who are on the ramp. could get near enough to disas- semble it until it had aired for Although FOD is never funny (only another few weeks. expensive and frightening), some of the FOD reports are indeed bizarre. If it is movable and hangs around an Rotorcraft Are Not airport, chances are that it has tried to go through an engine — with varying Immune from degrees of success. The numbers of FOD Events flight bags, valet bags, flight and main- tenance manuals, work stands, lad- “Foreign object damage? Not on ro- ders, tools, tool boxes, portable lights, torcraft! It’s the downwash, you

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 7 know. Blows all the junk off the pad. or worn over the shoulders. These We don’t have the problem fixed- bags provide a constant reminder and wing aircraft do. Those wing- a convenient receptacle for debris mounted engines in particular are and are periodically emptied into just big vacuum cleaners!” bright red FOD trash cans located conveniently around work areas. That is what many helicopter operators believe about FOD and Winter also poses potentially seri- rotorcraft. ous FOD problems. At an airport just after a heavy snowfall, the high- Helicopter turbine inlets are higher ways had been plowed and salted, off the ground and many have inlet and the airport roadways were screens. Tail rotors are generally plowed and sanded. In front of a much higher than fixed-wing props. corporate hanger, a helicopter was Movement on the ground at speeds picking up several passengers. A high enough for tires to pick up de- large limousine drove onto the pad bris and fling it into inlets or rotors and parked close to the entry door. is very rare. While it was parked there, all four fender wells deposited large globs Nevertheless, helicopters do encoun- of snow and slush (well laced with ter FOD problems. They are differ- highway salt) onto the tarmac, where ent from the problems experienced it continued to melt. by fixed-wing machines, but still a problem. The limousine departed, driving much of the snow into a thin layer of slush. Engine manufacturers and repair The passengers and the flight crew agencies say they see damage from walked through this mess and boarded the ingestion of nuts and bolts, bits the aircraft. At takeoff, the downwash of safety wire and an occasional tool kicked up a lot of salt-laden moisture — most left inadvertently in the in- that drifted across the ramp and settled lets or ducts during maintenance. on two corporate jets. After the depar- ture, someone dutifully brushed up the Airframe manufacturers all have ac- residue and shoveled it onto a snow tive FOD programs. Boeing Heli- bank beside the ramp where it contin- copters considers the elimination of ued to melt and run across the ramp. FOD to be a factor in job security Three aircraft were immediately con- and maintains a FOD hotline. In the taminated with corrosion-producing manufacturing area and on the flight- salts and more were exposed to salt test line, Boeing employees have contamination until rain had diluted bright orange bags clipped to belts the salts and washed them away. All

8 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 this happened because no one had tion program for your airport or fa- thought to restrict the limousine from cility. Airline maintenance supervi- entering the air operations area. sors usually have a program to con- trol FOD problems and usually share If snow is forecast, ensure that the their information with other opera- ramp areas are free of debris and not tors. Talk to airport operators or su- trapped or buried under the snow. pervisors. Schedule a walk on the Ramp taxiway and runway expan- ramp to collect trash. Call a session sion strips that were loosened dur- with other operators at your field and ing the summer may be pushed up schedule a cleanup, then display the and out when water collects under- results at a seminar on FOD. When neath, which expands when frozen. everyone sees the collected debris piled on a table, they will realize the Ramp vehicles with tire chains that seriousness of the problem. Call your have broken links are especially dan- engine manufacturer or overhaul gerous. Inspect chains carefully agencies. They are generally very co- when installing them and during use. operative and can often provide dam- aged parts, posters, films and video- Where multiple rotorcraft are oper- tapes for your seminar. ating close to each other, the clean- liness of the ramps and pads is ex- If your airport has a sweeper, vacuum tremely important because the and/or a magnetic pickup device, see downwash from one aircraft can pick when and where it is scheduled to up trash that can enter inlets and can be operated. If its use is not frequent cause rotor damage or erosion to enough, discuss the problem with nearby machines. airport management.

What can be done to prevent FOD? Commercial magnetic pick-up de- The process of eliminating or reduc- vices are relatively expensive, but I ing foreign object debris that causes saw a Jeep with a large electro-mag- damage begins with all employees, net hung from the snow plow sup- regardless of job or title. If you work port that operates satisfactorily. The at an airport or heliport, you can help. magnet was constructed of two three- No matter where you are, keep an foot diameter, half-inch soft iron eye out for debris on the ramp, pad, plates, with the coil wound from a hangar and shop floors. If you see couple of surplus power cords from something, pick it up. It is good exer- a 28-volt direct current (DC) air- cise and there will be one less hazard. craft power unit, powered by a 100- amp aircraft generator, and driven In addition, consider a FOD elimina- by the Jeep engine.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 9 Another approach is to install mag- ¥ Providing a flow of FOD in- nets on the bottoms of frequently formation and communication; used ramp vehicles. Check your lo- cal avionics shop for defunct mag- ¥ Organizing an FOD program netrons from the older radars (have or becoming an active partici- them take the tubes out) and you pant if such a program is in will have a powerful pickup device place; that works every time you cross the ramp. ¥ Involving your own personnel;

When conducting runway and taxi- ¥ Training all employees exposed way inspections, take a can of fluo- to areas where FOD exists or rescent spray paint and outline any can occur; areas of bad sealant, spalled or cracked areas, etc. This will alert ¥ Setting an example, by being vis- flight crews and assist maintenance ible and by picking up debris; crews in locating areas in need of repair. ¥ Holding employees and super- visors responsible for their Tool kits that have a molded cutout areas; for each tool make an inventory of all tools at the end of a job extremely ¥ Providing adequate receptacles simple and increases safety. One for trash and debris and assur- mechanic outlined all of his tools on ing timely pickup; sheets of 1/4-inch plywood cut to fit the drawers of his tool box. He then ¥ Appointing a supervisor for a cut out the outlines on a scroll saw, daily check of ramp, hangar, stained and varnished the plywood maintenance areas and taxiways; and secured the sheets to the drawer and bottoms with double faced tape. The red bottom of the drawer shows ¥ Preventing vehicles that have through the cutout if a tool is not in been operated on off-airport its proper place. It is convenient, at- highways from driving onto an tractive, efficient and, above all, a air operations area. big contribution to safety. If you decide that FOD prevention FOD problems can be avoided by: is not your job, chances are FOD will not be prevented. A good FOD ¥ Stressing the importance of the program can save thousands of dol- problem; lars, reduce delays, cancellations,

10 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 expensive down time, and protects where he served in a variety of jobs and lives. o positions, including director of de- velopment engineering and man- ager of avionics, systems and equip- About the Author ment engineering. He is a frequent John F. O’Neill Jr. is president of contributor to technical aviation JAYFON Enterprises, an aviation publications and is a U.S. Federal consulting company. O’Neill was Aviation Administration-designated employed for 28 years at USAir, engineering representative.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 11 NEWS & TIPS

ANSI Standard to Be Individuals interested in this service should contact ANSI’s Customer Ser- Made Available via vice Department at (212) 642-4900. CD-ROM

All standards published by the Industrywide American National Standards Insti- Standards for tute (ANSI) are now available in CD- Piston-powered ROM (compact disc-read only memory) format. A contractor has Aircraft Engine Oils scanned ANSI standards cover-to- Issued by SAE cover and integrated the standards with the latest CD-ROM technology The Society of Automotive Engi- and high-speed search and retrieval neers (SAE) recently published the software. This service will allow us- first industrywide standards for pis- ers with personal computers with ton-powered aircraft engine oils. The CD-ROM capability to locate ANSI new standards define specifications standards within seconds. Bulky and for all grades of oil, including multi- time-consuming paper files of ANSI viscosity oils. These new standards standards can be eliminated. are a result of five years of work by representatives from SAE, the U.S. In announcing this service, ANSI Navy, various aircraft engine manu- President Manuel Peralta said: “In facturers, research labs, testing fa- the past, ANSI members have ex- cilities and oil suppliers. pressed the desire to gain quick and easy access to American National Dennis Boggs, lubricants technical Standards. Keeping pace with the director for Phillips 66, said: “The ever-changing world of high tech- industry needed a standardized ap- nology is a continuing challenge for proval system that would include ev- the Institute and the standards com- ery oil on the market today and munity. This service will allow the would encourage development of business community to use CD-ROM new oils.” Boggs added: “Standards technology in research, strategic for aviation oil really haven’t planning and standards operations.” changed much since the 1940s, but

12 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 the oil chemistry has.” prove RVI, Olympus has published a brief six-question mail-in card for Pilots and technicians will not see user response. The free textbook is any major differences in the oils. offered in return for completing the However, they should be aware of questionnaire. the new terminology that will ap- pear on labels and in literature. Technicians interested in receiving the questionnaire may contact Olympus Old New Corp., Industrial Fiberoptics Division, 4 Nevada Drive, Lake Success, NY Mil-L-6082 SAE J 1966 (This 11042-1179 U.S. specification now in- cludes aviation grades 65 and 100.) Training Offered in the Mil-L-22851 SAE J 1899 (This Human Element in specification in- Aviation for cludes ashless oils, as Maintenance Managers well as multigrade oils.) Richardson Management Associates Ltd., which has its head offices in Montreal, Canada, has announced a Free Textbook on training session designed to increase Remote Visual skills in managing people, conflict, authority, safety and performance for Inspection Offered maintenance managers and supervisors. The Olympus Corp., one of the lead- ing manufacturers of remote visual Courses are scheduled May 18-21, inspection (RVI) equipment used in 1993, in London, England, and June the aviation industry, is offering a 7-11, 1993 in Montreal, Quebec, free copy of a textbook, “The Sci- Canada. ence of Remote Visual Inspection,” to technicians who respond to a ques- For information contact: Richardson tionnaire included in one of Management Associates Ltd., 2054 Olympus’ recent mailings. Sherbrooke Street West, Suite 102, Montreal, Quebec, Canada H3H To maximize customer satisfaction 1G5. Telephone (514) 935-2593 or and exchange information to im- Fax (514) 935-1852. o

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 13 MAINTENANCE ALERTS

This information is intended to provide area. Airline officials stated, “This in- an awareness of safety problems so that cident did not affect the airworthiness they may be prevented in the future. of the aircraft in any way. It stemmed Maintenance alerts are based upon pre- from the failure of two individuals to liminary information from government perform their duties properly.” The agencies, aviation organizations, the press mechanic and an inspector responsible and other sources. The information may for the work were discharged, accord- not be entirely accurate. ing to an airline spokesman.

Investigators were particularly con- NTSB Reports Incident cerned about this incident because Similar to Fatal of its similarity to a maintenance error in 1991 when a number of Continental Express screws were left out of the horizon- Accident tal stabilizer leading edge, causing a crash that killed all 14 people on Investigators from the U.S. National board. In both cases, someone at the Transportation Safety Board (NTSB) commuter airline’s Houston base had have reported that a maintenance er- failed to reinsert fasteners after per- ror, similar to that which resulted in a forming maintenance. 1991 crash of a Continental Express EMB-120, forced a flight operated by the same carrier to return to the air- Faulty Wiring of port after takeoff on Dec. 9, 1992. The pilots reported that vibrations were Cockpit Voice noted in the control column shortly Recorders Found in after takeoff. The flight returned to Several Commuter the airport 12 minutes later. There were no injuries and no additional damage And Charter Airplanes was found on the aircraft. While investigating several small jet NTSB investigators found that 12 and turboprop aircraft accidents, the screws had been left out of the left U.S. National Transportation Safety aileron following maintenance in that Board (NTSB) found that the

14 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 recorded information on the cockpit that the erase-enable jumper is prop- voice recorder (CVR) was nearly erly installed. This inspection should useless in three instances. be completed within 120 days of the recommendation. All CVRs use a continuous tape that records the last 30 minutes (or 15 “Require B+D Instruments and Avi- minutes in some cases) of commu- onics to modify the self-test circuitry nications and conversation in the in its cockpit voice recorders (CVRs) cockpit. The continuous loop tape is so that the CVRs will fail the inter- erased just prior to passing over the nal self-test if the erase-enable recording head. In several of the ac- jumper is not installed. This modifi- cidents and incidents under investi- cation should be accomplished at the gation, the tape had not been erased next unit overhaul or within two and the recording was overwritten years, whichever comes first. on the previous recordings. The CVRs were installed on aircraft such “Require B+D Instruments and Avi- as the BAe Jetstream 3101 and the onics to revise the procedures con- Learjet series. All the CVRs were tained in its approved installation manufactured by B+D Instruments manual to include a test or tests that and Avionics. will detect a cockpit voice recorder installation with an inadequate erase- Analysis of the installation disclosed enable jumper placement.” that the circuit that should have en- abled erasure of the tape under nor- mal operation had not been properly connected. As a result, the erase func- Lack of Lubrication tion was disabled and the tape was Cause of DC-8 being constantly overwritten. Because Landing Gear Bogie of a peculiarity in this particular unit, this fault is not recognized in the nor- Beam Failure mal self-test of the CVR system. A DC-8-71F aircraft operated by a On Feb. 8, 1993, the NTSB recom- package carrier recently experienced mended that the U.S. Federal Avia- a failure of the swivel bogie beam tion Administration (FAA): assembly of the left main landing gear bogie beam while taxiing for “Require a one-time inspection of takeoff. The main landing gear was all aircraft equipped with a cockpit severely damaged. However, there voice recorder manufactured by B+D were no injuries to the crew and no Instruments and Avionics to ensure structural damage outside of the gear.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 15 The swiveling bogie beam assembly The current manufacturer’s mainte- is incorporated in the design of the nance manual calls for lubrication main landing gears of the DC-8 se- of the bogie beam swivel joint(s) ries 20, 30, 40, 50, 60 and 70 air- every 350 to 400 flight hours. It was planes. The swiveling bogie beams discovered, however, that the on- connect the forward set of wheels to aircraft maintenance planning the aft set of wheels, permitting (OAMP) document for the 70 series sharper turn angles during taxiing DC-8 does not include a specific task than could be achieved without the card to lubricate these points. swivel feature. The primary compo- nents of the swivel bogie beam as- On May 17, 1990, as the result of a sembly are the aft and the forward failure in the swivel joint, the manu- bogie beams, which are assembled facturer published a service letter together by a swivel pin through two alerting operators of DC-8-50/60/70 lugs on the forward beam and two airplanes to the importance of proper lugs on the aft beam. lubrication of this assembly and reit- erated the recommendation to lubri- A U.S. National Transportation Safety cate these swivel joints each 350 to Board (NTSB) investigation of this 400 flight hours. On May 9, 1991, as incident disclosed that a separation a result of another bogie beam fail- of the bogie beam assembly occurred ure, the manufacturer issued a revi- in the upper and lower swivel pin sion to this letter calling for the lu- lugs of the forward bogie beam. Met- brication interval to be reduced to 75 allurgical examinations of the failed flight hours. No action was taken to lugs disclosed that the upper lugs frac- require that the lubrication period be tured because of overstress; however, included in the operator’s routine the lower lug fractures stemmed from maintenance program. During the in- two small areas of stress corrosion vestigation of the incident that oc- cracking. Extensive pitting corrosion curred on August 21, 1992, the NTSB was found in both origin areas. alerted the manufacturer to the omis- sion of the lubrication task from the Although the lugs are equipped with OAMP and a change was subse- grease fittings, there was little, if any, quently proposed calling for this lu- lubricating grease evident in the brication at a 75-hour interval. swivel joint. Since 1969, there have been 22 service difficulty reports Because lubrication of the swivel pin (SDRs) of swivel bogie beam fail- joint in the bogie beam assembly ures. All these failures were attrib- has not been included in the OAMP uted to stress corrosion or excess wear document, the NTSB is concerned because of insufficient lubrication. that other operators of the DC-8 may

16 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 not have lubricated these joints on a one-time inspection for evidence of regular or sufficiently frequent ba- excessive wear, pitting corrosion, sis. Consequently, the NTSB has rec- and stress corrosion cracking in the ommended that the U.S. Federal swivel joints of bogie beams of all Aviation Administration (FAA): main landing gears of DC-8 airplanes that incorporate a swivel bogie beam “Require operators of DC-8 air- configuration. During this inspec- planes to lubricate the main landing tion, special attention should be gear bogie beam swivel joints at an given to examination of inside di- appropriate interval. ameter surface and unpainted areas of the upper and the lower swivel “Issue an Airworthiness Directive to pin lugs in the forward and aft bogie require, within a reasonable time, a beams.”o

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Low-cost Device The ultrasonic signal is sensed by the instrument’s probe and transmit- Detects Leaks ted to a piezo-ceramic transducer that converts the mechanical vibration to A non-invasive leak detection in- an electrical signal. This signal is strument, the Leakcheck Contact processed and amplified by the unit’s Probe, has been introduced by ICC electronics and is heard through Federated. The unit is designed to identify changes in the amplitude of the ultrasonic signal emitted by any movement within a mechanical system. Photo not available. The manufacturer claims that the unit can be used to detect leakage through a check valve or shut-off valve. The liquid or gas flow emits a steady rushing sound. A properly seated valve should emit no sound.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 17 headphones. materials are also available.

Mechanical problems in gearboxes and other rotating components also can be detected by this system, ac- cording to the manufacturer of the unit.

For more information, contact: ICC Photo Federated, 2200 South Street, not available. Racine, Wisconsin 53404 U.S. Tele- phone (414) 639-6770.

Expandable Plastic Cable Wrap Eases Line Application The spiral wrap makes the product especially useful for protecting wir- The M.M. Newman Co. produces a ing bundles while allowing for ease full line of spirally cut cable wrap of break-outs and/or re-routing of and abrasion protective wrap that it wiring. The product is said to resist says can be easily applied without abrasion and dampen vibration of tools. The flexibility and ease of ap- wiring and plumbing installations. plication make this product espe- For more information, contact: M.M. cially useful to the line technician Newman Corp., 24 Tioga Way, making repairs or modifications to Marblehead, Massachusetts 01945 existing installations because the U.S. Telephone (617) 631-7100. wrap can be installed without dis- connecting terminal connectors or harnesses, the company said. Replacement Power According to the manufacturer, Heli- Unit Alternative to AD Tube¨ Spirally Cut Cable wrap is Inspections Underwriters Labs (UL)-approved and is available in clear or colored Aerospace Lighting Corp. has re- polyethylene, UV-resistant polyeth- cently introduced a replacement ylene and fire-resistant white or power unit for aircraft interior fluo- black polyethylene. Natural and rescent lighting systems that are sub- black nylon or Teflon¨-based ject to the repetitive inspection of

18 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 U.S. Airworthiness Directive (AD) information, contact: Aerospace 90-14-06. Repetitive inspections of Lighting Corp., 101-8 Colin Drive, affected installations are required by Holbrook, New York 11741 U.S. this AD to prevent overheating or Telephone (516) 563-6400 or Fax fire if there is a faulty or broken (516) 563-8781. connector.

The manufacturer states that the U.S. Ansul Announces Federal Aviation Administration (FAA) has approved the use of its Environment-friendly protected power units as a direct re- Fire Extinguishing Gas placement for the original units that are subject to the repetitive inspec- Halon fire extinguishers have proven tions. The unit is said to provide a to be very effective and are widely unique fault-sensing capability in- used. Halon is, however, a member stantly shuts the unit down in the of the freon family of chemicals and event of open or short circuits, bro- has been found to be harmful to the ken output wires, improperly in- environment because of its ozone- stalled or broken lamp connectors layer depleting characteristics. The and a variety of excessive voltage industry now plans to phase out conditions including arcing. production of halon. U.S. industry intends to ban production of halon by December 1995, and sources in- dicate that a future international meeting may suggest a worldwide Photo ban as early as 1994. not available. With the introduction of a new agent labeled “INERGEN,” Ansul now claims to have “the environment- friendly halon replacement.” Ac- cording to Ansul, INERGEN is a mixture of three inert gases: ap- The installations are used in a wide proximately 52 percent nitrogen, 40 variety of airline and corporate inte- percent argon, and eight percent car- rior installations and the manufac- bon dioxide. As a gaseous extin- turer claims that this part has re- guishing agent, the manufacturer ceived FAA approval as a claims it is well suited for the terminating action to the repetitive protection of sensitive electronic inspections of this AD. For more equipment.

FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993 19 Ansul plans to introduce a Under- straight-threaded port, an integral writers Laboratory (UL)-listed and “O-ring-type bead” on the plug fits Factory Mutual-approved INERGEN snugly into the bevel of the threaded fire suppression system for the North opening, preventing oil or fluid leak- American market this year. age. At the same time, according to INERGEN systems are already ap- Caplugs, a lip on the flange of the proved and in use in some European plug compresses against the boss re- countries, according to the maker. cess, providing a positive seal that keeps paints and/or other contami- For more information, contact: Ansul nants from the sealing surface. Fire Protection, One Stanton Street, Marinette, Wisconsin 54143-2542 The RPO Series of Caplugs is de- U.S. Telephone (715) 735-7411. scribed on product sheet RPO 991 and is available with a sample kit of new plugs. The design is said to be very cost-effective because it elimi- New Type Caplug nates the need for a separate O-ring Protects Sealing Area seal and the added labor to install it. The plugs have a serrated top for As Well as Opening hand installation as well as a slot for screwdriver tightening and a 12- The Caplugs Division of Protective point head for socket wrench use. Closures Co. has recently introduced a series of threaded plastic plugs that, For a free sample kit and further according to the manufacturer, pro- information contact: Caplugs Divi- vide a unique double-sealing feature. sion, Protective Closures Co., 2150 Elmwood Avenue, Buffalo, New When screwed into a standard Soci- York 14207 U.S. Telephone (716) ety of Automotive Engineers (SAE) 876-9855. o

20 FLIGHT SAFETY FOUNDATION ¥ AVIATION MECHANICS BULLETIN ¥ MARCH/APRIL 1993