One advantage of the externally accessible engine equipment and peripheral devices is the possibility of inspecting and testing them with relative ease. Inspections can serve as a temporary measure in acute cases, when remedies can not be implemented sufficiently quickly for temporal and logistic reasons. Examinations can be conducted as separate procedures, but should preferably be done during maintenance and inspection. They can be specifically designed for the problem at hand in various ways. The following are several examples:
Knowledge of the frequency of the damage types is helpful for designing preventive measures (Fig. "Statistic of accessory equipment damages and problems"). Typical measures to minimize risks are:
Instrument and sensor errors:
Figure "Fastening of accessory equipment": Accessory equipment can be subjected to high dynamic (LCF, HCF) and static loads (middle diagram). Special types of vibration are excited, depending on the excitement mechanism and mass distribution. These vibrations can cause both the aggregates and the fastening systems (bottom diagram) to fail. Because fasteners and fastened masses reciprocally influence one another, even “minor changes” (e.g. during modernization) require realistic verification in tests close to operating conditions (Ill. 188.8.131.52-5).
11.2.5-1 NTSB Identification: FTW94IA198, incident from June 17, 1994.
11.2.5-2 NTSB Identification: LAX94FA323, incident from August 13, 1994.
11.2.5-3 NTSB Identification: LAX87IA029, microfiche number 34708A, incident from October 31, 1986.
11.2.5-4 S.W. Kandebo, “USAF Targets Engine Mishaps”, periodical “Aviation Week & Space Technology”, March 29, 1999, pages 84 and 85.
11.2.5-5 M. Miller, J. Colehour, K.Dunkelberg, “Engine Case Externals Challenges and Opportunities”, Proceedings Paper of the “Isromac-7, the 7th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery”, February 22-26, 1998, pages 1604-1611.
11.2.5-6 G. Norris, “Boeing tackles 777 power problems”, periodical “Flight International”, 18-24 August,1999, page 6.
11.2.5-7 “FAA takes action on R-R AE3007 FADEC transistor failures”, periodical “Flight International”,12-18 September, 2000, page 14.
11.2.5-8 R.L.Johnson, R.C. Bill, “Fretting in Aircraft Turbine Engines”, Proceedings AGARD-CP-161 of the “Specialist Meeting on Fretting in Aircraft Systems, pages 5-1 bis 5-13.
11.2.5-9 P. Phelan, ”'Green' fuel sparks off fears of engine failures“, periodical “Flight International”, 17-23 August, 1994, page 6.