AIRCRAFT
AIRWORTHINESS
INSPECTION
INTRODUCTION
In order to ensure that aircraft are maintained to the highest standard of air-worthiness, they are managed and inspected under FAA-mandated and -approved inspection programs. Inspection programs must ensure the aircraft is airworthy and conforms to all applicable FAA aircraft specifications, type certificate data sheets, airworthiness directives, and other FAA approved data.
Inspection planning is organized around an aircraft's age, utilization, environmental conditions, and the type of operation. Examples include changes in temperature, frequency of landings and takeoffs, operation in areas of high industrial or environmental pollutants, and passenger or cargo operations. To assure proper maintenance, each inspection interval must be stated in terms of flight hours, calendar times, and cycles (the number of take-offs and landings the aircraft makes). As part of the aircraft's certification process, the aircraft manufacturer and the FAA agree on the frequency for inspection requirements on the aircraft as well as functional checks of each system. This forms the basis for the maintenance program when the aircraft is in service. Every system on the aircraft has its own inspection requirements. Typically, major system-inspection requirements are synchronized to minimize aircraft downtime and to eliminate a duplication of effort. However, it is common to have completely separate inspection cycles for the primary aircraft structure and its engines.
On a base level, "inspect" means to examine by sight and touch. When performing inspections, the inspector measures and checks conditions against established guidelines. An inspector must be able to recognize defects and be aware of failure modes. Aircraft inspections include manual tasks such as initiating the inspection, accessing the aircraft, and responding to problems. In addition, cognitive tasks, such as search and decision making skills, are also used in the inspection process. An inspector should be able to identify and determine the accept-able degree of deterioration or defects permitted by the manufacturer's manuals or other approved data. Initiating the inspection can begin by reviewing a maintenance checklist or work card, and under-standing the area or item to be inspected. Maintenance checklists for small aircraft (under 12,500 lbs. gross takeoff weight) must conform to FAR Part 43, Appendix D. Most aircraft manufac-turers provide inspection checklists regarding the specific aircraft they produce. Small aircraft manu-facturers' inspection schedules meet the minimum requirements of Appendix D and contain many details covering specific items of equipment installed on a particular aircraft. In addition, they often include references to service bulletins and ser-vice letters, which might otherwise be overlooked. As long as they meet the minimum requirements of Part 43 Appendix D, approved inspection checklists may also be customized and made more extensive to meet the needs of an individual owner/operator. Large and turbine powered aircraft are inspected under more encompassing inspection programs tai-lored to their specific type of aircraft and operating conditions.
Aircraft are subject to many required inspections. These range from the basic pre-flight inspection, a daily walk-around inspection, to extensive heavy maintenance checks, which involve significant dis-assembly and detailed inspection of the aircraft.
PRE-FLIGHT INSPECTIONS
An FAA approved Minimum Equipment List
(MEL) includes equipment that, if inoperative, may
either ground the aircraft or allow it to be flown with flight restrictions deferring maintenance for specific periods of time. An aircraft's MEL is spe-cific to its precise configuration and serial number. When a MEL item is discovered inoperative, it is reported by making an entry in the aircraft's main-tenance record. The inoperative equipment is either repaired or deferred according to the MEL instruc-tions prior to further flight. After repair, record an airworthiness release or aircraft maintenance entry to remove the flight restrictions. [Figure 17-1] During a pre-flight inspection, all of the aforemen-tioned items are verified by the pilot along with per-forming a visual walk-around inspection. The walk-around entails referencing a pre-flight checklist and looking for obvious problems such as nicks and cracks on the propeller, missing hardware, properly inflated tires, and flight control damage. Although pre-flight checklists are primarily designed for the flight crew, an aircraft technician should also perform these checks before operating an aircraft. [Figure 17-2]
FAR PART 91 REQUIRED
INSPECTIONS
FAR Part 91 contains the General Operating and Flight Rules of aircraft and specifies the inspections required to determine the airworthiness of an air-craft. Subpart E of Part 91 deals with and describes the approved inspection programs for aircraft operations.
Small aircraft are governed by subpart E and must have a complete annual inspection every 12 calen-dar months. If the aircraft is operated for compensa-tion or hire, it must have a "100-hour" inspeccompensa-tion of the same scope as an annual inspection performed every one hundred hours of operation. Large and turbine powered, multi-engine aircraft require more specific detailed inspections that are tailored to their particular flight operations.
ANNUAL INSPECTION
The most common type of inspection required for small general aviation aircraft is the annual
inspec-Aircraft Airworthiness Inspection 17-3
ROCKWELL COMMANDER 500A REGISTRATION NO. OOXYZ SERIAL NO. 500A3848Q
21-1 REVISION 2 4/20/00 2. NUMBER INSTALLED
SYSTEM & SEQUENCE NUMBERS
3. NUMBER REQUIRED FOR DISPATCH 4. REMARKS OR EXCEPTION 21. AIR CONDITIONING 1. COMBUSTION HEATER 2. HEATER VENTILATION FAN C C
. (M) MAY BE INOPERATIVE PROVIDED: a. MAINTENANCE PULLS AND CAPS
JANITORIAL HEATER CIRCUIT BREAKER.
MAINTENANCE:
A certificated mechanic shall perform an inspection of the combustion heater. Remove nose section top access panel, a. Inspect the heater for general security,
damage and fuel leaks, Inspect for damage to any of the associated systems adjustment to the heater, b, Replace access cover.
c. Inspect heater fuel pump located inside the nose wheel well area mounted against the top of the wheel well. Check for security, damage and fuel leaks to heater fuel pump,
d, Inspect fuel cycling solenoid valve and fuel safety solenoid valve located in the wheel well area against the lower bulkhead area looking aft, Check for security, damage and fuel leaks to any associated fuel lines in this area.
Enter a statement of work performed in the aircraft flight log and install placard.
. MAY BE INOPERATIVE PROVIDED: a. COMBUSTION HEAER IS NOT UTILIZED ON
THE GROUND,
b. HEATER IS TURNED OFF PRIOR TO LANDING.
c. WINDSHIELD DEFOGGING IS NOT REQUIRED ON THE GROUND.
FINAL APPROVAL
FEDERAL AVIATION AMINISTRATION
NM-FSDC-MINIMUM EQUIPMENT LIST 13-12 04/20/00 REVISION 3
Figure 17-1. A Minimum Equipment List (MEL) includes items of equipment related to the aircraft's airworthiness. It does not con-tain items such as wings, flaps, and rudders, which are obviously required. MELs also list equipment that may be deferred with
3'
CD
tn CD
Aircraft Airworthiness Inspection 17-5
tion. Within every 12 calendar months, the aircraft must have a complete inspection performed to determine if the aircraft meets all the requirements for its certification. A calendar month is one that ends at midnight of the last day of the month. For example, if the inspection was completed on January 14, it will remain valid until midnight January 31, the following year. An aircraft may not be over flown beyond the annual due date unless a special flight permit is obtained authorizing the air-craft to be flown to an inspection facility.
The FAA specifies the details of both an annual and a 100-hour inspection in Appendix D of 14 CFR Part 43. Appendix D includes a list of items entitled, "Scope and detail of items (as applicable to the particular air-craft) to be included in annual and 100-hour Inspections." This list is not all-inclusive to each air-craft manufactured, but typical of the scope of inspec-tion the FAA requires. The manufacturer of the aircraft provides a detailed inspection checklist, which meets the minimum requirements of Appendix D, in the ser-vice manual for each aircraft it produces.
Figure 17-3 represents a portion of a typical manu-facturer's inspection checklist. The checklist shows the recommended time intervals of items inspected under a progressive inspection program, a complete inspection, or annual, including all 50,100 and 200-hour items in addition to any special inspection items.
Annual inspections must be performed by an A&P technician holding an Inspection Authorization (IA) or an inspector authorized by a certified repair sta-tion with an airframe rating. If the aircraft passes the inspection, the inspectors must write up the inspec-tion results in the maintenance records, and approve the aircraft for return to service. If for any reason the aircraft does not meet all of the airworthiness requirements, the inspector must provide a list of discrepancies and unairworthy items to the aircraft owner. The inspector may not delegate any inspec-tion responsibility to another A&P or repairman, nor may the inspector merely supervise the inspection. However, as long as the discrepancy found does not require a major repair, any certified A&P technician may correct each discrepancy the inspector listed, and then approve the aircraft for return to service. The due date of the next annual inspection is then based on the date of the original inspection and not on the date the discrepancies were corrected. For example, if an aircraft's annual was completed on March 20, but a discrepancy repair was not com-pleted until April 15, the next annual is still due March 30 the following year.
If the aircraft does not pass the annual inspection, it may not be flown until the unairworthy condition is corrected. However, if the owner wants to fly the aircraft to a different repair location, a special flight permit may be obtained to ferry the aircraft to that alternate repair location.
100-HOUR INSPECTION
If the aircraft is operated for compensation or hire, it must be given a complete inspection of the same scope and detail as the annual inspection every 100 hours of operation unless it is maintained under an FAA-approved, alternative inspection program such as a progressive inspection program. In the case of a 100-hour inspection, the time limitation may be exceeded by no more than 10 hours of flight opera-tion while enroute to an inspecopera-tion facility. However, the excess time used to reach the inspec-tion locainspec-tion must be included in computing the next 100 hours of time in service. For example, if a 100-hour inspection was due at 1000 hours and the pilot over-flew the aircraft to 1008 hours to reach an inspection facility, the next 100-hour inspection is still due at 1100 hours of operation.
The difference between a 100-hour and an annual inspection is that a certified A&P technician may conduct the 100-hour inspection and approve the aircraft for return to service. The A&P technician who inspected the aircraft must make the proper entries in the aircraft's maintenance records and approve the aircraft for return to service before the 100-hour inspection is considered complete.
Like the inspector performing an annual, the A&P inspecting the aircraft may not merely supervise the inspection process. The maintenance technician performing the 100-hour inspection is responsible for approving the aircraft for return to service. In other words, the A&P signing off the aircraft must be the one who actually performed the inspection. However, the inspector may utilize other A&Ps or repairmen in the preparation for the inspection such as removing inspection panels, cowlings, and fairings. In addition, any certified A&P technician may repair and sign off any discrepancies found by the inspector as long as they are not major repairs or major alterations.
100-hour inspections may be signed off as annual inspections if an A&P mechanic holding an inspec-tion authorizainspec-tion (IA) completed the inspecinspec-tions. In a sense, the aircraft could have several annuals performed in one calendar year at each 100 hours of operation. However, a 100-hour inspection may not take the place of an annual inspection. If an aircraft is operated under the requirements of an annual
50 H O U R S 10 0 H O U R S 2 0 0 HO URS IAL I N SPEC T IO N I T EM X X X O AIRFRAME o
3
Ul Q m UJ UJ to 1 Aircraft Exterior • 2. Aircraft Structure ©3. Windows, windshield, doors and seals s
4. Seat stops, seat rails, upholstery, structure and mounting G 5. Seat belts and shoulder harnesses e
6. Control column bearings, sprockets, pulleys, cables, chains and turnbuckles 0 7. Control lock, control wheel and control column mechanism O 8. Instruments and markings s
9. Gyros central air filter • 13
10. Magnetic compass compensation 5
11. Instrument wiring and plumbing •
12. Instrument panel, shock mounts, ground straps, decals and labeling •
13. Defrosting, heating and ventilating systems and controls e
14. Cabin upholstery, trim sun visors and ash trays o 15. Area beneath floor, lines, hose, wires and control cables o 16. Lights, switches, circuit breakers, fuses and spare fuses e
17. Exterior lights Q
18. Pitot and static systems o
19. Stall warning unit and pitot heater • 20. Radios, radio controls, avionics and flight instruments a
21. Antennas and cables e
22. Battery, battery box and battery cables o
23. Battery electrolyte 14
24. Emergency locator transmitter G 15
25. Oxygen system 0
26. Oxygen supply, masks and hose • 16
27. Deice system plumbing
28. Deice system components •
29. Deice system boots ii
CONTROL SYSTEMS
In addition to the items listed below, always check for correct direction of movement, correct travel and correct cable tension.
1. Cables, terminals, pulleys, pulley brackets, cable guards, turnbuckles and fairleads 2. Chains, terminals, sprockets and chain guards
3. Trim control wheels, indicators, actuator and bungee 0
4. Travel stops
5. Decals and labeling a
6. Flap control switch, flap rollers and flap position indicator * 7. Flap motor, transmission, limit switches, structure, linkage, belt cranks, etc.
8. Flap actuator jackscrew threads •
9. Elevators, trim tab, hinges and push-pull tab 17 10. Elevator trim tab actuator lubrication and tab free-play inspection
11. Rudder pedal assemblies and linkage 18 12. External skins of control surfaces and tabs
13. Ailerons, hinges, and control rods © 14. Internal structure of control surfaces
15. Balance weight adjustment
I
SPECIAL INSPECTION ITEMS
1. First 25 hours, refill with straight mineral oil (MIL-L-6082) and use until a total of 50 hours have accumulated or oil consumption has stabilized; then change to ashless dispersant oil. Change filter element each 50 hours, or every six months.
2. Clean filter, replace as required.
3. Replace hoses at engine overhaul or after 5 years, whichever comes first. 4. General inspection every 50 hours.
5. Each 1000 hours, or to coincide with engine overhaul.
6. Each 100 hours for general condition, lubrication and freedom of movement. These controls are not repairable. Replace every 1500 hours or sooner if required. 7. Each 500 hours.
8. Internal timing and magneto-to-engine timing limits are described in the engine service manual.
9. Remove insulation blanket or heat shields and inspect for burned area, bulges or cracks. Remove tailpipe and ducting; inspect turbine for coking, carbonization, oil deposits and impeller for damage.
10. First 100 hours and each 500 hours thereafter. More often if operated under prevailing wet or dusty conditions.
11. If leakage is evident, refer to Governor Service Manual.
12. At first 50 hours, first 100 hours, and thereafter each 500 hours or one year, whichever comes first
13. Replace each 500 hours.
14. Check electrolyte level and clean battery compartment each 50 hours or each 30 days. 15. Refer to manufacturer's manual.
16. Inspect masks, hose and fittings for condition, routing and support. 17. Refer to maintenance manual.
18. Lubrication of the actuator is required each 1000 hours or three years.
19. Each five years replace all rubber packings, back-ups and hydraulic hoses in both the retraction and brake systems. Overhaul all retraction and brake system components. 20. Replace check valves in turbocharger oil lines each 1000 hours.
21. Check alternator belt tension.
Figure 17-3. (2 Of 2) An excerpt of a typical manufacturer's inspection checklist utilized during annual inspections that outlines the required inspection items. This inspection checklist is multi-functional. It outlines 50-hour, 100-hour, 200-hour, and annual inspec-tion intervals.
inspection, it must be inspected by an A&P who holds an IA rating, or certified repair station inspec-tor and be signed off as an annual inspection only.
PROGRESSIVE INSPECTION
At times, aircraft operators may feel that it is not economical to keep the airplane out of commission long enough to perform a complete annual inspec-tion at one time. In which case, the owner may elect to use a progressive inspection schedule. A progres-sive inspection is exactly the same in scope and detail as the annual inspection but allows the work-load to be divided into smaller portions and per-formed in shorter time periods. For example, the engine may be inspected at one time, the airframe inspection may be conducted at another time, and components such as the landing gear at another. Progressive inspection schedules must ensure that the aircraft will be airworthy at all times and
con-form to all applicable FAA aircraft specifications, type certificate data sheets, airworthiness direc-tives, and other data such as the manufacturer's ser-vice bulletins and serser-vice letters.
The manufacturer provides guidelines to help an operator select an appropriate inspection program for their specific operation. For example, if an air-craft is flown more than 200 hours per calendar year, a progressive inspection program is most likely recommended to reduce aircraft downtime and overall maintenance costs.
Again referring to Figure 17-3, this aircraft inspection chart outlines a typical schedule used in a progressive inspection program. As shown in the chart, there are items inspected at 50,100, and 200 hours, in addition to special inspection items that require servicing or inspection at intervals other than 50, 100 or 200
17-8 Aircraft Airworthiness Inspection
hours. The inspection intervals are separated in such a way to result in a complete aircraft inspection every 200 flight hours. This particular inspection program would not be recommended or practical unless the aircraft is flown more than 200 hours per year.
Before a progressive inspection schedule may be implemented, the FAA must approve the inspection program. The owner must submit a written request outlining their intended progressive inspection guidelines to the local FAA Flight Standards District Office (FSDO) for approval. After approval, and before the progressive inspection program may begin, the aircraft must undergo a complete annual inspection. After the initial complete inspection, routine and detailed inspections must be conducted as prescribed in the progressive inspection sched-ule. Routine inspections consist of visual and oper-ational checks of the aircraft, engines, appliances, components and systems normally without disas-sembly. Detailed inspections consist of thorough checks of the aircraft, engines, appliances, compo-nents and systems including necessary disassembly. The overhaul of a component, engine, or system is considered a detailed inspection.
A progressive inspection program requires that a current and FAA-approved inspection procedure manual for the particular airplane be available to the pilot and maintenance technician. The manual explains the progressive inspection and outlines the required inspection intervals. All items in the inspection schedule must be completed within the 12 calendar months that are allowed for an annual inspection. The progressive inspection differs from the annual or 100-hour inspection in that a certified mechanic holding an inspection authorization, a certified repair station, or the aircraft manufacturer may supervise or conduct the inspection.
If the progressive inspection is discontinued, the owner or operator must immediately notify, in writ-ing, the local FAA Flight Standards District Office (FSDO) of the discontinuance. In addition, the first complete inspection is due within 12 calendar months or, in the case of commercial operations, 100 hours of operation from the last complete inspection that was performed under the progres-sive inspection schedule.
LARGE and TURBINE POWERED
MULTI-ENGINE AIRCRAFT
Large (over 12,500 lbs. gross takeoff weight) and multi-engine turbine aircraft operating under FAR Part 91, require inspection programs tailored to the specific aircraft and its unique operating condi-tions. These unique conditions would include
sce-narios such as high flying times, aircraft operated in extremely humid environments, or in extremely cold or wet climates. Because of the size and com-plexity of most turbine-powered aircraft, the FAA requires a more detailed and encompassing inspec-tion program to meet the needs of these aircraft and flying conditions. Although they may be operated under Part 91, large and turbine-powered aircraft are often inspected under programs normally uti-lized by air carrier or air taxi operations.
The registered owner or operator of a large or tur-bine-powered aircraft operating under Part 91 must select, identify in the aircraft maintenance records, and use one of the following inspection programs: a continuous airworthiness inspection program, an approved aircraft inspection program (AAIP), the manufacturer's current recommended inspection program, or any other inspection program developed by the owner/operator and approved by the FAA. The exception is in the case of turbine-powered rotorcraft operations, in which case, the owner/oper-ator may choose to use the inspection provisions set out for small aircraft: annual, 100-hour, or progres-sive inspection programs. After selection, the opera-tor must submit an inspection schedule, along with instructions and procedures regarding the perfor-mance of the inspections, including all tests and checks, to the local FAA FSDO for approval.
A continuous airworthiness inspection program is designed for commercial operators of large aircraft operating under FAR Part 121, 127, or 135. It is one element of an overall continuous airworthiness maintenance program (CAMP) currently utilized by an air carrier that is operating that particular make and model aircraft. [Figure 17-4]
Figure 17-4. Large turbine powered corporate jet owners may elect to use a continuous airworthiness inspection program because of the complexity of the aircraft and its systems.
A continuous airworthiness inspection program might be chosen under Part 91 operations when an air carrier purchases or leases an aircraft operating
under another air carrier's 121 certificate. For exam-ple, Airline B purchases an aircraft from Airline A. The aircraft must be operated under an inspection program during the transition from Airline A to Airline B. Instead of creating an entirely new inspection program tailored to the specific aircraft during this transition period, Airline B may choose to keep the aircraft on its current continuous air-worthiness inspection program until it is placed on the new owner's Part 121 operating certificate. An approved aircraft inspection program (AAJP) may be chosen by on-demand operators who operate under Part 135. If the FAA determines that annual, 100 hour, or progressive inspections are not adequate to meet Part 135 operations, they may require or allow the imple-mentation of an AAIP for any make and model aircraft the operator exclusively uses. The AAIP is similar to the CAMP utilized by most Part 121 air carriers. This pro-gram encompasses maintenance and inspection into an overall continuous maintenance program. [Figure 17-5]
Figure 17-5. Turbo-prop aircraft typical of the type operated by air-taxi operators. Each aircraft operated by air-taxi oper-ators may be maintained under an AAIP designed specifi-cally to that particular aircraft by registration number.
A complete manufacturer's recommended
inspec-tion program consists of the inspecinspec-tion program
supplied by the airframe manufacturer and supple-mented by the inspection programs provided by the manufacturers of the engines, propellers, appli-ances, survival equipment, and emergency equip-ment installed on the aircraft. A manufacturer's inspection program is used more frequently when an aircraft is factory new. If an aircraft has several modifications, updated systems, or custom avionics not installed at the factory, the manufacturer's inspection program alone may not be adequate in the overall inspection of the aircraft and all of its installed equipment and components. In this case, another method of inspection must be chosen. The owner of an aircraft may choose to develop their own inspection program. The recommended
manufacturer's inspection program is generally used as the basis of an owner developed inspection
plan. However, deviation from the manufacturer's
inspection program must be supported and approved by the FAA. The customized plan must include the inspection methods, techniques, prac-tices, and standards necessary for the proper com-pletion of the program. Most owner developed inspection programs include inspection and repair requirements only, and do not require continual maintenance performed to their aircraft.
CONFORMITY INSPECTIONS
Aircraft are manufactured to FAA approved specifi-cations. Alterations made to the original design specifications of the aircraft require approval in the form of a sign-off from a certificated maintenance technician or, in the case of a major repair or alter-ation, approval from the FAA on form 33 7. The absence of approval for any alteration renders the aircraft unairworthy. A conformity inspection is an essential element of all aircraft inspection programs and performed to determine whether the aircraft conforms to or matches its approved specifications. A conformity inspection is essentially a visual inspection that compares the approved aircraft specifications with the actual aircraft and associ-ated engine and components. A list is compiled out-lining the information gathered from the type cer-tificate data sheets (TCD), applicable supplemental type certificate data sheets (STC), major repair & alteration information (FAA Form 337), aircraft equipment list, airworthiness directive compliance record, etc. The list includes model numbers, part numbers, serial numbers, installation dates, over-haul times, and any other pertinent information obtained in the above reference documents. The mechanic performs a visual inspection and com-pares the aircraft with the compiled list of informa-tion making note of any deviainforma-tion from the aircraft specifications. [Figure 17-6]
A conformity inspection is not specifically required by name, but it is inherently required at every inspection interval due to the nature of the inspec-tion; to determine whether the aircraft conforms to its certification specifications. However, a confor-mity inspection is specifically required when an aircraft is exported to or imported from another country with the intention of becoming registered in that respective country. Further, a conformity inspection is highly recommended when perform-ing a pre-purchase inspection for a prospective air-craft buyer.
77-70 Aircraft Airworthiness Inspection
Figure 17-6. (1 of 2) Typical conformity inspection checklist. A mechanic visually inspects the aircraft then documents the actual aircraft and equipment information on a conformity checklist. The checklist is then compared to the aircraft's specifications to
ENGINE:
MAKE:
MODEL: S/N:
TBO hours/years: Maintenance Doc & Rev. no.
Engine TT: TSO Date of last Overhaul:
STC's installed:
Applicable airworthiness directives
PROPELLER:
MAKE:
MODEL: S/N:
TBO hours/years: Maintenance Doc & Rev. no.
Prop TT: TSO Date of last Overhaul:
STC's installed:
Applicable airworthiness directives
GOVERNOR:
MAKE:
MODEL: S/N:
TBO hours/years: Maintenance Doc & Rev. no.
Gov. TT: TSO Date of last Overhaul:
STC's installed:
Applicable airworthiness directives
MAGNETOS: LH MAKE:
MODEL: S/N:
RHMAKE: MODEL: S/N:
TBO hours/years: left right Maintenance Doc & Rev. no.
Mageto TSO left right Date of last Overhaul: left right
STC's installed:
Applicable airworthiness directives
Page 2 o f 2 Figure 17-6. (2 Of 2)
Although the conformity inspection is an important part of the overall inspection process, it is one of the most common inspections overlooked or not
entirely carried out. For example, an IA performing an annual inspection is responsible for determinig the airworthiness of the aircraft. Many times,
77-72 Aircraft Airworthiness Inspection
inspectors fail to visually verify the equipment installed on the aircraft with the equipment list. In doing so, the IA may overlook a piece of equipment installed on the aircraft but not documented in the maintenance records, which could render the air-craft unairworthy. The verification of the presence of equipment installed in the aircraft, but not veri-fying that the installation was properly performed may also render the aircraft technically unairwor-thy. The inspector must not only verify the physical presence of items but also confirm whether the installation of the equipment was properly per-formed, especially if the installation was done with-out proper documentation.
A skilled and effective inspector meticulously veri-fies the installation of equipment list items. Not only verifying that they are physically in the air-craft, but also that they were properly installed and, in the case of a major repair or alteration, that a form 337 was created and approved by the FAA.
AIR CARRIER & AIR CHARTER
OPERATIONS
Aircraft operators regulated under FAR Part 121 or 135 must maintain their aircraft under comprehen-sive maintenance and inspection programs. One of the differences between Part 91 operations and Air Carrier operations is that Part 121 operators must continually maintain and inspect their aircraft.
Ongoing maintenance is not required on aircraft operated under Part 91. The operating rules of Part 91 only require an owner to correct discrepancies found during inspection intervals. Air carriers, on the other hand, must perform aircraft maintenance and inspection on a continual basis.
Air charter operations regulated under Part 135 offer another unique operating environment. Depending on the type of operation, and the size and complexity of aircraft operated, a range of inspection rules apply. Part 135 operators may choose from several different inspection programs depending on the number of seats and complexity of the aircraft.
PART 121 AIR CARRIER INSPECTIONS
Air carriers operating under Part 121 must maintain their aircraft under a Continuous Airworthiness Maintenance Program (CAMP). A continuousair-worthiness inspection program is one element of an
overall CAMP. The basic requirements of a CAMP include inspection, scheduled and unscheduled maintenance, overhaul and repair, structural inspection, required inspection items (RII), and a reliability program. Specific instructions, standards, and operations specifications for each element of the continuous airworthiness maintenance program must be included in the air carrier's maintenance manual for the specific aircraft for which it is applicable. A CAMP is a fleet program and
encom-MAINTENANCE CHECK SCHEDULE
CHECK
SCOPE
INTERVAL
Service check Log book and maintenance forms review (for example: time control items). Exterior visual checks and routine aircraft servicing such as hydraulic fluids, engine oil, & general lubrication. Operational checks.
Required no more than 48 elapsed calendar hours from the last Service Check, A-1, A-2, A-3, A-4, or C check.
Check: A-1 check A-2 check A-3 check A-4 check
Log book and maintenance forms review. Exterior visual check, routine and specific inspections, and routine aircraft servicing. Replacing time-limited items. Operational checks.
Required no more than 125 flight hours from the last equalized A and/or C check.
C Check Includes "A: check items in addition to detailed inspections of aircraft, engines, components, and appliances.
Required no more than 3600 flight hours from the last C check.
Check: D-1 check D-2 check D-3 check D-4 check
Includes "C" check items in addition to extensive dissassemby and opening up of the aircraft, and weight & balance. Flight test after operational checks.
Required to be performed at no more than 9000 flight hours or 3 calendar years, whichever occurs first from the last phase D check.
Figure 17-7. Typical air carrier maintenance "letter check" schedule outlining the scope and time intervals of required inspections
for a specific type of aircraft. The maintenance schedule outline is used in conjunction with the specific work cards to maintain
passes the entire group of aircraft versus inspection programs regarding individual aircraft such as an AAIP, which is utilized under Part 135 air charter operations.
Like a progressive inspection program, the FAA must approve a continuous inspection program. This inspection program is extremely comprehen-sive, specific to the operator's aircraft, and requires complex maintenance facilities and large numbers of technical personnel. A continuous airworthi-ness inspection program is a program of FAA-approved inspection schedules which allow aircraft to he continually maintained in a condition of airworthiness without being taken out of service for long periods of time. This program keeps aircraft downtime to a minimum due to segmented maintenance or inspections intervals, thereby keeping the aircraft in service in a more efficient and convenient manner.
The continuous inspection program for a large air carrier may, as an example, consist of "letter check" inspection schedules. An example of a typical letter check inspection schedule is outlined in Figure 17-7. Letter checks are normally scheduled prior to due times or cycles. Over-flying due times or cycles of any required inspection is a direct violation of FAA regulations and may include large monetary fines. [Figure 17-7].
It is difficult to provide an overall description of a general air carrier inspection program because each air carrier's CAMP is designed specifically to its air-craft and type of operating conditions. Hence, every air carrier operating in the U.S. utilizes a different CAMP designed specifically for its individual needs and specific flight operations.
There are many different methods of inspection scheduling, inspection frequency, and terminology used throughout the airline industry. For example, one airline may refer to cursory line maintenance as a "daily" check, while another may refer to the same type of line check as a "service" check. The scope of these types of inspections is also designed explicitly for the particular aircraft. What is included in a daily check for one specific type of aircraft may not be comprehensive enough for another. Again, figure 17-7 illustrates a letter check schedule including phase inspections within the "A" and "D" checks regarding a specific type of aircraft.
In this schedule arrangement, service checks are
based on calendar hours while all other letter checks are based on flight hours. The completion of an "A" check eliminates the need for a service check due at the identical time interval. In other words, if a more detailed inspection is performed, it may zero out the less-encompassing inspection due time. A service check is due 48 calendar hours from the completion period of a "service", "A", "C", or "D" check. The next "A" check phase is due 125 flight hours from a completed "A", "C", or "D" check. This inspection schedule shows a series of "A" checks between each "C" check. There are twelve sets of "A" checks (A-l, A-2, A-3, A-4) between each complete heavy "C" check. "C" checks are due every 3600 flight hours and two comprehensive "C" checks are due between every heavy "D" check.
Each level of inspection must be clearly defined in the operator's continuous airworthiness inspection program. For example, a specific area of the aircraft may require only a visual inspection during pre-flight, "service checks", and "A" checks but may require a detailed inspection in the same area for a heavy "C" or "D" check. In most letter check maintenance schedules, the inspection and maintenance become more detailed and build upon the prior letter check performed.
Work cards act as control documents in the
contin-uous inspection process. Job cards are issued for all aspects of CAMP inspections and are used to orga-nize inspection instructions and account for the specific steps involved. Depending on the scope of inspection, several work or job cards are refer-enced. Each work card outlines one specific area of the inspection. Figure 17-8 is an example of a work card used during a heavy "C" check regarding an air carrier aircraft. The work card provides an out-line of a specific area of the aircraft inspection. Recurring airworthiness directives and manufac-turer's service bulletins are usually incorporated on work cards also. The work card provides account-ability columns where the inspector or mainte-nance technician signs off each step as it is inspected or serviced. In addition, specific instruc-tions, including reference figures, may be included with each work card. The completed work card becomes part of the aircraft's maintenance record. [Figure 17-8]
FAR Part 121 outlines the specific approval for return-to-service requirements for air carrier operations.
77-74 Aircraft Airworthiness Inspection
FLY HIGH AIRLINES
B737-200 C-Check
INSPECT LEFT ELEVATOR/TAB STRUCTURE AND HINGE FITTINGS CARD NUMBER 6-4008
A/C NUMBER STATION DATE
INSPECT LEFT ELEVATOR/TAB STRUCTURE AND HINGE FITTINGS
M 1. INSPECT LEFT ELEVATOR UPPER AND LOWER SKIN (service bulletin AOT-53-02)
M 2. INSPECT LEFT ELEVATOR INTERNAL STRUCTURE 3. INSPECT THE FOLLOWING L/H ELEVATOR TAB HINGES 1 a. Inspect L/H elevator tab hinge no. 1
1 b. Inspect L/H elevator tab hinge no. 2
4. INSPECT THE FOLLOWING L/H ELEVATOR AND HORIZONTAL STABILZER HINGE FITTINGS AND BEARINGS
1 a. Inspect L/H elevator No. 1 hinge bearing and bolt (AD 97-08-22) I b. Inspect L/H elevator No. 2 hinge bearing and bolt (AD 97-08-22)
5. INSPECT THE FOLLOWING L/H ELEVATOR AND HORIZONTAL STABILZER HINGE FITTINS, BEARINGS AND PLATE ASSEMBLIES
1 a. Inspect No. 3 hinge bearing plate assembly ! b. Inspect No. 4 hinge bearing plate assembly
INSPECT LEFT ELEVATOR/TAB STRUCTURE AND HINGE FITTINGS
APPLICABLE FIGURES: FIG.1
1. INSPECT LEFT ELEVATOR UPPER AND LOWER SKIN FOR
DELAMINATION, CRACKS AND SIGNS OF BONDED SKIN SEPARATION. 2. INSPECT LEFT ELEVATOR INTERNAL STRUCTURE FOR CONDITION
INCLUDING:
a. Check internal spars, webs, ribs and stiffeners.
b. Check condition of structure at front spar hinge attachment to elevator. c. Check tab lock mechanism for condition.
3. INSPECT THE FOLLOWING L/H ELEVATOR TAB HINGES FOR GENERAL CONDITION AND OBVIOUS DAMAGE.
a. Inspect L/H elevator tab hinge No. 1. b. Inspect L/H elevator tab hinge No. 2.
4. INSPECT THE FOLLOWING L/H ELEVATOR AND HORIZONTAL STABILZER HINGE FITTINGS AND BEARINGS FOR GENERAL CONDITION AND
OBVIOUS DAMAGE. (Refer to figure 1)
a. Inspect L/H elevator No. 1 hinge bearing and bolt. b. Inspect L/H elevator No. 2 hinge bearing and bolt.
5. INSPECT THE FOLLOWING L/H ELEVATOR AND HORIZONTAL STABILER HINGE FITTINGS, BEARINGS AND PLATE ASSEMBLIES FOR GENERAL CONDITION AND OBVIOUS DAMAGE.
a. Inspect No. 3 hinge bearing plate assembly. b. Inspect No. 4 hinge bearing plate assembly.
Figure 17-8. (1 of 2) Work/job card which references the "Left elevator/tab structure and hinge fitting" inspection required at a
heavy "C" check. The work card includes the specific inspection steps along with supporting documentation helpful in the
77-76 Aircraft Airworthiness Inspection
PART 135 AIR CHARTER
INSPECTIONS
Part 135 on-demand air charter operators have sev-eral different options regarding the type of inspec-tion programs with which they must comply. Air charter companies that operate aircraft with less than 9 seats may choose to inspect these aircraft under FAR Part 91 and Part 43 rules, 100-hour or progressive inspection programs. In other words, they are not required to perform continual mainte-nance on their aircraft, only inspection and dis-crepancy repair. Air charter operators that operate aircraft with 10 or more seats are required to imple-ment a more-encompassing continual maintenance and inspection program. They may choose to implement a Continuous Airworthiness Maintenance Program [CAMP), an Approved Aircraft Inspection Program (AAIP), a current man-ufacturer's inspection program, or an operator developed inspection and maintenance program approved hy the FAA.
An approved aircraft inspection program (AAIP) is the inspection program most often implemented by FAR Part 135 operators. It is similar to a continuous airworthiness maintenance program used by Part 121 air carriers. However, AAIPs are not fleet inspection programs and do not require continual maintenance. They require continual inspection and are set up for the individual aircraft by registra-tion number and serial number. Air charter opera-tions may have several different AAIPs for different aircraft operated.
For example, an air charter operation that operates an aircraft with 9 or fewer seats may inspect that particular aircraft under 100-hour or progressive inspection intervals. The same operation may also operate several larger, complex aircraft and inspect them under separate AAIPs. It is possible for an air charter operator to use a different inspection pro-gram for each of its aircraft, progressive for one, AAIP for another, etc. [Figure 17-9]
Manufacturers' inspection programs are more spe-cific than the 100-hour or annual inspections but lack the ease and control provided by the approved aircraft inspection program. An AAIP allows the operator to choose their own maintenance and inspection schedules. An AAIP is not considered better than a manufacturer's program, however, an AAIP provides the FAA inspector with more control of the program's content. It requires the operator to validate its programs and revisions to the inspector which manufacturer's programs do not require. This
Figure 17-9. Air medical operators may operate several dif-ferent types of airplanes and helicopters and inspect each under separate inspection programs. AAIPs are not fleet programs; they are inspection programs designed for indi-vidual aircraft. A charter company that owns and operates five different aircraft could conceivably operate them under five different AAIPs; each specific to an individual aircraft.
is not to say that a manufacturer's program cannot be used, but it must be identified as an AAIP and approved for a particular operator as that operator's program, not the manufacturer's.
When establishing an approved aircraft inspection program (AAIP), it should include avionics, instru-ment systems, and appliances. These types of sys-tems are not always installed by the aircraft manu-facturer and may not be included in their recom-mended inspection program. The AAIP must include instructions and procedures for all installed systems. Approved aircraft inspection programs are similar to continuous airworthiness inspection programs in that they both differ tremendously from operator to operator and aircraft to aircraft. An example of an AAIP might contain a daily service check, a 50-hour Preventative Maintenance Inspection (PMI), a series of 5 separate phase inspections conducted 150 hours apart, a 2500-hour major airframe inspection, and additional maintenance items that include stand-alone inspections. [Figure 17-10] [Figure 17-11]
SPECIAL INSPECTIONS
Special inspections are scheduled inspections with prescribed intervals other than the normally estab-lished inspection intervals set out by the manufac-turer. Special inspections may be scheduled by flight hours, calendar time, or aircraft cycles. For instance, in the case of a progressive inspection schedule for a small Cessna, special inspections occur at intervals other than 50, 100, or 200 hours.
INSPECTION SCHEDULE OUTLINE A/C time flight hrs 1 PHASE 2 3 4 Type of Inspection
200 X Nose landing gear area, nose gear, pilot's compartment, cabin
section, rear fuselage & empennage, wings, main gear area, engines, landing gear retraction, operational inspection, post inspection.
400 X Nose section, nose avionics compartment, nose landing gear area,
nose gear, pilot's compartment, cabin section, rear fuselage & empennage, wings, main landing gear area, engines, landing gear retraction, operational inspection, post inspection.
600 X Nose landing gear area, nose gear, pilot's compartment, cabin
section, rear fuselage & empennage, wings, main gear area, engines, landing gear retraction, operational inspection, post inspection
800 X Nose section, nose avionics compartment, nose landing gear area,
nose gear, pilot's compartment, cabin section, rear fuselage & empennage, wings, main landing gear area, engines, landing gear retraction, operational inspection, post inspection.
After "phase 4" inspection is completed, repeat inspection sequence. The complete program must be accomplished at least one time every 24 calender months. Any part of the inspection not completed is due immediately. Completion of phases 1-4 is considered a "complete inspection."
Figure 17-10. An example of a typical AAIP phase inspection schedule outline.
Special inspection items are usually explained in the notes section of the service manual inspection chapter.
Examples of special inspection items may include oil change information after an engine overhaul, the inspection and replacement of hoses at engine over-haul, and magnetic compass compensation every 1000 hours. Additionally, inspection and replace-ment of the rubber packings on each brake at 5-year intervals, and inspection and lubrication of the ele-vator trim tab actuator at 500-hour intervals may also constitute special inspection items. Each man-ufacturer outlines special inspection items specific to each model of aircraft.
Altimeter and static system inspections and certifi-cations are considered special inspections. Every
aircraft operated under Instrument Flight Rules must have its altimeters and static systems inspected and certified for integrity and accuracy every 24 calendar months as required by FAR Part 91.411. The scope of the altimeter and static system certification is outlined in FAR Part 43, Appendix E. The altimeter is checked for operation and accu-racy up to the highest altitude it is used, usually the aircraft's service ceiling, and a record made of this
inspection and certification in the aircraft mainte-nance records.
The altimeter certification may be conducted by the manufacturer of the aircraft, or by a certificated repair station (CRS) holding an appropriate rating that authorizes this particular inspection. However, a certified airframe technician may perform the sta-tic pressure system leakage tests and integrity inspection but cannot perform the certification.
ATC transponder inspections are also considered
special inspections. The radar beacon transponder that is required for aircraft operating in most areas of controlled airspace must be inspected each 24 calendar months by any of the following: a certifi-cated repair station approved for this inspection, a holder of a continuous-airworthiness maintenance program, or the manufacturer of the aircraft on which the transponder is installed. This test is required by FAR Part 91.413 and described in FAR Part 43, Appendix F.
The emergency locator transmitter (ELT) inspection is also considered a special inspection. FAR Part 91.207 requires the ELT inspection every 12 months. The inspection entails checking for proper
17-18 Aircraft Airworthiness Inspection
A. NOSE SECTION ATA ref.Mec
h
Insp
1. Combustion heater
a. Check the gap and condition of the heater spark plug 21-40-00
b. Check fuel plumbing, pump and regulator for leakage, damage, and security of attachment 21-40-00
c. Clean and inspect the system fuel filter at the inlet port of the fuel control valve 21-40-00 B. NOSE AVIONICS COMPARTMENT
NOTE: There are no inspections required in this section during this phase
C. NOSE LANDING GEAR AREA
1. Electrical wiring and equipment- inspect all exposed wiring & equip for chafing & damage AC 43.13 D. NOSE GEAR
1. Wheel
a. Inspect wheel for wear, damage, and corrosion 32-40-00
b. Inspect wheel bearings and races for wear, pitting, cracks, discoloration, rust, or damage 32-40-00
2. Tire
a. Inspect for wear and deterioration 12-20-00
b. Check for correct inflation 12-20-00
3. Shimmy damper - Inspect for leaks, security, and attachment
4. Nose gear brace stop lugs - Inspect for cracks, damage or deterioration 5. Nose gear steering stop - Inspect steering stop for damage or distortion
6. Landing & taxi lights - Inspect for broken lens or bulbs 33-40-00
7. Steering linkage- Inspect nose gear steering mechanism & attaching hardware for wear 32-50-00
8. Nose landinq gear strut - Check strut for leakage and correct extension 32-20-00
Phase 1 Inspection (page 1 of 5)
installation, battery corrosion, operation of the con-trols and crash sensor, and the ELT signal. Check the ELT battery's expiration date and record the expira-tion date for replacing or recharging the battery in the maintenance record. The expiration date must also be legibly marked on the outside of the ELT.
CONDITIONAL INSPECTIONS
A conditional inspection is an unscheduled inspec-tion conducted as a result of a specific over-limit, or abnormal event. Examples of events requiring spe-cial inspections include:
• Hard landings • Overstress conditions
Flight into severe turbulence Flight into volcanic ash Overtemp conditions Overweight landings
Exceeding placarded speed of flaps and landing gear
Bird strike Lightning strike
INSPECTION GUIDELINES AND PROCEDURES
The inspection of an aircraft to determine its airwor-thiness requires a great amount of skill and judgment. For the most part, the items to he inspected are listed in an inspection checklist. However, how well an inspector evaluates an item's airworthiness is up to the judgement and skill of the individual. These factors combine to require the inspector to develop a system or procedure for effectively inspecting an aircraft. It is imperative that inspectors set up a set of stan-dards in order to determine an item's airworthiness. These standards must be high enough to guarantee the airworthiness of the aircraft, but not so high to cause needless expense to the owner. The inspector must also withstand pressures applied by others to lower those standards by representing items as being airworthy when they are not. Once these stan-dards are compromised, it is very difficult to restore the integrity of an aircraft inspector.
INSPECTION FUNDAMENTALS
Aircraft inspectors should be familiar with the vis-ible, measurable or otherwise detectable effects of wear and tear on an aircraft. An effective inspector is able to recognize and determine the cause of the wear and tear that is found during inspection, which makes the subsequent repair straightfor-ward. The five most common sources of wear and tear are weather, friction, stress overloads, heat, and vibration.
The damaging effects of weather can vary widely and range from surface corrosion, oxidation, wood rot, wood decay, fabric decay, fabric brittleness, fab-ric mildew and cracks, and interior damage and exterior paint oxidation due to ultra-violet rays. In addition, physical damage due to weather can range from lightning damage, hail dents, wind damage to control stops and control rigging, to surface damage due to sand and dirt erosion. Atmospheric moisture content is another consideration when inspecting an aircraft. The amount of water and salt the air holds may directly influence the potential corrosion found on the aircraft, especially aircraft based near large bodies of water and oceans. For further
infor-mation regarding the identification and treatment of corrosion, see chapter 12 of the ASrP Technician General Textbook.
Friction damage manifests in many different forms such as abrasions, burnishing, chafing, cuts, dents, elongation, erosion, galling, gouging, scratches, scoring, and tearing. In the context of this section, friction is the rubbing of one object against another that causes a destructive result. [Figure 17-12]
• Abrasion is caused by a rough substance
between two moving surfaces.
• Burnishing is the polishing of a surface by the sliding contact with another, smoother, harder, metallic surface. Bearings have a tendency to burnish and should he checked and lubricated regularly.
• Chafing is the wear between two parts rub bing, sliding, or bumping into each other that are not normally in contact.
• Elongation is the oval-shaped wear of a bear ing surface around bolts, hinge pins, clevis pins, etc.
• Erosion is the loss of metal from the surface by the mechanical action of materials such as dirt, sand, or water. Propellers, leading edges of the wings and empennage, wheel fairing, landing gear, and cowlings are susceptible to erosion damage.
• Galling is the breakdown or buildup of the metal surface due to excessive friction
between two parts in motion. Particles of the softer metal are torn loose and welded to the harder metal surface.
Overloading the aircraft may result in the failure or deformation of the structure, either slightly or prominently, but usually produces visible damage. The types of stress overloads that an inspector must
This nose strut shows signs of abrasion due to a lack of lubrication on the strut surface. The protective plating has also been rubbed away at the base exposing the metal underneath. The unprotected portion of the strut also shows signs of oxidation corrosion. Cleaning and lubricating the strut surface extends the life and appear-ance of the strut
This example illustrates chafing caused by the control cables rubbing the ducting found under the floor panels of
a Beech King Air.
Wheel bearings have a tendency to burnish with a lack of lubri-cation. The bearing race in this example shows signs of bur-nishing. Detailed inspection and lubrication of the bearing assembly will extend the life of the bearings.
Elongation is a defect that needs to be checked at attach points on the aircraft. The attachment plate of this hydraulic actuator shows signs of elongation of both bolt holes. The continuation of the elongation will eventually fatigue the metal to the point of fail-ure if not detected.
Figure 17-12. Examples of friction damage.
become familiar with are tension, compression, tor-sion, shear, and bending overloads. [Figure 17-13]
Tension overloads usually occur after hard landings, taxiing on rough fields, or flight in turbulent air. Failure is indicated by signs of the pulling away of fittings from the fuselage, failure of welded areas, wrinkling of metal skin, and deformed or cracked fittings.
Compression overloads may manifest as
bulges in the metal skin, breaks in paint, and bows or bends in the long members such as wing struts. Wood compression may be detected by a slight ridge across the face of the member at right angles to the grain.
Torsion or twisting overloads will turn one
end of a part around its longitudinal axis
J I I -
This propeller shows signs of erosion on the leading edge due to sand, dirt, and foreign objects wearing away the surface metal
77-22 Aircraft Airworthiness Inspection
Tension or stretching damage may be exhibited by the pulling away of the skin from the structure of an aircraft. In this example, the lower wing skin of a damaged Beech Bonanza has been pulled away from the riveted seam exposing the interior wing
Figure 17-13. Examples of stress-overload damage.
while the other end is held fixed or turned in the opposite direction. Wheels caught in frozen ruts during landing may twist the land-ing gear and cause torsion damage. Careful inspection of the landing-gear torque links should be made after landing on rough or rut-ted fields. Severe air loads imposed upon the aircraft during flight through turbulent air may twist the control surfaces. Improper rigging of the wing and tail control surfaces may also cause torsion overloads by producing a posi-tive load on one side of the surface at all times.
Shear overloads result from forces that are
applied to an object in an opposite but parallel direction. When a shear overload is applied, the part having the least resistance to the force will fail first. Because bolts, rivets, and clevis pins are used in areas subject to shear forces, they should be inspected for shear failure. Bent, torn, or deformed bolts, rivets, or clevis pins are good indications of shear damage.
Bending overloads cause rigid members to curve or bow away from a straight line. Hard landings, abnormal flight loads, and improper ground handling may cause bending damage. Wood or metal skin may show signs of wrin-kling, cracking, or distortion. On fabric cov-ered airplanes, a bent member may be detected by looseness or wrinkling of the fabric.
The primary source of heat damage affecting the air-craft is the powerplant. Inspectors must be familiar with direct and indirect heat sources that cause damage. Direct heat damage is normally caused by leaking exhaust gases, and, in the case of severe leaks, may allow flames to escape resulting in dev-astating consequences. Indirect heat damage may result from excessive engine compartment heat indicated by high oil and cylinder head tempera-tures, blistering paint on the engine cowling, and odors of burned oil or rubber during or after engine run-up.
The wing tip of this aircraft is bent in an upward direction illustrating bending stress overload. The inboard portion of the wing was held in place while a bending force was applied to the wing tip.
The firewall of this small aircraft was compressed in a hard landing. The firewall is constructed of stainless steel requiring a large amount of compression stress overload
Improperly installed or leaking engine baffles, mis-aligned cowlings, improper carburetor-heat control rigging, improper cowl-flap door rigging, and dirty air coolers may cause indirect heat damage. In addi-tion, the use of an improper grade of oil, and oil leakage, may also cause indirect heat damage to the aircraft and engine. [Figure 17-14]
Figure 17-14. The bubbling of the paint in addition to the exhaust trail exiting the engine cowling vent illustrates
indirect heat damage.
Vibration causes many malfunctions and defects
throughout the life of the aircraft. Vibration affects loose or improperly installed parts and accelerates wear to the point of failure in some cases.
Low frequency vibration can be felt or noticed by the pilot or mechanic. It is usually caused by a malfunctioning powerplant, propeller, worn engine-mount pads, loose aircraft structure joints, or improper rigging. Noticeable vibration causes abnormal wear between moving parts. Excessive clearances and poor installation are also factors affecting the level of vibration damage and should be considered when inspecting the aircraft.
For example, control surface and trim tab "free-play" limits may be extreme due to excessively worn hinges and actuator damage. Excessive free-play causes the control surface to vibrate or "flutter" in flight. The vibration then transfers through the airframe structure and causes fractures and fatigue to appear in locations remote from the source. [Figure 17-15]
INSPECTION GUIDELINES
In addition to the aforementioned wear and tear effects, following is a brief outline of some of the most common deficiencies to look for in an aircraft
Figure 17-15. The cracks on the wing skin of this Piper Seneca were caused by the excessive play in the aileron
hinge. During flight, vibration or "flutter" of the ailerons
occurred which stressed the aircraft structure and caused
stress cracks to manifest on the upper wing surface.
inspection. An inspector must be familiar with each of these areas in order to perform effective and high-quality inspections.
• Movable Parts: proper lubrication, security of attachment, binding, excessive wear, proper safety wiring, proper operation and adjust ment, proper installation, correct travel,
cracked fittings, security of hinges, defective bearings, cleanliness, corrosion, deformation, and sealing and tension.
• Fluid lines and hoses: proper hose or rigid tubing material, proper fittings, correct fitting torque, leaks, tears, cracks, dents, kinks, chaf ing, proper bend radius, security, corrosion, deterioration, obstructions and foreign matter, and proper installation.
• Wiring: proper type and gauge, security, chaf ing, burning, defective insulation, loose or broken terminals, heat deterioration, corroded terminals, and proper installation.
• Bolts: Correct torque, elongation of bearing surfaces, deformation, shear damage, ten
sion damage, proper installation, proper
size and type, and corrosion.
• Filters, screens, and fluids: cleanliness, cont amination, replacement times, proper types, and proper installation.
• Powerplant Run-up: Engine temperatures and pressures, static RPM, magneto drop, engine response to changes of power, unusual engine noises, ignition switch operation, fuel shut- off/selector valves, idling speed and mixture settings, suction gauge, fuel flow indicator
operation, engine mount security, mount bolt torque, spark plug security, ignition harness
77-24 Aircraft Airworthiness Inspection
security, oil leaks, exhaust leaks, muffler cracks and wear, security of all engine acces-sories, engine case cracks, oil breather obstruc-tions, firewall condition, and proper operation of mechanical controls.
Propellers: nicks, dents, cracks, cleanliness, lubrication, gouges, proper blade angles, blade tracking, proper dimensions, governor leaks and operation, and control linkages for proper tension and installation. Nicks on the leading edge of the blade are an important item to inspect for; they produce stress con-centrations that need to be removed immedi-ately upon discovery in order to prevent the blade from separating at the nick.
INSPECTION PROCEDURES
The inspection of aircraft requires a great deal of organization and planning. Effective inspections must be performed in a logical and orderly sequence to ensure that no inspection item is over-looked or forgotten. The accepted method of per-forming an inspection that is used by the aircraft maintenance industry also includes the service and repair activities that are necessary to approve the aircraft for return to service.
The inspection of an aircraft is divided into five basic phases: pre-inspection, examination, service and repair, functional check, and the return to ser-vice phase.
PRE-INSPECTION PHASE
The pre-inspection phase is very important and serves to organize the paperwork, records, tools, and equipment needed for the inspection. This phase usually includes: work order completion, compilation of the aircraft specifications, review of maintenance records, airworthiness directive research, manufacturer service bulletin and letter research, airworthiness alert research, producing the inspection checklist, and aircraft preparation. The pre-inspection phase begins with the comple-tion of the work order which outlines and autho-rizes the performance of the services. The mainte-nance records, airworthiness directives, service bul-letins, and any other relevant service information are researched and, if applicable, added to the inspection checklist. The aircraft is cleaned, and the engine is usually run-up to check engine para-meters and to set a base line for the post-inspection run-up. Removal of inspection panels, engine cowl-ing, and interior, if required, are done during the pre-inspection phase. In addition, tools and equip-ment are made ready, and any known parts that are needed are ordered. [Figure 17-16]
WORK ORDER
The work order is the agreement between the shop or mechanic and the owner of the aircraft concern-ing the work to be performed. It describes the work
Figure 17-16. During the pre-inspection phase, the aircraft is prepared for the inspection by removing all applicable inspection pan-els and completely uncowling the engine compartment. It is important to have access to as much of the aircraft, systems, and
requested and serves as a record of parts, supplies, and labor expended on the aircraft. While inter-viewing the owner, describe the work requested and any discrepancies that the owner wants repaired. The owner then signs the work order before work begins on the aircraft. [Figure 17-17]
Figure 17-17. Preparing the work-order with the customer is an important step in the pre-inspection phase of any inspection.
Clearly explain to the customer that additional charges may apply regarding maintenance per-formed to correct any discrepancy found during the inspection. It should be noted that the work order normally only estimates the total cost of the inspec-tion and any subsequent maintenance repair. It is impossible to determine the labor and parts expense of unknown discrepancies. Certain shops charge a flat rate for the inspection and charge separately for parts and labor regarding any maintenance done to the aircraft. Others may charge on an hourly basis along with any expenses for parts and supplies that are incidental to the inspection and maintenance. At times, discrepancies are detected upon inspec-tion. It is wise to provide the owner the opportunity to choose to fix the discrepancies or not. If the owner chooses to repair any discrepancy that is found dur-ing the inspection, revise the work order ■with reference to the needed repairs. Have the owner sign the revision order before beginning the repairs.
MAINTENANCE RECORDS AND AIRCRAFT SPECIFICATION REVIEW
The maintenance record and aircraft specifications review is a very important part of any inspection and takes place before the aircraft is physically examined. Maintenance records can reveal quite a bit about the care and maintenance of an aircraft. The maintenance history of the aircraft is carefully examined to determine repetitive maintenance problems, airworthiness directive compliance, any major repairs and alterations done to the aircraft,
and, on a base level, whether the aircraft has had maintenance performed in a consistent manner. Maintenance records are researched to determine information such as the type of oil in use, ELT bat-tery expiration and operational test date, altimeter and transponder test due dates, when the spark plugs were last changed, age of the battery, when vacuum system filters were last changed, life-lim-ited parts status, aircraft total time, major repair and alteration information, and engine time since overhaul (TSO). [Figure 17-18]
Figure 17-18. Thorough maintenance information research is key to an effective inspection. Without complete and correct aircraft information, important items may be over-looked during an inspection.
All aircraft must conform to their certification requirements. Therefore, the research and compi-lation of the aircraft specifications is essential to a proper conformity inspection. A conformity inspection entails a visual inspection of the entire aircraft, engine, propeller, avionics, and appli-ances using information gathered from the TCD, STCs, aircraft equipment list, and applicable air-worthiness directives. A thorough inspection starts with the research of the aircraft specifica-tions and maintenance information.
In addition to the records review, the inspection checklist must be obtained that is specific to the aircraft make and model. When performing annual or 100-hour inspections, the use of a checklist is required by FARs. The technician may design a checklist that is specific to the aircraft being inspected, or use a checklist provided by the man-ufacturer of the aircraft, engine, propeller, and installed components as long as it meets the mini-mum requirements outlined in 14 CFR part 43 Appendix D.