14-8 Figure 14-2. Typical Main Landing Gear Spring Strut and Axle Assembly
14.7.2.2 Corrosion, fatigue, or hardware substitution, or all, can be detrimental to other areas of the strut as well, and the manufacturer’s recommendations should be thoroughly reviewed and understood. Compatibility of materials should be considered, particularly when aircraft have been modified with components of different base metals than originally certified, such as titanium/cadmium combinations or other non-compatible materials. The effects of time in service on hardware should be considered and replacement intervals established.
14.7.2.3 Aircraft in service with these modifications should have an increased inspection frequency with records maintained to indicate the method and status since last inspection.
14.7.2.4 Under current guidance, ICA are required to be addressed prior to returning the aircraft to service. Apply careful consideration when developing field approval data packages that define the methods, techniques, and practices used in determining the continuous airworthiness of the aircraft. AC 43-210, Figure 5-1, Major Repair or Major Alteration Maintenance Information Checklist, contains the minimum requirements that should be addressed. The ICA should be referenced in block 8 of FAA Form 337.
14.7.2.5 In establishing the frequency of these repetitive inspections, special consideration should be given to the number of hours flown, type of flying, operational environment, age, and previous operating history of the aircraft.
14.7.2.6 Operators of aircraft having obtained approval for these installations, prior to the data package requirement for field approval, may wish to develop ICA for their aircraft.
14-9
14.8 Interchanging of Skis and Wheels.
14.8.1 W&B Computation. A person appropriately authorized by 14 CFR § 43.3 must perform a new W&B computation when the larger tires are initially installed. The FAA recommends that the airplane be weighed for this initial computation. After the initial installation, removing the larger tires and/or brakes and returning the aircraft to its original configuration or vice versa is considered a preventive maintenance operation if it does not involve complex assembly operations or a new W&B computation. Refer to 14 CFR part 43 appendix A, paragraph (c)(18).
Note: During subsequent W&B changes to the airplane, be sure to update the W&B records and equipment list to ensure proper configuration of all approved ski, wheel, and float installations.
14.8.2 Periodic Inspection Required. Seasonally removed and installed equipment items such as tires, skis and floats should be inspected at installation to comply with 14 CFR §§ 91.407(a) and 91.409(a), and 14 CFR part 43 appendix D, if they were not installed on the airplane at the time of the last inspection. All available data described in this paragraph should be used during the inspection.
14.9 Documentation.
14.9.1 Alterations. Modifications not listed in the aircraft specifications, incorporating larger tires, wheels, or brakes are considered a major alteration. Therefore, it is recommended that the procedures contained in ACs 43.9-1 and 43-210 be utilized to meet the recording requirements contained in 14 CFR part 43.
14.9.2 Performance Information. The following paragraphs contain the minimum additional performance data required for airplanes equipped with larger tire installations. Refer to AC 43-210, Paragraph 4, Flight Manual Supplements, for additional guidance regarding approved AFMS.
Note: In estimating landing distances for other conditions, caution should be exercised as temperatures or other environmental conditions may either decrease or increase these distances.
14.10 Summary of Considerations for Approval of Larger Tire Installation (may be used as a job aid).
14.10.1 If an STC exists, it must be used.
14.10.2 All tires must be either TSO or PMA approved.
14.10.3 Tire size must not exceed 35 x 15 inches.
14-10
14.10.4 Procedures:
1. Review ACs 23-17 and 43-210.
2. Review the aircraft records for previous alterations and repairs to ensure there is no effect on the proposed alteration.
3. Conduct a conformity evaluation to ensure that the proposed alteration will not impact the airworthiness of the aircraft.
4. Submit FAA Form 337 prepared in accordance with 14 CFR part 43 and ACs 43-210 and 43.9-1, including the certification basis used for the field approval, a description of the proposed alteration, and ICA.
5. The alteration must be performed by a certificated airframe mechanic, and accomplished using acceptable methods, techniques, and practices. Refer to 14 CFR §§ 43.7 and 43.13.
6. Aircraft must be weighed with tires installed, and a new W&B generated. Refer to 14 CFR §§ 43.13, 91.9, and 91.103.
7. Aircraft CG must be determined for the most forward and aft conditions, at both empty and gross weights. Refer to AC 43.13-1, Chapter 10, Weight and Balance.
8. The holder of an Inspection Authorization (IA) should inspect the aircraft for:
• Previous alterations or repairs that may not have been recorded.
• Compatibility of previous alterations or repairs.
• Airworthiness of the aircraft.
14.10.4.1 Ensure that the aircraft wing, tail, and control surfaces have not been improperly altered and the aircraft is properly rigged (log book entry by a certified mechanic).
14.10.4.2 Perform a series of maintenance operational check flights as follows:
• No passengers permitted.
• All flights conducted in accordance with the aircraft’s flight manual or limitations.
• Turning and braking tests for tire slippage and interference. Recommend conducting at minimum and maximum tire pressures.
• Aircraft minimum weight: Flight(s) conducted at the most forward and at the most aft CG.
• Aircraft at gross weight: Flight(s) conducted at the most forward and at the most aft CG.
14.10.4.3 After completion of check flights, the pilot will sign the aircraft’s airframe maintenance log book, certifying that the aircraft is safe to operate within the operational limits of the aircraft’s design. Refer to 14 CFR § 91.407(b).
OMB Control Number: 2120-0746 Expiration Date:12/31/2027 Advisory Circular Feedback Form Paperwork Reduction Act Burden Statement: A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0746. Public reporting for this collection of information is estimated to be approximately 20 minutes per response, including the time for reviewing instructions, searching existing data sources, gathering, and maintaining the data needed, completing, and reviewing the collection of information.
All responses to this collection of information are voluntary. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to:
Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-1524.
If you find an error in this Advisory Circular, have recommendations for improving it, or have suggestions f or new items/subjects to be added, you may let us know by emailing this form to the Flight Standards Directives Management Officer at 9-AWA-AFB-120-Directives@faa.gov.
Subject:
AC 43.13-2C, Acceptable Methods, Techniques, and Practices – Aircraft Alterations Date: _____________________ Please mark all appropriate line items:
☐ An error (procedural or typographical) has been noted in paragraph ____________ on page _______.
☐ Recommend paragraph _____________ on page __________ be changed as follows:
☐ In a future change to this AC, please cover the following subject:
(Briefly describe what you want added.)
☐ Other comments:
☐ I would like to discuss the above. Please contact me using the information below.
Submitted by: Date: ______________________ FAA 1320-73 (01/25) SUPERSEDES PREVIOUS EDITIONS