MIL-HDBK-1530B(USAF)
APPENDIX A
APPENDIX A
ADDITIONAL GUIDANCE FOR NEW, OFF-THE- SHELF AIR VEHICLES
A.1 Structural qualification. The following general guidance should be used to tailor the guidance contained in the main body of this document to conform to a specific program. The degree of structural development necessary should be determined as part of an in-house technical assessment. It should be noted that even a Federal Aviation Regulation (FAR)-Part-25-certified air vehicle could be a major structural development if major mission variations adversely affected the structural life.
A.1.1 Performance requirements. The structural performance requirements should be established by the Program Manager. The structural performance requirements will identify the structural criteria which should be used to establish the strength, durability, and damage-tolerance of the air vehicle. This should include weights, speeds, altitudes, and runway surface preparation from which the air vehicle is to be operated.
A.1.2 Service goal concept. The Program Manager should also establish the desired service goal concept for the air vehicle, the missions to be flown, and the usage of those missions during the service goal.
A.1.3 Preliminary structural evaluation. The candidate air vehicle should be examined through a
preliminary structural evaluation. This effort should characterize the structural integrity of the proposed system and should be based on the database that currently exists for the air vehicle. This should be a critical evaluation of the certification basis for the air vehicle as compared to the requirements of the ASIP. The design criteria used in the certification process should be the basis for this evaluation. The ASIP should be tailored to be consistent with the intended use of the air vehicle and the scope of this evaluation. The primary effort should be an examination of vibration, acoustic, flutter, loads, static strength, fatigue and damage tolerance analyses, and the associated testing described in the first three tasks of the ASIP. The guidance for acceptable compliance with these tasks can be found in JSSG-2006. Particular attention should be given to the third task of ASIP, which includes the full-scale testing. The elements of this task-which include the laboratory static and durability tests and the flight and ground operations test-represent significant costs to the program if not previously executed or executed improperly. The lack of adequate testing may also mean there could be high risk that there is a structural deficiency. The individual air vehicle tracking program and the loads/environment spectra survey found in fourth task of the ASIP will, in general, not be included in the original certification basis for the air vehicle. For FAR Part 25 air vehicles, many of the ASIP required analyses and tests are routinely accomplished during the certification process. However, they should be critically examined for compliance with the ASIP. For FAR Part 23 air vehicles, the requirement for the evaluation is normally greater, since the structural requirements for these air vehicles are less stringent than for the FAR Part 25 air vehicles. In addition, consideration should be given to rules that were current at the time the certification took place, since the requirements have been significantly modified over the years.
The certification basis for air vehicles certified by foreign authorities should be examined on a case-by-case basis. If the certification basis is not considered adequate, then the air vehicle should be subjected to an in-depth technical assessment. This technical assessment should be based on the data provided by the contractor. This assessment should, in general, include effort in the vibration, acoustic, flutter, load, stress, fatigue, and damage tolerance analysis disciplines. Durability and damage tolerance are typically the areas where the certification basis is lacking.
The available database should be used for the in-house durability and damage tolerance assessment to locate critical areas of the structure. This should be a limited effort and should concentrate on a few generic areas and areas which, if found deficient, could result in major modification costs. The next task should be to generate a
flight-by-flight spectra of stresses at these critical locations. These spectra should represent the lifetime operation of the air vehicle, which should include loads from taxi, maneuvering, turbulence, and landing impact. Fracture analyses using these spectra of stresses should be used to estimate the durability and damage tolerance capability of the air vehicle. In some cases, the use of coupon testing may be required to provide validation of these analyses. These studies should be used as a basis to assess the economic impact of bringing the air vehicle into the U.S. Air
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