Tasks IV and V of the ASIP guidelines of MIL-HDBK-1530 define
the force management tasks for preserving the airworthiness of an aircraft
throughout its design life. According
to Berens, et al. , force management is the "specification and
direction of inspections, preventive maintenance, repairs, modifications, and
damage assessments required to economically prevent structural failure and
preserve the strength and rigidity of the individual airframe during its useful
life." The basic objective of ASIP
is to ensure operational safety and readiness of the aircraft. Force Management
objectives are to:
structural failures through an effective maintenance program of inspections,
repairs and modifications.
2) Preserve structural strength and rigidity through
an effective preventive maintenance program of environmental protection
and economic repair or replacement of deteriorating parts.
structural maintenance costs by eliminating unnecessary structural maintenance
actions through effective application of data on test and operational failure
modes and data on individual aircraft usage.
a basis for planning of system phase-out and future force structure.
The guidelines of ASIP Task IV are directed at the manufacturer
generated, force management data package
that provides the design usage FSMP and the mechanism for collecting and
analyzing data for updating the FSMP as required. Task V is directed at the implementation of
the force management activities by the Air Force. Figures 8.1.1 and 8.1.2 from MIL-HDBK-1530 are functional flow diagrams
of Tasks IV and V, respectively.
Under Task IV of ASIP, the airframe contractor devises a Force
Management Plan that contains three
essential parts: 1) the Force Structural Maintenance Plan (FSMP), 2) the
Loads/Environment Spectra Survey (L/ESS), and 3) the Individual Aircraft
Tracking (IAT) Program.
The initial FSMP presents the schedule for inspections and
maintenance actions for aircraft that are accumulating damage according to the
design loads spectra usage predictions.
It is updated when the baseline operational load spectra are developed.
The L/ESS is a data collection and analysis program designed to
provide the data to develop the baseline operational load spectra. A number of the force aircraft, usually
about twenty percent, are fitted with data
measuring and recording equipment.
Parameters such as accelerations, angular rates, airspeed,
altitude, weight and other load indicative quantities are obtained in a time
history form as the aircraft are flown.
The data are categorized by mission type and segment, and load histories
are calculated for the critical areas of the aircraft. These are the same areas which were identified in the critical parts list and which
will be subjected to subsequent inspection and possible repair or
modification during maintenance actions.
The new baseline operational damage accumulation rates based on the
L/ESS data are used to update the FSMP.
The IAT program is also a data collection and analysis effort
that is applied to each aircraft of the force. The minimum amount of data is collected that
will allow the estimation of the damage being accumulated. Comparison with the
baseline damage accumulation predictions allows modification of the FSMP
to account for the differences in usage of each aircraft.
The planning for these three parts of the FSMP should begin
with the initial design studies and the fracture control plan. Crack growth techniques used during the
design are also those used in the IAT and
FSMP portions of the program and should be formulated to permit easy
incorporation. Studies made for evaluation of the effect of different
load parameters on the loads computation and subsequently on crack growth
calculations should be used in development of the parameter list for the L/ESS
program. Accuracy requirements and parameter ranges should be selected to be
commensurate with the methods of analysis.
Figure 8.1.1. Functional Flow Diagram of ASIP Task IV from
Figure 8.1.2. Functional Flow Diagram of ASIP Task V from MIL-HDBK-1530
The following subsections present general descriptive comments
for the three major elements of force management. See Berens, et al.  for more complete descriptions and
discussions of these topics.