Airlift Operations Research Articles

Optimizing Dynamic Airlift Operations: Winning Strategies in the AFRL Airlift Challenge

The Air Force Research Laboratory (AFRL) has sponsored the Airlift Challengeover the past two years, aimed at addressing the dynamic airlift problem. Thedynamic nature of the challenge included the random disappearance of graphedges to simulate adverse weather conditions and the spontaneous appearance ofcargo requiring delivery. This poster presents the systems that won both the 2023and 2024 challenges. The initial approach focused on intelligent solutions for subtasks, or 'build-smart'. It soon became clearthat the optimization of the scoring rate, points per second, was moreimportant than single instance metric performance. In the subsequentcompetition, a 'build-fast' strategy was adopted due to this observation. Thispaper discusses the impact of iteration on algorithm selection for optimizationproblems and suggests considerations for structuring scoring processes infuture competitions.

Screening the Lipid Production Potential of Oleaginous Yeast Yarrowia lipolytica under Wood Hydrolysates

Since Yarrowia lipolytica, an oily yeast, contains many valuable products as biomass, to increase its widespread use, it is very important to develop a sustainable production model. In this study, the production of high acid hydrolysate from sawdust biomass, which is produced in very high amounts in our environment, and the effect of these products on the growth efficiency of Yarrowia lipolytica were investigated. A preliminary statistical analysis was carried out to assess sugar production from sawdust by hydrolysis, which estimated 85% of total sugar recovery (TSR) using 96 g of sawdust, while TSR at the highest sawdust was as high as 79%. There was a higher loss in the recovery of C5 sugars with acid and time. This study revealed that Y. lipolytica could grow with high biomass yields in varying hydrolysate concentrations, approaching yields achieved in synthetic glucose media. The maximum biomass obtained was 13 and 26 g in batch and airlift operations, respectively, using organic nutrients. Biomass and lipid yields from kinetic modeling provided a close approximation to the experimental yields performed on an airlift reactor. It was found that Y. lipolytica biomass cultivated on sawdust hydrolysates had significant lipid and protein compositions, as high as 29 and 38%, respectively.

Deep lifted decision rules for two-stage adaptive optimization problems

This paper presents a novel method to generate flexible piecewise linear decision rules for two-stage adaptive optimization problems. Borrowing the idea of a neural network, the lifting network consists of multiple processing layers that enable the construction of more flexible piecewise linear functions used in decision rules whose quality and flexibility is superior to linear decision rules and axially-lifted ones. Two solution methods are proposed to optimize the weights and the decision rule approximation quality: a derivative-free method via an evolutionary algorithm and a derivative-based method using approximate derivative information. For the latter method, we suggest local-search heuristics that scale well and reduce the computational time by several folds while offering similar solution quality. We illustrate the flexibility of the proposed method in comparison to linear and axial piecewise linear decision rules via a transportation and an airlift operations scheduling problem.

Selecting a Cargo Aircraft for Humanitarian and Disaster Relief Operations by Multicriteria Decision Aid Methods

Airlift operations are vital to support contingency plans during the major humanitarian and disaster relief (HDR) events. The access to disaster zones is often limited by unsafe conditions, poor road infrastructure, and lack of commercial air services. To overcome these limitations, the development of larger planes has allowed bulkier equipment and larger quantities of supplies to be transported by fewer flights. Embraer developed the KC-390 airplane to carry out logistics support and HDR missions. Multinational HDR events usually call for a wide variety of aircraft. The comparison between the KC-390 and the C-130 gains relevance under these circumstances, where the two will be competing for use in emergency support. This article aims to provide support for the allocation of the appropriate aircraft to each mission, by quantifying the advantages (and possible disadvantages) of the KC-390 compared with the C-130 based on the relative difference of their technical performance. Consolidated scores are established through the probabilistic composition of preferences by combining preference probabilities using weighted sums. The weights are calculated based on the experience of pilots applying the analytical hierarchical process. Among the types of missions analyzed, search and rescue present the highest difference in technical performance, in favor of the KC-390.

The Airlift Planning Problem

The U.S. Transportation Command (USTRANSCOM) is responsible for planning and executing the transportation of U.S. military personnel and cargo by air, land, and sea. The airlift planning problem faced by the air component of USTRANSCOM is to decide how requirements (passengers and cargo) will be assigned to the available aircraft fleet and the sequence of pickups and drop-offs that each aircraft will perform to ensure that the requirements are delivered with minimal delay and with maximum utilization of the available aircraft. This problem is of significant interest to USTRANSCOM because of the highly time-sensitive nature of the requirements that are typically designated for delivery by airlift, as well as the very high cost of airlift operations. At the same time, the airlift planning problem is extremely difficult to solve because of the combinatorial nature of the problem and the numerous constraints present in the problem (such as weight restrictions and crew rest requirements). In this paper, we propose an approach for solving the airlift planning problem faced by USTRANSCOM based on modern, large-scale optimization. Our approach relies on solving a large-scale mixed-integer programming model that disentangles the assignment decision (which aircraft will pickup and deliver which requirement) from the sequencing decision (in what order the aircraft will pickup and deliver its assigned requirements), using a combination of heuristics and column generation. Through computational experiments with both a simulated data set and a planning data set provided by USTRANSCOM, we show that our approach leads to high-quality solutions for realistic instances (e.g., 100 aircraft and 100 requirements) within operationally feasible time frames. Compared with a baseline approach that emulates current practice at USTRANSCOM, our approach leads to reductions in total delay and aircraft time of 8%–12% in simulated data instances and 16%–40% in USTRANSCOM’s planning instances.

Numerical investigations of the crosswind stability of the Korean light tactical vehicle during airlift

The Korean light tactical vehicle (KLTV) is a new military vehicle that was developed to meet the demands for airlift by helicopter. Special lifting kits were installed in the front and rear ends of the KLTV, and the performance of the KLTV was verified by an airworthiness test. As most of Korea is mountainous, the airlift capability of military vehicles to conduct rapid operations is becoming more important, especially because a gust of wind in a canyon or on the coast during airlift operations can threaten the security of the helicopter and vehicle. This paper presents a dynamic analysis method to evaluate the effect of crosswind on the high-speed vehicle during an airlift. First, MSC.ADAMS/Car is used to construct a full car model of the KLTV with 107 degrees of freedom. Next, a test rig for airlift and an aerodynamic load template are developed and coupled with the dynamic model of the KLTV. Thereafter, dynamic analyses of helicopter flight speeds, crosswind speeds, and crosswind angle are performed. Finally, sling forces under crosswind and MIL-STD-209K condition are compared to review the structural safety of the airlift device for KLTV. The proposed numerical method will offer helpful data on the crosswind stability of a military vehicle equipped with airlift provision.

Analytical method to develop airlift equipment for Korean light tactical vehicle

The Korean light tactical vehicle (KLTV) is developed to meet the demands for a new military vehicle that fulfills certain conditions, such as multi-purpose, high mobility and survivability. Double-wishbone independent suspension is developed to improve the ride and handling performance and maximize the off-road driving performance of the new tactical vehicle. In particular, the KLTV is equipped with front and rear lifting provisions that support the vehicle safely during airlift operations. In this paper, a comprehensive analytical method to evaluate the structural safety of these components is presented. First, a vehicle dynamic model of the KLTV and a test rig for airlift simulation are developed using MSC.ADAMS/Car. Second, a finite element model of airlift kits, which are newly installed in the KLTV, is constructed. Third, stress analyses on vertical load conditions, MIL-STD-209K, and helicopter flight speeds are performed using ABAQUS. Finally, a dummy apparatus test and an actual vehicle test are conducted to verify the suitability of the airlift equipment for the KLTV. The computational method presented herein will provide useful information on the structural safety of airlift equipment during the early stages of a military-vehicle-designing process.

The Effect of Robust Decisions on the Cost of Uncertainty in Military Airlift Operations

There are a number of sources of randomness that arise in military airlift operations. However, the cost of uncertainty can be difficult to estimate, and is easy to overestimate if we use simplistic decision rules. Using data from Canadian military airlift operations, we study the effect of uncertainty in customer demands as well as aircraft failures, on the overall cost. The system is first analyzed using the types of myopic decision rules widely used in the research literature. The performance of the myopic policy is then compared to the results obtained using robust decisions that account for the uncertainty of future events. These are obtained by modeling the problem as a dynamic program, and solving Bellman’s equations using approximate dynamic programming. The experiments show that even approximate solutions to Bellman’s equations produce decisions that reduce the cost of uncertainty.

Airlift mission monitoring and dynamic rescheduling

We describe the Flight Manager Assistant (FMA), a prototype system, designed to support real-time management of airlift operations at the USAF Air Mobility Command (AMC). In current practice, AMC flight managers are assigned to manage individual air missions. They tend to be overburdened with associated data monitoring and constraint checking, and generally react to detected problems in a local, myopic fashion. Consequently, decisions taken for one mission can often have deleterious effects on others. FMA combines two key capabilities for overcoming these problems: (1) intelligent monitoring of incoming information (for example, weather, airport operations, aircraft status) and recognition of those situations that require corrective action and (2) dynamic rescheduling of missions in response to detected problems, both to understand the global implications of changed circumstances and to determine appropriate rescheduling actions. FMA builds on two existing technologies: an execution-monitoring framework previously applied to small-unit operations and control of robots, and a dynamic scheduling tool that is transitioning into operational use in AMC's Tanker/Airlift Control Center. FMA's dynamic-mediation module provides for collaborative mission management by different planning and execution offices by structuring communication for decision making.

USAF Airlift into the Heart of Darkness, the Congo, 1960-1978: Implications for Modern Air Mobility Planners

Abstract : Airlift operations in Third World countries are always a challenge due to distances and lack of airfield facilities. USAF airlifters met that challenge three times in the Congo in 1960-64, 1964, and 1978. These operations serve as a blueprint for future air mobility contingencies. Since coalition operations are a vital part of U.S. strategy, comparing and contrasting Belgian Air Force operations in the Congo in conjunction with USAF operations are useful to anticipate the future. When the Congo gained independence in 1960 from Belgium, rioting and violence threatened white lives. The Belgian government tried to restore order and evacuate refugees. Belgian Air Force operations in July 1960 demonstrated improvisations to aircraft and a high operations tempo. But under pressure from the United Nations Security Council Belgium had to withdraw. The USAF entered the Congo with the goal of saving Americans and providing food to the newly independent state. On 14 July 1960 the USAF became the airlift arm of United Nations security force dispatched to the Congo from over 34 countries. The USAF continued to support the UN operation until 30 June 1964 when the last UN soldier went home. In the three years separating the start and conclusion of this massive undertaking, the USAF rotated troops and maintained the logistical lifeline the UN needed. However, the USAF conducted its most ambitious airlift in the Congo in November 1964. Internal revolts continued as rival groups sought to dominate the government. On August 4, 1964 the eastern city of Stanleyville was captured and American State Department personnel were seized. USAF C-130 aircraft flew Belgian Para-Commandos to the Congo and then on to a parachute assault on Stanleyville. A second jump took place 48 hours later. This operation foreshadowed future African adventures by the European powers.

Routing airlift aircraft by the double-sweep algorithm

In this paper, we describe the problem of modeling the routing of aircraft across a network of enroute bases. This is done to provide routes for scenarios that are being studied by the analysis tools at the Airlift Mobility Command. We are primarily concerned with the development of routes that can be easily implemented with the airlift operations analysis tools in use at AMC. We will describe the specific implementation issues that have been addressed. One such issue is the use of available data in a specific input file format. Another crucial issue is adapting the base-to-base route set provided by the double-sweep algorithm into a region-to-region route set which can be used by the airlift analysis models. The methods used to adapt the route sets appropriately are described, and test results are provided for two different scenarios. Finally, recommendations that were given to the analysts at AMC for use of the k-shortest path routine are given.

Mean Value Analysis of Military Airlift Operations at an Individual Airfield

An analytical queueing network model of military airlift operations at an individual aire eld is developed and implemented. The aire eld system is represented as a capacitated open network of multiserver queues and forkjoin constructs that capture concurrent aircraft e ow through subnetworks of activities. Generated performance measures include mean values for system throughput, aircraft ground time, and resource utilizations. The quality of the analytical approximation is demonstrated through comparison with simulation results.

An Execution Planning Algorithm for Military Airlift

Execution planning at the military airlift command of the US Air Force involves updating the routes and schedules of aircraft to reflect changing requirements for moving freight and personnel and changing airlift resources. The problem can be characterized as a pickup and delivery problem with time windows and node capacities. The constraints on the capacities of the nodes (airfields) limit the rate at which the aircraft can be serviced and the amount of requirements (tonnage of cargo, number of passengers) that can be loaded and unloaded at an airfield per day. The execution planning algorithm described can be used daily to modify the existing airlift operations plan. An algorithm based on the insertion heuristic was selected for implementation due to its computational feasibility and its capability to absorb complex constraints arising in the execution planning problem. The insertion heuristic has the additional desirable feature of keeping intact as much of the existing schedule as possible.

Heuristics for Scheduling Aircraft and Crew during Airlift Operations

The Air Force is frequently placed in a situation where a large quantity of goods must be transported between various locations in a specified time period by Air Force personnel. The goods are of different and interrelated types; thus, the sequence of missions is specified to maintain a proper balance of goods at each location. Other vital considerations include both aircraft maintenance and health and alertness maintenance for pilots and personnel. Nevertheless, economy in operations needs to be demonstrated. Thus, the problem addressed in this paper is one of minimizing the number of crews used in the airlift, subject to crew rest requirements and the completion of all missions within the specified time frame. It is assumed that all routes, missions, and aircraft are predefined with limited crew availability. Results of computational testing are provided where the proposed algorithms are compared to the current Air Force methods.

Improving Utilization of Air Force Cargo Aircraft

The Deployable Mobility Execution System (DMES) was developed for the US Air Force to improve aircraft utilization and responsiveness in airlift operations. The model uses a modified cutting stock heuristic to generate feasible cargo loads, which the planner can modify using detailed interactive graphics. The system runs on a small, off-the-shelf microcomputer which can be operated at remote sites. In three tests during military exercises, the system reduced load-planning man-hours by 90 percent and increased airlift utilization by 10 percent. During the Grenada rescue operation in October 1983, the system saved over $2.5 million in flying-hour costs and provided timely planning. Projected annual savings for peacetime exercises are estimated to exceed $20 million. More importantly, DMES significantly improves airlift support of combat operations.

German Air Force Air Lift Operations.

German Air Force Air Lift Operations.

Stochastic programming models for scheduling airlift operations

AbstractThis article describes an analytic approach to flight scheduling within an airlift system. The model takes explicit account of the uncertainty present in cargo requirements or demands. For computational feasibility, the approach consists of two related models: (1) a monthly planning model that produces an initial schedule, and (2) a daily model for making periodic changes in the schedule. Both are formulated as two‐stage stochastic linear programs. A detailed mathematical description of each model and its physical interpretation is given.The monthly model determines the number of flights each type of aircraft in the fleet. Excess demands on certain routes are assumed to be met, at least in part, by spot procurement of commerical lift from outside the system. The flight assignment is determined by minimizing the expected total system cost, which consists of operating costs, costs of reallocating aircraft to different routes, spot commercial procurement costs, and other penalty costs of excess demand. The model accounts for limitations on the number of flying hours and the carrying capacities of various aircraft in satisfying demands.In the daily model the number of aircraft of each type to switch from one route to another and the number of commercial flights on spot contract to add on the current day are the principal decision variables. These are determined by balancing operating, procurement, and redistribution costs against the expected costs of additional cargo delay. The current state of the system — the amount of unmoved cargo on various routes andathe position of aircraft throughout the system — plays a role in determining these decisions.A description of two variants of an algorithm recently developed for this class of problems is presented. Both versions, which use ideas from convex programming, make extensive use of linear programming codes for the brunt of the calculations. The models may thus be solved by augmenting existing linear programming routines.

Use of Gas Lifts in the Mid-Continent Field

For some time it has been more or less recognized within the industry that ascientific control of flowing wells would result in increased production and agreater ultimate recovery of oil. About two years ago it was proposed by thewriter that this control should follow principles worked out by him whilehandling large air-lift operations. In the case of wells that had ceased toflow where a large quantity of liquid was present, the use of these principleswould result in a large increase of production by using compressed air or gasto flow the well; in the case of a well flowing naturally it would take theform of controlling the gas associated with the oil, resulting either inimmediate increase of production or in a reduction of the gas consumed perbarrel of oil, and in both cases would result in a greater ultimate recoveryfrom the sand. The Roxana Petroleum Corp., appreciating the advantages to be obtained by ascientific application of the principles of the air lift to oil wells, recentlyengaged, for a limited time, the services of the writer to work out some of theproblems involved. The work was carried out at Braman, Garber and Tonkawa inOklahoma, and at Oxford in Kansas. Following some suggestions of the writer awell was also equipped by the Roxana company at Smackover by A.S. Feild. Increased Production by Application of Air Lift The results of the use of this method were, as a whole, quite satisfactory, in so far as it was possible to carry out these ideas in a limited time. Atotal of 14 wells produced 6590 bbl. before installation of the air lift and13,847 bbl. afterward, thus giving an increase of 110 per cent. The range ofincrease was from 5 to about 400 per cent where conditions were favorable forthe use of the air lift, indicating that in many cases wells would yield agreater production of oil if the fluid were removed as rapidly as it enters thewell. Most of this increase was made on wells already provided with the usualtype of gas lift. In bringing about this change in operating conditions it was arranged to removeall back-pressures wherever possible.