Airdrop Operations Research Articles

Hierarchical mission planning for multiple vehicles airdrop operation

PurposeAirdrop operation has become an important transportation mode due to its mobility and rapidity and mission planning is one of the critical steps in the preparation of an airdrop operation. The purpose of this paper is to propose an efficient mission planning method for airdrop operation using multiple vehicles.Design/methodology/approachA hierarchical mission planning method is proposed. According to the objectives of the action, the mission planning is divided into three planning levels to form the hierarchical structure and the constraints are distributed among them. By doing so, the proposed approach converts the original mission planning problem to a constrained optimization problem, which is solvable using existing mathematical methods.FindingsOn the basis of analysis, the mathematic models of three planning levels are established. Each level has its own optimization objective, taking part of constraints into account. The integrated mission scheme had been obtained step by step.Practical implicationsThis paper systematically tackles the complicated multiple vehicles airdrop mission planning problem, and it provides a platform for optimizing the outcomes. The mathematical models established in this paper could apply in a variety of more complex mission scenarios.Originality/valueThis paper fulfils an urgent need to study how the advantages of airdrop operation can be maximized through planning airdrop mission schemes carefully.

Simulating the Flows About Cargo Containers Used During Parachute Airdrop Operations

This paper presents results from a Navier-Stokes finite volume flow solver simulating the flowfields around a platform and cargo configuration representative of platforms used for military parachute airdrops. The platform and cargo configuration consists of a flat plate model with an aspect ratio (width/length) of 0.56, upon which a box representing cargo is placed. This combination is simulated in conditions approximating the fall of a container prior to, and after parachute deployment and inflation, including a full 360 ◦ angle of attack range at a Reynolds number of 2.94 ·10 6 (freestream velocity of 30ft/s). The static simulations approximate those cases where the tumbling of the container (mostly prior to parachute deployment) is slow enough to approximate near-steady state flow conditions. Results include lift, drag, and moment coefficients over the range of flow conditions, as well as pressure contours to help elucidate relevant flow physics around the pallet-cargo configuration. Results show the flow orientation (into the nose bumper or flat side first) significantly affects the drag and moment behavior, but not the lift coefficient. Lift curve slopes match well to previously published data on pallet and cargo geometries as well as flat plates with similar aspect ratios. Drag and moment coefficients were significantly different between flow orientations; drag coefficients exhibit asymmetry between positive and negative angles of attack while moment coefficients illustrate that flow into the nose bumper may be more stable during extraction but much less stable during steady descent.

A single heavy load airdrop and its effect on a reversible flight control system

PurposeThis paper aims to investigate the addition of airdrop capability to a commuter aircraft and its consequences on the reversible flight control system.Design/methodology/approachAirdrop was modeled to include its effect on aerodynamics and flight control system. A mathematical model was also developed for the reversible longitudinal flight control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi‐body dynamics code and validated using existing manufacturer's data which included recorded data from flight. The airdrop simulation results showed that the flight control system is affected in two steps. In the first step, the movement of the load required a forward force by the pilot. In this step, the elevator power was a key factor and had to be increased to allow the pilot to keep the aircraft in trim position during the airdrop. In the second step, a sudden forward shift of centre of gravity required an abrupt change in the direction of applied force. The maximum allowable force and control column movement had to be checked. In the case under study, they did not impose any difficulty.FindingsThe result showed that a special consideration had to be taken into account when an aircraft with reversible flight control system was to be used for airdrop mission.Originality/valueThis paper investigates the behaviour of a reversible flight control system during airdrop operation through analysis and simulation.

Personnel Airdrop Simulation

We develop an object-oriented simulation that models the airdrop mission of a U.S. transport aircraft, the C-1 7 Globemaster III. The simulation, written in MODSIM III, is based on three basic object types: an aircraft, a wake vortex, and a paratrooper. The aircraft object provides the required aerodynamic constants for simulating the wake vortices generated off each wingtip; the vortex object includes velocity field and decay models as well as a position algorithm; and the paratrooper object implements a 6-degree-of-freedom trajectory model. Using the simulation, we generate vortex encounter information for various formations and wind conditions, and quantify the associated risk of paratrooper/vortex encounters in a potential en counter rate. Time over the drop zone is a primary concern in any airdrop operation, and the results of this analysis form a tool that allows the ground com mander to assess the risk involved in decreasing that time.

Development of the C-17 Formation Airdrop Element Geometry

The analysis and tests that determined the C-17 three ship element geometry suitable for formation airdrop operations at night are discussed. The objective is to avoid jumpers encountering vortices generated from aircraft upstream. A measure of merit is developed based on the closest predicted lateral proximity between a vortex and a jumper. The geometry tested underwent two changes during the course of the test, due to the introduction of tolerance boxes for aircraft position and vortex encounters which occurred during early testing. An echelon geometry 6000 ft long and 1500 ft wide was ultimately adopted. In 101 passes over the drop zone, 1349 mannequins and 1251 personnel were dropped from this formation geometry without vortex encounter. NOMENCLATURE b Wing span DM Formation design margin, eq. (1) DZ Drop zone ti Parachute opening time V Aircraft velocity, ft/sec X Downstream distance between aircraft, ft Y Lateral distance between aircraft, ft, positive to starboard

Controlled opening method for clustered parachutes

This paper presents a method for achieving simultaneous opening of clustered parachutes. The method involves connecting and partially reefing the parachutes in a cluster during the initial stage of the opening so that they open together as a single parachute; they are then disconnected and disreefed at almost full inflation, thereby controlling and opening the parachute simultaneously. This method, called the controlled opening method, was tested with clusters of 64-ft-diam G-12 cargo parachutes, 100-ft-diam G-ll cargo parachutes, and 28-ft-diam C-9 personnel parachutes. Their openings were significantly improved when compared to the openings of these clusters without using the controlled opening method. LUSTERED parachutes offer several advantages over a single large parachute. The important ones are shorter opening time and distance, easier fabrication and ground re- covery, and more stable descent. The major difficulty of clus- tered parachutes is that parachutes in a cluster generally open randomly and unevenly; the random opening results in a large variation in opening times and an uneven distribution of open- ing forces among the parachutes. Consequently, the lead- opening parachutes are often damaged, resulting in an un- satisfactory airdrop operation. In view of the importance of uniform opening of clustered parachutes, some fundamental studies of flowfields and open- ing of clustered parachutes were conducted by Braun and Walcott,1 Heinrich and Noreen,2 Heinrich et al., 3 Wolf and Spahr,4 and Nicuum and Kovacevic.5 Current techniques for improved cluster opening are generally those used for con- trolling the opening of a single parachute. They include reef- ing the canopy skirt, adding a secondary chute at the skirt, introducing a pull-down centerline, and applying tension force at the apex by a drogue chute. These techniques generally modify the opening of a single parachute, but they do not necessarily improve the opening of a cluster as a whole. This is evidenced by the current problems in opening 100-ft-diam standard U.S. Army G-ll cargo parachute clusters6 and the great difficulties in opening 137-ft-diam developmental cargo parachute clusters.7-8 Most recently, Johnson9 developed a central reefing/disreefing system that addressed the opening of a cluster as a whole. His system improved the opening of a cluster of three 52.5-ft-diam parachutes. This paper presents a method for improved opening of clustered parachutes. The method was tested extensively with clusters of various size and number of parachutes. Test results demonstrated that the method improves their opening significantly.

United States air-drop operations in Antarctica, 1956–59

The establishment of the United States IGY stations at the South Pole and in Marie Byrd Land, with their subsequent annual re-supply, has involved the delivery of men and matériel by air on a scale previously unknown to Antarctic operations. “Amundsen-Scott” station at the South Pole was planned and executed entirely by air, with C-124 Globemasters of the United States Air Force air-dropping the great bulk of the required cargo tonnage, and Navy ski-equipped R4D and P2V aircraft delivering personnel and nondrop cargo. In the case of “Byrd” station, the bulk of the cargo was planned for delivery from “Little America V” by tractor train, assisted by skiequipped aircraft carrying personnel and some cargo to the station, and giving logistic support to the tractor trains. A considerable amount of matériel was also air-dropped by the C-124's, both cargo for the station and fuel for the tractor trains. In addition, a small amount of cargo was air-dropped for the setting up of the small summer station on the South Pole route (formerly “Liv Camp”, now the “Naval Auxiliary Air Facility, Beardmore Glacier”).