Browse Topic: Military aircraft
Civil and military rotorcraft operators desire enhanced capabilities from their vehicles in terms of mission efficiency, effectiveness, productivity, and availability. A critical element of this challenge is associated with providing cold weather availability. Currently, cold weather operations are enabled by regulatory actions leading to Limited Approvals, Qualifications, Clearances, and Restrictions. Cold weather certification (clearance of a new aircraft) and continuing airworthiness (maintaining effectiveness of fielded aircraft) are data driven processes. This work provides guidance on an Icing Encounters Survey (IES) based data gathering method supporting continuing airworthiness organizations in improving fleet safety and capabilities during cold weather operations.
Low-level flight, defined by high-speed operations near terrain, represents a significant challenge in military rotorcraft missions while providing strategic advantages, such as radar evasion and heightened surprise. Recent conflicts highlight the urgent need for advanced low-level flight capabilities in the design of new rotorcraft. The close proximity to ground obstacles, combined with the complexities of piloting, necessitates precise control and robust handling qualities to prevent accidents. However, existing handling quality standards, such as MIL-DTL-32742, reveal limitations in assessing low-level maneuvers. Given the diverse array of new rotorcraft designs, driven by initiatives like the U.S. Army's Future Vertical Lift and NATO's Next Generation Rotorcraft Capabilities, a customized handling qualities evaluation for each design is impractical. In response, a performance-driven strategy has been implemented, scaling Mission Task Elements to align with aircraft performance
Piloted evaluations form a critical part of Handling Qualities (HQ) testing. Military rotorcraft standard ADS-33 outlines the widely accepted approach to perform HQ testing, including both methods to determine predicted and assigned HQs (Ref. 1). Recently, ADS-33 has been replaced with MIL-DTL-32742, which includes updates to previously defined criteria and tasks (Ref. 2). Assigned HQs are awarded using short-look tasks, so-called Mission Task Elements (MTEs), stylized to represent mission requirements. Test courses focus on external visual cues, used by the pilot to judge position. Setting up external courses is usually expensive and may not be feasibly possible. The MCRUER (Means of Compliance Requirements for UAM Evaluations and Ratings) system intends to support HQ evaluations, replacing physical test courses using virtual displays. Four MTEs were successfully demonstrated in flight by three pilots using a variable stability rotorcraft. HQ evaluations were performed both using
Maintaining the operational readiness of military helicopters demands repair solutions that are fast, reliable, and adaptable. This paper presents the integration of Gamma Alloys' advanced metal matrix composites (MMCs) into additive manufacturing (AM) techniques - specifically Cold Spray and Friction Stir Additive Manufacturing (FSAM) - as a transformative approach to helicopter repair and replace for the US Army.
This paper describes the development process of a comprehensive pilot-in-the-loop simulation framework suitable for preliminary feasibility, and on-deck handling qualities assessment of the Leonardo AW609 civil tiltrotor, when operating with the Italian Navy aircraft carrier Cavour. A pilot-in-the-loop engineering simulator was used for simulations in which steady, quasi-unsteady, and fully unsteady ship airwakes were created using Computational Fluid Dynamics (CFD) and experimental data. A dedicated analysis of the simulation environment provided a strong agreement with various pilot inputs and aircraft response parameters when compared with flight data. Snapshot CFD simulations taken from a simulated lateral entry on ship deck allowed a comparison of airframe loads predicted by the aeromechanical model. While there are some good agreements and matched trends, development is ongoing to improve these aspects. Back-to-back piloted simulator approaches found a relatively good
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift (FVL) platform of the US Army. The US Army's National Rotorcraft Technology Center (NRTC) project "Rotorcraft Handling Qualities Requirements for Future Configurations and Missions" was a U.S. Government and Industry co-funded three-year research project. A project team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address rotorcraft high-speed handling qualities. The High Speed Acceleration/Deceleration MTE was designed to provide suitable coverage in ADS-33 for handling qualities in Low/High Speed Transitional flight regimes (e.g. rotor-borne to wing-borne flight). The MTE objectives, descriptions, and performance criteria were developed via a series of piloted simulation sessions at each of the four teams' simulation
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Sikorsky has successfully planned and executed several significant aircraft structural certification programs for military aircraft in the past few decades. These certifications included the CH-53K® with NAVAIR, the HH-60W with the Air Force and the Raider X® Competitive Prototype Aircraft with the Army. The methodologies for these certifications addressed the different requirements of each of these branches of the military as well as satisfying emerging techniques for structural life management ("Sikorsky Airframe Full Spectrum Customer/Supplier Collaboration", Reference 1). Safe Life Crack Initiation, Flaw Tolerant (Enhanced) Safe Life Crack Initiation and Fail Safe Life Limit Crack Propagation analysis had been rigorously pursued and demonstrated in these programs. This paper takes a retrospective look at what turns out to be many similarities in these methodologies that previously have been the subject of significant debate in the industry. The combined knowledge of these
ABSTRACT A flight simulation model for the UH-60 Black Hawk based on Sikorsky's GenHel model is modified to simulate a locked failure of a main rotor swashplate servo actuator and is compensated by using the stabilator as a redundant control effector. Steady state trim analysis is performed to demonstrate feasibility of trimmed flight in various conditions with different locked servo actuator positions for the forward, aft, and lateral actuators. A model-following, linear dynamic inversion controller is implemented and modified to account for locked actuator position. Post-failure, the control mixing and feed-forward control coupling terms are reconfigured to partially reallocate the control authority in the longitudinal axis from the main rotor longitudinal cyclic to a symmetric deflection of the stabilator. This is done by manipulation of only the control allocation relating pilot stick inputs to servo actuator positions, the feedback control gains and mechanical rigging between
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the US Army. A team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address VTOL high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. Tracking MTEs based on a sum-of-sinewaves (SOS) command signal were defined for precision, aggressive and precision, non-aggressive applications. The command signals are derived from fixed wing analogs that have long been used to evaluate aircraft handling qualities. While the precision, aggressive SOS tracking tasks, the primary subject of this paper, are surrogates for air-to-air tracking and nap-of-the-earth tracking, the known forcing function
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the US Army. A team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that have been defined to address VTOL high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. The attitude capture and hold MTEs that are the subject of this paper were defined to be precision, non-aggressive tasks that build upon fixed wing analogs. The MTE objectives, descriptions, and performance criteria were assessed and refined via several checkout piloted simulation sessions. Formal evaluations were then conducted by Army test pilots at four simulator facilities, each featuring a unique high-speed platform including a generic winged
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift (FVL) platform of the US Army. The US Army's National Rotorcraft Technology Center (NRTC) project "Rotorcraft Handling Qualities Requirements for Future Configurations and Missions" is a U.S. Government and Industry co-funded three year research project. A Sikorsky-led project team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address rotorcraft high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. Break Turn MTE was defined for non precision, aggressive applications in order to provide a suitable coverage of aggressive air combat maneuvers in future ADS-33. The MTE objectives, descriptions, and
Corrosion occurs in diverse environments mainly on metallic parts. Helicopters are made of a huge percentage of metallic parts and need to have several maintenance steps to guarantee its functioning and its durability. The military helicopters are flying in different kinds of environment, which cover large spectrum of severity of the atmospheric corrosion [1]. In maritime conditions, the most influencing factor is the Time of Wetness, which is a direct result Relative Humidity and Salt loading. The main material used for aircraft and that is suffering from corrosion is aluminium. There are plenty of data to follow the corrosion as a function of the environmental conditions, mainly on the sensitivity with sodium chloride, Relative Humidity, film thickness, etc... [2][3]. The maintenance efficiency on helicopters is dependent on the environmental severity. The U.S. armed forces estimate $10.2 billion in corrosion costs for their aviation and missile fleets during 2016 [4] [5] [6]. The
The Advanced Helicopter Seating System (AHSS) was started as an effort to evaluate and improve the current state of military rotorcraft seating. The overall goal of the program has been to improve pilot ergonomics and safety through the integration of advanced energy absorption and vibration reduction mechanisms as well as a broad approach to system integration based around updated occupant anthropometrics. An entirely new seating solution has been developed, with intent to integrate with the AH-64 Apache platform for demonstration purposes. The AH-64 development culminated with a series of static tests and dynamic test events to measure the effectiveness of the safety systems integrated on the seat as compared to the legacy AH-64 seating system. While lumbar load data and seat stroke data was obtained, issues with the anthropomorphic test device (ATD) configuration at the 95th male configuration caused some data to be suspect, and premature failure of several components also caused
The use of converging-diverging (C-D) variable area nozzle (VAN) in military aeroengines is now common, as it can give optimal expansion and control over engine back pressure, for a wide range of engine operations. At higher main combustion temperatures (desired for supercruise), an increase in the nozzle expansion ratio is needed for optimum performance. But changes in the nozzle throat and exit areas affect the visibility of engine hot parts as the diverging section of the nozzle is visible for a full range of view angle from the rear aspect. The solid angle subtended by engine hot parts varies with change in visibility, which affects the aircraft infrared (IR) signature from the rear aspect. This study compares the performances of fixed and variable area nozzles (FAN and VAN) in terms of engine thrust and IR signature of the engine exhaust system in the boresight for the same increase in combustion temperature. This study is performed for two cases: (i) variable throat area and
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Military rotorcraft engines operating in harsh environments routinely ingest large quantities of mineral dust, which can degrade components and ultimately reduce operability. Time off-wing for unscheduled maintenance is a costly burden, both financially and operationally. Rapidly predicting engine deterioration rates as a function of the mission presents an opportunity to optimise flow of supplies, better manage fleets, and perform safety risk assessments when dust loading is expected to be particularly high. In the current contribution, we present our ongoing efforts in this field with a new methodology for assessing the effectiveness of inertial particle separators and quantifying the changes they impart to the inbound dust. We demonstrate that both the concentration reduction and the modification to the particle size distribution can be made on the basis of a single independent variable- a generalised Stokes number for inertial particle separators- and a single performance parameter
The U.S. Department of Defense has begun the acquisition of the next generation of military rotorcraft, named Future Vertical Lift (FVL), to replace its aging fleet. U.S. Army Futures Command intends to sustain FVL under a new strategy of maintenance free operating periods (MFOP). This study developed a discrete event simulation to evaluate MFOP success given component reliabilities, desired MFOP duration, and operational tempo of a battalion with thirty aircraft. The simulation compared notional FVL aircraft with improved reliability to today's fleet. Results indicated that inherent reliability alone was insufficient to achieve MFOP goals and that prognostics and diagnostics with robust information management are necessary. Sensitivity studies found the recovery effort after an MFOP was linked to the MFOP duration. Recovery downtime was tied to both the duration and operational tempo. Availability and cost improved with moderate gains in MFOP duration by eliminating unnecessary
Future vertical lift (FVL) missions will be characterized by increased agility, degraded visual environments (DVE) and optionally piloted vehicles (OPVs). Increased agility will induce more frequent variations of linear and angular accelerations, while DVE will reduce the structure and quality of the out-the-window (OTW) scene (i.e. optical flow). As helicopters become faster and more agile, pilots are expected to navigate at low altitudes while traveling at high speeds. In nap of the earth (NOE) flights, the perception of self-position and orientation provided by visual, vestibular, and proprioceptive cues can vary from moment to moment due to visibility conditions and body alignment as a response to gravitoinertial forces and internally/externally induced perturbations. As a result, erroneous perceptions of the self and the environment can arise, leading ultimately to spatial disorientation (SD). In OPV conditions, the use of different autopilot modes implies a modification of pilot
In application, the Aeronautical Design Standard for the handling qualities of military rotorcraft, ADS-33E-PRF, provides the means to effectively predict rotorcraft handling qualities via validated criteria and demonstrate actual handling qualities in flight test using mission task elements. Besides a definition, a note that rotorcraft shall have no tendencies, and a note regarding Attitude Command Response-Types and gain bandwidth frequency, the topic of pilotinduced oscillations (PIO) is not addressed via specific criteria or flight test techniques. As the use of full authority fly-by-wire flight control continues to expand in Vertical Takeoff and Landing (VTOL) aircraft, the likelihood of encountering PIO will also expand. In the fixed wing world where PIO has been commonplace, at least in developmental test if not operations, predictive analytical methods that can also be used for detection of PIO in realtime have been developed, which can also be applied to rotorcraft
Advancements in Damage Tolerant Airframe Structures in combination with Structural Health Monitoring (SHM) have created an opportunity to exploit the synergies in these technologies to change the paradigm for Airframe Life Management for future Aircraft. In the last decade or more, Sikorsky has validated multiple production helicopter Airframes using Damage and Flaw Tolerant certification requirements. The experience of the authors of this paper contributed to the recent joint services and industry development of the Rotorcraft Structural Integrity Program (RSIP as specified in MIL-STD-3063) for design of future military rotorcraft. In addition, Sikorsky has also developed a range of technologies relevant to SHM to reduce over-inspection and maintenance to drive increased operational availability. Combined, these developments will allow new Airframe designs to meet the US Army's new requirements for Maintenance Free Operational Periods (MFOP), for example 200 flight hours for the
The U.S. Army monitors the structural integrity of its rotary-wing aircraft fleet through annual evaluations and reporting via the Airframe Condition Evaluation (ACE) program. ACE evaluations capture the location and character of structural defects for each aircraft, which are then available for trending and detailed analysis by engineers with the U.S. Army Combat Capabilities Development Command Aviation & Missile Center (CCDC AvMC). As analytic methods are increasingly advanced through the digital thread, CCDC AvMC has sought to improve available trending, modeling, and analysis tools beyond status quo to provide higher fidelity visuals to both aid communication with decision makers, and also to reveal structural defect trends which may not otherwise be evident. This paper will detail the development and utility of the ACE Color Mapping Application within the ACE Mapping Module and its impact on product support of U.S. Army aircraft with regard to airframe structural integrity.
The US Marines CH-53K King Stallion replaces the venerable CH-53E Super Stallion and delivers almost triple the payload over the primary mission radius of 110 nm, while maintaining the same shipboard footprint. In order to achieve this the main gearbox design had to achieve an unprecedented power density. The main gearbox is a split torque gear box with three input clusters and four dual herringbone drive pinions per cluster. This paper addresses the challenges related to contact pattern development of the MGB 3rd-stage gear meshes.
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