Full Electric Helicopter Anti-Torque

On the way to complete electric flight, the electrification of helicopter subsystems is an essential milestone. This paper discusses the design of an electric helicopter anti-torque system, which uses Kopter's AW09 helicopter as a platform and shall be tested in ground tests. Analysis of state of the art anti-torque devices for helicopters has helped to identify concepts, which are suitable to be combined with electric propulsion and actuation. Engineering models are used to estimate the power benefits of varied tail rotor RPM, enlarged and steerable vertical stabilizers and drag reducing devices, which cover the rotor in forward flight. In connection with operational benefits viewed from the OEMs perspective, an architecture is proposed which consists of an electric driven shrouded tail rotor, an electric pitch actuation system and additional aerodynamic surfaces, like a steerable vertical stabilizer and a drag optimized tail rotor cover. The systems were developed according to the results of a safety analysis to meet the requirements of CS-27. The electric tail rotor drive is designed with an internal level of redundancy that allows to compensate for subsystem failures

Design and Evaluation of Fault-Tolerant Electro-Mechanical Actuators for Flight Controls of Unmanned Aerial Vehicles

Electro-mechanical actuators (EMAs) are a primary actuation technology for unmannedaerial vehicles (UAVs). Intensive research has been conducted for designing and evaluating fault-tolerant EMAs for flight controls of UAVs to ensure their compliance with new airworthinessrequirements for safe operation over civilian zones. The state-of-the-art research involves severalfault-tolerant architectures for EMAs based on parallel electric motors or a single motor with internalfault-tolerant features. In this study, a fault-tolerant architecture is introduced, comprised of two serialelectric motors driven by two isolated controllers and a health monitoring system. The proceduresof developing various fault-tolerant features are discussed with a deep focus on designing healthmonitoring functions and evaluating their influence on the overall actuator stability and availability.This work has been conducted and evaluated based on operational data for ALAADy: a heavygyrocopter-type UAV at DLR (German Aerospace Center)

Contrast-enhanced imaging in hepatic epithelioid hemangioendothelioma: retrospective study of 10 patients.

PURPOSE  The purpose of this study was to analyze imaging findings in hepatic epithelioid hemangioendothelioma (HEHE) with a particular focus on contrast-enhanced ultrasound (CEUS). MATERIALS AND METHODS  This retrospective multicenter study included 10 patients with histologically proven HEHE from 5 European centers. All existing ultrasound images/videos were independently analyzed by 2 experienced examiners (DEGUM level III, internal medicine) using a standardized evaluation form. Patterns of contrast enhancement were correlated with computed tomography (CT), magnetic resonance imaging (MRI), and pathological findings. RESULTS  B-mode ultrasound, CEUS, CT, and MRI were performed in 90 %, 70 %, 100 %, and 90 % of patients, respectively. Multifocal HEHE could be observed in 80 % with affection of both liver lobes in 70 %. Analysis of CEUS revealed 3 characteristic patterns that correlated well with contrast patterns on CT and MRI: (a) peripheral nodular enhancement with centripetal fill-in and wash-out in the portal venous and late venous phase (PVLP), (b) rim-like arterial enhancement with wash-out in the PVLP, and (c) inversed target sign with/without wash-out in the PVLP. Wash-out in the PVLP as a sign suspicious of malignancy was observed in 6/7 patients (85.7 %). CONCLUSIONS  Knowledge of the different characteristic CEUS patterns is of importance to avoid misdiagnosis due to resemblance of patterns A and B to the much more common focal liver lesions hemangioma and intrahepatic cholangiocarcinoma. Of importance, sonographers should be aware that wash-out in the PVLP might be absent in some patients