Browse Topic: Pitot-static instruments
Air data measurement and calibration are fundamental components in the pursuit of accurate and reliable aerodynamic assessments. The systematic collection of essential data regarding air properties are important for evaluating aircraft performance under various conditions and configurations. The scope is to achieve a comprehensive understanding of airflow characteristics, which is fundamental for design improvements and operational strategies, contributing to safer and more efficient flight operations in a several range of scenarios. This type of data measurement is even more challenging for the AW609 Tiltrotor which combines vertical take-off technology capabilities with the fixed-wing flight efficiency. The activity starts from known pitot-static system calibration methodologies for conventional applications and shows what were the difficulties encountered in a non-conventional Tiltrotor approach. The paper goes through the presentation of the original Pitot-Static and Air Data system and all the problematics that driven to a design change. After the presentation of the new architecture and the new data collection activity, it will be discussed the optimization of the data calibration strategy, also related to some peculiarities of the Tiltrotor, and how it drives to infer the calibration curves for the Air Data Computers (ADCs).
This AS defines instruments which use inputs of static and pitot pressure equal to those which are utilized to establish the pressure altitude and speed of that aircraft. These pressures are applied to the instrument ports to provide means for generation of an aural warning whenever the aircraft reaches or exceeds the maximum operating limit speed. This Over Speed Warning Instrument function may be incorporated as part of an Air Data Computer, or an Air Speed Indicator, or an Air Speed/Mach Number Indicator, or other instruments. In those cases where the Over Speed Warning Instrument is part of another instrument, the standards contained herein apply only to the Over Speed Warning Instrument function. Each aircraft type and model has a defined maximum operating limit speed curve or curves which are a part of the airframe manufacturer's type certification approval data; this limit speed data shall be available from the subject airframe manufacturer as published in the operating manual for the aircraft type and model number and configuration.
Selective catalytic reduction (SCR) of oxides of nitrogen (NOx) with gaseous ammonia is the leading technology used to meet on- and off-highway NOx emission standards across the world. In typical SCR systems, a low-pressure injector introduces a solution of urea and water (UWS) into hot exhaust gases leading to atomization and subsequent spray processes that finally lead to production of gaseous ammonia. Through their synergetic effect, the UWS injector and mixing enhancement devices (such as static mixers or baffles) help deliver a uniform mixture of ammonia and NOx to the SCR catalyst with minimal urea-derived solid deposits. To develop an efficient and robust aftertreatment system, it is essential to have experimental and simulation capabilities to assess the behavior of sprays under flow conditions representative of engine exhaust. The experimental part of the present work uses an optically accessible, cold- or hot-flow capable test section (called Insitu test section) that allows optical observations and measurements of aftertreatment sprays in cross-flowing gas. Pitot tubes are used to measure gas velocity, and high-speed imaging is used in conjunction with laser diffraction drop size measurements to characterize the spray. CFD Simulations are conducted using the commercial finite volume code ANSYS FLUENT using the Lagrangian Drop - Eulerian Fluid framework. User defined functions are developed to prescribe accurate initial conditions for the spray, and custom MATLAB scripts are used for detailed post- processing. Predicted velocity fields, spray trajectories and drop sizes are compared against test data under both cold- and hot-flow conditions and effects of spray submodels and numerical model settings are investigated. Finally, implications of the findings from this study for diesel aftertreatment system CFD simulations are discussed.
FAA rotorcraft airworthiness regulations require calibration of pitot-static systems in all flight regimes. Of all methods commonly used, none has been applied in a manner showing full compliance, specifically in the takeoff phase and in determining CG (Center of Gravity) effects. A review of accepted Position Error Correction methods identifies the GPS-based true airspeed method, with an adapted execution and analysis technique, as the most practical in terms of equipment and efficiency to provide a complete airspeed system calibration. The level flight limitations of the GPS method are solved by a combination of flight profiles, continuous data recording and reduction technique. The GPS horseshoe method and the ORBIS constant turn radius method are expanded by varying the airspeed, altitude, and heading as required to provide an equation set solved for the wind components and true airspeed. The new variable parameter methods minimize wind variability effects and flight test time.
This document describes recommended methods, associated equipment, and test setups to assist in understanding and conducting pressure drop tests on fuel system components. Background information and suggestions are provided to improve accuracy and repeatability of test results. Although written specifically for fuel system components, the methods, equipment, and suggestions presented herein apply equally to pressure drop tests conducted on any equipment utilizing incompressible fluids.
Recent studies have found that high mass concentrations of ice particles in regions of deep convective storms can adversely impact aircraft engine and air probe (e.g. pitot tube and air temperature) performance. Radar reflectivity in these regions suggests that they are safe for aircraft penetration, yet high ice water content (HIWC) is still encountered. The aviation weather community seeks additional remote sensing methods for delineating where ice particle (or crystal) icing conditions are likely to occur, including products derived from geostationary (GEO) satellite imagery that is now available in near-real time at increasingly high spatio-temporal detail from the global GEO satellite constellation. A recent study using a large sample of co-located GEO satellite and in-situ isokinetic evaporator probe (IKP-2) total water content (TWC) datasets found that optically thick clouds with tops near to or above the tropopause in close proximity (≤ 40 km) to convective updrafts were most likely to contain high TWC (TWC ≥ 1 g m-3). These parameters are detected using automated algorithms and combined to generate a HIWC probability (PHIWC) product at the NASA Langley Research Center (LaRC). Seven NASA DC-8 aircraft flights were conducted in August 2018 over the Gulf of Mexico and the tropical Pacific Ocean during the HIWC Radar II field campaign. The convection sampled during four flights was observed by GOES-16 at 1- or 5-minute intervals, providing the first opportunity to analyze product performance from this new satellite. This paper will (1) present initial comparisons between GOES-16 and IKP-2 datasets during HIWC Radar II, (2) demonstrate GOES-16 products for select periods when high TWC was encountered with an emphasis on three flights with 1-minute imagery, (3) compare GOES observations and derived products from the HIWC Radar I and II campaigns.
NASA’s Langley Research Center has developed a new method for calibrating pitot-static air data systems used in aircraft. Pitot-static systems are pressure-based instruments that measure the aircraft’s airspeed. These systems must be calibrated in flight to minimize potential error. Current methods — including trailing cone, tower fly-by, and pacer airplane — are time- and cost-intensive, requiring extensive flight time per calibration. NASA’s method can reduce this calibration time by up to an order of magnitude, cutting a significant fraction of the cost. In addition, NASA’s calibration method enables near-real-time monitoring of error in airspeed measurements, which can be used to alert pilots when airspeed instruments are inaccurate or failing. Because of this feature, the technology also has applications in the health usage and monitoring (HUMS) industry. Flight test engineers can be trained to use this method proficiently in 12 days without costly specialized hardware.
Bell Helicopter's 525 Relentless will be the world's first commercially certified fly-by-wire helicopter. As a fully computer controlled aircraft, the design aims at higher safety through reduced pilot workload, increased situational awareness, and improved handling qualities. The flight control system that achieves these results operates with numerous redundant sensors that provide flight data and feedback to the flight control logic. This paper describes the development of the Bell 525's redundant Pitot static airspeed system, showing how computational fluid dynamics (CFD) models were used to perform initial calibration of the triplex system far ahead of first flight. Since air data readings interact with the flight control logic, it was important to have a reasonable airspeed calibration available for first flight. The Bell 525 aerodynamics team developed an analytical approach to model the triplex airspeed system to account for position error across the flight envelope. The analysis developed calibration curves for forward flight, descent, and climbs to meet FAA rules for accuracy. The resulting process has allowed the 525 to conduct its first flight and full envelope expansion with an accurate and reliable production airspeed system.
Nearly every military and commercial aircraft in the United States today uses pitot-static probes for accurate, repeatable airdata measurements. Recently, local angle-of-attack- and sideslip-sensing capabilities have been added to these probes to satisfy requirements for advanced aircraft with extended maneuvering envelopes. Probes made in advanced shapes to satisfy these requirements have been evaluated in wind-tunnel tests at angles of attack up to 90°, with favorable results. Flight tests of the Advanced L-probe Air Data Integration (ALADIN) program, directed toward evaluating the performances of these probes, were recently concluded at NASA Dryden Flight Research Center.
A novel airdata system based on flush-mounted pressure sensors has been developed for the X-33 aerospace vehicle. Denoted the "X-33 flush airdata sensing" (FADS) system, it was designed to overcome limitations of pitot-static probes that were used previously, as explained below.
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