Sun Gear Fault Detection on an OH-58C Helicopter Transmission
Adrian Hood Research Assistant Alfred Gessow Rotorcraft Center Department of Aerospace Engineering University of Maryland College Park, MD 20742-3015 Darryll Pines Dean and Farvardin Professor A. James Clark School of Engineering University of Maryland College Park, MD 20742-3015
Detecting seeded faults on a full-scale helicopter transmission is the focus of this paper. Two methods to isolate the dynamics of an individual sun gear, in an effort to assess its condition, are developed and validated on an OH-58C helicopter transmission’s planetary reduction stage. Planetary indexing is used to geometrically synchronize dynamic measurements with the positions of the meshing teeth. This provides the opportunity for source/signal mapping that can lead to increased sensitivity, allowing faults to be detected earlier and thus increasing the available time for corrective action. Special measurement and data processing techniques are needed to filter out the effects of the planet gears, bearings, input spiral bevel stage, and other components in and around the gearbox. Two sun gears, which were damaged in previous fatigue tests, serve as the focus of this current work. A vibration separation (VS) algorithm, for the non-sequential OH-58C transmission was developed and the resulting signals analyzed. A non-VS based method, which uses only the time synchronously averaged data and takes advantage of the signal/source mapping required for VS is also developed. The FM4 condition indicator is used to compare the two damaged cases with the baseline. Both algorithms were successful in identifying the damage on the sun gear with multiple faults. Sun gear damage was confirmed by the presence of sun mesh groups. Introduction In the last 30 years, researchers have attempted to develop qualitative and quantitative helicopter gear fault detection methods. (Refs. 1–17) Typically, a system is compared to a previous undamaged state over many flight hours and various tools are used to detect when the system deviates from the baseline. The effectiveness of the methodology is governed by it is ability to discriminate between changes due to operating conditions versus those truly due to damage. False alarms are potentially costly since its possible that a helicopter may be unnecessarily removed from service for inspection and/or overhaul. In addition, the system should not be so insensitive that many faults are missed, leading to accidents and possibly the loss of lives. Thus, the number of false alarms, which can be as high as 1 per 1,000 flight hours, must be kept to a minimum. (Ref. 18) In order to increase the probability of a correct diagnosis, it is best to learn as much about the system as possible. This is accomplished by understanding the gear system’s fundamental properties and how 1.) they are affected by damage and 2.) how the damage manifests in measured signals. Presented at the American Helicopter Society 67th Annual Forum, Virginia Beach, VA,May 3-5, 2011. Copyright 2011 by the American Helicopter Society International, Inc. All rights reserved. Testing on the OH58 at NASA Tests were conducted on the 500HP OH-58 helicopter transmission test stand at NASA GRC. Many researchers have used this test stand to advance the field of helicopter HUMS. In 1997, Nachtsheim conducted seeded fault test on the OH-58A transmission on this test stand. (Ref. 19) Seeded damage was introduced using file marks cut on nine alternating teeth on the 19-tooth input spiral bevel pinion gear. The loading was increased monotonically and the tests were stopped when five of the seeded teeth were either fractured or a partially separated. Plots of the data shows increasing spectral activity in the lower frequency range. Lewicki, et al, conducted accelerated fatigue tests while testing advanced lubricants. (Ref. 5). Tests were conducted on the OH-58A and OH-58C transmissions with the goal of producing planet bearing and sun gear fatigue, mast-shaft ball bearing micropitting, and spiral bevel gear scoring. The test matrix used had different test durations (50-100 hours), input torque (100% to 117%) of design maximum, oil pressure (21% to 100%), inlet oil temperature (180o to 275o F), and mast radial loading (0%-100%) of design maximum. The resulting damage components serve as the test components in this current work. Jammu, et al, conducted accelerated fatigue tests on the OH-58A generating various component faults. (Ref. 20)
飞行翻译公司 www.aviation.cn 本文链接地址：Sun Gear Fault Detection on an OH-58C Helicopter Transmission.pdf
Adrian Hood Research Assistant Alfred Gessow Rotorcraft Center Department of Aerospace Engineering University of Maryland College Park, MD 20742-3015 Darryll Pines Dean and Farvardin Professor A. James Clark School of Engineering University of Maryland College Park, MD 20742-3015
Detecting seeded faults on a full-scale helicopter transmission is the focus of this paper. Two methods to isolate the dynamics of an individual sun gear, in an effort to assess its condition, are developed and validated on an OH-58C helicopter transmission’s planetary reduction stage. Planetary indexing is used to geometrically synchronize dynamic measurements with the positions of the meshing teeth. This provides the opportunity for source/signal mapping that can lead to increased sensitivity, allowing faults to be detected earlier and thus increasing the available time for corrective action. Special measurement and data processing techniques are needed to filter out the effects of the planet gears, bearings, input spiral bevel stage, and other components in and around the gearbox. Two sun gears, which were damaged in previous fatigue tests, serve as the focus of this current work. A vibration separation (VS) algorithm, for the non-sequential OH-58C transmission was developed and the resulting signals analyzed. A non-VS based method, which uses only the time synchronously averaged data and takes advantage of the signal/source mapping required for VS is also developed. The FM4 condition indicator is used to compare the two damaged cases with the baseline. Both algorithms were successful in identifying the damage on the sun gear with multiple faults. Sun gear damage was confirmed by the presence of sun mesh groups. Introduction In the last 30 years, researchers have attempted to develop qualitative and quantitative helicopter gear fault detection methods. (Refs. 1–17) Typically, a system is compared to a previous undamaged state over many flight hours and various tools are used to detect when the system deviates from the baseline. The effectiveness of the methodology is governed by it is ability to discriminate between changes due to operating conditions versus those truly due to damage. False alarms are potentially costly since its possible that a helicopter may be unnecessarily removed from service for inspection and/or overhaul. In addition, the system should not be so insensitive that many faults are missed, leading to accidents and possibly the loss of lives. Thus, the number of false alarms, which can be as high as 1 per 1,000 flight hours, must be kept to a minimum. (Ref. 18) In order to increase the probability of a correct diagnosis, it is best to learn as much about the system as possible. This is accomplished by understanding the gear system’s fundamental properties and how 1.) they are affected by damage and 2.) how the damage manifests in measured signals. Presented at the American Helicopter Society 67th Annual Forum, Virginia Beach, VA,May 3-5, 2011. Copyright 2011 by the American Helicopter Society International, Inc. All rights reserved. Testing on the OH58 at NASA Tests were conducted on the 500HP OH-58 helicopter transmission test stand at NASA GRC. Many researchers have used this test stand to advance the field of helicopter HUMS. In 1997, Nachtsheim conducted seeded fault test on the OH-58A transmission on this test stand. (Ref. 19) Seeded damage was introduced using file marks cut on nine alternating teeth on the 19-tooth input spiral bevel pinion gear. The loading was increased monotonically and the tests were stopped when five of the seeded teeth were either fractured or a partially separated. Plots of the data shows increasing spectral activity in the lower frequency range. Lewicki, et al, conducted accelerated fatigue tests while testing advanced lubricants. (Ref. 5). Tests were conducted on the OH-58A and OH-58C transmissions with the goal of producing planet bearing and sun gear fatigue, mast-shaft ball bearing micropitting, and spiral bevel gear scoring. The test matrix used had different test durations (50-100 hours), input torque (100% to 117%) of design maximum, oil pressure (21% to 100%), inlet oil temperature (180o to 275o F), and mast radial loading (0%-100%) of design maximum. The resulting damage components serve as the test components in this current work. Jammu, et al, conducted accelerated fatigue tests on the OH-58A generating various component faults. (Ref. 20)
飞行翻译公司 www.aviation.cn 本文链接地址：Sun Gear Fault Detection on an OH-58C Helicopter Transmission.pdf
自定义标签： 
