Test Stand &
Test Cell Upgrade
Engineers consider a variety of factors when designing jet engine test cell instrumentation systems, including engine control, safety and performance.
T700 test cell throttle control
Honeywell T55 electronic engine log and data reduction system (EELDRS) data reporting
T700 Engine History Counter (EHC) test system
T700 Electrical Control Unit (ECU) test system
Helicopter engines make up a large portion of Corpus Christi Army Depot’s workload. The engines themselves are made up of subsystems that are individually tested and then brought together as a complete engine and tested as an engine.
Corpus Christi Army Depot (CCAD) has several test stands used to test these engine subsystems. These test stands contain obsolete instruments. CCAD is accepting new workload involving General Electric T700-701D model and Honeywell T55-714A model engines. The test stand fixtures need to be able to run the newer engines and still be compatible with the older engines. The fixtures currently being used are old and not reliable and need to be redesigned and manufactured. The engine manufacturer supplies software to CCAD that is used to certify the rebuilt product will meet the original performance specifications given by the manufacture. The newer programs have added features and newer requirements that require an update to the interface between them and the current systems at CCAD. A number of different test stands and test cells have been upgraded over time. Some are described below.
Electronic Control Unit (ECU) Function Generator and Printer Upgrades
Three test stands were upgraded for this task. The out-of-production Wavetek 278 function generator was replaced with a modern Agilent 33220A function generator. The old Epson dot matrix printer was replaced by a HP 2430n LaserJet printer. Drivers for both were updated so the existing test stand software would be compatible with the new devices. All three test stands were upgraded successfully; however, preexisting issues with the Np ramp rate tests were identified that prevented the two Sytronics test systems from complying with testing as defined by the DMWR.
Digital Electronic Control Unit (DECU) Function Generator and Printer Replacement
One test stand was upgraded for this task. The out of production Wavetek 278 function generator was replaced with a modern Agilent 33220A function generator. The old Epson dot matrix printer was replaced by an HP 2430n LaserJet printer. Drivers for both were updated so the existing test stand software would be compatible with the new devices.
Engine History Recorder (EHR) Function Generator and Printer Replacement
Two test stands were upgraded for this task. The out-of-production Wavetek 278 function generator was replaced with a modern Agilent 33220A function generator. The old Epson dot matrix printer was replaced by an HP 2430n LaserJet printer. Drivers for both were updated so the existing test stand software would be compatible with the new devices.
T700 Test Cell Throttle Control Replacement
Southwest Research Institute (SwRI) replaced an expensive throttle controller that was breaking fairly frequently with a design almost entirely made of commercial off-the-shelf (COTS) parts. Feedback for the legacy system from the operators and engineers was used in creating the new design. The new design is lighter, easier to attach, and has much higher reliability. In addition to replacing the hardware, the software drivers were updated so that the existing test cell software would be compatible with the new hardware.
T55 Engine Test Cell Software Investigation
The T55 engine test cell software had a pre-existing infrequent bug that would reverse the desired direction of the throttle controller after a calibration sequence was performed. After investigating it was believed that the problem occurred when the stepper motor controller count cycles went beyond its maximum of 999,999 and started over again at 0. To alleviate this problem, the code was modified to ensure that the stepper motor controller count is reset to 400,000 every time the system is calibrated. The problem has not been reported since the software was updated.
ATETS/Daytronics Machine Interface Debugging
A computer in test cell 6 runs Daytronics emulator software and occasionally locks up and must be restarted. SwRI investigation determined that the emulator was using a huge portion of the computer's resources (95% of the CPU’s clock cycles). The emulator code was modified and with the modifications, the Daytronics emulator now uses less than 5% of the clock cycles. The CPU clock cycle usage was divided by 19 which is a huge improvement for this system. The lock-up problem has not been reported since this modification.
General Electric PC Data Reduction Program (GEPCDRP) Software Integration
General Electric (GE) released a new data reduction program to replace a prior version. All previous versions ran on a UNIX system inside the test cell, but the new program was made for Windows 98 through XP. SwRI wrote software to automatically run the program when a new engine run is completed and after successful data reduction move the files to a desired location.
Honeywell T55 Electronic Engine Log and Data Reduction System (EELDRS) Data Reporting
SwRI created an SQL program that allows approved CCAD users to access T55 EELDRS data reports from a web browser. Any time a new engine is run in test cell 5 a file of data is created. The SQL program automatically takes the reduced data and generates a report identical to what CCAD is used to. The big difference is that these reports are easily viewable by any person that has been granted access. The program also produces trend data plots for data taken from a group of engines.
Re-design of Test Cell APU Throttle Controller
SwRI created a remote electronics throttle control system to vary the APU throttle screw while the unit is under test. This system helped to provide CCAD with a new capability to pursue new business in testing APUs while providing the safety of not having an operator in the cell while the engine is running.
T700 DEC and EHC Production Expansion
The Corpus Christi Army Depot (CCAD) desired to expand their depot test capability for the T700 Digital Electronic Control (DEC) to increase production volume and achieve a higher throughput. The original T700 DEC test system already in operation at CCAD was designed, built, and installed by General Electric Aircraft Engines (GEAE) during the period of 1990-1992. In addition to the ability to test T700 DECs, the existing T700 DEC test system has the capability to test T700 Engine History Counters (EHC).
SwRI designed and built two separate test systems, a T700 Digital Electronic Control (DEC) test stand and a T700 EHC Test Stand, for use by CCAD. This allows for testing of the T700 DECs and EHCs in parallel, thus saving time and improving throughput. The basic design of the test stands was based on the design of General Electric T700 DEC Test Stand but incorporated changes that eliminated obsolete equipment and further improved the reliability and ergonomics of the test system.
ECU Test Console Upgrades and Rehosting
SwRI modified the T700 Electrical Control Unit (ECU) test console originally produced by General Electric (GE). SwRI replaced the Hewlett-Packard (HP) computer, which utilized a Unix operating system and Rocky Mountain BASIC software application program, with a Kontron rack-mountable computer with a Windows® XP® operating system and TransEra HT-BASIC software application program. The T700 ECU test software was modified to operating in the new software application program environment. Automated test procedures (ATP) were performed on various ECU families to ensure the hardware and software modifications did not adversely affect testing of the unit under test (UUT).
aircraft engine performance • test stand upgrade • test stand update • electronic control unit • ECU • digital electronic control unit • DECU • engine history recorder • EHR • test cell throttle control