Remote Instrumentation Best For Jet Planes.--Instruments for jetplanes of the future will be of the electrical remote-reading type for reasons of safety and ease of installation, in the opinion of C. A. Edman, of General Electric's Meter and Instrument Division.
Speaking at a recent ASME meeting on the subject of."Instrumentation for Jet-Propelled Airplanes," Mr. Edman explained that the low vibration inherent in jet engines permits the use of more delicate primary detectors than does the reciprocating engine. He said that d-c selsyn systemsusingmovable contacts have already proved successful in a number of jet plane installations.
"Because of theirsize, however, these d-c selsyn systems will doubtless be superseded by the inherently smaller a-c types as soon as the proper ranges are developed in the latter systems," Edmansaid.
Remote-reading instruments are virtually a "must" for jet planes, according to Mr. Edman, because of the need for quick disassembly of the engine from the airframe and the desirability of keeping high-pressure fuel lines outside the cockpit.
The jet plane's gas-turbine engine needs only five basic indicating instruments, as compared with seven required by the conventional reciprocating engine, Ednian said. These are the tachometer, tailpipe-temperature indicator, bearing-temperature gage, oil-pressure gage, and fuel pressure gage. However, he pointed out, these instruments will need considerable improvement to meet the special conditions of jet engine indication. The most urgent needs are in tailpipipe-temperature and bearing-temperature indication. Instruments for these purposes will require improved resistance bulbs to withstand high temperatures and corrosive atmosphere.
R. H. O.