Engineering topics
Publications and source records attributed to Martin, R. L..
Fluid dynamic aspects of the Antarctic ozone hole phenomena are studied. Data collected by the ER-2 aircraft as part of the Airborne Antarctic Ozone Experiment (AAOE) are used to calculate the potential vorticity distribution on potential temperature surfaces. Most of the ER-2 flights show a monotonic decrease in potential vorticity and nitrous oxide toward the pole on isentropic surfaces.
Remarkable domination of the summer Southern Hemisphere (SH) circulation by medium-scale features (zonal waves 4-7) has been reported. More recently, it has been shown that these features derive their energy from baroclinic instabilities of the mean state. As one aspect of attempting to further explain the unusual spectral peak and phase-time continuity of the SH waves, the same microwave satellite instrument is used to compare characteristics of medium-scale lower stratospheric temperature waves in the Northern Hemisphere (NH) and SH summertimes. Data from the Tiros-N Microwave Sounding Unit from August 1979 are analyzed here and compared with previous analyses for January 1979 reported by Yu et al. (1983) and others. The interhemispheric comparison reveals that summertime medium-scale waves in the NH do not exhibit the striking phase-time continuity of their SH summer counterparts. In addition, winter NH medium-scale waves are also found to have less phase-time continuity than those in the SH winter. The reason for the interhemispheric difference in maintenance of the medium-scale waves, especially in summertime, remains to be explained.
Flight loads on the 747 propulsion system and resulting JT9D blade to outer airseal running clearances during representative acceptance flight and revenue flight sequences were measured. The resulting rub induced clearance changes, and engine performance changes were then analyzed to validate and refine the JT9D-7A short term performance deterioration model.
Past diagnostics studies revealed the primary causes of performance deterioration of high by-pass turbofan engines to be flight loads, erosion, and thermal distortion. The various types of airplane loads that are imposed on the engine throughout the lifetime of an airplane are examined. These include flight loads from gusts and maneuvers and ground loads from takeoff, landing, and taxi conditions. Clarification is made in definitions of the airframer's limit and ultimate design loads and the engine manufacturer's operating design loads. Finally, the influence of these loads on the propulsion system structures is discussed.
The JT9D jet engine exhibits a TSFC loss of about 1 percent in the initial 50 flight cycles of a new engine. These early losses are caused by seal-wear induced opening of running clearances in the engine gas path. The causes of this seal wear have been identified as flight induced loads which deflect the engine cases and rotors, causing the rotating blades to rub against the seal surfaces, producing permanent clearance changes. The real level of flight loads encountered during airplane acceptance testing and revenue service and the engine's response in the dynamic flight environment were investigated. The feasibility of direct measurement of these flight loads and their effects by concurrent measurement of 747/JT9D propulsion system aerodynamic and inertia loads and the critical engine clearance and performance changes during 747 flight and ground operations was evaluated. A number of technical options were examined in relation to the total estimated program cost to facilitate selection of the most cost effective option. It is concluded that a flight test program meeting the overall objective of determining the levels of aerodynamic and inertia load levels to which the engine is exposed during the initial flight acceptance test and normal flight maneuvers is feasible and desirable. A specific recommended flight test program, based on the evaluation of cost effectiveness, is defined.
Electromagnetic compatibility and radio frequency interference of aircraft radio antennas
Boson production in p-p collisions at 12.3 Bev/c