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The Sonic Altimeter for AircraftDiscussed here are results already achieved with sonic altimeters in light of the theoretical possibilities of such instruments. From the information gained in this investigation, a procedure is outlined to determine whether or not a further development program is justified by the value of the sonic altimeter as an aircraft instrument. The information available in the literature is reviewed and condensed into a summary of sonic altimeter developments. Various methods of receiving the echo and timing the interval between the signal and the echo are considered. A theoretical discussion is given of sonic altimeter errors due to uncertainties in timing, variations in sound velocity, aircraft speed, location of the sending and receiving units, and inclinations of the flight path with respect to the ground surface. Plots are included which summarize the results in each case. An analysis is given of the effect of an inclined flight path on the frequency of the echo. A brief study of the acoustical phases of the sonic altimeter problem is carried through. The results of this analysis are used to predict approximately the maximum operating altitudes of a reasonably designed sonic altimeter under very good and very bad conditions. A final comparison is made between the estimated and experimental maximum operating altitudes which shows good agreement where quantitative information is available.
Document ID
19930081403
Acquisition Source
Legacy CDMS
Document Type
Other
Authors
Draper, C S
(Massachusetts Institute of Technology, Cambridge , Mass)
Date Acquired
September 6, 2013
Publication Date
August 1, 1937
Report/Patent Number
NACA-TN-611
Accession Number
93R10693
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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