A Continuing Study of Altitude Determination Deficiencies of the Service Aircraft Instrumentation Package (SAIP)
Abstract
After correcting test equipment used in a previous study of the SAIP for an ambiguous grounding requirement, research was continued on aerodynamic factors affecting SAIP altitude measurement. Existing equations for incompressible flow over a cylinder and a sphere were used to model the static- pressure probe located on the front of the SAID pod and an algorithm was derived for the computation of the pressure coefficient, Cp. Our low-speed wind tunnel data show an overpressure at the static pressure ports when the angle of attack (phi) is less than 14 deg. The five-inch diameter body of the SAIP, located aft of the static pressure probe, is responsible for creating a stagnation-like region at the front of the SAIP probe which envelops the static-port location. Calculation of the altitude error (delta zeta) using the model for Cp, corrected for compressibility, is within + or - 15% of the error observed in flight a Mach 0.60. Improvements in the compressibility correction as well as analyses using an aero-panel method are suggested before sufficiently reliable fixes to the SAIP can be proposed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1991
- Accession Number
- ADA245952
Entities
People
- Robert J. Russell
Organizations
- Naval Postgraduate School