"INTRODUCTION This Data Item is one of a series concerned with the correction of errors inherent in anemometric sensors and in the registered (indicated) values of the parameters. Two of the Data Items@ Reference 8 and this work@ give methods of analysis by which these corrected parameter values may be used to derive true values of the prime data required for airworthiness and performance evaluation and for safe and efficient operation of the aircraft. The use of the prime data is especially important for air data systems controlling an air-breathing propulsion unit. These prime data are Mach number@ M@ pressure height@ Hp@ true airspeed@ V@ and ambient air temperature@ Ta. Data Item No. 83029@ Reference 8@ is concerned with speeds up to those giving a stagnation temperature of 1000 K. This limit permits speeds up to Mgt; 4@ at appropriate heights@ to be considered and gives an interface with the present Item which is concerned with real gas effects (Zgt; 1.0). Reference 8@ on the other hand@ assumes an ideal gas state in the stagnation air or@ at the higher temperatures@ caloric imperfections. Figure 1 displays the scope of the methods presented here: speeds between M> 4 and M= 10and heights up to 65 km. The implications of the ""advisory"" limits@ M = 10 and Hp=65km are discussed in Appendix A. The lower limits of height are those for the data presented in this Item@ and are considered to be adequate for foreseeable applications. However@ if required@ the source data in References 2 and 3 give information down to sea level. The maximum height at which the data may be applied is dependent on vehicle geometry and could be as low as 37 km@ see Section A2. The user of this Data Item is recommended to refer to Data Item No. 93020@ Reference 14@ for a method of calculating the value of static pressure@p2 @ in preference to attempting to derive it from pressure information supplied by anemometric data sensors. Section 3 discusses the assumptions and restrictions which apply. Section 4 derives the conditions of state for equilibrium air behind a normal shock. Section 5 uses conservation equations@ the Rankine-Hugoniot relationships@ and the data derived in Section 4 to obtain the required prime parameters@ M@Hp@V and Ta. Section 6 reviews the accuracies of the processes dealt with in Sections 4 and 5. Section 7 summarises the calculation procedures involved in using the method of Sections 4 and 5 and includes the corrections required for non-steady flight. Section 9 presents an example of the use of the method. Appendix A is concerned with the applicability and the limitations of the Item. Appendix B gives the derivation of corrections required to some parameters for non-steady flight."
ESDU 88025 C-1994 history
1994ESDU 88025 C-1994 DERIVATION OF PRIMARY AIR-DATA PARAMETERS FOR HYPERSONIC FLIGHT