System for estimating airspeed of an aircraft based on a drag model

A method of estimating a plurality of airspeed parameters for constantly calculating an airspeed of an aircraft, the method comprising:

• receiving, by a computer, a plurality of operating parameters that each represent an operating condition of the aircraft;
• determining, by the computer, a stability-axis drag coefficient based on the plurality of operating parameters, wherein the stability-axis drag coefficient quantifies a stability-axis drag of the aircraft created during high speed conditions;
• determining, by the computer, a body-axis lift coefficient based on the plurality of operating parameters, wherein the body-axis lift coefficient corresponds to a lift of the aircraft created along a vertical body-axis during low speed conditions;
• determining, by the computer, the aircraft is operating at either the high speed conditions or the low speed conditions based on a flap position of a plurality of flaps of the aircraft and a value of an estimated Mach number;
• in response to determining the aircraft is operating at the low speed conditions, estimating, by the computer, a dynamic pressure based on the body-axis lift coefficient;
• in response to determining the aircraft is operating at the high speed conditions, estimating, by the computer, the dynamic pressure based on stability-axis drag coefficient;
• and
• estimating, by the computer, the plurality of airspeed parameters based on the dynamic pressure.

A system for estimating a plurality of airspeed parameters for constantly calculating an airspeed of an aircraft, the system comprising:

• one or more processors;
• and
• a memory coupled to the one or more processors, the memory storing data comprising a database and program code that, when executed by the one or more processors, causes the system to:
• receive a plurality of operating parameters that each represent an operating condition of the aircraft;
• determine a stability-axis drag coefficient based on the plurality of operating parameters, wherein the stability-axis drag coefficient quantifies a stability-axis drag of the aircraft created during high speed conditions;
• determine a body-axis lift coefficient based on the plurality of operating parameters, wherein the body-axis lift coefficient corresponds to a lift of the aircraft created along a vertical body-axis during low speed conditions;
• estimate a dynamic pressure based on one of the stability-axis drag coefficient and the body-axis lift coefficient;
• and
• estimate the plurality of airspeed parameters based on the dynamic pressure, wherein the stability-axis drag coefficient is determined as:
• CD=CD1(α,MMOL)CD2(Flap,MMOL)CD3(Gear,MMOL)+CD4(Spoiler,α,MMOL)CD5(stabilizer,α,MMOL)+CD6(rudder,β,MMDL)
• wherein Flap represents the flap position indicative of a position of trailing edge flaps of wings, Gear represents the landing gear position, Spoiler represents a plurality of spoiler positions, Stabilizer represents the stabilizer surface position, rudder represents the rudder position, and components CD1-CD6 are each determined based on respective lookup tables saved in the memory.

A method of estimating a plurality of airspeed parameters for constantly calculating an airspeed of an aircraft, the method comprising:

• receiving, by a computer, a plurality of operating parameters that each represent an operating condition of the aircraft;
• determining, by the computer, a stability-axis drag coefficient based on the plurality of operating parameters, wherein the stability-axis drag coefficient quantifies a stability-axis drag of the aircraft created during high speed conditions;
• determining, by the computer, a body-axis lift coefficient based on the plurality of operating parameters, wherein the body-axis lift coefficient corresponds to a lift of the aircraft created along a vertical body-axis during low speed conditions;
• estimating, by the computer, a dynamic pressure based on one of the stability-axis drag coefficient and the body-axis lift coefficient;
• and
• estimating, by the computer, the plurality of airspeed parameters based on the dynamic pressure by:
• CD=CD1(α,MMDL)CD2(Flap,MMOL)+CD3(Gear,MMDL)+CD4(Spoiler,α,MMDL)CD5(stabilizer,α,MMOL)+CD6(rudder,β,MMDL)
• wherein Flap represents the flap position indicative of a position of trailing edge flaps of wings, Gear represents the landing gear position, Spoiler represents the plurality of spoiler positions, Stabilizer represents the stabilizer surface position, rudder represents the rudder position, and components CD1-CD6 are each determined based on respective lookup tables saved in a memory of the computer.