Chapter 5 - Machmeter Flashcards
An aircraft cruising at M.84 is?
Maintaining a TAS which is 84% of the speed of sound at the level at which the aircraft is flying.
What is Mach Number?
The ratio of true airspeed to local speed of sound.
Mach Number = TAS / Local Speed of Sound
What is the speed of sound a function of?
Temperature - Lower the temperature the lower the speed of sound.
How do you find the TAS from Mach No and Temperature?
Mach number = TAS / Local Speed of Sound
TAS = Mach Number x Local Speed of Sound
TAS = Mach Number x 38.94 x (Square root) Temperature (Kelvin)
A Machmeter is made up of?
An Altitude capsule and an Airspeed Capsule
Airspeed capsule to measure - Pitot and Static
Altimeter Capsule to measure - Static
What results in an increase of Mach number?
Increase in airspeed (IAS / CAS / RAS) or increase in altitude will result in an increase in Mach Number.
What errors is the Mach meter subject too?
Instrument and Pressure (Position/Manoeuvre) Error.
What is the relationship between Mach Number and CAS?
Mach Number depends on the ratio of Dynamic Pressure to Static Pressure. When climbing at constant Mach No dynamic pressure must reduce in order to remain at a fixed ratio to static. Reducing Dynamic leads to reducing IAS and CAS.
What is the relationship between Mach No and TAS?
TAS at a given mach number depends on temperature. When climbing below the tropopause at constant Mach No, temperature generally reduces and so the local speed of sound and TAS reduces.
Detail ECTM
Arrow Relationship Between EAS, CAS, TAS and Mach
E=EAS, C=CAS, T=TAS and M=Mach
If climbing use -ECTM+
If one of the speeds is kept constant, then the speeds to the right of it are increasing and to the left decreasing.
If an inversion is involved change over TAS and Mach.
If an isothermal layer is involved then TAS and Mach are coincident with each other.
Conversely using the same laws in a descent use +ECTM-
The calibration of the Machmeter assumes?
No ISA conditions
