Flight Instruments Part 3/3 Flashcards
What does a heading indicator do?
Designed to facilitate the use of a magnetic compass. This is because errors in the magnetic compass make straight flight and precision turns to headings difficult to accomplish, especially in turbulent air.
Describe an error with the heading indicator
Because of the precession caused by friction, the heading indicator creeps/drifts from a heading from which it is set.
Describe another error with the heading indicatorkee
The gyro is oriented in space and the earth rotates in space at a rate of 15degrees in one hour, thus discounting precession caused by friction, the heading indicator may indicate as much as a 15deg error per every hour of operation. Some heading indicators referred to as horizontal situation indicators HSI receive a magnetic North reference from a magnetic slating transmitter (magnetometer) and generally need no adjustment.
What has enabled electronic flight systems to replace free-spinning gyros with solid state laser systems that are capable of flight at any attitude without tumbling.
Attitude and Heading Reference Systems (AHRS) sends attitude information to the PFD in order to generate the pitch and bank information of the attitude indicator
What is an AHRS?
Attitude and Heading Reference System
How is the heading information derived in an AHRS?
Derived from the magnetometer, which senses the earth’s lines of magnetic flux. This info is processed and sent out to the VFD to generate the heading display
Two basic characteristics of earth’s lines of magnetic field flux
- A magnet aligns with them
2. An electrical current is induced or generated in any wire crossed by them
What drive’s slave gyros?
Flux Gate Compass System uses current induction on 3 coils connected to smaller coils in a sychro on the instrument case. The synchro rotates the dial of a Radial Magnetic Indicator (RMI) or an Pictorial Navigation Indicator (HSI)
Describe two different types of Remote Indicating Compasses
- The Pictorial Navigation Indicator (referred to as an HSI)
- Slating Control and Compensator Unit (you have the option of selecting the slave gyro or the free gyro mode)
What does the slaving meter button do on a Slating Control and Compensator Unit
It indicates the difference between the displayed heading and the magnetic heading
What is an RMI?
Radio Magnetic Indicator. It combines indications from a magnetic compass, VOR, and ADF (automatic direction finder) into one instrument
Describe how an RMI works
The compass card is driven by signals from the flux valve and the two pointers are driven by an automatic direction finder (ADF) and a very high frequency (VHF) omni-directional radio range (VOR).
In arial navigation, describe the difference between true and magnetic directions is called:
Variations
In arial navigation, describe the angular difference in surveying and land navigation
Declination
What is the Agonic line?
Along this line, the two poles are aligned and there is no variation
