Cockpit Flashcards
Evolution of cockpits
- With the introduction of early flight instruments, the pilots were able to determine their position along the desired route and assess the situation of the aircraft more efficiently and accurately.
- However, more instruments can lead to a higher complexity and may require more people to monitor them.
- Additional instruments were replaced with digital systems to reduce the workload and number of persons in the cockpit: Starting with two pilots, a flight engineer, a navigator and a radio operator, some crew members were replaced with automated systems, leading to the modern 2 pilot cockpit.
- With the introduction of digital displays and digital instruments, information could be displayed on different pages, prioritizing messages and warnings.
- The development to these new systems, however, lead to new problems with the design of the user interface and the usability of the overall system
Change of the tasks performed by pilots:
Transition from flying the aircraft to supervising aircraft systems
Flight envelope, flight envelope boundaries: Which ones exist?
Ma-h diagram -Stall limit n = 1 -Thrust limit T = D -Buffeting -Dynamic pressure limit -Temperature limit (MIL) V-n Diagram -Structural failure area -Structural damage area -stall speed 1g/ -1g(inverted)
Constrains issued by air traffic control that have to be adhered to:
Altitude, heading, course, vertical speed, navigation along pre-defined routes
which additional information can be taken into account:
- Weather: Wind, turbulences
- Traffic situation
- Altitude prediction
which parameters can be optimized
fuel consumption, time, noise and costs
Difference between classical flight instruments and state-of-the-art integrated systems
classical layout: 1 Sensor -> 1 instrument
state of the art integrated systems: sensors -> flight computer -> instruments
Layou tof the flight instruments
which parameter are shown
basic T; airspeed, altitude, artifical horizon, kompass/ils
Air data system: available sensors. What is directly measured?
Instruments using static and total air pressure:
Altimeter (ALT), Vertical speed indicator (VSI), Airspeed Indicator (ASI), Machmeter
Gyroscopic instruments:
Compass, Turn indicator / turn coordinator, Attitude Indicator, Directional Gyro, Slaved Compass
Radio instruments:
Radio altimeter
Modern digital instruments:
Primary Flight Display (PFD), Navigation Display (ND)
Categories of instruments
Instruments using static and total air pressure:
Altimeter (ALT), Vertical speed indicator (VSI), Airspeed Indicator (ASI), Machmeter
Gyroscopic instruments:
Compass, Turn indicator / turn coordinator, Attitude Indicator, Directional Gyro, Slaved Compass
Radio instruments:
Radio altimeter
Modern digital instruments:
Primary Flight Display (PFD), Navigation Display (ND)
Principle of temperature measurement, definition of SAT and TAT
Static air temperature (SAT or 𝑻𝒔):
The temperature of the undisturbed air through which the aircraft is about to fly (very hard to measure);
Total air temperature (TAT or 𝑻𝒕):
The maximum air temperature which can be attained by 100% conversion of the kinetic energy of the flight (impossible to measure, because the complete energy conversion is not possible);
Air data system: available sensors.What is directly measured?
- Pitot tube
- Static pressure sensor
- Angle of sideslip sensor
- Angle of attack sensor
- Total air temperature (TAT) sensor
- Static air temperature (SAT) sensor
Sources of error in the temperature measurement
•THERMAL CONDUCTION
A condition error may occur when the fuselage of the aircraft is at a different temperature than the sensor. This usually occurs on the ground during taxi conditions on hot summer days or in the winter.
•THERMAL RADIATION
When the total temperature being measured is relatively high, heat is radiated from the sensing element, resulting in a reduced indication of temperature.
•TIME CONSTANT
An instantaneous response by a sensor to a temperature change is impossible due to the heat capacity of the sensor parts and surrounding structure. This results in an indicated temperature/time transient. The time constant is a performance parameter typically used to describe this temperature/time transient.
•AIRFLOW DIRECTION
When the airstream approaches the inlet of a total air temperature sensor from a direction other than directly forward, errors may be introduced.
•SELF-HEATING
Total air temperature sensors which use resistance elements require that a small electrical current pass through the sensing element. This current causes a self-heating effect (I2R -Joule heating) which results in a small increase in the measured temperature.
•DEICING HEAT ERROR
For total temperature sensors with deicing heaters, application of the deicing heat can cause 𝑇𝑚to increase at low airspeeds. Basically, this effect is a conduction error, internal to the sensor, caused by the close proximity of heated portions of the sensor housing to the sensing element.
•AERODYNAMIC DRAG
Although the drag is not involved with the accuracy of total air temperature sensors, it can be important in trade-offs with other performance parameters. For example, deiced total air temperature sensors usually exhibit a higher drag than non-deiced sensors. The drag is influenced by the shape and size of the sensor and varies with the aircraft speed and altitude
Principles of altitude measurement
- The altimeter is a sealed pressure container, consisting of pressure capsules and a mechanical system. To display the altitude, the container is connected to the static pressure.
- Difference between static air pressure in the container and pressure in the capsules causes an expansion or contraction of the capsules.
- The lever and a (in the image simplified) mechanical system translates the movement into a rotation of the different pointers
formel Geopotential height
𝐻𝐺=𝑟𝐸⋅ℎ/𝑟𝐸+ℎ
