Flight Instruments, Failures, & Emergencies Flashcards
What instruments operate on the Pitot-Static System?
- Airspeed Indicator
- Altimeter
- Vertical Speed Indicator
What instrument relies on the Pitot tube?
The Airspeed Indicator
How does an Altimeter work?
- An Altimeter senses the difference between the pressure set to 29.92 in HG in the aneroid wafer and the outside air pressure fed into the chamber surrounding the wafer.
- The wafer is attached to a series of gears and linkages to the needle on the instruments display
What errors are associated with the Altimeter?
- Non-Standard temperature errors
- Non-Standard pressure errors
Explain the temperature errors associated with the Altimeter.
Warmer than standard temps
- Warm air is less dense
- Pressure levels are higher for a given altitude than they would be at standard temps
- True Altitude (MSL) is higher than Indicated
Colder than standard temps
- The air pressure is lowered
- Pressure levels are lower than they would be at standard temps
- True Altitude MSL is lower than Indicated.
- This is dangerous
Extreme Cold Temps
- It may be necessary to apply a cold temperature correction to the Altimeter to provide additional terrain/obstacle clearance
***REMEMBER: Hot to cold, look out below
What is the correlation between air Temperature and air Pressure?
They are conversely related
- High Pressure = Temp must also increase
- Low Pressure = Temp must also decrease
Explain the Pressure errors associated with the Altimeter.
If the Altimeter setting is not adjusted when flying between different areas of pressure, the reading will be incorrect
High to Low Pressure
- True Altitude (MSL) will be lower than Indicated
- Dangerous
Low to High Pressure
- True Altitude (MSL) will be higher than Indicated
For IFR flight, what is the maximum allowable error for an Altimeter?
The Altimeter must read within +- 75ft of field elevation
What is Indicated Altitude?
The Altitude as read from the Altimeter
What is True Altitude?
The height above mean sea level (MSL)
Charted in MSL
- Airport elevation
- Airspace heights
- Terrain
- Obstacles
What is Absolute Altitude?
Height above the ground (AGL)
Charted in AGL
- MDA/DA in (parentheses) on an IAPs minimums
What is Pressure Altitude?
Our Altitude corrected for non-standard Pressure
- You can find it by setting the altimeter to 29.92 on the ground
- Used to compute things like Density Altitude and True Airspeed
What is Density Altitude?
Pressure Altitude corrected for non-standard Temperature
- This is the altitude the aircraft will feel like its performing at
- A high Density Altitude means that your aircrafts performance will be negatively effected (engine, climb, stall recovery)
Does adjusting your Altimeter setting have any effect on the altitude displayed to ATC?
No
How does the Airspeed Indicator work?
The airspeed indicator measures the difference between RAM air pressure from the Pitot Tube and Static air pressure from the Static ports
- Static Pressure is sent to the aneroid wafer inside the Airspeed indicator
- Total Pressure enters the Pitot Tube and is sent to the chamber surrounding the aneroid wafer
What are some limitations of the Airspeed Indicator?
- Position Error - It must have smooth airflow entering the Pitot-Static System
- Clogging - It is subject to being clogged with ice or other debris
- Density Error - Changes in Altitude and Temperature are not compensated for
- Compressibility Error - Caused by air packing into the Pitot Tube at high airspeeds. Results in higher than actual indications. Usually occurs above 180 kts.
What are the 4 kinds of airspeed?
- Indicated - As read from the Airspeed Indicator
- Calibrated Airspeed - Indicated Airspeed corrected for instrument and position errors
- Equivalent Airspeed - Calibrated Airspeed corrected for Compressibility Error during nonstandard conditions. As airspeed and Pressure Altitude increase CAS becomes higher than it should be and requires a correction.
- True Airspeed - This is Calibrated Air speed corrected for both non-standard pressure and temperature.
What is True Airspeed?
True airspeed is our actual speed as we move through the air in non-standard conditions. As we gain altitude the air becomes Less Dense and the Pitot-Tube needs more air to produce the same indicated airspeed. So True Airspeed would correct for this.
How does the Vertical Speed Indicator work?
The VSI measures the rate at which pressure changes as you gain or lose altitude to determine a FPM rate of altitude change.
- Static pressure is sent to an aneroid wafer and also to a chamber surrounding the wafer.
- The aneroid wafer receives instant pressure readings while the chamber has a calibrated leak that SLOWLY equalizes pressure.
- So the VSI measures the change between current pressure and the pressure at the original altitude, when descending or ascending.
What will happen to your airspeed indicator if the both the Pitot-Tube and the Pitot-Drain hole are clogged?
The airspeed indicator is only receiving Static Pressure from the Static port and will now act like an Altimeter.
Will show an increase in airspeed as you climb and a decrease in airspeed as you descend
*Dangerous because if you do not notice the malfunction and try and slow down the aircraft or speed up to much based on the false indications you could overspeed or stall the aircraft
Traditionally, what instruments contained Gyroscopes?
- Attitude Indicator
- Turn Coordinator
- Heading Indicator
Traditionally, how are Gyroscopic instruments powered?
Most commonly they are powered by vacuum pump or electricity
How does a Vacuum Powered Gyroscope work?
A stream of air is pumped past the vanes of a rotor to spin the gyro
What are the two principles on which a Gyroscope funtions?
Rigidity in Space - A spinning plane resists tilting
(the attitude and heading instruments operate on this principle)
Gyroscopic Precession - Force applied to a point on a spilling wheel is not felt at that point, but in 90 degrees of the direction of its rotation.
(the turn coordinator operates on this principle)
