Aircraft Instruments: Aircraft Instruments Pitot – Static System: Pitot – Static System Airspeed Indicator: Airspeed Indicator Airspeed Indicator Symbology: Airspeed Indicator Symbology White Arc – Flap operating Range
Green Arc – Normal Operations
Yellow Arc – Caution Area (Only use in smooth air)
Red Line – Never Exceed Speed Aircraft Airspeeds: Aircraft Airspeeds Vso – Stall speed in landing configuration
Vs – Stall speed in clean (flaps up) configuration
Vy – Climb speed for the max amount of height v. time
Vx- Climb speed for the max amount of height for distance
Vfe- Flap Extension speed: Flaps should not be used above this speed
Va – Design maneuvering/rough air speed: Speed at which abrupt full control inputs can be used without risking structural damage. Should never be exceeded in rough air. Changes with weight
Vno – Max structural Cruise speed
Vne – Never Exceed Speed
Types of Airspeeds: Types of Airspeeds Calibrated
Speed corrected for installation and instrument errors.
At high angle of attack, the pitot tube does not point straight into the relative wind, this tends to make the airspeed indicate lower than normal at low airspeeds.
Not usually a problem in cruise, usually we only worry about calibrate airspeed when we are converting to true airspeed.
The actual speed of your airplane is moving through undisturbed air.
On a standard day, Calibrated airspeed will be equal to TAS.
As density altitude increases, true airspeed increases for a given CAS or amount of power.
TAS can be calculated by using CAS with temperature and pressure on your E6B
Calibrated airspeed corrected for adiabatic compressible flow at a particular altitude.
Above 200 kts and 20,000 feet air compresses in front the pitot tube causing abnormally high airspeeds. Many flight computers are designed to compensate.
Airspeed Indicator: Airspeed Indicator Uses ram air from the pitot tube as well as static air.
Ram air pushes against a diaphragm inside the airspeed indicator, which will then be able to expand or contract accordingly. This movement of the diaphragm is then translated into needle movement. Airspeed Indicator: Airspeed Indicator If the Pitot tube is blocked and the drain is open, speed will go to zero.
If the Pitot tube is blocked and the drain is open, it will act as an altimeter.
If the the Static vent is blocked, the airspeed will read higher than it should above altitude where it became blocked and lower than it should below.
If all three all blocked, the needle will freeze. Questions?: Questions? How does the airspeed indicator compute indicated airspeed?
How will we know if we have a blocked pitot tube?
What would you do?
Will you need to compute your equivalent airspeed for flight?
Altimeter: Altimeter Altimeter: Altimeter Static Input Only
Manufacturer seals the aneroid wafer(s) at a specific pressure. As the static pressure fills in the area around these sealed wafers, they will be able to contract or expand accordingly Altimeter Operation: Altimeter Operation Types of Altitude: Types of Altitude Indicated
What you read on the altimeter when it is correctly adjusted to show approximate height above mean sea level
Indicated altitude corrected to compensate for instrument error
Displayed when altimeter is set to standard sea level (29.92).
Vertical distance above the standard datum plane
Pressure altitude corrected for non – standard temperature
Used to determine aircraft performance, when high (temp above standard), performance will be worse.
Actual height above mean sea level
Actual height of aircraft above the earths surface. Altimeter Errors: Altimeter Errors Make sure you update your altimeter setting as often as possible (or at least every 100 miles)
If you fly to an area with a lower altimeter setting, without resetting your altimeter, you may fly at a lower altitude than you had intended.
“High to low, look out below”
On warm days, true altitude is higher than indicated. Aircraft true altitude is lower than indicated in colder air.
Altimeter will freeze at the altitude the blockage occured High to Low, Look out Below!: High to Low, Look out Below! Questions?: Questions? How does the altimeter work?
What altitude is displayed on a sectional chart?
If I fly from an area of a pressure setting of 29.92 to an area where it was 30.00, would I be likely to be flying above or below where I should?
How would you know if the static port was blocked?
If you then turned on alternate air, what kind of indication would you generally expect?
Vertical Speed Indicator: Vertical Speed Indicator Rate of climb and descent
Trend will show immediate indication of an increase in the airplanes rate of climb or descent
Rate shows a stabilized change in altitude Vertical Speed Indicator: Vertical Speed Indicator Static air enters both the diaphragm and the area around it. However, the air in the diaphragm is constantly updated while the air outside of it is very slowly allowed to escape through a calibrated leak. The instrument measures the difference in these two pressures (the air where you where v. where you are)
Vertical Speed Indicator Errors: Vertical Speed Indicator Errors Blocked Static
Lags: should not be relied upon to give instantaneous information
Don’t “chase the needle” Pitot – Static Summary: Pitot – Static Summary While the Altimeter, VSI and airspeed indicator all use Static air, only the airspeed indicator uses Pitot
If you notice all of your pitot static instruments are giving conflicting information, try turning using the alternate air source
If only your airspeed indicator is not working properly, try turning on pitot heat
Gyro Instruments: Gyro Instruments Which instruments are Gyroscopic?: Which instruments are Gyroscopic?
Which instrument(s) are powered by the vacuum system?
Which are powered by the electrical system?
Why? Gyroscopic Principles: Gyroscopic Principles Rigidity in Space
A wheel with a heavily weighted rim spun rapidly tends to remain fixed in the plane in which it is spinning
The wheel is mounted on a set of gimbals so that the gyro is able to rotate freely in any plane
As the gimbals’ base tilts and twists, the gyro remains spinning in its original plane
Allows a gyroscope to measure changes in the attitude or direction of an airplane
Precession: Precession What is precession?
When an outside force tries to tilt a spinning gryo, the gyro responds as if the force had been applied at a point 90 degrees in the direction of rotation
Precession side – effects?
Friction in gimbals and bearings may cause a slow drifting in the heading indicator and occasional small errors in the attitude indicator
Questions?: Questions? Why is the turn coordinator powered by the electrical system?
A spinning wheel tends to stay in its original plane when disrupted, this refers to what concept?
Our heading indicator has become inaccurate by 5 degrees since takeoff, what is causing this? Vacuum Instruments: Vacuum Instruments Attitude Indicator: Attitude Indicator Only instrument that gives immediate and direct indication of the airplane’s pitch and bank attitude.
Gyro spins in the horizontal plane, mounted on dual gimbals that allow it to remain in the plane regardless of aircraft movement.
Pendulous vanes allow the attitude indicator erect itself on taxi
Attitude Indicator Errors: Attitude Indicator Errors Usually less than 5 degrees of bank error and 1 bar width of pitch error in a 180 degree turn.
Pendulous vanes act on the attitude indicators gyro in an undesirable way during turns.
The same pendulous vanes will cause the gyro to try to line up with the g – forces of a turn.
Acceleration and Deceleration can induce precession errors. During acceleration, horizon bar may show a climb, reinforcing the somatogravic illusion.
Tumbling: Past 100 degrees of bank or 60 degrees of pith
Heading Indicator: Heading Indicator What does it do?
Senses rotation about the aircraft’s vertical axis.
Precession can cause heading to drift, so remember to re – check about every 15 min. Turn Indicators: Turn Indicators Turn Coordinator:
Rate and Roll
Slip and Skid
Rate ONLY – older aircraft
What is the inclinometer?
Slip? Rate of turn is too slow for the angle of bank, ball moves inside
Skid? Rate of turn is too great for the angle of bank.
Gyro Instruments Summary: Gyro Instruments Summary The gyroscopic instruments incorporate two concepts, Rigidity in Space and precession
The turn coordinator is powered by the electrical system rather than the vacuum system so that in case of a failure, the pilot will always have a way to reference flight attitude.
Compass: Compass Bar Magnet aligns itself with the magnetic field Compass Errors: Compass Errors Variation: Difference between the true and magnetic poles. Use correction indicated on sectional
Compass Errors: Compass Errors Deviation: Compass error due to disturbances in magnetic field de to metals and electrical accessories in the airplane. Use deviation card in airplane to correct. Compass Errors: Compass Errors Magnetic Dip: Bar magnet contained in compass is pulled by the earth’s magnetic field, it tends to point north and somewhat downward. Greatest near the poles Compass Errors: Compass Errors Acceleration Error: Occurs when accelerating or decelerating on an easterly or westerly heading. As you accelerate, inertia causes the compass weight on the south end of magnetic to lag and turn the compass toward north. As you decelerate, inertia causes weight to move ahead, moves the compass toward a southerly heading.
Compass Errors: Compass Errors Turning Error: Most pronounced when turning to or from headings of north or south.
When you begin a turn from a heading of north, the compass initially indicates a turn to the opposite direction. When the turn is established, the compass begins to turn in the correct direction, but it lags behind the actual heading. Questions?: Questions?