Flight Instrumentation

Lesson Objectives Describe the operation of an airspeed indicator Identify different types of airspeed readings Describe the operation of an altimeter Describe the effects of barometric pressure and temperature of altitude readings Describe the operation of attitude indicators List the data elements a pilot can gain from a horizontal situation indicator Chapter 4, Lesson 4

The Operation of an Airspeed Indicator An airspeed indicator determines airspeed by measuring the difference between dynamic air pressure and static air pressure It gets its data from a system called the pitot- static system Pitot tube captures dynamic as well as static pressure Pitot tube’s pressure chamber sends the total pressure to the airspeed indicator Static port sends static pressure to the airspeed indicator When the dynamic pressure changes, airspeed indicator shows either increase or decrease

Airspeed Readings Indicated — Airspeed shown on the airspeed indicator Calibrated — Indicated airspeed corrected for installation error and instrument error Equivalent — As a plane flies faster than 200 knots, the air being squeezed into the pitot tube becomes more compressed. This leads to an error that indicates the plane is flying faster than it really is. This error grows particularly large near the speed of sound. Pilots can correct for error at speeds exceeding 200 knots using a chart to find the equivalent airspeed True — Calibrated airspeed corrected for altitude and temperature. Because air density changes at different altitudes and temperatures. The pilot uses a flight computer that calculates the true airspeed when the pilot enters the calibrated airspeed, pressure altitude, and temperature..

Airspeed Indicator Markings Airspeed indicator has color-coded markings White arc— Aircraft’s operating range for approaches and landings Green arc—Aircraft’s normal operating range Yellow arc—Range in which a pilot should be cautious Red line—Pilot should never exceed this speed Chapter 4, Lesson 4 Reproduced from US Department of Transportation/Federal Aviation Administration

The Operation of the Altimeter The most common type of altimeter is the pressure altimeter The major component is a stack of sealed aneroid wafers; an aneroid is a sealed flat capsule made out of thin metal disks and emptied of all air The pressure inside the sealed wafers is 29.92 inches of mercury. A static port captures static pressure and introduces it into the sealed altimeter case. "Reproduced from US Department of Transportation/Federal Aviation Administration"

The Operation of the Altimeter The wafers expand or contract because of changes in the static pressure in the surrounding atmosphere due to change of altitude. Mechanical parts connect the wafers’ movements to needles on the altimeter’s face. When the wafers contract, the needles show a decrease in altitude. When the wafers expand, the needles indicate an increase in altitude. "Reproduced from US Department of Transportation/Federal Aviation Administration"

Effect of Barometric Pressure on Altitude Reading The altitude shown on the altimeter face is correct only when certain standards are met: Sea level barometric pressure of 29.92 inches of mercury Temperature of 59 degrees F (15 degrees C) A standard rate of decrease in pressure and temperature with an increase in altitude Since barometric pressure and temperature generally don’t remain constant; pilots must adjust their altimeters If flying from high-pressure area to a low-pressure area without adjusting the altimeter, the aircraft’s actual height would be lower than the altimeter indicates

Effect of Temperature on Altitude Readings Similarly when flying in temperatures that are colder than standard, the actual altitude will be lower than the altimeter indicates When the air is warmer than standard, the aircraft will be higher than the altimeter says Pilot can correct for temperature with the help of a computer Chapter 4, Lesson 4 Reproduced from US Department of Transportation/Federal Aviation Administration

The Operation of Attitude Indicators Displays an aircraft’s attitude which can alert the pilot to possible changes in airspeed, altitude, and direction Works according to gyroscopic rules; features a fixed aircraft on its face and a freely moving horizon bar If an aircraft pitches or banks, the horizon bar of the altitude indicator remains in its original horizontal plane. This is because the bar is fixed to the gyroscope so it can maintain its horizontal plane even as the aircraft moves about its lateral or longitudinal axis. Chapter 4, Lesson 4 Reproduced from US Department of Transportation/Federal Aviation Administration

Attitude Indicator An attitude indicator generally has limits as to how much pitch and roll it can indicate Banking limits are usually from 100 to 110 degrees. Pitch limits are from about 60 to 70 degrees. Chapter 4, Lesson 4 Reproduced from US Department of Transportation/Federal Aviation Administration

The Functions of a Horizontal Situation Indicator HSI is a flight instrument that indicates an aircraft’s position and direction in relation to the desired route Information includes: magnetic heading course the pilot has selected deviation from the intended course glide slope indicators deviation from the intended descent red warning flags when HSI isn’t working properly Chapter 4, Lesson 4 Reproduced from US Department of Transportation/Federal Aviation Administration

Lesson Objectives Describe the operation of an airspeed indicator Identify different types of airspeed readings Describe the operation of an altimeter Describe the effects of barometric pressure and temperature of altitude readings Describe the operation of attitude indicators List the data elements a pilot can gain from a horizontal situation indicator Chapter 4, Lesson 4

Activity 1: Calculating True Airspeed   Read the information about corrections to indicated airspeed on the airspeed indicator Examine the example on how to calculate true airspeed and then solve the problems Chapter 4, Lesson 4

Activity 2: Airspeed Indicators Review the textbook information on airspeed indicator markings Answer the questions about the airspeed indicator in your own words Chapter 4, Lesson 4

Activity 3: Altimeters and Temperature Determine the air or ground temperature or altitude Examine the examples and solve the problems Chapter 4, Lesson 4

Activity 4: Functions of the Horizontal Situation Indicator Review the textbook information on the functions of a horizontal situation indicator (HSI) Describe in your own words the functions of some features on the HIS and what they tell a pilot Chapter 4, Lesson 4

Activity 5: Attitude Indicator Readings Review the textbook information on the functions of attitude indicators Answer the questions about the attitude indicator and determine the readings Chapter 4, Lesson 4

Activity 6 Flight Simulator: Flight Instruments Identify the different aircraft flight instruments using Microsoft Flight Simulator Chapter 4, Lesson 4