Pilot’s Handbook of Aeronautical Knowledge
FAA-H-8083-25C — FAA educational reference
Priority chapters from the FAA’s primary knowledge handbook: Aircraft Performance, Weather Theory and Airspace. The PHAK is an educational reference — it is not regulatory. It explains the aeronautical concepts behind the regulations. Additional chapters are being added over time.
Chapter 11. Aircraft Performance
Structure of the Atmosphere
The atmosphere is an envelope of air that surrounds the Earth and rests upon its surface. much a part of the Earth as is land and …
Atmospheric Pressure
Though there are various kinds of pressure, pilots are mainly concerned with atmospheric pressure. It is one of the basic factors …
Pressure Altitude
Pressure altitude is the height above the standard datum plane (SDP). The aircraft altimeter is essentially a sensitive barometer …
Density Altitude
The more appropriate term for correlating aerodynamic performance in the nonstandard atmosphere is density altitude—the altitude i…
Performance
Performance is a term used to describe the ability of an aircraft to accomplish certain things that make it useful for certain pur…
Takeoff and Landing Performance
The majority of pilot-caused aircraft accidents occur during the takeoff and landing phase of flight. Because of this fact, the pi…
Performance Speeds
True airspeed (TAS)—the speed of the aircraft in relation to the air mass in which it is flying. Indicated airspeed (IAS)—the spee…
Performance Charts
Performance charts allow a pilot to predict the takeoff, climb, cruise, and landing performance of an aircraft. These charts, prov…
Transport Category Aircraft Performance
Transport category aircraft are certificated under Title 14 of the CFR (14 CFR) part 25. For additional information concerning tra…
Chapter Summary
Performance characteristics and capabilities vary greatly among aircraft. As transport aircraft become more capable and more compl…
Chapter 12. Weather Theory
Atmosphere
The atmosphere is a blanket of air made mixture of gases that surrounds the Earth and reaches almost 350 miles from the surface of…
Coriolis Force
In general atmospheric circulation theory, areas of low pressure exist over the equatorial regions and areas of high pressure exis…
Measurement of Atmosphere Pressure
Atmospheric pressure historically was measured in inches of mercury ("Hg) by a mercurial barometer. [Figure 12-6] The barometer me…
Altitude and Atmospheric Pressure
As altitude increases, atmospheric pressure decreases. On average, with every 1,000 feet of increase in altitude, the atmospheric …
Altitude and Flight
Altitude affects every aspect of flight from aircraft performance to human performance. At higher altitudes, with a decreased atmo…
Altitude and the Human Body
As discussed earlier, nitrogen and other trace gases make up 79 percent of the atmosphere, while the remaining 21 TAKEOFF DISTANCE…
Wind and Currents
Air flows from areas of high pressure into areas of low pressure because air always seeks out lower pressure. The combination of a…
Atmospheric Stability
The stability of the atmosphere depends on its ability to resist vertical motion. A stable atmosphere makes vertical movement diff…
Air Masses
Air masses are classified according to the regions where they originate. They are large bodies of air that take on the characteris…
Fronts
As an air mass moves across bodies of water and land, it eventually comes in contact with another air mass with different characte…
Chapter Summary
Knowledge of the atmosphere and the forces acting within it to create weather is essential to understand how weather affects a fli…
Chapter 15. Airspace
Controlled Airspace
Controlled airspace is a generic term that covers the different classifications of airspace and defined dimensions within which ai…
Uncontrolled Airspace
Class G Airspace Uncontrolled airspace or Class G airspace is the portion of the airspace that has not been designated as Class th…
Special Use Airspace
Special use airspace or special area of operation (SAO) is the designation for airspace in which certain activities must be confin…
Other Airspace Areas
“Other airspace areas” is a general term referring to the majority of the remaining airspace. It includes: • Local airport advisor…
Airspace System
The primary purpose of the ATC system is to prevent a collision between aircraft operating in the system and to organize and exped…
Chapter Summary
This chapter introduces the various classifications of airspace and provides information on the requirements to operate in such ai…
Source information
- Source type
- FAA Handbook
- Official title
- Pilot's Handbook of Aeronautical Knowledge
- Citation
- FAA-H-8083-25C
- Publication number
- FAA-H-8083-25C
- Revision
- C
- Edition
- 2023
- Effective / amended
- Jan 1, 2023
- Status
- Current
- Last checked by SkeyeMentor
- Aug 8, 2026
- Internal version
- phak-ingest-1.0.0
- Official source