| Home | Privacy | Contact |

Pilot's Handbook of Aeronautical Knowledge

Basic Calculations

| First | Previous | Next | Last |

Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Establishing a wind correction angle.
Figure 15-17. Establishing a wind correction angle that will counteract wind drift and maintain the desired course.

To summarize:
• Course—intended path of an aircraft over the ground
or the direction of a line drawn on a chart representing
the intended aircraft path, expressed as the angle
measured from a specific reference datum clockwise
from 0° through 360° to the line.
• Heading—direction in which the nose of the aircraft
points during flight
• Track—actual path made over the ground in flight, (If
proper correction has been made for the wind, track
and course are identical.)
• Drift angle—angle between heading and track.
• WCA—correction applied to the course to establish
a heading so that track coincides with course.
• Airspeed—rate of the aircraft's progress through the
• GS—rate of the aircraft's inflight progress over the

Basic Calculations

Before a cross-country flight, a pilot should make common
calculations for time, speed, and distance, and the amount
of fuel required.

Converting Minutes to Equivalent Hours
Frequently, it is necessary to convert minutes into equivalent
hours when solving speed, time, and distance problems. To
convert minutes to hours, divide by 60 (60 minutes = 1 hour).
Thus, 30 minutes is 30/60 = 0.5 hour. To convert hours to
minutes, multiply by 60. Thus, 0.75 hour equals 0.75 x 60
= 45 minutes.

Time T = D/GS
To find the time (T) in flight, divide the distance (D) by the
GS. The time to fly 210 NM at a GS of 140 knots is 210 ÷
140, or 1.5 hours. (The 0.5 hour multiplied by 60 minutes
equals 30 minutes.) Answer: 1:30.
Distance D = GS X T
To find the distance .own in a given time, multiply GS by
time. The distance flown in 1 hour 45 minutes at a GS of 120
knots is 120 x 1.75, or 210 NM.
To find the GS, divide the distance flown by the time required.
If an aircraft flies 270 NM in 3 hours, the GS is 270 ÷ 3 =
90 knots.

Converting Knots to Miles Per Hour
Another conversion is that of changing knots to miles per hour
(mph). The aviation industry is using knots more frequently
than mph, but it might be well to discuss the conversion for
those that use mph when working with speed problems. The
NWS reports both surface winds and winds aloft in knots.
However, airspeed indicators in some aircraft are calibrated
in mph (although many are now calibrated in both miles per
hour and knots). Pilots, therefore, should learn to convert
wind speeds that are reported in knots to mph.

A knot is 1 nautical mile per hour (NMPH). Because there are
6,076.1 feet in 1 NM and 5,280 feet in 1 SM, the conversion
factor is 1.15. To convert knots to miles per hour, multiply
speed in knots by 1.15. For example: a wind speed of 20
knots is equivalent to 23 mph.

Most flight computers or electronic calculators have a
means of making this conversion. Another quick method of
conversion is to use the scales of NM and SM at the bottom
of aeronautical charts.