Section 3 EO C437.01 – SOLVE NAVIGATION PROBLEMS WITH A MANUAL FLIGHT COMPUTER

Navigation calculations are simplified by the use of a flight computer. Most manual flight computers consist of two sides: a circular slide rule and a wind side.

Show the slide of Figure A-1 to the cadets.

The instructions for using a manual flight computer are often printed directly on the flight computer.

Circular Slide Rule

The circular slide rule can be used to solve any problem of multiplication, division, or proportion. There are three scales printed on the circular slide rule. The outer scale is fixed to the computer. The two inner scales are printed together on a disc that may be rotated to any position opposite the outer scale.

Show the slide of Figure A-2 to the cadets.

The outer scale represents miles, gallons, true airspeed and corrected altitude. The inner scale represents time in minutes, calibrated airspeed, and calibrated altitude. The third scale represents time in hours and minutes.

The figures on the circular slide rule may represent any proportion or multiple of 10. For example, 10 on the outer scale may represent 1, 10, or 100; 45 may represent 4.5, 45, or 450.

One of the most common types of calculations a pilot has to make is converting from one unit of measure to another. Fuel is sold by the litre, but fuel quantities and consumption are usually specified in the aircraft manual in gallons. Wind speeds are reported in knots, but the airspeed indicator (ASI) may be in statute miles per hour.

Using the circular slide rule for conversion calculations is a simple process. Rotate the inner scale to the correct position, locate the original quantity / measure on the outer scale, and read the converted quantity / measure from the inner scale, opposite to the appropriate marking.

Convert Between Nautical and Statute Miles

To convert between nautical and statute miles:

1.Rotate the inner scale until the known number of miles is under the appropriate index (NAUT or STAT).

2.Read the converted number of miles under the other index.

For example, to convert 90 nautical miles to statute miles: (1) Rotate the inner scale until 90 is under the nautical miles index. (2) Read the number of statue miles under the statue miles index (104 statute miles).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 1  Nautical and Statute Mile Indexes

Convert Between Miles and Kilometres

To convert between miles and kilometres:

1.Rotate the inner scale until the known number is under the appropriate index (NAUT, STAT, or KM).

2.Read the converted number under the desired index.

For example, to convert 115 statute miles to kilometres: (1) Rotate the inner scale until 115 is under the statute miles index. (2) Read the number of kilometres under the kilometres index (185 km).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 2  Statute Mile and Kilometre Indexes

Convert Between Imperial and US Gallons

To convert between imperial and US gallons:

1.Rotate the inner scale until the imperial and US gallon indexes are aligned.

2.Locate the known quantity (outer scale for imperial gallons and inner scale for US gallons) and read the desired quantity on the opposite scale.

For example, to convert 55 imperial gallons to US gallons: (1) Rotate the inner scale until the imperial and US gallon indexes are aligned. (2) Locate 55 on the outer scale and read the quantity of US gallons on the inner scale (66 US gallons).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 3  US and Imperial Gallon Indexes

Convert Between Gallons and Litres

To convert between gallons and litres:

1.Rotate the inner scale until the litres index is aligned with the appropriate gallon index.

2.Locate the known quantity and read the desired quantity on the opposite scale.

For example, to convert 100 L to US gallons: (1) Rotate the inner scale until the litres index is aligned with the US gallon index. (2) Locate 100 on the outer scale and read the quantity of US gallons on the inner scale (26 US gallons).

Convert Between Pounds and Kilograms

To convert between pounds and kilograms:

1.Rotate the inner scale until the pounds index is aligned with the kilograms index.

2.Locate the known quantity and read the desired quantity on the opposite scale.

For example, to convert 100 pounds to kilograms: (1) Rotate the inner scale until the pounds index is aligned with the kilograms index. (2) Locate 100 on the outer scale and read the quantity of kilograms on the inner scale (45 kg).

The objective of this activity is to have the cadets practice converting units of measure using a manual flight computer.

Nil.

1.Distribute a manual flight computer and a Navigation Problems Worksheet to each cadet.

2.Have the cadets complete Part 1 of the worksheet using the manual flight computer.

3.Review the answers using the answer key located at Attachment C.

Nil.

The rate arrow on the disk is always set to indicate a value per hour on the outer scale. There are three basic types of speed-time-distance problems. In two types of problems the speed is known, in the third, the speed is the unknown.

When solving speed, distance, and time problems, the units have to agree. For example, if the speed is in knots, the distance has to be in nautical miles and the time in hours. If the units do not agree, use the circular slide rule to perform the required conversions to make the units agree before attempting to solve the problem.

Calculating Time (Speed and Distance are Known)

To calculate time when speed and distance are known:

1.Rotate the inner scale until the rate arrow is opposite the speed.

2.Locate the distance on the outer scale.

3.Read the time from the inner scale, opposite the distance.

For example, to calculate the time en route if the speed is 150 knots and the distance is 245 nautical miles: (1) Rotate the inner scale until the rate arrow is opposite 150. (2) Locate 245 on the outer scale. (3) Read the time en route from the inner scale, opposite 245 (1 hour and 38 minutes).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 4  Rate Arrow, Speed, Distance, and Time

For example, to calculate the time en route if the speed is 120 knots and the distance is 100 statute miles: (1) Convert the distance to nautical miles (87). (2) Rotate the inner scale until the rate arrow is opposite 120. (3) Locate 87 on the outer scale. (4) Read the time en route from the inner scale, opposite 87 (44 minutes).

When calculating time en route, use the aircraft's groundspeed, not the airspeed.

Calculating Distance (Speed and Time are Known)

To calculate distance when speed and time are known:

1.Rotate the inner scale until the rate arrow is opposite the speed.

2.Locate the time on the inner scale.

3.Read the distance from the outer scale, opposite the time.

For example, to calculate the distance if the speed is 125 knots and the time en route is 4.5 hours: (1) Rotate the inner scale until the rate arrow is opposite 125. (2) Locate 4:30 on the inner scale. (3) Read the distance from the outer scale, opposite 4:30 (564 nautical miles).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 5  Rate Arrow, Speed, Distance, and Time

When calculating distance, use the aircraft's groundspeed, not the airspeed.

Calculating Speed (Distance and Time are Known)

To calculate speed when distance and time are known:

1.Rotate the inner scale until the distance is opposite the time.

2.Locate the rate arrow.

3.Read the speed from the outer scale, opposite the rate arrow.

For example, to calculate the speed if the distance is 26 nautical miles and the time en route is 13 minutes: (1) Rotate the inner scale until 26 is opposite 13. (2) Locate the rate arrow. (3) Read the speed from the outer scale, opposite the rate arrow (120 knots).

Note. From "Air Classics E6-B Flight Computer Instructions", Aviation Supplies and Academics, Inc. Retrieved November 26, 2008, from http://www.asa2fly.com/files/support/E6B_Manual.pdf

Figure 6  Rate Arrow, Speed, Distance, and Time

When calculating speed from distance and time, it is the groundspeed that is being calculated, not the airspeed.

The objective of this activity is to have the cadets practice calculating speed, distance, and time using a manual flight computer.

Nil.

1.Have the cadets complete Part 2 of the worksheet using the manual flight computer.

2.Review the answers using the answer key located at Attachment C.

Nil.