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Flight Computer Jeppesen CR4

How To Use Your Flight Computer

These videos use the Jeppesen CR4, however most operate on the same principal.

How To Determine Head / Tailwind And Crosswind Component (Above)

  1. Set TAS triangle to airspeed (1:00 to 1:11)
  2. Turn green dial so wind angle from TAF or ARFOR is on black TAS triangle (1:11 to 1:35)
  3. Draw circle around wind speed (1:35 to 2:05)
  4. Turn green dial so heading we want to fly is at the top (2:05 to 2:30)
  5. This now answers how much head/tail and crosswind we have( See from 2:30 to 3:30)


How To Work Out Where We Need To Head Due To That Wind (Above)

  1. Make sure TAS triangle is set to aircraft TAS on the outer white scale
  2. Go around outer scale until we find the crosswind component eg 8° (3:15 to 4:00)
  3. Go in two levels on the white outer from where it has degrees° so that when TAS = 100 eg 8° crosswind adjust heading by 4.5° (3:45 to end)

Determine How Much To Adjust Heading Due To Crosswinds (Above)

  1. Get wind forecast and set wind angle on the outer green scale to the wind angle. Eg: if it was 090, set 90 on the outer green scale to the top of the dial at the black TAS triangle (0:40-1:25)
  2. Then go down the scale from there and circle wind speed eg if it was 20 kt, you would go down the row from TAS 60, 50, 40 , 30 and then circle 20 (1:10 to 2:00)
  3. Turn outer green dial so that intended heading is now at the top black TAS triangle (2:35 to 3:15)
  4. This now displays our wind relative to our heading and we can read off if it is a head wind (above the x axis) tailwind (below the x axis) a wind from the right (right of y axis) a wind from the left (left of the y axis) (3:00 to 3:35)
  5. Then go to outer scale and read crosswind eg if its 10kt crosswind go to the outer scale 6° (3:35 to 5:05)
  6. Read off the next scale in how many degrees you need to adjust. Eg: at 100kt TAS for 10kt of crosswind on the outer scale we would need to adjust 6° of heading. (4:20 to End)
  7. Ground speed is simple maths, deduct headwind component from TAS.

How To Find Time(Above)

  1. Find Black triangle hour marker and set to GROUND SPEED
  2. The outer white scale is miles
  3. The outer yellow scale is minutes
  4. So as long as you set your speed to GROUND SPEED ACURATELY you can go around and read off any distance and time

How To Find Time Distance (Above)

  1. Set 1 hour black marker to GROUNDSPEED on the outer white scale
  2. You can now read off miles on the outer scale for any time or any time for distance. Time will be on the outer yellow scale and miles on the outer white scale.

How To Do Fuel Calculations (Above)

  1. Set 1 hour black marker to LITRES on the outer white scale EG: 20
  2. You can now read off LITRES on the outer scale for any time or any time for LITRES. Time will be on the outer yellow scale and LITRES on the outer white scale.