061 GNAV Formulas

Question 1

1 NM = ? km = ? ft

Answer 1

1 NM = 1.852 km = 6080 ft

Question 2

Departure (GNAV)

Answer 2

dep = chlong • cos(lat°)

• dep = departrue [NM]*
• chlong = change in longitude [x’ (minutes)]*
• lat = latitude [x° (degrees)]*

Question 3

Cross-/head-/tailwind components

Answer 3

XWC = V_wind • sin(wa)

HWC or TWC = V_wind • cos(wa)

• XWC = crosswind component*
• HWC = headwind component*
• TWC = tailwind component*
• V_wind = wind speed (wind speed and components same unit)*
• wa = wind angle [x°] (never more than 90°)*

Question 4

Earth convergence

Answer 4

EC = chlong • sin(mean lat°)

• EC = earth convergence [x° (degrees)]*
• chlong = change in longitude [x° (degrees)]*
• mean lat = mean latitude [x° (degrees)]*

Question 5

Conversion angle

Answer 5

CA = ½ • EC

• CA = conversion angle [x°]*
• EC = earth convergence [x°]*

Question 6

ILS glide path intercept height

(glide angle/gradient)

Answer 6

Intercept height = θ • 100 • dist from thld + height above thld

Intercept height = glide gradient • 60 • dist from thld + height above thld

• Intercept height [ft]*
• θ = glide angle [x°]*
• height above threshold [ft] (usually 50 ft)*
• thld = threshold*

Question 7

Rate of descent (GNAV)

(glide angle/gradient)

Answer 7

RoD = θ • 100• (GS/60)

RoD = glide gradient • GS

• RoD = rate of descent [ft/min]*
• θ = glide angle [x°]*
• GS = groundspeed*

Question 8

Chart convergence

Answer 8

CC = chlong • sin(P_o)

• CC = chart convergence [x°]*
• chlong = change in longitude [x° (degrees)]*
• P_o = parallel of origin*
• • same formula as earth convergence -*

Question 9

Constant of cone

Answer 9

cone = sin(P_o)

P_o = parallel of origin

Question 10

Grid track

Answer 10

GT = TT +/- conv

GT = MT +/- griv

• GT = grid track [x°]*
• TT = true track [x°]*
• MT = magnetic track [x°]*
• conv = convergence [x°] (west = - , east = +)*
• griv = grivation [x°]*

Question 11

Grivation

Answer 11

grivation = convergence + variation

Question 12

Convergence

(grid nav)

Answer 12

convergence = chlong

chlong = change in longitude from datum meridian to position [x°]

Question 13

Time conversion (x°/h)

Answer 13

15°/h

1°/ 4 min

Question 14

NM ⇔ NAM

Answer 14

Cross multiplication (e.g. GS = NM • TAS ÷ NAM)

see attachement

Question 15

Local speed of sound

Answer 15

• a = local speed of sound [kt]*
• T = temperature [K]*

Question 16

Mach number

Answer 16

• M = Mach number*
• TAS = true airspeed [kt]*
• a = local speed of sound [kt]*

Question 19

True height

(compared to ISA)

Answer 19

Δh_true = Δh_ISA • (1 + 0.004 • ΔISA)

• Δh_true = true height [ft]*
• Δh_ISA = height in ISA atmosphere [ft]*
• ΔISA = ISA deviation [°C]*

Question 20

1 kg = ? lb

Answer 20

1 kg = 2.2 lb

Question 21

1 sm = ? km

Answer 21

1 sm = 1.609 km

Question 22

1 imp gal = ? US gal = ? l

Answer 22

1 imp gal = 1.2 US gal = 4.55 l

Question 23

1 US gal = ? l

Answer 23

1 US gal = 3.8 l

Question 24

Density altitude

Answer 24

DA = PA + ( 120 • ΔISA )

• DA = density altitude*
• PA = pressure altitude*
• ΔISA = ISA deviation*

Question 25

1 inch = … cm

Answer 25

1 inch = 2.54 cm