Quick Reference Formulas
*majority of this is copy-pasted from somewhere else, i've added a few more which are important.
Calculating lead intercepts for DME arcs and any selected course
TAS / 200
Example:
120KTAS / 200 = 0.6
Therefore, initiate a standard rate turn 0.6nm prior to arriving at the arc.
For a 45 degree intercept to the final approach course, 0.3nm
(use GPS for XTRK information.)
For a 30 degree intercept, initiate at 0.2nm.
Calculating Rate of Descent to track glideslope
(Groundspeed / 60) * 300
Example:
105 knots GS
105/60 = 1.75
1.75 * 300 = 525FPM
Note: 300 is used because flying a 3-degree glideslope will cause the aircraft to descend 300 feet per nautical mile (FPNM.) If a nonstandard glideslope angle is published on the IAP, use that number instead (i.e. if 3.24 degrees, use 324.)
Alternate method (rule of thumb):
Use 10% of groundspeed, and multiply times 5.
Example:
90 knots GS
90 * 5 = 450FPM
This method is quite accurate, provided a standard 3.00 degree glideslope.
Calculating bank angles for standard rate turns
10% of TAS + 7
Example:
120KTAS
12 + 7 = 19 degrees angle of bank
Calculating VDP (or PDP, Planned Descent Point)
Distance-based VDP/PDP:
MDA (HAT) / 300
Example:
MDA is 430 ft. AGL. 430/300 = 1.4nm
Time-based VDP/PDP:
Subtract 10% of the MDA (HAT) from the time between FAF and MAP
Example:
MDA is 430 ft. AGL
Time between FAF and MAP is 3:54
10% of 430 = 43
Subtract 43 seconds from 3:54 = 3:11 to VDP/PDP
1 in 60 Rule Calculation
sin x = 1 / 60
1 = Aircraft XTK distance L/R of desired track.
60 = Distance travelled in Nautical Miles.
x = Track Error Angle (TKE). This is difference between the desired track and the track the
aeroplane is currently 'making good'.
Example :
sin x = 2 / 60
x = 2 degrees.
Therefore, to be able to reach Pos B, aircraft has to alter heading left 4 degrees.
Top of Descent Calculation
Height to lose x 3 + 10 = distance to begin descend.
as for ROD, groundspeed multiplied by 6.
Calculating lead intercepts for DME arcs and any selected course
TAS / 200
Example:
120KTAS / 200 = 0.6
Therefore, initiate a standard rate turn 0.6nm prior to arriving at the arc.
For a 45 degree intercept to the final approach course, 0.3nm
(use GPS for XTRK information.)
For a 30 degree intercept, initiate at 0.2nm.
Calculating Rate of Descent to track glideslope
(Groundspeed / 60) * 300
Example:
105 knots GS
105/60 = 1.75
1.75 * 300 = 525FPM
Note: 300 is used because flying a 3-degree glideslope will cause the aircraft to descend 300 feet per nautical mile (FPNM.) If a nonstandard glideslope angle is published on the IAP, use that number instead (i.e. if 3.24 degrees, use 324.)
Alternate method (rule of thumb):
Use 10% of groundspeed, and multiply times 5.
Example:
90 knots GS
90 * 5 = 450FPM
This method is quite accurate, provided a standard 3.00 degree glideslope.
Calculating bank angles for standard rate turns
10% of TAS + 7
Example:
120KTAS
12 + 7 = 19 degrees angle of bank
Calculating VDP (or PDP, Planned Descent Point)
Distance-based VDP/PDP:
MDA (HAT) / 300
Example:
MDA is 430 ft. AGL. 430/300 = 1.4nm
Time-based VDP/PDP:
Subtract 10% of the MDA (HAT) from the time between FAF and MAP
Example:
MDA is 430 ft. AGL
Time between FAF and MAP is 3:54
10% of 430 = 43
Subtract 43 seconds from 3:54 = 3:11 to VDP/PDP
1 in 60 Rule Calculation
sin x = 1 / 60
1 = Aircraft XTK distance L/R of desired track.
60 = Distance travelled in Nautical Miles.
x = Track Error Angle (TKE). This is difference between the desired track and the track the
aeroplane is currently 'making good'.
Example :
aircraft travelling from Pos A to Pos B on a course of 360 maintaining heading 360, distance A-B is 120 Nm. After travelling 60 Nm, aircraft is 2 miles Right of desired track.
sin x = 2 / 60
x = 2 degrees.
Therefore, to be able to reach Pos B, aircraft has to alter heading left 4 degrees.
Top of Descent Calculation
Height to lose x 3 + 10 = distance to begin descend.
as for ROD, groundspeed multiplied by 6.
posted by fail-operational at
4:01 AM
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