Example
To find the time to fly 225 kilometres at 90 kph
1. Set 60 of inner scale opposite 90 of outer
2. Opposite 225 of outer, read off 150 or 2 hours 30 minutes on inner
Example
Find distance travelled in 29 minutes at 87 knots.
1. Set 60 of inner opposite 87 on outer
2. Opposite 29 on inner, read off 42 on outer
Answer
29 minutes at 87 knots = 42 nautical miles
Example
Find speed if 23 statute miles are flown in 10 minutes.
1. Set 10 on inner scale opposite 23 of outer
2. Opposite 60 of inner read off 138 on outer
Answer
23 statute miles in 10 minutes = 138 mph
Example
How many statute miles and kilometres in 66 nautical miles?
1. Set 66 on inner opposite NAUT M index on outer
2. Read of on inner opposite STAT M index on the outer, 76 andat KM-M-LTR index, 122.3
Answer
66nm = 76 sm = 122.3 km
Example
What speed in knots and mph is the same as 161 kph?
1. Set 161 of the inner scale opposite KM-M-LTR index on outer scale
2. Read of on inner opposite NAUT M index on the outer, 87 and at the STAT M index, 100
Answer
161 kph=87 knots=100 mph
Example
How many yards and feet in 1920 metres?
1. Set 1920 of the inner at KM-M-LTR index on outer scale
2. Read of on inner scale opposite the outer scale indices YARDS 2100 and FEET 3600
Answer
1920 metres = 2100 yards = 6300 feet
Example
Convert 500 lbs to a weight in kgs.
1. Set 500 of the inner at the WEIGHT IN LBS index
2. Opposite WEIGHT IN LBS index of the outer read of 227 on the inner.
Answer
500 lbs = 227 kgs
Example
Convert 110 imperial gallons to U.S. gallons and litres.
1. Set 110 of the inner beneath the IMP gal index on outer scale
2. Opposite the U.S.GAL index on the outer read off 132 on the inner and opposite the KM-M-LTR index read off 500
Answer
110 imperial gallons = 132 U.S. gallons = 500 litres
Example
What is the weight in pounds and kilogrammes of 110 imperial gallons at a specific gravity of 0.72?
1. Set 110 of the inner beneath the IMP gal index on outer scale
2. Beneath 0.72 of the SpG index beneath WEIGHT IN LBS read 794 on the inner and at SpG 0.72 beneath WEIGHT IN KGS read 360 kgs
Answer
110 imperial gallons at SpG 0.72 weighs 794 pounds or 360 kgs
Example
How many imperial gallons weigh 1000 lbs at a specific gravity of 0.72 and what is the weight in kgs and the volume in litres and U. S. galls?
1. Set 1000 of the inner scale opposite SpG 0.72 beneath WEIGHT IN LBS on the outer scale
2. Read off
[a] at outer IMP GAL index, 138 1/2 on inner
[b] at outer KM-M-LTR index, 628 (LITRES) 1/2
[c] at outer U.S. GAL index, 166 1/2
[d] at SpG 0.72 beneath WEIGHT IN KGS, 454
Answer
1000 lbs of fuel at SpG 0.72 is by volume 138 1/2 imperial gallons of 628 litres or 166 1/2 U.S. gallons and weighs 454 kgs
Example
How much fuel is required for 168 minutes at 14.3 gph?
1. Set 60 of inner beneath 14.3 on outer
2. Opposite 168 on inner, read off 40 on outer
Answer
168 minutes at 14.3 gph requires 40 gallons
Example
If 52 gallons are used in 13 minutes, what is the fuel consumption per hour?
1. Set 13m0f inner beneath52 of outer
2. At 60 of inner, read off 240 of outer
Answer
52 gallons in 13 minutes = 240 gph
Example
What is thwe endurance if 133 letres are available and the fuel consumption is 57 lph?
1. Set 60 of the inner scale beneath 57 of the outer scale
2. Opposite 133 of the outer, read off 140 on the inner
Answer
At 57 lph, 133 litres gives an endurance of 140 minutes
The speed indicated on the air speed indicator is the Indicated Air Speed (IAS)
IAS corrected for position and instrument error gives the Rectified Air Speed (RAS)
RAS is always used on the computer for calculating the True Air Speed (TAS)
RAS corrected for density error gives the TAS up to 300 knots
The temperature indicated on the outside air thermometer is effected by kinetic heating and so will always read higher than the correct air temperature.
The value of this rise is given in the table below, and should always be subtracted from the indicated outside air temperature to obtain the correct air temperature.
| TAS knots | 100 | 140 | 175 | 200 | 225 | 245 | 265 | 280 | 300 |
|---|---|---|---|---|---|---|---|---|---|
| Temp rise 'C | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
Example
RAS 150 knots; Pressure altitude 18000 feet; (corrected) Temperature -30 deg C; what is TAS?
1. In AIR SPEED window set CORR AIR TEMP -30 opposite PRESS ALT 1000 FT, 18
2. Opposite 150 on the inner scale, read 195 on outer scale
Answer
RAS 150 knots at 18000 ft at -39 deg C = TAS 195 knots
Example
Corrected temperature at pressure altitude 4000 feet is -40 deg C, what is the TAS for a RAS of 140
1. Set temp -40 opposite PRESS ALT 1000 FT, 4
2. Opposite RAS 140 on inner read 135 TAS on outer scale
Answer
Press Alt 4000 ft; temp -40 deg C; RAS 140 = TAS 135
An altimeter measures
ALTITUDE when the sub-scale is set to QNH
PRESSURE ALTITUDE when the sub-scale is set to 1013.25 hPa
PRESSURE ALTITUDE / 100 = FLIGHT LEVEL
PRESSURE ALTITUDE and FLIGHT LEVEL are NOT subject to temperature error
Reasonably accurate corrections of ALTUTUDES up to 30,000 feet for temperature error can be made on the computer, although the correction is seldom called for.
Example
Altitude (QNH) 17,400 feet; Pressure altitude (1013.25 hPa) 18,000 feet corr temp -5 deg C; what is the true altitude?
1. In ALTITUDE window, set AIR TEMP deg C -5 against PRESS ALT x 1,000 FT, 18
2. Opposite 17,400 feet on inner scale, read 18,500 feet on the outer scale
Answer
Corr temp -5 deg C; Press alt 18,000 ft; altitude from altimeter 17,400 ft; true altitude is 18,500 ft
Again, this calculation is seldom called for
Example
Pressure altitude 18,000 ft, corr temp -5 deg C; what is the density altitude?
1. In the AIR SPEED window, set temp -5 deg C against pressure altitude 18,999 ft
2. In the DENSITY ALTITUDE window, read off density altitude 20,000 ft
Answer
The density at pressure altitude 18,000 ft with a temperature of -5 deg C is the same as the density at 20,000 ft in the International Standard Atmosphere (ISA)
On the computer a scale is provided beneath the circular slide rule for the conversion of temperatures in degrees fahrenheit to degrees centigrade
The circular slide rule can also be used to solve the "1 in 60 Rule problems"
Example
Pinpoint 3 nautical miles to starboard of track, 36 nm along track. What is the Track Error?
1. Set 36 on the inner scale opposite 3 of the outer scale
2. Opposite 60 of the inner scale, read 5 on the outer scale
Answer
3 nm off track to starboard in 36 nm gives a track error of 5 deg Starboard
Example
Inbound to VOR/DME station, desired track 241, VOR gives QDM 248 and DME range is 43 nm. How far is aircraft off desired track?
1. Set 60 of inner opposite 7 of outer, (284-241)
2. Opposite 43 of inner, read (5.02) distance off on outer
Answer
QDM 248; desired track 241; DME 43 nm; aircraft is 5 nm port of desired track
Example
What is the speed of sound at a corrected air temperature of -35 deg C
1. In AIR SPEED window, set MACH NO INDEX Opposite -35 deg C
2. Opposite 1 on the inner scale, read 600 on the outer.
Answer
The speed of sound at -35 deg C is 600 knots
Example
Set on the wind velocety of 230/35 knots. (TAS 135 knots)
1. Set 230 at the true heading index
2. Using "L" side of the scale, mark in wind +35 units below the centre dot
Example
Hdg(T) 140: W/V 230/35; TAS 135; What is Tr and G/S?
1. Mark in wind + (as at 24 above)
2. Set 140 at TRUE HEADING Index
3. Set centre dot over 135
4. Beneath wind + read off G/S 140 and Drift 14 deg Port
5. Beneath 14 deg P on outer drift scale, read Tr 126(T) on Inner scale
Answer
Hdg 140(T); TAS 135; W/V 230/35; gives Tr 126(T); G/S 140
Example
W/V 325/40; Tr 2609T0; tas 120; What is Hdg(T), G/S and Drift?
1. Mark in wind + (use "L" side of slide)
2. Set 120 beneath center`dot
3. Set 260 at TRUE HEADING index
4. Read off drift 20 deg P beneath wind +
5. Beneath 20 P on drift scale, set Tr 260
6. Beneath wind + read drift 18 deg P
7. Beneath 18 P on drift scale, set Tr 260
8. Beneath wind + read drift 18 deg P (same as beneath wind +)
9. Read off G/S 97 and drift 18 deg P
10. Read off Hdg 278(T)
Answer
W/V 325; Tr 260(T); TAS 120; gives Hdg 278(T), G/S 97 and 18 deg P
Example
Hdg 180(T); TAS 315; Tr 188(T); G/S 335; What is W/V
1. Set 180 at TRUE HEADING index
2. Set 315 beneath centre dot ("H" side of slide)
3. Above 188 on circular scale, read off drift 8 S; on plotting disc at intersection of 335 groundspeed arc and 8 S drift line
4. Rotate disc until wind + lies on zero drift line beneath the centre dot
5. Read off wind direction 070 and wind speed 50
Answer
Hdg 180(T); TAS 315, Tr 188(T); G/S 335, gives W/V 070/50
Example
W/V 260(M)/40: Runway direction 225(M); what are the headwind and crosswind components?
1. Set 260 at TRUE HEADING index
2. Set zero of squared graph ("L" side of slide) beneath centre dot
3. Mark in wind + 40 units below the centre dot on the centre lone of the graph
4. Set 225 at TRUE HEADING index
5. Beneath wind + read off perpendicular to the centre line of crosswind of 23 knots
6. Beneath wind + read of headwind component of 34 knots on the line parallel to the centre line
Answer
On runway direction 225(M) with a surface wind of 260/40 the headwind component is 34 knots and the crosswind component is 23 knots from the right (wind cross is to the left of the centre line)
Example
Aircraft heading is 344' and you wish to intercept the inbound track of 245' to the N.D.B. what will be the realitive bearing of the N.D.B. on intercepting the inbound track of 245'?
1. Set the red arrow on the selector opposite 344' on the inner scale
2. Opposite 245' on the innermost scale read off 229' on the inner scale
Answer
Turn on to 245' inbound track when radio compass reads 229' relative
Example (a)
TAS 214 Kt W/V 30 Kt, find Wind Speed ratio
1. Set 1 on inner scale opposite 214 on outer scale
2. Opposite 30 on the outer scale read 14 on inner scale
Answer
TAS 214Kt: Wind Speed 30 Kt, Wind Speed ratio = 0.14
Example (b)
TAS 1040 Kt G/S 1.13, find G/S
1. Set 1 on inner scale opposite 1040 on outer scale
2. Opposite 1.13 on the outer scale read 1175 on inner scale
Answer
TAS 1040 Kt: G/S ratio = 1175 Kt.
Example
Hdg (T) 265; W/V 210/35; TAS 290 Kt.What is Tr and G/V?
1. Calculate Wind Speed ratio. 1 on inner scale against 290 on the outer scale, against 35 on the outer scale read radio (0.12) on inner scale
2. Set index on wind arm to 0.12
3. Rotate the wind arm until WIND DIRECTION line lies over 210' on the outer compass rose.
4. Holding the wind arm in place rotate the grided disc until the HEADING INDEX points to 265' on the outer compass rose
5. Under the index on the wind arm read off the drift (6'S) and G/S radio (0.93)
6. Against 6' Starboard on the drift scale read off the Track on the outer compass rose (271')br>
7. Convert the G/S ratio into a Ground Speed 1 on inner scale against 290 on outer scale (as for first stage above0, against 0.93 on inner scale read off G/S on outer scale (271 Kt)
Answer
Hgg (T) 265; W/V 210/35; TAS 290 Kt gives Trk 271' (T) G/S 271 Kt
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