The Navigation Computer

The Navigation Computer is an analogue computer used to solve navigation and flight planning problems quickly and easily. The EASA regulations allow students to take the analogue computer of their choice into the General Navigation examination.

Navigation Computer calculations form a large part of the General Navigation EASA ATPL and Navigation PPL examination. Almost 25% of the exam comprises direct Navigation Computer questions and many of the other questions can often be solved faster with a Navigation Computer than by calculator. Rapid operation of the Navigation Computer is also fundamental to Flight Planning. It is essential that you learn to operate the Navigation Computer quickly and accurately. Those who do not make the effort to master it completely lose marks unnecessarily in exams.

We are pleased to offer you:

a fully functional version of the Navigation Computer
detailed instruction manual
more than 200 exercises to consolidate skills

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Slide Rule Face

Wind Face

MULTIPLY:

9 × 8 = 72

11 × 30 = 330

111 × 12 = 1332

202 × 2.1 = 424.2

315 × 0.3 = 94.5

275 × 45 = 12375

121.5 × 14 = 1700

12 × 12 × 12 = 1728

237 × 7 × 0.5 = 830

12 × 13 × 15 = 2340

DIVIDE:

35 ÷ 7 = 5

210 ÷ 7 = 30

32 ÷ 8 = 4

325 ÷ 5 = 65

39 ÷ 60 = 0.65

275 ÷ 45 = 6.11

2705 ÷ 4.5 = 601.1

72960 ÷ 12 = 6080

755 ÷ 0.8 = 944

20.2 ÷ 22 = 0.917

PROPORTIONING:

15 / 5 = 20 / 6.67

175 / 18 = 50 / 5.14

5 / 34 = 20 / 136

Your rate of descent is 270 metres per minute. How many minutes to descend through 2100 metres? 7.8 minutes

Your rate of descent is 270 metres per 2 minutes. How far do you descend in 5 minutes? 675 metres

Complete the tabulations:

Ground speed (kt)	Distance (NM)	Time (min)
230	33	8.6
175	234	80
182	510	168
145	36	15
260	334	77
200	170	51
169	46.5	16.5
143	231	97
218	156	43
320	18.5	3.5

Fuel Flow	Time	Fuel Used
140 litres/h	1 h 20 min	187 litres
2120 kg/h	16 min	570 kg
117 imp.gal	3 h 25 min	400 imp.gal
8.7 US.gal/h	2 h 15 min	19.6 US.gal
9800 lb/h	5 h 20 min	52267 lb
165 kg/h	2 h 33 min	420 kg
603 lb/hr	1 h 47 min	1075 lbs
295 US.gal/h	4 h 40 min	1377 US.gal
160 litres/h	1 h 45 min	280 litres
260 imp.gal/h	4 h 18 min	1120 imp.gal

Nautical Mile	Statute Mile	Kilometre
88	101	163
23.4	27	43.5
47	54	87
141	162	261.5
127.7	147	237
167	192	310
5400	6210	10000
433	499	805

Metres	Feet
1000	3280
8.8	29
120	393
356	1166

Litres	Imp.gal	US.gal	SG	kg	lb
1000	220	264	0.78	780	1716
1909	420	504	0.81	1546	3402
3031	667	800	0.84	2546	5600
1250	275	330	0.80	1000	2200
1263	278	333	0.72	909	2000

CAS	Pressure Altitude	SAT(°C)	TAS
140	10000	-10	162
175	8000	+5	200
220	15000	-22	273
300	30000	-40	472
180	12500	-25	212
165	9000	+7	193
163	11000	+10	199
295	31000	-53	460
160	12000	-10	192
260	35000	-45	450

Mach No	SAT (°C)	TAS
0.82	-50	477
0.66	-60	375
0.71	-38	425
0.77	-60	438
0.92	-11	580
0.71	-47	415

Ind Alt	SAT (°C)	True Alt
10000	-20	9450
18000	-30	17400
6000	+10	6150
27000	-50	25600
21500	-35	20800
8000	+10	8350

Pressure Alt	SAT (°C)	Density Altitude
10000	+15	12400
6000	+25	8040
27000	-40	26880
23000	-22	24080
25000	-45	23800
29000	-38	29600

To calculate track and ground speed:

1. Set wind direction under true heading index.

2. Mark in wind dot on centre line of computer BELOW centre dot at a distance

equal to wind speed scale to scale.

3. Set true heading at true heading index.

4. Set TAS under centre dot.

THE COMPUTER IS NOW SET UP CORRECTLY WITH HEADING AT THE TRUE HEADING INDEX. DO NOT DISTURB THE SETTINGS.

5. Read off drift under wind dot.

6. Read off track on circular scale beneath drift on drift scale.

7. Read off ground speed beneath wind dot.

HDG°(T)	W/V	TRACK MADE GOOD°(T)	TAS	GS
273	230/40	286	150	124
181	150/30	194	90	66
054	350/28	073	88	80
084	255/55	082	210	264
141	280/35	135	190	217
274	030/40	262	150	171
213	060/35	218	150	181
029	090/40	016	170	155
305	350/16	297	100	89
187	270/60	157	110	119
310	045/45	302	320	327
138	125/50	140	390	340
253	180/70	263	415	400
131	210/40	126	485	480
100	315/55	104	480	525
270	315/55	242	110	81
200	125/50	214	210	204
180	210/40	168	135	102
140	180/70	119	170	125
093	045/45	103	210	182
103	060/35	109	240	215
237	270/60	225	205	158
343	030/40	338	350	322
030	350/16	032	390	379
315	280/35	318	375	346
145	090/40	150	420	400
290	255/55	194	490	445
191	150/30	193	480	459
257	350/28	254	475	480
157	230/140	139	460	440

To calculate the wind velocity:

1. Set true heading at the heading index.

2. Set TAS under the centre dot.

3. Read off drift on drift scale opposite track on circular scale.

4. Mark in wind dot at intersection of ground speed and drift line.

5. Rotate face until wind dot lies on centre line BELOW centre dot.

6. Read off wind direction at true heading index and wind speed to scale.

HDG°(T)	W/V	TRACK MADE GOOD°(T)	TAS	GS
209	155/30	219	150	134
270	055/25	266	180	202
223	050/40	224	206	246
069	014/26	079	138	124
299	002/14	293	125	120
167	217/22	162	202	190
213	144/26	231	85	80
014	129/38	005	200	218
330	250/28	348	90	90
179	300/50	168	196	226
098	300/30	100	310	338
091	172/80	080	440	435
050	298/40	055	398	415
351	085/75	340	393	405
288	155/41	292	434	462
276	224/35	281	335	316
280	014/40	275	430	435
291	125/30	292	330	360
097	124/25	095	343	322
056	227/32	055	287	320
108	298/50	109	480	530
176	277/40	171	428	438
270	312/40	265	335	308
248	270/80	243	406	332
247	200/41	252	380	352
200	172/32	202	435	403
198	143/25	202	340	325
275	275/40	275	435	395
274	245/22	275	290	270
321	298/60	326	338	280
045	308/85	061	285	305
196	065/50	205	210	245
311	011/135	295	482	435
011	110/50	358	198	211
355	262/62	008	248	270
111	060/10	115	120	114
228	130/148	245	460	505
175	233/16	168	121	114

Multi-drift Winds

1. TAS = 180 knots

Heading	Drift
130	6°P
070	4°P
190	2°P

W/V 205/18

2. TAS = 150 knots

Heading	Drift
045	3°S
345	6°P
105	8°S

W/V 026/22

3. TAS = 120 knots

Heading	Drift
270	2°S
210	12°S
330	9½°P

W/V 098/30

4. TAS = 165 knots

Heading	Drift
100	2°P
040	14°P
160	12°S

W/V 107/40

Wind Components

1. An airfield has runways 18/36 and 07/25, all of equal length. The TAF W/V is 310/25. Variation is 20°E. Which will be the best R/W for take-off and landing?

RW 25

2. In the Question 1 situation, what will be the head and crosswind components on this runway?

head: 19 cross: 16

3. An aircraft requires 10 knots headwind component for take-off. The crosswind limit for the aircraft is 20 knots. The only runway available is 25. The ATIS W/V is 290/10G40. What are the minimum and maximum wind speeds for take-off?

min: 13 max: 31

4. On a particular take-off, you can accept up to 10 knots tailwind. The runway QDM is 047, the variation is 17°E and the ATIS gives the wind direction as 210. What is the maximum wind strength you can accept?

11 knots

The Navigation Computer