Sextant skills

[zoidberg]

I’m still in awe of your claims in post 60. I can manage just fine doing 2, sometimes 3 LoP per day at 6kts but find it incomprehensible that you could update fixes, when pushed, every 10-12 minutes while flying at several hundred knots. Respect ?
How did you maintain the DR? Plane sailing (or should that be Plane Flying ?)?

First of all, your aged correspondent was but one of several hundred, and so lowly he was not even on the 'totem pole'. In that age , all RAF trainee navigators went through two intensive 'nav courses'. The second one was almost entirely astro.

Next the aircraft mentioned had TWO periscopic sextants, and one could set-up precomputed azimuths and elevations; then it was A:B:A:B:A ( for example ). Next, there were 5 crew. Typically, there were two navs, two pilots, and 'the other guy'. An astro navex was very much a team sport - the Nav-Radar would set up and take the sights, the captain would hand-fly the beast to iron out the cyclic motions that the autopilot couldn't; the co-pilot would call the timing and watch all the little needles in the little round gauges; the Nav-Plotter would precompute the sights, calculate/apply the various corrections ( 'fiddle factors' ), plot the resultant fix or LOPs, and feed in the new position and tracking corrections to the analogue DR computer. 'The other guy' or Air Electronics Officer did strange things with switches, fuse boxes, relays, etc. that no-one else quite understood.... and passed around the aircrew rations/Mars Bars at suitable intervals.

There were many 'fiddle factors', as a really close look at some of the pages of the Air Almanac would suggest. These included e.g. 'acceleration corrections' - longitudinally and laterally - where the 'Pendulous Reference' ( 'bubble' ) in the sextant was influenced by small changes in airspeed and heading. Judging those really well was one of the skills 'separating the wheat from the chaff', that the 'Murricains didn't quite get.

Three-LOP fixing was quite easy, but used mostly by 'the truckies' flogging across oceans. Two-position line fixing A:B:A:B:A or A:B:A:B:A:B:A done continuously was preferred.
Where the two Stars Selected were alternately on the beam and ahead/astern, one could use the resultant info sequentially as a series of Single LOPs, giving alternately Cross-Track Error and Along-Track ( Timing )/ DTG Error, as in A:A:A then B:B:B, precomputed around the central time. The Periscopic Sextant averaged, say, 30 readings in a 1-minute run. One also got a 'compass check' from the star's azimuth each time, logged and considered at required intervals.

The best crews selected for NATO Bombing Competitions were able to select and 'tweak' some of their items of equipment, such as watches and peri-sextants. That involved, of course, the instrument technicians on the base.

So it was very much a team game.

We Brits were very, very good at this - until the Russkies spoiled the game by building interceptors that could get up high enough.....

 

[Buck Turgidson]

First of all, your aged correspondent was but one of several hundred, and so lowly he was not even on the 'totem pole'. In that age , all RAF trainee navigators went through two extensive 'nav courses'. The second one was almost entirely astro.

Next the aircraft mentioned had TWO periscopic sextants, and one could set-up precomputed azimuths and elevations; then it was A:B:A:B:A ( for example ). Next, there were 5 crew. Typically, there were two navs, two pilots, and 'the other guy'. An astro navex was very much a team sport - the Nav-Radar would set up and take the sights, the captain would hand-fly the beast to iron out the cyclic motions that the autopilot couldn't; the co-pilot would call the timing and watch all the little needles in the little round gauges; the Nav-Plotter would precompute the sights, calculate/apply the various corrections ( 'fiddle factors' ), plot the resultant fix or LOPs, and feed in the new position and tracking corrections to the analogue DR computer. 'The other guy' or Air Electronics Officer did strange things with switches, fuse boxes, relays, etc. that no-one else quite understood.... and passed around the aircrew rations/Mars Bars at suitable intervals.

There were many 'fiddle factors', as a really close look at some of the pages of the Air Almanac would suggest. These included e.g. 'acceleration corrections' - longitudinally and laterally - where the 'Pendulous Reference' ( 'bubble' ) in the sextant was influenced by small changes in airspeed and heading. Judging those really well was one of the skills 'separating the wheat from the chaff', that the 'Murricains didn't quite get.

Three-LOP fixing was quite easy, but used mostly by 'the truckies' flogging across oceans. Two-position line fixing A:B:A:B:A or A:B:A:B:A:B:A done continuously was preferred.
Where the two Stars Selected were alternately on the beam and ahead/astern, one could use the resultant info sequentially as a series of Single LOPs, giving alternately Cross-Track Error and Along-Track ( Timing )/ DTG Error, as in A:A:A then B:B:B, precomputed around the central time. The Periscopic Sextant averaged, say, 30 readings in a 1-minute run. One also got a 'compass check' from the star's azimuth each time, logged and considered at required intervals.

The best crews selected for NATO Bombing Competitions were able to select and 'tweak' some of their items of equipment, such as watches and peri-sextants. That involved, of course, the instrument technicians on the base.

So it was very much a team game.

We Brits were very, very good at this - until the Russkies spoiled the game by building interceptors that could get up high enough.....

On the kipper fleet in the 90's we still did the odd astro exercise but I can't comment on the accuracy. The AEO didn't need to fiddle with fuses though, that was my job as the Air Eng ?

 

[zoidberg]

Further, we tended to use Lamberts Conformal charts, sometimes oriented around the major track e.g. RAF Lincolnshire to Gander, or RAFL to Bahrain, or Murmansk....We all had to learn the benefits and limitations of several chart projection concepts. A little lateral thinking will expose why conventional Mercator charts were not always optimum.

That 'golden age of astro' passed abruptly. Someone somewhere ( probably a Canberra recce crew ) discovered that the PVO-STRANY had Mig-21s that could get up to the Vulcans at height - and that wasn't welcome news. A 'signal' was sent by Their Airships and, overnight, the V-Force went low-level. Hobson's choice....
The Valiant couldn't hack it. It broke with the multiplied stresses. The beautiful Victor was given other roles, which it performed magnificantly for decades. That left the great big lumbering over-powered Vulcan to learn to bounce around down at zilch feet over the endless MittelEuropean forests and the northern cold deserts. And that wasn't fun for the 'guys in the back'.

There was half a benefit. The Mig-21s 'probably' couldn't get a missile or guns solution on a Vulcan evading down at less than 50 feet agl. Not until the 'Iron Triangle' had to lift clear of any vertical obstruction - like a hill. Good ol' fashioned map reading became VIP again, to find the hollows and bumps that could help. But that was very much 'on the defensive'....

If you were bounced, you were unlikely to walk away.

Mind you, the opposition had its weaknesses, too. It 'emerged' that the Mig-21 had a number of limitations. One was that its gunsight gyro toppled at about 2 1/4 Gs. And it had an 'aft C of G' problem, in that it couldn't use more than 'about 2/3 fuel load' before it could no longer be kept balanced in flight. So if one could out-turn the bugr by pulling 3G or more, and continue doing that at serious low level, he'd run to his limiting fuel load and have to bug out. Same thing at high level, except way up there the MiGs could stand off and pop missiles - which is what they were designed to do.

The perceptive would have worked out that the Vulcans would need rather good topographic charts to find their way from here to there - wherever 'there' was - and getting the pics for such charts fell to the very capable recce Canberra crews. That became a dangerous job, and a good handful of crews and airframes didn't come back. Garry Powers wasn't the only one....

How did we find out about the Mig-21's limitations? Around that time, the Syrian Air Force had British jet fighters and it was Brit ex-military flying instructors who were employed to teach the Syrians 'the job'. at SAAF Nayrab. When they bought MiG-21s, the Russkies ran a 'conversion to type' course for the new hot ships; all resident flying instructors did the course, and that included several ex-Fleet Air Arm Hunter jocks. ( No, I didn't know either ) Those guys were certainly not blurry irriots. What they learned was swiftly fed back.

It mattered.

 

[zoidberg]

On the kipper fleet in the 90's we still did the odd astro exercise but I can't comment on the accuracy. The AEO didn't need to fiddle with fuses though, that was my job as the Air Eng ?

Ah, yes, the rightly-famous 'kipper fleet' of AvRo Shacklebombers.... famed in song and story.

They had a long wire sometimes trailing out the back. I'm reliably informed that that was for the 'mackerel spinner'.....
They didn't climb to operating altitude after take off at RAF St Mawgan. They trundled along the huge runway, fell off the cliff at the end, then descended to the height they wanted.
They were so slow that they used to tack downwind to improve their VMG.
They didn't have airspeed indicators or clocks fitted in the instrument panel, but calendars.
They didn't bother with sending flight plans. They took so long that they sent post cards instead, on departure, announcing when they'd likely be back.

 

[Beneteau381]

First of all, your aged correspondent was but one of several hundred, and so lowly he was not even on the 'totem pole'. In that age , all RAF trainee navigators went through two intensive 'nav courses'. The second one was almost entirely astro.

Next the aircraft mentioned had TWO periscopic sextants, and one could set-up precomputed azimuths and elevations; then it was A:B:A:B:A ( for example ). Next, there were 5 crew. Typically, there were two navs, two pilots, and 'the other guy'. An astro navex was very much a team sport - the Nav-Radar would set up and take the sights, the captain would hand-fly the beast to iron out the cyclic motions that the autopilot couldn't; the co-pilot would call the timing and watch all the little needles in the little round gauges; the Nav-Plotter would precompute the sights, calculate/apply the various corrections ( 'fiddle factors' ), plot the resultant fix or LOPs, and feed in the new position and tracking corrections to the analogue DR computer. 'The other guy' or Air Electronics Officer did strange things with switches, fuse boxes, relays, etc. that no-one else quite understood.... and passed around the aircrew rations/Mars Bars at suitable intervals.

There were many 'fiddle factors', as a really close look at some of the pages of the Air Almanac would suggest. These included e.g. 'acceleration corrections' - longitudinally and laterally - where the 'Pendulous Reference' ( 'bubble' ) in the sextant was influenced by small changes in airspeed and heading. Judging those really well was one of the skills 'separating the wheat from the chaff', that the 'Murricains didn't quite get.

Three-LOP fixing was quite easy, but used mostly by 'the truckies' flogging across oceans. Two-position line fixing A:B:A:B:A or A:B:A:B:A:B:A done continuously was preferred.
Where the two Stars Selected were alternately on the beam and ahead/astern, one could use the resultant info sequentially as a series of Single LOPs, giving alternately Cross-Track Error and Along-Track ( Timing )/ DTG Error, as in A:A:A then B:B:B, precomputed around the central time. The Periscopic Sextant averaged, say, 30 readings in a 1-minute run. One also got a 'compass check' from the star's azimuth each time, logged and considered at required intervals.

The best crews selected for NATO Bombing Competitions were able to select and 'tweak' some of their items of equipment, such as watches and peri-sextants. That involved, of course, the instrument technicians on the base.

So it was very much a team game.

We Brits were very, very good at this - until the Russkies spoiled the game by building interceptors that could get up high enough.....

Ah, the "telegraph poles" parked around our base with the extremely crude "chicken wire" square emitters that guided them? Surprisingly accurate I believe?

 

[Skylark]

Many thanks, @zoidberg I could read your amusing but informative and entertaining posts all day long.

A few years ago, I was near Barton Airfield (Manchester) and caught the wonderful sight and sound of a very low flying Vulcan as it did a fly by during its farewell tour.

Respect, kind sir.