Aircraft navigation systems

[PMN1]

From 'Dowding of Fighter Command' by Vincent Orange

Page 112

During a night exercise in 1937, two-thirds of a bomber force failed to find the very large and fully illuminated city of Birmingham. Matters did not improve: during 1938 and 1939, numerous bomber crews simply got lost (earlier on it says that over the space of 24 months from 1936, there had been 478 forced landings by aircrews who had go lost).


Group Commanders and aircrew were aware of the problem so if it had been fully accepted in Bomber Command following the 1937 exercise that there was a problem and a serious look at electronic navigation was made, when is the earliest Bomber Command can have a navigation system with any kind of accuracy?

[PMN1]

From Robin Neillands' 'The Bomber War'

Page 71

The real story (of H2S) begins one day in November 1941, when a Blenheim navigator noticed that when the radar on his AI set was pointed down it gave a very good outline picture of the ground below, showing not only built-up areas but outlines from the coast and features such as woods, lakes and towns in open country. A note was made of this interesting fact, and eventually found its way to TRE. There the possibilities were explored, and the outcome after a great deal of work, was H2S.



If the note had been ignored and there was no H2S, what would be the result of no H2S?

[PMN1]

With Oboe MkIII (introduced April 1944), it seems four aircraft could operate on one frequency, and the system could accommodate approaches other than simple radial ones, what changes to the MkI and II did that require?


With G-H, it was the aircraft carrying the transmitter while the ground station had the transponder, could this approach have been used form the start and so be developed first rather than Oboe?

[PMN1]

RAF Bomber Command 1936-1968 by Chris Ashworth

Page 189

A fixing aid using pulsed range signals from ground transmitters had been invented in 1938 but had remained undeveloped due to lack of funds. In June 1940 work restarted at the TRE and a simple cathode ray tube display giving readings, which could be plotted, on a special navigational grid chart to give an accurate fix was produced. The equipment was enthusiastically reported on a radio aids meeting on 16 October 1940 and a month later Bomber Command requested that Gee be provided for all bombers.

Is the Gee that was developed the system that was invented in 1938?

[curmudgeon]

RAF Bomber Command 1936-1968 by Chris Ashworth

Page 189

A fixing aid using pulsed range signals from ground transmitters had been invented in 1938 but had remained undeveloped due to lack of funds. In June 1940 work restarted at the TRE and a simple cathode ray tube display giving readings, which could be plotted, on a special navigational grid chart to give an accurate fix was produced. The equipment was enthusiastically reported on a radio aids meeting on 16 October 1940 and a month later Bomber Command requested that Gee be provided for all bombers.

Is the Gee that was developed the system that was invented in 1938?

Don't know - GEE was straightforward but took a long time to be implemented. There was VERY strong resistance in Bomber Command to the use of electronic aids. It took the Lindemann/Butt analysis of aiming point flash photos to prove dead reckoning and astro-nav just didn't work. RV Jones (Most Secret War ... section on 'Jay') provides a (very nearby) outsider's view of the introduction of aids ... he had worked on jamming the German aids in 1940/41 so had a strong professional interest. Contemporaneously Blackett and Braddick also developed the Mk XIV bombsight - halving the linear bomb spread from the aiming point meant you would need 1/4 the bombers!
There is a history of GEE at http://www.lancaster-archive.com/bc_gee.htm - Dippy (the 1937 man) produced GEE, so I expect it was the same system, perhaps with tweaking

[PMN1]

There is a history of GEE at http://www.lancaster-archive.com/bc_gee.htm - Dippy (the 1937 man) produced GEE, so I expect it was the same system, perhaps with tweaking


That's the impression I have got form looking at other sites.

[PMN1]

It took the Lindemann/Butt analysis of aiming point flash photos to prove dead reckoning and astro-nav just didn't work.

Perhaps sooner..

The Bomber War by Robin Neillands

Page 64

Before a problem can be solved, it must be recognised and accepted as real, rather than seen as an excuse for failure. There is plenty of evidence that the crews and chiefs of Bomber Command, quite early on in the war and long before the Butt Report, were well aware that they were not seriously damaging German industry. Indeed, one of the points raised by Richard Pierse, when he replied to Portal’s Directive of 25 October 1940 – a year before Butt – was that ‘on long range attacks only one out of every five aircraft despatched actually reaches the target’. This figure was revised by a conference of the Bomber Command group navigation officers at High Wycombe, the Bomber Command HQ, three weeks later, when they reached the conclusion that at best only about 35 per cent of bombers actually despatched actually reached their primary targets.

[curmudgeon]

Perhaps sooner..

The Bomber War by Robin Neillands

Page 64

Before a problem can be solved, it must be recognised and accepted as real, rather than seen as an excuse for failure. There is plenty of evidence that the crews and chiefs of Bomber Command, quite early on in the war and long before the Butt Report, were well aware that they were not seriously damaging German industry. Indeed, one of the points raised by Richard Pierse, when he replied to Portal’s Directive of 25 October 1940 – a year before Butt – was that ‘on long range attacks only one out of every five aircraft despatched actually reaches the target’. This figure was revised by a conference of the Bomber Command group navigation officers at High Wycombe, the Bomber Command HQ, three weeks later, when they reached the conclusion that at best only about 35 per cent of bombers actually despatched actually reached their primary targets.

note the 'creep' ... an anecdotal one-in-five mysteriously improves to '35%' ... It is clear that the upper levels of the command believed their own propaganda about long range navigation and pin-point hits (Portal targets). It was only with Lindemann/Butt that the War Cabinet put the word on the RAF to fix it, with the implicit alternative of career termination.
In the pre war period the RAF rejected technical means and lauded the spirit and competence of aircrew. Which didn't hold up in either Fighter Command or Bomber Command once combat was joined.

[PMN1]

note the 'creep' ... an anecdotal one-in-five mysteriously improves to '35%' ... It is clear that the upper levels of the command believed their own propaganda about long range navigation and pin-point hits (Portal targets). It was only with Lindemann/Butt that the War Cabinet put the word on the RAF to fix it, with the implicit alternative of career termination.
In the pre war period the RAF rejected technical means and lauded the spirit and competence of aircrew. Which didn't hold up in either Fighter Command or Bomber Command once combat was joined.


When he became C-in-C, Bomber Command in 1937 Edgar Ludlow-Hewitt toured his command and produced a report on his findings that discussed the command’s ability to do what it was supposed to do – it was apparently not good reading.

He also wrote in 1939 another report “Readiness For War” which again gave a bleak view of Bomber Command’s capabilities.

He was moved in 1940 to Inspector General, don't know if that is/was considered a place to stick annoying people.

Never actaully seen the full reports but from what i understand they were distressingly accurate.

[Lightning]

Hi PMN1 and curmudgeon,

I am not surprised that, using dead reckoning navigation at night, only 20% - 35% of the bombers reached their distant targets. Without visible landmarks by which to make corrections ("pilotage navigation"), dead reckoning alone is terribly inaccurate--and that inaccuracy increases with distance.

Dead reckoning looks good on paper: Draw a line on a chart; measure its distance; apply magnetic variation and deviation to arrive at compass course; use winds-aloft reports/forcasts to figure wind correction angle and ground speed. Then all you have to do is fly the calculated compass heading at the proper indicated airspeed for the calculated time, and you're over your destination.

The only problem is that compasses, airspeed indicators, and winds-aloft reports all have inaccuracies--sometimes significant ones. Also, pilots have to maintain the compass heading "spot-on"--easier said than done over long periods of time. If course changes enroute are planned, things get even more complicated.

I've proven this to myself on several occasions. After doing all of the above, I would go out and fly the course. While keeping track of my position by ground reference, I would hold my heading and airspeed and fly the clock exactly as planned, regardless of the results. At my calculated ETA, I would mark my position on the sectional chart. Sometimes it was astounding how far off I was, and I can't think of even one time where I was exactly where I should have been.

Modern flight training stresses the use of electronic navigational aids, but the novice pilot better sharpen his map-reading, dead reckoning, and pilotage skills in preparation for that inevitable power failure in his airplane.

Regards,

Lightning

[Kutscha]

Reminds me a story my Dad once told me Lightning.

During WW2 for a time he was stationed at Summerside with No. 1 GRS. He was the radio operator for the trainee navigator. These were long boring flights out over the Gulf of St Lawrence and to break the monotony the pilot would let him fly the Anson. Other crews did the same. The trainee navigators preferred the non pilot flying the a/c as they would hold the heading better than the pilot.

[Lightning]

Hi Kutscha,

Reminds me a story my Dad once told me Lightning.

During WW2 for a time he was stationed at Summerside with No. 1 GRS. He was the radio operator for the trainee navigator. These were long boring flights out over the Gulf of St Lawrence and to break the monotony the pilot would let him fly the Anson. Other crews did the same. The trainee navigators preferred the non pilot flying the a/c as they would hold the heading better than the pilot.

That's pretty good. I would imagine that the reason was that the non-pilots, being more aware of their piloting limitations, paid stricter attention to what they were doing and took less for granted than the experienced pilots.

For a long while (and maybe still), the accident rate among student pilots and low-time licensed pilots was lower than among pilots having considerably more experience. They (the beginners) knew they had a lot to learn; the "experienced" pilots thought they had already learned it.

Regards,

Lightning

[Kutscha]

Hi Kutscha,
That's pretty good. I would imagine that the reason was that the non-pilots, being more aware of their piloting limitations, paid stricter attention to what they were doing and took less for granted than the experienced pilots.

Be sure

For a long while (and maybe still), the accident rate among student pilots and low-time licensed pilots was lower than among pilots having considerably more experience. They (the beginners) knew they had a lot to learn; the "experienced" pilots thought they had already learned it.

I have read that around 500hr flight time is the most dangerous time.

Regards,

Lightning

Wild and crazy youth. Another story he told was of an Anson crashing landing after just lifting off. A non pilot was at the controls and the a/c hit some seagulls. The base commander was not pleased, to say the least. This impromptu flight school was very quickly terminated.