Don’t forget Max that Jim has also found that a number of 6 Group squadrons flying Lancasters were definitely working in mph/statute miles up to the end of the war. The whole of 4 Group was still flying Halifaxes at the time and, unless their ASIs had been modified, they would have been using mph etc.

I don’t think one should take Hoare’s statement as all-embracing – you yourself have just noted you have a navigator’s chart from March 1945 scaled in statute miles.

Trying to summarise what has been written here, and what has appeared in the Lancaster Archive Forum, it seems that at the beginning of the war the ASIs of all Bomber Command’s aircraft, including Lancasters when they started to come on line, were calibrated in mph and forecasts were presented accordingly. There is no doubt that this situation continued until at least March 1944.

At some time during the summer of 1944 some of the later Marks of Lancasters reaching squadrons were equipped with ASIs calibrated in knots. The navigators of these would have no option but to use knots and nautical miles in their calculations, but this was not universal practice since some Lancaster squadrons never converted.

In other words there was a right mixture of procedures – just as well the HSE wasn’t around then.

Brian
PS. Doesn’t anyone know anything about the Halifax?

I think, CD, that it should be remembered that the broadcast winds were not simply for navigation but an attempt to keep the bomber stream together so that it arrived over the target as near as possible in a compact formation.

Although the windfinders were all supposed to be experienced navigators there was, no the less, a considerable scatter in the winds they sent back to HQ Bomber Command via the Groups. The forecasters then had to decide which to disregard then compute a mean from the remainder. This wasn’t for just one level but sometimes 4 or 5 and the time available was limited.

At HQ Bomber Command the found winds were plotted on a vector diagram so the winds that were seriously in error were obvious, but even so there could be quite a spread. I’ve reconstructed one of the vector diagrams using found winds reported on a Berlin raid on the night of 28/29 Jan 1944 to show what I mean. This was before the foun/broadcast wind procedure was introduced and was actually a trail to see if it had merit. The blue Z is the mean wind calculated after the event by the Command Nav Officer.

As a matter of interest on this particular operation one aircraft often reported winds 90 deg different to the others.

It is easy to imagine how, if all the aircraft on an operation depended on their own navigator, the stream would become scattered.

(Hope this works, I’m not used to posting attachments.)
Brian

Graham and Bazv,

Many thanks for your replies.

I’ve done some research on this from a Met Office viewpoint and the raw data on which forecasts were based. At the beginning of the war winds aloft were recorded as kph, but this changed to knots at the beginning of 1944. Logically, as far as the Met Office was concerned, wind speeds would have been forecast in the units in which the raw data were received, but there is no doubt that up to and during the first months of 1944 forecasts were in mph and any references to distance were in statute miles (AIR2/5029).

Forecasts would only have been issued in mph if that was what the customer, Bomber Command, demanded – thus the conversion from kph/knots to mph was done by the Met Office – not the aircrew.

I’m sure that the requirement for speeds to be presented in mph was solely because all the aircraft I listed in the first post of this thread had ASIs reading mph – given the number of restoration projects and specialists on this forum it has been rather disappointing that none of those involved could answer what is really a very simple question.

I’m equally sure, but don’t know, that when the really large raids (in terms of numbers of aircraft) started in 1942 all the ASIs were calibrated in mph but, as you state Graham, in the later Marks of Lancasters this changed to knots. However, did the same happen with the Halifax or did the ASIs remain in mph to the end?

Reading through this I suppose, Graham, I’m really repeating what you’ve already said, but the ramifications are considerable if a couple of navigators erroneously used mph instead of knots, or vice versa, in respect of time on target or ‘simple’ navigation.

Brian