Jet stream and bombing accuracy

[Hairog]

I know that the jet stream over Japan had a great effect on the strategic bombing of Japan. The vaunted B29 had to fly under it to effectively do it's job there by negating it's altitude advantage.

Is there any website that could give information of other jet stream anomalies that might effect bombing in the Soviet Union?

[Bill Walker]

Since the jet stream rarely descends below 30,000 feet, I don't think any WW2 aircraft would be greatly effected, apart from the B-29 and a few jets.

[Hairog]

I know over Japan the jet stream had a huge effect and kept the B29s below 25000 feet. Are there not other areas where the stream dips down and would greatly effect ultra high level bombing like over Japan?

I've been looking for a map that might assist me but I guess I'm not using the correct search criteria as I can find nothing that can tell me what I seek.

[Kutscha]

There is 4 jet streams.
http://en.wikipedia.org/wiki/File:Jetstreamconfig.jpg

[Hairog]

Thank you Kutscha but that is the kind of general stuff I've been able to find. I need more detailed info on how it might effect say high altitude bombing over Moscow or Vladivostok etc.

[Bill Walker]

The two northern hemisphere jet streams flow west to east. I think part of the reason the B-29s kept low on the way into Japan from the Pacific islands was to avoid the headwind on the inbound leg.

The jet streams do occasionally drop as low as 25,000 feet - at least over North America. I expect it would be similar over the Motherland.

There are two big problems with a conventional bomber encountering the jet stream - en route issues, and bombing accuracy issues.

The jet stream can be quite narrow, less than 100 miles. It wanders around, so it can be hard to forecast if your flight path will ever encounter the stream. With wind speeds roughly equal to cruising speeds of a piston engined bomber, running into a jet stream can have a huge effect on your ground speed and track. You will need to keep a close watch on both ground speed and track, if your equipment allows this. Even half an hour in a jet stream without realizing it can throw you way off course and schedule. You could, in an extreme case, get totally lost, or run out of fuel before completing your mission, or be forced to turn around and head home before reaching your target.

If you are unlucky enough to be tracked on enemy radar, they will see you enter the jet stream almost immediately. If the enemy can coordinate radar plots from several aircraft, the people on the ground could locate the jet stream, and ensure that interceptors used it to their advantage, or at least avoided it. Meanwhile, the bomber flying into a jet stream could be literally hovering on their scopes.

The winds encountered by the bombs after leaving the bomber will of course effect the impact point. Most bomb sights used some method of predicting this effect, but they are based on the assumption that the wind direction remains relatively constant over the drop, and that the wind speed decreases in a smooth, predictable manner as you get lower (the "planetary boundary layer", usually plotted as function of altitude to the 0.7 power). If your bomb spends part of its flight in a jet stream, and part out of the jet stream, all these assumptions go out the window.

If we assume the bomb has a terminal air speed of 600 mph and a drop from 6 miles (to make the numbers easy), the flight time of the bomb is about 0.01 hours, or 0.6 minutes. A worst case error of wind speed might be assuming a forward speed of 250 mph, but getting an actual ground speed of 500 mph. In 0.6 minutes your impact point would be shifted 2.5 miles. This is on top of all the other errors we see in WW2 bombing. (Actually, I think the flight time will be longer, since it will take some seconds for the bomb to reach terminal velocity. So, the bombing error due to wind could be greater than this.)

[drgondog]

There is a lot of evidence as well as presentation directly from Curtis LeMay that the greater motivation to go low and at night was multifold.

1. Japanes industry was largely scattered and less susceptible to 'key' target syndrome (i'e. ball bearing production at Schweinfurt) and therefore less vulnearble to precision bombing - which was not providing very much impact due to the Jetstream effect on bombing accuracy (cross streams at different altitudes increased difficulty in calculating drift)

2. High altitude bombing strained the 3350's increasing engine fires and losses to mechanical causes

3. More susceptible to daylight interception

Further, he reasoned that the Japanese radar guided AA was far less effective than German flak, fire fighting resources inadequate to defend against fire bombing, and fire bombing more effective against distributed cottage industry buried in the citeies.

The rest is history

[Hairog]

I just re-discovered this thread. Thank you all for the information. It will come in handy.