In the second quarter, Apple’s share of the global notebook computer market more than doubled, causing the company to surge from No. 7 to No. 3 in total units shipped.

According to Deutsche Bank and reported by Fortune, Apple made this move on the strength of iPad sales, which Deutsche Bank included as part of the notebook market. Apple sold 2.47 million units of its traditional MacBook laptops in Q2 and the company also sold 3.27 million units of the iPad, which launched on April 3.

Apple still trails notebook market leaders Hewlett-Packard and Acer by a wide margin, but the iPad surge enabled it to leapfrog all of the second-tier notebook vendors – ASUS, Dell, Lenovo, and Toshiba.

Deutsche Bank analyst Chris Whitmore said, “The iPad is directly cannibalizing demand for other vendors’ [notebook] products. Remarkably, Apple’s traditional MacBook business posted accelerated unit growth on a Y/Y basis in 2Q, despite the launch of the iPad, while every other Top 5 vendor slowed.”

As the chart above shows, incumbents Hewlett-Packard, Dell, and Acer have been the vendors losing the most market share during the past year, while Apple has been the largest gainer. Asian vendors ASUS, Lenovo, Samsung, and Sony have also posted modest gains.

Sanity check

Of course, the big issue here is whether the iPad should really be counted as part of notebook/laptop sales. I’d favor breaking out tablets into their own category or at least as a sub-category of notebooks, since a tablet typically gets purchased in addition to a notebook and not as a replacement.

Then, researchers could have both a notebook category and a tablet category (or sub-category), as well as a larger category that included both. We’ve seen similar breakouts done with netbooks, where they can be broken out separately or rolled up into the notebook market totals.

That said, I do know a number of people with iPads who say they are using their notebooks less and less. So it could eventually become a replacement for a notebook purchase in some cases. Tablets may already be a replacement for a second notebook for some people. That was the phenomenon that was driving netbooks in many cases. And, that’s probably why tablets are eating into notebook sales for Apple competitors, according to the Deutsche Bank data.

The other thing to keep in mind is that Apple is the only one of these seven vendors that currently has a low-cost touchscreen tablet on the market. That won’t be the case for long. A year from now, nearly all of these vendors should have competing tablets, powered by either Android or Windows.