Orders to US factories rose by a larger-than-expected amount in July as demand for commercial aircraft, heavy machinery and iron and steel all posted solid gains. The Commerce Department reported Wednesday that new orders increased by 1.3 percent in July, much stronger than the 0.8 percent increase economists had been expecting. The July advance follows an even bigger 2.1 percent increase in June and represents the fifth straight rise in orders. Manufacturers have seen a sharp slowdown in the US economy offset by strong gains in foreign demand, helped by a weaker dollar which makes their products more competitive overseas. The July strength was led by a 28.1 percent jump in commercial aircraft, which rebounded from a 21.3 percent decline in this volatile category in the previous month. Orders in all transportation categories rose by 3.2 percent in July, the best showing in five months. It was the second straight month that orders for motor vehicles rose, increasing by 0.6 percent in July following an even bigger 3.2 percent June advance. Excluding transportation, factory orders would have risen by 1 percent, slightly below the 1.5 percent economists had been expecting. Orders for durable goods, items expected to last at least three years, rose 1.3 percent in July, unchanged from the preliminary estimate the government made last week. Orders for nondurable goods, products such as fuel, food and chemicals, increased 1.2 percent in July. Demand for iron and steel jumped 5 percent, orders for machinery rose 4.1 percent with demand for construction machinery soaring 17.9 percent.