AeroVironment (NASDAQ:AVAV) posted a strong fourth quarter, but provided guidance that requires a little bit of math in order to get to an EPS expectation, which they did not provide.  So lets break down what their guidance meant.  They stated:

"For fiscal year 2011, the Company expects to achieve revenue growth of 10% to 15% over fiscal year 2010, with an operating income margin between 12% and 14%."

On their conference call, they provided more details and advised analysts to use a cautious 35% tax rate because they were not sure whether or not they would receive extended tax credits.  Also, the balance sheet now includes a significant 142M in investments, so we can assume something like a return on those investments for their coming fiscal year.  Let's do the math using the midpoint of the ranges they provided:

12.5% revenue growth on top of 249.5M = apx 281

13% operating income of that = apx 36.5

1.5% investment income from the 142M = 2.1M

That means income before income taxes = 38.6M

With a 35% tax rate, net income = 25.1

With a 22M share count, that yields $1.14 earnings per share, which is slightly below analyst expectations of $1.17.  Although they beat the Q4 analyst estimate by .12, traders in today's after market for AeroVironment were clearly disappointed by the guidance.