We have various market risk exposures that arise from our ongoing business operations. Market risk is the potential economic loss that may result from adverse changes in the fair value of financial instruments. Our financial results are impacted by changes in interest rates, certain foreign currency exchange rates and commodity prices.
Foreign Currencies
We have manufacturing, sales, and distribution facilities in various locations throughout the world. As a result, we make investments and conduct business transactions denominated in various currencies, including the U.S. dollar, the British pound, the European euro, the Canadian dollar, the Mexican peso, and the Australian dollar. Total annual foreign sales, including foreign export sales, averaged approximately $171.5 million over the last three years. More than half of our foreign sales are to Europe or Canada. Foreign sales represented 12.1% of consolidated net sales in 2010. We estimate a hypothetical 10% adverse change in foreign currency exchange rates relative to the U.S dollar for 2010 would have had an unfavorable impact of $9.7 million on sales and, excluding the $6.4 million non-cash non-tax deductible goodwill charge taken at our Aerospace U.K. Composites reporting unit, a $0.6 million unfavorable impact on operating income. We manage foreign currency exposures that are associated with committed foreign currency purchases and sales and other assets and liabilities created in the normal course of business at the subsidiary operations level. Sometimes we may, through the use of forward contracts, hedge the price risk associated with committed and forecasted foreign denominated payments and rates. Historically the use of these forward contracts has been minimal. We do not use derivatives for speculative or trading purposes.
On February 12, 2009 (the Transfer Date) we completed the transfer of ownership of the 11 SH-2G(A) Super Seasprite helicopters (along with spare parts and associated equipment) to the Company. In accordance with the settlement agreement proceeds from the sale of these items will be shared with the Commonwealth of Australia on a predetermined basis. In connection with sharing sale proceeds, we have agreed that total payments of at least $39.5 million (AUD) will be made to the Commonwealth regardless of sales, with at least $26.7 million (AUD) to be paid by March 2011, and, to the extent cumulative payments have not yet reached $33.1 million (AUD) and $39.5 million (AUD), respectively, additional payments of $6.4 million (AUD) each in March of 2012 and 2013. During 2008, we entered into forward contracts for the purpose of hedging these required payments. These contracts cover $36.5 million (AUD) of the $39.5 million (AUD) required payments. See Note 6, Derivative Financial Instruments, in the Notes to Consolidated Financial Statements for further discussion.
Interest Rates
Our primary exposure to interest rate risk results from our outstanding debt obligations and derivative financial instruments employed in the management of our debt portfolio with interest at current market rates. The level of fees and interest charged on revolving credit commitments and borrowings are based upon leverage levels and market interest rates.
The principal debt facilities are a $275.0 million revolving credit agreement that expires September 20, 2014 and a $42.5 million term loan agreement with a four year-term entered into on October 29, 2008 and amended on September 20, 2010. Total average bank borrowings for 2010 were $98.0 million. The impact of a hypothetical 100 basis point increase in the interest rates on our average bank borrowings would have resulted in a $1.0 million increase in interest expense. Changes in market interest rates would impact interest rates on our Revolving Credit Agreement and Term Loan Agreement. The other facilities, established for foreign operations, are comparatively insignificant in amount.
During the first quarter of 2009, we entered into interest rate swap agreements for the purpose of hedging our eight quarterly variable-rate interest payments on the Term Loan Agreement due in 2010 and 2011. These interest rate swap agreements are designated as cash flow hedges and are intended to manage interest rate risk associated with our variable-rate borrowings and minimize the negative impact on our earnings and cash flows of interest rate fluctuations attributable to changes in LIBOR rates.
In November 2010, we issued $115.0 million convertible unsecured senior notes due on November 15, 2017 in a private placement offering. These notes bear 3.25% interest per annum on the principal amount, payable semiannually in arrears on November 15 and May 15 of each year, beginning on May 15, 2011 and have an effective interest rate of 5.25%.
Commodity Prices
We are exposed to volatility in the price of raw materials used in certain manufacturing operations as well as a variety of items procured by our distribution business. These raw materials include, but are not limited to, aluminum, titanium, nickel, copper and other specialty metals. We manage our exposure related to these price changes through strategic procurement and sales practices.