53 Pa. Stat. § 15923
If, for any reason, the project revenues pledged for the payment of revenue bonds issued under this act shall become insufficient to meet the requirements of the bond ordinance under which such bonds were issued, the chief fiscal officer of the city shall certify such fact and the reasons therefor to the city council and the city council shall then have the power, subject to constitutional debt limitations, to authorize the issuance and sale of general obligation refunding bonds of the city without limitation as to rate of interest and in such principal amount as may be required, together with other available funds, to pay and redeem such revenue bonds including principal, interest to the date fixed for redemption or payment and premium, whether or not the revenue bonds to be refunded shall have matured or are about to mature, and whether or not the principal of or interest on the refunding bonds shall exceed the principal of or interest on the bonds to be refunded. Such refunding bonds may be exchanged for outstanding revenue bonds to be refunded or may be sold in the manner and subject to the terms and conditions, to the extent not inconsistent with this section, as provided by law for the sale of general obligation bonds generally, and the proceeds applied to the purchase, redemption or payment of the revenue bonds to be refunded.
53 P.S. § 15923