The effect of forced, opposed air flow on flame spread across shallow n-butanol pools in a narrow tube was studied experimentally. The flame spread was accompanied by pulsations, whose amplitude depended on the opposed air velocity. Dependences of the average flame speed on temperature and the opposed air velocity were obtained. The average flame speed was found to be independent of the liquid depth ahead of the flame within the experimental error. Fourier analysis has shown there are natural frequencies of pulsating of the flame. The effects of modulating frequency of forced, opposed air flow on average flame speed was studied experimentally. Response of the flame to the modulation of the opposed air velocity depends on the modulating frequency. If the modulating frequency is more than the natural frequency of pulsations of the flame then the average flame speed depends on time; at first the average flame speed increases and then gradually the value of speed comes back to the value without modulation. If frequency is close to natural frequencies of flame pulsations then the average flame speed increases.