Experimental studies on the collective field emission from carbon nanotubes (CNTs) on metallic cathode substrate show wide variability. In this paper, we investigate several related effects, such as the relationship between the electron-phonon transport and the mechanical deformation in the CNTs. A systematically coupled model of randomly oriented CNTs in a thin film is developed. Numerical simulations are reported, which are able to reproduce several experimentally observed phenomena, such as a fluctuating field emission current, deflected CNT tips and the heating process. Examples are shown, where the electrodynamic stretching of the initially deflected CNTs can produce transients in the collective field emission current as large as 10 3 times the usual field emission current. Correspondingly, the tip temperature rises from 303 to 520 K within a time interval of 40 s. A 10 K variability in the maximum temperature is observed over the 0.0144-0.0202 V/nm range of the DC bias electric field. The maximum tensile stress is found to be 1.2 GPa, which is much smaller than the fracture stress. (C) 2008 Elsevier B. V. All rights reserved.