  The FLASH L-band (1.3 GHz) superconducting accelerator facility at DESY has a
Low Level RF (LLRF) system that is similar to that envisioned for ILC. This
system has extensive monitoring capability and was used to gather performance
data relevant to ILC. Recently, waveform data were recorded with both beam on
and off for three, 8-cavity cryomodules to evaluate the input RF and cavity
gradient stability and study the rf overhead required to achieve constant
gradient during the 800\mu\s pulses. In this paper, we present the recent
experimental results and discuss the pulse-to-pulse input rf and cavity
gradient stability for both the beam on and off cases. In addition, a model of
the gradient variation observed in the beam off case will be described.
