The only problem might be reaction time. The helo might be long gone by the time you have kindled the inner tube and generated enough smoke to signal. Something quicker might be a smoke flare. I have carried some about the size of a 35mm can, very easy to have on hand. Smoke is superb for indicating the local wind direction at the LZ, if that is a consideration.

What really works best of all in the daytime is a signal mirror; quick to use and unmistakable.