When a VHS video recorder is placed in the record mode over an existing recording, the full-track erase head starts erasing all of the information on the tape, including the video tracks.
This portion of partial tracks is equal to the linear width of the helical-scan tracks because the full-track erase head produces a vertical, 90-degree erasure on the videotape across the slanted (about 6 degrees) field tracks.
When the recorder has a flying erase head, the underlying hi-fi audio information will be erased just ahead of the hi-fi audio-recording process and the new information will be recorded properly.
When a VHS recorder is placed in the record mode over an existing recording, the underlying control-track information is erased by both the full-track erase head and the control-track record head.
The longer test overrecordings were of sufficient length to completely erase the portion of the videotape between the full-track erase head and the beginning of the helical-scan heads (the pre-video erased area) (see Figure 3); whereas the short overrecordings did not completely erase that segment.
This VCR has a flying erase head. This figure is in Adobe Portable Document Format.