We have been developing and evaluating GBAS (Ground Based Augmentation System), which includes VDB (VHF Data Broadcast) system. The VDB system with horizontal polarization generally has a null problem. Therefore we made a stacked array antenna known for a solution of the null problem and installed it at Sendai airport. We conducted flight tests and executed two types of flight procedure. One is a level flight including orbit and arc flight patterns for checking a coverage of VDB, and the other is an approach flight for checking occurence of message error on approach course. The results of flight to check the null problem showed deep nulls were reduced by the stacked array antenna and no message errors were detected in GBAS service area. And the results of approach flight showed message error rate was less than 10^-3.

This paper introduces our GBAS equipments and the flight test results about it.