972 F.2d 1353
NOTICE: Federal Circuit Local Rule 47.8(b) states that opinions and orders which are designated as not citable as precedent shall not be employed or cited as precedent.  This does not preclude assertion of issues of claim preclusion, issue preclusion, judicial estoppel, law of the case or the like based on a decision of the Court rendered in a nonprecedential opinion or order.Ronald M. O'BRIEN, Petitioner,v.DEPARTMENT OF THE AIR FORCE, Respondent.
No. 92-3250.
United States Court of Appeals, Federal Circuit.
June 5, 1992.

Before RICH, PAULINE NEWMAN and MICHEL, CIRCUIT JUDGES.
DECISION
PER CURIAM.


1
Ronald M. O'Brien petitions for review of the November 20, 1991 award of the arbitrator in FMCS File No. 91-24396 (Grievance No. 91-129), denying O'Brien's grievance.   We affirm.

DISCUSSION

2
The arbitrator sustained the agency's removal of O'Brien for assaulting a supervisor, finding that the agency established the fact of the assault by a preponderance of credible evidence.   O'Brien does not allege any legal error, but contends that the arbitrator "erred in analyzing the testimony of the witnesses."   As the allegations of his informal brief make clear, O'Brien's petition is primarily a challenge to the arbitrator's credibility determinations.   Such determinations of a presiding official are "virtually unreviewable" by this court.   Hambsch v. Department of the Treasury, 796 F.2d 430, 436 (Fed.Cir.1986).   We may not overturn the arbitrator's award, sustaining the agency's removal of O'Brien, unless we find it to be arbitrary, capricious, an abuse of discretion, contrary to law, or unsupported by substantial evidence.   See 5 USC 7703(c);  5 USC 7121(f) (section 7703 applies to arbitrator's award as if decided by Merit Systems Protection Board).   We see no such error in this case.

