Citation X (C750)
Flight Crew Air Transport Pilot (ATP)
Training / Qualification; Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
General Release Refused / Aircraft Not Accepted; General Maintenance Action
Procedure; Incorrect / Not Installed / Unavailable Part; Aircraft
On post flight we discovered another compass deviation; a compass card blank with all corrections erased and blank. There also was no compass deviation date or data located on card. It was highly unusual. This was the second WiFi aircraft with a problem; the other aircraft had a compass deviation of 45 degrees and was written up accordingly. Both aircraft will require compass rose swing. With two problems with compasses on WiFi aircraft in one tour I am checking all WiFi aircraft for problems and correct deviation data.
The Reporter stated that the aircraft in question displayed about a 25 degree standby compass deviation with no compass card correction after an in flight WIFI system installation. A standby compass swing was not conducted after the modification which included two antennas; one under the flight station forward electronic equipment bay and one near the tail; plus a control box in an aft section compartment near the aft lavatory. A fifty foot wire connects the forward antenna under the forward equipment bay to the aft control box. The distance between the antenna and the standby compass is about 4-5 FT. The two modified aircraft this Reporter has flown both display about a 25 degree error on the ground and in flight although the WIFI does not become operational until climbing through 10;000 FT. A non WIFI equipped aircraft flown the day following this event had a compass calibration card with only minor corrections unlike the WIFI modified aircraft which had no compass calibration card and about a 25 degree error. The Reporter talked with his Chief Pilot about this and was not given a satisfactory answer about the compass error and lack of calibration. When asked if a new aircraft weight and balance was completed because of the additional weight; the Chief Pilot answered affirmatively. But when asked about a compass swing he answered it was not necessary. The Reporter thought otherwise.
A CE-750 Standby Compass error of approximately 25 degrees was not recorded on the Compass Card after a WIFI system installation.