HS125 flight crew on a ferry flight reported experiencing flight anomalies created by an unfastened ...

Attributes
ACN	1359125
Time
Date	201605
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	HS 125 Series
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Cowling/Nacelle Fasteners Latches
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

Narrative:

Aircraft experienced gradual; uncommanded left roll/yaw at 16;000 ft and 300 KIAS; level flight; while vectored direct for the arrival. Continuous light vibration felt throughout airframe. Slip/skid (ball) indicator displaced completely to the left of center (unusual for a left yaw situation). No unusual engine or flight control malfunctions or abnormalities indicated on the mfd/pfd/mws.slowed to 250 KIAS; disengaged auto pilot (ap)/ yaw damper (yd); and centered the ball by displacing rudder trim 2 indications to the left. Coordinated diversion with ATC. Aircraft remained stable with rudder trim 2 indications to the left; rudder pedals difficult to move as if yaw damp still engaged; and vibrations still noticeable. Flew stable visual approach. ATC arranged for emergency vehicles to be on standby. Landed with no complications.on post flight; discovered a fastener on the leading edge of an accessory panel; on the underside of the left engine pylon; became loose and allowed for the leading edge of the panel to be forced aft. Although it was understandable that the panel could cause the aircraft to yaw left; it was confusing as to why the slip/skid (ball) indication was indicating to step on the left pedal and add left trim. Notified acp; maintenance and steward on duty.

Original NASA ASRS Text

Title: HS125 flight crew on a ferry flight reported experiencing flight anomalies created by an unfastened panel on the engine pylon.

Narrative: Aircraft experienced gradual; uncommanded left roll/yaw at 16;000 ft and 300 KIAS; level flight; while vectored direct for the Arrival. Continuous light vibration felt throughout airframe. Slip/skid (ball) indicator displaced completely to the left of center (unusual for a left yaw situation). No unusual engine or flight control malfunctions or abnormalities indicated on the MFD/PFD/MWS.Slowed to 250 KIAS; disengaged Auto Pilot (AP)/ Yaw Damper (YD); and centered the ball by displacing rudder trim 2 indications to the left. Coordinated diversion with ATC. Aircraft remained stable with rudder trim 2 indications to the left; rudder pedals difficult to move as if Yaw Damp still engaged; and vibrations still noticeable. Flew stable visual approach. ATC arranged for emergency vehicles to be on standby. Landed with no complications.On post flight; discovered a fastener on the leading edge of an accessory panel; on the underside of the left engine pylon; became loose and allowed for the leading edge of the panel to be forced aft. Although it was understandable that the panel could cause the aircraft to yaw left; it was confusing as to why the slip/skid (ball) indication was indicating to step on the left pedal and add left trim. Notified ACP; maintenance and steward on duty.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.