MD80 first officer experienced minor track deviation when the auto pilot is engaged at six hundred f...

Narrative:

FMS equipped airplane. RNAV departure to the north. After takeoff; navigation engaged at four hundred feet with centered deviation indicator; navigation trk; and normal navigation indications. When autopilot was engaged at six hundred feet; the airplane started an immediate right turn away from the intended RNAV track. The turn was commanded on the FD also. Just as quickly; the airplane banked back to the left and intercepted the outbound track properly. There were no apparent reasons for the 'bobble' and the deviation was not significant. Winds were from the west. I do not believe that engaging the autopilot during the takeoff climb improves the accuracy of RNAV departures. The take off mode is not particularly stable and the airplane acts unpredictable using this new procedure. It is not a good answer to RNAV departure errors.

Original NASA ASRS Text

Title: MD80 First Officer experienced minor track deviation when the auto pilot is engaged at six hundred feet during an RNAV departure. The reporter does not believe that track accuracy is improved by using the autopilot at low altitude in this aircraft.

Narrative: FMS equipped airplane. RNAV departure to the north. After takeoff; NAV engaged at four hundred feet with centered deviation indicator; NAV TRK; and normal navigation indications. When autopilot was engaged at six hundred feet; the airplane started an immediate right turn away from the intended RNAV track. The turn was commanded on the FD also. Just as quickly; the airplane banked back to the left and intercepted the outbound track properly. There were no apparent reasons for the 'bobble' and the deviation was not significant. Winds were from the west. I do not believe that engaging the autopilot during the takeoff climb improves the accuracy of RNAV departures. The take off mode is not particularly stable and the airplane acts unpredictable using this new procedure. It is not a good answer to RNAV departure errors.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	878319
Time
Date	201003
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Night
Aircraft 1
Make Model Name	MD-83
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	SID ZZZ
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	First Officer Pilot Flying
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Track / Heading All Types

MD80 first officer experienced minor track deviation when the auto pilot is engaged at six hundred feet during an RNAV departure. The reporter does not believe that track accuracy is improved by using the autopilot at low altitude in this aircraft.