B757 flight crew reports failure of autopilot to properly maintain airspeed with pitch during the no...

Attributes
ACN	888081
Time
Date	201005
Local Time Of Day	0601-1200
Place
Locale Reference	SNA.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb Takeoff
Route In Use	SID DUUKE TWO
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	First Officer Pilot Not Flying
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Speed All Types

Narrative:

During takeoff out of sna (weight 187;000) with a normal rotation to approximately 21 degrees; just like briefed; LNAV engaged at 400 ft; autopilot at 500 ft; and VNAV approximately 100 ft late; with climb page edited to 156/3000. I noticed airspeed decreasing rapidly with the power change to climb 2 and the nose of the aircraft not lowering as it should. With airspeed now approaching V2; I advised pilot flying of situation and the autopilot was disengaged and the nose pushed over. Airspeed went to approximately 121 KTS during this process; airspeed was regained and the rest of the departure went normally. I think this particular departure is far too dynamic for the autopilot to be engaged at 500 ft. Change engagement altitude of the autopilot to a point after 854 ft on profile.

Original NASA ASRS Text

Title: B757 Flight Crew reports failure of autopilot to properly maintain airspeed with pitch during the noise abatement departure from SNA. The autopilot was turned off and the nose aggressively pushed over to regain airspeed.

Narrative: During takeoff out of SNA (weight 187;000) with a normal rotation to approximately 21 degrees; just like briefed; LNAV engaged at 400 FT; autopilot at 500 FT; and VNAV approximately 100 FT late; with climb page edited to 156/3000. I noticed airspeed decreasing rapidly with the power change to climb 2 and the nose of the aircraft not lowering as it should. With airspeed now approaching V2; I advised pilot flying of situation and the autopilot was disengaged and the nose pushed over. Airspeed went to approximately 121 KTS during this process; airspeed was regained and the rest of the departure went normally. I think this particular departure is far too dynamic for the autopilot to be engaged at 500 FT. Change engagement altitude of the autopilot to a point after 854 FT on profile.

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.

B757 flight crew reports failure of autopilot to properly maintain airspeed with pitch during the noise abatement departure from sna. The autopilot was turned off and the nose aggressively pushed over to regain airspeed.