THE FO OF A DC10-30; DURING DEP FROM GATWICK; EXPERIENCED AN ALT EXCURSION AND ATTRIBUTED IT TO AN 'UNREASONABLE' NOISE ABATEMENT PROC.

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DC10-30; NEAR GROSS; FOR RWY. OPTIMUM FLAPS FOR TKOF (10.5 DEGS) AND MAX THRUST. ATIS RPTED WINDSHEAR ON FINAL AND RPTS OF SEVERE TURB BELOW 6000 FT. GND CONDITIONS AT THE TIME WERE LIGHT TO OCCASIONAL MODERATE RAIN SQUALLS WITH FAST-MOVING CLOUDS. MOVEMENT SURFACES; INCLUDING RWY; WERE WET. PWR WAS RUN UP AND STABILIZED BEFORE TKOF. LONG TKOF ROLL WITH TWO VERY SMALL HESITATIONS IN AIRSPD INCREASE. ACFT DID NOT ROTATE OR CLB ENTHUSIASTICALLY DUE TO WT; WIND; AND SHALLOW FLAP SETTING. THIS IS A NOISE ABATEMENT DEP (LAWBOURNE 3M). PWR REDUCTION TO CLB THRUST AT 1500 FT AGL; THEN CLB TO 3000 FT AGL; BEFORE RETRACTING FLAPS. AT 2.3 DME; R TURN WAS INITIATED; SPD WAS INCREASING ABOVE V2 + 10 KTS; BUT CLB PERFORMANCE WAS POOR; WINDY; AND ROUGH. FLAPS RETRACTED TO 1 DEGS (TKOF SLATS) CAPT WAS REDUCING AND THEN INCREASING PWR DUE TO FLUCTUATING AIRSPD. ROUGH RIDE. AT ABOUT 2500 FT MSL; SPD AND CLB INCREASED SIGNIFICANTLY. SPD WARNING AND ALT HORN (FOR INTERMEDIATE ALT LEVELOFF AT 3000 FT MSL) NEAR IDLE THRUST; AUTOTHROTTLES OFF. APPARENT STRONG UPDRAFT/WINDSHEAR. REVERSED CLB RATE AT ABOUT APPROX 3400 FT; SPD ABOUT 290 KTS. SLOWED AND RETRACTED TKOF SLATS. CONTINUED CLB AT DEP CTL REQUEST ON RADAR HEADING. ALT EXCURSION CAUSED BY UNREASONABLE REQUIREMENT TO COMPLY WITH NOISE ABATEMENT SID UNDER VERY POOR FLYING CONDITIONS.