Engine power loss.

Attributes
ACN	97333
Time
Date	198811
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sjc
State Reference	CA
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tower : sjc
Operator	general aviation : instructional
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	climbout : intermediate altitude climbout : takeoff
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 5100 flight time type : 200
ASRS Report	97333
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

I was taking off from sjc airport after a normal runup. Takeoff was accomplished from runway 20L with a left downwind departure to sns. Tower requested I execute a left turn as soon as possible, which was initiated at approximately 300' MSL. As I turned downwind at 600' AGL the engine suddenly dropped from 2550 RPM to 2150 RPM and a steady miss prevailed. I requested immediate landing from tower and was instructed to follow a jet on 3 mi final. I explained the problem and requested to turn inside the jet and land on runway 30R. Tower granted the request and a normal landing followed. A runup was made once I was on the ground and everything appeared normal. The aircraft was left at sjc until a cause for the malfunction can be determined. Callback conversation with reporter revealed the following: reporter states aircraft had been sitting for some time prior to flight. Each runup was fine. Maintenance investigation indicates probably a sticking valve caused problem. Just one cylinder affected. Flown since and performs well. Reporter feels tower did not accept severity of problem. He had to come up with sensible action of crossing to runway 30R rather than follow a jet on 3 mi final.

Original NASA ASRS Text

Title: ENGINE POWER LOSS.

Narrative: I WAS TAKING OFF FROM SJC ARPT AFTER A NORMAL RUNUP. TKOF WAS ACCOMPLISHED FROM RWY 20L WITH A LEFT DOWNWIND DEP TO SNS. TWR REQUESTED I EXECUTE A LEFT TURN AS SOON AS POSSIBLE, WHICH WAS INITIATED AT APPROX 300' MSL. AS I TURNED DOWNWIND AT 600' AGL THE ENG SUDDENLY DROPPED FROM 2550 RPM TO 2150 RPM AND A STEADY MISS PREVAILED. I REQUESTED IMMEDIATE LNDG FROM TWR AND WAS INSTRUCTED TO FOLLOW A JET ON 3 MI FINAL. I EXPLAINED THE PROB AND REQUESTED TO TURN INSIDE THE JET AND LAND ON RWY 30R. TWR GRANTED THE REQUEST AND A NORMAL LNDG FOLLOWED. A RUNUP WAS MADE ONCE I WAS ON THE GND AND EVERYTHING APPEARED NORMAL. THE ACFT WAS LEFT AT SJC UNTIL A CAUSE FOR THE MALFUNCTION CAN BE DETERMINED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES ACFT HAD BEEN SITTING FOR SOME TIME PRIOR TO FLT. EACH RUNUP WAS FINE. MAINT INVESTIGATION INDICATES PROBABLY A STICKING VALVE CAUSED PROB. JUST ONE CYLINDER AFFECTED. FLOWN SINCE AND PERFORMS WELL. RPTR FEELS TWR DID NOT ACCEPT SEVERITY OF PROB. HE HAD TO COME UP WITH SENSIBLE ACTION OF XING TO RWY 30R RATHER THAN FOLLOW A JET ON 3 MI FINAL.

Data retrieved from NASA's ASRS site as of August 2007 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.