Experimental aircraft pilot experiences rough running engine while flying in formation.

Attributes
ACN	591484
Time
Date	200308
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 1000
Environment
Weather Elements	Fog
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : zzz.tracon tower : rap.tower
Operator	general aviation : personal
Make Model Name	Experimental
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	VFR
Aircraft 2
Controlling Facilities	tracon : zzz.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 45 flight time total : 1800 flight time type : 1
ASRS Report	591484
Person 2
Affiliation	other
Function	flight crew : single pilot
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : landed in emergency condition flight crew : took precautionary avoidance action
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

On final in a pre-planned formation to land at ZZZ, I pulled carburetor heat on and the motor started to misfire and run very badly. I pushed carburetor heat back in and went to full power. The engine stumbled a little more and almost quit. I pulled carburetor heat and it came up to full RPM. At the time of this emergency, I had to turn 45 degrees off to the right, so I would not overtake the aircraft in the lead. I then did 1 s-turn toward the runway at full power to stay behind the lead aircraft. Because of the high speed and possible engine failure, spacing was adjusted to land safely.

Original NASA ASRS Text

Title: EXPERIMENTAL ACFT PLT EXPERIENCES ROUGH RUNNING ENG WHILE FLYING IN FORMATION.

Narrative: ON FINAL IN A PRE-PLANNED FORMATION TO LAND AT ZZZ, I PULLED CARB HEAT ON AND THE MOTOR STARTED TO MISFIRE AND RUN VERY BADLY. I PUSHED CARB HEAT BACK IN AND WENT TO FULL PWR. THE ENG STUMBLED A LITTLE MORE AND ALMOST QUIT. I PULLED CARB HEAT AND IT CAME UP TO FULL RPM. AT THE TIME OF THIS EMER, I HAD TO TURN 45 DEGS OFF TO THE R, SO I WOULD NOT OVERTAKE THE ACFT IN THE LEAD. I THEN DID 1 S-TURN TOWARD THE RWY AT FULL PWR TO STAY BEHIND THE LEAD ACFT. BECAUSE OF THE HIGH SPD AND POSSIBLE ENG FAILURE, SPACING WAS ADJUSTED TO LAND SAFELY.

Data retrieved from NASA's ASRS site as of July 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.