C172 instructor pilot and student reported the cockpit filled with smoke.

Attributes
ACN	571972
Time
Date	200301
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : aln.airport
State Reference	IL
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : aln.tower
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	other
Flight Plan	None
Person 1
Affiliation	other
Function	instruction : instructor
Qualification	pilot : cfi pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time last 90 days : 100 flight time total : 2000 flight time type : 1500
ASRS Report	571972
Person 2
Affiliation	other
Function	instruction : trainee
Events
Anomaly	aircraft equipment problem : critical other anomaly other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overrode automation flight crew : landed in emergency condition
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

While practicing lazy 8's with a commercial student, smoke developed in the cockpit. We started an immediate return to the airport (aln). We notified the tower of our problem, and the tower declared an emergency. All electrical was shut down and a landing was made on runway 17. We coasted off the runway onto the ramp. A fire truck followed, but after engine shutdown, no further smoke was noted. After mechanics investigated problem, it was found that a valve cover gasket had failed, spraying oil on exhaust manifold, creating the smoke. (Aircraft heating system takes heated air from shroud over exhaust manifold, which caused the smoke in the cockpit.) aircraft was fixed within the hour.

Original NASA ASRS Text

Title: C172 INSTRUCTOR PLT AND STUDENT RPTED THE COCKPIT FILLED WITH SMOKE.

Narrative: WHILE PRACTICING LAZY 8'S WITH A COMMERCIAL STUDENT, SMOKE DEVELOPED IN THE COCKPIT. WE STARTED AN IMMEDIATE RETURN TO THE ARPT (ALN). WE NOTIFIED THE TWR OF OUR PROB, AND THE TWR DECLARED AN EMER. ALL ELECTRICAL WAS SHUT DOWN AND A LNDG WAS MADE ON RWY 17. WE COASTED OFF THE RWY ONTO THE RAMP. A FIRE TRUCK FOLLOWED, BUT AFTER ENG SHUTDOWN, NO FURTHER SMOKE WAS NOTED. AFTER MECHS INVESTIGATED PROB, IT WAS FOUND THAT A VALVE COVER GASKET HAD FAILED, SPRAYING OIL ON EXHAUST MANIFOLD, CREATING THE SMOKE. (ACFT HEATING SYS TAKES HEATED AIR FROM SHROUD OVER EXHAUST MANIFOLD, WHICH CAUSED THE SMOKE IN THE COCKPIT.) ACFT WAS FIXED WITHIN THE HR.

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.