Narrative:

I pulled the carburetor heat on and reduced power to about 1200 RPM to practice a simulated engine failure. We were directly over the big lake airstrip, so I instructed him to make his approach to that field. As he entered left downwind for the east runway, I cleared the engine. I did not clear the engine again during the approach. The student's pattern was wide. When we turned to final at about 500 AGL, we were too far away to make the field. Both the student and I recognized this. I instructed him to initiate a go around. As he was pushing in the throttle, he entered a very shallow right bank. I did not correct the bank or tell the student to do so when I first noticed it. He was an advanced student preparing for his private chkride. I didn't feel I should immediately correct every small error he made. The engine didn't respond to the throttle. When I realized what was happening, I took the controls, corrected the bank and aimed for the only clearing I saw. The airstrip was too far away to be considered as an option. I initiated the restart procedures, but did not complete them. I noticed my airspeed getting too slow and the trees below approaching rapidly. I concentrated my efforts on maintaining best glide speed over the trees to the clearing. The landing gear clipped the tops of the trees just before the clearing. I landed as slowly as possible, tail low. The nose gear hit a berm and collapsed. The aircraft slid on its nose a short distance until it hit another berm and rolled over nose first. We stopped upside down. Neither of us was hurt -- not even a bruise or scratch. The emergency locator transmitter was not automatically activated. Any engine, but particularly the continentals of cessna 150's, needs to be pampered in very cold WX. The temperature in the practice area was 10-15 degrees colder than at the point of departure. I probably had the throttle set too low for those conditions. I've been told since that 1500 RPM is the lowest safe setting in winter. The student told me later that his instructor had always told him to turn off the carburetor heat and then add the power. In warmer climates, that's not a problem. In ak, it is. He may have turned off the carburetor heat before adding power. Another student who had been flying that aircraft later said that it had been running rough and backfiring on touch and goes and gars (he always adds power first and then turns off the carburetor heat). A mechanic who had worked on that airplane said that the idle mixture may have been set too lean.

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Original NASA ASRS Text

Title: THE ENG QUIT WHEN A STUDENT PLT TRIED TO GAR AFTER BOTCHING A SIMULATED ENG EMER.

Narrative: I PULLED THE CARB HEAT ON AND REDUCED PWR TO ABOUT 1200 RPM TO PRACTICE A SIMULATED ENG FAILURE. WE WERE DIRECTLY OVER THE BIG LAKE AIRSTRIP, SO I INSTRUCTED HIM TO MAKE HIS APCH TO THAT FIELD. AS HE ENTERED L DOWNWIND FOR THE E RWY, I CLRED THE ENG. I DID NOT CLR THE ENG AGAIN DURING THE APCH. THE STUDENT'S PATTERN WAS WIDE. WHEN WE TURNED TO FINAL AT ABOUT 500 AGL, WE WERE TOO FAR AWAY TO MAKE THE FIELD. BOTH THE STUDENT AND I RECOGNIZED THIS. I INSTRUCTED HIM TO INITIATE A GAR. AS HE WAS PUSHING IN THE THROTTLE, HE ENTERED A VERY SHALLOW R BANK. I DID NOT CORRECT THE BANK OR TELL THE STUDENT TO DO SO WHEN I FIRST NOTICED IT. HE WAS AN ADVANCED STUDENT PREPARING FOR HIS PVT CHKRIDE. I DIDN'T FEEL I SHOULD IMMEDIATELY CORRECT EVERY SMALL ERROR HE MADE. THE ENG DIDN'T RESPOND TO THE THROTTLE. WHEN I REALIZED WHAT WAS HAPPENING, I TOOK THE CTLS, CORRECTED THE BANK AND AIMED FOR THE ONLY CLRING I SAW. THE AIRSTRIP WAS TOO FAR AWAY TO BE CONSIDERED AS AN OPTION. I INITIATED THE RESTART PROCS, BUT DID NOT COMPLETE THEM. I NOTICED MY AIRSPD GETTING TOO SLOW AND THE TREES BELOW APCHING RAPIDLY. I CONCENTRATED MY EFFORTS ON MAINTAINING BEST GLIDE SPD OVER THE TREES TO THE CLRING. THE LNDG GEAR CLIPPED THE TOPS OF THE TREES JUST BEFORE THE CLRING. I LANDED AS SLOWLY AS POSSIBLE, TAIL LOW. THE NOSE GEAR HIT A BERM AND COLLAPSED. THE ACFT SLID ON ITS NOSE A SHORT DISTANCE UNTIL IT HIT ANOTHER BERM AND ROLLED OVER NOSE FIRST. WE STOPPED UPSIDE DOWN. NEITHER OF US WAS HURT -- NOT EVEN A BRUISE OR SCRATCH. THE EMER LOCATOR XMITTER WAS NOT AUTOMATICALLY ACTIVATED. ANY ENG, BUT PARTICULARLY THE CONTINENTALS OF CESSNA 150'S, NEEDS TO BE PAMPERED IN VERY COLD WX. THE TEMP IN THE PRACTICE AREA WAS 10-15 DEGS COLDER THAN AT THE POINT OF DEP. I PROBABLY HAD THE THROTTLE SET TOO LOW FOR THOSE CONDITIONS. I'VE BEEN TOLD SINCE THAT 1500 RPM IS THE LOWEST SAFE SETTING IN WINTER. THE STUDENT TOLD ME LATER THAT HIS INSTRUCTOR HAD ALWAYS TOLD HIM TO TURN OFF THE CARB HEAT AND THEN ADD THE PWR. IN WARMER CLIMATES, THAT'S NOT A PROB. IN AK, IT IS. HE MAY HAVE TURNED OFF THE CARB HEAT BEFORE ADDING PWR. ANOTHER STUDENT WHO HAD BEEN FLYING THAT ACFT LATER SAID THAT IT HAD BEEN RUNNING ROUGH AND BACKFIRING ON TOUCH AND GOES AND GARS (HE ALWAYS ADDS PWR FIRST AND THEN TURNS OFF THE CARB HEAT). A MECH WHO HAD WORKED ON THAT AIRPLANE SAID THAT THE IDLE MIXTURE MAY HAVE BEEN SET TOO LEAN.

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.