B737-300 crew landing without clearance, after the stabilizer trim failed in the nose down direction...

Attributes
ACN	641466
Time
Date	200412
Day	Mon
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	msl single value : 6600
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : den.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 250 flight time total : 12000 flight time type : 7700
ASRS Report	641466
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical incursion : landing without clearance non adherence : far non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : stab trim wheel other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew other other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

Everything normal up to this point. At 1200 ft AGL, I called for flaps 30 degrees. Nose down main electric trim failed. Nose up available. Used manual trim to adjust pitch. Continued to landing. Landing was a safer decision instead of going around and dealing with numerous flap/pitch changes with only manual trimming nose down available. Airplane was stable. During this time, I remember hearing from approach 'cleared for the visual runway 16L.' I do not remember hearing instructions to switch to tower. I did respond at the 1000 ft call 'cleared to land.' I failed to follow my technique of verifying I heard cleared to land because I was very focused on 'flying the airplane.' still no excuse, but truthful reason. After landing, first officer said he tried to contact ground and was on correct frequency, no answer. Ramp told us to call den ground control. Den ground gave a phone number. I called, realized we might not have received 'cleared to land.' I did explain I was dealing with a flight control problem. During taxi in, I was testing main electric trim at each flap setting, nose up and nose down on the lower right side of the pedestal where the takeoff warning horn is installed. Wrote up main electric trim. Maintenance took plane OTS.

Original NASA ASRS Text

Title: B737-300 CREW LWOC, AFTER THE STABILIZER TRIM FAILED IN THE NOSE DOWN DIRECTION.

Narrative: EVERYTHING NORMAL UP TO THIS POINT. AT 1200 FT AGL, I CALLED FOR FLAPS 30 DEGS. NOSE DOWN MAIN ELECTRIC TRIM FAILED. NOSE UP AVAILABLE. USED MANUAL TRIM TO ADJUST PITCH. CONTINUED TO LNDG. LNDG WAS A SAFER DECISION INSTEAD OF GOING AROUND AND DEALING WITH NUMEROUS FLAP/PITCH CHANGES WITH ONLY MANUAL TRIMMING NOSE DOWN AVAILABLE. AIRPLANE WAS STABLE. DURING THIS TIME, I REMEMBER HEARING FROM APCH 'CLRED FOR THE VISUAL RWY 16L.' I DO NOT REMEMBER HEARING INSTRUCTIONS TO SWITCH TO TWR. I DID RESPOND AT THE 1000 FT CALL 'CLRED TO LAND.' I FAILED TO FOLLOW MY TECHNIQUE OF VERIFYING I HEARD CLRED TO LAND BECAUSE I WAS VERY FOCUSED ON 'FLYING THE AIRPLANE.' STILL NO EXCUSE, BUT TRUTHFUL REASON. AFTER LNDG, FO SAID HE TRIED TO CONTACT GND AND WAS ON CORRECT FREQ, NO ANSWER. RAMP TOLD US TO CALL DEN GND CTL. DEN GND GAVE A PHONE NUMBER. I CALLED, REALIZED WE MIGHT NOT HAVE RECEIVED 'CLRED TO LAND.' I DID EXPLAIN I WAS DEALING WITH A FLT CTL PROB. DURING TAXI IN, I WAS TESTING MAIN ELECTRIC TRIM AT EACH FLAP SETTING, NOSE UP AND NOSE DOWN ON THE LOWER R SIDE OF THE PEDESTAL WHERE THE TKOF WARNING HORN IS INSTALLED. WROTE UP MAIN ELECTRIC TRIM. MAINT TOOK PLANE OTS.

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.