Narrative:

On approach I called for gear down. (I was the PF at the time.) the gear didn't come down. The indication was: nose gear red; main gear had no lights. At this point we were too close to the airport; in the 'critical phase of flight' to be conducting emergency checklists; so the captain notified tower that we would be going around; and requested to fly a box pattern out to the west. The captain then started performing the manual gear extension checklist from the QRH. I mentioned that we should check circuit breakers; so I slid my seat up so the captain could inspect the area behind my seat. No breakers out. I inspected the area behind his seat. No breakers out. At a certain point; the checklist has the crew look through the various landing gear inspection ports to determine if the gear is indeed down. The captain decided that we would switch PF/pilot monitoring duties. He took the airplane (on downwind). I would perform the inspection. The captain made an announcement about the gear issue; informing the passenger that I would be coming back to the cabin. I first checked the nosewheel. It was down with the alignment marks lined up. Next; I proceeded with the QRH back to the main cabin to inspect the main landing gear through the viewing ports located just past mid cabin. I brought the QRH with me because it contained a diagram of what I was looking for. I also took my flashlight. I located the viewing port and took up the carpet. I knew I didn't have much time; because now we were down to around 3000 pounds of fuel (less than 30 mins). I spent several mins looking through the inspection port; but was unable to see the alignment marks in the main gear wells. I could see the wheels were down; I just couldn't see the alignment marks. I knew we didn't have a lot of time so I proceeded back to the flight deck. I informed the captain that I could not locate the alignment marks; but I saw the wheels were down. I asked him a couple times if he wanted to go back and inspect it himself. He declined due to our low fuel status. He indicated that we would not have time to delay any longer. We needed to land very soon. While I was in the back; the captain briefed the 'a' flight attendant about the emergency; and to prepare for a possible evacuate/evacuation. We did a low pass. Both ZZZ1 and ZZZ2 confirmed the gear was down. We flew a very tight pattern around and landed uneventfully on runway 16. As soon as we turned off the runway; I smelled smoke. Next we saw the smoke getting quite thick very rapidly. The 'a' flight attendant called the captain to inform of smoke in the cabin. The captain stopped the aircraft. We performed the emergency evacuate/evacuation qrc and evacuate/evacuationed the aircraft. The smoke irritated my throat and lungs a bit; so at the advice of medical responders; I went to get checked out. I'm not sure if my inability to determine the main landing gear status was due to: poor lighting; misaligned mirrors; dirty lenses; or if it was a training issue (not looking at it correctly) or; possibly a combination. We as pilots could benefit from increased training on this. I know we talked about how to perform this inspection at some point in training; however; at no point was any in-aircraft training given on this inspection. It seems relatively simple until you actually attempt to do it yourself. I was later informed that this inspection was repeated on this aircraft once it was parked at the hangar. It took the first individual approximately 15 mins before they could locate the alignment marks in a lighted hangar. I'm not trying to excuse my inability to successfully perform the inspection; but clearly all could benefit from further training on it. Callback conversation with reporter revealed the following information: the reporter believes that a landing gear relay may have been responsible for the absence of a gear down indication. This may also have caused the aircraft to remain in the air mode after touchdown; causing the packs to overheat and produce the cabin smoke. The viewing ports for the main gear were ineffective. The lenses; mirrors; and even the alignment marks on the landing gear were covered with dirt and brake dust; rendering the system useless.

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Original NASA ASRS Text

Title: THE LNDG GEAR FAILED TO EXTEND ON A B737. EMER GEAR EXTENSION WAS PERFORMED; BUT WHEN GEAR COULD NOT BE CONFIRMED DOWN; THE VIEW PORTS WERE UTILIZED. AFTER LNDG; SMOKE ENTERED THE CABIN AND THE ACFT WAS EVACUATED.

Narrative: ON APCH I CALLED FOR GEAR DOWN. (I WAS THE PF AT THE TIME.) THE GEAR DIDN'T COME DOWN. THE INDICATION WAS: NOSE GEAR RED; MAIN GEAR HAD NO LIGHTS. AT THIS POINT WE WERE TOO CLOSE TO THE ARPT; IN THE 'CRITICAL PHASE OF FLT' TO BE CONDUCTING EMER CHKLISTS; SO THE CAPT NOTIFIED TWR THAT WE WOULD BE GOING AROUND; AND REQUESTED TO FLY A BOX PATTERN OUT TO THE W. THE CAPT THEN STARTED PERFORMING THE MANUAL GEAR EXTENSION CHKLIST FROM THE QRH. I MENTIONED THAT WE SHOULD CHK CIRCUIT BREAKERS; SO I SLID MY SEAT UP SO THE CAPT COULD INSPECT THE AREA BEHIND MY SEAT. NO BREAKERS OUT. I INSPECTED THE AREA BEHIND HIS SEAT. NO BREAKERS OUT. AT A CERTAIN POINT; THE CHKLIST HAS THE CREW LOOK THROUGH THE VARIOUS LNDG GEAR INSPECTION PORTS TO DETERMINE IF THE GEAR IS INDEED DOWN. THE CAPT DECIDED THAT WE WOULD SWITCH PF/PLT MONITORING DUTIES. HE TOOK THE AIRPLANE (ON DOWNWIND). I WOULD PERFORM THE INSPECTION. THE CAPT MADE AN ANNOUNCEMENT ABOUT THE GEAR ISSUE; INFORMING THE PAX THAT I WOULD BE COMING BACK TO THE CABIN. I FIRST CHKED THE NOSEWHEEL. IT WAS DOWN WITH THE ALIGNMENT MARKS LINED UP. NEXT; I PROCEEDED WITH THE QRH BACK TO THE MAIN CABIN TO INSPECT THE MAIN LNDG GEAR THROUGH THE VIEWING PORTS LOCATED JUST PAST MID CABIN. I BROUGHT THE QRH WITH ME BECAUSE IT CONTAINED A DIAGRAM OF WHAT I WAS LOOKING FOR. I ALSO TOOK MY FLASHLIGHT. I LOCATED THE VIEWING PORT AND TOOK UP THE CARPET. I KNEW I DIDN'T HAVE MUCH TIME; BECAUSE NOW WE WERE DOWN TO AROUND 3000 LBS OF FUEL (LESS THAN 30 MINS). I SPENT SEVERAL MINS LOOKING THROUGH THE INSPECTION PORT; BUT WAS UNABLE TO SEE THE ALIGNMENT MARKS IN THE MAIN GEAR WELLS. I COULD SEE THE WHEELS WERE DOWN; I JUST COULDN'T SEE THE ALIGNMENT MARKS. I KNEW WE DIDN'T HAVE A LOT OF TIME SO I PROCEEDED BACK TO THE FLT DECK. I INFORMED THE CAPT THAT I COULD NOT LOCATE THE ALIGNMENT MARKS; BUT I SAW THE WHEELS WERE DOWN. I ASKED HIM A COUPLE TIMES IF HE WANTED TO GO BACK AND INSPECT IT HIMSELF. HE DECLINED DUE TO OUR LOW FUEL STATUS. HE INDICATED THAT WE WOULD NOT HAVE TIME TO DELAY ANY LONGER. WE NEEDED TO LAND VERY SOON. WHILE I WAS IN THE BACK; THE CAPT BRIEFED THE 'A' FLT ATTENDANT ABOUT THE EMER; AND TO PREPARE FOR A POSSIBLE EVAC. WE DID A LOW PASS. BOTH ZZZ1 AND ZZZ2 CONFIRMED THE GEAR WAS DOWN. WE FLEW A VERY TIGHT PATTERN AROUND AND LANDED UNEVENTFULLY ON RWY 16. AS SOON AS WE TURNED OFF THE RWY; I SMELLED SMOKE. NEXT WE SAW THE SMOKE GETTING QUITE THICK VERY RAPIDLY. THE 'A' FLT ATTENDANT CALLED THE CAPT TO INFORM OF SMOKE IN THE CABIN. THE CAPT STOPPED THE ACFT. WE PERFORMED THE EMER EVAC QRC AND EVACED THE ACFT. THE SMOKE IRRITATED MY THROAT AND LUNGS A BIT; SO AT THE ADVICE OF MEDICAL RESPONDERS; I WENT TO GET CHKED OUT. I'M NOT SURE IF MY INABILITY TO DETERMINE THE MAIN LNDG GEAR STATUS WAS DUE TO: POOR LIGHTING; MISALIGNED MIRRORS; DIRTY LENSES; OR IF IT WAS A TRAINING ISSUE (NOT LOOKING AT IT CORRECTLY) OR; POSSIBLY A COMBINATION. WE AS PLTS COULD BENEFIT FROM INCREASED TRAINING ON THIS. I KNOW WE TALKED ABOUT HOW TO PERFORM THIS INSPECTION AT SOME POINT IN TRAINING; HOWEVER; AT NO POINT WAS ANY IN-ACFT TRAINING GIVEN ON THIS INSPECTION. IT SEEMS RELATIVELY SIMPLE UNTIL YOU ACTUALLY ATTEMPT TO DO IT YOURSELF. I WAS LATER INFORMED THAT THIS INSPECTION WAS REPEATED ON THIS ACFT ONCE IT WAS PARKED AT THE HANGAR. IT TOOK THE FIRST INDIVIDUAL APPROX 15 MINS BEFORE THEY COULD LOCATE THE ALIGNMENT MARKS IN A LIGHTED HANGAR. I'M NOT TRYING TO EXCUSE MY INABILITY TO SUCCESSFULLY PERFORM THE INSPECTION; BUT CLEARLY ALL COULD BENEFIT FROM FURTHER TRAINING ON IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER BELIEVES THAT A LNDG GEAR RELAY MAY HAVE BEEN RESPONSIBLE FOR THE ABSENCE OF A GEAR DOWN INDICATION. THIS MAY ALSO HAVE CAUSED THE ACFT TO REMAIN IN THE AIR MODE AFTER TOUCHDOWN; CAUSING THE PACKS TO OVERHEAT AND PRODUCE THE CABIN SMOKE. THE VIEWING PORTS FOR THE MAIN GEAR WERE INEFFECTIVE. THE LENSES; MIRRORS; AND EVEN THE ALIGNMENT MARKS ON THE LNDG GEAR WERE COVERED WITH DIRT AND BRAKE DUST; RENDERING THE SYSTEM USELESS.

Data retrieved from NASA's ASRS site as of May 2009 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.