M-20P PLT LANDED THE ACFT AND FORGOT TO EXTEND THE LNDG GEAR.

Narrative

I HAD JUST COMPLETED 4 1/2 HR FLT FROM NEW YORK; LNDG AT ZZZ; US. A PLT REQUESTED THAT I ACCOMPANY HIM TO AN ARPT IN HIS MOONEY ACFT. THE OTHER PLT WAS IN COMMAND OF THE AIRPLANE FOR THE TKOF AND SUBSEQUENT FLT AND; WITH VFR FLT FOLLOWING AND PILOTAGE; WE PROCEEDED TO THE AIRSTRIP. UPON REACHING THE AIRSTRIP; SITUATED IN HILLY TERRAIN; WE ENCOUNTERED TURB AND UPON TURNING THE BASE LEG THE PLT ASKED ME TO LAND THE AIRPLANE. THE AIRSTRIP WAS A PAVED 1600-1800 FT BY 25 FT. I HAD LARGE; UNFAMILIAR HEADSET WHICH IMPEDED MY ABILITY TO HEAR THE GEAR WARNING HORN. UPON TURNING TO FINAL; THE PLT SAID 'I'M EXTENDING THE FLAPS.' HAVING JUST COME FROM A 2 CREW COCKPIT AND ACCUSTOMED TO FLYING WITH A QUALIFIED COPLT; AND WITH THE SUDDEN CHANGE OF COMMAND; WE FAILED TO ENSURE THAT THE GEAR WAS DOWN. THE SUBSEQUENT LNDG WAS GEAR UP AND ON THE RWY. NEITHER THE PLT NOR MYSELF SUSTAINED ANY INJURY. THE ACFT SUSTAINED WHAT APPEARED TO BE MINOR SKIN DAMAGE AND A PWR OFF PROP STRIKE. THIS INCIDENT COULD HAVE BEEN AVOIDED BY MY HAVING BEEN MORE FAMILIAR WITH THE ACFT AND BY MY HAVING BEEN IN COMMAND FROM THE OUTSET OR EARLIER ON IN THE FLT. OBVIOUSLY; THE TRIED AND TRUE 'GUMP CHK' OR STRICT ADHERENCE TO CHKLIST ITEMS WOULD HAVE PRECLUDED THE SIT. I AM A PROFESSIONAL CPR PLT WITH AN UNBLEMISHED RECORD AND ATTEND RECURRENT FLT TRAINING REGULARLY. I WAS SICK ABOUT THIS EVENT.