Narrative:

Good VFR 10SM/clear winds 340at 9 knots; multi engine lesson; completed 1.0 of 1.4 total hours. On our second touch and go we were cleared for the option on rwy xx. This was a simulated single engine from downwind through base and landing. As is normal in a single engine situation the gear horn is going off the entire time the throttle is pulled back. The student missed putting the gear in the down position and I missed verifying that. On a left base the student made a call that the final approach was clear of traffic which I attempted to verify visually. With the exception of the gear the pattern was normal/routine. We landed on rwy xx with the gear up. When we came to a stop I notified tower of what had happened; turned all switches to the off position and exited the airplane. Airport personnel were present with a few minutes.I believe the biggest contributing factor to the incident (other than obvious pilot error) is that during single engine training the gear warning horn is going off continuously and pilots become immune to it. Adding a gear warning silence horn would help with that but comes with other potential problems. The BE76 poh does have the option of a gear warning silence button that will silence the gear warning horn until greater than 16 degrees of flaps are put in. At that point the warning horn will sound again and can't be silenced. There are additional audio advisory systems that can be used as another check that the gear is down. This is based off of airspeed that can be set so that an audible voice in the headset says 'too low; gear' is heard when airspeed drops below this and the gear is not down. The key is to get the speed right so that it is not heard during routine training but rather when it is heard it is real and something is done about it instead of ignoring the sound.

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Original NASA ASRS Text

Title: BE76 flight instructor and student reported a gear up landing due to the bias of a single engine operation and the accompanied gear warning horn.

Narrative: Good VFR 10SM/CLR winds 340at 9 Knots; Multi engine lesson; completed 1.0 of 1.4 total hours. On our second touch and go we were cleared for the option on Rwy XX. This was a simulated single engine from downwind through base and landing. As is normal in a single engine situation the gear horn is going off the entire time the throttle is pulled back. The student missed putting the gear in the down position and I missed verifying that. On a left base the student made a call that the final approach was clear of traffic which I attempted to verify visually. With the exception of the gear the pattern was normal/routine. We landed on Rwy XX with the gear up. When we came to a stop I notified tower of what had happened; turned all switches to the off position and exited the airplane. Airport personnel were present with a few minutes.I believe the biggest contributing factor to the incident (other than obvious pilot error) is that during single engine training the gear warning horn is going off continuously and pilots become immune to it. Adding a gear warning silence horn would help with that but comes with other potential problems. The BE76 POH does have the option of a gear warning silence button that will silence the gear warning horn until greater than 16 degrees of flaps are put in. At that point the warning horn will sound again and can't be silenced. There are additional Audio Advisory Systems that can be used as another check that the gear is down. This is based off of airspeed that can be set so that an audible voice in the headset says 'too low; gear' is heard when airspeed drops below this and the gear is not down. The key is to get the speed right so that it is not heard during routine training but rather when it is heard it is real and something is done about it instead of ignoring the sound.

Data retrieved from NASA's ASRS site 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.