Can a commercial jet pilot please confirm this for me?I have spent many hours riding up front of some B727, B737 etc some years back and I thought from memory the '1,000' to go' (or therabouts) altitude audio horn sounded as assigned altitude was approached - regardless of whether the auto-pilot was engaged or not.Can anyone please clarify this for me?In the UIPC module, the warning horn only sounds if the auto-pilot is engaged as the assigned alt. is approached, whereas one of the B727's I have, has the exact audio horn replica sound and this sounds even if the auto-pilot is disengaged ... as I would have expected (and as I thought was the case in reality).Thanks in anticipation.

What you are referring to is the Altitude Alert or also called an Altitude Advisory System. It operates independently of the Autopilot/Autoflight system. It does take it's input from the altitude that is set in the Autopilot Altitude Select window or mode control panel. The sysem usually includes an alert light on the altimeter (which may or may not illuminate a Master Caution Light if installed) and an aural sound through the cockpit speakers. The altitude that the light and aural come on will vary with the manufacturer of the system in a particular make of aircraft. On the DC-10 I flew it came on at 750ft prior to the selected altitude and went out 250ft prior. On our 757's, they came on at 900ft and off at 300ft and if you deviated 300ft from the selected altitude once you were there, the Master Caution light along with the other indication came on along with an Altitude Alert message on the EICAS.Regards,Ed Weber a.k.a tallpilot/Cap'n Tall