After doing a lot of auto landings in Zurich and getting various results I wonder if those programs are 100 % consistent.Ex: On final approach when on the G/S I get the message terrain,terrain.Sometimes I get it,sometimes no.Of course I made 100 % sure that all conditions are the same ( weather,weights,route etc etc )When getting the terrain message I just ignore it and continue.The landing is perfect,all indications are there( from the Green Box to Align etc )I just wonder if the computer can behave weird and if other people notice that too.ThanksHubert Werni

After doing a lot of auto landings in Zurich and getting various results I wonder if those programs are 100 % consistent.Ex: On final approach when on the G/S I get the message terrain,terrain.Sometimes I get it,sometimes no.Of course I made 100 % sure that all conditions are the same ( weather,weights,route etc etc )When getting the terrain message I just ignore it and continue.The landing is perfect,all indications are there( from the Green Box to Align etc )I just wonder if the computer can behave weird and if other people notice that too.ThanksHubert Werni

Hi Hubert,Didn't you post about this before? The terrain warning is triggered by the Rad Alt, have a look on the PFD when on the approach. it's possible to get false warnings in FS and the real world and is usualy caused by rising terrain eg flying over a hill on final approach. I've never had problems with the GPWS in FS but in the real world yes the computers can sometimes do very weird things.http://www.37000feet.com/report/676323http://www.airlinepilotforums.com/hangar-talk/37376-garmin-496-false-terrain-obstacle-warning.html

Hi Hubert,Didn't you post about this before? The terrain warning is triggered by the Rad Alt, have a look on the PFD when on the approach. it's possible to get false warnings in FS and the real world and is usualy caused by rising terrain eg flying over a hill on final approach. I've never had problems with the GPWS in FS but in the real world yes the computers can sometimes do very weird things.http://www.37000feet.com/report/676323http://www.airlinepi...le-warning.html

Yes,I posted this before.I get ( sometimes ) the terrain warning at app 500 feet radio alt above the runway.Anyway,I will take your advice andmonitor the Rad Alt very carefully.By the way this is fun and I like to investigate and solve problems.And being retired I have plenty of time.I will report back once I can achieve this landing and duplicate it several times.ThanksHubert Werni

Yes,I posted this before.I get ( sometimes ) the terrain warning at app 500 feet radio alt above the runway.Anyway,I will take your advice andmonitor the Rad Alt very carefully.By the way this is fun and I like to investigate and solve problems.And being retired I have plenty of time.I will report back once I can achieve this landing and duplicate it several times.ThanksHubert Werni

After you land, have a look at the FSX flight analysis to see how consistent your approach is. It might provide clues.

Is the radar alt the only thing that triggers that? I guess there's no forward looking radar, so it's got to be the rate at which the radar alt is losing altitude. Hmmmm. Need to go read about how GPWS works. Never thought much about it.

Yes,I posted this before.I get ( sometimes ) the terrain warning at app 500 feet radio alt above the runway.Anyway,I will take your advice andmonitor the Rad Alt very carefully.By the way this is fun and I like to investigate and solve problems.And being retired I have plenty of time.I will report back once I can achieve this landing and duplicate it several times.ThanksHubert Werni

Hubert,Some help in your investigation:Lately made three auto approaches into LSZH RWY14.Two approaches at near Max Landing Weight and Flaps35 with a FAS around 161 kts.These approaches both generated a Terrain warning descending through baro 2300 ft on the GS.One approach with 30 tons less weight and Flaps50 with a FAS around 147 kts.This approach did NOT trigger the Terrain warning.Why?The terrain warnings we talk about here are triggered by a terrain closure rate.In this case have a look at GPWS Mode 2B (System Manual -Warning and Alerting- WARN 10.17)The Graph of the warning envelope is on WARN 30.8With slower approach speeds you stay just outside the envelope, higher speeds may just trigger the warning. That is, looking at speed only of course, as a more then normal VS has it's influence too. That's the reason I made all the approaches AUTO.What's also interesting is the 'Airport Envelope Modulation' -see WARN 10.19In the real aircraft LSZH is one of the places where this modulation takes place.Don't think this simulation is modulated that way.Hope it helps,Regards,Harry