737-700 Alpha Floor Limit - Why & When?

[Chris Catalano 0]

Sometimes upon landing, I seem to have trouble by triggering the Alpha Floor Limit (the A flashes on the speed selector on the MCP, and the horn sounds). I am closely following the landing speed limits that are poseted in the FMC for a flaps 30 or flaps 40 landing, yet I still get this problem. Why is this happening if I am following the correct landing speeds in the FMC? How can I anticipate when this is going to happen before it even does? Any ideas? How do I avoid this? How can I tell the times this is STILL going to happen when I choose to follow the FMC speeds?ThanksChris Catalano

[fozzy 1]

are you sure you are initializing the FMC correctly? check that you are using kg (or lbs) in FS and in the PMDG load manager and in the PMDG menus. Luca

[Guest glenlee]

As Luca said, you need to check you are using the correct weights when you are on the ground and setting up the FMC.Have you used the Load Config Utility?Double check with the manual that the take-off v1 vr & v2 settings given to you by the FMC when you right click (after setting flaps) are somewhere near. That will prove that you are configured correctly.When you are approaching your destination double check your landing weight (i.e add fuel to Zero fuel weight) and make sure it is correct. Click on the appropriate FMC calculated flap/speed reference setting. This tells you the speed you should aim for when you touch the runway (give or take a bit for wind).Finaly, make sure you bring the speed down with the flap speed setting bug, i.e. Reduce the speed (MCP dial) to the 'flaps up' marker, lower the flaps to position 1 when the speed reaches the bug, then wind the speed back to the 'flaps 1' marker and lower the flaps to 5 (through 2), bring the speed back to the 'flaps 5' marker..... etc etc.If you reduce the commanded speed to the landing speed without waiting for the flaps to catch up you will enter the stall 'red bricks' area and you will either fall out of the sky or accelerate away - (Alpha floor)Hope this helps.Glen Lee

[Chris Catalano 0]

>If you reduce the commanded speed to the landing speed without waiting for the flaps to catch up you will enter the stall 'red bricks' area and you will either fall out of the sky or accelerate away - (Alpha floor)THAT'S IT!!!!!!!!!!!!! I am POSITIVE I follow the weights carefully (I have a whole MS Excel chart I designed for fuel calculations & weights to make sure), and I DO use the Load Manager - but - I OFTEN do NOT wait for the flaps to "catch up" as I often just dial down to the landing speed. I am CERTAIN this is my problem!!! Thank you so much! I am sure this will clear up the problem, as I am doing wrong EXACTLY what you described! Thanks a million!Chris Catalano

[Guest glenlee]

Glad to help, happy flying.Glen

[Guest viper18799]

I would be intrested to see your excel sheets for fuel planning as the PMDG sheets are sometimes off and do not allow you to plan for a 315 kt climb out

[Orlaam 306]

You don't have to wait until the speed is at the speed bug on the tape. A lot of videos I've seen have pilots setting flaps above this speed, and I don't think it's uncommon for them to do this. I believe as long as you're within limits for flap safety, you can set flaps to 5 even if you're doing 210 knots, and so on. I'm sure the bug speed is more of a reference to avoid a stall, but I may be way off.Anyone?