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JohnSmith

GPWS Warnings When Approaching Using Flaps 20

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Afternoon everyone. I would like to ask the frequent flyers of the PMDG 777 a brief question about approach flap selection. Yesterday, I was just about to start my approach into Frankfurt. I selected flaps 20 in the FMS and verified the selection when I went through the landing checklist on final. However, just a few hundred feet above the ground, the GPWS began to shout at me, "Too low! Flaps!" Of course, this warning prevented the altitude callouts and my landing was quite rough. I've never had this issue when using flaps 25 or 30. Is this a bug or have I missed something?

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Afternoon everyone. I would like to ask the frequent flyers of the PMDG 777 a brief question about approach flap selection. Yesterday, I was just about to start my approach into Frankfurt. I selected flaps 20 in the FMS and verified the selection when I went through the landing checklist on final. However, just a few hundred feet above the ground, the GPWS began to shout at me, "Too low! Flaps!" Of course, this warning prevented the altitude callouts and my landing was quite rough. I've never had this issue when using flaps 25 or 30. Is this a bug or have I missed something?

The manual states flaps 25 or 30 for landing.  That's why you don't get the warning message when you do use flaps 25 or 30.

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I've never had this issue when using flaps 25 or 30. Is this a bug or have I missed something?

 

You've missed something. Despite being an option on the REF page of the FMC, the selection is non-normal (there are a few situations in which it is specified by Boeing, but as part of non-normal procedures), thus the warning.

 

If, for whatever reason, you want to land with non-normal (other than 25 or 30) flaps, note the FLAP OVRD switch above the gear handle.

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You've missed something. Despite being an option on the REF page of the FMC, the selection is non-normal (there are a few situations in which it is specified by Boeing, but as part of non-normal procedures), thus the warning.

 

If, for whatever reason, you want to land with non-normal (other than 25 or 30) flaps, note the FLAP OVRD switch above the gear handle.

Interesting how the option would still be included in the FMS. Oh well. Thanks for the reply. :)

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Interesting how the option would still be included in the FMS. Oh well. Thanks for the reply. :)

 

Just because it's non-standard doesn't mean that it should be hard to find  :wink:

 

You're welcome.

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I remember one of the engine failure checklists had a flap 20 landing, presumably because of the reduced drag meaning a lower thrust level on the good engine, and missed approach considerations.

 

Flap 20 should be for non-normal, ie: something failed.

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what about page 184/1210 FCOM1 L10.6 ? Flaps 20 and 30 for Autoland

 

Michael

 

What about it?

 

Flap 30 for normal autoland. Flap 20 when non-normal checklists call for flap 20, and then autoland.

 

What's the hang up here?

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What about it?

 

Flap 30 for normal autoland. Flap 20 when non-normal checklists call for flap 20, and then autoland.

 

What's the hang up here?

 

Sorry , no worries , Just thought you could have a Autoland 3 with Flaps 20 and not having the GPWS alert you . Maybe my bad

 

Michael

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Interesting how the option would still be included in the FMS. Oh well. Thanks for the reply. :)

All landing flap settings are in the FMC.

 

Just as Kyle said.

 

Flaps 25 and 30 for normal landing.

Flaps 20 for non normal such as after an engine failure (but you can also land with flaps 30 and single engine....depends on conditions).

 

It is not weird that flaps 20 is also in the FMC....it is there to make your life easier......so you dont have to open up books and tables to go look for the proper speed after a non normal situation.

 

Makes sence no?

 

Ofcource if you dont know when what speed and flap setting should be used.....yes then it gets confusing ;-)

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and I keep getting terrain warning

any ideas

 

Probably actual terrain.

 

The warning you'd get with flap 20 is "TOO LOW - FLAP." If you were getting "TERRAIN," then there was probably actual terrain.

 

You can still hit terrain in the full landing config. What airport were you going into?

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it happened to in tow different airports

heca cairo

enbr Bergen

 

Knowing Bergen rather well, I'm not surprised it gave you that warning, depending on where you were.

 

Cairo I'm not so sure. Regardless, the warning being discussed here is the "TOO LOW - FLAP" GPWS warning. If you were hearing "TERRAIN," I wouldn't call this completely abnormal. I'd have to see it myself to say one way or the other.

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Sorry , no worries , Just thought you could have a Autoland 3 with Flaps 20 and not having the GPWS alert you . Maybe my bad

 

Michael

You can, if you select GPWS Flap Ovrd. That's what that switch is there for.

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So in summary - Flaps 20, 25 and 30 are all valid landing flap setting, hence why they are in the FMS.

 

Flaps 20 would normally be used in an engine-out situation, requiring manual override of the GPWS flap warning using the guarded switch near the gear handle.

 

Flaps 25 and 30 are valid for normal, both engines operating approaches.

 

Boeing recommends only Flaps 20 or 30 are used for autoland, with 20 being in an engine out situation normally.

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