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Joelrbt93

Extending flaps at what altitude

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Hi there,

 

What is the best altitude to start extend the flaps after we reach the best flap speed? by the way I'm flying the pmdg 737. Normally during descent i would start to extend flaps 1 to 5 at FL150. Talking about realism, am I doing the right thing? Thanks.

 

Joel

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Your a little high to be extending flaps.

 

According to the FCOM on downwind to landing Flaps 1

Turning base Flaps 5

Glideslope alive Gear down, Flaps 15

Glideslope capture Flaps 30 landing flaps.

 

 

Basically my flaps don't start coming out until under 7000 feet if not lower.

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On your initial approach to the airport you want to be flying at flaps up manouvre speed...ie no flaps. Speed will depend on weight but will be 200-220 kias. Your altitude will vary, but 3000-5000 would be about right.

 

When on LOC intercept heading at your G/S intercept height (2000-3000), reduce speed to 180 and extend flaps as needed ....probably flap 5

 

When G/S alive reduce to 160 and set appropriate flap ...probably 15..... gear down.

 

Fly the G/S at 160, and when 3-5 miles from touchdown select landing flap and reduce speed to VAPP

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You should never need to extend flaps in any a/c until you're approaching the localiser. From 250kts down to 210kts do nothing. To establish on the localiser or within 10-15dme of your faf reduce speed to 180 kts now extend your flaps. Then progressively extend them until landing. So look at your STAR charts and see the speed restrictions. Always assume that ATC tell you to reduce to 180 from the stack to localiser intercept.

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Joel,

 

The timing of when to extend flaps is simply when you want to slow the aircraft down in preparation for landing. Slower you go the more flaps you need. Its not directly related to altitude. Here's a quick example, from the ATC side of things. Most airline pilots want to go as fast as possible, for as long as they can, until they must start slowing down to configure the aircraft for landing. Let's say your the first arriving flight in the morning to ORD. Nobody is in front of you so there wouldn't be any speed reductions for other traffic. Also assume you were given a descent in a timely manner to get the aircraft down. Its hard for most airliners to get down AND slow down at the same time. Some are better than others. Example, a B727 can do it without any difficulty. But a B757 has a real problem doing it. 

 

Almost all B737's can go 250kts to about a 15 mile final. (OR 15 flying miles from the runway). Remember the altitude assumption, the aircraft can't be high OR above the glideslope or they WILL need to slow earlier.

So if you are doing 250Kts no flaps are needed. When you get to 15 miles you will need to start slowing down THUS here is when you start lowering flaps. Start slowing down to around 210kts which will be about flaps 5. When you slow, from 250kts, add flaps as you slow, lets say 230kts flaps 1 or 2 then at 220 add flaps 5 and go to 210KTS. DISCLAIMER, I'm not an airline pilot these are only very general instructions. Hold 210 kts till 10 miles out then add flaps slowly as you slow down more. Slow to 180/170 when your flaps should be at flaps 15 or so. Hold 180/170 till the FAF or about 5 miles out. Start slowing AND adding flaps till your at 125 to 140 and your flaps are at FULL.

 

So basically you add flaps to slow down, regardless of altitude. If you don't need to slow down you don't need any flaps.

 

Hope this helps.

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