Hello everyone.

 

To my understanding, a lot of airlines use Flaps 25 as standard for landing but will increase to Flaps 30 depending on runway length and weather conditions. Assuming weather is calm, around what runway length would pilots start switching to Flaps 30? Also, while you’re here: What wind speed, crosswind component, and/or gust factor would justify Flaps 30?

 

Thanks in advance.

1 hour ago, HighFlier said:

a lot of airlines use Flaps 25 as standard for landing

Source please?

6 minutes ago, vc10man said:

Source please?

No particular source, mainly cockpit videos and even some -8 pilots commenting here on this very forum. I very well could be wrong but it’s just what I observed.

What I have read is that on the 747 Flaps 30 is rather „normal“ and F25 is used for cross wind landings. It has a high Vref anyway due to its arrow shaped wings, why increasing it even further, except for very strict NAP reasons

what do FCOM abd FCTM say?

Edited February 12, 20197 yr by Ephedrin

6 minutes ago, Ephedrin said:

What I have read is that on the 747 Flaps 30 is rather „normal“ and F25 is used for cross wind landings. It has a high Vref anyway due to its arrow shaped wings, why increasing it even further, except for very strict NAP reasons

what do FCOM abd FCTM say?

I’ll take a second look at the FCOM. The 747-8 doesn’t come with a FCTM, or if it does, it’s missing from the Ops Center for me.

PMDG doesn't deliver one... but google does 😄 I only have the FCOM on my mobile but I haven't found a search function on the iphone pdf reader yet lol

 

11 minutes ago, Ephedrin said:

PMDG doesn't deliver one... but google does 😄 I only have the FCOM on my mobile but I haven't found a search function on the iphone pdf reader yet lol

 

See I’ve read that a lot of people have done this, but I can’t seem to find one using Google. Perhaps I just don’t what keywords to type in but I’ll try again.

Edit: Found one but it’s from 2010 and says TBD for anything 747-8 related.

Edited February 12, 20197 yr by HighFlier

Gents,

This is not an easy answer because there are a few important factors here.

First is related to landing distances required for landing at the destination, alternate by FAA or ICAO....distances that will vary by weight, wx conditions, elevation, temperatures a/c condition.

Next is what is the company policy based on the above and then what the manufacturer recommends. 

Flap Setting for Landing from Boeing
For normal landings, use flaps 25 or flaps 30. When conditions permit, use flaps 30 to minimize landing speed, and landing distance.

Flaps 25 provides better noise abatement and reduced flap wear/loads.
Note: Runway length and condition must be taken into account when selecting a landing flap position.

What is considered a short runway? Some airlines use as a reference number between 7000 FT to 8000 FT, but again depends on the second paragraph above.

Now with gusty winds doing an approach and a landing with flaps 25 is much easier versus flaps 30 where is more drag, more constant and drastic power changes leading to a more unstabilized approach when the wind is kicking like crazy.  Again, we will check performance landing data and act accordingly. Sometimes you have a choice between 25 x 30.

 

Far to many variables here for a 'stock' answer, IMHO, Landing Weight would be my first consideration, followed by runway condition (both normal surface condition and/or presence of contamination), followed by wind direction. On short (=<7,000 ft) runways, it'd be a no land for me with any tail wind component, but crosswind would be ok by me if <30kts.

Oh - and I'd be at Flaps 30 on a short runaway no matter what.

Edited February 13, 20197 yr by PopsBellNC
Forgot flaps recommendation

On 10000 foot plus runways full flaps is just wasting fuel and time. Important to also consider missed approach terrain clearance. The faster you come in the faster you can climb out when you have to. 

Edited February 14, 20197 yr by sloppysmusic

2 hours ago, sloppysmusic said:

On 10000 foot plus runways full flaps is just wasting fuel and time. Important to also consider missed approach terrain clearance. The faster you come in the faster you can climb out when you have to. 

Good point that reminded me of my last arrival at KMIA landing rwy 9.  One has to pay attention to the 747-8 taxi restrictions at many locations, which at KMIA requires the aircraft to depart the runway at the far end because non of the normal exits are open for the -8.  Even autobraking 2 has to be disconnected several thousand feet before the end.

4 hours ago, sloppysmusic said:

On 10000 foot plus runways full flaps is just wasting fuel and time. Important to also consider missed approach terrain clearance. The faster you come in the faster you can climb out when you have to. 

Well that is one way of looking at it, but unless you think there is a high probability of a go -around, any chief pilot and/or airline/cargo operator would say "Save the tires and bakes, G*d da%*nit!!" Regular, faster-than-necessary, TD speeds won't appreciably affect a climb out, but will most certainly affect your maintenance costs.

4 hours ago, sloppysmusic said:

On 10000 foot plus runways full flaps is just wasting fuel and time. Important to also consider missed approach terrain clearance. The faster you come in the faster you can climb out when you have to. 

As I was told once by an instructor when I was in test flight school "Do you have any verifiable data to support your supposition?" 🙂

Grace and Peace,

Edited February 14, 20197 yr by Bluestar
clarification

6 minutes ago, Bluestar said:

As I was told once by an instructor when I was in test flight school "Do you have any verifiable data to support your supposition?" 🙂

Grace and Peace,

That info comes straight from the training material in all the fcoms for current PMDG jets, so yes it's not actual real world I should have made that clear. 

13 minutes ago, PopsBellNC said:

Well that is one way of looking at it, but unless you think there is a high probability of a go -around, any chief pilot and/or airline/cargo operator would say "Save the tires and bakes, G*d da%*nit!!" Regular, faster-than-necessary, TD speeds won't appreciably affect a climb out, but will most certainly affect your maintenance costs.

The difference in braking between 30 and 40 flaps is minute especially when reverses and autobrakes are used efficiently but the extra fuel consumption adds up considerably after thousands of flights.