Flaps 30 requires higher speeds, so I don't know how much fuel you are really saving. Your full flaps are down for maybe 3-5 miles max. There are many reasons for using flaps 30 instead of 40 so unless you can show me the airlines that choose 30 are doing it for fuel, I will not believe it. I have heard that some airlines use flaps 30 for higher speeds not any cost savings and others have said for tailstrike reasons. - David Lee

Lower speed on approach means more drag and more fuel flow. You are below the minimum drag speed so drag coefficient increases as speed decreases. Therefore flap 40 is a double hit on fuel flow. Try it for yourself in the NGX as I did (see my earlier post). It is only for a few minutes but it all adds up, just like single engine taxi.

 

Other negative effects include more noise and greater wear on the flap mechanism. Clearly GOL are prepared to accept those disadvantages for their own operational reasons.

Well 777200lrf it is a detailed table with fuel savings researched by Boeing. I imagine IT IS RELEVANT, even if I am not a 737 pilot or operator. In the Boeing SOP I dont see a major concern about a tail strike with flap 30 setting.

I found this Boeing SOP. Low fuel burn is in line but they seem more concern about safety in the approach and a missed approach possibility more than anything else including a tail strike. I would imagine there is a greater threat in the -900.

Maybe they operate in enough short runways like Congonas that the use Flaps 40 standard.

 

http://www.boeing.com/commercial/aeromagazine/articles/qtr_02_10/5/

 

Yes, in this video, at 3:15, the captain explains (in portuguese), that Gol adopts flap 40 because of the lower risk of a tail strike... In all 737-800 of Gol fleet there is a placard on the panel saying flaps 40 is standard for landing...

 

 

http://www.airliners.net/photo/Gol-Linhas-Aereas-Inteligentes/Boeing-737-8EH/2223813

 

 

Nice post! Interesting reading!

 

That's pretty interesting how GOL would make mandatory F40 for tailstrike prevention!

 

Personally we don't select landing flap based on tailtrike prevention and is purely performance derived, there's several other factors which would make a tailstrike far more likely on landing like

 

 

•Unstabilized approach

 

•holding off the flare (going for a greaser isn't great on a 1700m runway)

 

•Incorrect Landing Technique

 

•Trimming in the Flare

 

•Incorrect Airspeed

 

•Crosswind Landing

 

•No Speedbrake

 

•Mishandled Go-Around

 

 

F40 gives you a 1.5 degree less nose attitude compared to F30, I can't think of any Tailstikes during/after landing that could've been avoided from using a F40 instead of F30, like Kevin said maybe GOL have their own reasons to use F40 on all landings.

 

On the NG's a tailstrike is far more likely on the -800's and 900's, hence why they're fitted with tailskids.

I just tried a comparison in the 737-800 on a three degree slope at Flap 30 and 40, with the speed set at Vref + 5.

 

Flap 30 (Vref 148):

Pitch: +2 deg

N1: 59.1%

FF 1200 kg/hr

 

Flap 40 (Vref 141):

Pitch: +0.5 deg

N1: 65.6%

FF 1780 kg/hr

 

In this case pitch angle will be approximately 1.5 degree more during flare at flap 30 than at flap 40. That brings you closer to the tailstrike limit.

 

Assuming about 2 minutes stabilised at Vref the extra fuel burn is 38 kg. Not a lot but if you scale it up by the number of landings each day and it starts to become significant. The higher N1 means more noise of course.

let's not split hairs...

 

A 1.5 degree difference is negligible at best.

let's not split hairs...

 

A 1.5 degree difference is negligible at best.

That depends how close you get to a tailstrike. 1.5 degrees could make all the difference between impact and no impact.

 

I wasn't trying to prove any point. Just showing there is a difference in pitch and it is easily visible on the PFD.

flaps? meh i land without.

 

 

Your final flap setting isn't going down until close to the runway, how much fuel do you think is really being burned? - David Lee

 

The Boeing Aero article linked by Alberto suggests you could save around 8kgs with Flap 30 vs Flap 40. 8kgs is negligible for one pilot on one aeroplane, but an operator with perhaps hundreds of aircraft and thousands of flights per day, is looking at it as 8kg x 1800 flights per day = 14,400kg of fuel saved every day -- just by using Flap 30 instead of Flap 40.

 

As has already been mentioned, Flap 40 would be sensible in LVPs as the lower deck angle will (slightly) improve the visual segment.