Cat3A on B737... Flaps 30 or 40...

[despegue]

My current airline has just been approved for CAT3A LVP.
Now, our procedure requires us to use flaps 40 (we are a B737 operator), which I also used during LVP in another airline. The main reason is the better ground-view as the approach-angle is flatter.

Yesterday however I got into a discussion with one parc-aviation captain on a contract with us, who claims that nowadays, Boeing does not recommend this anymore and pleads for a flaps30 approach in all weather ops. This guy is the head of safety/security for a European National airline, so he should know what he is talking aboout.
Having never heard about this fact, and having recently completed a Lufthansa based LVP ground-course , I ask you: are you in your airline using Flaps 30 or 40 for CAT2/CAT3 , (on B737)

Thanks and have a safe 2005

[BOAC]

despegue - I know nothing of the Boeing 'recommendation'. Most airlines insist on F40 in 300m or less since the view is better (lower nose angle - nb 'approach angle' is always the same for F30 or 40). It is reckoned you will NOT see the necessary visual cues in 300m or less with the higher nose angle.

HOWEVER - do what your OPS manual says! If it is to change, Boeing will tell everyone.

[BLE]

Boeing does not "plead" flap30 for all approaches.
The forward view is improved in low vis conditions by using flap40.

Flap30 is normally only used if the aircraft is operated under JAR OPS and there is an issue with approach climb weight due to operations with DA below 200`.
In addition, if the aircraft is a fail operational 737 600-900 certified for CatIIIb ops, then flap30 is the only option if you plan to land with one engine operating.

And you will be amazed by the number of people who should know what they are talking, and it turns out, they do not.

Ask him for the Boeing reference, I`m sure Boeing Flight Ops would be surprised if he can give you one!:8

[bantios]

Interesting topic...

Some airlines (like mine) have a Flaps 40 policy for all landings. During a CAT 3 landing i dont see why flaps 40 would be a problem, if anything it would be a bonus as you get a better view out the window (due to pitch angle).

[FlightDetent]

I'm with BOAC.

[URL=http://www.pprune.org/forums/showthread.php?s=&threadid=154972&highlight=segment/URL]

[M.85]

maybe a lower Vref,hence a lower sink rate;-)

M.85

[Noak]

In our B737 NG FCOM Vol 1 it is stated in the chapter "Limitations" under "Low Weather Minima Operations" that:

The airplane is approved for the following types of ILS approach and landing:

(.......some text omitted)

DH below 100 feet but not less than 50 feet (Category IIIa) (Flaps 30 and 40).
- Dual channel automatic approach and landing.

In other words we may use flaps 30 or 40 at our discretion.

[alexban]

737 is certified for cat3 with flaps 30 or flaps 40 .
We use flap 30,but it's not a must.We use flap30 most of the time (95 % of the landings we do) so why use a not so trained configuration in a cat 3 app?
Brgds Alex

[BOAC]

alexban - perhaps you need to practice more Flap 40's?:D

I assume you do not operate often to slippery or short runways, or in vis of less than 300m? Have you been shown 200m at 50' in the sim with Flap 30 and Flap 40? I can assue you there IS more to see at 40.

The reason (again) is to improve your chances of actually SEEING the required reference in 300m or less, and thereby improve your chances of landing. It has nothing to do with handling, since the aircraft (which is doing the handling, so it doesn't matter whether it is 'practised' at it or not) is equally happy at 30 or 40. The only thing YOU have to do 'differently' is to remember to select one more notch of flap.

[alexban]

BOAC -you assume right. We operate mostly on big international airports,long rwys,only one or two rwys with less than 2000m.So ,maybe you have a point.
I'll try to see if there is a big difference between what you see at flaps 40 or flaps 30 .The difference in airplane boddy attitude is 1.7 degrees (3.7-flap30 ; 2.0-flap40 for 700 series) and the main gear touchdown poin (no flare) is at 657' (flap30) or 683' (flap 40) .So ,not a big difference,from this figures,i guess.Also ,you can see,almost 30' less in air when using flap 30 ;)
But ,again,you may have a point.Happily,we get to chose between 30 or 40.
Brgds alex

[Bearcat]

We use Flaps 40 most of the time unless the missed approach climb limit weight is against us.....then we use flaps 30. I have had to do bleeds off cat 3 approachs sometimes when our weights were so high.....this is a pain as the work load is through the roof together with the cat 3 stuff. our ops man has if i can remember nearly a 4 ton penalty for icing enroute and this stuffs us re above.

[A and C]

I've used both 30 and 40 flap for CAT 3 landings I find that 30 flap gives a smoother landing as for seeing the lights at DH I can't say that 40 gives a better veiw than 30 in fact I don't think that there is much to choose between them.

So for me the runway length is the number one factor for flap selection as most of the places that I go GA performance is not a critical factor however if the runway might be slippery I would go for 40.