747 Flap Settings During Climb After Takeoff

[il88pp]

Interesting stuff.

But that can't be right. I see it says it right there, and viewed the link as well, but that document can't be right.

 

I will give the flap settings available on the throttle quadrant (and displayed on the gauges). They are different from the ones mentioned in the document.

I will aso give the maximum flap speeds as given the kneeboard. Those are pretty accurate.

I use slightly different values myself. I will add those here in brackets as well. I base these new values on the fact that at a certain flap setting the engine needs to spool up to almost full thrust to get past that speed.

 

The flap settings given in the document you posted do not all exist. The speeds in the document are much lower then the speeds given in the kneeboard. Something amiss with that.

 

Flap -- Max Speed

1--------280 (280)

5--------260 (260)

10-------240 (240)

20-------230 (220)

25-------205 (205)

30-------180 (180)

[MBKHOU]

I hope you will pop in again.

I would like to know, why is it not possible to calculate V-speeds for full flaps?

 

From experience in ffsx I know V-Rotate speed when using full flaps in the B747_400 is around 150-160 knots, depending on weight. At full weight it will rotate and lift off at 160 knots. When almost empty it rotates and lifts just above 150 knots.

 

I like calculations. What is the reason this could not be calculated? Thank you.

 

I guess because full flaps gives way too much drag for a takeoff, and being it's not really

viable, the FMC does not provide the numbers for a full flaps takeoff.

I suspect the main reason you have trouble rotating when using flaps 10 is due to

the trim not being set. This is pretty much proven by you having to adjust trim during

the takeoff roll in order to lift off. Normally that flaps 10 trim setting should be set before

the takeoff. The trim setting is given on the takeoff performance page of the FMC, or

I suppose could be calculated on paper if one had all the numbers.

Like Ralph says, no jets ever take off with full flaps. Many don't even land with full flaps

unless there is a specific reason to do so.

But I'm a 737 buoy for the most part, and am used to it's numbers..

IE: most full load 737 takeoffs are done with flaps 5, and the FMC will give you the

exact trim setting to use. A light 737 takeoff is commonly flown with flaps 1.

Say I'm selecting flaps 5 for takeoff. The FMC will then calculate the three V speeds,

and also the exact trim setting to use, which with the 737 can vary a good bit from

say 4.5, up to around 6 or so. Will vary each flight per load, balance, etc.

I look at the trim scale and adjust the trim so it's at the takeoff setting.

At this time, I usually also dial up the FMC calculated V2 speed on the MCP so it's ready.

 

When using the proper trim setting, you will have no trouble rotating, and the trim

will be just about right after takeoff to where you can release pressure from the yoke,

and still be flying the correct vertical path. With the Boeing jets, you can not engage

the AP if there is pressure on the yoke. But this won't apply to the default FSX jets,

as they are not realistic. I'm just mentioning that as another reason that the correct

takeoff trim setting is so important.

[dspaulding]

I guess because full flaps gives way too much drag for a takeoff, and being it's not really

viable, the FMC does not provide the numbers for a full flaps takeoff.

 

Correct. The drag initially from full flaps doesn't provide much of a benefit than doing partial flaps TO when an engine fails. That's my point guys. It's not about successfully taking off its about performance when an engine FAILS.

[il88pp]

MBKHOU,

Some thoughts:

-I knew about the trim, so I did set some trim before takeoff. It turned out it needed much more. eventually it rotated when I added 4 more clicks while hanging on the stick.

If I had added the trim earlier I am pretty sure the pitch on takeoff would have been just as steep as in that first set of 5 pics. 10 degrees going quicly to 15.

 

-In both flights the vertical speeds were similar. At flaps 10 the B747_400 did not shoot up like a rocket. But at flaps 10 the nose is way steeper up, and the tail nearly scraped the runway.

 

-Do you mean full flaps isn't used in real life because ir produsces to much drag? In FS the opposite happens it seems. With more flaps you need less runway to lift off.

 

-Regarding flaps 5. What aircraft are you talking about here. You mention you fly "the 737" in it, but is that the default 737?

Are you talking taking off full weight?

What speed do you rotate at?

 

-I meant to keep my responses to this discussion purely about the default B747_400. That was the aircraft in the first post of the thread. I see now my questions lead to real world discussions. Please when explaining, say if it is real world data or FS, and how to apply it to FS, if possible. Thanks.:)

[MBKHOU]

Interesting stuff.

But that can't be right. I see it says it right there, and viewed the link as well, but that document can't be right.

 

I will give the flap settings available on the throttle quadrant (and displayed on the gauges). They are different from the ones mentioned in the document.

I will aso give the maximum flap speeds as given the kneeboard. Those are pretty accurate.

I use slightly different values myself. I will add those here in brackets as well. I base these new values on the fact that at a certain flap setting the engine needs to spool up to almost full thrust to get past that speed.

 

The flap settings given in the document you posted do not all exist. The speeds in the document are much lower then the speeds given in the kneeboard. Something amiss with that.

 

Flap -- Max Speed

1--------280 (280)

5--------260 (260)

10-------240 (240)

20-------230 (220)

25-------205 (205)

30-------180 (180)

 

I think the numbers you have are the maximum flaps speeds.

The numbers he gave are the minimum maneuvering speeds for each flap setting.

Those are the numbers that will be used as flap guides on the speed tape.

And you see the reverse when slowing for the landing.

Fer instance, with the 737NG, 240 knots is the maximum speed for flaps, and flaps

two is the max for that speed. But the minimum clean maneuvering speed is about 200

knots. At that point, you would select flaps 1, which has a min maneuver speed of around

180 knots or so. The flaps guide on the speed tape will change as you select each

stage of flaps, and you will see at a glance the exact speeds for the various settings

as you fly them. During the descent, with each speed and flaps setting change, you are

adjusting the MCP speed to match the flap bug on the speed tape. Or.. the FMC will

select those speeds for you if in VNAV.

 

With the appx 200 knot clean maneuvering speed, that is also the slowest I would want

to be when fully retracting the flaps, and the flap guide will show that as you are flying out.

IE: Takeoff with flaps 5, I see a flaps 1 bug at appx 180+ knots or so.. When I reach that

speed, I select flaps one, and the flaps "1" bug changes to an "up" bug at the appx 200 or so

knots. When I reach the speed of the flaps up bug, I then fully retract the flaps.

When the flaps are retracted, the 230 knot speed bug will change to 250 knots for the climb

to 10k ft.

[MBKHOU]

MBKHOU,

Some thoughts:

 

 

-In both flights the vertical speeds were similar. At flaps 10 the B747_400 did not shoot up like a rocket. But at flaps 10 the nose is way steeper up, and the tail nearly scraped the runway.

 

Then the rotation speed was too low for that flaps setting, or you rotated too

soon, or too much.

 

-Do you mean full flaps isn't used in real life because ir produsces to much drag? In FS the opposite happens it seems. With more flaps you need less runway to lift off.

 

Way too much drag.

...................................................................

 

-Regarding flaps 5. What aircraft are you talking about here. You mention you fly "the 737" in it, but is that the default 737?

 

Yep, all my numbers are from the 737. The plane is the PMDG NGX. I don't fly any

default jets. Just way too unrealistic.. :(

 

But the methods are still pretty much the same. The numbers are just adjusted..

.........................................................................................................

Are you talking taking off full weight?

What speed do you rotate at?

 

Usually pretty full when playing SWA buoy. I select the exact load before the

flight.. Number of people, how much cargo, etc..

But I do fly a good number of lighter flights with the BBJ's.

V1, VR and V2 will all vary each flight due to the exact load. And also vary to

the model of 737. In general, each longer model of 737 uses slightly higher speeds

for a certain percentage load.

So with the 737-700, I will often rotate in the mid 130's or so..

But with the 737-800 with the same percantage load, I might rotate in the 140's

range, up to the lower 150's for a wide load 800 flight.

With the little 737-600 and the light BBJ loads I run with it, I'll often rotate in the

mid 120's range. There is no one set of V speeds that covers all scenarios.

 

 

-I meant to keep my responses to this discussion purely about the default B747_400. That was the aircraft in the first post of the thread. I see now my questions lead to real world discussions. Please when explaining, say if it is real world data or FS, and how to apply it to FS, if possible. Thanks.:)

 

Yep, the 737 is a tad different, but not too much. Most of the basic procedures

are about the same. And everything I say applies to real world, as I fly my sim

the same as real world. Which requires a better airplane than the default..

You can not fly as in real world with the default FSX jets. That's why I hung em

up, and don't use them anymore. :p

[dspaulding]

MBKHOU,

Some thoughts:

 

 

-Do you mean full flaps isn't used in real life because ir produsces to much drag? In FS the opposite happens it seems. With more flaps you need less runway to lift off.

 

 

Do me a favor and TO full flaps with 2 engines failed at Vr. Let me know how you do climbing. That's the reason. You now have half the thrust you originally had. But try it. I'm curious to know what happens. Try it even with a 737. Smaller plane, right? Fail an engine at Vr with full flaps TO.

[il88pp]

I will try taking off a little differently the coming flights. Not right now.

[dspaulding]

Be sure to do it at MTOW. That's the worst case scenario.

[il88pp]

I think this is going off in a different direction. I agree that if all engines fail you will be in some trouble. And if one engine fails on rotation, flying, in a 747 is possible, but in a 737 it is a lot harder, if not impossible. Trying to stop on the runway may be a better option.

I'm not going to do many prctice flights to test that out.

And I will pull out of this discussion here. There is to much conflicting information given by everyone.

I know how I like to fly in fsx, and I don't aspire to become an airline pilot. It works for me.

Thanks for all your information everyone. I will think about it more.

 

MBKHOU,

I somehow missed you reply earlier. The thread is was moving fast.

Thank you for clarifying. Since my points here are all about the default aircraft, it seems we were comparing apples and pineapples:).

Maybe the default jets do indeed not follow real world speed values very closely. They have their own, different behaviour.

 

Thank you all,:)

il88pp

[MBKHOU]

Maybe the default jets do indeed not follow real world speed values very closely. They have their own, different behaviour.

il88pp

 

The flight model of the default 737 is not horrible, but the limited systems don't allow one

to fly as you usually would in the real world. The engine modeling is also much more

accurate with the NGX, than with the default plane.

As an example, the default plane has one idle setting. The real plane has different idle

settings for the various stages of flight, which the NGX simulates.

I could go on for days detailing the various differences and shortcomings with the default

plane. But I'll spare you for now.. ;)

To me, the airplane is everything. Without an accurate aircraft simulation, FSX is nothing

but a scenery display program. That why I bought the airplane long before ever

upgrading any of the scenery.

If I ever decide to play 747 buoy, you can take it to the bank I'll be using the new

747 that PMDG is fixing to come out with. It will make the default 747 feel like a

Fisher Price toy, as does the NGX vs the default 737.