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cmbaviator

Not enough "nose heay" during flare ?

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Hi Guys,

 

I haven't been flying the 747v3 for months and restart flying since the -800. I messed up my flare as i Floated way too much even though it was within the LZ. But I notice that even when I released the yoke, the pitch was decreasing very very slowly. 

As far as i understand ground effet, it has mainly two effects :

1) as you approach closer to the ground, the vertcial speed will increase due to more lift

2) as you approach closer to the ground, the aircraft is subject to a negative ( nose down) torque.

the 1) seems to be spot on but however I still reserved on 2), it seems that the decrease of pitch is due to the lost of speed after retarding the throttle.

I own the 737/777/747 and all have the same issue with 2) unless i'm completely wrong.

Before i was flying with the IXEG B737-300, and you can really feel the nose down effect after passing 60 feets, you needed to hold a bit more back pressureto maintain your ROD until flare.

Also do you need to retard earlier ? here is a video of my landing

 

 

 

Edited by cmbaviator

Camille MOUCHEL-BLAISOT ( CMB )

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8 minutes ago, cmbaviator said:

-800

8. There is no such thing as an 800.

8 minutes ago, cmbaviator said:

Also do you need to retard earlier ?

For not knowing the proper landing technique enough to know when to retard the throttles, among other things, I find the thread title a little inappropriate, honestly.


Kyle Rodgers

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I mostly fly A320 or B737-300 on Xplane, you usually retard at 20-30 feets, i was wondering if its the same for the 747 or you should retard between 30-40 fts ?

innapropriate ?

 

This topic is about the negative torque induced by ground effect and if the 747 should be affected or not because currently it doesn't feel at all

 

It gets better: All of these effects are reversed when landing. In other words, when we least want a reduced indicated airspeed, a nose-down moment, or a decrease in drag and thrust, that’s what we get. It’s no wonder primary students can have trouble with their landings.

 

source : http://www.aviationsafetymagazine.com/issues/35_10/features/Using-Ground-Effect_11069-1.html

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Camille MOUCHEL-BLAISOT ( CMB )

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4 minutes ago, cmbaviator said:

I mostly fly A320 or B737-300 on Xplane, you usually retard at 20-30 feets, i was wondering if its the same for the 747 or you should retard between 30-40 fts ?

innapropriate ?

Yes, inappropriate. Granted, English may not be your primary language, so I will grant that you might not have intended it, but the thread title comes across as "your plane is incorrect," while your post itself contains many questions that show that your experience does not match up with the claim of the thread title.

To me, it is inappropriate to make an assertion from the point of limited experience. I don't fly helicopters. I'm not going to open a thread about a helo simulation and question its accuracy for something this specific. Moreover, I'm not going to cite generic sources (and yours was written for single-engine GA pilots, largely).

Try using the information you have cited to land the MD-11, for example. Aircraft all follow the basic laws of aviation, but to lump them all into this idea that "a plane is a plane, and they'll all follow this random article I've quoted" goes against the laws of physics, and the facts of the situation. Why, for example, might one have to get a type rating for different types of aircraft? The answer is not only related to how the systems are set up, or the buttons on the flight deck - it's because planes have different flight characteristics, as well.

If you were to quote an article about mastering stalls in aircraft, and then go up in a 747 to attempt to use that same knowledge, you'd find yourself having a bad day, very quickly.


Kyle Rodgers

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i'm not asserting, I'm just asking if it's normal or not to not feel the nose down effect in 747 heavy during flare, it's a question and i'm just expecting developpers or real pilot to confirm it or not.

 

 

 


Camille MOUCHEL-BLAISOT ( CMB )

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In a General aviation single engine prop (C172 for example) you flare by holding the airplane a few inches off the ground and basically let it stall.

You can‘t do that with a 200 tons airliner. 

30 ft is ok to „close the throttle“ respectively retard the thrust levers. But don‘t wait the airspeed to slow down, it won‘t do that enough. This airplane is sluggish. You will run out of runway before it sits down by itself.

rather fly it on the ground. To flare an airliner means you don‘t stall it but you simply reduce the decent rate. Check your speed being at Vref moments before touch down when you close the throttles, then lift the nose a bit, however, fly it onto the runway, when touched down, your spoilers will deploy, your autobrakes will kick in, your lift is destroyed, now fly the nose down to the ground. Push. Thats all.

 

happy landings


,

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The 747 is a very different beast to to the 737 in terms of flying characteristics -- the Jumbo is, by and large, extremely stable and surprisingly responsive for an aeroplane of its size. When it comes to control inputs less, generally, is more, particularly in the roll axis.

The one area I think may be lacking a little in the PMDG model is the thrust-pitch couple -- my understanding of the real thing is that there is quite a strong coupling (i.e. if you reduce thrust the nose should pitch down quite positively and vice versa) which isn't really replicated well in FS as a whole.

However, that said if you are asking why you floated, the answer is quite simple: not so much a late reduction of thrust as too much flare. The pitch change in the flare in the 747 is really quite tiny -- only about two degrees at the most, which is just barely enough to determine that the pitch has changed at all (i.e. the exact moment you see the horizon move down relative to the top of the glareshield -- that's about two degrees and you should stop there!). In your video, if you look at the ADI you will see your pitch change is closer to 4 degrees -- i.e. nearly double the recommended amount.

The FCTM contains full details of the recommended technique.

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Simon Kelsey

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8 minutes ago, skelsey said:

is the thrust-pitch couple -- my understanding of the real thing is that there is quite a strong coupling (i.e. if you reduce thrust the nose should pitch down quite positively

Isn‘t that obsolete with the fly by wire in the -8 and 777/787?


,

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1 minute ago, Ephedrin said:

Isn‘t that obsolete with the fly by wire in the -8 and 777/787?

Probably! Sorry, I always forget that this forum includes questions about the -8 -- comments above reference the -400 :).


Simon Kelsey

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5 minutes ago, Ephedrin said:

Isn‘t that obsolete with the fly by wire in the -8 and 777/787?

The -8 isn't FBW...


Kyle Rodgers

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Thank you for your inputs.

I may  have over pitched up as i thought i may need to hold more back pressure to counteract the pitch down moment (main subject of this topic)  normally induced during ground effect


Camille MOUCHEL-BLAISOT ( CMB )

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1 hour ago, scandinavian13 said:

The -8 isn't FBW...

I‘ve just read about the 748. I was pretty wrong about it, I really thought it was fbw, brought to the standard of the 777... so basically it has the same flight controls as the 744... I wonder why it feels so different from the 744. since I thought it was fbw I flew it just like the 777 and there wasn‘t much difference. I didn‘t notice a change of the pitch and bank when I didn‘t touch the yoke. Is it just that stable? 


,

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3 minutes ago, Ephedrin said:

Is it just that stable? 

Different wing. Different engines. Longer.

Keep in mind that the 748 was aimed at keeping the type certificate the same. Entirely redesigning the flight control system wouldn't exactly be a good idea for maintaining that kind of commonality. This includes the bleed-based ECS, despite using the GEnx engine developed for the 787, which was designed to be bleedless, but a variant was developed for the 748 - again, commonality.

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Kyle Rodgers

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2 minutes ago, Ephedrin said:

I‘ve just read about the 748. I was pretty wrong about it, I really thought it was fbw, brought to the standard of the 777... so basically it has the same flight controls as the 744... I wonder why it feels so different from the 744. since I thought it was fbw I flew it just like the 777 and there wasn‘t much difference. I didn‘t notice a change of the pitch and bank when I didn‘t touch the yoke. Is it just that stable? 

It has a very different wing.  Note how much more fuel the Main 2 & 3 now hold compared to B744.  I would say it has the same controls as the B744, although similar for type rating the outboard ailerons are electronically controlled.. this only affects low speed flight.  The new wing and the longer body no wonder it handles differently.  Kyle beat me.

The OP question about torque effecting a nose down moment due to aerodynamics sounds reminiscent of a discussion I've read here before that is always initiated by someone from the XPlane audience.  Seems to be a thing in that crowd.  It doesn't apply to the B747.

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Dan Downs KCRP

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5 minutes ago, downscc said:

The outboard ailerons are electronically controlled..

Then I think that‘s what I read and substituted to the whole airplane.


,

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