Pitched up but descending?

SixPapaCharlie

SixPapaCharlie

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Okay, someone explain to me how this works.

I am fortunate that I like and work a handful of miles from DFW.
I am driving home tonight and notice something I have seen many times but sort of realized the physics is not quite making sense.

Airliner is seemingly pitched a few degrees up yet descending.
How does this work?

Obviously, it is not doing a falling leaf down to the numbers. Is it just my perspective and I am not seeing it as I think I am or is there some other piece to the puzzle?

on our checkrides, the DPE makes us do the slow flight thing with the stall horn going off and we can't lose alt...

These big jets "appear" to be in a flare attitude several hundered feet up and miles out.
How does that work?

Thanks,
 
That pitch attitude, combined with that airspeed, yields the proper lift for the profile.
I'm sure you can in your Cirrus pull power back and keep the nose up and still descend without stalling.

Not sure if that answered your question..??
 
SixPapaCharlie said:
on our checkrides, the DPE makes us do the slow flight thing with the stall horn going off and we can't lose alt...

These big jets "appear" to be in a flare attitude several hundered feet up and miles out.
How does that work?

Thanks,
Click to expand...

During slow flight and/or MCA you can descend or climb also. Always teach that to my students. That's basically what an airliner is doing except it's configured for landing and at a safe airspeed. Yours didn't teach you this 6PC, or ya screwing with us?
 
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Cpt_Kirk said:
In all honesty, I hope this is a joke.
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I get it. but I don't understand the physics.
The wing has a positive angle of attack w/o airflow separation but it is settling down.

This is not so much a flying question as it is an understanding of what the airflow is doing.

I know they are not toying w/ the stall speed as we are doing during slow flight. When I am on final, I an 20 kts above stall speed.
During slow flight, I am on the cusp of stalling. The airliners are likely not on the cusp of stalling.
 
SixPapaCharlie said:
I get it. but I don't understand the physics.
The wing has a positive angle of attack w/o airflow separation but it is settling down.

This is not so much a flying question as it is an understanding of what the airflow is doing.

I know they are not toying w/ the stall speed as we are doing during slow flight. When I am on final, I an 20 kts above stall speed.
During slow flight, I am on the cusp of stalling. The airliners are likely not on the cusp of stalling.
Click to expand...
The AOA is well below the critical AOA.

You can descend with the nose high... think MCA.
 
Pitch for airspeed, power for descent....the pitch you see is what is required for the proper airspeed in the landing configuration.
 
I guess so. When I am in a stabilized approach, my nose is pitched down.
Just different w/ different aircraft I guess. At any rate, it struck me tonight looking at this giant plane descending with the nose up.
 
SixPapaCharlie said:
I guess so. When I am in a stabilized approach, my nose is pitched down.
Just different w/ different aircraft I guess. At any rate, it struck me tonight looking at this giant plane descending with the nose up.
Click to expand...

Remember the FB thing someone else posted.

Flapping my arms generates lift, but I certainly ain't flying.

So in the scenario of nose high at lower power (low side of the power curve), you're generating enough lift to not stall, but not enough lift to counteract gravity.
 
SixPapaCharlie said:
I get it. but I don't understand the physics.
The wing has a positive angle of attack w/o airflow separation but it is settling down.

This is not so much a flying question as it is an understanding of what the airflow is doing.

I know they are not toying w/ the stall speed as we are doing during slow flight. When I am on final, I an 20 kts above stall speed.
During slow flight, I am on the cusp of stalling. The airliners are likely not on the cusp of stalling.
Click to expand...

SixPapaCharlie said:
Just different w/ different aircraft I guess.
Click to expand...
It really all comes down to the additional lift devices on aircraft and their relationship with speed.

Look at the different approach angles between this CRJ 200:

And this CRJ 700:

Now, understand I'm not typed on either airplane and I'm sure a few people here can explain the systems in detail much better than I can, but the 700 is equipped with leading edge slats, unlike the -200. You'll notice that while the approach speeds might be similar, the approach angles are quite different (-200, nose down; -700, nose level, if not inclined). Now, this assumes the weights are similar and yadda, yadda, yadda, but the point I'm trying to get across is that the deck angles are really a factor of additional lift device positions and speed.

I feel like I'm falling short of being able to adequately explain this to you, but I'm trying to think of some examples to relate to your experience.

Edit: A330's are known to have a high deck angle on their approaches.

I guess the point I'm trying to get across is that you have to completely forget about the cabin and just try to isolate the wing in regards to the aerodynamics. The wings are flying (clearly). As the additional lift devices are deployed (flaps and slats), they change the camber and ah, f*ck it. I understand it, but not enough to explain it simply.

I wish I could just show you in the Pilatus. It has a significant change when going from 0* to 40* at varying speeds.
 
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Maybe I don't understand your question...?

The pitch / power combo is what's needed to maintain the desired path & speed.

Seeing as though the AOA is less than the critical AOA, no stall will occur.
 
Cpt_Kirk said:
It really all comes down to the additional lift devices on aircraft and their relationship with speed.

Look at the different approach angles between this CRJ 200:

And this CRJ 700:

Now, understand I'm not typed on either airplane and I'm sure a few people here can explain the systems in detail much better than I can, but the 700 is equipped with leading edge slats, unlike the -200. You'll notice that while the approach speeds might be similar, the approach angles are quite different (-200, nose down; -700, nose level, if not inclined). Now, this assumes the weights are similar and yadda, yadda, yadda, but the point I'm trying to get across is that the deck angles are really a factor of additional lift device positions and speed.

I feel like I'm falling short of being able to adequately explain this to you, but I'm trying to think of some examples to relate to your experience.

Edit: A330's are known to have a high deck angle on their approaches.

I guess the point I'm trying to get across is that you have to completely forget about the cabin and just try to isolate the wing in regards to the aerodynamics. The wings are flying (clearly). As the additional lift devices are deployed (flaps and slats), they change the camber and ah, f*ck it. I understand it, but not enough to explain it simply.

I wish I could just show you in the Pilatus. It has a significant change when going from 0* to 40* at varying speeds.
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Nah, this makes a lot of sense
The physics is the same but I am comparing light single to significantly different aircraft.

I got it. When I land a 172, I am pitched up moresoe than the Cirrus but neither airplane is about to fall out of the sky.
Apples to oranges in this case.
 
SixPapaCharlie said:
Airliner is seemingly pitched a few degrees up yet descending.
How does this work?

Obviously, it is not doing a falling leaf down to the numbers. Is it just my perspective and I am not seeing it as I think I am or is there some other piece to the puzzle?

on our checkrides, the DPE makes us do the slow flight thing with the stall horn going off and we can't lose alt...

These big jets "appear" to be in a flare attitude several hundered feet up and miles out.
How does that work?

Thanks,
Click to expand...
I think the answer you're looking for is slats. Just slats.
 
Because I'm not smart enough, here's a video. The wing with a slat is at the end, but I suggest watching it to get a visual representation of the aerodynamics.

Great video, by the way. I've referenced it numerous times.

 
Tarheelpilot said:
Nothing. It was a joke. Personally I love ❤️ d->
Click to expand...
not.jpg
 
Cpt_Kirk said:
I think the answer you're looking for is slats. Just slats.
Click to expand...
Slats do change the chord line, thus affecting AOA. Without slats, swept wing aircraft would need to fly everything at higher speeds.
 
In non-technical terms, it works for the same reason you need power in slow flight to keep from descending even though your nose is way up in the air (on your third lesson as a student pilot ;)). It's also the same thing you do on a short field over an obstacle landing. It's just getting to a point in the lift curve where the effects of drag are greater than lift, so you descend.

If you didn't realize the connection between this and basic pilot maneuvers, you are not alone. The number of pilots who, high in final, push the nose down to dive at high speed (increasing their overall energy) rather than pull the nose up to descend (maintaining or decreasing their overall energy) tells me that.

In the case of the airliner, there may well be equipment that assists with accomplishing that lift/grad equation, but the basics are pretty much the same.
 
Zeldman and ICR gave the simplest answer, the rest doesn't matter. The wing needs to produce enough lift to support the weight of the plane. The amount of lift can be increased or decreased by changing airspeed or AOA. At ANY given AOA, the airspeed will determine how much lift is produced. So, there is a power setting that will support level flight (ignoring the frontside of the curve) and below that, the aircraft will descend(eventually).

Think about it this way. If you were to pull the power halfway back shortly after takeoff and maintain the climb out attitude, what would happen?
 
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It has to do with the angle of the dangle but only if the full moon was on the Tuesday before the first flight of the condor in eastern time zone before daylight savings time in the west.

Seriously though BiRon, did you not watch the spotry's videos or the king people? They explain most if it in a very interesting way. And if you pay attention their is brief nudity in both video series!
 
A stall is when the wings is done flying and they are not providing lift. When you are on the backside of the power curve you are nose up with the wings not stalled(the wings are providing lift still) you are using the power of the plane to hold you at that altitude. If you pull power out and and keep the same attitude you will begin to descend without a change in attitude because you are not producing the same amount of power. I needs to make up that lack of power that you just took away from it so it has to descend, if you try and stop this descent the wings will slow and stall.
 
6PC when you go up in a C172 try a landing with a no flap landing, and then one with full flaps. You'll see the difference.
 
SixPapaCharlie said:
I guess so. When I am in a stabilized approach, my nose is pitched down.
Just different w/ different aircraft I guess. At any rate, it struck me tonight looking at this giant plane descending with the nose up.
Click to expand...
When I'm flying level in slow cruise in a 172 or 182 -- which is essentially downwind speed, not all that slow -- I'm pitched to +10 deg.

I only get the nose below level when descending with full barn door flaps, which essentially rotates the wing for me.
 
this thingy (Day 1 minute 1 of student pilot training):


forces_of_flight.jpg



plus this other thingy (Day 2 of student pilot training):




anglattack.gif




should get you closer to your answer.
 
eman, as I was scrolling down, I was looking for exactly that. Glad I wasn't disappointed!
 
You'll notice the CRJ-200's have an exaggerated nose down pitch on approach... (unless they're doing a no flap landing) As others have pointed out, it has to do with not having leading edge slats and having very high approach speeds (140+)

The ERJ-135/140/145 are opposite in that they tend to have a very high nose up pitch on approach. While they don't have leading edge slats, they have Vortilons that improve low speed handling. Often time, you can see Vref speeds in the low 120's which is much slower compared to the CRJ-200.
 
The 700 and 900 both have high ref speeds and have that slight nose up landing attitude. 737 also has a pretty high ref speed and lands slight nose up.
 
jordane93 said:
The 700 and 900 both have high ref speeds and have that slight nose up landing attitude. 737 also has a pretty high ref speed and lands slight nose up.
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They all have leading edge flaps/slats. Jets without leading edge devices will have a pronounced nose-down attitude on approach.
 
As much as Bryan does seem to troll, I think his question was legitimate. And I think the answer has already been answered. But let me take a stab at the answer. Hopefully I am at least partially correct.

When you extend flaps on your typical Cessna, the center of lift moves aft on the wing. That results in a nose low pitch attitude. Now, when you add leading edge devices to the wing, that causes the center of lift to move FORWARD on the wing, resulting in a nose high pitch attitude. On airplanes that have leading edge devices, they typically are the first thing that extends, resulting in a nose high attitude. As the trailing edge devices come out, the pitch attitude flattens out some but the result is still a nose high pitch attitude on final.

Some, if not all of the DC-9 series and a lot of the Embraer series of Aircraft don't have leading edge devices so they have a nose down attitude on final.
 
This is what happens when you land it "like in the cirrus"

Clear as mud? #TheCirrusLife
 
Ok this makes a lot of sense. At osh, the STOL planes also land with a high pitch up attitude and many had slats I the front of the wings.
 
redrum4me said:
I would hope that this is a place where a person could ask a aviation related question and not get ridiculed.
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I understand your point.

1. The OP does tend to joke around and instigate at times and I wanted to be sure this wasn't one of those times.
2. I wanted to be sure because I was going to spend a bit of my time making sure he truly understood this concept for the safety of himself, his family, and all others underneath and around his flight path.
3. I think the posts afterwards did answer his questions without undue ridicule.
4. I think he'll continue to ask questions from here on out, regardless of how may be perceived.

Aerodynamics is the most important aspect of flying an airplane and, unfortunately, it's one of the most misunderstood.
 
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