With a reduction in airspeed you need an increase in angle of attack to maintain level flight. With an increase in angle of attack you have more drag, therefore you need an increase in power to maintain slower flight.
Well we know less speed means less lift so ... we still want to stay at the altitude for maintaining level flight . So what we do now is to increase angle of attack so that we increase the speed of air and reduce static pressure on the upper cmaber again . But point is the less airspeed we have the more downwash we get which leads to having more induced drag . Now to overcome the drag we need to use more power to maintain the speed .
The other two answers which mentioned induced drag are correct. There are two main kinds of drag acting on an aircraft. Parasitic drag is what you encounter just by moving through the air. Even cars on the road experience this, which is why car manufacturers have wind tunnels. Parasitic drag is proportional to speed squared. That's why the right half of the curve goes up so sharply. For those who are interested, the actual equation is Dp = Cdp•A•½•ρ•V². For a specific plane at a specific altitude, those terms are all more or less constant except V. Induced drag is a side effect of generating lift. The faster a plane goes, the more lift the wing can generate, and the slower the plane goes, the harder the wing has to work to keep the plane in the air (this is a crude way to put it, but whatever). The stall speed is the speed where the wing just can't do it any more. It turns out that induced drag increases as the plane goes slower. Di = k•W² / AR / (½•ρ•V²•S); again, see where the V term appears in the equation. Power required is drag times speed. Add the two drag curves together, and you have the curve shown in the video. The curve has a low point, which is the point where the plane needs the least power to fly. I've flown at that speed long distance to see if I could do it, and it's hard work. Any deviation at all, and you start losing altitude, which can only be regained by increasing power.
I believe this is an area of serious concern. I am a CFI with over 3000 hours in the right seat. Every now and then I come across some pilots (and instructors) that emphasising on the landing while stall warning is screaming out. In the US it seems this technique is very popular and they even have a name for it "Full-Stall Landing"!!! They put the aircraft in the area of reverse command so close to stalling the aircraft during the round-out over the runway before touchdown, and they are so adamant about their technique that they don't even want to listen to any contrary opinion. I have flown in different countries and different systems CASA, EASA and FAA. It seems that the FAA is the only one that let this procedure to be conducted by their pilots. During the incipient stall and the recovery phase, instructors teach the students to recover (go-around) at the first symptoms and indications of an approaching stall, then how could the same instructors justify letting the aircraft flare and land while in a full-stall (or region of reverse command and beyond). If you are an instructor please consider reviewing this technique if you come across it. With such a low speed and low distance above the ground, in case of a go-around decision, you are in a very bad situation. Good luck everyone.
CFI in training here. yeah, I just had my DPE tell me on my commercial checkride to land with the stall warning going off in order to have smoother landings. but yeah, I didn't even consider the idea that by doing that, you're not really in a good position for go-arounds
Please correct me if I'm wrong, but in answer to your question at the end: your angle of attack is higher, so your lift vector will point further backwards, your airspeed is slower, so your wing will need to create more lift with a higher angle of attack, and with increased lift comes an increase in induced drag, and also, because of your higher angle of attack, you present more of the aircraft surface to the relative rearward airflow, hence creating more parasite(?) drag... I think that's it, but if I'm wrong, please correct me, thanks!
Reducing speed means a lower cruise altitude, which means more drag due to the thicker air, which is why you can't fly fast at low altitudes unless you have the power to push the plane that fast.
Not really. Yes, air is denser at lower altitudes but not enough to be relevant here. What you need more power for here is the increased drag when pitched up at higher angle of attack. At slower air speeds you need a higher angle of attack to wash down the same amount of air, thus you have more drag.
@@freddyfreeloader1200 these graphs assume a constant angle of attack. I think a better explanation can be had by comparing power required with total drag as they are the same, at any speed below minimum drag, drag actually increases meaning you need more power for less speed (IAS), this is referred to as area of reverse command or being speed unstable
at what airspeed (or range) does the bottom of curve occur? eg piper warrior (assume ea model may be slightly different). eg I'm practicing slow flight or power off stall, I pull power back and pitch up to maintain alt. As the flaps get added and airspeed drops, where do I need to start adding back a little power to maintain alt. ? Another way to say it is: in cruise, pitch varies altitude and power varies speed whereas in slow flight, pitch varies speed and power varies altitude....at what airspeed (or range) does that switch over take place?
You probably don't want to fly slower, so saying "You need more power to fly slower" seems awkward to me. What might really happen is that you notice that you are TOO slow, nearing a stall, so you increase power, only to find that you fly slower. So maybe you say, "An increase in power will actually REDUCE your airspeed and bring you closer to a stall." Why does this happen? It's because at the high angle of attack, there is a significant rear-facing component of lift. Add power, increase lift, increase the rearward component (also known as induced drag), and the plane's airspeed drops. Adding power might also further increase the angle of attack - not good. What to do? LOWER THE NOSE, THEN add power to recover airspeed, then keep the pitch and airspeed in the desired range. COMMENTS? I'm just a student, but this is what I think.
Yah .these concepts can be quite mind-boggling and confusing at first. What you're experiencing is normal, so don't feel bad. I would suggest just to keep revisiting the subject from time to time, while also flying it in the airplane. Learning is a change of behavior based on experience. So the more time and effort that you spend on the subject, the more clear it will become. I felt the same frustration 40 years ago when I first started learning this .. keep the faith. Some concepts just don't come overnight.
With a reduction in airspeed you need an increase in angle of attack to maintain level flight. With an increase in angle of attack you have more drag, therefore you need an increase in power to maintain slower flight.
you help me so much thanks dude
Yes because as the angle of attack increase so does the induced drag. Therefore more power is needed to over come this additional drag
Well we know less speed means less lift so ... we still want to stay at the altitude for maintaining level flight . So what we do now is to increase angle of attack so that we increase the speed of air and reduce static pressure on the upper cmaber again . But point is the less airspeed we have the more downwash we get which leads to having more induced drag . Now to overcome the drag we need to use more power to maintain the speed .
The other two answers which mentioned induced drag are correct.
There are two main kinds of drag acting on an aircraft. Parasitic drag is what you encounter just by moving through the air. Even cars on the road experience this, which is why car manufacturers have wind tunnels. Parasitic drag is proportional to speed squared. That's why the right half of the curve goes up so sharply. For those who are interested, the actual equation is Dp = Cdp•A•½•ρ•V². For a specific plane at a specific altitude, those terms are all more or less constant except V.
Induced drag is a side effect of generating lift. The faster a plane goes, the more lift the wing can generate, and the slower the plane goes, the harder the wing has to work to keep the plane in the air (this is a crude way to put it, but whatever). The stall speed is the speed where the wing just can't do it any more. It turns out that induced drag increases as the plane goes slower. Di = k•W² / AR / (½•ρ•V²•S); again, see where the V term appears in the equation.
Power required is drag times speed. Add the two drag curves together, and you have the curve shown in the video. The curve has a low point, which is the point where the plane needs the least power to fly. I've flown at that speed long distance to see if I could do it, and it's hard work. Any deviation at all, and you start losing altitude, which can only be regained by increasing power.
I believe this is an area of serious concern. I am a CFI with over 3000 hours in the right seat. Every now and then I come across some pilots (and instructors) that emphasising on the landing while stall warning is screaming out. In the US it seems this technique is very popular and they even have a name for it "Full-Stall Landing"!!!
They put the aircraft in the area of reverse command so close to stalling the aircraft during the round-out over the runway before touchdown, and they are so adamant about their technique that they don't even want to listen to any contrary opinion. I have flown in different countries and different systems CASA, EASA and FAA. It seems that the FAA is the only one that let this procedure to be conducted by their pilots.
During the incipient stall and the recovery phase, instructors teach the students to recover (go-around) at the first symptoms and indications of an approaching stall, then how could the same instructors justify letting the aircraft flare and land while in a full-stall (or region of reverse command and beyond). If you are an instructor please consider reviewing this technique if you come across it. With such a low speed and low distance above the ground, in case of a go-around decision, you are in a very bad situation.
Good luck everyone.
CFI in training here. yeah, I just had my DPE tell me on my commercial checkride to land with the stall warning going off in order to have smoother landings. but yeah, I didn't even consider the idea that by doing that, you're not really in a good position for go-arounds
Slower airspeed = higher angle of attack = GREATER Induced drag = MORE POWER REQUIRED to fly at slower airspeed.
As aircraft flies slower, induced drag is going up rapidly, thereby total drag would increase much.
So we need more power to compensate it I think
Please correct me if I'm wrong, but in answer to your question at the end: your angle of attack is higher, so your lift vector will point further backwards, your airspeed is slower, so your wing will need to create more lift with a higher angle of attack, and with increased lift comes an increase in induced drag, and also, because of your higher angle of attack, you present more of the aircraft surface to the relative rearward airflow, hence creating more parasite(?) drag... I think that's it, but if I'm wrong, please correct me, thanks!
When I become confused about something in my lesson,it is the first place that I come...thank you so much 😊😊
You're welcome 😊
Because of more drag.
Amazing video!
Another superb video! Is there a follow up video? Thank you 😊
Make a video on normal command and reverse command please it would be very helpful for aviation students
Such a great idea. Thank you!
Thank you for oVery easy explanation
Thank you for the positive feedback.
To maintain altitude?
Why there is no verbal explanation?
Bottom of the curve is Best Glide?
Reducing speed means a lower cruise altitude, which means more drag due to the thicker air, which is why you can't fly fast at low altitudes unless you have the power to push the plane that fast.
Not really. Yes, air is denser at lower altitudes but not enough to be relevant here. What you need more power for here is the increased drag when pitched up at higher angle of attack. At slower air speeds you need a higher angle of attack to wash down the same amount of air, thus you have more drag.
@@freddyfreeloader1200 these graphs assume a constant angle of attack. I think a better explanation can be had by comparing power required with total drag as they are the same, at any speed below minimum drag, drag actually increases meaning you need more power for less speed (IAS), this is referred to as area of reverse command or being speed unstable
at what airspeed (or range) does the bottom of curve occur? eg piper warrior (assume ea model may be slightly different). eg I'm practicing slow flight or power off stall, I pull power back and pitch up to maintain alt. As the flaps get added and airspeed drops, where do I need to start adding back a little power to maintain alt. ? Another way to say it is: in cruise, pitch varies altitude and power varies speed whereas in slow flight, pitch varies speed and power varies altitude....at what airspeed (or range) does that switch over take place?
my cfi said not specific speed but in the 60ish area. any other info from you folks still appreciated
Because of induced drag
You probably don't want to fly slower, so saying "You need more power to fly slower" seems awkward to me. What might really happen is that you notice that you are TOO slow, nearing a stall, so you increase power, only to find that you fly slower. So maybe you say, "An increase in power will actually REDUCE your airspeed and bring you closer to a stall." Why does this happen? It's because at the high angle of attack, there is a significant rear-facing component of lift. Add power, increase lift, increase the rearward component (also known as induced drag), and the plane's airspeed drops. Adding power might also further increase the angle of attack - not good. What to do? LOWER THE NOSE, THEN add power to recover airspeed, then keep the pitch and airspeed in the desired range. COMMENTS? I'm just a student, but this is what I think.
During an approach to landing an aircraft is in reverse command region?
Negative because you are trading altitude for airspeed and therefore additional power is not needed to maintain level flight.
Thx u so much
You're welcome!
Yes
i dont gte it
Yah .these concepts can be quite mind-boggling and confusing at first. What you're experiencing is normal, so don't feel bad. I would suggest just to keep revisiting the subject from time to time, while also flying it in the airplane. Learning is a change of behavior based on experience. So the more time and effort that you spend on the subject, the more clear it will become. I felt the same frustration 40 years ago when I first started learning this .. keep the faith. Some concepts just don't come overnight.
So this is the same as slow flight
Indeed. This theory applies to slow flight. Thank you!