MERGED power curve / floats posts

[aeroncasuperchief]

The 4 forces, everyone knows those,,, lift weight thrust and drag. As induced drag (And form drag also, in the backside ) goes up, you must counteract with more thrust. lift and weight will be equal and opposite. I don't give a rats ass HOW you get there ( everyone in the know knows you need to use pitch in order to increase AOA to get more drag ) my simplified statement is this : the lift /weight equation is satisfied at a lower airspeed BECAUSE of thrust. You CANNOT go into the backside regime without increasing thrust to counteract drag, therefore the statement : To go slower, you MUST increase thrust (power) is factually correct! I don't need anyone to explain aerodynamics to be , I started out by having a simplified discussion in a BAR ROOM !! and now I am being told I am ignorant? Those who try to counteract a clear fact in physics and aerodynamics are trying to Obsfucate the facts and are the true TROLLS !

[Zaibatsu]

Of course you can go slower without increasing power. You just can’t stay there without losing altitude or stalling.

Still useless for landing anywhere you can take off from.

[Zaibatsu]

Oh... and for slow flight... which is on the back side of the power curve..... how do you recover?

I’ll stick with Aux Bats method of adding power to recover. He seems to know a little bit of what he’s talking about.

[Chris M]

You CANNOT go into the backside regime without increasing thrust to counteract drag, therefore the statement : To go slower, you MUST increase thrust (power) is factually correct!

Again, no.

You can't maintain ALTITUDE on the backside without increasing power.

You can leave the throttle at idle and sit around on the backside of the curve as long as you want, you'll just have a progressively steeper approach angle the slower you go and eventually meet the ground. I fly all my short field approaches on the backside of the power curve with the throttle at idle.

I also fly gliders for hours at a time below best L/D. I don't have a throttle to increase. Somehow I manage to stay there just fine.

Please answer me this: You're flying along and reduce power to idle. You also raise the nose and let the plane slow to the edge of stall, then hold the AOA there without letting it stall. You don't add power. What happens?

[Aviatard]

In my experience, and as a general rule, you can determine the craziness / trollness of a poster by counting the number of words spelled in ALL CAPS, and dividing by the number of exclamation points used. Multiple commas ,,, used as elipses are also a clue that the person is a nutbar.

[youhavecontrol]

There's a pretty good video that I think describes exactly what aeroncasuperchief is getting at:
https://www.youtube.com/watch?v=fT7pFSfVZBI

[aeroncasuperchief]

Still useless for landing anywhere you can take off from.

IF one is flying into a 1 way strip and must land in a tailwind, the take-off will be in a headwind and so the runway is too SHORT for a front side of the lift/power curve but is ok for a take-off. It is fine for a backside approach though. This is an example where you cant get in but can get out IF you do not use the tools of the trade and approach in the backside !

You need to get out of your mommys basement apartment and go flying in the real world !

[aeroncasuperchief]

I also fly gliders for hours at a time below best L/D. I don't have a throttle to increase. Somehow I manage to stay there just fine.

Max L/D is at best range. Best endurance is at a much lower airspeed ( min power) As a Hang glider pilot, We are close to the stall in order to maximize lift and best glide in a tight light thermal BUT will alter the airspeed for various reasons ( thermal size and strength is 1, turbulence and the drop off the falls at the edge of the thermal is another) We will even use best range if the thermal is big so as to reduce workload!

[trey kule]

I think the problem Asuperchief is that you might not be able to accurately reproduce slow flight performance on your FlightSim.

[aeroncasuperchief]

Why use a flight sim when you can do the real thing in a real airplane, instead of guessing at how a plane flies or trying to explain the theory behind it? Trey, I probably put away my old PC flight sim before you were born

[aeroncasuperchief]

proficiency.jpg (31.82 KiB) Viewed 753 times

PROFICIENCY: BEHIND THE POWER CURVE
WHERE IT TAKES MORE POWER TO FLY SLOWER
November 5, 2013 By Thomas A. Horne
One glance at the power curve immediately tells you that it takes as much power to fly very slowly (A) as it does to fly at cruise speed (B) in this curve representing a hypothetical piston single. Meanwhile, (C) shows the power needed for maximum endurance, and (D) shows the value for maximum range.
One glance at the power curve immediately tells you that it takes as much power to fly very slowly (A) as it does to fly at cruise speed (B) in this curve representing a hypothetical piston single. Meanwhile, (C) shows the power needed for maximum endurance, and (D) shows the value for maximum range.
You’re on final, and see you’re losing altitude. The VASI lights are all red. The trees are getting closer. It’s clear that on your present approach path you’re on target to land well short of the runway. In an attempt to arrest the descent and set things right, you add power and raise the nose.

Bad move. You’re still sinking, even though you’ve gone to full power in what is now a desperate effort to climb. Welcome to what’s commonly known as the back side of the power curve, or the “region of reversed command.” It’s not a happy place, and it’s worth a review of some basics in order to avoid it. These basics have to do with the relationship between drag and power.

First off, there are two main types of drag. Parasite drag is the drag created by the airframe’s resistance to forward motion. Put your arm out of a car window as it’s cruising down the road—your arm is creating parasite drag. There are subsets of this type of drag, such as cooling drag (drag created by cooling inlets) and interference drag (drag created by flow interruptions and turbulence where wings meet fuselages, and where engine nacelles join wings), but the upshot is the same: the faster you fly, the greater the parasite drag. Double your airspeed, and parasite drag quadruples.

Induced drag is a byproduct of lift, and it’s greatest at high angles of attack and slow airspeeds. In this condition, the lift that supports the airplane’s weight (effective lift) acts vertically but, as always, the total lift generated by the wing acts perpendicular to the wing chord. At high angles of attack, this perpendicular force exerts strong amounts of rearward force opposite to the direction of flight—and that’s induced drag.

So just as parasite drag is highest at high airspeeds, induced drag is greatest when flying slow and nose-high. And the greater the angle of attack and the slower you fly, the more you’ll continue that way. Practicing slow flight at minimum controllable airspeed gives you a good introduction to how an airplane behaves with lots of induced drag.

How to overcome parasite drag? Add more power! But at some point the drag will be too great for the power available, and that’s when you reach maximum level airspeeds. As for induced drag, the problem is trickier. To maintain altitude, you’ll need more power—a lot more, as you continue to increase the attack of attack. But at some point there will come a reckoning. All the power you’ve got simply won’t be able to keep the airplane in the air. It will stall.

This is a much worse outcome than hitting the high-speed wall created by parasite drag. You’re low, slow, powered up, and mushing on short final. The only way out is to lower the nose, reduce the angle of attack and try to go around—here’s hoping there’s enough altitude and time to carry the day.

Lowering the nose to gain altitude, and raising it to lose altitude, may sound counterintuitive, which is one reason why the back side of the power curve is called the region of reversed command. On the front side of the power curve the airplane behaves according to popular notions: raising the nose brings altitude gains, lowering it causes descents.

Is there a dividing line between the front and back sides of the power curve? You bet, and we’ve plotted an accompanying stereotypical power curve (previous page) to show it. Notice the other points we’ve plotted along the curve. At either end of the curve it’s easy to see where the stall speed and redline occur, but it’s also worthwhile noting that it takes as much power to fly this hypothetical airplane at 40 knots (A) as it does to fly at its maximum cruise speed of 120 knots (B).

Point C illustrates the airspeed and power combination that produces maximum endurance. Why? Because this is where minimum power is required for level flight, and where the lowest fuel flows occur. Point D represents the condition for maximum range. Why? Because for just a little more fuel consumption, airspeeds rise significantly higher than in point C.

The power curve’s biggest lessons speak to those flying too low on final. Use all the vertical guidance available when approaching the runway, fly at the proper airspeed and in the proper configuration, and watch your planned touchdown spot for any movement. If it moves toward you, you’re high; if it’s moving away from you, you’ll land short. And you’re probably on the back side of the power curve. Best to add power, go around, and try again. Anything but mushing toward terra firma, as hundreds of pilots have learned the hard way.

Is it enough to post graphs and NASA letters and high time airline pilot letters to show ( not in my words ) that the backside of the power/drag curve requires more power to fly at an even lower airspeed at a specific altitude OR am I dealing with a bunch of nutcases?

[aeroncasuperchief]

Hmm, another dumb airline pilot OR is it certain posters on AvCanada who are "behind the intelligence curve" ?

If you want to maintain a speed below the minimum drag speed, something very interesting happens. To maintain that lower speed, the more thrust is required. This is the total opposite of what we normally do in flight. We reduce thrust to move at low speeds, while we increase thrust to increase the speed. When you fly behind the curve this gets fully reversed. The lower the speed you want to maintain the higher will be thrust demand.

Many airliners approach for landing slightly behind the drag curve. It is not dangerous, if you know how to handle the aircraft in such a situation.

(Being) Behind the drag curve is synonymous with being behind the power curve. Behind the power/drag curve ( area of reversed controls) STARTS at the minimum drag speed.

Apparently, according to some posters, these Airline pilots should not be flying. It is a totally unnecessary and unsafe approach!

[aeroncasuperchief]

https://youtu.be/UzUqsO9R_M4

Here is a video clearly showing flight in the backside requiring more power to fly slower. Even a 10 year old can understand this stuff!

[shimmydampner]

Still useless for landing anywhere you can take off from.

Well that's just plain not true.

[PilotDAR]

Still useless for landing anywhere you can take off from.

An example of an occasion where I used the behind the power curve approach, was landing a 182 amphibian into a very small runway in a Norwegian fjord. I walked the runway (having driven there first), so I knew what to expect. The runway had a noticeable slope downward toward the west, with a manageable over run, was bumpy grass, though with an excellent departure path west. The east end of the runway was an aircraft carrier like serious drop off, and a very upslope departure path toward mountains. There was no wind.

Upon arrival, I flew the runway west to east for on last look, then climbed east to turn around for my approach. I dragged the plane in toward the west, and downslope, touched down where I intended by simply closing the throttle, and with effort, stopped before the small goat fence. Other than for an engine failure during a dragged in approach, I had better assurance of not undershooting than overshooting. I would rather take out the goat fence at the far end, that the whole plane at the approach end. Yes, I could have landed upslope, but I could not touchdown early (that darned goat fence), and if I over ran, it would be off the cliff at the east end. If I had chosen to abort an uphill landing to the east, it would have been toward higher ground.

One might say that I landed into a runway too short from which to takeoff. Well, getting the plane stopped on the downslope use more runway roll distance than my downslope takeoff did, and the departure path was very good, continuing down the fjord, rather than up toward the mountains, as an easterly operation would require.

It all worked out just fine, and a visitor at the airport put my arrival and departure on Youtube, I was later told I was the first "airplane" to use the runway, as it was normally for ultralights. The aircraft owner, who had asked me to fly his plane in there, was considering buying the aerodrome, and lengthen the runway. All things considered, I advised against this.

As I mentioned in an earlier post, I have used backside of the power curve technique many times in different circumstances, on wheels, floats and skis. In each case, I considered what I was doing, the increased risk, and the need to do this. It is possible, but as many things in aviation, do you need to do it?

[pelmet]

Personally, I think both sides of the debate have a point but it is just the way it is being worded that is causing the difference of opinion. I understand what our Aeronca test pilot is trying to say and I also understand what out test pilot school graduate is stating from his interpretation of the wording what the non-graduate test pilot said.

So what does it all mean for the new pilot out there. Different people can have different interpretations of what is basically the same thing and can end up arguing over nuances when they are actually in agreement without realizing it. At least, that's my interpretation. Exact wording can be extremely important and one can see it on occasion as something is written as a policy and some people may interpret things differently. Clarity is important.

What kind of aircraft are you doing test flying on Mr. Aeronca?

[Sockpuppet]

In Fort Frances, I once debated with a fellow pilot concerning the backside of the power curve, In that , as you increase power, you reduce your speed and land at a slower groundspeed ! He could not believe it !!! Well lets open this discussion to newbies and seasoned bush pilots who know better about these beyond training school tools in the industry .

Are you sure?
I would have thought it would reduce the airspeed, I'm not sure of the physics involved that would allow it to slow the ground speed, how does that work?

[aeroncasuperchief]

If one is landing on a short snow covered ( 2 inches or less) strip, it would be wise to touchdown at the lowest SAFE speed ( that would entail a backside approach in order to be stable) this same strip is lots long enough for a take-off but too short in these conditions for a normal approach speed and landing. The V-1 cut and stop distance is not available in these conditions WHY do it at all? Because you must land due to an emergency OR because you want to for shits and giggles or practice?

[aeroncasuperchief]

It all worked out just fine, and a visitor at the airport put my arrival and departure on Youtube, I was later told I was the first "airplane" to use the runway, as it was normally for ultralights. The aircraft owner, who had asked me to fly his plane in there, was considering buying the aerodrome, and lengthen the runway. All things considered, I advised against this.

As I mentioned in an earlier post, I have used backside of the power curve technique many times in different circumstances, on wheels, floats and skis. In each case, I considered what I was doing, the increased risk, and the need to do this. It is possible, but as many things in aviation, do you need to do it?

And so WHY did you do it ? Because you could and you did it safely. You did your homework. You did a risk assessment. Bravo

A mature and capable pilot is not risk adverse but rather an analysist and risk assessor !

[aeroncasuperchief]

There are MANY more instances where a capable pilot will use backside approaches to REDUCE risk !