Debunking the myth Power vs Pitch - GoFly Fix
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- Опубліковано 26 гру 2019
- In this video Damien and Paul demonstrate which is better: power or attitude for airspeed on final approach.
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I’ve driven everything from ultralights to Airbus, I use the steering wheel to keep the picture I want in the window and the gas pedal to keep the speedo where I want, 42 years, worked for me!
In that Airbus, how often is the glidepath coupled hence “Hal” trimming? Alternately, in that Airbus, what is the spoolup time for the engines? Pitch for glidepath with power/throttle for speed is a front side technique. If in a backside flyer, pitching down if high will cause you to float long. We trim for AOA though use speed as a crutch if we have no AOA display. Once trimmed, that AOA will stay constant if we don’t have bumps or “stick-bumps.” Hence power will control glideslope. This is a Power Technique and works both sides of the curve. To prove it to you, consider flying at cruise obviously front side, what happens if you add power? You go up. As the power technique works everywhere, we use it on the backside as we don’t like true backside techniques. You could use the power technique on the front side but often rather than just considering 1.3 Vso, procedures are designed to be the higher of 1.3 Vso or front side so as to compensate for aircraft that have long spool-up times on the engines. Pitch for glidepath is a relatively quick response. For many turbines, power for glide, especially if not at a higher up neutral power point, takes too long to propagate. Hence why I bet you’re happy in that Airbus. Further, often in professional aircraft, you’re coupled up so the aircraft is constantly trimming and the aircraft owns glidepath so you have no choice but to use power for speed. That reverses upon uncoupling should you have insufficient energy to be front side.
As for those backside techniques no one likes, yes, you’d use pitch for path but not in a comfortable way. If high, you’d need to pull up to slow down increasing drag so as to fall toward desired glidepath then dump the nose to capture speed to maintain desired glidepath. Alternately, if low, you’d need to push the nose to reduce drag to float long. As I say, uncomfortable while many newer pilots never learn these just as they never learn the distinction between zoom and dive versus climb and descent.
It’s very simplified to say pitch for speed and power for rate of descent, but they are completely intertwined. This is true for all maneuvers. This is why you add power in steep turns to arrest any descent while holding pitch and maintaining airspeed. Understanding how the two interact with each other makes you a better pilot in all phases of flight.
You add power in steep turns to stay level assuming you want to maintain constant airspeed. You can leave the power where it is and add trim settling to a slower speed. Such is actually one of the test techniques for determining energy loss rates and creating the EM diagram. You fly full power to find a top speed then turn bleeding to a new speed then increase turn bleeding to a new speed… As you’re already at full power, you can’t add power.
@@jimallen8186 The speed bleeds because vertical lift is reduced in the bank and requires more AOA to maintain altitude.
@@AnonyMous-jf4lc The speed bleeds because of the extra induced drag from that increased AOA. That’s different. Drag causes the deceleration not the AOA. You can either add trim as we really trim for AOA not speed to hold this increased AOA and accept the slower speed meaning you trimmed aka pitched for AOA and pitched for speed, or, add power to counter this increased drag. If you do add power, you will see speed increase but this a second order effect and is not power for speed as you added to power to maintain altitude and you’ll be maintaining a constant AOA to which you previously trimmed. Now, if we flush speed from the discussion and use AOA as we should be, these nitnoid pieces fall out. Pitch for AOA Power for GlidePath. We’ll still use “fast” and “slow” for referencing AOA so as not to confuse “high” and “low” from glidepath. But as we need to appease the FAA still stuck on speed not AOA as not all aircraft display AOA, we need to keep these confusions with speed hence confusions in the video and comments.
@@jimallen8186 obviously I understand that concept, and figured you did as well, so didn’t elaborate.
Think as if driving a vehicle through the hills and wanting to keep a constant speed, when you go up hill you got to add power to maintain the speed, when you go downhill vice versa. An airplane is exactly the same except you can make your own Hills.
Not really, in an airplane there are forces acting that don't exist in a car, there are different concepts. Use within this reasoning, for example, the lift formula and relate it to the rate of descent along with the vectors of forces that act on the aircraft in different situations and compare.
Fantastic comparison. Very well presented.
Excellent video, great job. 👏
Another fantastic video!
Very good. I’m wondering what Jacobson (of Jacobson flare fame) would say. He doesn’t seem to make a distinction between aircraft types
In approach, autoflight of b737 use power for speed and pitch for path.
Great video. Logically there might be a transition plane that works either way?
I fly the exact opposite: in a single piston (not a sling) power for speed. Hold pitch steady as can be and don't let the torque steer the nose. In a heavy (not a 737), pitch for speed. The heavy has a HUD so it won't porpoise into a 2000fpm climb unless you're bad. If you're good, the pitch is steady from IM to flare.
@8:08 I'm glad you got it stopped with a little runway left to spare, but can you tell me what your brake temps where? I think you melted them. :) Never mind the pax aren't too happy with going from 1000 fpm climb to 2000 fpm decent. What if the runway was wet. Icy. Or light snow. Would have ended like that flight into Reagan Intl many years ago that ended up in the Potomac, with pax struggling in the freezing water with jet fuel in their eyes/mouth/nose etc. Hard enough not to drown in ice cold water, never mind with jet fuel on top.
He's just bad at controlling power when on final. I fly piper tomohawks and we were taught to aim and adjust power barley. If you are taught correctly it's not sloppy and it's much nicer than pitch for airspeed flying
Totally agree - the magnitudd of his power changes is wild given the conditions. A long video but no real conclusive info or theory. I was taught by Alex IAF test pilot and went through all the theory behind why approaches are more stable using power to manage speed.
Well there is no good method. It depends on the type of aircraft and type of approach you fly. Bush pilots, on single piston engine, clearing high obstacles, will go high angle descent slop, airspeed barely above stall, keeping the the airspeed with pitch and power is kept constant at 1500/1600 RPM until starting to round out and flare.
Normal approaches on single engine: I clearly go pitch for airspeed and power for VS, way safer. Why? Because pulling the yoke to adjust VS close to stall speed could be catastrophic a low altitude.
In a jet or even heavier piston planes, power controls speed and yoke controls VS. So there is no good answer, it is only dependent on what plane is flown and in which circumstances...just my opinion.
This video makes 0 sense to me. You just showed two different situations, but never really went into why.
They touched on it a bit. The high mass of the 737 gave it much more inertia so it was very unstable to control the approach with pitch for airspeed and power for attitude because of such a high delay in effect.
The light aircraft did not suffer from this issue because its inertia is much lower and responded quite quickly. The argument for light aircraft is to pitch for airspeed because using the pitch for attitude will cause more induced drag at lower speed and lead to a higher descent rate… but this is also true with pitching for airspeed.
In my opinion, they’re very closely related and you should just use what works for you. They both control your energy management so you’ll end up changing one after you change the other. Overthinking it can cause you to focus less on more important things.
Does power or pitch control airspeed.
Answer: Yes
So, ummm... What's the myth you're debunking? Isn't it common knowledge that you fly small aircraft differently from large aircraft, who thinks otherwise? Good demonstration though.
You can fly both with Power techniques meaning power for glidepath pitch trim for speed. Only reason you’d differ is if you wanted to maintain extra energy for gliding scenarios. Note: Gliders also use the “Power techniques” as they use spoilers that both reduce lift and increase drag thus altering the loss rate of energy. The spoiler lever is mechanized in the same manner as throttle / power lever with back increasing the energy deficit, forward decreasing the energy deficit. You may not have spoilers on small planes but you do still have slips. Power technique is by far the easier and works both sides of the drag curve. Front side techniques work for turbine aircraft that have long engine spoolup times. Note Navy jets add excess drag so as to shift the neutral power point up such that their engines are already spun up so they can use power techniques. Front side techniques also work with coupled autopilots as the plane is constantly trimming to maintain glidepath. The myth is that power techniques are strictly for backside flyers; power techniques work everywhere assuming a constant trim so long as you don’t need to worry about delayed spoolup times. True backside techniques are rarely taught and rely on the distinctions between zoom and dive versus climb and descent. For the backside technique, if high, pull up increasing drag to fall faster then dump the nose to catch desired speed at desired glidepath. If low, push down to reduce drag so as to be able to float further.