fundamental guidance on Captain Jake landing

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rod321
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Re: fundamental guidance on Captain Jake landing

Post rod321 »

Hi Paughco

many thanks for your generosity in sharing the links to SIM CFI's videos; particularly the first 2. So 'round-out' is a new term for me.

Still learning; thanks to you.

Seeya

Rod
EGBB (another blue sky; I'll have to chuck some water at the garden)

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bobsk8
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Re: fundamental guidance on Captain Jake landing

Post bobsk8 »

rod321 wrote:
14 Sep 2019, 07:26
Hi Paughco

many thanks for your generosity in sharing the links to SIM CFI's videos; particularly the first 2. So 'round-out' is a new term for me.

Still learning; thanks to you.

Seeya

Rod
EGBB (another blue sky; I'll have to chuck some water at the garden)

Back to Saturday's soccer! Can Leicester beat Man United?
All of Sim CFII's videos are wonderful. He covers many A2A aircraft.
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pjc747
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Re: fundamental guidance on Captain Jake landing

Post pjc747 »

MaxZ wrote:
13 Sep 2019, 08:32
pjc747 wrote:
26 Aug 2019, 23:38
...The only speed you care about over the runway before actually landing the airplane is your ground speed...

Hi everyone! I have to strongly disagree to your opinion.
Groundspeed is the reason we pick different landing directions but it does in no way reflect how high or low you are on energy. Airspeed or better yet as you mentioned alpha should be your focus. Paired with a headwind component you'll have less GS than TAS.

Greetings,
Max
Please educate me on this. Approaching the runway on short final is not actually landing the airplane. The stumbling block that people encounter when learning to fly is not flying around the pattern (that is a fairly easily learned project), it is putting the airplane on the ground and making it not fly. At that point, airspeed does not matter anymore, because we are directly over the runway, and at an altitude of less than 20 feet. Our groundspeed IS a direct measure of our energy as we try to actually do the bit where we make it not fly anymore (land). If you put down a Cessna 172 in 25 knots of wind, ground groundspeed will likely be around 25-30 knots at the moment of touchdown. Your ground roll in the case will be very short; if you were to land a Cub in 40 knots of wind, you could land on a helipad, no problem. Landing with a tailwind means you have an abundance of energy, far more than you would on a calm wind day, and even with the appropriate airspeed for normal flight, stopping on the runway would be impossible. Airspeed is no reflection of the momentum we carry in the pattern.

With high density altitude, is our airspeed greater or less at liftoff? Is our groundspeed greater or less? On the edge of space, we could carry great momentum, 1000 knots ground speed, but have zero airspeed (indicated) because there is no air. The art of landing the airplane is understanding this fact. Staring at the airspeed indicator will do us no favors as we attempt to safely and effectively put the wheels on the ground, and make a flying machine cease to fly. On approach? Sure! An airspeed indicator can be our friend, but understanding how our machine flies at slow airspeeds is essential, and at that point we can worry about landing.

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bobsk8
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Re: fundamental guidance on Captain Jake landing

Post bobsk8 »

pjc747 wrote:
14 Sep 2019, 09:37
MaxZ wrote:
13 Sep 2019, 08:32
pjc747 wrote:
26 Aug 2019, 23:38
...The only speed you care about over the runway before actually landing the airplane is your ground speed...

Hi everyone! I have to strongly disagree to your opinion.
Groundspeed is the reason we pick different landing directions but it does in no way reflect how high or low you are on energy. Airspeed or better yet as you mentioned alpha should be your focus. Paired with a headwind component you'll have less GS than TAS.

Greetings,
Max
Please educate me on this. Approaching the runway on short final is not actually landing the airplane. The stumbling block that people encounter when learning to fly is not flying around the pattern (that is a fairly easily learned project), it is putting the airplane on the ground and making it not fly. At that point, airspeed does not matter anymore, because we are directly over the runway, and at an altitude of less than 20 feet. Our groundspeed IS a direct measure of our energy as we try to actually do the bit where we make it not fly anymore (land). If you put down a Cessna 172 in 25 knots of wind, ground groundspeed will likely be around 25-30 knots at the moment of touchdown. Your ground roll in the case will be very short; if you were to land a Cub in 40 knots of wind, you could land on a helipad, no problem. Landing with a tailwind means you have an abundance of energy, far more than you would on a calm wind day, and even with the appropriate airspeed for normal flight, stopping on the runway would be impossible. Airspeed is no reflection of the momentum we carry in the pattern.

With high density altitude, is our airspeed greater or less at liftoff? Is our groundspeed greater or less? On the edge of space, we could carry great momentum, 1000 knots ground speed, but have zero airspeed (indicated) because there is no air. The art of landing the airplane is understanding this fact. Staring at the airspeed indicator will do us no favors as we attempt to safely and effectively put the wheels on the ground, and make a flying machine cease to fly. On approach? Sure! An airspeed indicator can be our friend, but understanding how our machine flies at slow airspeeds is essential, and at that point we can worry about landing.
My suggestion to you is get a copy of Stick and Rudder and study it.
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Oracle427
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Re: fundamental guidance on Captain Jake landing

Post Oracle427 »

Again the groundspeed will be significantly higher on hot and humid days and especially so at higher altitudes. If you use groundspeed as your measure of energy, then you will be in for a nasty shock.

The fact is that the plane will land at a much higher groundspeed in the above conditions. It will stall and touch down at a relatively high speed. The airspeed on the other hand will be exactly the same if the approach is flown correctly. There are numerous accident reports that are attributed to pilots not accounting for these significant changes in performance under varying atmospheric conditions. The pilot must expect the runway to be zooming by much faster in this situation and performance becomes more critical on an otherwise "long" runway.

When over the runway on short final, no one really should be managing airspeed or groundspeed anymore. The pilots job is to maintain alignment with the runway and keep the airplane flying until it is ready to touch down. At that point in time both the airspeed and groundspeed is what it is.

Take for example landing at a 2000 foot long runway at sea level on a winter day. It will be very easy to approach at 65 knots and touch down at the beginning of the runway and come to a stop midway in a 182, even with the exception speed on approach. Now try doing the same in the summer with a density altitude of 3000 feet. The approach will be relatively shallow, noticably faster, and if at 65 knots you will struggle to come to stop by the middle of the runway without looking brakes even if you touch down at the very down at the beginning of the runway. The ground speed is just that much faster. If the pilot slows down to try and approach at the "normal" speed they expect in winter, then they will be very slow and not have enough energy for the flare. If the reverse is done with the pilot speeding up to fly with a "summer" grounspeed the pilot might find themselves completely overrunning the tunway in the winter with a lot of excess airspeed and energy to bleed off.
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AKar
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Re: fundamental guidance on Captain Jake landing

Post AKar »

Airspeed, as in IAS/CAS should not be called "speed" at all, because it isn't. It is inherently a measure of pressure, and proper unit for it is pascal, bar or some other. Though I recon few issues if we changed our instrument faces to read in pressure units. :mrgreen: (Spacecrafts often actually do that.)

Importance of ground speed, navigational issues aside, comes from the fact it relates to airplane's "true" inertial speed (not quite accurately, though, due to rotation of the Earth, and if the descend/climb angle is steep). Therefore, when the wind is not steady along airplane's path, airplane's inertia attempts to keep constant ground speed. This is why near-VNE descends in strong tail wind are bad idea: when the tail wind inevitably slows down, sometimes rather sharply, the airplane wants to keep its inertial speed (≈groundspeed), and you will overspeed the airframe. This happens somewhat regularly to keep the investigating authorities busy.

The opposite occurs if maintaining too low approach speed when strong headwind component is evident (low ground speed at altitude). The wind within the surface gradient follows closely a kind of power law, the exponent of which ('α' in the picture below) depends mainly on the surface type. One can expect to lose some significant airspeed when the aircraft sinks through the final 100 meters of altitude or so. In gliders particularly this results in hazardous condition, because you end up very low in energy and lack altitude to recover. I've landed hard and/or bounced a few times myself before I learned to add some extra to the approach speed per headwind component.

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Picture source: Recoskie et al, A High-Fidelity Energy Efficient Path Planner for Unmanned Airships

-Esa

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MkIV Hvd
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Re: fundamental guidance on Captain Jake landing

Post MkIV Hvd »

bobsk8 wrote:
14 Sep 2019, 09:46
My suggestion to you is get a copy of Stick and Rudder and study it.
Popcorn anyone?? :lol:

This is a great discussion with a lot of good information. Groundspeed is clearly important in several scenarios other than enroute and descent planning, etc. However, the OP was about the landing phase of flight itself and we all should agree that the ultimate goal in pulling off a good landing is to be at or very close to stalling the airplane at the time that the wheels touch the ground, Transport Category A/C, jets, etc. excepted. This is done through reference to airspeed on approach and visual clues in the flare and has nothing to do with groundspeed, which is what it is. Energy related to flight, whether a 747 or Cub, has nothing to do with groundspeed until the wheels are upon said ground.
pjc747 wrote:
14 Sep 2019, 09:37
Staring at the airspeed indicator will do us no favors as we attempt to safely and effectively put the wheels on the ground, and make a flying machine cease to fly. On approach? Sure! An airspeed indicator can be our friend, but understanding how our machine flies at slow airspeeds is essential, and at that point we can worry about landing.
Staring at any single thing in an airplane is a sure way to get in trouble. Whether it’s staring at airspeed or out the window trying to figure out how fast you’re going across the ground, safe flight is always scanning. We absolutely need to learn and fully understand how our airplane flies at slow airspeeds and through the stall (our approach to…) in order to be able to successfully land any airplane…note that is all done with reference to airspeed.

Cheers,
Rob
Rob Wilkinson
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Paughco
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Re: fundamental guidance on Captain Jake landing

Post Paughco »

A long time ago, at an airport far away (KHAF, back in '64 or so) I was learning how to fly in a Cessna 150. Standard pattern altitude at that time was 750 feet above ground level. Here we are, in a 150, on a right downwind for Runway 30. No crosswind, no traffic. (Roll the introduction to "Dogfights" on the History Channel).

The airplane is trimmed for normal cruise speed, about 90 mph and is on the downwind leg, flying level, essentially hands off, as we look out the ride side at the runway. As we pass the runway numbers, power is pulled to idle and the nose drops a bit. Pull carb heat, hold the yoke so that we're in a glide at 75 mph, and trim for hands off. We're still on downwind, judging when to turn base, so that we'll ideally be able to cross the numbers on final with no additional use of power (other than an occasional clearing of the engine, once or twice during the approach). We turn right onto base, and we're descending nicely at 75 mph. We roll onto final, lining up on the runway, still at 75 mph, power off, gliding along, toward the numbers.

OK, here comes the tricky part: my instructor described the technique as gently pulling back on the yoke as the ground approaches, transitioning gently from a stable 75 mph glide to a near zero descent rate with airspeed gradually bleeding off. The last part of this is done with the main gear inches off the ground, the nose coming gradually higher, stall warning beeping, finally the mains gently kissing the ground. That was how he demonstrated it!

Now my turn. I never crashed us into the ground (carrier landing!), but I did have us ballooning upwards by pulling back on the yoke too quickly (I was a punk kid then; finesse was not in my vocabulary, with cars, girls, or airplanes). My approaches were great, but the transitions (round out) at the end were anything but.

One Saturday morning, I thought about it as I was waking up. That's when it came to me. The rounding out thing is to be done gently, subjectively, totally dependent upon variables as they are at the moment of landing. Like Dudley says, "Fingers and toes, not hands and feet."

That day I ACED it! I was ready for solo! Hey, if 18-yr old me could do, you can do it too!

Seeya
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AKar
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Re: fundamental guidance on Captain Jake landing

Post AKar »

Acknowledging fully that this may be somewhat off the original topic... :mrgreen:
MkIV Hvd wrote:
14 Sep 2019, 11:48
Energy related to flight, whether a 747 or Cub, has nothing to do with groundspeed until the wheels are upon said ground.
...with this, I beg to differ. The simplest elementary counter-example is descend planning. (And this even applies to steady winds.) You need to either increase your rate of descend (equivalent to rate of energy dissipation) in case of tailwind to keep a constant descend angle, or you need to keep the air distance constant by starting the descend earlier over the map. This is of course obvious, but there is also more subtle point: from the top-of-descend to the full stop after landing, you'll need to dissipate the extra kinetic energy you've got due to tail wind at the moment you start your descend before chocks are thrown. Whether the amount of joules is significant, depends of course of the airplane in question and of the wind profile (due to latter, you may need to carry those extra joules longer than you'd like to). But fundamentally, airplane's descend and landing is an energy management problem of fairly simple geometry: your ground speed needs to end up being zero, and your height needs to end up being zero as well.

-Esa

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Oracle427
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Re: fundamental guidance on Captain Jake landing

Post Oracle427 »

Can we at least agree that in a landing, in the final moments prior to touchdown work the engine at idle, that airspeed and AOA are going to dictate where the plane will touchdown? The groundspeed and wind are whatever they are. The plane doesn't feel those and will stall only based on airspeed and more directly the AOA.

One could say that all this talk of relative wind changes/gradients is merely affecting the airspeed anyway. You can have a grounspeed higher than your currently indicated 1G stalling airspeed. What is going to happen at that point in time? Conversely, to you could have an extremely low grounspeed, yet have plenty of airspeed.
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AKar
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Re: fundamental guidance on Captain Jake landing

Post AKar »

Oracle427 wrote:
14 Sep 2019, 12:26
Can we at least agree that in a landing, in the final moments prior to touchdown work the engine at idle, that airspeed and AOA are going to dictate where the plane will touchdown?
Well....not exactly where, but when, yes. :mrgreen: With ground speed similar to his airspeed, this guy would have landed way further:
https://www.youtube.com/watch?v=7vP13XPMNfc
Oracle427 wrote:
14 Sep 2019, 12:26
One could say that all this talk of relative wind changes is having an effect on airspeed anyway. You can have a grounspeed higher than your currently indicated 1G stalling airspeed. What is going to happen at that point in time?
I'm not sure I get the question right, but of course we can all agree that ground speed as a steady number has zero relevance to stalling.

-Esa

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MkIV Hvd
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Re: fundamental guidance on Captain Jake landing

Post MkIV Hvd »

Oracle427 wrote:
14 Sep 2019, 12:26
Can we at least agree that in a landing, in the final moments prior to touchdown work the engine at idle, that airspeed and AOA are going to dictate where the plane will touchdown?
Yes we can.
AKar wrote:
14 Sep 2019, 12:38
…but of course we can all agree that ground speed as a steady number has zero relevance to stalling.
YAY! So, proper landing = timely stall…timely stall in no way related to groundspeed…me back to not caring about groundspeed as it relates to the approach to the timely stall… ;)
Paughco wrote:
14 Sep 2019, 11:57
Like Dudley says, "Fingers and toes, not hands and feet."
Repeat to yourself as often as necessary to drive that home…it’s the only way!
Rob Wilkinson
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AKar
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Re: fundamental guidance on Captain Jake landing

Post AKar »

MkIV Hvd wrote:
14 Sep 2019, 13:08
AKar wrote:
14 Sep 2019, 12:38
…but of course we can all agree that ground speed as a steady number has zero relevance to stalling.
YAY! So, proper landing = timely stall…timely stall in no way related to groundspeed…me back to not caring about groundspeed as it relates to the approach to the timely stall… ;)
Well, of course, with airplanes that are landed in stall attitude. :)

-Esa

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Oracle427
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Re: fundamental guidance on Captain Jake landing

Post Oracle427 »

Since I do occasionally fly super cubs into very short fields of about 400 feet. I can say that my grounspeed is never really considered in the landing. On the other hand I'm am by carefully considering my approach speed and feeling my energy state with my butt.

As in a touch of throttle, seat gets heavier. Take out a touch of throttle, seat gets lighter. Repeat over and over and maintain pitch carefully to stay close to max AOA.

Some days it will be faster, some data it will be slower coming in. The winds are what they are, and of they aren't favorable, or the density altitude is too high, then it's a scrub.

I will make sure to land there only when the ground speed is going to be low enough to stop in the distance I have available.
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AKar
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Re: fundamental guidance on Captain Jake landing

Post AKar »

Oracle427 wrote:
14 Sep 2019, 13:22
I can say that my grounspeed is never really considered in the landing. On the other hand I'm am by carefully considering my approach speed and feeling my energy state with my butt.

As in a touch of throttle, seat gets heavier. Take out a touch of throttle, seat gets lighter. Repeat over and over and maintain pitch carefully to stay close to max AOA.
Yes, that's probably the essence of it, whenever you can do it that way. No argue whatsoever there. :)

-Esa

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