fundamental guidance on Captain Jake landing

This is the place where we can all meet and speak about whatever is on the mind.
pjc747
Senior Master Sergeant
Posts: 2220
Joined: 04 Jan 2011

Re: fundamental guidance on Captain Jake landing

Post pjc747 »

bobsk8 wrote:
14 Sep 2019, 09:46
My suggestion to you is get a copy of Stick and Rudder and study it.
Seems like a serious argument!
Oracle427 wrote:
14 Sep 2019, 09:49
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.
Groundspeed is a direct indication of the energy held. Indicated airspeed remains constant despite altitude, so if I need more momentum to achieve the same indicated airspeed, then I have more energy. If I am landing in a 40 knot headwind, and I come to a stop in 50 feet, then I necessarily have less energy as it relates to landing. Should I approach at the appropriate airspeed, with a 15 knot tailwind, I would be almost certainly unable to stop on a 2500-foot runway. Why? Because I have far more energy. I am not saying you fly the airplane by groundspeed, but it is the factor which tells us how much energy we have, and therefore how much distance it would take us to stop, or whether we will carry so much energy that we skip or bounce when the wheels make contact and we didn't touch down with the perfect angle.
Oracle427 wrote:
14 Sep 2019, 13:22
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.
What you are describing is sink rate. Speed over ground is the only way we know how much energy, momentum, we carry. If you never consider this at the point of landing, i.e. touchdown, then you are saying that at the same field with zero wind compared to an appreciable one, there is no difference in energy as you meet the surface at the same airspeed? How make no considerations as to wind at all?

User avatar
Oracle427
Chief Master Sergeant
Posts: 3844
Joined: 02 Sep 2013

Re: fundamental guidance on Captain Jake landing

Post Oracle427 »

pjc747 wrote:
14 Sep 2019, 22:01
Groundspeed is a direct indication of the energy held. Indicated airspeed remains constant despite altitude, so if I need more momentum to achieve the same indicated airspeed, then I have more energy. If I am landing in a 40 knot headwind, and I come to a stop in 50 feet, then I necessarily have less energy as it relates to landing. Should I approach at the appropriate airspeed, with a 15 knot tailwind, I would be almost certainly unable to stop on a 2500-foot runway. Why? Because I have far more energy. I am not saying you fly the airplane by groundspeed, but it is the factor which tells us how much energy we have, and therefore how much distance it would take us to stop, or whether we will carry so much energy that we skip or bounce when the wheels make contact and we didn't touch down with the perfect angle.
Yes, groundspeed is a direct indication of the kinetic energy relative to the ground. It has no bearing on the energy state of the aircraft relative to its ability to maintain flight. The latter is the common understanding of energy state. Yes, we land into headwinds whenever possible to avoid having too much speed and energy relative to the ground. However, I can't understand how a pilot would change their approach speed based on ground speed. It doesn't make sense to do so. It may make sense to carry a gust factor if winds are variable, but the fact is that you must accept the groundspeed you get in the direction of landing at the appropriate airspeed for your configuration and type of landing. There is no performance data, training materials or anything I have ever seen that suggests that a pilot would change airspeed based on their perceived speed over the ground while on the approach. Everything I have read is 100% to the contrary.

If you are actually saying that the pilot should maintain the correct airspeed and not deviate from the correct airspeed on their approach regardless of what groundspeed they are making then I have no issue with what is being said here. The performance data tables for most aircraft will tell you exactly how much runway you need to land at various density altitudes, weights and configurations as well as wind components. The groundspeed is accounted for in these tables, the pilot only has to fly their approach at the proper airspeed and everything else is accounted for.
pjc747 wrote:
14 Sep 2019, 22:01
I am not saying you fly the airplane by groundspeed, but it is the factor which tells us how much energy we have, and therefore how much distance it would take us to stop, or whether we will carry so much energy that we skip or bounce when the wheels make contact and we didn't touch down with the perfect angle.
This is completely false. If the aircraft flies an approach at the proper airspeed (not any faster or slower) it doesn't matter what the winds are doing or what the groundspeed is. When the aircraft airspeed decreases below it's landing configuration 1G stall speed in a normal landing configuration. The aircraft *WILL* stall and it will not be able to bounce, skip or anything assuming the pilot maintains directional control and landed from at a normal height. The aircraft is simply is unable to generate sufficient lift to fly once it is stalled. If the pilot comes in with excess airspeed and touches down before bleeding off that airspeed, I can guarantee that they will bounce and skip or whatever else, because the aircraft has excess airspeed to lose before stalling. The groundspeed has no effect whatsoever on this, the wings do not know what the groundspeed is and the energy state of the wings is not affected at all by the energy state of the tires rolling over the pavement.

Should that pilot making the short field landing in Esa's video have accelerated to maintain the proper groundspeed? By your definition they had waaaay too little energy because they were basically nearly stationary over the ground. Do you believe that the pilot was flying that aircraft faster than normal in that situation to increase their energy state? I can assure you they were not. The converse is also true, a pilot will not fly an approach any slower just because they perceive they are coming in too quickly. The pilot *must* consider why they are coming in quickly and maintain appropriate situational awareness to understand if they may have to go around because of an unexpected tail wind component, etc. It would be incorrect and frankly could be very dangerous to slow down if the correct airspeed was already being maintained.

Suppose an aircraft is at idle and sitting on a treadmill. The treadmill starts to run and gradually accelerates to 50 knots in the direction opposite the airplanes direction of travel. The airplane pilot applies full throttle at the same time as the treadmill starts to accelerate to 50 knots. What is going to happen to the aircraft?
Flight Simmer since 1983. PP ASEL IR Tailwheel

User avatar
Oracle427
Chief Master Sergeant
Posts: 3844
Joined: 02 Sep 2013

Re: fundamental guidance on Captain Jake landing

Post Oracle427 »

AKar wrote:
14 Sep 2019, 12:38
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
I disagree that the pilot's groundspeed will dictate when and not where. A well trained and proficient pilot can rather precisely manage their touchdown point no matter the groundspeed. The pilot cannot however directly control the rollout distance after touchdown, as that is a factor of groundspeed. They must change direction of landing and/or wait for a windier day and/or go to a longer runway surface so they can make the landing in the available space. The pilot can still have 100% control over exactly where they touch down, provided they fly the aircraft at the right energy state in terms of airspeed and more directly the AoA. The pilot will stall the aircraft right where they need it to stall. A good/great instructor will drill this skill into their students and teach them that they have a huge degree of control over where you touchdown.

Yes, I fully agree that once the wheels are rolling on the ground and *only* once the wheels are rolling on the ground that the problem of touching down at the correct point and speed ends and the new problems begin of maintaining directional control as well as coming to a stop in the available distance. Those problems must be planned for *prior* to touchdown, and preferably prior to departure.

I think that pilots get sloppy with this stuff because they get used to flying out of big airports with runways that are 2-3 mistakes long and get complacent about airspeed management so they come in with lots of extra airspeed because they convince themselves that "it is safer". Some of these pilots end up avoiding "small airports" because of the sloppy technique. Sadly, I've witnessed some crashes in RL due to this, so it strikes a nerve with me. I know this is a flight sim forum, but some of us are also pilots and a few do go on to become pilots, so I do this only to try and educate.
Flight Simmer since 1983. PP ASEL IR Tailwheel

pjc747
Senior Master Sergeant
Posts: 2220
Joined: 04 Jan 2011

Re: fundamental guidance on Captain Jake landing

Post pjc747 »

Oracle427 wrote:
14 Sep 2019, 22:48
This is completely false. If the aircraft flies an approach at the proper airspeed (not any faster or slower) it doesn't matter what the winds are doing or what the groundspeed is. When the aircraft airspeed decreases below it's landing configuration 1G stall speed in a normal landing configuration. The aircraft *WILL* stall and it will not be able to bounce, skip or anything assuming the pilot maintains directional control and landed from at a normal height. The aircraft is simply is unable to generate sufficient lift to fly once it is stalled. If the pilot comes in with excess airspeed and touches down before bleeding off that airspeed, I can guarantee that they will bounce and skip or whatever else, because the aircraft has excess airspeed to lose before stalling. The groundspeed has no effect whatsoever on this, the wings do not know what the groundspeed is and the energy state of the wings is not affected at all by the energy state of the tires rolling over the pavement.
You do not understand what I am saying. If you are coming in to land, and your groundspeed and airspeed are equal, because wind is zero, it will take you longer to land, and longer to come to a stop, than it would if you had wind. Making an emphasis on airspeed implies to the reader that we should fixate on that, we should not. I do not know what airspeed a given airplane will land at, because I have no way to measure that. The airspeed indicator doesn't tell me that, and there is no specified airspeed at which an airplane lands. But when you land a plane, and care about where to put it, the energy you come in with, and ability to dissipate that energy, depends on your speed across the ground. Depending on that, we must modify how we approach the runway to accomplish a desired result. With the same base/final approach speed, the way my approach will be tailored, and the way the airplane comes to the surface, can be easily gauged by how fast I am going in relation to the cars on the freeway I see out my window. I don't care about the technical jargon you send at me at how the airplane stalls no matter what, that doesn't matter. I don't need to look at the airspeed indicator, or any instrument to successfully approach and land a G.A. single. But looking at how fast across the ground I am approach it dictates exactly how I will configure the airplane to get it onto the ground.

User avatar
AKar
A2A Mechanic
Posts: 4560
Joined: 26 May 2013

Re: fundamental guidance on Captain Jake landing

Post AKar »

Oracle427 wrote:
14 Sep 2019, 22:54
I disagree that the pilot's groundspeed will dictate when and not where. A well trained and proficient pilot can rather precisely manage their touchdown point no matter the groundspeed.
Returning to the original condition, engine at idle (gliding flight)...if you chop the throttle on speed (proper approach air speed), and at some given altitude, what remains constant regardless of the steady wind (and hence ground speed) is the time you have remaining before you smack the wheels down, assuming similar control technique. What in turn depends on the wind, of course, is the remaining ground distance covered during that flare maneuver. I think this is rather not debatable point, right? Of course, if you want to target a precise touchdown point, you need to take this into account in timing of your flare and cutting the power. So, you end up taking the wind speed (and hence again, the ground speed) into account. Right?
Oracle427 wrote:
14 Sep 2019, 22:48
If you are actually saying that the pilot should maintain the correct airspeed and not deviate from the correct airspeed on their approach regardless of what groundspeed they are making then I have no issue with what is being said here.
Are you saying that adding the wind corrections to the approach reference speeds they have been doing for decades is complete rubbish? They should stop doing that? Probably thousands of approaches and landings every day add half of the steady head wind component plus the full gust increment, cumulatively +5 knots minimum and +20 knots maximum, to the reference approach speed, which in turn is directly based on stall speed. Other similar "formulae" exist. You do know the reasoning behind wind corrections to final approach speeds, right? Only thing I'm stating perhaps unconventionally here is using word ground speed instead of wind speed.
Oracle427 wrote:
14 Sep 2019, 22:48
If the aircraft flies an approach at the proper airspeed (not any faster or slower) it doesn't matter what the winds are doing or what the groundspeed is. When the aircraft airspeed decreases below it's landing configuration 1G stall speed in a normal landing configuration. The aircraft *WILL* stall and it will not be able to bounce, skip or anything assuming the pilot maintains directional control and landed from at a normal height. The aircraft is simply is unable to generate sufficient lift to fly once it is stalled. If the pilot comes in with excess airspeed and touches down before bleeding off that airspeed, I can guarantee that they will bounce and skip or whatever else, because the aircraft has excess airspeed to lose before stalling.
What about aircraft that are not stall-landed? Such as some twins, many (most?) gliders, fast stuff, et cetera?

By saying it doesn't matter what the winds are doing, do you say that if you lose ten knots of headwind you don't lose ten knots of (true) airspeed unless you make that back up again, either by increasing engine power (if installed), or by sinking slightly on the approach? I guess that's not what you're saying, no. Would it not be more efficient to anticipate, if able, this loss, and carry those extra knots indicated with you to shed them off when penetrating the wind gradient?

If I'm flying very slow aircraft, with nominal approach speed of say 85 km/h, don't you think that a prompt loss of 10 knots, which is 22 % of my approach speed, at around treetops height would put me uncomfortably close to running out of luck for the day? Would it not be a good idea to make the approach speed like 95 km/h when I anticipate such conditions? Note, this is not to be kept as a threshold speed, so when you lose your extra knots to the wind gradient, you don't want to regain them anymore!



I'm talking about very conventional thinking here, after all. Nowhere have I said, not would I ever say, that ground speed as a number should be anyone's primary flying reference for much anything except navigation and hovering a helicopter, hopefully for obvious reasons. What I'm simply saying is that its importance as a reference to airplane's inertial speed is often forgotten or not understood, and that it can and does provide the only cue available to the actual wind component at the airplane's current position.



Edit: I do appreciate you put strong emphasis on avoiding overruns on short runways. For my kind of real physical world flying I used to do, that was basically not a factor. Instead, landing short really was, and my home airfield sometimes was notorious for its difficult wind conditions. So, different people come from different backgrounds, have different educations and experiences - and hence different points-of-view, priorities and opinions! :)

-Esa

plicpriest1
Airman
Posts: 38
Joined: 23 Jan 2017

Re: fundamental guidance on Captain Jake landing

Post plicpriest1 »

Such a great discussion! Now thats aviation :)

My own 2 cents. I am a former CFI II MEI (it lapsed, ya I know I know) and currently a 767 FO (just bragging a little). So I will give you all my own thoughts and advice.

First: treat every landing as its own and unique landing. What that means is this, adjust all the variables to meet the demands of the situation. Windshear on final- carry a few extra knots. General rule of thumb for big planes is add half the headwind and all of the gust up to 20 knots. That is of course silly in a 172, but adding 3-5 isnt a bad idea. Oh yes and if there is ice pellets or breaking action is less that a 5-5-5 (look up RCAM), do NOT attempt to grease the landing. Just put it down on the center line in the touchdown zone on speed (not slow not fast).

Second: fly the approach by the numbers. That is either what is in the POH or the old 1.3xVso. Again however there are times you need to adjust. Do so but do it deliberately, not "oh gee im fast, I meant to do that lol".

Third: dont stop flying the aircraft until you are at the hanger. Just because you managed to get the wheels on the pavement, doesnt mean you are done. Especially in a crosswind. Keep your crosswind correction IN!!! Dont take it out until you are crawling, even then you do remember your control positions on taxiing in a crosswind dont you? Also just because you are down doesnt mean your done. Nothing worse than greasing that landing only to eff a taxi clearance and get a phone number.

Fourth: always always always strive for perfection. If you did okay today do better tomorrow. Enjoy yourself but always hold yourself to high standards. Even if you are not a professional (paid to fly), you ARE a professional pilot. The day you are able to fly by yourself you are a professional!!! Fly the part, look the part, and if you have no clue whats going on- act the part.

Best wishes
Brian

User avatar
DHenriquesA2A
A2A Chief Pilot
Posts: 5169
Joined: 27 Mar 2009
Location: East Coast United States

Re: fundamental guidance on Captain Jake landing

Post DHenriquesA2A »

plicpriest1 wrote:
15 Sep 2019, 21:27
Such a great discussion! Now thats aviation :)

My own 2 cents. I am a former CFI II MEI (it lapsed, ya I know I know) and currently a 767 FO (just bragging a little). So I will give you all my own thoughts and advice.

First: treat every landing as its own and unique landing. What that means is this, adjust all the variables to meet the demands of the situation. Windshear on final- carry a few extra knots. General rule of thumb for big planes is add half the headwind and all of the gust up to 20 knots. That is of course silly in a 172, but adding 3-5 isnt a bad idea. Oh yes and if there is ice pellets or breaking action is less that a 5-5-5 (look up RCAM), do NOT attempt to grease the landing. Just put it down on the center line in the touchdown zone on speed (not slow not fast).

Second: fly the approach by the numbers. That is either what is in the POH or the old 1.3xVso. Again however there are times you need to adjust. Do so but do it deliberately, not "oh gee im fast, I meant to do that lol".

Third: dont stop flying the aircraft until you are at the hanger. Just because you managed to get the wheels on the pavement, doesnt mean you are done. Especially in a crosswind. Keep your crosswind correction IN!!! Dont take it out until you are crawling, even then you do remember your control positions on taxiing in a crosswind dont you? Also just because you are down doesnt mean your done. Nothing worse than greasing that landing only to eff a taxi clearance and get a phone number.

Fourth: always always always strive for perfection. If you did okay today do better tomorrow. Enjoy yourself but always hold yourself to high standards. Even if you are not a professional (paid to fly), you ARE a professional pilot. The day you are able to fly by yourself you are a professional!!! Fly the part, look the part, and if you have no clue whats going on- act the part.

Best wishes
Brian
Excellent post Brian. I've been following this thread with some degree of interest and have hesitated to get in. I've been waiting for someone to break it all down to the KISS principle where it belongs. Now I don't have to type it out myself. LOL
Dudley Henriques

User avatar
MaxZ
Senior Airman
Posts: 143
Joined: 27 Sep 2013
Location: LOWL

Re: fundamental guidance on Captain Jake landing

Post MaxZ »

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.

Hi! Sorry for the late reply...my work-life balance is clearly tilted towards work at this time. And sorry for reading not all pages of this thread yet.Yes, indeed your brakes need to convert a lot more energy with a high ground speed and it puts a lot more stress on the whole plane. But from what I understand this is not the key point in energy management. In this case total energy is a product of two factors: kinetic energy, namely for the sake of explanation airspeed and potential energy, namely altitude. Think of it that way: You only take into account your aircraft's energy, not the energy of the wind.

Greetings,
Max

plicpriest1
Airman
Posts: 38
Joined: 23 Jan 2017

Re: fundamental guidance on Captain Jake landing

Post plicpriest1 »

Max,
I think your onto a good track. There are a few more items to keep in mind.
First, Yes you do need to think of things in terms of Kinetic and Potential energy. As pilots we need to manage this. One of the ways in which we manage energy is through the drag of the aircraft and drag devices on the aircraft. High on the approach? Lower the gear early (or introduce more flaps). Still not enough? Maybe a little slip. Still not enough? GO AROUND! Note some aircraft prohibit the use of slips (structural concerns). Too low? Add power or go around.

Now to the main argument of GS vs Airspeed. When flying, fly airspeed. If you fly the correct airspeed, then unless you have a very contaminated runway or a strong tailwind, you will have sufficient runway to land and get stopped. "but how do we know we have enough runway"? Great question, by running the data from the POH performance section! Pro-tip: do a preliminary landing distance calculation of your destination and alternate before you leave. Just do a general no wind no contamination landing distance. Once you get arrival ATIS (AWOS ASOS) you may refine your calculations.

Personally I like to do a worst case landing analysis. Max tailwind, max weight, downhill, high density altitude, etc. If with all those evil factors against me, I still have enough runway than absolutely no concerns on landing (except putting the gear down lol).

Moral of the story: fly proper airspeed, on glide path. Don't stress the ground speed except to not let the winds push your downwind too far. Have the landing distances known ahead of time (and add a fudge factor). If the landing is in doubt, go around.

new reply

Return to “Pilot's Lounge”

Who is online

Users browsing this forum: No registered users and 12 guests