Dangerous teaching

[motzartmerv]

Saphire. How and why does one try to maintain their groundspeed in a turn? Please be careful in the student thread, be clear about what your saying. This is not the local bar. Thanx

 

 

[nomadpete]

Sapphire I thought you were referring to the "downwind turn stall" myth, I agree when doing a teardrop turn it should ideally be into any cross-wind there may be simply to minimise the turn radius.

At least you agree with my gliding training. thanks

 

 

[Camel]

A lot of info here . http://www.australianflying.com.au/news/dragons-of-the-downwind-turn

 

 

[nomadpete]

Glider Rope break - Turn back procedure:

 

Perhaps I didn't make it clear in my post describing a glider 180 turn back. The initial move is to veer downwind, then turn back into the wind, to minimise the turn radius, and allow the dropping airspeed to work with the crosswind component to drift you back to the centreline of the strip without allowing the airspeed to drop below 1.5 Vs. This makes the slight downwind turn happen when airspeed is highest. If you want to call it a teardrop turn, then the first part of it is really a downwind 'S' turn before making a 'U' turn into wind.

 

My other point remains - it is a very dangerous thing to try consider in a low mass, draggy aircraft such as our RAAus aircraft.

 

 

[Sapphire]

Saphire. How and why does one try to maintain their groundspeed in a turn? Please be careful in the student thread, be clear about what your saying. This is not the local bar. Thanx

MM, my example showed diferent relationships of ground speed and IAS. When flying with visual reference to airspeed, you look at your ASI to get IAS. Ground speed automatically adjusts itself depending on wind conditions and density height. The effect I described does theoretically happen but has little impact on day to day flying. If you are say just about to stall and turn into wind, that would inhibit the stall while turning downwind would tend to induce a stall. Further to Turboplanner's comment I fly a plane by ground speed. Of course yes, to navigate a plane I use ground speed, to keep it in the air I use IAS. There are several airspeeds-indicated air speed which is just dynamic pressure calibrated into airspeed numbers and does not exactly tell you how fast you are going except at sea level 15 deg C. 1013.2 mb. Calibrated airspeed which is indicated airspeed corrected for instrument errors. True air speed is how fast you are going in relation to the air around you, and ground speed which tells you how fast you are going relative to the ground. At any one time you are flying four different airspeeds and each gives you different information.

 

 

[Sapphire]

A lot of info here . http://www.australianflying.com.au/news/dragons-of-the-downwind-turn

Just read it and it supports my arguement. Inertia is what can kill you in a downwind turn because you loose speed in relation to the air around you. It takes time to move an a/c to it's downwind ground speed. The effect is more evident in a heavy inertia ridden a/c such as a heavily loaded crop duster. I withdraw my statement above it has little impact on day to day flying-the impact can be enormous.

 

 

[motzartmerv]

Saph. Some pretty confusing stuff there mate. I think you need to clear it all up in your own head before posting in the student threads.

 

1. Ground speed adjust itself?

 

2. Ground speed adjust for density height?

 

3. Turning into wind inhibits the stall? Care to explain that?

 

4. True airspeed is not just how fast you are going in relation to the air around you.

 

Please mate. This is the student thread, im sure they can google themselves to come up with similar findings to the ones youve posted and all it will do is add confusion and ambiguity.

 

Cheers

 

 

[metalman]

The way I understand it if you turn to downwind you create an immediate decrease in lift as your IAS will drop off. Then the plane is accelerated by trading off some height and you achive same IAS and same lift. Net result is less time in the air. Turning into wind is the opposite. Your IAS increases, and use that to stay in the air longer. However, turning into wind decreases your ground speed and turning downwind increases your ground speed. The one into wind will help you avoid a stall and allow a tighter turn. The wind gradient into wind will go against you compared to downwind. Work that all out in your one second reaction time.

So just so I'm not mis reading your post ,,if a pilot turns with the wind ( a tailwind )his IAS will drop and the plane will lose altitude,,,is that what is written above,,,

And a turn into a headwind will increase your IAS and lift,,,,,so enough of a tailwind ( not wind shear, no one has mentioned that yet) if we turn to quickly the plane may stall, please tell me that is NOT what you've posted, and if it is I'll PM you my address to send those welding rods( hopefully I can choose the specs)

 

Just so we can be sure do you have any documentation/ text books that have this "teaching"

 

 

[metalman]

Just read it and it supports my arguement. Inertia is what can kill you in a downwind turn because you loose speed in relation to the air around you. It takes time to move an a/c to it's downwind ground speed. The effect is more evident in a heavy inertia ridden a/c such as a heavily loaded crop duster. I withdraw my statement above it has little impact on day to day flying-the impact can be enormous.

I just reread that article, and I cannot see it written anywhere that a downwind turn will effect the IAS , ground speed ,yes turn radius ,yes ,obstacle avoidance yep, indicated airspeed nope

Look ,don't want to jump all over you , ask your instructor, even have another look through the BAK, sometimes this aircraft stuff can be a bit hard to get a grasp of

 

Cheers Met

 

 

[Sapphire]

Saph. Some pretty confusing stuff there mate. I think you need to clear it all up in your own head before posting in the student threads.1. Ground speed adjust itself?

2. Ground speed adjust for density height?

 

3. Turning into wind inhibits the stall? Care to explain that?

 

4. True airspeed is not just how fast you are going in relation to the air around you.

 

Please mate. This is the student thread, im sure they can google themselves to come up with similar findings to the ones youve posted and all it will do is add confusion and ambiguity.

 

Cheers

You guys have me pumping the keys tonight.

 

Ground speed adjust's itself - You are flying to a constant IAS of say 100 kts. Your ground speed becomes a figure based on wind velocity and density height and that 100kt IAS It simply"adjusts itself" to a figure based on those parameters. Eliminate the term "adjusts itself" if you find that confusing.

 

Ground speed adjusts itself for density height-explained above. Density height, wind velocity, IAS are parameters which affect ground speed. Increase the density height you increase the TAS which increases your ground speed [provided you maintain a constant IAS]

 

Turning into wind inhibits the stall-if you are the "inertia" believer as CASA is in the links provided in other recent posts in this thread, then turning from a high ground speed down wind into a head wind gives you more lift. Say you are going downwind at 120kt ground speed and you turn into a 20 kt headwind. Now momentarily you are doing almost 120 kts into a 2o kt headwind and inertia is allowing that. With your power setting constant the plane will slow down to 100kts ground speed and you will loose that initial extra lift.

 

True airspeed is not just how fast you are going in relation to the air around you-not true and never said it. Find it in my post and I'll eat the words.

 

 

[facthunter]

Once airborne you are doing it in a parcel of air that may be moving over the surface of the earth. You are not connected to the earth so when you do a turn through 360 degrees you just go around a circle in that parcel of air. To someone on the ground you are doing some sort of ellipse and appear to be accelerating and decelerating but if you hold your bank angle constant and change nothing your airspeed remains constant and the fact that you are in a wind means nothing to how the plane behaves except that you are being carried along with the wind and don't stay over one point of reference, as you would in a no wind situation. Same as if you are in a supersonic plane and you run around a circle . It is the same as if you are parked on the ground.( which is planet earth and is moving through the universe at some incredible speed but might as well be stationary as far as you are concerned. Nev

 

 

[Sapphire]

[qThey point out that if you suddenly turn round so the wind is behind you, the aircraft will not instantly accelerate to a groundspeed of 110kts (80+30). It is a heavy chunk of metal which has inertia, so it will take time to accelerate from 50 to 110 knots, and during this time the tailwind will cause it to lose airspeed and lift.

 

This explanation seems logical, but it has a major flaw. It’s based on the belief that groundspeed plays a part in the physics and aerodynamics of a body that is totally supported by the air. It doesn’t

 

I just reread that article, and I cannot see it written anywhere that a downwind turn will effect the IAS , ground speed ,yes turn radius ,yes ,obstacle avoidance yep, indicated airspeed nopeLook ,don't want to jump all over you , ask your instructor, even have another look through the BAK, sometimes this aircraft stuff can be a bit hard to get a grasp of

Cheers Met

The first word in the article above "They" are CASA and some other experts. The writer doesnt agree with them and his arguement is very flawed. If you read that artical he explains it away with aerodynamics. We are taking about inertial effects which are in addition to aerodynamic effects. CASA is right on this one.

 

 

[Sapphire]

Once airborne you are doing it in a parcel of air that may be moving over the surface of the earth. You are not connected to the earth so when you do a turn through 360 degrees you just go around a circle in that parcel of air. To someone on the ground you are doing some sort of ellipse and appear to be accelerating and decelerating but if you hold your bank angle constant and change nothing your airspeed remains constant and the fact that you are in a wind means nothing to how the plane behaves except that you are being carried along with the wind and don't stay over one point of reference, as you would in a no wind situation. Same as if you are in a supersonic plane and you run around a circle . It is the same as if you are parked on the ground.( which is planet earth and is moving through the universe at some incredible speed but might as well be stationary as far as you are concerned. Nev

How do you explain away the inertial effects Mr Nev? Don't say there are none or you will be assimilated.

 

 

[facthunter]

Inertia and kinetic energy ( energy of motion) do apply but you have to get your datum or reference point right. Your aircraft is not attached to the earth. and as I said the earth is hurtling through space at some crazy speed anyhow but you and I are blissfully unaware of it . What happens IF I am assimilated? Nev

 

 

[turboplanner]

One question Sapphire, have you actually flown an aircraft?

 

 

[Head in the clouds]

Gliding books discuss this effect in relation to entering thermals and changes in wind velocity....

This thread has turned into a classic, and I agree that it is very confusing for people trying to learn from the student thread. I think discussions like this is one of the reasons I got worn out with instructing.

 

I'm pretty sure that the quote above in Sapphire's post #46 is where the confusion stems from. While Sapphire has been discussing flying around in a moving body of air of constant velocity, I think he has actually been talking about very important teachings in glider training which refer to flying from one moving body of air into another body of air, and the two of those are moving at different velocities relative to each other.

 

The examples that Sapphire mentions describe the plane going from air travelling at say 10kts, into air travelling at say 20 kts. This situation is sought out as a normal part of soaring when entering or leaving thermals, given that the thermal is a rotating mass of air it depends on which side of the thermal you enter or leave it, to whether you enter air that is travelling toward the body of air you just left, or away from it. In the former case your aircraft plunges into the new air mass and until drag evens things out the planes inertia (momentum actually) does mean that for a short while the plane will be travelling faster through the new air than it was travelling in the old air, so there is a very noticeable increase on the ASI. And, if you were just about to stall in the old air mass, the increase in real airspeed should prevent the stall. This might not always be the case though because the rotating air mass is also ascending and the increased angle of attack experienced instantaneously by the wing might actually allow the stall to develop - but that's another discussion.

 

If you enter the thermal on its other side you would meet air travelling away from (relatively slower than) the air you just left, and it would also be ascending, so you would most definitely stall if you were about to stall in the old air ... And if you bear in mind that thermals are surrounded by cool descending air the situation is exacerbated.

 

Conversely, leaving the thermal you might exit it on the first side described above and meet slower descending air or you might exit it on the second side described above and meet faster descending air, the former might avoid you stalling if you were about to stall while in the thermal, and the latter would almost certainly prevent the stall.

 

The above also applies to powered planes that are not deliberately seeking out thermals. As you fly in a straight line and hit a thermal dead centre you will first descend as you meet the cool air mass descending around the outside of the rotating hot core, then you will meet air that will push the nose of the aircraft up and to the left (because the core is rotating clockwise in our part of the world) and if you were flying close to the stall you might well stall at that stage having gone from descending air to rising air, and nose high, then you will fly level in lift but the plane will be displaced sideways, first left and then right, and then you leave the ascending air to enter the descending air where the nose gets pushed left again and also it drops, before getting back to straight and level. Some folks call it turbulence, I call it free fuel if you fly slow in the lift and fast in the sink.

 

What happens if you don't hit the thermal dead centre, but instead hit it one quarter to the left or right side is a good mental exercise for any students who have persevered this long with this thread.

 

Similar things happen when transiting the earth's boundary layer, aka the wind gradient, but the difference here is that you are not flying from one air mass to another, instead the part of the same air mass which is closest to the ground has its speed reduced by the roughness of the earths surface - trees, rocks etc - and so when landing into wind there is less wind on the ground than at 100ft so you experience a loss of airspeed due to the aircraft's inertia and conversely, when landing downwind you experience an increase in airspeed as you descend through the wind gradient, which is one of the very few good things that can be said about downwind landings.

 

I hope that helps but I'm preparing myself to being Assimilated anyway, just in case ...

 

 

[motzartmerv]

True air speed is how fast you are going in relation to the air around you,

[motzartmerv]

Yea look, this is getting a bit silly now. I know where your getting this from Saph, its a theoretical argument that doesnt take into account the fact an aeroplane can NOT simply change its heading quickly enough to expereince any of the effects you are trying to explain (i think). We have seen it all before and have been through it all before. I think theres a myth busters ep somewhere ( i think) and I know the internet is full of "ahhaaa but what about this" arguments. I could argue that we are traveling at thousands of miles per second through space and stuff up an closed system argument. While some of this info could be usefull, I think your experiencing why being an instructor is not as easy as some people would think, and as such perhaps should post your ideas in a new thread or do an instructor rating (or pilots licence) :).

 

Cheers

 

 

[poteroo]

The old downwind v upwind turn eh?

 

For starters - it all depends on how much the pilot is affected by the downwind turn illusion of slip, or the upwind turn illusion of skid. And, the extent of this effect depends entirely on your operating height above ground level. (>500ft - next to no illusion, 300ft - moderate, 150ft - significant.) and the actual wind speed. Low altitude in wind of 15-20 kts and the illusions are quite strong and may trap the unwary. All is revealed when you do a proper low level course.

 

My take on the subject is this: pilot rolls into turn from upwind to downwind - during turn,peripheral vision says the a/c is 'slipping' - pilot applies more rudder in the direction of turn - which drops the nose -pilot applies back pressure to maintain 'height' , which loads up wing and decreases IAS - rolls out of turn -IAS increases back to that set, but not due to anything magical or mysterious. All to do with the illusion and using incorrect inputs. The downwind to upwind turn creates a similar, but opposite effect due to the skid illusion. Ignore the illusions - fly attitude and everything stays the same.

 

happy days,

 

 

[Sapphire]

Inertia and kinetic energy ( energy of motion) do apply but you have to get your datum or reference point right. Your aircraft is not attached to the earth. and as I said the earth is hurtling through space at some crazy speed anyhow but you and I are blissfully unaware of it . What happens IF I am assimilated? Nev

Suprisingly a simple turn into wind and downwind has so much unresolved debate in official quarters. I think the effects of inertia are most evident in a fast aerobatic type a/c doing quick turns in a strong wind. The case example given in one of the references is a plane doing just that, turning into wind, stalling and crashing. A crop duster pilot recounts similar scary experiences. As far as being assimilated Nev, if Seven of Nine [part Borg] does it, you will be lying down with stars in your eyes, tongue hanging out, and begging for more. She is very skillful and sexy.

 

 

[Sapphire]

Yea look, this is getting a bit silly now. I know where your getting this from Saph, its a theoretical argument that doesnt take into account the fact an aeroplane can NOT simply change its heading quickly enough to expereince any of the effects you are trying to explain (i think). We have seen it all before and have been through it all before. I think theres a myth busters ep somewhere ( i think) and I know the internet is full of "ahhaaa but what about this" arguments. I could argue that we are traveling at thousands of miles per second through space and stuff up an closed system argument. While some of this info could be usefull, I think your experiencing why being an instructor is not as easy as some people would think, and as such perhaps should post your ideas in a new thread or do an instructor rating (or pilots licence) :).Cheers

I thought you would conclude more professionally. There is no useful substance there.

 

 

[Sapphire]

Suprisingly a simple turn into wind and downwind has so much unresolved debate in official quarters. I think the effects of inertia are most evident in a fast aerobatic type a/c doing quick turns in a strong wind. The case example given in one of the references is a plane doing just that, turning into wind, stalling and crashing. A crop duster pilot recounts similar scary experiences. As far as being assimilated Nev, if Seven of Nine [part Borg] does it, you will be lying down with stars in your eyes, tongue hanging out, and begging for more. She is very skillful and sexy.

Make correction to above statement "turning into wind". Change "turning from into wind to downwind"

 

 

[facthunter]

When you plane turns "suddenly" (as if it is on a stick) the wind would act as you say. A control line aircraft does this. It flies into a headwind and then a tailwind and tends to have both a fluctuating air speed and a fluctuating ground speed, BECAUSE you have determined the centre if the circle to be a constant point. In the parcel of air, the point moves with the air current.The illusions of slipping and skidding make flying at low level in high winds risky unless you have done all the training and are aware of them. If you engaged an autopilot( that doesn't experience the illusions) it would perform a perfect turn relative to the parcel of air with no change of airspeed or power, provided the airmass was stable and uniformly moving at a constant velocity. Nev

 

 

[turboplanner]

So, the student has just passed solo, and he's off on his first session of circuits, but the engine cuts out in the Tecnam a hundred feet above the ground - if he'd memorised the information in this thread, would that be helpful to him?

 

Footnote: Note that I didn't use a ******** as an example

 

 

[facthunter]

At this stage No use at all. Reason the causes and effects have not yet become accepted More information or better arguments have to be presented. I warned at the beginning we should start a separate thread and that this subject had aspects to it that were hard to grasp sometimes because they appear anti intuitive. Nev