Yo-Yo
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Posts posted by Yo-Yo
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On 5/18/2024 at 8:42 PM, razo+r said:
Either be fast enough or don't pull too hard.
Also, don't compare with AI. They use different physics compared to players.
They use the same trajectory physics and the same energy possibilities (drag, induced drag and propeller effective power) as human. The only difference is that AI carefully manage energy never pulling excessive g.
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Спасибо!
On 4/11/2024 at 1:55 PM, shwed said:Эти усилия вы можете напрямую транслировать в джойстик и педали, и управлять усилиями на них и их поведением, и такие устройства стоят у вас в офисе
Десяток-другой килограмм на домашнем джойстике?? Или что?
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1 hour ago, Eponsky_bot said:
Я в свое время делал сравнение с Ил-2 .
Строй держать нереально вообще. А вертолеты это отдельная боль
Разница огромная: один зеленый, второй белый. И один в правом вираже, второй - в левом.
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13 minutes ago, Bozon said:
The angle of attack is increasing both for the main wing and the tail. Since the airspeed is more than sufficient to hold the tail up, the plane will want to return itself to it's "trimmed" (could also be stick held) AoA, i.e. respond in a pitch down with a phase delay. There is a time-scale to this process of increase-decrease in AoA - if this time is of the same order or sorter than the compress time of the main gear strut, the aerodynamic bounce will be small. A stiff strust creates a short travel has a short compression time, which increases the bounce.
And this just proves that you need very low sink rate to avoid ballooning, because generally the time constant of mechanical system "undercarriage suspension - longitudinal MOI" is sufficiently lower than time constants of aerodynamic moments at low landing speed.
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1 minute ago, kablamoman said:
I trust that something is up. The way the tail wheel is erratically bouncing in a lot of the videos looks problematic, as well as the fact that it seems to get damaged shockingly easily. Hopefully that's something that they've fixed internally already.
I was just trying to provide some clarity about the tail down moment during a wheel landing. It's the biggest thing you have to worry about with wheel landings in real life, and depending on the plane, the wheels spinning up may or may not be a whole lot of help. The tail typically produces a net negative lift, so I'm afraid without carefully timed nose-down/tail-up elevator it's not going to prevent the nose-up torque on a wheel landing.
The tail wheel bouncing has no relation neither to the main wheels and touchdown behavior nor to wheel physics at all. It is a matter of surface noise model and has a quite complicated nature similar to aliasing problem. It is not so noticeable for the old model, but some small wheels having the new model can be affected with it. We are trying to change things, but it requires time because of its complexity.
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31 minutes ago, 4eyes said:
Arguing about all this really doesn't matter.
Solution: Give us a choice. Keep the aircraft as is, and give us novices a choice to use a easier aircraft to land.
Give us a choice.
What's so hard about that?
The choice is well known:
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55 minutes ago, Slaobladder said:
I beg to differ...a lighter aircraft will want to bounce more with the same airspeed, flap angle, etc. The fact is the dcs Mossie causes excessive bounce/pitch up on landing. Do you have Normandy 2 to test not a perfect concrete runway?
I am afraid, your opinion about tail dragger kinematic is very far from reality.
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45 minutes ago, Slaobladder said:
We have shown you many videos of real Mosquitos landing, a modern Mossie aircraft is carrying hugely less weight and more prone to a bounce which clearly doesn't happen. I have landed the dcs Mossie a lot at different sink rates and the effect is the same a bounce and instant nose high attitude followed by the tail slamming in to the floor. That last video I showed you clearly shows the compliance in undercarriage as the aircraft is taxiing over the grass. If you have Normandy 2 map taxi around St Pierre or San Croix and you will understand the harshness in the gear which given the low tyre pressures run with the Mossie don't correlate, the tailwheel is equally harsh but also fragile. I even had one break being dropped to the deck once a repair had been completed. A tail dragger like the Mossie will skip down the runway and the gear spinning up and subsequent braking effect will promote a nose over and keep the tail in the air.
"and LESS prone to bouncing" you probably wanted to say? Because the bouncing tendency or AoA increasing has its cause in three things: an arm between contact points and CoG, the MASS (the more is the mass the more pitch-up torque will be generated) and sink rate.
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3 hours ago, Slaobladder said:
The fact is the DCS mossie struts appears to be fully extended the whole time which is contrary to all the images and video shown of even post war lighter mossies in these vids. They also show there isn't a violent nose up attitude at touchdown as per the dcs flight model and also show the tail to carry lift and not slam in to the runway causing damage. Another vid I found showing the strut length and tailup attitude down the runway.
I think that nobody read this forum... especially ED answers. Yes, the struts already adjusted down, but IT IS NOT A REASON of nose pitch up. (Too many times was mentioned on the forum, as well). There are two main reasons of it for tail draggers - high sink rate at touchdown and high GW of the aircraft.
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12 hours ago, Terry Dactil said:
Yes I do. The way the rebound gets damped.
The whole point of a shock strut is for it to rebound much more slowly than it compresses.
The Oleo strut does this with different one-way restricting orifices controlling the fluid flow past the piston. With the Mosquito, if the hole in the rubber block is tapered then the sliding resistance on the tube will be more in one direction than the other. Same effect. It stops the strut being just a spring.
The only problem is that in fact rubber blocks, as the drawing shows, have no friction contact with the case or any fixed part of the strut. Energy is absorbed using internal friction of rubber that is symmetrical during a compression cycle. And it is absolutely right approach to do it. Friction in this case is the worst way for it because the heat can not dissipate from the contact zone and rubber will burn and wear every time the strut is used. The energy at the touchdown can be estimated as 4500*1^2/2 for 1 m/s strike velocity that gives up to 5-7 kW of power concentrated at the surface. Remember, how rubber belts smoke and fire in seconds as the pulley is jammed even at small engines. Moreover, as you are trying to use friction for the stack, you will see that only lower block moves full travel, while the majority of blocks move much less or simply stays in place, and provides no significant work at all.
Any rubber details has its internal energy dissipation, otherwise your garden wheelbarrow would bounce for minutes as you drop it. It stops bouncing after several times. But if it had a oleo-pneumo strut it would react exactly as in your video. -
8 hours ago, SMH said:
Yeah, doesn't look like a lot of compression. (That's the bomber variant but I suspect the gear are exactly the same. The fighter/bomber was an afterthought - explaining why many of our instruments are behind our gunsight!)
And it also shows just how much shock the tires take up. What are they inflated to? How's that compare to P-47/P-51 tire pressures? I'm guessing a lot less.
And surely there's a maintenance manual somewhere that says exactly what compressions we should expect on the struts under what weight conditions.Except the fact that the manual gives the numbers for fully dead rubber stack.
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14 hours ago, Terry Dactil said:
Here is how a real landing gear works.
Note the long compression stroke and then the very small and highly damped (slow) rebound stroke.
It does not work like a spring!
Do you see a difference between rubber blocks and gas-oleo struts?
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6 minutes ago, Holbeach said:
Full load 20500lb (22500lb in DCS) minimum is 1.75 inch. Plus 20mm is 2.6 inches of tube showing. I'll take that.
Min load 14000lb (16000 in DCS) minimum is 3.0 inch. Plus 20mm is 3.79 inches of tube showing. I'll take that.
..
Yes, we changed it, and it will merged sooner or later.
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Anyway, the manual contains just terminal compressions for fully degraded rubber blocks. It means that physical parameters of the rubber degraded. But the initial compression is not available.
But, I am not sure I see this information here, in this degraded conditions the manual directed to replace half-size block to full-size. This can add about 20 mm to the numbers specified in the table, and this is what we can do for the struts in DCS. So, the strut will be authentic for refurbished one. -
So, the initial procedure for good 2-wheels landing:
1. 10-15% of fuel, no bombs.
2. VSI zero mark area is visible (adjust camera position left, but only to see this area, not more)
2. Maintain 210-220 kph at normal stabilized approach.
3. As the wheels is about 2-3 m from the ground, start lowering VS to 50-100 fpm watching steady IAS app. 200-210 kph.
4. As the new VS is established do not touch the throttle, use only small stick deflection to maintain VS.
5. Wait.
6. As you feel ground, move the stick forward a bit as a mongoose and fix 2-wheel attitude.
7. Slowly retard both throttles. (Slowly forward throttles and go-around, if the airfield fence is too close). Freeze the stick and enjoy, you are cool.
8. Wait for the tail lowering itself. -
On 4/30/2024 at 9:46 PM, Lixma 06 said:
I can't realistically land with a lower sink rate than this...
...and yet the plane rebounds into the sky like an electric shock, and thus begins the inevitable rodeo session.
I can only say that attempts to 2-wheel landing with full fuel load from ME will not be successful. The landings you see in videos are performed for much lighter planes. I think, that I have not to explain, why GW is directly affects the pitch-up torque t touchdown.
The second thing that is important: stabilized low vertical speed and IAS. IAS is important to be sure that the desired low vertical speed is the same up to the moment of touchdown.
In this video the speed just before the touchdown lowers from 208 to 200 kph that means that the plane lost about 8% of lift, and the vertical speed increased. As you can see, g-meter shows 0.9 g instead of 1 just before the touchdown.
And the third thing: small forward moving of the stick JUST AT THE MOMENT of touchdown . Not before and not too late, both cases worsen the situation, but if it is done in time it really works.
In this video one can see constant vertical speed and the almost constant IAS before touchdown. Anyway, small forward stick was used as well.-
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2 hours ago, Dragon1-1 said:
Was it a deliberate wheelie landing, or did you just miss the three-pointer?
Also, nice going with the brakes at the end.
But hey, at least it's not the Spit, which would've likely ground-looped at that point...
It was "low tail" touchdown that frequently happens during planned three-point touchdown. It is safe as a three-wheel landing, especially if you stop to pull the stick after main wheels touch the ground. But even if you miss this point nothing serious will happen - the additional AoA is low, speed is bleeding. and the bouncing will not be excessive.
This is an example:
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Yes, very, very bouncing...
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On 2/27/2024 at 8:34 PM, shwed said:
Я собираю усилия и логику работы ОУ для разных ЛА, для последующей реализации на большом железном ффб, этим графиком один из пользователей поделился.
Эти усилия оптимизированы под реальный самолет с реальными перегрузками.
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On 3/11/2024 at 10:51 AM, HmtSabotage said:
Всегда было интересно - а зачем впринципе такая большая температура охлаждающей жидкости, что она кипит про разгерметизации системы? Чего бы не держать её скажем 60 градусов? Я не двигателист конечно, но понимаю что есть прогрев двигла, но вот перегревать то нарочно зачем?
Элементарно. Чем выше температура, тем больше теплоотдача в воздух в радиаторе при прочих равных.
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2 hours ago, Slippa said:
Can you tell us which map you’re using to fly in and out of Duxford please?
Also, could I have a copy as a late Christmas pressie?
Only a paper map.
I mean that Duxford airfield is much smoother than a lawn where I measured friction.-
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If we want to find a state for a time moment when the plane stops sinking its CoG, the stroke length DOES NOT MATTER. As I wrote before it's only a matter of momentum. You can expand this process or make it very short - the resulting angular velocity increasing your AoA will be the same. The only difference could be that very long stroke and long time of angular velocity rising allows to react and pull the stick forward.
But anyway, the strokes for any certain plane is determined, so we have to deal with real parameters.
Regarding the second pint: I thought that you meant only initial moment of wheels acceleration at touchdown where rolling friction is not relevant. But, I have to say, that my experiments with the different types of rolling friction for pneumatic gave exactly the same results for quite uneven grass surface (Duxford airfield is much smoother) and smooth tarmac.
The reason is that in steady movement bumps are averaged.
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By further investigation the recommendation to have 0.3-0.5 m/s sink rate at touchdown are proven. Though it requires a lot of training without RL cues, FM and tires itself are ok.
Except low sink rate that must be almost constant at least for several seconds. the speed must not be too high or too low - the higher speed is the more extra lift will be due to increased AoA.
My touchdown was at 0.6 m/s and it can be considered as a limit for actual gross weight about 7600 kg to perform a wheeler.P.S. Engines on idle just after touchdown prevent from possible bouncing reducing speed and wing lift due to downwash.
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Controllability Above 20k Feet
in DCS: P-51D Mustang
Posted
Yes, they have a copy of cooling system human plane has.