fixed Mosquito landing gear strut incorrect operation..

[Slaobladder]

1 hour ago, Yo-Yo said:

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.

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. 

 

[Holbeach]

10 hours ago, SMH said:

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. 

The tyres on a P-51 are a skinny 27 inch, (To fit inside a thin wing) at 45psi and the Mossie a fat 16 inch at 39psi.

There is no requirement for compression measurements on new struts, only for max wear limits.

But there are dozens of pictures out there, showing where the strut should sit when under load.

I'll put this one up again, showing Kermit Weeks late model at less than full load.

..

Edited May 9, 2024 by Holbeach

[Yo-Yo]

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. 
 

[Slaobladder]

43 minutes ago, Yo-Yo said:

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. 
 

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.

[Holbeach]

This shows how a main wheel landing should be done, no not by me, but I wish it was.

 

 

..

[Slaobladder]

5 minutes ago, Holbeach said:

This shows how a main wheel landing should be done, no not by me, but I wish it was.

 

 

..

Look at the tailwheel....you can hear it rattling around as well....

[Slippa]

If any of us simulated ourselves into the Mossie we have now we'd be in bleedin traction.

I'm no engineer and I don't have a degree in aeronautics but if I get in my Mos on any map, it's just not sensible on the ground as it is.

[Yo-Yo]

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.

[NineLine]

16 hours ago, 4eyes said:

I thought we were going to get a fix?

There are some changes coming, but I believe Yo-Yo is trying to describe that the changes won't do everything that is expected here. 

[Slaobladder]

2 hours ago, Yo-Yo said:

"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.

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?

Edited May 9, 2024 by Slaobladder

[Yo-Yo]

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.

[kablamoman]

59 minutes ago, Slaobladder said:

I beg to differ...a lighter aircraft will want to bounce more with the same airspeed, flap angle, etc.

Generally, the above may be true, but you may not be understanding the kind of "bounce" Yo-Yo is describing. It's something unique to tailwheel aircraft with the center of gravity behind the main wheels. If you try to land on just the mains with any kind of sink rate, the center of mass behind the wheels will want to keep going down when the mains touch, which means it will generate a pitch-up torque, which increases the angle of attack of the wings, generates additional lift, and lifts you off the ground again. If you try to correct it by pushing the nose back down, you'll most likely induce an even worse pitch-up moment the second time around, and so on, leading to a kind of PIO that bounces down the runway.

A successful wheel landing means accounting for this by minimizing sink rate and will probably also require some properly timed nose-down elevator to damp any nose-up tendency.

Edited May 9, 2024 by kablamoman

[Yo-Yo]

 

[Slaobladder]

34 minutes ago, kablamoman said:

Generally, the above may be true, but you may not be understanding the kind of "bounce" Yo-Yo is describing. It's something unique to tailwheel aircraft with the center of gravity behind the main wheels. If you try to land on just the mains with any kind of sink rate, the center of mass behind the wheels will want to keep going down when the mains touch, which means it will generate a pitch-up torque, which increases the angle of attack of the wings, generates additional lift, and lifts you off the ground again. If you try to correct it by pushing the nose back down, you'll most likely induce an even worse pitch-up moment the second time around, and so on, leading to a kind of PIO that bounces down the runway.

A successful wheel landing means accounting for this by minimizing sink rate and will probably also require some properly timed nose-down elevator to damp any nose-up tendency.

 

Trust me a number of us fly the Mossie and all experience this issue this is why so many people comment. When you touch down on the runway the spin up of the main gear is a braking force which counteracts tail drop, the tail its self is still producing lift as well at landing speed. All I have seen are videos of the same perfect concrete runway, try St Croix or St Pierre in Normandy 2, also watch that videos tailwheel skipping around, they simply don't do that the tyre takes up alot of the damping.

[Yo-Yo]

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:
 

 

[kablamoman]

13 minutes ago, Slaobladder said:

Trust me a number of us fly the Mossie and all experience this issue this is why so many people comment. When you touch down on the runway the spin up of the main gear is a braking force which counteracts tail drop, the tail its self is still producing lift as well at landing speed. All I have seen are videos of the same perfect concrete runway, try St Croix or St Pierre in Normandy 2, also watch that videos tailwheel skipping around, they simply don't do that the tyre takes up alot of the damping.

I trust that something is up. The way the tail wheel is erratically bouncing when rolling on smooth surfaces 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.

Edited May 9, 2024 by kablamoman

[Yo-Yo]

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.

[Bozon]

46 minutes ago, kablamoman said:

Generally, the above may be true, but you may not be understanding the kind of "bounce" Yo-Yo is describing. It's something unique to tailwheel aircraft with the center of gravity behind the main wheels. If you try to land on just the mains with any kind of sink rate, the center of mass behind the wheels will want to keep going down when the mains touch, which means it will generate a pitch-up torque, which increases the angle of attack of the wings, generates additional lift, and lifts you off the ground again. <snip>

 

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.

[kablamoman]

1 minute ago, Yo-Yo said:

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.

Great to hear! Thanks, and best of luck.

[Yo-Yo]

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.

[Slippa]

I’m already on the naughty step so I’m trying to be patient and tread lightly with this.

The idea came from a good place and all too obviously must’ve made good sense on paper somewhere. We’re all after improvements and have to accept to a degree that things will change a bit along the way. At least now there’s some acknowledgment that enough of us really aren’t happy with what’s been done. Hopefully, we’re past the brick wall ‘there’s nothing wrong with it, read my data’ stuff and we can get it back on track, pardon the pun.

i’d have been happier if we’d have been warned or as 4eyes says have had the option to stay with what we had. At least until someone had tried and tested the experiments properly. Hopefully, we’ll get something sensible back that we can be happy with. Not everybody’s gonna love it all but no matter what data goes into the tinkering, it’s got to be practical. Like I said, at least now it’s being looked at.

Or… Give us our old Mossie back, pre-super-suspension and start work on another marque from the dream-team for future release (and sales)?

Plenty of ideas and time to get it lovely .

Lots of work.

 

[NineLine]

Well, no one is in trouble, well one person but they chose the red pill. I am mildly interested in the fact that this might be affected by the terrain, and why we might see it more on one map than another. I am looking into this for sure. So keep sharing and keep engaging, don't be worried unless you start calling people names or anything like that you will be fine

[Slippa]

Ah, ok then 

cheers bignose . 

[NineLine]

6 minutes ago, Slippa said:

Ah, ok then 

cheers bignose . 

Ouch... right in the feelings

Hey, can everyone do me a favor that is having issues? Can you all do some comparison landings on the Caucasus, The Channel, Normandy or any other extra map you have? It can be Caucasus vs any other map. I just want to see if you guys also see a difference. I had noticed it myself and just thought I sucked

Make sure all things are equal, load and weather, etc.

[Slippa]

Just logged in as I thought the same thing. I have every map bar Afghan and will check it out, save tracks etc.

Problem I have is I’m having a bit of a Loach-affair with Tobi & Eightballs’ creation. Time in the Mossie vs lashing myself about dropping all kinds of coloured smoke. I’m plastered in face-paint unsure if I’m Martin Sheen, Marlon Brando or Dennis Hopper. I know, I know, it’s Hopper .

I’ve already tested and tested on the Channel from different airfields, same loads. A lot more on N2 and not a lot on the others but I will .

But… coloured smokes man! Imagine the Mossie with something crazy like target indicators and flares? 

Edited May 10, 2024 by Slippa
Typo