The hobbldy hoy nature of the ground handling

[Damocles]

Pilfered/plagiarized from elsewhere, (not written by me) but adds something to the debate I think.

 

"Ok, we're getting closer You have to remember that the generation of fighters designed in the early and mid-1030s with retracting undercarriages were the first ones to use what WE now regard as commonplace - oil-damped coil-sprung hydraulic dampers. In some cases they were only "lookalikes", the tubular legs being internally damped and sprung by rubber. All our cars use them for suspension nowadays, and we are isolated from the vibration of the engines in them by miniature versions of these dampers.

 

However, at the time these aircraft were designed - this hydraulic suspension technology was ALSO very new and far more primitive than nowadays. "Seals" were just hard-vulcanised rubber "o"-rings, "suspension fluid" was just plain rubber-nonfriendly oils, NOT latex-friendly seal-swelling synthetics. Designers could design and have built struts that would support the tons' weight of aircraft on landing...but couldn't in any way "tune" suspension units like they can today.

 

So, how in those days did you make a long-length and long-travel suspension strut that not only actually held up the aircraft's weight but at the same time was soft enough to cope with ALL types of surface? Remember, you CAN'T "dial in" performance like you can nowadays - how do you actually soften the suspension unit and still make it's preferably-long travel (to soak up the bumps) keeps the aircraft off the ground but isn't overly high?

 

The answer is simple, and something that has been neglected with time and better technology. You cant it over. Here's examples of the same model of postwar Veolcette motorcycle...these bikes were originally designed with their trade mark "arc of a circle" bracketry to allow the UNADJUSTABLE suspension units to be moved. Why?

 

 

Note the circled portion of the pic. The top mount of the suspension unit is moved closer to vertical - for a firmer ride with a fixed amount of travel...

 

BUT

 

 

...on THIS bike the top mount has been moved, canting the suspension unit over more. Why? To SOFTEN the same amount of suspension travel when you have no form of adjustment ON the strut

 

Thus a 109 with its struts canted forward and outward - canted in TWO directions from the centreline - has a softer but well-damped suspension action AND can have a longer travel.

 

 

So although the earlier marks of 109s had problems courtesy of narrow wheelbase on landing...they had BETTER suspension action than the more upright-in-two-directions undercarriages of the Hurricanes and Spitfires - leading to these having traditionally-"weaker" suspension struts. They weren't actually weaker - just had a harder action with less damping and travel so took more impact and thus wear/damage on landing.

 

(JF, check out the angle of rear shocks on 1970's twin-shock off road bikes you'll see what I mean)

 

Motorcycles were the first post-war application of this suspension technology, which was so new that only a couple of racing bikes had it BEFORE the war - the Kompressor BMWs of 1935-39 and the Gardengate Nortons of 1939. Cars/lorries relied on boring old leaf springs for decades afterwards."

[Yo-Yo]

Unblock the tailwheel in 109... just to compare in the same conditions.

Edited January 13, 2017 by Yo-Yo

[Damocles]

Am I correct in thinking that the weight balance of the Spit, fore/aft, i.e further forward was in the Spits favor, in mitigating against ground loops compared to the 109 ?

[Damocles]

Unblock the tailwheel in 109... just to compare in the same conditions.

 

I haven't time to try it now, but I don't doubt you for a second.

 

It does beg the question though, if the retro fitting of a tail lock was so effective on the 109, why wasn't a tail wheel lock also used on the Spitfire if the Spitfire also had problems with ground loops ?

 

I'll have to do some circuits in the 109 tomorrow night with the tail wheel unlocked. :joystick: :D

[MiloMorai]

“Chief aerodynamicist for the the Messerschmitt Me 163 rocket fighter, Josef Hubert ....told me that Willy Messerschmitt had adamantly refused to compromise the Bf 109’s performance by adding the drag-producing wing-surface bumps and fairings that would have been necessary to accommodate the wheels with the proper geometry. This would have reduced its accident rate to within expected military-fighter ranges and made it a world standard!”

I find that hard to believe as upper wing bulges were added when larger wheels were fitted to the Bf109.

 

DCS K-4

[David OC]

No he is entirely correct, when a tailwheel aircraft is in the 3 point attitude on the ground and moving the CoG is behind the main wheels and the laws of physics makes this an unstable condition, being alert and keeping it under control does not change the laws of physics.

 

This guy explains it pretty well, they know a thing or two about tailwheel at the commemorative air force.

Link only as the video owners have restricted playback on 3rd party websites.

 

 

Thanks for posting the video

 

I do like how the presenter explains in the video when a pilot lands a taildragger, he needs to be a better computer with a higher CPU clock speed. I.E. Detect fast and react quicker to movement.

 

I think putting it that way and relating it to PC's, we can all definitely relate to that here lol.

 

[*Aquila*]

It does beg the question though, if the retro fitting of a tail lock was so effective on the 109, why wasn't a tail wheel lock also used on the Spitfire if the Spitfire also had problems with ground loops ?

To save weight.

One shall note that many troubles on the ground go solved when the stick is firmly hold rearward. True for taxi, take off and landing as well. Continuously applying aerodynamic downforce is the key to deter the tail wheel from living its own life all by istelf, and so making yours a PITAS.

[NeilWillis]

I have come up with a brilliant theory. The Spitfire was never designed with clipped wings. They actually wore down to the square ends due to constantly being scraped along runways by inexperienced pilots.

 

I have no evidence whatsoever to support this, but like most flight model theories held on this forum, I'd say it is absolutely irrefutable - unless some pedantic "person" says we need documentary evidence, which would of course just be a way of hiding the truth.

 

You heard it here first folks!!!

[Yo-Yo]

I haven't time to try it now, but I don't doubt you for a second.

 

It does beg the question though, if the retro fitting of a tail lock was so effective on the 109, why wasn't a tail wheel lock also used on the Spitfire if the Spitfire also had problems with ground loops ?

 

I'll have to do some circuits in the 109 tomorrow night with the tail wheel unlocked. :joystick: :D

 

 

Is this answer helpful? :-)

By the way, Mr. Brunotte surprised me when he said that he did not lock the tailwheel in 109. "For better feeling"

Edited January 14, 2017 by Yo-Yo

[9.JG27 DavidRed]

what i do wonder in that regard is, if we will see an improvement of modeling the different surfaces, i.e. grass fields..or will it stay like its currently implemented?

cause keeping the tailwheel unlocked in the 109 is no problem at all on concrete runways, and in fact i prefer to takeoff and land without the locked tailwheel as well....

but landing in fields is a complete different story...its possible with unlocked tailwheel, but the really high side-friction of the modeled grass-surface makes this a really dangerous thing, and locking it, makes it a thousand times easier.

Edited January 14, 2017 by 9./JG27 DavidRed

[Anatoli-Kagari9]

And, after exchanging some very interesting thoughts with Klaus Plaza it was also evident to me that apparently the efficiency of locking the tailwheel in DCS is overdone.

 

He mentioned in some of his answers to my simmer questions that the tailwheel lock mechanism in the 109s is not very effective, and still requires quite a deal of foot and asymmetric toe brake work...

[Pilum]

First of all let me say I love the DCS Spitfire! A bit twitchy in pitch but that is as it should be as far as I can tell from historical sources like the NACA report L-334 which is a good read if you have not seen it so far.

 

Anyway when it comes to the ground handling I think the biggest problem we face was very well put by Zimmerdylan in this post: The lack och acceleration input simply makes it more difficult in general in sims which is also my experience comparing flying IRL: the acceleration cues tell you things are moving before you get the visual cue but by the time you see things moving you already have a problem in that you are already behind the game since you now have a swing going that you could have stopped earlier if you had the acceleration cue input.

 

Also from control theory we know that controlling a system through feedback things get more difficult if you introduce a delay in the feedback loop which we are essentially doing by being cut off from the acceleration input like we do in a sim. Does not make it impossible, just a bit harder and taking a longer time to get used to that’s all. So yes, I think Zimmerdylan has a point that it is more difficult in a sim. He is in the post I linked referring to IRL experience but I think control theory supports him as well.

 

In addition, sorry to have to say this but in order to get full enjoyment there are no shortcuts in terms of controllers: I flew for years with pot based plastic controllers but lately indulged: I now got a rig with hall sensors only: Warthog with 10 cm stick extension, MFG Crosswind pedals with the width extension and it makes a world of difference: Of course this does not eliminate the lack of acceleration feedback but it does make things easier to control.

 

That being said, when it comes to the current wing dipping tendencies in the Spitfire, did not the DCS Fw-190 go through a few iterations after it was released that tuned the ground handling and made it less prone to ground loop? At least I seem to recall that or maybe that was just me getting better at handling it through practice…..:smilewink:

[Damocles]

 

Is this answer helpful? :-)

By the way, Mr. Brunotte surprised me when he said that he did not lock the tailwheel in 109. "For better feeling"

 

Sorry Yo Yo but that is totally irrelevant. It's obviously a training machine, not a front line fighter and if the colour is anything to go by, nothing like PRU or Desert pink, then it definitely calls into question the attention to detail in other parts of the build.

[David OC]

 

In addition, sorry to have to say this but in order to get full enjoyment there are no shortcuts in terms of controllers: I flew for years with pot based plastic controllers but lately indulged: I now got a rig with hall sensors only: Warthog with 10 cm stick extension, MFG Crosswind pedals with the width extension and it makes a world of difference: Of course this does not eliminate the lack of acceleration feedback but it does make things easier to control.

 

I have spoken to pilots that say most controls IRL aircraft can have a noticeable play in them and things like hall sensors are just an extra accuracy items for us simmers. I do believe it’s the height and throw length more than anything, like how you have the extensions fitted, not sure how ED balances this out with all the controllers out there. I know you can limit an axis and curve them, so would you need to limit the axis throw if you were to use a full scale replica stick or is the scale of the throw and height set to full size control movement to begin with?

[David OC]

Here is my scientifically tested, old joystick broom handle test. It works great for the choppers too. lol

 

Edited January 14, 2017 by David OC

[Pilum]

I have spoken to pilots that say most controls IRL aircraft can have a noticeable play in them and things like hall sensors are just an extra accuracy items for us simmers. I do believe it’s the height and throw length more than anything, like how you have the extensions fitted, not sure how ED balances this out with all the controllers out there. I know you can limit an axis and curve them, so would you need to limit the axis throw if you were to use a full scale replica stick or is the scale of the throw and height set to full size control movement to begin with?

 

Maybe I should clarify: The reason I got rid of my old rig was that the pots were giving up: the stick was shaking like crazy and the throttle was not constant: Using the throttle as collective for the Huey or Mi-8 required constant attention since the pots were drifting.

 

I do however think the MFG Crosswind would have helped even if the used pots instead of hall sensors: They are wide apart and for the rudder does a similar job to your nifty broomstick extension. :smilewink:

[Pilum]

Also: I did a few quick take-off and landing tests with the Me-109K4 with tailwheel unlocked and you have to be pretty quick on the toebrakes there as well if you don't want to scrape a wing so I don't know if I agree that the Spitfire is so much worse? After all it does not have a lockable tailwheel like the Me-109.......

[Schwarzfeld]

IMO if you wanna be a hot dog and fly the 109 on take off with an unlocked tailwheel, you better get the tail up and roll on the mains ASAP once you get rudder authority and dance the brakes up to that point.

 

Frankly, in a plane with that narrow of landing gear and as fast as the 109 needs to get going for full rudder authority, personally I think unlocking the tailwheel on the 109 in the sim is just showboating - you'd NEVER do that in a real one, EVER.

[NineLine]

Here is my scientifically tested, old joystick broom handle test. It works great for the choppers too. lol

 

 

That is so McGyver lol... although I wish there would have been more duct tape :)

[NineLine]

And, after exchanging some very interesting thoughts with Klaus Plaza it was also evident to me that apparently the efficiency of locking the tailwheel in DCS is overdone.

 

He mentioned in some of his answers to my simmer questions that the tailwheel lock mechanism in the 109s is not very effective, and still requires quite a deal of foot and asymmetric toe brake work...

 

Reference?

[Sporg]

IMO if you wanna be a hot dog and fly the 109 on take off with an unlocked tailwheel, you better get the tail up and roll on the mains ASAP once you get rudder authority and dance the brakes up to that point.

 

Frankly, in a plane with that narrow of landing gear and as fast as the 109 needs to get going for full rudder authority, personally I think unlocking the tailwheel on the 109 in the sim is just showboating - you'd NEVER do that in a real one, EVER.

Well, as Yo-Yo said, Erich Brunotte clearly stated he preferred not to lock the tailwheel.

He flew in that era, you know. ;)

 

Secondly he said he never used brakes on take off, except for getting RPM up on particularly short fields.

[dburne]

I do not use brakes on take off either, I did at first but found it better at least for me not to use them.

[Whisper]

Secondly he said he never used brakes on take off, except for getting RPM up on particularly short fields.

Didn't he he say he never used brakes on the 190 on take off, but brake could be needed (right side) sometimes on the 109 on take off roll?

[Davee]

Have you seen Matt's video with TO and landing? He used the same FM. But he really had encountered the problem you describe before he got the right way of handling.

Perform please an experiment with TO assistant ON. But DO NOT FORGET TO ADD BRAKES after these 10 seconds, because your rudder inputs gets useless at low speed, and the plane breaks away. You can check it. The only force that can dip the wing is INERTIA, and it appears as the plane begins to turn.

 

Hi Yo-Yo,

I've completed my evaluation of using TO assistant and note that there still is an issue in my mind.

 

I say this because watching the rudder pedals during roll-out, I notice fine adjustments and at the same time I see no swing at all in the nose/tail. The aircraft is tracking true and I think it is unnatural to assume that the rudder dancing is influencing it that much.

 

My take on this is that the AI of the TO assistant is making calculations based upon other calculations that I can't feel or see.

 

With no TO assist, I can track straight and true in the same manner as with TO on - however, there may be some force being applied that I cannot detect as I am at a computer and not feeling what is happening in a real cockpit.

 

I submit, that even though the calculations may be correct according to the "book", the translation into what is being experienced behind a computer screen is not. I think that there needs to be some tweaking to transmit what is happening to the aircraft in order to provide some time for the virtual pilot to detect it and then to react. Not enough response time between being aware (if at all), to the tail is breaking out.

 

For me, I'm putting the Spit to bed for a while and wait and see what is being changed down the road.

 

Cheers,

Cats . . . .

[Yo-Yo]

Hi Yo-Yo,

I've completed my evaluation of using TO assistant and note that there still is an issue in my mind.

 

I say this because watching the rudder pedals during roll-out, I notice fine adjustments and at the same time I see no swing at all in the nose/tail. The aircraft is tracking true and I think it is unnatural to assume that the rudder dancing is influencing it that much.

 

My take on this is that the AI of the TO assistant is making calculations based upon other calculations that I can't feel or see.

 

With no TO assist, I can track straight and true in the same manner as with TO on - however, there may be some force being applied that I cannot detect as I am at a computer and not feeling what is happening in a real cockpit.

 

I submit, that even though the calculations may be correct according to the "book", the translation into what is being experienced behind a computer screen is not. I think that there needs to be some tweaking to transmit what is happening to the aircraft in order to provide some time for the virtual pilot to detect it and then to react. Not enough response time between being aware (if at all), to the tail is breaking out.

 

For me, I'm putting the Spit to bed for a while and wait and see what is being changed down the road.

 

Cheers,

Cats . . . .

I guess your seeing of the things is too complicated... so it's obviously wrong. I am glad that you understand the problem right but the only thing I can recommend is to use the TO assistant gradually lowering its authority as you getting the skill.

TOA does not use any "book calculations", no mysteries. Just simple tracking feedback basing on the feeling we have in real world. But instead of them one can train the ability to get them not from your body sensors but from the visual perception - getting angular speed and acceleration from visual cues.

Add a rudder pulse to confuse TOA, then watch the replay at 1/2 or 1/4 speed, notice the phase it applies rudder relative to angular velocity of yaw.

Find how much braking you need to keep steering authority.

Then, start from 80% of TOA trying to keep the plane straight. Read the part 3 of the Essay first and try to steer following the advices... as you are successful then lower the %%.

 

Or keep the TO assistance on...

Edited January 15, 2017 by Yo-Yo