Conspicuous by Their Absence

[Ivan]

Messerschmitt 109E TROP is Finally DONE!

This critter is finally finished. There is certainly more that can be done, but the same can be said of most of my projects.
The result doesn't look half bad though the texture could use some reworking.

The Messerschmitt 109E had quite a few objectionable characteristics which were partially addressed with the Me 109F.

Now that the workspace has been cleared, time to move something else into the workshop.

- Ivan.

 

[Ivan]

Uncontrollable Sideslip

Hey Womble55,

I remember you mentioned an aeroplane you were working on that could not control its altitude loss with a sideslip and even mentioned it in this thread.

I don't really want to search through several hundred posts, so can you remind me which one it was?
I might have a workable solution for you.

- Ivan.

 

[smilo]

Vickers Vernon?

i'm not womble, but,
would post #724 on page 29
be the one you are referring to?

just below the threat title: is a menu with thread drop downs.
one is Search Thread. i typed in sideslip and got page 29.

 

[Ivan]

Thanks Smilo,

I did a similar search, but when the results didn't show the "sideslip" text, I didn't dig further because I thought it was not getting the correct posts. I also did an "Advanced Search" instead of just searching this particular thread, so the good hit was probably lost in the noise. Advanced MUST be lots more better, right???

Thanks again.

oddly, i was just reading about the first two 109F prototypes.
apparently, v21 and v22 had the wing span reduced by 61 cm (2ft).
this was accomplished by clipping the tips.

I came across that story in a Luftwaffe aircraft book. Funny how that was the original intent: to REDUCE the wing area.
It reduced agility to such an extent they had to put back the wing area which they did with a rounded tip. I always thought the rounded tip looked so much better than the square tip wings.

Debating on starting a later version of the Messerschmitt.... I have always wanted a late G model or a K.

- Ivan.

 

[womble55]

My God, that was a while ago.
The sideslip was appalling and unless a gentle turn was instigated, a severe height loss was on the cards. A 360 degree would take up most of southern England, not good.
I followed the advice given and use the Air file from the P51D as a starting point and not use a file from a similar aircraft in my collection gathered over the years.
The progress I make by subtle changes in power, wing area, weight, engine positions, et al, are saved as a separate air file named in sequence.
When the performance changes for the worse back I go to the previous one.
This works for me and has stood me in good stead from the smallest (Christmas Bullet) to the largest (BV238).

 

[Ivan]

Hello Womble55,

The reason I was asking is because I was recently experimenting with Side Force due to Yaw Angle and found that I could mess with the sideslip to any extent I wanted. I had the Me 109 exceeding the speed of sound going sideways!
The trick is to figure out how much is reasonable to add as a correct side force so that the aeroplane handles well.

Thanks to Smilo, I found the Vernon installed on my development machine and was messing with it a bit last night.
I don't know how far you got with your P-51D derived AIR file, but the one I have wasn't very flyable.
Besides sideslip, the stability is very low in every direction. Problem is that I don't know how the real one flew.

I am also still working out a way to figure out numbers to plug in. I don't want them able to fly sideways faster than they can go forward! The original idea was to tweak my old Eindecker which had a pretty similar problem with sideslip even though it was still flyable.

This is kind of how things work in my little workshop. I start off wondering how to texture somethng such as the Albatros and then think about doing the AIR file for it, and then go to a similar aeroplane like the Eindecker and then to the Vickers Vernon. Hopefully something useful will come of this little trip....

- Ivan.

 

[womble55]

It's so refreshing to know that I'm not the only on that gets sidetracked easily.
As the available Bumpf about the Vernon's flight characteristics and indeed a lot of other aircraft is non existant, an educated guess is the best we can do. I'd say the Vernon was pretty stable with few vices (If it had any bad traits then there would be a mention somewhere).
At a guess, the turning circle would be in the region of 600 to 800 yds, maybe at the lower end once the wing loading for empty and loaded was calculated. Climb would not be of a figure to write home about, so 300 to 500ft per min would suffice.
I don't think sideslip was a problem with the Vernon, again, no mention in any book or website. Not even for the Vimy, Valletta or any of the similar aircraft of that era.
With my luck these comments will now generate a plethora of available flight data for the Vernon, previously unavailable via the ordinary search engines and books.

 

[smilo]

i wouldn't go so far as saying it's refreshing
to know others are easily sidetracked or distracted.
i believe i have taken it to being a lifestyle.

a friend once described it as old man's disease.

i wouldn't know what to do if i could stay focused.
i tried once, but forgot what i was doing.

 

[Ivan]

That friend who described it as an old man's disease probably doesn't remember that he also had it when he was a young man.

My son has had it for a very long time though with him I believe it is selective. If he wants a new toy or is trying to explore a video game, he is very singleminded....

- Ivan.

 

[Ivan]

Uncontrollable Sideslip

Last night, I decided to experiment a bit.

I loaded up and tested a bunch of aeroplanes, both stock and add-ons.
NONE of them could fly a knife edge over the field.
After that, I figured I would test the aerial ballet dancer: The FS98 Extra 300. (I have two FS98 installations.)
That aeroplane could not do it either. I must not know how to fly this maneuver properly.
I must be doing something wrong. Will have to check again tonight.

Maybe I need to find a Gee Bee or a Pitts to try?

- Ivan.

 

[smilo]

a couple posts to reply to;

your old man's disease comment made me smile.
it's too true, and it's not just a guy thing,
although, it seems our cases are much more acute.
heck, come to think about it, i've always had it.
at least, as far back as i can remember.

about the knife edge maneuver;
never tried it, but, most likely, will. shortly
have you tried it in a jet?

granted, pilot skill is essential, but,
controller sensitivity (or lack there of) comes to mind.
for example, go into settings, game controllers... properties.
does the + in the X Axis/ Y Axis window bounce around a bit?
how about the rudder Axis? does it bounce?
and notice that the axis' move when you simply
put your hand on the controller.

another control issue i find aggravating;
is it just me, or does anyone else find
it difficult to just fly straight and level?
it doesn't seem to matter what i'm flying,
although, some aircraft are better than others.
when i attempt to trim, either left/right or up/down,
i can never get it just right. or should i say, correct.
i can get it trimmed close, but,
it always seems to drift one way or the other
and one tap of the trim key usually sends it
in the opposite direction...never centered.

another interesting little quirk i've noticed is,
if i get it trimmed close to straight and level,
sometimes, the trim setting is lost if i maneuver
using the rudder, elevator or ailerons.
then, i have to do the trim process again from scratch.

in the end, the only way i can fly straight
and level is to turn on the auto pilot
which doesn't seem very realistic to me.

dang...there was one more comment i wanted to make,
but, i forgot what it was.



THERE IT IS! i remember, now

i know the excitement of the kill has an effect,
but, my aircraft seems to move all over the place
when approaching a potential victim.
for some reason, i can not keep my aircraft stable for the shot.
the slightest controller movement seems to over compensate
and i invariably loose my position on the target.
and yes, i have tried backing off the controller axis' sensitivities.
i've even tried using the keyboard
instead of a controller button to fire the guns.
that helps a bit, but doesn't solve the problem.

bottom line, is it an inadequacy of the old sim,
a controller issue, pilot error, or possibly,
a combination of all these factors?

 

[Ivan]

Where Do I Start?

Hi Smilo,

We're pretty much in agreement regarding the distraction issues. I have had them since I was young also, but have also worked my way around them to get a few things accomplished. With this hobby, I choose NOT to work around them because it is just a hobby and my goal is to explore and learn. If somethinng releasable comes of it, great. If not, oh well....

Regarding the other subjects, I think you just opened a HUGE can of worms here....

First of all, Dunno about Jets. I don't think I have but a couple installed.
I trust none of the flight models except for perhaps the Learjet and I don't think that one will fly a knife edge safely.

The rest of this is my own opinions but with a little bit of background to back it up:
First of all, the controller is less important in my opinion.
It is really nice if it centers nicely and doesn't wobble around without user input, but REAL aircraft control columns don't have spring loaded centering. Centering is aerodynamic and weight balancing for the most part and it isn't all that precise.
If you are really curious, look for "Stick-Free" and "Stick-Fixed" stability in flight reports. What we have in the sims is only Stick-Fixed. There really isn't any feedback, even on the force-feedback joysticks because the folks coding the forces there generally have no clue what they are really doing.

Regarding aircraft stability, the best single engine fighters are either neutrally stable or barely stable on each axis.

An example of longitudinal instability is the Spitfire. In order to cure it, they enlarged the aerodynamic balance after about the Mk.V. It made the elevator much too sensitive but made the aircraft barely stable longitudinally. I have read some of the engineering docs on this subject and don't really understand HOW it worked, but obviously it did.

The FW 190A pilot report states that the aeroplane had ideal stability for a fighter with neutral lateral stability (and a very high roll rate), low stability longitudinally and good stability directionally.

The P-51 Bubble Top fighters were barely stable directionally to the point where you could bend the aeroplane if you applied a lot of rudder at high speed. The designers attempted to cure the issue first with a fin fillet on the lateer D and K models and eventually pretty much cured the problem with a taller fin and rudder on the H model.

If you load an aircraft with the CoG very far aft, longitudinal stability gets to be quite poor.
(You also get better performance though.)

Regarding Trim:
Most CFS aircraft have trim notches that are way too coarse. it allows for greater compensation for damage, but doesn't allow for very precise trim to allow the aeroplane to fly hands-off.
I generally start (when starting with the stock P-51D) by setting the Longitudinal (elevator) trim to about 0.400 instead of the stock value of 0.500. To be honest, this doesn't make all that much of a difference.
I then reset the Lateral and Directional trim down to 0.015 or so which is much less than the original.

Most real aircraft will have pretty large trim changes with changing weight conditions such as burning off fuel or with changing airspeeds. The Me 109E has its fuel tank behind the pilot and trim goes nose down pretty quick as fuel is burned off. The P-40 changed directional trim pretty seriously depending on airspeed. The Hellcat (and most other aircraft) changed longitudinal trim with airspeed.

With just about all my aircraft projects over the last few years, I test that the aircraft can be trimmed to hold a compass heading at fully (non-WEP) power at fairly low altitude (around 5000 feet) for at least a couple minutes. Longitudinal trim is generally set to be slightly nose up because I found that this changes a bit with altitude. I usually have a test sheet showing the settings I used and in very recent releases have put that information into the aircraft checklist.
The way I do this is to count trim notches and see what comes closest. If I get an "in-between" value, I adjust the trim notches so that I can hit the proper value.
This method works reliably but is incredibly tedious to do.
Often there are multiple combinations of Lateral and Directional trim that will maintain a compass heading.
It also needs redone if the level speed or weights & balance change.
I doubt that most developers take the time to check aircraft trim settings which is probably why you may find aircraft that won't trim to fly straight and level.

I usually set the CoG fairly far aft as mentioned earlier with the center of lift an inch or two ahead of the Center of Gravity. This also has a tendency to make the aircraft harder to trim longitudinally and often leads to a long period oscillation (phugoid). This is one part I am still experimenting with.

I believe the problem with trimming in the middle of a fight is that your speed and attitude changes are so quick that you never have a chance to let things setting down to see what the actual result was. Also, as stated earlier, trim usually varies with airspeed, so unless you maintain a constant airspeed, you should expect trim changes.

This is my current view of the world and easily subject to change as I learn more.
Hope this makes sense.
- Ivan.

 

[Ivan]

Ground Adjustable Trim

Most aircraft that I know of have Longitudinal (Elevator) trim that can be adjusted in flight

Many aircraft have Directional (Rudder) and Lateral (Aileron) trim that can only be adjusted on the ground.
Typically this is done by bending a small flexible tab that is attached to the trailing edge of the control surface.
Normally this would be done as part of production test flying and then adjusted as needed in service.

On aircraft with only ground adjustable trim, does it make sense to eliminate the trim settings?
I generally don't do that because I don't know of a way to "preset" trim in the AIR file.
Longitudinal trim is easy to preset.
Do any of you know of a way to adjust directional or lateral trim in the AIR file?

- Ivan.

 

[Ivan]

Here are a few screenshots from some experimentation with the P-38J by Eric Johnson.
The original AFX that I have does not have Propellers, Flaps, or a transparent Canopy.
I added those and a few other features to experiment with the best assembly method for a potential future project.

Eric Johnson did extremely well with the overall dimensions of his project. So far, I have found only one major dimensional issue and visually the issue is not obvious. The general shape is pretty good considering he was limited to 0.10 foot increments and used 8 sided cross sections.

- Ivan.

 

[smilo]

thanks for your replies on the subject of trim.
although, i am a "little" confused.
at least now, i know trimming issues
are not entirely pilot error.

in the first post, you talked about how you set up trim
when starting with a stock p-51 air file.

then, in the next post, you ask if anyone knows
how to "adjust directional or lateral trim in the AIR file?"
sorry, i don't know how to do that sort of thing,
i leave air files to the experts.

is it not possible to make an aircraft fly straight,
or at least straighter?
i maybe mistaken, probably am, but,
isn't the directional and lateral, for want of a better word, drifting
caused, for the most part, by the propeller P factor?
if so, couldn't one simulate directional ground trimming
by reducing the P factor in the air file?

you're right, this is a can o worms

replying to the p-38 post;

that's not a bad looking p-38.
it's amazing how a transparent canopy
and props improve the visual model.

to bad the cross sections are only 8 sided.
12 or, better yet, 16 sides would really smooth the curves.

as is, it would make a suitable replacement
for the stock p-38, especially if it's bleed free.

 

[Ivan]

Setting Up Aircraft Trim

Hi Smilo,

The first post was about using the P-51D AIR file was just describing how the size of each notch of trim adjustment was way too high to allow precise adjustment of Lateral and Directional Trim. One setting might be putting the aeroplane's left wing down while one notch to the right puts the other wing down. What you need is a half notch of trim or just smaller changes per notch.

It is sort of like the case a couple decades ago when a fellow decided to bring his Ruger Mini-14 to the 200 yard firing line during High Power (Service Rifle) practice. I was in the group pulling targets at the time. One shot would go left of the bull and the next would go right. I found out later that his sights were only capable of 2 MOA adjustments, so one click would move the aiming point 4 inches. The surprising thing was that he was so consistent with his aiming and even more surprising was that his rifle was so accurate.

The second post was about setting up default trim. By changing the angle of incidence of the stabiliser and a few other things, I can easily make the aeroplane be tail heavy or nose heavy without any user adjustments. The question is whether or not there is a way to make the aeroplane fly with the right wing down by default without changing other things that should not be changed. Is there a way to make the aeroplane yaw to the right without any user adjustments of trim?
There is often an aerodynamic twist built into an airframe to adjust for the asymmetrical airflow of the propeller.

There are a few other factors besides P-factor that cause a drift. P-factor for the most part only affects the aircraft on the ground because the direction of travel is not the same as the propeller axis. In the air there are a bunch of other factors that affect things. I don't know of a nice way of adjusting those factors without causing some other side effects.

The BV 141 was a pretty good illustration of one method of adjusting for the asymmetrical propeller effects. I am using pretty much the same idea on the flight model for the P-38J at the moment and it DOES work for the most part. Yet there are still some significant side effects.
With the P-38J, the engine thrust centerlines are about even vertically with the aircraft centerline (by my definition) and are offset 96 inches laterally from the centerline. I found that if I put the Port Engine out to -120 or -121 inches, most of the propeller direction effects are cancelled out pretty well. There is still a slight pull TO THE RIGHT on take-off and a slight drift to the left at high speed cruise, but it isn't hard to manage. I am still wondering if a vertical offset would do anything useful.

- Ivan.

 

[Ivan]

replying to the p-38 post;

that's not a bad looking p-38.
it's amazing how a transparent canopy
and props improve the visual model.

to bad the cross sections are only 8 sided.
12 or, better yet, 16 sides would really smooth the curves.

as is, it would make a suitable replacement
for the stock p-38, especially if it's bleed free.

Thanks Smilo.

Actually there are a lot of little changes in shapes that are not apparent from those screenshots. I have taken out a mess of bleeds so far and plan on fixing a bunch more. The things that are still bothering me are the coolant radiators on the booms and, the shape of the rudder, and some bleeds out the front that the wing-fuselage templates don't seem to be fixing.

I believe Eric Johnson really did very well with just 8 sided cross sections. I normally use 12 sided cross sections and run out of resources with a single engine fighter. I don't believe it is possible using AF99 to build anything signifcant using 16 sided cross sections.

My plan is actually NOT to release this one at all. I am taking way too many shortcuts that have my shop foreman cursing under his breath. notice the cockpit is still empty? Even my own pilot refuses to be seen flying it! I am messing with it to test assembly sequence and general construction techniques. It is also better than any other P-38 visual model that I have found for testing and building a flight model. (So, the pilot is still doing the test flying, but using his invisible man Halloween costume.)

I WILL send you a copy to use as a replacement for the stocker though my plans are not for public release.

Womble55,
Hopefully you are also following this thread because the screenshots attached are an example of the method I was proposing in an earlier discussion about Fowler Flaps. All of the Flap parts and Flap Well are set in the "Retracted" positiion in AF99. Aircraft Animator finds them and sets the axis of rotation as one might for a simple hinged Flap.
I then move the axis DOWN and AFT.
The amount Down sets how far BACK the deployed Flap will be.
The amount Aft is pretty much how far UP the deployed Flap will be.
It is interesting to mess with the pieces in Aircraft Animator.
For some reason Fowler_2 won't upload but you can still get the idea....

I also had a lot of muttering and cursing when I figured out that the outer Wing section where the outboard Flaps were mounted was actually added to the assembly with "Dihedral" selected. It makes the default Component not useful as a reference to use in building pieces. That is why I have never used it after seeing the result in a Kawanishi N1K2-J Shiden KAI that was my first AF99 attempt.

- Ivan.

 

[smilo]

yes, please.
i would welcome a copy of your upgraded EJ p-38j.
an upgraded afx would, also, be very cool.

from your past comments, i am aware of af99 resource limitations.
(i do remember some things)
my 12-16 side comment was merely a wish list.
for one to build with that kind of "accuracy", ad2k is a must.

i have uploaded the EJ p-38 afx into my ad2k install
and played with it a little.

i am tempted to pursue the project,
but, knowing my MO, i will, for now, refrain.
i have another long term project,
that i don't want to interrupt....again.


quick question, what does MOA mean?

 

[Ivan]

MOA is short for Minute of Angle. 60 Minutes in 1 Degree.
A Minute of Angle subtends approx 1.04 inches at 100 yards.
In the field of shooting, it is used as a measurement of accuracy to describe the angular dispersion of shots fired.
For shooting, 1 MOA is typically assumed to be 1 inch at 100 yards instead of 1.04 inch.

1 MOA for whatever reason (Probably because it is not that hard to achieve) is often used to describe an "Accurate" rifle.
The idea is that the two shots are measured (at the center of the bullet hole) and the number is recorded.
The problem is that there isn't any great standard as to how many shots are fired which makes comparisons quite difficult.
Often Hunting rifles fire 3 shot groups for record because they tend to have lighter weight barrels which heat up quite fast with firing and the point of impact may move when the barrel is hot.
Service Rifle (a competition category using US Military rifles) typically describes 10 shot groups.

I typically shot 5 shot groups and often superimpose the resulting groups to get an impression of what a 10 shot group would have been. In general, this SHOULD give a slightly worse result than a single 10 shot group would have because the conditions may have changed slightly between groups.

A typical US Military rifle (M1 Garand and later) has adjustments that move the Point of Impact 1 inch per "click". A service rifle with competion sights typically has sights that move the POI 1/2 inch per click. I don't shoot well enough without a telescope to take advantage of that kind of precision.
That was the surprising part of this story. They fellow with the Mini-14 was holding a group that was about as well as the rifle could achieve in my experience. His sights did not have fine enough adjustments to let him center the group on the target.

- Ivan.

 

[womble55]

That brings back a few memories.
When I was shooting full bore in the Air Cadets, we used service .303 Lee Enfields and fired a good 100 rounds per rifle in a day.
They were just as accurate in the afternoon as they were in the morning and our marksmanship was still 2.5 inch at 300 yds, not bad for 14 to 17 year olds.
All this with a blade and aperture sights.
We once had a Bren, 30 cadets + 28 rounds apiece and the barrel soon heated up. Solved by unclipping the barrel and dropping it into a bucket of water while the spare barrel was clipped on.
I tried but could not get on with the 7.62 SLR, it didn't seem to have the build quality that the Lee Enfield had, even though the round it used had a higher muzzle velocity.