Acceleration comparisons

[horseback]

Originally Posted by JG27CaptStubing

Interesting to see what TD did to some of the FWs... No wonder you can easily get caught with your pants done

To be fair, this set of tests were done at just about the worst possible height for the FW; 3000m is quite close to the alt at which its supercharger moves from low to high blower, so the engine is not at its best here. I've just started doing the sea level (100m) tests, which should be more flattering to the Wurger.

cheers

horseback

[IceFire]

Probably a good idea to point out that context is extremely important. As these acceleration tests were all done at the same altitude. Some aircraft will be better and others worse at this altitude... nothing stays the same across the range. It's not one acceleration level that extends from 0 to 10,000 meters.

You have to know your plane. I know that the Tempest V between 3000 and 4000 meters is less capable against the FW190D-9 (which I consider to be its chief rival) as the stage 1 supercharger starts to run out of steam and you're just about to switch to the stage 2. Depending on the D-9 model year... this is the worst altitude to fight at. Take it lower or higher and the Tempest is faster and more able. Context!

[MaxGunz]

I would have problems with a plane that didn't get noticeably more lift for a 6 mph speed increase.

Check around, there are 10-turn and IIRC 20-turn pots in various ranges.

Less fine-adjusting but oh so desirable, check the unit price:
http://www.futurlec.com/PotSliding.shtml
There is a shipping charge but that can be as low as $4 to $5.
http://www.futurlec.com/Delivery.shtml
The package comes from Hong Kong so expect about 2-3 weeks wait.

Something else you could do is put a 10k or smaller pot in series with a 100k pot (or a 1k and 10k) and have both coarse and fine adjustment knobs on the same circuit.

[horseback]

Originally Posted by MaxGunz

I would have problems with a plane that didn't get noticeably more lift for a 6 mph speed increase.

That might be appropriate for a general aviation private plane with a maximum speed of 170 knots, but for a fighter capable of advanced acrobatics with an engine spinning twice as many blades three times as long (& at least five times as heavy) and hosting five to ten times as many horses?

cheers

horseback

[MaxGunz]

Originally Posted by horseback

That might be appropriate for a general aviation private plane with a maximum speed of 170 knots, but for a fighter capable of advanced acrobatics with an engine spinning twice as many blades three times as long (& at least five times as heavy) and hosting five to ten times as many horses?

cheers

horseback

Still the same only more so. Lift is by speed squared, AOA and constant factors aspect ratio and wing area. As speed increases, AOA must decrease to keep level flight.

However the tailplane part of the airplane balancing act also has a lift and it's own AOI relative to the main wings which must affect need for trim.

If the P-38 tailplane actually forces the nose down more with increasing speed then the COL moving back as critical mach is approached would turn that into a bad thing... which may or may not be part of the P-38 death dive phenomenon.

I would be very careful pulling text out of books and treating everything with a key word as if on an equal basis with every other. Those comments come from people with different backgrounds and if filtered through yet another party with another background and then evaluated by a reader with a completely different background it's all too easy to end up in a subjective mess especially if the last person tries to use unqualified statements as hard references.

Ie, stick with controlled test data or have your experts on hand to qualify and explain just what they mean.
Don't play at guessing to arrive at your own conclusions even when you have some facts to go with the guessing. I have facts about lift and balance but only questions and not conclusions about the FM to make from those.

If the P-38 didn't need trim then why is it there? Did that quote about not needing trim with power of speed changes apply to small changes or to the full safe operating range? We all know that at some speeds that use of trim and slowing down did become needed, don't we?

BTW, what do you think of using 2 pots for coarse and fine adjustment? I've never seen such but series resistances do add.

[RPS69]

There are commercial potentiometers, that allow you to turn around 10 times, and have a numerical track of your position.
They are very precise, and can move fast if well kept. Still, don't play unneadlessly with them, because they get noisy after so many changes. Still, they may work fine for around 10 years on an everyday use.

http://www.schukat.com/schukat/schuk...8&kb=DIAL15111

That was the first example I stumbled upon. Don't know how good they are though...

Horseback

Nice observations and I would agree with your assessment. You note the rudder boost tab reversal mod (from boost tab to anti-boost tab) on the P-51 and its effect on rudder use but you didn't note the same change was made to the long-tail P-40's rudder with the same result. Something else that I have difficulty with is all Mustangs seem to be able to snap the wings off in a dive with the same ease when there should be a very noticeable difference between elevator bob weight modded and un-modded aircraft. (Elevator bob weight mods were also installed on Spits starting with mid Vb.)

[MaxGunz]

Originally Posted by RPS69

There are commercial potentiometers, that allow you to turn around 10 times, and have a numerical track of your position.
They are very precise, and can move fast if well kept. Still, don't play unneadlessly with them, because they get noisy after so many changes. Still, they may work fine for around 10 years on an everyday use.

http://www.schukat.com/schukat/schuk...8&kb=DIAL15111

That was the first example I stumbled upon. Don't know how good they are though...

There's 20 turn pots too, made with high precision for test instruments. They're not cheap. Check Mouser, Digikey or some other electronics house for listings. Sometimes you can find the parts cheaper, just make sure of manufacturer and check the datasheet.

Here's the thing about multi-turn pots: how do you keep track of how many turns you have made? A single turn pot or linear slider is so much simpler.

[SadoMarxist]

As far as the acceleration comparisons go, there was a nutter on WoP forums a few years ago who claimed that the ability of an aircraft to accelerate can be expressed and evaluated by something called Specific Excess Power (Ps). Furthermore, said person was audacious enough to claim that the information necessary to compare the acceleration performance of one airplane relative to another is contained within the IL- 2 Compare diagrams. I can't find the thread now, but never mind, it was long and boring anyway. However, I was able to find a document which explains Ps:

http://www.aviation.org.uk/docs/flig...-FTM108/c5.pdf

Regarding the trim characteristics of a certain airplane, this will have to do with stability and control. While contributing factors of the control surfaces can be modeled, the peculiarities of inception mechanisms (sticks, yokes, pedals, hydraulic augmentators, balance weights,... ) scarcely can be. Luckily, one can assign trim to axis and then use IL- 2 Joy proggie to adjust the response curve of the trimmer to one's liking .

[horseback]

Regarding the trim characteristics of a certain airplane, this will have to do with stability and control. While contributing factors of the control surfaces can be modeled, the peculiarities of inception mechanisms (sticks, yokes, pedals, hydraulic augmentators, balance weights,... ) scarcely can be. Luckily, one can assign trim to axis and than use IL- 2 Joy proggie to adjust the response curve of the trimmer to one's liking .

While I'm all for maths and technobabble in their proper places, I feel that in a forum like this, they usually do far more to obscure than they do to explain.

As I've pointed out, the trim issue seems to be confined to a relatively small group of aircraft, and I've done extensive experimenting over the eleven years I've been playing this game and its predecessor with trimming methods and controllers. Button trim usually is the more accurate of the two, since it is input in quite tiny increments (about 160 clicks from one extreme to the other), and on most aircraft it is more than adequate, in the sense that you can get to a 'zone' where one more click up or down makes no discernible difference. However, on some aircraft the transition from one click down or one click up always seems to be excessive at any throttle/pp setting; you will either be climbing or losing altitude, in a slight skid or slide or rolling to one side or the other unless you hold your stick absolutely rock steady precisely at angle X/Y. On these same aircraft, I also notice that you need to trim precisely for very small changes in speed and power, or the penalties in performance and speed loss can be severe.

When it consistently happens with aircraft I know were easily trimmed for hands off or at least reasonably stable flight, I have to wonder why, when so many other aircraft described by contemporary pilots act as described in the game (or considerably better). If the programmers can simulate the trimming characteristics of plane A (the P-40 series) from records 70 years old, then how is it that planes B, C and D need to be adjusted at least 150% more often than the acknowledged worst trimming aircraft in the US inventory?

cheers

horseback