[horseback]

Originally Posted by MaxGunz

I can get behind what you say but not how you say it. I wonder just what you expect when I've read the same material and don't come away with descriptions like yours.

In Bud Anderson's account the need to change trim was no surprise to him but as stated something you just do from regular practice, like tuning a car radio in those same times. But then from training on he was taking planes across the speed range quickly regularly.

Anderson, like all the pilots of that era did have a lot of practice at trim adjustment, but he also had the 'feel' that the virtual pilot is denied, and as I pointed out, the account that everyone loves to quote covers one fight at between 25 and 30 thousand feet; at that altitude, the IAS is relatively low, especially as both combatants were trying to extend their zoom climbs (and oddly enough, that is where the comment about constantly trimming comes up). As I understand it, flight performance is consistent with indicated airspeed regardless of altitude, and at low IAS, the rudder needs a lot of adjustment, but not the elevators or the ailerons to any great degree.

At low speed you don't get enough air over the elevator and ailerons to make high stick forces but propwash on the tail will be high in proportion to prop speed and power and worse on the ground when the tail is down. At cruise the plane should be closest to trim neutral by design. Do you find any accounts for any plane of the stick being "set in cement" at low speed? At high speed, yes.

"At cruise the aircraft should be closest to trim neutral by design." What happens when you have an air start with the Mustang in-game? Your starting speed is what, around 300kph/185 mph? The Mustang (and almost every other late-war US fighter except the Hellcat) drops like a rock; you can lose 1,500 ft before you recover, even with pushing the throttle and prop pitch well forward and mashing in nose up trim while pulling back on the stick and trying to avoid a stall. Then, once you get leveled, you're fighting a climb because there is no discernible balance or transition point. You simply start fighting your stick in the other direction and mashing in nose down trim. Elevator trim on the Mustang should be minimal, not a constant battle with the joystick's springs, and the difference between 185 mph indicated and the normal cruise speed of around 240 mph IAS (2700 rpm and about 35-40" manifold pressure in the DCS Mustang), and the rudder shouldn't need a couple of clicks (1/80th of the trim range) for every 10kph/6mph in speed variation--as noted before in previous posts, the P-40 was thought extremely trim hungry because it needed a rudder trim adjust for every 16kph/10mph of speed variation.

Check any reliable source, and the P-40 would be rated well below any model of the P-51 in the matter of trimmability or trim demands. Even with the recent changes to the FM, the Il-2 '46 Warhawk is still not the trim hog the Il-2 '46 Mustang is; the Warhawk is still fairly predictable and quite intuitive, and a far better gun platform as a result.

Trim is normal for most planes for not just speed change but engine setting change. When you change the propwash spiral you need to adjust the rudder to match though it's easily enough done first and sometimes (like the 109) only with the feet.

Here, I agree with you in principle, but the degree of change required to minimize stick force seems excessive to me; it's 160 clicks of rudder or elevator trim from one extreme to the other, and you can feel the difference of one click (and usually, you find yourself giving it three clicks in one direction and then one click back on the elevators and then you adjust the rudder trim in approximately the same way, and then if your nose isn't perfectly level, you're either speeding up or slowing down a little bit and the trim has to be adjusted again). Elevator-elevator- elevator; UN-elevator -rudder-rudder-Unrudder--oops--UN-elevator-UN-elevator, rudder. Lather, rinse, repeat. In most cases of Il-2 FMS I believe that the elevator trim is much too excessive--on average, I think that we are applying trim at least two to four times as often as we should have to in proportion to rudder trim.

This is where I read/listen close to accounts, what are the conditions and are there any clues about all those things that don't get written or mentioned which is why Bud's statement starting off with how trim is one of those things and why really sticks out. It doesn't mean trim every second but in maneuvering combat it happened often and for an accomplished pilot was no big deal, something done without thought.

Still the IL-2 P-51 is trim needy as are most all of the models and in IL-2 it's not simple at all to get right (in fact it's a PITA) nor do we players have the feel of G's and slip side-pull and changing stick force that let these things become automatic. It's a pain no matter what plane, some degree of that plays a part in P-51's so how do you say how much is the game itself and how much the model? Oh, by comparing to enemy planes!

On the contrary, I have always compared the Mustang FM to other US fighters, and there appears to be a clear historical hierarchy that can be established from worst to best. The P-38 was the least trim needy, closely followed by the Mustang, and the P-40 was far and away the worst with most of the rest grouped somewhere close to the middle--and this may be why Oleg was so sure that US fighters 'got worser' as they were developed--it is generally agreed that the P-40's trim issues became more pronounced with every new model and the Soviets received almost every Warhawk variant via Lend Lease. Since 1C appears to have used TsAGI wartime testing as their primary source of data for their FMs well into the life of the sim, and TsAGI had little in the way of first hand data on the late war US fighters (particularly the Naval fighters), I think that some extrapolation went on, and that there was a certain prejudice at work. We had several instances of US sources of official documentation being rejected by 1C because they were 'propaganda'.
If we could assume that the original game and Forgotten Battles/Pacific Fighters had the P-39 and the P-40 series properly 'slotted' in terms of capabilities and firepower versus the Soviet and German aircraft that the Soviets exhaustively tested during and after the war (and players' results in the game seemed to reflect that slotting), we should expect that the superior late war aircraft should be superior to the P-39 and P-40 in most, if not all respects.

Instead, there's this insistence that more advanced means more complicated and harder means more realistic.

How many degrees is elevator trim? And how many clicks is the total range? A couple of clicks is barely anything!

As I said, I have checked on several aircraft, and it's the same for all; 80 button clicks from neutral to full trim in each direction, or 160 clicks from one extreme to the other. You're right; a couple of clicks is barely anything. Or at least it should be. Amazingly, much of the time one click is too little and two clicks is excessive; you still find yourself fighting the stick or making constant micro corrections when you should be able to just hold the stick steady and maintain straight and level flight once you've stopped accelerating and keep the throttle and prop pitch constant on aircraft with an established reputation for stability.

If something needs to be fixed it also has to determined how much fix and not enter magic wand land.

If something needs to be fixed, the responsible parties first have to agree that it should be fixed; a partly nerfed Mustang seems to have a lot of supporters in the Il-2 '46 community, not least because of some fashionable historical revisionism and cherry picking.

BTW, plural orders of magnitude more is 100x, 1000x, 10000x, not 2x or 3x more. Please, significant is 10%, 1/10th more, and 50% more or less is extremely remarkable where 25% alone is remarkable. Orders of magnitude is not a statement to be thrown around. It has numbers attached that beg qualification despite how often number-challenged people misuse the term. Cargo capacity of a ship tends to be orders of magnitude more than that of a truck. A modern jet might fly a single order of magnitude faster than a Piper Cub. Changing trim 100x more than what Bud described you mean never removing a hand from the trim wheel.

Depends on your background; you appear to be using an engineering standard as in ten to the x power. I might be overstating my case, but I tend to think in terms of squares and cubes as orders of magnitude. When you have 160 squared (160 rudder X 160 elevator plus maybe a little aileron here and there) shades of trim adjustment and you have to use every one of those steps in some part of the flight regime (plus several in between) for an aircraft that historically is described as needing very small amounts of trim (and mostly rudder trim), that's reasonably close to an order of magnitude in my book.

I have to be a lot more ham-handed than usual to get The Ball to misbehave anything like what you describe.

Maybe you're not chasing ai Me 110s that will twitch out of your sights just as you get within effective gun range; the moment I correct to get the guns back on the target, the ball under the sight is squirting all the way to one side or the other; I realized a while back that most of the time it isn't remotely accurate unless you've been flying straight and level for a minute or so. Of course, I probably drink a lot more coffee than you do, but it is a lot more 'active' than most other aircraft's T&Bs in response to minor inputs. As I said, the cockpit displays in the Japanese fighters are far more stable, accurate and timely, but they are based on what someone thinks they should be like (and that someone probably owns a Honda or a Toyota), because they have next to no documentation on them, and they cannot imagine a time when good quality in a Japanese product would be a surprise to anyone who encountered it. The German instruments are slower and less accurate than the Japanese, for Pete's sake. That is just upside down and backwards from the historical record.

I understand that the instruments in many aircraft are modeled as illegible or slow & inaccurate, but this is a flight simulation without 360 degree field of view or moving cockpit; we don't get the cues that the real pilots got, and ones we do get are slow or false in selected cases to a greater or lesser degree. I have argued in other threads on this forum that the flight instruments depicted in the game cockpits should at least meet a single standard of accuracy and clarity, the clearer and more accurate the better.

Find the date that Zeno's Flight Characteristics film was made. Clues: it's a P-51B being introduced as new. There is NO mention of the fuselage tank and CoG caveats we see mentioned later as you would expect if there was a fuselage tank and "these reports were part of the training regimen" which BTW that film was.
My conclusion is that at that time there was no concern because there was no fuselage tank to be concerned about. Still, once it is EMPTY the result *might* be the same or close to the film.

Let's start with the film; at 2:20 we briefly see an Olive Drab D model without a fin fillet, so it's safe to say that the film probably is late '43 at the earliest (first production 'B' models came off the line in late May or early June of that year, and the cutdown fuselage and bubbletop were in the works before New Year's Day 1944).

At 3:20, Mr Deitz (the bald guy) says "And we're putting an 85 gallon tank in the fuselage, back of the pilot's seat." This means that it's a done deal, the tests were passed, the concept works and we're either in production or about to enter it. No earlier than August of '43 for that portion of the script; the wording is vague and he could mean that they were already doing it at that time or that they were about to.

Again, it's an overload tank, and I agree that the aircraft in the film probably didn't have it (no white cross near the data panel is visible, but the film could have been made before it became common practice). As mentioned in the film, the heavier Merlin 60 series moved the CG a bit forward from the P-51A, and I am aware that the newer radios were more compact and lighter than those in the earlier models, so adding the extra bracing, fittings and the tank probably put the CG much nearer to where it was intended. Since the consensus is that once the tank had less than 45 gallons in it, the aircraft would behave normally, the extra 235 to 260 lbs of weight from that first forty gallons of fuel was the critical part that hosed the CoG up. America's Hundred-Thousand says that as a class, the Merlin Mustangs needed a bit more trim than the Allison powered models, but that they were still very good in that regard. We could argue that a Merlin Mustang with the empty tank was closer to the ideal CG of the P-51A than the first P-51Bs without it.

Now regarding trim, at 13:40 in the movie the Major in the tower asks the pilot "How is she on directional trim changes as speed and horsepower are varied?"

Response:"The aircraft is stable at all normal loadings but the directional trim changes at low speeds as speed and horsepower is varied. However, the rudder tab corrects this with just a slight adjustment and it should be used as necessary. Normally, there is no trouble as the plane is naturally stable."

--At this point Deitz breaks in and says "That means that the P-51B will remain at any altitude without adjusting the trim tabs."

The Colonel responds "Less work for the pilot."

The trimming section on the P-51 in Francis Dean's America's Hundred-Thousand is transcribed in full below:

"ALLISON powered Mustangs were particularly notable for lack of required trim changes. Power or flap setting changes gave only small trim variations, and the same was true of gear retraction. The changes in tab settings for climbing and diving were negligible. Tab controls were sensitive and had to be used carefully.

Trimmability was also quite good in MERLIN Mustangs, and tabs were sensitive. In these versions directional trim changed more with speed and power changes. When the rudder trim system was changed and rigged as an anti-balance tab to give opposite boost, a resulting disadvantage was more tab was required to trim the aircraft from a climb into a dive.

Along with trimming the airplane for longer term steady flight conditions, some pilots trimmed their aircraft almost continuously to wash out any high stick or pedal force during maneuvering in combat."

What I take from the movie and the testimony from Dean (and a good forty or fifty other pilots' accounts and personal testimony that I have read or heard over the last 40-50 years) is that the original P-51 was very well behaved in flight, and that very little trim was necessary to maintain straight and level flight throughout the speed range, and the Merlin Mustangs were also very good. In fact, so little adjustment was needed that pilots had to be warned that the tabs were sensitive & had to be applied carefully.

We're not talking about a Cessna 172 here, with 160hp and a full flight speed range of 60-160mph--we are talking about an aircraft that stalls around 95mph and achieves a level indicated speed of around 380 mph at 5000 ft (and was controllable at much higher speeds).

It was designed for a much greater degree of stability over a much greater range of speeds; if it weren't fairly stable over that range of speeds, particularly over the subset range of speeds normally attained in combat, it would have been nearly useless as a gun platform, which is what so many would-be users of the Il-2 Sturmovik '46 Mustangs are put off by, because it is completely unintuitive and you have to just keep at it until you learn to fly it by rote and muscle memory and ignore your instruments at critical moments.

We -KNOW- that with the tank more than half full that the change was big not only from the manual but pilot accounts such as Clostermann's.

Please don't quote Clostermann to me; the guy could tell a good story, but his 'official' victory total had increased significantly over his RAF credits by the time he left this world, so I tend to discount his authority in much the same way as I do with Martin Caiden. I'm not aware that he flew the Mustang in operations (I believe he was a Spitfire and Tempest guy), so I have to wonder what the hell he would know about the subject beyond hearsay.

I would take his word on what constituted a good pastry, though.

I know you have a passion for the subject but it keeps going to the fundamentalist religion level. If you get a blackboard, you could approach the Beck level from where you may never come back to sane reasoning and start using first letters in arranged words to make your own truth. Did you ever know Von Helton?

I have no idea who you are referring to. Are those the voices in your head?

cheers

horseback