Author Topic: Corsairs..? (Read 4184 times)

Krusty · « **Reply #45 on:** March 03, 2008, 11:02:59 AM »

Urchin, at low speeds sometimes you can't even roll right with a good amount of rudder! I've noticed that when taking off at slow speeds in 109g6s. At high alt, including 109G14s, you use WEP and the aileron trim isn't enough to keep you on course. You actually start turning left on the compass heading, and have to adjust course repeatedly.

So we know the torque is there in general.

Also, the airframes on the F4u and P-47 are so different that I don't think they'd have the same departure characteristics. The 47 has a larger wing without the gull dip, a larger inverted-egg-shaped fuselage cross section, and a larger vertical tail, than the compact tube-like f4u. I mean that, while the engine may produce the same amount of torque, the rest of the p-47 may be better at overcoming this. Especially if the tail is further out and can act as a greater lever. One thing that always surprises me is the compactness of the F4u airframe.

P.S.

Quote

Originally posted by Saxman
Krusty,

As I pointed out before, in the video the F4U reacted more violently in the power-off/full flaps and power-on/partial flaps stalls than it did power-on full flaps.

In the power-on full-flap stall, the aircraft's nose tucked and it crabbed off to the left but did NOT exhibit the same immediate snap-over to inverted as in the other two power/flap configurations.

It didn't just crab over. It tucked under somewhat sharply in what looked like was going to be a flat spin. We're not just talking nose drop, it drop and spiraled inward, and you just don't see that in this game.

Come to think of it, I recall I *USED* to like the P-51B because the P-51D in-game had more of a tendency to spin into the left wing. The added dorsal surface on the -B meant this happened less. I haven't had that happen since the airflow recode. I think it's not only on the F4u that this is happening, now that I think about it.

SgtPappy · « **Reply #46 on:** March 03, 2008, 04:07:09 PM »

It seems to be like this on most aircraft. The only time I'll come close to snapping over is when I neutralize all trim and full-power take-off.

The torque is likely an issue. For example, under many quoted sources (which I am too lazy to find right now), the Spitfire XIV is supposedly very difficult to handle at full throttle on take-off and not even FULL rudder can compensate. In the game, you can trim yourself neutral, firewall the throttle and you wont even have to use more than 50% rudder left to make the plane stay stable.

Krusty · « **Reply #47 on:** March 03, 2008, 04:11:54 PM »

Yes, I'd heard that too.

I wonder if in AH1, the system worked "like that" and they set torque levels at "N" to get the desired results under that system. Now in AH2, the system works "like this" and the setting "N" doesn't produce the same result. To get the same end result, the torque needs to be set to "N * 1.5" (just using a random number for example).

Serenity · « **Reply #48 on:** March 03, 2008, 05:56:47 PM »

Quote

Originally posted by Saxman
On the OTHER hand, Widewing's article suggests torque roll in the F4U was no more of an issue than any other high-powered fighter, and that in spite of the sudden wing drop in a stall there was plenty of warning about 7mph before she snapped over.

The video I mentioned before specifically stated that the F4U gave NO warning before stalls. I dont know much about these aircraft, but considering this was published as a training film by the war department, during the war, specifically about the F-4U, I would think they have an idea what they are talking about.

Serenity · « **Reply #49 on:** March 03, 2008, 05:58:24 PM »

Quote

Originally posted by SgtPappy
For example, under many quoted sources (which I am too lazy to find right now), the Spitfire XIV is supposedly very difficult to handle at full throttle on take-off and not even FULL rudder can compensate.

In the book Fly For Your Life, the story of RAF pilot Robert Stanford Tuck, Tuck is quoted as saying that. Thats one source at least...

Stoney · « **Reply #50 on:** March 03, 2008, 07:59:31 PM »

Quote

Originally posted by Arlo
But does this put you in the "why not tweak the torque model" crowd or not? Or do you think that's opening a possible period of mass dissatisfaction (can-o-worms) when such coding presents the inevitable teething issues across the board, affecting practically everyone's favorite ride in a negative way that requires tweaking virtual pilot technique? I'm leaning pro-torque but I can be convinced otherwise if there's an decent argument standing in my way (and there may well be).

Personally, I don't know. I think that HTC has done a good bit of "dumbing down" some of the more germane (if that's an appropriate word) parts of flight for the cause of playability and fun. I'm a real pilot, and if I need to get a dose of realism, I'll hop in an actual cockpit in order to satisfy my "engine management" fetish, for example. So, if the torque is porked, that's fine with me, as long as all planes possess the same relative differences in actual torque (i.e. everything is modelled at 75% of actual, for example). On the other hand, I'm not sure it is actually porked.

What I would like to see, and its the point I continually try to make here, is someone with an honest gripe about how things are modelled, is to do the research and the work to support their argument. There is a mountain of information available to the "Everyman" aerodynamicist that explains how all of these forces interact on aircraft. Given the fact that we know (from the picture of the F4U in a climb) that things like pounds of lift, coefficients of drag, and pitching moments are computed by the game (which has to use math to output aerodynamic forces on the plane), there must be some sort of relationship between whats going on in-game, and the formulas displayed in most aerodynamics textbooks/resources. Certainly Dale didn't "invent" all of the formulas that translate all that stuff into the code that affects the 3D model we see represented in game.

Saxman · « **Reply #51 on:** March 03, 2008, 08:50:28 PM »

Krusty and Serenity,

A point of order is that the F4U used in the training video is a -1 birdcage, lacking the stall strip in the starboard wing. While it wasn't an absolute solution to the departure issue, it was clearly a significant enough improvement to warrant inclusion in every mark since. So the behavior in the video isn't perfectly indicative of stall behavior across the entire series.

Krusty · « **Reply #52 on:** March 03, 2008, 09:40:05 PM »

Even the -1 birdcage in-game doesn't act like that film, though.

I haven't spun out at low speed in a long time in anything other than a ta152 -- and when that happens its instant tail slide, no spin, no recovery.

Only time I've come near to spinning is extreme hammerhead-type manuvers, and coming back down at the top.

Serenity · « **Reply #53 on:** March 04, 2008, 12:51:54 AM »

Quote

Originally posted by Saxman
Krusty and Serenity,

A point of order is that the F4U used in the training video is a -1 birdcage, lacking the stall strip in the starboard wing. While it wasn't an absolute solution to the departure issue, it was clearly a significant enough improvement to warrant inclusion in every mark since. So the behavior in the video isn't perfectly indicative of stall behavior across the entire series.

However this film has taken into account newer models of F4Us as far as cockpit layout, so I would think that they would also take into account the characteristics. Perhaps if there was a truly significant difference in stall due to that strip, they would have mentioned it.

Stoney · « **Reply #54 on:** March 04, 2008, 01:28:28 AM »

Quote

Originally posted by Krusty
Also, the airframes on the F4u and P-47 are so different that I don't think they'd have the same departure characteristics...

I wasn't talking about departure. That's more a term of stalling behavior. I was talking about torque effect.

...The 47 has a larger wing without the gull dip...

Corsair has 14 square feet more wing area than the Jug at 314 ft^2 vs. 300 ft^2. I could not find the aileron area on the Hog to compare.

...and a larger vertical tail, than the compact tube-like f4u. I mean that, while the engine may produce the same amount of torque, the rest of the p-47 may be better at overcoming this. Especially if the tail is further out and can act as a greater lever. One thing that always surprises me is the compactness of the F4u airframe.

If you were talking about which one might be more pitch/yaw stable, I'd agree. The P-47 was 3 feet longer than the Hog, plus the fact that the Vertical stab on the Hog was set in front of the horiz stab means a much shorter vertical tail arm on the Hog. Of course, Vought made up for it by having a rudder almost twice the size of the Jug.

But, the point is that the vertical stab has less to do with controlling the roll moment (of which torque would be a part) of the aircraft than the ailerons--much less. So, if there's an appreciable difference, it would be have to be in aileron area.

So, again, why would torque act more against the Corsair than the Jug, under the same power?

Saxman · « **Reply #55 on:** March 04, 2008, 07:16:27 AM »

Serenity,

If the stall strip made no appreciable difference it wouldn't have been there.

And I don't remember the film saying anything about changes in cockpit layout between the birdcage and later marks.

Krusty · « **Reply #56 on:** March 04, 2008, 09:37:07 AM »

Stoney: The vertical tail's reason for being is to counter torque. On the 109 models they added a taller tail as the engine power increased, because the smaller tails could not counter the torque. On the bubble top P-51s and P-47s, they lost dorsal area and couldn't counter as much torque, leading to fillets being installed.

Stoney · « **Reply #57 on:** March 04, 2008, 10:11:09 AM »

Quote

Originally posted by Krusty
Stoney: The vertical tail's reason for being is to counter torque.

Oh boy...

Krusty · « **Reply #58 on:** March 04, 2008, 10:17:12 AM »

Okay, let me rephrase that

"One of the more important reasons there is a vertical stab is..."

EDIT: Even you can't deny that's its primary role. If a plane has too much torque they add vertical surface area to bite into the airflow and counteract this.

Old Sport · « **Reply #59 on:** March 04, 2008, 12:58:43 PM »

Quote

Originally posted by SgtPappy
Thanks, Old Sport. It's always good to have new explanations like that. But sorry, I don't really understand that bracketed diagram of cross sections.

Okay Sgt Pappy, maybe these photos will help a little more.

Gravity pulls straight down, vertically. Lift pushes straight up, vertically against it.

So the cross-sectional shape of the wing that produces the lift, including the flaps, has to be measured vertically, not at an angle.

The F4U's bent wing can trick us into looking at the length of the deployed flaps from an angle (the bottom view on the left), when we should be looking at them vertically (bottom view on the right). You can see just by a rough "eyeball" that the difference may be around 10 percent. I'd say that is not insignificant.

All the best