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"Rule writing. Turning radius at speed" Topic


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World War Two in the Air

354 hits since 7 Oct 2019
©1994-2019 Bill Armintrout
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Last Hussar07 Oct 2019 2:17 p.m. PST

Do turning radius' increase with speed?

In my rules a plane move up to 4 times (impulses) per phase, depending on speed, but may only make one turn during any phase (this 2nd impulse if more than 1)

Is this reasonable?

Personal logo Herkybird Supporting Member of TMP07 Oct 2019 3:28 p.m. PST

I think its a given that the faster a plane is going the wider the turning circle.

HMS Exeter07 Oct 2019 3:32 p.m. PST

I don't mean to leave a floater in your pool, but trying to write air to air combat rules has to be one of the most wickedly complex things you could imagine trying.

Turning radius does vary with speed. It also varies by aircraft type, even if moving at the same speed, and it varies based on altitude. Don't even think about the radius of a climbing or diving turn.

Personally, I am a huge fan of house rules. They tend to be simple and fun. But, to speak the truth and shame the devil, this is one realm of combat I'd be more focused on picking an established rules set, and kitbashing as needed to suit your preferences.

I hear good things about Check Your Six. You could do worse than the Blue Sky series from Stanoch. There must be others.

I commend your initiative, but you're gonna drive yourself bonkers, and the excitement of trying will corrode pretty quickly.

Good hunting.

Last Hussar07 Oct 2019 4:59 p.m. PST

I have a set of rules that are perfectly good. I was just thinking about them, making it tighter and easier to play without losing what makes them what they are.

Basically its reducing bookkeeping while keeping the mechanisms. While I was simplifying movement (without dumbing down) I suddenly wondered does it actually work like we expected it to, or is the obvious answer wrong.

irishserb07 Oct 2019 6:15 p.m. PST

Just a shot in the dark here, not knowing the rules, but maybe Impose a number of straight moves in between impulses to reflect the larger radius, as speed is increased.

HMS Exeter07 Oct 2019 6:22 p.m. PST

The obvious answer is right. It works the same with cars and ships and aircraft. The faster you go, the wider the turn. There are exceptions. The CSS Virginia turned like a brick at every speed.

Thresher01 Supporting Member of TMP07 Oct 2019 8:33 p.m. PST

Yes, and the increase is not linear.

Once set in a turn, supposedly, all aircraft turn at the same rate, for a set speed and number of "Gs" being pulled, assuming the aircraft have the energy to maintain that (that isn't always a given).

Getting rolled/banked is where the differences come about between various aircraft.

If you really want to get into this, you might consider buying an aeronautics manual. I have one from the USN, from back in the day. It provides a graph showing the turning radii for various G-Force levels, at different speeds. Very educational, to the point of making your head hurt, unless you are a walking computer.

emckinney07 Oct 2019 9:52 p.m. PST

"Do turning radius' increase with speed?"

No. An aircraft near its stall speed can barely turn. As the aircraft gets faster, it's able to pull more and more Gs without stalling. At some point, it reaches its safe G limit, or the pilot risks blacking out, or the control surfaces "reverse" due to aeroelasticity (before the introduction of all-moving elevators, etc.).

The most important thing is the difference between rate of turn and turning radius.

Rate of turn is how many degrees you turn per second.

Turning radius is how far it is across a circle that you would make if you flew at constant speed and Gs.

Your highest rate of turn and your tightest turning radius occur at different speeds (often extremely different speeds). Highest rate of turn is the aircraft's "corner speed" or "maneuvering speed."

It's a bit complicated, but once you understand the basics, you see fighter performance in a whole new light. The interaction on all these factors is also what makes games like J.D. Webster's Fighting Wings series and Tony Valle's Birds of Prey so fascinating and deep. The question, "Which was more maneuverable, the 109 or the Spitfire?" stops being important and the question, "How do make the most of my aircraft's strengths and weaknesses?" gives the player real decisions to make.

Wikipedia on be maneuvering speeds: link

Wolfhag08 Oct 2019 10:01 a.m. PST

emckinney,
Then there is the instantaneous turn/G's a plane can pull and the sustained rate/excess power. You also need to take into account the banking performance/roll rate. Planes with good sustained turning radius do not necessarily have the best roll rates. The lighter they get burning off fuel the better their performance too.

A plane that is up against a better turning opponent can change directions more quickly if he has a better roll rate than his opponent and makes it difficult to line up a shot. Roll rates can also depend on speed and hydraulic assist. Some planes, like the Zero, had control difficulties at high speeds and suffered in maneuverability.

Spitfires suffered from aileron reversal at high speeds because of the single spar wing and elliptical wingtip.
During the BoB, some 109 pilots claimed they could out-turn a Spitfire in a sustained turn once the leading-edge flaps were deployed but I'm sure it depended on the pilot skill.

Some links to check out:

zenoswarbirdvideos.com

link

wwiiaircraftperformance.org

emckenney is one of the more technically knowledgable people on physically modeling air combat games

Wolfhag

HMS Exeter08 Oct 2019 11:02 a.m. PST
emckinney09 Oct 2019 9:04 a.m. PST

I'm an amateur compared to Webster and Valle …

Roll rate is quite complicated as well, varying with speed, angle of attack, and a host of other factors.

The F-4 Phantom II was notorious for a terrible low-speed roll rate with a danger of losing control. Turned out that good training allowed pilots to use the rudder to roll effectively at low speed! (Rudders are normally way down the list of important things in dogfighting, but FAA light plane flight instructions emphasize them a lot: these are raficqll different flight regimes.)

Once the leading-edge flaps popped out on a 109, pilot skill wasn't any more important than in any other flight regime--just don't pull hard enough to stall! The problem.was that in hard turns, the airflow was faster over the outer wing than the inner wing, so the inner flap would pop first, increasing the lift from that wing, which caused a sudden roll to the outside! (out of the turn). A good pilot could anticipate it, but it caught out a lot of pilots.

In any case, the 109 was generally better off keeping its speed up and trying for slashing attacks.

BattlerBritain09 Oct 2019 12:43 p.m. PST

m v squared over r

V is your speed, r is radius.

Double the speed and it's 4 times the radius.

Hence in a game if you move so many hexes (say) before you can turn at a certain speed if you double the speed you'd have to move 4 times the number hexes before you could turn.

Most games have this in a turn mode table.

JD Websters games have it for speeds in chunks of 50mph and turning 30degrees.

If you want to read about it a good physics book would have it, or A C Kermode's Mechanics of Flight is a good one. I bought mine when I was 12.

And stall speed increases by the square root of the number of G's your pulling. Better hope your engine can cope :)

Hope this helps,

B

BattlerBritain09 Oct 2019 1:21 p.m. PST

Oh and all aircraft types will have the same turn radius at the same speed and G pull.

So a Jumbo jet pulling 4G at 400kts will turn the same as a MiG-17 pulling 4G at 400kts.
The difference between them is that a Jumbo jet probably couldn't do it for very long, whereas a MiG-17 could do it for quite a while.

The difference between aircraft types is how much they slow down when pulling so many Gs. How much drag their wings produce at that load and whether their engines can provide enough power to overcome that drag.

It's called Specific Excess Power.

BattlerBritain09 Oct 2019 1:24 p.m. PST

And CY6 has the most unrealistic set of move charts I've ever seen in an air game.

I hate them, but they make for a simple move sequence for a game.

Each to their own.

King Cobra09 Oct 2019 6:12 p.m. PST

Greg's Airplanes and Automobiles explains turn performance in this link.
https://youtu.be/Ir5J9X3txz4

BattlerBritain10 Oct 2019 4:47 a.m. PST

Great vid thumbs up

He explained turn radius using bank angle for no height lost. You can also set bank angle at 90degs and accept a small height loss and approximate using v squared over r.

He explained that straight and level stall speed is a major factor in turn radius. The lower the stall speed the tighter you'll turn.

BattlerBritain10 Oct 2019 4:53 a.m. PST

Link to the book in the vid:
PDF link

The turn radius chart is on page 179.

King Cobra10 Oct 2019 3:44 p.m. PST

BattlerBritain,

Thanks for digging it out. Now I've something to read tonight! De-classified, I hope?

BattlerBritain11 Oct 2019 6:34 a.m. PST

Yep :)

Lion in the Stars12 Oct 2019 1:16 p.m. PST

So a Jumbo jet pulling 4G at 400kts will turn the same as a MiG-17 pulling 4G at 400kts.
The difference between them is that a Jumbo jet probably couldn't do it for very long, whereas a MiG-17 could do it for quite a while.

I dunno, I've seen 747s do some pretty crazy maneuvers, mostly during flight tests. Including barrel rolls.

The scary one was a crash in Kabul, apparently one of the (30-ton!) MRAPs broke loose on the takeoff roll. Pilot did a freaking wingover to get the nose down, but needed about 200 feet more altitude to avoid the ground.

Built Boeing Tough is not a joke.

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