WWII Rate of Turns

[Shortround6]

I think the variation in gravity is the least of your worries/considerations.
Come on, gravity at 9000 meters is 0.3% of gravity at sea level?
10,000lb airplane will act like a 9970lb plane at 9000 meters?


You are going to get more variation in air density on cold and hot days. Let alone fuel burn and oil consumption.
ANd if you are figuring things that close you better being using pilots who are 100% clones of each other and planes that have 100% identical fit and finish.

 

[swampyankee]

Pitching moment does, as it will influence trim drag. Lift coefficient also comes in as higher lift coefficient means greater induced drag; this is why deltas have, historically, bled off speed quickly in air combat. Maneuvering flaps will probably make sustained — vs instantaneous— turn rate worse, as the increase trim drag and tend to be partial span, so they increase induced drag.


Lift coefficient has one direct effect on sustained turn rate: induced drag increases by lift coefficient squared, so the induced drag in a 2-g turn is 4 times what it is in level flight at the same speed and altitude. There's also a second order effect from the fact that the horizontal tail needs to provide lift to maintain the proper angle of attack for the new lift coefficient, which increases trim drag. Propellers ahead of the c/g are destabilizing, which could be another problem, and could require more trim.

Lift flaps can increase instantaneous turn rate, as they can increase achievable lift coefficient, but since they're usually part span, they will increase induced drag -- there will be a big vortex where they end -- and, since they increase camber, they will increase the nose down pitching moment and, so increase the trim drag.

 

[pbehn]

I was looking at a graph and found something interesting: Gravity varies with altitude...

• 0 m = 9.807 (listed, actually 9.80665) m/s
• QUOTE]

.

You do have a problem with units Zipper, acceleration due to gravity is m/s²

From Wiki
The apparent force of gravity on Earth is the resultant (vector sum) of two forces:[30] (a) The gravitational attraction in accordance with Newton's universal law of gravitation, and (b) the centrifugal force, which results from the choice of an earthbound, rotating frame of reference. The force of gravity is the weakest at the equator because of the centrifugal force caused by the Earth's rotation and because points on the equator are furthest from the center of the Earth. The force of gravity varies with latitude and increases from about 9.780 m/s2 at the Equator to about 9.832 m/s2 at the poles​

 

[Zipper730]

I think the variation in gravity is the least of your worries/considerations.

I just didn't know to what degree it varied with altitude. I know in space you usually see in orbit, zero g because you're basically in a constant state of fall except you're moving so fast that you never actually crash into the Earth (well eventually you do, it's called orbital decay, but...)

 

[Shortround6]

What keeps things in orbit is centrifugal force countering gravity. Orbital decay happens because most low orbit satellites/objects are not in a true vacuum and the very low density air is causing drag which slows the satellite/object below the speed needed to stay in orbit, the lower the satellite/object "falls" the higher the density of the "air", the more drag, the faster the speed bleeds off and then just keep repeating.

I would also note that even P-40 fighters could vary by over 100lbs (extreme) from one aircraft to another on the production line (empty weight) so trying to figure gravity to 3-4 decimal places when computing performance is pretty much a waste of time.

 

[pbehn]

View attachment 485668

What keeps things in orbit is centrifugal force countering gravity. Orbital decay happens because most low orbit satellites/objects are not in a true vacuum and the very low density air is causing drag which slows the satellite/object below the speed needed to stay in orbit, the lower the satellite/object "falls" the higher the density of the "air", the more drag, the faster the speed bleeds off and then just keep repeating.

I would also note that even P-40 fighters could vary by over 100lbs (extreme) from one aircraft to another on the production line (empty weight) so trying to figure gravity to 3-4 decimal places when computing performance is pretty much a waste of time.

If the plane is on full power, then for example a Merlin used 150 gallons per hour, which means it is losing something like 1 lb per second in fuel, it needs a computer or some calculus to make sense of it.

 

[DarrenW]

There are instances where planes have very good initial turn (they turn very well with energy) but their engine is underpowered and as soon as they get into prolonged turns, they turn into whales that do small turn radius but they take long time to complete one because the plane is fighting stall thus the plane isn't turning efficiently because it doesn't have enough energy to perform manuevers. One example would be the F6F-3.

Hi Laurelix97,
While I can appreciate your scientific approach concerning the determination of an aircraft's turn rate, I would have to disagree with the comment that the F6F-3 was "underpowered". Of the eleven US fighters discussed in Dean's America's Hundred Thousand, it had one of the lowest power loadings at the specified altitudes:

 

[DarrenW]

Dean did some calculating of his own regarding the turn radius of various US fighters in America's Hundred Thousand. He basically was looking at two factors, wing loading and maximum wing CL, under the assumption that the aircraft had enough power to sustain the turn and not sink in altitude. With this information he placed the FM-2 as best of the eleven fighters, giving it an arbitrary 100%, and ranked the others in comparison to it accordingly.

For instance, the P-63 came in second at being able to achieve 124% of the FM-2's radius, followed by the P-61 at 133%, then the F6F at 138%, the P-51 at 179%, and so on. Even more surprising to me than the Black Widow's ranking was the placement of the F4U in dead last. Dean surmises that the relatively lower maximum CL, due to the spoiler on the right wing, was the culprit and apparently NACA testing supports this notion.

I figure that turn radius is just as important as turn rate, because if you can't turn tight enough to bring your guns to bear on an enemy than being able to turn at a high rate of speed really amounts to nothing.

 

[Zipper730]

What does minimum turnr-radius index number mean?

 

[swampyankee]

Dean did some calculating of his own regarding the turn radius of various US fighters in America's Hundred Thousand. He basically was looking at two factors, wing loading and maximum wing CL, under the assumption that the aircraft had enough power to sustain the turn and not sink in altitude. With this information he placed the FM-2 as best of the eleven fighters, giving it an arbitrary 100%, and ranked the others in comparison to it accordingly.

For instance, the P-63 came in second at being able to achieve 124% of the FM-2's radius, followed by the P-61 at 133%, then the F6F at 138%, the P-51 at 179%, and so on. Even more surprising to me than the Black Widow's ranking was the placement of the F4U in dead last. Dean surmises that the relatively lower maximum CL, due to the spoiler on the right wing, was the culprit and apparently NACA testing supports this notion.

I figure that turn radius is just as important as turn rate, because if you can't turn tight enough to bring your guns to bear on an enemy than being able to turn at a high rate of speed really amounts to nothing.
View attachment 485745

Most of the lift coefficients they're showing -- considerably over 2 -- are highly suspect. While there is some momentary increase in lift coefficient when there's a rapid change in angle of attack, such as during a landing flare, I would be very surprised if any of these aircraft could demonstrate no-flap instantaneous lift coefficients over 1.75 in turning flight. Indeed, the only lift coefficient in that table that I find plausible is the Corsair's.

 

[CORSNING]

I figure that turn radius is just as important as turn rate,

That depends on what game you are playing. Think A6M5 vs Yak-3, there
is no question that the A6M5 will outturn the Yak-3 IF they both limit their
speeds to 225 mph. This all changes if the Yak decides to accelerate up
to higher speeds. At 320 mph. the Yak-3 controls are still fully functional
where as the Zero's are not. Once into a turn at these speeds the A6M
still has a smaller turning radius, BUT the Yak-3's much greater roll rate
allows it to go into the turn infinitely faster and continue on to complete
its turn quicker. This allows the Yak-3 with its much greater climb rate
at 1,000 m to gain quite a height advantage....and so on.


because if you can't turn tight enough to bring your guns to bear on an enemy than being able to turn at a high rate of speed really amounts to nothing.

There are other ways to bring your guns to bear as I tried to point out above.

There is another consideration that makes quite a difference also, engine capability.
While the Yak-3 can pretty much have its way with the A6M5 at 1,000 m. Its Klimov
engine's power tends to peter out at ALTITUDE. This is another great factor to take
into consideration. While the cleaner design of the inline Yak allows its top speed to
remain 384 mph. at 6,000 m. compared to the A6M5's 350, the Sakae 31A engine's
output at that altitude gives it a better climb rate of 2,620 fpm vs. 2,250 fpm. of the
very close in weight Yak.

 

[Zipper730]

I figure that turn radius is just as important as turn rate,

That depends on what game you are playing. Think A6M5 vs Yak-3, there
is no question that the A6M5 will outturn the Yak-3 IF they both limit their
speeds to 225 mph. This all changes if the Yak decides to accelerate up
to higher speeds. At 320 mph. the Yak-3 controls are still fully functional
where as the Zero's are not. Once into a turn at these speeds the A6M
still has a smaller turning radius, BUT the Yak-3's much greater roll rate
allows it to go into the turn infinitely faster and continue on to complete
its turn quicker. This allows the Yak-3 with its much greater climb rate
at 1,000 m to gain quite a height advantage....and so on.

Okay, so let's divide this into the turn radius as well as rate of turn

 

[DarrenW]

What does minimum turnr-radius index number mean?

It is calculated by dividing an aircraft's wing loading by it's maximum coefficient of lift. Dean surmises that it's proportional to minimum turn radius.

 

[Zipper730]

At the other end of the "ad absurdum" scale the FW190 could out manoeuvre the Mosquito at all speeds except maximum.

Wait, I thought the Mosquito maneuvered better at higher altitudes...

Advance ratio is airspeed (ft or meters per second) divided by (diameter (ft pr meters) times rate of rotation(rev/sec)

Where would you find RPM rates for WWII aircraft?

 

[fubar57]

WWII Aircraft Performance

 

[Zipper730]

What do you guys think about this one?


View: https://www.youtube.com/watch?v=Ir5J9X3txz4

 

[parsifal]

I thought this was interesting as a non-technical assessment

P-40 and Zero

 

[Zipper730]

There is something interesting here to potentially make note of when it comes to comparing the F4U vs the P-51: They might very well have based the coefficient of lift on the P-51 operating with flaps and the F4U without.

 

[pbehn]

Wait, I thought the Mosquito maneuvered better at higher altitudes...

?

I read an account of a Mosquito bomber avoiding an Fw 190 at high altitude by going into a shallow high speed dive, the Mosquito just had slightly better control than the Fw which couldn't get a shot on target, at that height and speed the Fw doesn't have much time before it runs short of fuel.

 

[Zipper730]

WWII Aircraft Performance

Good point, I'm looking up figures for most of the major aircraft. I figure climb-speed and maximum speeds would be the most useful