WWII Rate of Turns

[pbehn]

...and Watt was performing marketing. Horses are about 50% more powerful than that.

I think it was just a number that allowed him to make a fortune by the improvement in efficiency of steam engines as I remember.

 

[Elvis]

550 foot-pounds was how much work James Watt originally calculated one standard issue horse could accomplish in one point zero measured seconds.
Doesn't anybody teach history of technology anymore?
Cheers,
Wes

But the formula already has you plugging HP in as a known source, so why are you calculating it again?

 

[XBe02Drvr]

But the formula already has you plugging HP in as a known source, so why are you calculating it again?

He asked what the significance of 550 foot-pounds was. I wasn't calculating anything, just answering his question.

 

[Zipper730]

Since the figures for the P-61 were inaccurate, I've started looking at the other figures.

The F4F-3's stall speed was

• 74.2 mph @ 6895 lb
• 73.7 mph @ 6763 lb (80% fuel)
• 72.5 mph @ 6565 lb (50% fuel)

Which would yield a 3g stall of

• 128.9 @ 6895 lb.
• 127.7 @ 6763 lb.
• 125.6 @ 6565 lb.

Though there might be other variables at work, if I was to scale the stall figures up to the FM-2's weight, I would get the following

• 1G Stall: 77.2 mph @ 7420 lb.
• 3G Stall: 133.7 mph @ 7420 lb.

I guess up to this point, nobody had access to all the data, or was anal enough to compute it all out.

 

[Elvis]

He asked what the significance of 550 foot-pounds was. I wasn't calculating anything, just answering his question.

...and that's another question....WHY are you commenting on this at all?
I was asking Swampyankee something specific about something specific that they posted.
It had nothing to do with you at all.

 

[Elvis]

...and now that that got all mucked up, I'll ask again....ATTENTION: SWAMPYANKEE...

Efficiency is defined as useful work out divided by energy in. For a propeller, that would be airspeed (in feet per second) times thrust (in pounds) divided by (horsepower multiplied by 550) or, equivalently, airspeed (in meters per second) times thrust (in newtons) divided by power (in watts).

Sorry to resurrect this part of the thread, but I'm curious....why are you multiplying HP by 550? What does 550 represent?
Thanks in advance.

Elvis

 

[DerAdlerIstGelandet]

Relax everyone...

 

[swampyankee]

...and now that that got all mucked up, I'll ask again....ATTENTION: SWAMPYANKEE...


Sorry to resurrect this part of the thread, but I'm curious....why are you multiplying HP by 550? What does 550 represent?
Thanks in advance.

Elvis

One horsepower is 550 ft-lbf (a unit of energy) per second. Power is energy per unit time. Confusingly, torque is also measured in ft-lbf (I know; some people use lbf-ft), but the two are fundamentally different quantities, like speed and hair color.

 

[XBe02Drvr]

Sorry to resurrect this part of the thread, but I'm curious....why are you multiplying HP by 550? What does 550 represent?

...and that's another question....WHY are you commenting on this at all?
It had nothing to do with you at all.

Well, excuse me for living! You asked a question, I offered an answer. I didn't realize I was intruding on a private conversation on this public forum. Excuse me all to hell. I'll don my dunce cap and go sit in the corner.
Cheers,
Wes

 

[DerAdlerIstGelandet]

Relax everyone...

 

[Elvis]

One horsepower is 550 ft-lbf (a unit of energy) per second. Power is energy per unit time. Confusingly, torque is also measured in ft-lbf (I know; some people use lbf-ft), but the two are fundamentally different quantities, like speed and hair color.

Thank you for taking the time to explain that.
I think I'll look into this a little further.

Elvis

 

[Laurelix]

sustained 360 horizontal turn
Ki-43-I - 12.5-13 sec
A6M2 - 13-14 sec
A6M3 - 14-15 sec
A7M2 - 14-15 sec
A6M5 - 15-16 sec
Ki-61-I - 16 sec
Ki-84 - 17 sec
Ki-100 - 17 sec
N1K2-J - 17 sec
BF-109E - 17 sec
P-39N - 17-18 sec
Yak-9 - 18 sec
Yak-3 - 18 sec
Ki-44-II - 18 sec
J2M3 - 18 sec
P-40F - 18 sec
Yak-9U - 18-19 sec
BF-109F-4 - 19 sec
BF-109G-10 - 19 sec
La-7 - 19 sec
F4U-4 - 20 sec
La-9 - 20-21 sec
F4U-1 - 21 sec
F6F-5 - 21-22 sec
P-51D (67Hg) - 22 sec
P-38J - 22 sec
FW-190A-5 - 23 sec
Ki-94-II - 23 sec
P-47N - 26 sec

 

[Elvis]

What source are you quoting?

 

[P-39 Expert]

Interesting. P-39N was the tightest turning plane not made in Japan (or an obsolete Bf109E).

 

[tyrodtom]

sustained 360 horizontal turn
Ki-43-I - 12.5-13 sec
A6M2 - 13-14 sec
A6M3 - 14-15 sec
A7M2 - 14-15 sec
A6M5 - 15-16 sec
Ki-61-I - 16 sec
Ki-84 - 17 sec
Ki-100 - 17 sec
N1K2-J - 17 sec
BF-109E - 17 sec
P-39N - 17-18 sec
Yak-9 - 18 sec
Yak-3 - 18 sec
Ki-44-II - 18 sec
J2M3 - 18 sec
P-40F - 18 sec
Yak-9U - 18-19 sec
BF-109F-4 - 19 sec
BF-109G-10 - 19 sec
La-7 - 19 sec
F4U-4 - 20 sec
La-9 - 20-21 sec
F4U-1 - 21 sec
F6F-5 - 21-22 sec
P-51D (67Hg) - 22 sec
P-38J - 22 sec
FW-190A-5 - 23 sec
Ki-94-II - 23 sec
P-47N - 26 sec

Several important aircraft not on that list, F4F, P-36, early model Mustangs, no Spitfires or hurricanes at all.

 

[Zipper730]

We should also try and find the stall speeds whenever possible as that will give the speed at which it becomes possible to pull a given g-load. That said, some airplanes are more sluggish than others and will take longer to pile on the g-load, so, it's just a start...

 

[pbehn]

We should also try and find the stall speeds whenever possible as that will give the speed at which it becomes possible to pull a given g-load. That said, some airplanes are more sluggish than others and will take longer to pile on the g-load, so, it's just a start...

Which stall speed? At which altitude? An aircraft can stall out on full power while pulling many "G". Thats where these "spanwise lift distribution" discussions are important. A plane that is completely benign coming in to land obviously at 1 G can stall with no warning at all its power on limit.

 

[XBe02Drvr]

That said, some airplanes are more sluggish than others and will take longer to pile on the g-load, so, it's just a start...

Any plane that needs to pile on the G load to do its job, such as fighters, fighter-bombers, attack planes, etc, while it may be sluggish in roll, isn't likely to be sluggish in pitch, as that's the working parameter in all combat maneuvering. A plane that reacts slowly in pitch is dogmeat, so elevator response and stick force gradient (the thing that will most likely impede pitch response) are critical design parameters.
Cheers,
Wes

 

[XBe02Drvr]

A plane that is completely benign coming in to land obviously at 1 G can stall with no warning at all its power on limit.

What do you mean by "its power on limit"? "on limited power"? Or "power on its limits"? In other words, "reduced throttle" or "full throttle"? In either case a plane with no wing twist, so the entire wing stalls at once, can hardly be called benign. And if it has wing twist so the wing stalls progressively, root to tip, it's pretty hard to stall it without causing warning buffeting, especially at approach speeds and configurations.
One thing I don't get is why AOA indicators have been so slow to take hold in the civilian world. USN and USMC have been using them to great effect since WWII, and I'm convinced they are a superior way to fly safely. Our club T34 had an approach indexer, which is a rudimentary AOA indicator, and I was taught to use it from my first flight in the bird. Oddly enough, the FAA, when they issued the civil type certificate for the B Model T34 specified that the approach indexer had to be disabled and its indicator masked over. When the club took delivery of their bird, the base CO (who had instructed in Teenie Weenies earlier in his career), came over for a look-see and made the club's mechanic unmask the indicator and re-activate the system. "Best damn safety device on the whole plane. If the FAA gives you any flak over it, send them to me!" The Feds did and the club did, and that's the last anybody ever heard of it. And the legend still lived on when I joined the club several years later.
Cheers,
Wes

 

[Laurelix]

Calculating the Stall Speed is easy.
Here is the formula:

V = Stall Speed (Metres Per Second)
L = Lift Force (Newton's)
CL = Wing Lift Coefficient
P = Air Density (1.225kg/m3 at sea level)
A = Wing Area (Metres Squared)

On this website it will calculate the stall speed for you
Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Velocity

-

Kurfürst - R.A.E. - Messerschmitt Me.109 Handling and Manoeuvrability Tests
Here are the British stall speed tests to determine the CL_Max (Wing Lift Coefficient) for BF-109E

BF-109E
Loaded Weight = 5580lbs / 2531kg
Lift Force = 2531kg x gravity (9.81)
= 24829 Newtons
Wing Area = 174sq ft / 16.17m2
Air Density at Sea Level = 1.225kg/m3
CL_Max = 1.4 (no flaps)

V = 42.31m/s stall speed which is 152km/h

The UK source states 95.5mph stall speed which is 154km/h. The 2km/h difference probably comes from the weight being round up.

Planes with laminar wings have about 1.3-1.33 CL_Max. These wings produce less lift, but also less drag which means these wings give a plane higher top speed whilst sacrificing manoeuvrability

Planes with Normal Wings have about 1.4-1.5 CL_Max
All BF-109's and FW-190's and Ta's have 1.4-1.41 CL. Ki-61/100 has 1.44 CL, Ki-84 has 1.46 CL. P-47's have 1.5 CL, F6F and F4U also have like 1.4-1.41 CL

The lower the stall speed, the better the initial turn. Then it comes down to how well the plane can maintain energy in a sustained turn to determine the overall sustained turn time. Power to weight ratio is good determining factor but the drag of the plane etc also plays a role.

if you want to know the stall speed of a plane whilst it's using flaps, you have to add the flap area to the total wing area and use the correct CL_Max. In this case, BF-109E wing lift coefficient using flaps is 1.9. You'll also have to add the flap area on top of the 16.17m2 wing area in the equation