The Niki and possible answer to uberness? Real numbers.

[Jimdandy]

Thank you F4UDOA. I'm glad to see someone else is thinking beyond hp/wt. Your right. Drag will greatly effect the plane. It increases with the square of the speed. So at lower speeds the planes thrust to weight ratio is very telling. This argument was started with low speed loops so I didn't worry about the drag to much. But thank you for pointing that out. So if I make a simple drag formula it would look like this:

F=KV^2

where K is a proportionality constant for the shape (frontal area) of the aircraft, F is the force of the liquid (in this case air), and V is the velocity of the aircraft. So lets just play with the numbers. Lets say our plane has a known drag of 1000lbs at 200mph. K=0.025lbs/mph. Now lets look at it at 400mph. F=4000lbs. The force really starts to increase with speed. That would also tell you that if you have 4000lbs of thrust generated by your aircraft you are at terminal level flight velocity. Your not going an faster than 400mph with out diving. Those are made up numbers just to show you where the formula takes you.

Edit: I made a mistake. The constant K should be 0.025lbs/mph^2.


[This message has been edited by Jimdandy (edited 02-13-2001).]

[This message has been edited by Jimdandy (edited 02-13-2001).]

[funked]

You forgot about induced drag.  But that equation you have will work at high speed.

[This message has been edited by funked (edited 02-13-2001).]

[Zigrat]

use this http://www.iit.edu/~buonmic/aircraft_test.xls

only thing wrong in that spreadsheet is the prop efficiency stuff, which i made up

if you have real prop efficiency curves, gimme gimme gimme

[funked]

Thanks Zig, I forgot about that thingy!

[Jigster]

The N1K2-J used the same basic wing design as the A6M5 52 B, the later Zero's with the increased skin durability for faster dive speeds. The only real change in aerodynamic surfaces between the two are from the N1K2's ailerons and vertical stabilizer, the N1K2 aileron's are quite a bit shorter to utilize the butterfly flaps, and are hinged deeper in the wing. The N1K1-Ja and A6M5 used the exact same tail design, while the N1K2-J had a larger horizontal stabilizer and full length rudder to compensate torque better.

So if your looking to input wing data try what's available for the A6M5 and A6M6's with increased wing skin. Keep in mind the Zero's wing wasn't what limited it's diving speeds, the ailerons of the A6M2's and A6M5's were designed for under 200 mph flight, alot of the high speed control problems were solved with the clip winged A6M3 but manuverability apparently suffered. Of course the numbers won't be exact but using figures for the Zero's wing you could probably get very close in general ability, at least over the point where the flaps were deployed

Below 250 mph or so (I'm not sure what speed they came down at in level flight, since it was also AoA dependent) the N1K2 was an extremely unclean airframe, the butterfly flaps added alot of induced drag when they deployd. I believe this was the main reason for such a high powered engined intially, to offset the drag in it's manuvering envelope. Or actually a side effect, because it was originally to give a float plane near equal speed of the Zero fighter, the only way to do so with so much drag present.

Once the flaps are deployed, your going to see a great increase in wing area, lift, and drag, and I have no idea what the aerodynamic data would come out to with them deployed...it would probably go a long way towards offsetting it's power to weight ration though.


- Bess

[flakbait]

Here's some numbers I pulled off Joe Baugher's page:

 

Powerplant: NK9H Homare 21 18-cylinder radial rated at 1990hp for takeoff, 1825hp at 5740 ft, and 1625hp at 20,015 ft.

Performance: 369mph at 19,355 ft, 359 at 9,840 ft. Cruising speed: 230mph at 9,840 ft

Service ceiling 35,300 ft

Climb to 19,685: 7 min 22 sec

Range: 1066 miles 219 mph at 9840 ft, max range is 1488 miles w/drop tank

Weights: empty 5,858 lbs, loaded 8,818 lbs, max 10,714 lbs.

Dimensions:
Wingspan: 39 ft 4 7/16 inches
Length: 30 ft 7 29/32 inches
Height: 12 ft 11 29/32 inches
Wing area: 252.95 sq ft

Reading through the page it turns out only 60 were delivered by the end of 1944. 415 total were produced by war's end.

[edit] Some notes Mr Baugher has on the N1K1-J:

 

Since the Homare 11 had been accepted for production before the completion of its final tests, it was plagued with teething troubles. The early Homare engine failed to develop its rated power, the propeller torque during takeoff was excessive, and the visibility during taxiing was poor. However the aircraft had pleasant flying characteristics and the automatic combat flaps gave the aircraft exceptional maneuverability.

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Flakbait [Delta6]
Delta 6's Flight School
Put the P-61B in Aces High
"With all due respect Chaplian, I don't think God wants to hear from me right now.
I'm gonna go out there and remove one of His creations from this universe.
And when I get back I'm gonna drink a bottle of Scotch like it was Chiggy von Richthofen's blood and celebrate his death."
Col. McQueen, Space: Above and Beyond
   

[This message has been edited by flakbait (edited 02-13-2001).]

[Jimdandy]

 

Originally posted by funked:
You forgot about induced drag.  But that equation you have will work at high speed.

[This message has been edited by funked (edited 02-13-2001).]

Gee funked thanks. As I said if I were only discussing this with engineers I would go a bit deeper. There is a large audience reading this so a gave a simple equation that would demonstrate it sufficiently as I stated. Did you read it closely. No or you would have caught the dimensional analysis mistake I made. I'll let you tell them all about Bernoulli's equation and vortex shedding etc. I'm just trying to KISS it. Your great at making little comments let's see you take it over and blow me away with your fluid mechanics. I'm no expert so have at it.

[This message has been edited by Jimdandy (edited 02-13-2001).]

[Widewing]

 

Originally posted by funked:
Widewing you can also get a power estimate from the rate of climb.  (I get about 1800 hp).  If you say it only had 1400 hp then you are disputing the climb data as well as the power figure.

Be sure the drag figures you use weren't based on speed data in the first place.

(Please excuse any typos. This online format makes it a pain in the neck to review a post prior to clicking 'send')

I have not been able to locate specific drag numbers for the N1K2. However, we can make some well founded judgements based upon aircraft of similar size and configuration, for which, I do have data.

To begin, once you know the drag coefficient of the aircraft, you can calculate the flat plate area.

Cdo = Drag Coefficient
Sw = Wing area in square feet.

Cdo x Sw = flat plate area.

Now, take the known horsepower and divide it by the flat plate area. This gives us the available HP per square foot of flat plate area, or HP/f.

Let's look at the F4F/FM-1. It has a zero-lift drag coefficient of .0253 and a flat plate area of 6.58 sq/ft. With 1,200 hp available, the HP/f is 182. This allowed for a max speed of about 320 mph.

How about the P-47B? Its Cdo was .0213 (its wing was especially clean and thin) and a flat plate area of 6.39 sq/ft. With 2,000 hp on tap, the HP/f is 313. This aircraft was capable of speeds just over 420 mph.

Now, let's look at the lowly P-39D. Its Cdo was an excellent .0217 and a flat plate area of 4.63 sq/ft. Having 1,150 hp, this provides for a HP/f of 248. Max speed was 368 mph.

Finally, we can look at the N1K2. Based upon camparible raial engine fighters, I will give it a generous Cdo of .0240. We find that the wing area is 253 sq/ft.

So, 253 x .0240 = 6.07 sq/ft.

Let's assume for a minute that the Homare radial actually generates 1,990 hp.

1,990/6.07 = 328 HP/f

That's considerably higher than the P-47B, yet the Thunderbolt is more than 50 mph faster! How can this be? Simple, the Homare was not making anything close to 1,990 hp.

Let's plug in 1,500 hp into the equation.
1,500/6.07 = 247 HP/f.

At this point, let's go back to the P-39D with its HP/f of 248. The P-39D could manage 368 mph. The N1K2 could reach only 369 mph.
Do you see the correlation? Based upon this method, the Homare was making no more than 1,525 hp, which is fully 465 hp less than rated.

This may be a backdoor method of calculating approximate horsepower, but I'll wager large that it stands up well to any other methodology used for the N1K2-J.

Now, as to climb. This is largely determined by weight and power. However, drag is also a critical factor. Let's compare the Bell P-63A and the N1K2.

Normal combat weight for the P-63A is 8,800 lbs. The N1K2 weighs in at 8,818 lbs loaded for combat (no external stores, full fuel and ammunition for both). It takes the N1K2 7.36 minutes to get to 19,685 ft (6,000 meters). The P-63A gets to 20,000 ft in 5.72 minutes. The Bell has only 1,325 hp available. So why does the P-63A climb so much faster than the N1K2 if it has more power and equal weight? The answer is that the N1K2 had much less power than rated. Moreover, the P-63A has much lower drag numbers.

Cdo = .0182
Sw = 248 sq/ft
Flat Plate area = 4.51 sq/ft
HP = 1,325
HP/f = 293

If the N1K2 was making 1,990 or even 1,800 hp, it would climb as well as the P-63A. The fact is that it does not even come close. So,
this tends to support the 1,525 hp estimate.

For JimDandy:
Power is determined by HP and propeller efficiency. Typically the WWII fighters had prop efficiencies in the 80% range, give or take 2%. Based upon this, Francis (Diz) Dean provides a simple formula to determine drag as equalized by thrust.

Thrust (in pounds) = 375 x prop efficiency x horsepower/TAS (true airspeed).

His example is that of a P-40 maintaining a constant 280 mph with 900 hp.

T = 375 x .80 x 900/280 = 964 lbs of drag, which must be equalled by 964 lbs of thrust to maintain a constant speed.

No WWII fighter ever produced thrust equal to its weight. Even the F8F would require over 10,000 lbs of thrust to accelerate straight up. Let's assume he is climbing at
125 mph, and not accelerating.
T = 375 x .80 x 4,500 hp/125 = 10,800 lbs, which is pretty close to weight + drag.
This would allow for a climb rate of about 11,000 ft/min., straight up. This is not out of line for the hotrod F8F that set the time to 10,000 ft record of just under one minute. However, this was a stripped down fighter making nearly 4,000 hp. We know that the production F8F could manage 4,570 ft/min. with 2,100 hp. Surely, it had nowhere near a 1:1 thrust to weight ratio. 1:2 at the very best.

Data sources:
 
America's One Hundred Thousand by Francis Dean

The American Fighter by Angelluci and Bowers

The Complete Book of Fighters by Green and Swanborough.

My regards,

Widewing

[Jimdandy]

Thanks Widewing. I must have been the data on that hotrod version I was looking at. I appreciate the explanation. As I said originally my intention was more to show that as the ratio went past 1:1 a plane could accelerate in the vertical. I had wrongly thought that the F8F had a greater than 1:1 but I never thought that it was the norm anyway. I also wanted people to look past the simple hp/wt and see that the prop has to use that power efficiently or the horsepower is wasted. hp/wt is a very good sign of a hot plane but it isn't the end all to making work. You can have a 10,000hp car but if your using smooth steel wheels in ice your not going anywhere.

[This message has been edited by Jimdandy (edited 02-13-2001).]

[Vermillion]

Heheh FYI JimDandy  

Most of the people that respond to the techno threads like this, are Engineers of one discipline or another.

Funked, Wells, Niklas, Zigrat, Myself, and I'm sure there are others that I'm forgetting at this exact moment.

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Vermillion
**MOL**, Men of Leisure

[flakbait]

Here's some food for thought. I took film of my little jaunt in an N1K2 loaded with a pair of 551 lbs bombs. Even with an extra 1,102 pounds on board it still handles like a dream.

Niki flight

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Flakbait [Delta6]
Delta 6's Flight School
Put the P-61B in Aces High
"With all due respect Chaplian, I don't think God wants to hear from me right now.
I'm gonna go out there and remove one of His creations from this universe.
And when I get back I'm gonna drink a bottle of Scotch like it was Chiggy von Richthofen's blood and celebrate his death."
Col. McQueen, Space: Above and Beyond
 

[Jekyll]

Extremely interesting analysis Widewing.  Much food for thought here.

I suppose part of the 'problem' (if one exists) is that we have no real idea how the FM's of the AH aircraft are generated.  Let's look to history a little.

Back in the days of AW I understand it used a simple 'table-based' flight model.  This enabled the aircraft to hit the right numbers, but basically consisted of a number of lookup tables for the aircraft.

So, a particular aircraft, at a particular weight, at a particular angle of attack with a particular throttle setting and at a particular altitude would generate a specific climb rate.

Now lets fast forward to AH.  IF the Nik had more engine power than it should, the AW based system would still let it hit the right numbers for top level speed, climb rate etc.  I would imagine that the only place that the incorrect engine power would show up would be in acceleration, vertical performance and the ability of the aircraft to replace lost energy after maneuvering (somewhat similar to E retention).

Now whether the same thing applies here in AH I do not know.  But the concept certainly is interesting.

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When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
Chapter 13, verse 11

[Jimdandy]

 

Originally posted by Vermillion:
Heheh FYI JimDandy    

Most of the people that respond to the techno threads like this, are Engineers of one discipline or another.

Funked, Wells, Niklas, Zigrat, Myself, and I'm sure there are others that I'm forgetting at this exact moment.

Thanks Verm I didn't know that. I still don't think it's a bad idea to KISS on here so those without the background can get some enjoyment out of it. Admittedly there are times where that's almost impossible but I'm sure there are some plane nuts and budding engineers that would like to know so I try to make analogies. What pisses me off is when I make a point of saying things like "...if I make a simple drag formula..." and some know it all pops in and tells me what I missed. Well NS buddy I just said it was simplified. Or ask's me why I'm talking about 1:1 thrust ratios when I'll I said was "...Any plane with a thrust to weight ratio greater than 1:1 will accelerate in the vertical..." Just wonted those that didn't know what the relationship of the numbers meant when they found the data. I think Widewing made a good argument against the N1K using comparative data and some good rules of thumb. It does bring into question the performance. My insistence on the thrust/wt was to try to see if that would show the reason for the increased performance. As you know hp/wt isn't showing it all. Maybe there was something to be gained in looking beyond that. I don't work with this stuff every day but I do know the plane doesn't magically move thru the air based only on the hp/wt. The prop is pretty important in making things happen.

[This message has been edited by Jimdandy (edited 02-14-2001).]

[funked]

Sorry Jimmy I have habit of reading the equations and skipping the roadkill.  Comes from grading too many papers I think.  
I just thought it was funny that you would tell Fscott he had oversimplified (ignored variation in prop efficiency) and then threw induced drag out the window.  Carry on.

[Jimdandy]

 

Originally posted by funked:
Sorry Jimmy I have habit of reading the equations and skipping the roadkill.  Comes from grading too many papers I think.    
I just thought it was funny that you would tell Fscott he had oversimplified (ignored variation in prop efficiency) and then threw induced drag out the window.  Carry on.

Yes I see where your comeing from. NP.