Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Widewing on February 13, 2001, 09:34:00 PM
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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 radial 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 the N1K2 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. So, yes, you were probably looking at the numbers associated with the record breaking hotrod F8F.
Other interesting HP/f ratios:
P-51D: 366 (437 mph)
P-38J: 355 (421 mph)
P-47M: 422 (475 mph)
F6F-5: 253 (380 mph)
F8F-1: 368 (440 mph)
F7F-1: 372 (445 mph)
The correlation is interesting but certainly not linear.
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
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Widewing,
I think your calculation is not taking into consideration that the Japanese fuel, at 87 octane, will cause the engine's power to diminish far more rapidly than the high octane fuel that the US used. Thus the N1K2, like all Japanese fighters, will be much more competetive at low altitude where there is more oxogen for the engine to breathe. Any climb to 19,000 feet is going to introduce this weakness of the Japanese fighters, and thus increase the amount of time it takes to reach altitude.
That said, it is an aknowledged fact (I have heard) that the N1K2 performs too well at altitude in AH. It also bleeds energy a little too slowly in turns.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak
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You know, I try to look at all these numbers and equations - people think up some amazing things to try and force an aircraft's handling the way they think it oughta be, and I just shake my head.
I go back to a statement I see over and over in US pilot journals and aircraft books, which states plainly that the Niki's maneuverability was *almost unbelievable*.
fscott
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Originally posted by Karnak:
Widewing,
I think your calculation is not taking into consideration that the Japanese fuel, at 87 octane, will cause the engine's power to diminish far more rapidly than the high octane fuel that the US used. Thus the N1K2, like all Japanese fighters, will be much more competetive at low altitude where there is more oxogen for the engine to breathe. Any climb to 19,000 feet is going to introduce this weakness of the Japanese fighters, and thus increase the amount of time it takes to reach altitude.
That said, it is an aknowledged fact (I have heard) that the N1K2 performs too well at altitude in AH. It also bleeds energy a little too slowly in turns.
I have mentioned this elsewhere and this is exactly my point. What prevented the Homare from developing its rated power was the 87 octane fuel limitations. This results in lower manifold pressure. Usually, the propeller is re-indexed to provide greater efficiency at lower MAP. Indeed, it was the lower octane fuel that kept power down to the 1,500 hp range. However, this was a supercharged engine and it shifts from low to high blower based upon altitude and throttle setting. The intention is to maintain something close to sea level density in the intake air charge. The lower octane limits MAP, and has no significant relationship to altitude. The anti-knock compounds have no idea what height you are flying at. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) The fact remains that you are limited to, let's say 44 in/Hg, regardless of your altitude. Exceed this with the Homare and you will experience detonation and rapid engine failure (not unlike the Allison V-1710-F17). Without higher octane, or at least ADI (water injection), the Homare could not produce anywhere near its rated power.
Just for the hell of it, I graphed some HP/f vs TAS examples. Lo and behold, they are far more linear than I had originally thought.
Here's the graph:
(http://home.att.net/~historyzone/HPf-TAS.JPG)
My regards,
Widewing
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Just want to add 1 thing to this before it goes too far:
Unlike the US fighters you are mentioning the Homare (like the Russian Ash-82FN) was only a Single stage supercharger. This meant the figures for the homare of 1,980 hp at Sl were probably correct for it's max throttle and supercharger settings at SL. However there was no second setting for the supercharger when the engine was operating higher- based on the detailed Ash-82FN figures I have my guess was it's performance was similar and began to lose it's max manifold pressure by 8,000 ft or so.
This BTW is correlated by all the information I have seen on this plane listing it's power as an optomistic 1600hp at 19,800 ft.
Thus widewing your figures should have some sort of descending scale to represent the loss of power over critical altitude where any of the single stage supercharged planes will have a variation in their hp/sqft ratio.
Or something like that (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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If your in range, so is the enemy.
(http://www3.bc.sympatico.ca/sorrow/sorrow.gif)
[This message has been edited by Sorrow[S=A] (edited 02-13-2001).]
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I understood that the Homare had Water Injection to prevent detonation. This would affect both the N1K2 and Ki84.
I will see if I can locate the post that stated this.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak
[This message has been edited by Karnak (edited 02-14-2001).]
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I think Widewing makes a good point and there are also quite a few general references to problems with Homare engines. The N1K2 appears to have a thicker wing section than US fighters like the P47-wouldn't that keep its speed down also. Does anyone know what the real 20mm ammo loadout was for the N1K2?
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Here we go:
Originally posted by brady in the "N1K2-J"George" SHIDEN-KAI and MW-50" thread:
I was wondering if anybody new if the wep on the N1K2 in the game is Methanol(MW50), my book on the George, Aero Detail 26 Shiden kai, shows that on the surviving examples in the US (3 out of the 4 taken from Japan and shipped hear for evaluation) were equipped with this,their is photographic evidence on multiple Aircraft.
Also the book states that 4 60kg or 2 250kg bombs could be caried.The four smaller ones would be kind of nice to carry on JABO missions sometimes.
The book also shows that the inboard gun had 200 rounds and the outboard 250 rounds,for a total for all 4 guns as 900rds.
This book is filled with very detailed photos of these planes taken in the various museums where these planes are on display, I highly recommend it,they have a whole series of these books on all sorts of planes.
Originally posted by Pyro in the "N1K2-J"George" SHIDEN-KAI and MW-50" thread:
The Ki-84(using the same Homare engine) had water injection as well. Ammo load on the George has been discussed in another thread and that's something I'll be changing in the next version. However, the Aero Detail is not exactly a good source for this information as they cite about 3 different ammunition capacities throughout the book.
Originally posted by Nath-BDP in the "N1K2-J"George" SHIDEN-KAI and MW-50" thread:
Hrmm... the Ki.84s didn't use Homare powerplants unless the Ha-45(Army Type 4) 23 is the IJAAF name for the NK9H Homare 21?
Looking at the HP output it doesn't seem so.
And:
p.s. The A6M6c with the Sakae 31 had methanol/water injection.
Originally posted by brady in the "N1K2-J"George" SHIDEN-KAI and MW-50" thread:
Nath.. They are the same engine,The Japanese army and navy had the mother of all service rivalries going on, they used totally different designation systems.
And as Pyro was kind enough to point out both had Methanol injection systems.
It would be cool if we get the 4 60kg bombs for the George it would make it nice for flak diving (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak
[This message has been edited by Karnak (edited 02-14-2001).]
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Widewing:
You can't use high-altitude speed readings together with sea level power ratings. At sea level, P-47D top speed is about the same as the N1K2-J.
Likewise you can't use sea level power ratings with 0-20,000 feet climb times. At sea level the N1K2-J outclimbs the P-39 (any variant) by up to 1000 fpm.
Hint: Repeat analysis using sea level speeds and climb rates. Good equations, bad data.
[This message has been edited by funked (edited 02-14-2001).]
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PS I just realized that the sea level info for the N1K2-J I am talking about comes from HTC's charts. I'm assuming those are from a historical reference. If that assumption is wrong then my argument is circular, and the analysis I suggested will only tell us what sea level hp value HTC used in their N1K2-J model.
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Karnak, I could not of said it better myself (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Brady
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(http://content.communities.msn.com/isapi/fetch.dll?action=MyPhotos_GetPubPhoto&photoId=nHwCwcDEJznXbXfCxAJfgD0a7w1sDVrWuMP28UBOabRCH339Yvya3KrR2Q8UMjrBJ)
[This message has been edited by brady (edited 02-14-2001).]
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When i look at the climbrate of the N1k in AH, then it seems to be modeled with ~1700Hp.
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I think Sorrows has a good point. That would explain the drop in performance at higher alt. while maintaining excellent lower and medium alt performance.
There has been some mention of fuel in here. I have a question. Wouldn't the fuel blend play a big role in the over all performance. I understand the aircraft fuel has more oxygen in it for better performance at high altitude. I have heard that it also contains nitro methane. I would think that any of these were lacking in the Japanese fuel and the US had it there would be an advantage at higher alt. I would also think that the MW injection would not only work for controlling the hot spots in the cylinder head but as a mild oxidizer too. Wouldn't you also increase your charge density thus increasing volumetric efficiency? Can anyone help me out on this. It's been to many years since chemistry. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
One more question. I've read that at altitudes above approximately 32k if the ignition system isn't designed for those altitudes it will fail. Could it be that the Japanese hadn't figured that out and it limited the high altitude performance of their aircraft? Am I wrong about the ignition thing? It's something I seem to have read in an article about the P-47 and the F6F.
If anyone can slap me into shape on both of these I would appreciate the info. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) Thx
[This message has been edited by Jimdandy (edited 02-14-2001).]
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Widewing,
Re-map your charts for sea level where the air density is a constant. If you do a couple of birds will be out of wack with the others. The P-47 and F4U namely.
I'm really not disagreeing with you. But in order to get flat plate drag area you need accurate Cdo numbers. Some of those numbers from AHT are a little suspect considering the speeds they were measured at vary greatly. From about 200 to 250mph in some cases. I have been searching for the NACA report with drag info for American fighters for a long time. If you have any of this please share.
Thanks
F4UDOA
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Jimdandy,
The problem was with the F4U and F6F cutting out at about 32K. The problem was that the ignition area(Don't know exactly??) was not pressurized properly due to manufacturing irregularities. Causing the A/C to cut out at high alt. This was resolved after the first few hundred A/C built.
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Thx DOA. Could the lack of proper ignition pressurization played a role in the generally poor high altitude performance of the Japanese fighters?
BTW Don't forget the fuel/MW question. Anyone?
[This message has been edited by Jimdandy (edited 02-14-2001).]
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Widewing, if you have the numbers for the A6M5b or c try plugging in it's drag coefficent for the N1K2-J.
The wings of the N1K1-Ja and A6M5c/A6M6 are practically identical when clean, and neutral aileron. Wing root to wing tip the wings are the same span, shape is the same, and the N1K1-Ja has a slightly narrower chord past the ends of the flaps. The N1K1-Ja was a much cleaner airframe (minus the gondolas) then the Zero of course, but they stuck with the same er um "combat proven" design.
- Bess
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Originally posted by F4UDOA:
Jimdandy,
The problem was with the F4U and F6F cutting out at about 32K. The problem was that the ignition area(Don't know exactly??) was not pressurized properly due to manufacturing irregularities. Causing the A/C to cut out at high alt. This was resolved after the first few hundred A/C built.
This was in the ignition coil. Air is a good insulator but its insulating properties per unit volume decreases as air pressure is decreased. The low air pressure in the coil allowed the electrical impulses to short to ground before they reached the gaps in the spark plugs.
The Army Air Force (along with P&W) resolved this by installing a pressurized ignition coil on the R-2800 powered P-47 and promptly did not share the information with the Navy (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
MiG
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Originally posted by MiG Eater:
...The Army Air Force (along with P&W) resolved this by installing a pressurized ignition coil on the R-2800 powered P-47 and promptly did not share the information with the Navy (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
MiG
You know what is really pathetic about that is that do to their lack of cooperation/rivalry men could have died. At the very least it held up the introduction of the F6F for a few weeks. In the article I read one of the engineers at Grumman just happened to be talking to a fellow engineer friend at Republic who said something like '...Oh you guys didn't know about that. We found that out testing the P-47...' Sad really. And it still goes on to this day.
[This message has been edited by Jimdandy (edited 02-14-2001).]
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Jimdandy,
Thankfully for us, any rivalry's that our services had paled in comparison with the mother of all service rivalries going on between the IJA and IJN.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak
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I too had heard that the Homare used water-injection & I even read somewhere it used water-methanol injection.
I *have* seen detailed internal cut-aways of the Ki-84Ia, and lo and behold, there was a fuselage tank (behind the pilot if I remeber rightly) which was labelled "water-methanol fluid" in the description.It is possible - in fact highly likely that the N1K2-J (and 1-J too) used water-methanol.
As mentioned earlier, water-methanol is normally injected below the rated altitude of the powerplant & acts as an anti-detonant, cooling the charge.Water injection on its own also acts in exactly the same way.In fact, I don't think the methanol acts as an anti-detonant but is basically there to prevent the injection water from freezing, though I could be wrong - it's entirely possible the methanol had its own effect on the charge, but I'm simply not sure.
PS:Oops - looking back at earlier posts in this thread it looks like it has been fairly well established that the N1K2-J used water-methanol.
Btw ppl are referring to the Japanese water-methanol mixture as MW-50, which is a German RLM designation.It means the injection fluid is split evenly into 50% methanol & 50% water.It was *not* the only form of MW mixture used by the LW, though it was used in the vast majority of cases.I've seen mixtures with 75/25 (or is that the other way around?) mentioned - MW-25 or MW-75 it was called, I can't remember which.
As for the Japanese water-methanol fluid, I have no idea as to what proportions of methanol & water were used.Does anyone know whether they used a 50/50 mixture ?
Btw Nath, I was under the impression that although most Ki-84Ia's used an 1,800hp powerplant, some also used a 1,990hp unit.Is this correct?
Also, does ne1 know what engine the Ki-84Ia used in the famous trials by the USAAF of that a/c during 1946 during which it achieved a max TAS of 427mph & outperformed & out-maneuvered up to 25k alt both a P-51D & P-47N (some sources state it was a -47D) which were used in the tests?
I know that the Hayate in question had been overhauled by USAAF ground crew to USAAF "operational standards" and was using hi-octane avgas, unlike war-time Jap Ki-84's which were usually poorly built, maintained & used low-octane fuel.But was this example using a 1,800hp Ha-45? I think the test results were a testament 2 just how dangerous the Hayate could have been had it been manufactured, maintained & fuelled to Western standards.That it was not was fortuitous 2 Allied airmen.
But if it was 2 be modelled in AH, what performance would be modelled?That of an operational Ki-84Ia with its often defective engines(whose performance varied markedly between different batches of Franks & even consecutive units on the same production line!) & low-octane gas whose top speed has regularly been stated as approx 392mph, or the "ideal" Hayate tested by the US in 1946 with a smoothly running powerplant & high quality fuel? IMHO, sice we don't model manufacturing defects in AH or system failures like jammed guns, I'd like 2 see the Ki-84 modelled as its designers envisaged - using a relatively trouble free powerplant with decent quality fuel (the avgas used in the last 12-18 months of WW2 by the IJN & IJNAF was generally absolutely atrocious)- and that was the Hayate tested in 1946 ;-)
[This message has been edited by C_R_Caldwell (edited 02-14-2001).]
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Originally posted by Karnak:
Jimdandy,
Thankfully for us, any rivalry's that our services had paled in comparison with the mother of all service rivalries going on between the IJA and IJN.
Heh, Luftwaffe and Kriegsmarine relationships were pretty stormy aswell...
Many merchant ships were saved because that...and KM Graf Zeppelin owes its inexistance to Goering's absolute opposal to give the Kriegsmarine an air branch (any german plane flying belongs to luftwaffe, he said)
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Btw Nath, I was under the impression that although most Ki-84Ia's used an 1,800hp powerplant, some also used a 1,990hp unit.Is this correct?
Most Ki-84-Ia's used the Ha-45 and the model 11, which had a hp output of 1,800 hp at take-off and 1,650 hp at 6,560 ft. Early pre-production models also had individual ejector exhausts for a measure of thrust augmentation.
The aircraft that was tested at Wright Field, however, was powered by the Ha 45 type 21 (1,990 hp at take-off and 1,850 hp at 5,740 ft), an engine that was installed in later version of the Ia in limited numbers. This engine, like its predecessors had a tendency to suddenly lose fuel pressure. The second to last version of the Ha 45 on the Ki-84 was the 23(1,900 hp for take-off and 1,670 hp at 4,725 ft), which overcame the loss of fuel pressure by having a low-pressure fuel injection system but this powerplant had one flaw, it lost some of the previous Ha-45's hp. The availability of this type was very limited, however, due to the destruction of Nakajima's main production facility at Asakawa by bombers of the XX Bomber Command.
Below is the info on the Ki-84 tested at Wright Field:
(http://www.geocities.com/nathownsj00/wright.gif)
and now...
Viewed from the cockpit
The following account of the characteristics of the Hayate was prepared by one of the USAAF test pilots responsible for evaluating a Ki.84-I-ko which had been recovered at Clark Field, Luzon, and transported to Wright Field, Dayton, Ohio, after preliminary testing by a Technical Air Intelligence Unit pilot in situ whose task it was to ready the fighter for the subsequent tactical trials in the USA. The evaluation at Wright Field comprised a total of 11 1/2 flying hours but the test programme was frequently interrupted by failure of exhhaust stacks as a result of the poor materials used in their manufacture coupled with inefficient welding. Problems were also experienced with the hydraulics.
THE COCKPIT of the Hayate was entered from the port wing root walkway and was facilitated by a retractable step and a push-in type handhold at the wing trailing edge, and a second retractable step just below the cockpit sill, these being extremely well located and making for easier access than offered by con-temporary AAF fighters. The stamped metal pilot's seat could be adjusted vertically by means of a handle on the left side, but the locking pin in this particular aircraft did not always engage, with the result that the seat had an annoying tendency to shift under g force changes. The AAF shoulder harness that had been fitted for the test programme was anything but satisfactory, affording no protection for the pilot whatsoever in the event of a crash landing as no stress member had been installed over which the straps could be passed and in the event of an accident involving longitudinal deceleration, the sheet metal seat back would undoubtedly have failed and the pilot would have struck his head on gunsight or instrument panel.
The layout of the cockpit itself was, in general, satisfactory, with the flight and engine instruments logically grouped, the former being arranged on the upper centre portion of the panel with the latter below. The flap and undercarriage controls were situated on the lefthand side of the floor, with the elevator trim wheel and engine control quadrant against the lefthand side wall. No fiight-adjustable aileron or rudder trim tabs were provided, preventing the aircraft being trimmed for hands-off flight. The auxiliary electrical panel and ignition boost control containing circuit breakers were below the instrument panel on the right; the internal and external fuel selector valves and fuel cooler and primer controls were on the righthand side of the floor, and the cowling and oil cooler flap controls were on the upper right cockpit side, together with the radio equipment. The auxiliary hydraulic pump was further aft on the righthand side and the mechanical up-lock release was on the left side of the cockpit floor.
The wobble pump, primer and starter button, all being on the right, kept one hand rather busy in starting, and it soon
became obvious that the Hayate handled rather poorly in taxying owing to inadequate braking action, a condition aggravated by the inefficient design of the rudder bar and toe brake assembly. Use of the brakes was mandatory for "S"ing in order to obtain a measure of forward vision. At the same time, braking had to be strictly limited in order to prevent overheating and locking as a consequence. It proved difficult to get the tailwheel to castor and vision for taxying was certainly not improved by the narrow cockpit and rearward position of the seat, but the actual take-off characteristics were good, with negligible torque effect if rated power was applied gradually. On the other hand, if power was piled on, full right rudder and some braking were necessary to counter the strong pull to port. Three-point take-offs could be safely executed at 95 mph (153 km/h) IAS with normal rated power or above, initial acceleration being normal with either 15 deg flap or no flap at all. At 150 mph (241 km/h) IAS only some four seconds were required for undercarriage retraction, this process producing no loss in altitude or sinking feeling and negligible trim change, and it was immediatcly obvious that initial climb rate wasextremely good, although no performance climbs could beattempted owing to flying time restrictions.
Excellent handling and control
Once the canopy was shut it became apparent that the cockpit left something to be desired from the viewpoint of comfort for a normal-sized pilot owing to the severely restricted head room, and the design of the seat coupled with lack of provision for rudder pedal adjustment would obviously have resulted in some discomfort during extended operations. However, body room was ample and heat level and ventilation volume were found to be good for warm weather operation at low and medium altitudes cold weather operation would have been another story owing to lack of cockpit heat. Despite a some- what narrow canopy, combat vision was excellent in climbing flight when gentle "S"turns were necessary. The cockpit noise level proved to be fairly normal for a radial-engined fighter without an exhaust collector ring, and the vibration level was definitely lower than that of the A6M5 Zero-Sen, especially at high speed, and comparing fairly closely with that of most contemporary US fighters.
It was quickly ascertained that, in general, the handling and control characteristics of the Hayate were superior to those of comparable US fighters and particularly in the low speed regime. The roll rate and turning radius were found to be slightly inferior to those of the A6M5, but control feel was very good; rudder and aileron forces were light, well correlated and produced quick, positive changes of attitude. Elevator forces, although heavier than those of the rudder and ailerons, were not objectionable and progressed with g forces with no apparent lightening. No flat spots or control reversal tendencies were encountered over an IAS range of 74 to 350 mph (119 to 563 km/h). There were little changes in directional trim between 150 and 350 mph (241 and 563 km/h), but the rudder control became extremely sensitive at 300 mph (483 km/h) lAS. sensitivity reducing somewhat at higher speeds.
As previously mentioned, flight adjustable trim was provided for the elevators only and the trim control worked easily, but excessive play at the cockpit end of the device resulted in some difficulties in the initial pre-setting of the tab, although very little trim change was necessary throughout the level flight speed of the aircraft. Only slight longitudinal trim changes occurred with opcration of the undcrcarriage and flaps. The lack of in-flight trimming for the ailerons or rudder did not seem serious, although a rudder trimmer would undoubtedly have improved the Hayate's capabilities as a gun platform. As flown, the Hayate had been rigged with too much right rudder trim and the attendant starboard wing heaviness proved something of a handicap in evaluating stall and handling characteristics accu- rately. However, the stability of the aircraft appeared to be very satisfactory. Yaw tests indicated some lateral oscillation, although not of a serious nature.
The stalling characteristics of the Hayate proved to be quite normal and stall warning occurred early enough to prevent a stall developing if recovery procedure was initiated promptly. In clean condition with power off at 8,000 ft (2440 m) the stall warning consisted of shudder and elevator buffet at 108 mph (174 km/h) IAS. The actual stall, which came at 102 mph ( 164 km/h), proved clean and the Hayate was stable with little tendency to drop off on a wing. and the ailerons and rudder remaining effective well below stalling speed. With the wheels and flaps down and the oil cooler shutters open, but the cowl flaps and canopy closed, the stall warning--occasionally accompanied by severe canopy buffet came at 92 mph ( 148 km/h) IAS and the actual stall occurred at 90 mph (145 km/h) with the nose dropping straight through. Again, there was no indication of instability.
With power on, undercarriage down and full flap, the Hayate did not stall. The rudder became inadequate below 81 mph(130 km/h) IAS and at this speed heading could be maintained
by use of full right rudder and right aileron. The ailerons became inadequate for maintaining altitude below 74 mph (119 km/h). the Hayate yawing left at this speed and then rolling with any further decrease in speed, but control was readily recovered by an increase in airspeed and a slight decrease in power.
Manoeuvrability was good; rolls, loops, Immelmanns and turns being executed with ease at normal speed, although well
co-ordinated manoeuvres proved somewhat difficult owing to the lack of in-flight aileron and rudder trimming. Handling on the approach and during landing was very good, with no undesirable characteristics or ground looping tendencies manifesting themselves, and vision, too, was good during the approach, although less than adequate after the flare was made. After extension of the undercarriage below 160 mph (257 km/h)and the application offull flap at 130 mph (209 kmh), a three-point landing could be satisfactorily executed (with elevator trim set for zero stick force) using speeds of 120 mph ( 193 km/h) over the fence and 110 mph (177 km/h) just off the runway, the actual touch-down being made at 92 mph ( 148 km/h). The Hayate landed easily. with all oleos soft, and was stable during the landing run which was pleasantly short. Crosswind landings could be made comfortably, but the brakes were relatively poor, although rather better than those encountered on the Ki.43-II Hayabusa.
General functioning
The Japanese instruments functioned well and appeared reliable with one or two noteworthy exceptions. The gyro turn indicator appeared to be binding inasmuch as only one-third needle width right or left was the maximum indication obtainable under any attitude or rate of turn; the caging knob was missing (or had been omitted) from the artificial horizon, making it impossible to cage the instrument for aerobatics or to erect the gyro after it had been upset--no gyro erection tendency was apparent in five minutes of level flight after up-setting, and the left fuel gauge consistently read lower than the right hand gauge although the fuel tanks theoretically fed evenly. Control friction was nominal on the ground, with no binding or roughness present, but interference between the auto mixture control and the stick became evident when an attempt was made to apply full left aileron when the mixture control was set normal.
The operation of the Nakajima Ha-45 18-cylinder radial was generally satisfactory throughout the series of flight tests, but while easy to start cold proved somewhat difficult when hot, the externally energized starter apparently having an insufficient torque rating. The engine ran somewhat roughly between 1,400 and 1,600 rpm and between 1,900 and 2,100 rpm, but the engine controls were smooth in operation with positive response. The engine control quadrant friction locks were unreliable, however, and rarely held the controls in fixed position, the auto mixture and supercharger controls creeping and the propeller control tending to vibrate at low rpm positions. Operation of the four-bladed electrically-controlled constant speed Pe-32 propeller was good, although it displayed a tendency to overspeed excessively unless extreme care was taken when power was being applied after a prolonged dive.
The hydraulic system usually worked smoothly but some difficulty was experienced with the hydraulically-operated undercarriage. On one flight, the mainwheels retracted only partway and on another retraction was completed but the up-locks would not engage. On both occasions repeating the cycle of operations appeared to clear the trouble. Prior to the delivery of this particular Hayate to Wright Field, the hydraulic pump had failed completely on one flight with the result that the wheels crept down. The auxiliary hand pump, which was connected to the reserve portion of the main hydraulic tank, worked well and its capacity was such that approximately 100 strokes were required to retract or extend the flaps, but its efficacy in so far as the undercarriage was concerned was not checked. In the event of a complete hydraulic fluid failure, the undercarriage could be unlocked manually and allowed to fall into place, the process being aided by yawing the aircraft until the indicator lights showed that the down-locks had engaged. One poor feature of the hydraulic system was the need to open and shut the by-pass. This had to be opened below 1,200 rpm to prevent the pump from overheating. The electrical system functioned well, with the exception of one instance of generator failure prior to take-off, but the location of the generator switch in the baggage compartment (which could not be reached by the pilot) was poor.
It was concluded from the test programme carried out at Wright Field that Hayate was essentially a good fighter which compared favourably with the P-sIH Mustang and the P-47N Thunderbolt. It could out-climb and out-mananuvre both USAAF fighters, turning inside them with ease, but both P-51H and P-47N enjoyed higher diving speeds and marginally higher top speeds. The light power loading and control forces of the Japanese fighter were to be admired, but it was not so well constructed as its US contemporaries, perhaps reflecting the slipping Japanese production standards at that stage of the war; it was obviously incapable of standing up so well as US fighters under continual usage and it was more demanding on maintenance. It revealed little effort on the part of its manufacturer to render its pilot's task easier or safer--it lacked fire extinguishers and means of emergency escape--but it was a sturdy little warplane and a very dangerous antagonist in fighter-versus-fighter high-g mananuvring combat when flown by a reasonably experienced pilot.
**Test info and data received from magazine AIR INTERNATIONAL, VOLUME 10, NUMBER 1, JANUARY 1976.
[This message has been edited by Nath-BDP (edited 02-14-2001).]
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Originally posted by F4UDOA:
Widewing,
Re-map your charts for sea level where the air density is a constant. If you do a couple of birds will be out of wack with the others. The P-47 and F4U namely.
I'm really not disagreeing with you. But in order to get flat plate drag area you need accurate Cdo numbers. Some of those numbers from AHT are a little suspect considering the speeds they were measured at vary greatly. From about 200 to 250mph in some cases. I have been searching for the NACA report with drag info for American fighters for a long time. If you have any of this please share.
Cdo numbers follow:
Type Cdo Source
P-51B: .0173 (NACA)
P-51D: .0176 (North American)
P-38G?: .0270 (Boeing)
P-38J: .0275 (Lockheed)
P-39D: .0217 (NACA)
P-63F?: .0203 (NACA)
P-63A: .0182 (Bell)
P-47B: .0213 (TAIC)
P-47D: .0221 (Republic)
P-40: .0242 (NACA)
P-61A: .0242 (Boeing)
F4U-1: .0267 (NACA)
FG-1: .0239 (Goodyear)*
F4F-3: .0253 (NACA)
F6F-3: .0272 (NACA)
F6F-5: .0249 (Grumman)*
F2A-3: .0300 (NACA)
*As one can see, there are sometimes differences between NACA numbers and those of the manufacturer. I can't explain why.
Several of these numbers came directly from Dean's book. Some from Bodie's original factory documents (Lockheed and Goodyear) and from various published sources.
In addition to these Cdo numbers, there are several useful reports currently on the NACA server at:
http://naca.larc.nasa.gov/ (http://naca.larc.nasa.gov/)
My regards,
Widewing
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I believe that the purpose of water/methanol injection is to carry more oxygen molecules/unit volume to the ignition chamber.
Voss
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Widewing,
Great drag numbers. Thanks, have always had a hard time with the .0267 Cdo for the F4U-1/FG-1. Considering it's top speed at sea level is 20+MPH faster than the P-47D-30 with less HP it just never seemed right.
Nath,
Dude, do you know how long I have been looking for that report and you just spit it out like it's been laying around somewhere? Unbeliveable! I know Vermillion has been searching for it too. Thanks!!
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There's a couple of other ways to look at it. One is to look at the propeller, it's diameter and rpm numbers and compare to another plane of known capacity (F4u, F6f). I noticed in Nath's numbers (great info!) for the Ki-84, that diameter is 3.1 m (4-blade), turning at 3000 rpm. One piece of missing data is the prop gear ratio. If anyone knows that, please post it! In the meantime, I'll have to assume the gear ratio and power are the same as R-2800 and compare propellers.
I get the following torques (2000 hp):
R-2800: 3890 foot-pounds @ 2700 rpm
Homare: 3500 foot-pounds @ 3000 rpm
Next, I need to convert the 4-blade prop diameter to an equivalent 3-blade as on the F4u and F6f.
3.1 * (4/3)^0.2 = 3.3m
Now, I can compare props directly for diameter, rpm and torque.
Torque goes up with diameter squared, so we need to find an equivalent diameter for equal rpms, using the 3.3m diameter figured above. I'll bring the Homare down to 2700 rpm, so diameter goes up to 3.7m. Compare that to the F4u and Hellcat at 4.0m. I'd estimate that if the prop gear ratio is the same (0.5), that power output is not quite 2000, maybe closer to 1700. Or, if power is indeed 1990, then we're looking at a gear ratio of about 0.54. Anyone got data for that?
[This message has been edited by wells (edited 02-15-2001).]
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Neato thread. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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Nath, tomorrow, I need to write a letter to the USAFM research office. Maybe we can get in there on Friday 3/9. I'm pretty sure they will have the originals for this report.
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FYI guys, about a year ago, I spoke with the Senior Researcher by letter, and then by telephone, at Wright Patterson.
According to him, the USAF Musuem archives contains no flight test data or documents for either the Ki-84 or N1K2-J (any models), even though they have a N1K2-J in their collection.
I also sent a similar request by mail to the Naval Aviation Musuem (who has the only other N1K2-J in the US) and they never replied to me.
But don't let me stop you from asking, you may find something more than I did.
As you guys know, this is one of my favorite subjects. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
*shudders* a 427mph Ki-84?
Scary... VERY scary. In fact it makes our current N1K2-J look like a peewee league football player, in comparison to a NFL linebacker.
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Vermillion
**MOL**, Men of Leisure
[This message has been edited by Vermillion (edited 02-15-2001).]
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Man that is weird, because they tested both planes. I've got some pictures of the Wright Field flight line at the end of the war that would blow your mind. They had one of everything. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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Wouldn't the ratio be one that kept the prop tips below the speed of sound? Say some where in the range of 0.9 the speed of sound?
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Originally posted by Voss:
I believe that the purpose of water/methanol injection is to carry more oxygen molecules/unit volume to the ignition chamber.
Voss
Thx Voss. That is what I'm suspecting.
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go to http://naca.larc.nasa.gov/ (http://naca.larc.nasa.gov/) and search amoung the NACA reports for the ones on nitrous oxide injection, water/methanol injection, supercharging, turbocharging etc... it's all in there.
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you know that 427mph Ki-84....well I live about 5 minutes from where it was tested in middletown Pa. I bet if I rolled down there, they would not have the data anymore. I wouldnt even know who to ask. I also live near the carlisle war college, I once e mailed them about the usaaf and they said I had to get a hold of the usaf.
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Nath-BDP, well done i have only seen excerpts from this report before wtg!
brady
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(http://content.communities.msn.com/isapi/fetch.dll?action=MyPhotos_GetPubPhoto&photoId=nHwCwcDEJznXbXfCxAJfgD0a7w1sDVrWuMP28UBOabRCH339Yvya3KrR2Q8UMjrBJ)
[This message has been edited by brady (edited 02-16-2001).]
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Does anyone know (maybe Mav?) if OCMI at Ft. Huachuca would be willing to assist in tracking down test data of this nature? I know the Army never disposes of useful data, so it has to be maintained somewhere (and yes any USAAF information would have been retained by the Army). Where is another matter, and who to ask? I have always found the Army to be very helpful with research relevant to the USArmy, and especially historical matters. You just have to find the right person to ask.
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Originally posted by Voss:
Does anyone know (maybe Mav?) if OCMI at Ft. Huachuca would be willing to assist in tracking down test data of this nature? I know the Army never disposes of useful data, so it has to be maintained somewhere (and yes any USAAF information would have been retained by the Army). Where is another matter, and who to ask? I have always found the Army to be very helpful with research relevant to the USArmy, and especially historical matters. You just have to find the right person to ask.
Actually, virtually all AAF records were transferred to the USAF in 1947-48. Surviving test data, flight test reports and performance evaluations, can be obtained from the National Archives located at College Park, Maryland. Or, you can visit the Air Force Historical Reasearch Center located at Maxwell AFB outside Montgomery Alabama. ALL AAF WWII records are stored at Maxwell. Microfilm copies are maintained at the National Archives.
You can contact the folks at the AFHRC by phone at:
(334) 953-2395
My regards,
Widewing
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No doubt one of you guys will correct me if needed; but as far as I'm aware, water is never an oxidant, it is in it's self an oxide and hydrocarbon combustion is an inaapropriate reaction to reduce it.
It's a coolant.
Wiether that means increased charge density or anti-preignition I'll leave it to the engine guys to discuss.
I'm very curious about the pressurized coil. True, air is an insulator, but the abscense of that insulator high alt/low pressure)does not mean the remaining interstices have been occupied by a conductor.
It's more likely mechanical defects in the windings (such as bubbles in the resin) were being exhibited.
And another thing...why doesn't the spill chacker thingy work?