Best radial fighter of '42 (1 Viewer)

[HoHun]

Hi Timppa,

>The Finnish State Aircraft Factory wondered the same thing. It suspected that the Curtiss numbers were obtained with a plane that was polished and waxed, antenna, machine guns and all other protruding parts removed.

That's highly interesting background! Maybe Curtiss marketing was indeed a bit optimistic - I don't think the CW-21 had much chance of attaining the advertised 5000 fpm climb either.

>It was found that at 6000-7000m the Curtiss had to use full throttle to keep up with PR Bristol Blenheim using its cruise speed.

Hm, but for which engine version was that observation made? If we'd know the speed of the reconnaissance Blenheim, that might give us another checkpoint for Hawk speeds Which mark of the Blenheim was used for reconnaissance, and how was it equipped (rear turret, nose barbette etc.)?

Regards,

Henning (HoHun)

 

[Juha]

Hello HoHun
Timppa already answered the question Finnish tests vs official Curtiss figures. Of course that was the conclusion of the staff of the State Aircraft Factory, was that the truth, whole truth… I don't know.

BTW have you seen the Curtiss' procure on specs for Curtiss Hawk 75-A, there is a pdf file of one from a Finnish archive/museum/library? One might be even in this site, in manuals section. You can find good Curtiss specs with weight info etc.
For ex at 2582 kg with 1820-G105A 413 km/h at SL, 467 km/h at 2500m (max for low blower) and 488km/h at 5790m.

FAF CUc-502 on 25.6.41 385km/h IAS at 2810m, more Finnish test results flown after major overhauls are in the Fokker D.XXI thread.

FAF H-75As had pilot's back armour until it was removed in 1944 in order to make a/c a bit lighter and so a bit more combative agains new VVS planes. Also the armour plate was too thin to be much use against heavy mg and cannon fire.

HTH
Juha

 

[Marcel]

Some info on the CW.21: Curtiss-Wright CW-21 Demon Interceptor

The CW-21B appeared in the January 1st, 1941 edition of American Aviation where the claim of "greatest climbing plane in the world" and vertical mile in a minute performance were repeated. There seems to be little doubt the CW-21 had excellent climb performance but the claim for an initial climb rate over 5,000 feet per minute is not supported by the data in this article. The author has found no details to substantiate the claim though the prototype CW-21 may have attained a climb rate of 4,800 feet per minute.

Here it might be worth commenting on the claims of an initial climb rate of over 5,000 feet per minute (Curtiss advertising) or even the slightly lower figure (4,500 feet per minute) mentioned in some sources [13]. The figures above show an average climb rate to both 4,000m and 5,000m as well as between those heights of 3,280 feet per minute. If the CW-21 actually climbed at initial rate approaching or exceeding 5,000 feet per minute but averaged 3,280 feet per minute to both 4,000 and 5,000 meters, its climb performance curve would look very strange when graphed out. In order to average 3,280 feet per minute to 4,000 meters after a start of nearly 5,000 feet in one minute its climb rate between 5,000 feet and 13,200 feet would average barely 2,700 feet per minute. The rate would then increase again to 3,280 feet per minute between 4,000 and 5,000 meters. This unlikely scenario appears even stranger when considering that at 5,600 feet the supercharger would bring the engine rating (850 hp at 2,100 rpm) up to exactly the same figures for sea level. In all likelihood claims for an initial climb rate much in excess of 4,000 feet per minute are probably vastly overstated and fail to represent the aircraft's performance under normal operating conditions. On the other hand an average climb rate of 3,280 feet per minute to 16,400 feet would certainly constitute outstanding performance.

The R-1820-G5 was rated at 1,000 hp at 2,200 rpm for take off and its normal sea level maximum rating at 2,100 rpm was 850 hp [12]. Normal maximum rating in first supercharger gear was 850 hp at 2,100 rpm and 6,000 feet and 750 hp at 15,200 feet in high supercharger gear. Curtiss credited the fighter with a maximum speed of 333 mph at 18,000 feet and 314 mph at 5,600 feet. Cruising speed was 282 mph at 12,200 feet. Cruising range was 630 miles. Climbing time to 13,120 feet (4,000m) was 4 minutes and to 16,400 (5,000m) was 5 minutes.

 

[Elvis]

On the subject of the R-1820-G205, I went over to enginehistory.org and took a look and don't even see the R-1820-56 listed. There's a "-55", followed by a "-57".
This may be due to the records belonging to the USAF and not the USN.

However, further investigation shows that there were actually two "-G205" variations of the Cyclone engine that were used by the USAAF.

One is denoted "GR-1820-G205A", with the other as being the "R-1820-G205A".

The "GR..." engine correlates to an R-1820-87.
The "-87" was a 1200HP powerplant with an 11" two-speed supercharger and the engine weight is listed as 1315 lbs.
The "R..." engine correlates to an R-1820-95.
The "-95" was also a 1200 HP powerplant and apparently, based on the "-87" varient, but differing due to accessory drives and cylinder baffles.
It's also interesting to note that this particular varient is listed as (and I quote), "Engine purchased by Norway but taken over by U.S.".
The usage is listed as that for the P-36G (noted as XP-36G, under the "descprition" for the other engine mentioned here).
It also used a two-speed supercharger, although the diameter is not listed, but the ratios are the same (so it could be surmised that this is the same SC used on the "-87").
The engine weight is listed at 1320 lbs.

On the subject of fuel requirements, the "G205..." engines listed above both show a grade of 100/130 as that to be used.
However, the recent mention of Finnish usage of 87 octane fuel is interesting, because in another section on the Cyclone at the enginehistory.org site, it lists a correlation between the R-1820-G5 and the R-1820-39.
The fuel requirement for this 930HP version is listed as 91/96.
It is entirely possible that the engine could "digest" the small difference in octane ratings with no ill effects, and as I see no notes for different HP ratings for that particular varient, power didn't suffer enough to make a difference to plane's (and engine's) overall performance.
However, engine weight is a bit lighter, being listed as 1198 lbs., compared to the later G-205 varients listed above.



Elvis

 

[Elvis]

Marcel,

On the claims for climb rate of the CW-21, I think that if the writer of the article were closely questioned, he would most likely claim artistic liberty for his "mile-a-minute" comment.
The rate equates to a speed of 60MPH, or almost 100 clicks.
At the time, that was considered a fairly "quick" rate of speed to the common American citizen, thus it would give the impression of a "high-performance" airplane, which I feel is the overall feeling the writer was most likely trying to convey.
Thus, whether the fact that the plane could actually climb at 5,280 ft./min., or not, would then be irregardless in this case, as it was not being portrayed as a "fact".
It would be more likely that if the claim were being presented as fact, it would be noted as "5,280 ft./min.", and not "a mile-a-minute".

JMHO.



Elvis

 

[HoHun]

Hi Elvis,

>On the subject of the R-1820-G205, I went over to enginehistory.org and took a look and don't even see the R-1820-56 listed. There's a "-55", followed by a "-57".

Note that there is another overview of Wright engines a bit further down the page, that's what initially confused me too. The second one does include the R-1820-56, but does not have as much detail information as the first.

>One is denoted "GR-1820-G205A", with the other as being the "R-1820-G205A".

Ah, thanks - I had missed that. I agree that the two engines appear to be virtually identical, despite the absence of the supercharger diameter figure in the second dataset (and the typo in the high gear full throttle height for the first).

Regards,

Henning (HoHun)

 

[HoHun]

Hi Juha,

>BTW have you seen the Curtiss' procure on specs for Curtiss Hawk 75-A, there is a pdf file of one from a Finnish archive/museum/library?

No - where can I find it? That would be highly interesting!

(I have some pages from a USAAF technical order listing data for the P-36A, but it sounds like this is a different dataset.)

Regards,

Henning (HoHun)

 

[Ivan1GFP]

Someone may already have commented, but the GR is an engine with a reduction gear up front for the prop. The R is a direct drive by my understanding.

- Ivan.

 

[Elvis]

Yeah, that's what I was thinking too, Ivan.
Thanks for confirming that fact.
-------------------------------------------------

Note that there is another overview of Wright engines a bit further down the page, that's what initially confused me too. The second one does include the R-1820-56, but does not have as much detail information as the first.

Sorry HoHun, I do not see what it is you're referring to.
THIS is the page I've been referring to the whole time we've been using it.
Can you show me where the additional Wright info is on this page?



Elvis

 

[HoHun]

Hi Elvis,

>THIS is the page I've been referring to the whole time we've been using it.

>Can you show me where the additional Wright info is on this page?

Direct link to the one I first referred to:

http://www.enginehistory.org/Wright/CWafter1930_2.pdf

Direct link to the one everyone else referred to:

http://www.enginehistory.org/ModDesig/I3 9.tif

Direct link to superior page that sent us into confusion:

Reference

Good thing you checked the post-war USAF designations - I skipped that page because I was clearly interested in the wartime USAAF! Talk about tunnel vision!

Regards,

Henning (HoHun)

 

[Juha]

Sorry HoHun
if it isn't in the technical section of this forum, I don't have a slightest recollection where I saw it in the net.

Juha

 

[Soren]

The FW-190 IMO.

 

[Elvis]

HoHun,

Thanks for the link.
Guess I'll have to invetigate that site a little closer.

Interesting correlalations between R-1820-56, ...-56WA and R-1820-72A.
All appear pretty much the same, except for production periods.
I wonder what the difference was that changed a "-56" to a "-72"?



Elvis

 

[Vincenzo]

Hi to all

i found a french site with a manual for H-75A-1, i post the link when i back to home, the fighter configuratio weight it´s 2691kg, it´s with the rear tank empty, the speed is 487,5 km/h at 4000 m.

I think the rated altitude under italian standard was different from international ones. for example DB601A-1 in italian nomenclature was rated at 4100 m. but was at 4500m.

 

[Vincenzo]

this is the link Le Curtiss H 75

other: we need add at challengers H-75 C-1 (the french planes fightning in november against the operatio torch)

 

[DerAdlerIstGelandet]

Lets put a visual to it. Poll added (Yeah I know another fricken poll??? Sorry I like them...)

 

[Vincenzo]

i not like

and P-47 is not in challenge

p.s. please if possible remove the poll

 

[tomo pauk]

Hi, Adler,

Perhaps you could make it a multi-choice poll, since the 190 would scoop all the votes? This way we'll see how the other contenders fare (sort of a second-best choice).

 

[DerAdlerIstGelandet]

I can not change it anymore. I did not really think of that. I will remove it.

But why would the P-47 not be included? It was in service in 1942.

 

[Vincenzo]

read first topic "actual fightning fighter"