Dive bomber accuracy in perspective.

[Geoffrey Sinclair]

RAF Performance figures,

Martlet I, 310 mph at 14,500 feet, ceiling 32,000 feet, 136 gallons of fuel, 29 gallons used for warm up and climb etc. 690 miles at 257 mph, 2.7 hours, at 15,000 feet. Alternatively at 165 to 175 mph, 845 miles, 5 hours. Normal weight 6,835 pounds

Hurricane I, 320 mph at 17,500 feet, ceiling 30,250 feet, 97 gallons of fuel, 19.4 gallons used for warm up and climb etc. 454 miles at 275 mph, 1.7 hours, at 15,000 feet. Alternatively at 180 mph 580 miles, 3.35 hours. Normal weight 6,629 pounds, De Havilland propeller. The Rotol propeller was around 100 pounds lighter and gave better take off and ceiling.

 

[SaparotRob]

I'm surprised the Wildcat had a higher ceiling than the Hurricane.

 

[WARSPITER]

I'm surprised the Wildcat had a higher ceiling than the Hurricane.

It needed to because the pilots helmets were taller.

 

[Wild_Bill_Kelso]

I'm surprised the Wildcat had a higher ceiling than the Hurricane.

Two stage supercharger (at least on F4F versions)

 

[Shortround6]

Two stage supercharger (at least on F4F versions)

And this where confusion starts.

The Martlet I were the ex French aircraft that were powered by the same 9 cylinder radial engines that were used in the F2A-2/3 Buffaloes. Engine makes it's re-appearance in the Martlet IV in July of 1942.

Martlet II & III (start production March of 1941) used the 14 cylinder R-1830 by P & W. except it is a two speed single stage engine just like the engines used in the F4F-3A.

The British don't get a Martlet with a 2 stage engine until the Martlet V Which started showing up in Dec 1942 and most or all were built by Eastern Aircraft.

The Marlet VI/Wildcat VI shows up in 1944 and is the same (mostly) as an FM-2 with it's single stage, two speed Wright 9 cylinder R-1820 engine.

Please note that 136 imp gal of fuel is an indicator that the plane does not have self sealing fuel tanks or was rebuilt/modified to have an external coating (?).
Martlets/Wildcats with US built/supplied protected tanks had about 120-122 Imp gallons of internal fuel.

Out of the 1082 Wildcats built for/acquired by the British, 311 had two stage superchargers.

 

[Wild_Bill_Kelso]

That's interesting, and might explain some difference in reported loiter time (per 'armouredcarriers') between some of the early British Martlets and F4F-4 anyway. Ten percent more fuel could make a bit of difference. If it's an unprotected fuel tank that is potentially a notable downgrade in combat effectiveness, external coating is still at least some protection.

 

[RCAFson]

The Skua as 'Fleet Defender'. During the 1940 Norway campaign the Skua downed the following aircraft via front gun kills:

Do 26 Flying boat - 1.
Dornier 18 flying boat - 3.
Heinkel 115 floatplane - 2. (10 more by strafing)
Heinkel 111 bomber -17.
Junkers Ju 88 - 5

(verified by Cull et all by cross referencing Luftwaffe loss records and operation reports)

 

[RCAFson]

Speed is not the definitive be all of fighter combat. The A6M was quite a bit slower than many contemporary fighters, but proved to be a deadly adversary thanks to its agility and good climb rate.
The Fulmar was what it was, a variant of a light bomber and proved unable to compete with the Bf110, let alone the Bf109. It was not only slow and docile handling, but also had a terrible climb rate. It struggled to deal wit many bombers.
By comparison, the SBD was a very agile aircraft, relatively well armed, 2 x .50's up front are much more lethal than 8 x .303's, and had a decent climb rate, not far short of the F4F Wildcat.
The SBD was certainly able to hold its own against the fearsome A6M, a plane that had no problem sweeping the Fulmar aside.

The Fulmar had a positive kill ratio vs the Me110. The Fulmar II's climb rate to 10K ft wasn't that bad (7.1 minutes) , using Normal climb power, and could be increased considerably by using Combat Power.

SBD's made lots of front gun claims against Zeros in 1942, but, according to Lundstrom, only one was verified by IJN records, IIRC.

 

[Wild_Bill_Kelso]

The Skua as 'Fleet Defender'. During the 1940 Norway campaign the Skua downed the following aircraft via front gun kills:

Do 26 Flying boat - 1.
Dornier 18 flying boat - 3.
Heinkel 115 floatplane - 2. (10 more by strafing)
Henkel 111 bomber -17.
Junkers Ju 88 - 5

(verified by Cull et all by cross referencing Luftwaffe loss records and operation reports)

Are those claims or cross-verified?

Per another debate i was having upthread with Shortround6, this is exactly what the job of the Skua was. Same for Fulmar. Perfectly adequate for defending the fleet far out to sea against long range attacks from planes like this. I would say that of that list the Ju 88 victories are particularly impressive since a Ju 88 should be able to outrun a Skua in theory, though not always in practice.

 

[RCAFson]

Are those claims or cross-verified?

Per another debate i was having upthread with Shortround6, this is exactly what the job of the Skua was. Same for Fulmar. Perfectly adequate for defending the fleet far out to sea against long range attacks from planes like this. I would say that of that list the Ju 88 victories are particularly impressive since a Ju 88 should be able to outrun a Skua in theory, though not always in practice.

Those were verified kills by cross referencing Luftwaffe records.

Acting as a fighter was secondary to it's intended role as a dive bomber, but 4 x forward firing .303 Brownings at 1200rpm/gun and 600RPG gave it lots of fire power. The Gloster Sea Gladiator was the fleet's dedicated fighter at the time and the SG scored a similar number of verified kills, IIRC.

The fleet was typically not that far out at sea. The RN and FAA benefitted from some of the first long range naval AW radars and were able to put together a rudimentary Radar GCI system fairly quickly.

 

[Wild_Bill_Kelso]

Those were verified kills by cross referencing Luftwaffe records.

Acting as a fighter was secondary to it's intended role as a dive bomber, but 4 x forward firing .303 Brownings at 1200rpm/gun and 600RPG gave it lots of fire power. The Gloster Sea Gladiator was the fleet's dedicated fighter at the time and the SG scored a similar number of verified kills, IIRC.

The fleet was typically not that far out at sea. The RN and FAA benefitted from some of the first long range naval AW radars and were able to put together a rudimentary Radar GCI system fairly quickly.

My point is that this specific role for some dive bombers, as a 'secondary fighter', works so long as they are beyond the range of the top land based fighters. In Europe when the Skua was still flying, that would be Bf 109. I think most of the time particularly up north they were far enough to be safe from Bf 109s. I don't think Skua's could handle Bf 109s.

But they certainly handle an He 111 or He 115 or a Fw 200, and apparently even Ju 88s, all of which can wreck convoys if there is no fighter protection.

 

[Zipper730]

CEP assumes a Rayleigh (2 dimensional circular) probability distribution, so if you're putting 25% within 30 meters, you should expect to put 50% within 1.552 * 30 = 46.6 meters.

How does one calculate a Rayleigh probability distribution

 

[GregP]

How does one calculate a Rayleigh probability distribution

It's a chi distribution with 2 degrees of freedom.

 

[Zipper730]

GregP

I mean, is there any formula that's written down for that?

 

[eljefe]

GregP

I mean, is there any formula that's written down for that?

Standard Rayleigh distribution, so sigma = 1. We don't know what the standard deviation is, so I just put in numbers until I found that x = .5364 gave a cumulative probability of 0.25, and x = .8326 gave a probability of 0.5. 0.8326 / 0.5364 = 1.552, so 1.552 x 30 meters = 46.6 meters.

A real mathematician could probably back out a standard deviation from P = 0.25 @ 30 meters, but I'm too lazy to do that.

Cumulative Distribution Function of a Rayleigh Variable

Calculate the cumulative distribution function of a Rayleigh random variable (distribution).

solvemymath.com

 

[Barrett]

Ju-87 with average pilot had a 25% chance to place 1,000kg bomb within 30 meters of target.

Ju-88 under test conditions (presumably expert pilot) could place 50% of bombs within 50 meter circle.

What accuracy could be expected from a Vietnam era Skyraider with 2,000 lb iron bomb?

What accuracy could be expected from a modern day A-10 with 2,000 lb iron bomb?

In researching my original SBD book (Naval Institute 1976) I found a 4th Marine Air Wing study comparing SBD and F4U bombing accuracy. Corsairs were surprisingly close to the Dauntless figures, though I don't recall specifics.

We never considered diving our Dauntless (an A-24B restored as an SBD-5) because the original seals were 30 years old by then. The pilot's manual said: THE SBD-5 AIRPLANE WILL NOT MAINTAIN LEVEL FLIGHT WITH THE DIVE BRAKES EXTENDED.

Roger that!

 

[Reluctant Poster]

In researching my original SBD book (Naval Institute 1976) I found a 4th Marine Air Wing study comparing SBD and F4U bombing accuracy. Corsairs were surprisingly close to the Dauntless figures, though I don't recall specifics.

We never considered diving our Dauntless (an A-24B restored as an SBD-5) because the original seals were 30 years old by then. The pilot's manual said: THE SBD-5 AIRPLANE WILL NOT MAINTAIN LEVEL FLIGHT WITH THE DIVE BRAKES EXTENDED.

Roger that!

I posted this USN study on dive bombing accuracy a while ago

Fairey Battle: Performance and Tactics

Accuracy is a relative term. The attached study by the US Navy is eye opening.

ww2aircraft.net