Effectiveness Of Straffing Aircraft Against Ships

[shep854]

Since .50s and 20s are central to this thread, a bit of background on why the US seemed to be so wedded to the big Browning:

http://www.quarryhs.co.uk/US404.htm

The Hispano-Suiza HS.404 20 mm Aircraft Gun in US Service

[rmgill]

How would 8 or 10 x 0.50s compare to 4 x 20mm Hispanos + 6 x 0.303 or 4 x 0.50 in the anti ship role?

How are the 20mm fuzed? How wold they deal with armor or splinter shields? Aircraft fuselages are going to handle the impacts differently than mild steel hulls and several layers of ship compartments. I can see fast fuzed 20mm impacting on the 1st compartments of the ship and detonating there but not getting to the vitals.

[Markus Becker]

What you said. A 20mm HE shell with an impact fuse will blow a hole into the (by comparison) very flimsy structure of an aircraft but it won't penetrate anything solid. Like the steel plating of a ship. Rifle caliber bullets have a limited armour piercing performance at best. More info is on Tony's website.

 

To give you an idea on how vulnerable DD were. In 1935 the USN usued up two Clemsons and concluded that bombs as small as 100 lb and exploding as far as 40 ft away would cause "very considerable damage" and that strafing with .50 bullets "would quite suffice to disable ships whose only protection were 1/4" gun shields".

[JWB]

Those 20mm HE shells were designed to shred aluminum aircraft skin. To cause significant damage against steel plate requires much larger projectiles. Like 40mm. In fact those B-25s might have been more effective armed with a pair of 40mm guns instead of a single 75.

[Chris Werb]

The 20mm would probably be significantly better at flak suppression as a 0.50 has an ECR of 0.25" and a 20mm HE presumably a few yards for fragmentation plus the effect of blast on gunner's aim. Vs hull plating, how they were fuzed would, as Ryan stated, make a huge difference, Then again one that fully penetrated the plating would be useless for flak suppression, unless it went through a gunshield. Circumstantial evidence does show lots of explosions on ships shot up by Beaufighters which would lead me to believe ammunition was point detonating or similarly fuzed. Would a 20mm on a Beaufighter have been loaded purely HE/HE-T or would there have been a mix of projectiles? The Beaufighter's 20mm guns had 240 rpg vs 500 RPG (IIRC) for the B-25s nose mounted 0.50s.

[Dawes]

USAF used to have a 20mm round called the M95 AP-T for use against armored targets. The projectile was simply a solid slug made from bar or forged steel. Not sure if it saw much use (in Vietnam, if anywhere) and it was withdrawn from use probably after the war.

Edited May 11, 2019 by Dawes

[Chris Werb]

I recall reading that the 0.50 M8 API was a big leap forward in effectiveness - it wasn't as penetrative as a dedicated AP round, nor as likely to ignite as a dedicated incendiary, but it put the incendiary sufficiently deeply into a (robust or lightly armoured) target, which made all the difference.

[DougRichards]

We should also remember how new the high velocity 12mm - 20mm technology was in the lead up to WW2. The Becker Type M2 20mm gun only went into production in 1916, and in many ways was a weapon looking for a purpose. The light construction of most WW1 aircraft really only needed rifle calibre rounds to bring down. The 12mm - 13mm rounds being developed were mainly for anti-tank use, once again, not in service until 1916.

 

So, effectively, in a space of 20 years a wide range of guns and ammunition was developed that previously not been used, and in many ways did not have a target (for naval purposes 45mm was really the minimum calibre for anti-torpedo boat work, and if two ships had come in machine gun range of each other then something either very serious or strange had occurred.

 

Having said that the requirement for aircraft to even strafe ships was probably invented by Billy Mitchell as part of the June - July 1921 tests.

 

Going on just 20 years, the Douglas Dauntless had two .50cal forward, whilst the later Helldiver went to 20mm. The Skyraider also had 20mm, which would tend to indicate that the USN, the most experienced navy in attacking ships, had decided that 20mm was better than .5cal. Of course the Grumman Avenger had .50cal.

[Dawes]

Regarding strafing, a historical report on DTIC related some interesting facts about the M56 20mm HEI round. This round was used extensively in Vietnam for strafing. It was fitted with the M505 point detonating fuze which had a rather blunt aerodynamic shape. This design (standardized in 1955) was seen as acceptable for combat at high altitudes where it's blunt shape wasn't an issue in the thinner atmosphere. Strafing at low altitudes in Vietnam, this round was slowed down to the point where it had functioning problems at ranges over a mile.

[Chris Werb]

We should also remember how new the high velocity 12mm - 20mm technology was in the lead up to WW2. The Becker Type M2 20mm gun only went into production in 1916, and in many ways was a weapon looking for a purpose. The light construction of most WW1 aircraft really only needed rifle calibre rounds to bring down. The 12mm - 13mm rounds being developed were mainly for anti-tank use, once again, not in service until 1916.

 

So, effectively, in a space of 20 years a wide range of guns and ammunition was developed that previously not been used, and in many ways did not have a target (for naval purposes 45mm was really the minimum calibre for anti-torpedo boat work, and if two ships had come in machine gun range of each other then something either very serious or strange had occurred.

 

Having said that the requirement for aircraft to even strafe ships was probably invented by Billy Mitchell as part of the June - July 1921 tests.

 

Going on just 20 years, the Douglas Dauntless had two .50cal forward, whilst the later Helldiver went to 20mm. The Skyraider also had 20mm, which would tend to indicate that the USN, the most experienced navy in attacking ships, had decided that 20mm was better than .5cal. Of course the Grumman Avenger had .50cal.

 

Some Corsairs had 4x20mm cannon and some Hellcats 2x20mm cannon + 4 x 0.50 mgs. Most Bearcats had 4 x 20mm and the Tigercat 4 x 20mm + 4 x 0.50 mgs.

[MiloMorai]

RAF Costal Command flew AA suppression and attack a/c against ships. There was a reason pilot head armour was greater than 1/4"' thick which was the typical thickness of ship hulls (destroyer and under size).

[Stuart Galbraith]

There is good thread on here showing B25 armament options. Interesting to see one fitted with rocket pods normally seen on a P47, not something Id seen before.

https://ww2aircraft.net/forum/threads/b-25-weapons-thread.10766/page-8

[rmgill]

Forward firing rockets is interesting, especially in the rotary launcher in the nose.

[Chris Werb]

I was always dubious about the 75mm and it doesn't surprised me that they removed it from aircraft and sometimes replaced it with yet another pair of 0.50s. It also surprises me that the single 20mm + 8 0.50s in the nose version was not more widely known in recent years as multiple airframes were thus fitted. The rotary rocket launcher is indeed interesting!

[17thfabn]

It also surprises me that the single 20mm + 8 0.50s in the nose version was not more widely known in recent years as multiple airframes were thus fitted. The rotary rocket launcher is indeed interesting!

 

 

I had not heard of widespread use of 20 mm guns on U.S. B25 gunships.

[shep854]

Ive never heard of any 20mm in B-25s. P-38s had one with 4x.50, and the P-70 (night interceptor version of the A-20) had four 20s, but no Mitchells.

Edited May 13, 2019 by shep854

[DougRichards]

I wonder how useful the P-61 radar would have been in the air to surface role? A variant of the radar was tried for surface to surface on British MGB and found to be useful.

 

A Black Widow coming up at night on a Japanese destroyer (without radar) should have been able to wreak some havoc on board the ship with just its 20mm guns, and the possibility of using six 5 in (127 mm) HVAR unguided rockets under the wings should not have been discounted.

[shep854]

Radar equipped Catalinas (Black Cats) were fairly successful running night missions in the Pacific, using bombs and torpedos. Remember strafing couldn't actually sink a ship. It was just to soften the target up for a bombing or torpedo run; at night, flak suppression was not as critical, since few Japanese ships had radar and a darkened plane could usually get into a drop position fairly easily.

Even with radar, the US Navy had great difficulty with Japanese night strikes. During some early night engagements, US ships were instructed to hold fire, to avoid pinpointing themselves to marauding Japanese bombers

From Wiki, 'Battle of Rennell Island':

" At 20:08, Giffen ordered his ships to reverse direction, to slow to 15 kn (17 mph; 28 km/h), and to cease firing their anti-aircraft guns. The absence of muzzle flashes concealed the ships from the Japanese aircraft, who all departed the area by 23:35."

https://en.wikipedia.org/wiki/Battle_of_Rennell_Island

Edited May 13, 2019 by shep854

[Stuart Galbraith]

Biggest problem I see with night strafing is ending up in the drink, particularly in an era before accurate altimeters and night vision goggles.

 

I guess you could rig up leigh light as they did on the liberators. Kind of going to make you a bit obvious for gunners though.

 

I thought the 20mm was interesting too. I suppose they got them surplus off P38's?

 

 

Have a pick through that site fellas, its got a LOT of interesting documents, including Luftwaffe operators manuals for a variety of aircraft. Lots of good stuff on there if you know where to look.

Edited May 13, 2019 by Stuart Galbraith

[seahawk]

The 37mm armed Stukas were quite effective against ships.

[Markus Becker]

Biggest problem I see with night strafing is ending up in the drink, particularly in an era before accurate altimeters and night vision goggles.

 

Well yes, you would have be to very, very careful even when there is some light from the stars and the moon.

 

 

shep854 wrote: Radar equipped Catalinas (Black Cats) were fairly successful running night missions in the Pacific, using bombs and torpedos.

 

 

Bombs? I thought they just laid mines.

[rmgill]

There was a WWII era Radar Altimeter at the time.

The RT-7 / APN-1. Fitted to B-24s at least. Indicated 50-300 feet.

Apparently also in the "TBM Avenger (see image from TBM Flight Manual), dive bomber SB2C Helldiver, patrol aircraft PV-1 Ventura, PV-2 Harpoon, PBY Catalina, PBM-5 Mariner, and PB4Y Privateer. "

https://aeroantique.com/products/radio-altimeter-altitude-selector-switch-sa-1-arn-1-for-radio-set-an-apn-1?variant=6185153069086

http://thepastpresented.com/index.php/tag/rt-7-apn-1-radar-altimeter/

Edited May 13, 2019 by rmgill

[MiloMorai]

Markus, https://youtu.be/2xMbz5vHioM

[shep854]

Markus, https://youtu.be/2xMbz5vHioM

Beat me to it!

To keep on thread, 20mm on PBY

[Nobu]

Strafing warships might be beneficial in certain instances under a certain set of conditions, but otherwise seems like the wrong choice of tool for the job in various ways.

 

Bombers swinging around for a second low-altitude pass to strafe warships after dropping bombs or releasing torpedoes in their first sounds like a good way to increase bomber aircrew attrition and decrease the ammunition available to defend themselves against enemy fighter attack on the return leg.

 

Fighters dropping down to the deck to strafe warships expose experienced fighter pilots to interlinked warship AA fire, and put them out of position and out of ammunition to perform their primary mission.

 

If Bf109s could have sunk or disabled a RN destroyers in confined waters by strafing alone, the question becomes why they did not do so with greater efficiency the week of May 27 1940.

 

During the Battle off Samar, Wildcats strafed the Japanese cruisers and battleships in desperate attempts to distract them from the jeep carriers of Taffy 3

 

Describing unrelenting airstrikes conducted by carrier air against IJN surface ships without fighter protection as "desperate" certainly adds a layer of heroic theater to the battle. Whether justified, based on the supremacy of airpower vs surface gunnery in the Pacific at this time, is another matter.

Edited May 13, 2019 by Nobu