"Bombing accuracy question" Topic

I am writing some rules for ground attack – low level bombing and am a bit stuck about how much error is involved.

In particular I'm wondering if a pair of bombs could land very far apart or if they'd end up pretty much within a few metres. Given the bombs would be dropped only a hundred or so metres from the target there doesn't seem much scope for random errors taking the bombs very far apart. You could and would still miss by a wide margin but this would be pilot error and would apply equally to the whole stick of bombs.

I have the same question regarding rockets like the RP3 carried by Typhoons.

Cross posting to land and air boards as it seems relevant to both.

All a question of pilot skill and practice. Triggering the bomb(s) and/or rockets at the right height, direction and angle is a skill and a result of practice.

I'd suggest that any supposedly trained unit (UK, British and Soviet) that specialized in ground attack would be pretty good. Other non-specialized units could attack, but would not be as effective.

Nearly everyone strafted targets, but even then you will read about inexperienced pilots flying into the ground or buildings.

Dan

In the rules I'm trying to write most of the 'missing' comes from the player knowing exactly what they want to hit but the pilot not realistically having as much omniscience.

From what I've been able to make out the whole process was rather random, and many weapons were used for area effect rather than for precision strikes.

It seems the best weapons were the MGs/Cannons because they were able to be aimed/adjusted onto the target.

It must be very difficult to hit or get close to the target even with practice under combat conditions. Then you factor in not really knowing where the target is with any precision it becomes a lottery.

Very high attrition for ground attack.
Especially attacking Jerry, because they pretty much had to gear up to disperse and defend with AAA.
Not the sort of stats that would encourage you to get in close enough to hit anything but a very large target.
Post war analysis of effect rates large cannon as the best way to destroy tanks.
Rockets were wildly inaccurate.
If they'd known just how inaccurate I doubt they'd actually have got anyone to run the risk of tank busting.

The answer would be yes. Just because the pilot wanted to release them at the same time does not mean they leave the plane at the same time. Could hang up for mechanical reasons, motion of the plane, wind, could just fall different. Even a fraction of time leaving the plane could translate to quite a distance of missing, or bombs landing a good ways apart.

Is that dive bombing or level bombing?

To add some numbers to illustrate flicking wargamer's point, at a (modest?) speed of 250 mph, the plane is traveling at over 350 feet per second. A quarter second delay results in about 90 feet traversed.

See this TMP discussion on blast radius: TMP link

According to an attachment in the above discussion, the blast radius for a 500lbr (Vietnam era) was ~20 meters lethal and ~60 meters casualty. So, a quarter second delay moves the target out of the kill zone.

Depends upon whether the wings are level, etc. as well, since that could make a difference too.

As mentioned, 15% – 20% losses per sortie for ground attacks, from D-Day and afterwards are not unheard of, not that you asked. However, heavy flak and MG fire could probably affect the pilots' ability to get bombs on target as well.

You should read about the carpet bombing used in the breakout from Normandy in WWII at the start of operation Cobra. 600+ friendly fire casualties as well as killed Lieutenant General Leslie McNair who got a little too close. They had something like a 2000yrd buffer zone.

Thanks guys – lots to think about so far. More still welcome of course.

I was thinking the kind of steep descent bombing used by low level attack aircraft – but nothing like dive-bombing which I think was limited to Stukas (in Europe anyway).

Stukas I've got getting their bombs pretty close to the target – assuming they find the right one! The dive would have reduced error from delayed release and uneven air resistance etc considerably I assume.

Everyone fielded dive bombers – but it's an offensive thing so you don't see it much unless you have both local air superiority and are on the offensive. Plenty of dive bombing on both sides of the Pacific theatre.

Late war designs favoured fighter-bombers with cannon and rockets, but it was still done.

The US deployed dauntless dive bombers in North Africa in 1943. thought it would be interesting Stuka vs Dauntless.

Hopefully John Salt will pick up on this – his latest compendium of War office reports had data on rocket (horrible) and bombing accuracy tests.

If I get a chance tomorrow I will see if i can fire up one of my other computers that has my latest copy of his work.

As I recall the Typhoon had a couple percent chance of hitting a barn let alone a tank.

link

Is this the thing you mean goragrad?

Terry Copp's book on the Canadians in Normandy has details of the RAF's own tests.
"In January 1943 a full scale model of German artillery position with 48 mock guns and 58 dummy soldiers was created. Every effort was made to aid the fighter-bombers, but neither Mustangs strafing, nor Typhoons firing rockets were able to inflict more than negligible damage on the position."
These targets were of course not shooting back.
Post battle operational research confirmed the test results.
"It was found that Typhoon rockets hit a viaduct 500 yards long and 8 yards wide only 1 in 15 times. Bombs dropped from "bombphoons" and Spitfires struck the same target 1 in 82 times. Typhoon rocket attacks on gun positions produced results varying from 110 RP's fired at a casemate in Courseulles-Sur-Mer with 0 hits to 2 hits out of 127 against a similar target . None of these attacks were against well defended targets."
Target identification was another problem. Tests in March 1943 showed that given a 6 figure map reference pilots were unable to spot well camouflaged gun positions even when the guns were firing.
The principle effects of tactical airpower in WW2 were morale and disruption. Troops that had suffered air attack had their morale shaken and attacks were disrupted or dispersed as the troops sought cover. Advances were delayed as they reorganised after the air attack and gun positions attacked had their firing plans disrupted for several hours.

"Is this the thing you mean goragrad?"

No, that is the report on general effectiveness of Tac Air.

There are some more specific reports on accuracy of rocket projectiles.

iirc the CEP (the diameter of the circle within which 50% of munitions will land) for a Stuka was 25m. That was considered astonishingly precise, so I would imagine the CEP for steep angle fighter bomber attacks was considerably larger.

That is a 50:50 chance of landing the bomb within 25m of the target.

Somewhat better than the early RAF night raids where the CEP was measured in miles!, but still fairly poor if trying to hit a hard target like a bunker or a tank.

Weren't RAF Spitfire IXs used for dive bombing missions in Italy. Probably not as steep a dive as specialist aircraft though.

This is a two part problem.
First the detection of the target.

link

Then the actual attack on the target.

Thanks Martin, that is correct.

On Typhoons from the 2006 Salt compendium -

WO 291/2357 Rocket Typhoons.
This report is dated 12 June 1945. The expected probability of hits on different targets using RPs is
given as:
Target Dimensions % hits
Small gun position 5' diameter 0.2
Panther tank 22'6" Χ 10'9" Χ 9'10" 0.5
Large gun position 10' diameter 0.8
Army hut 60' Χ 30' Χ 20' 2.8
Large building 120' Χ 54' Χ 50' 10.0

"Among the hundreds of abandoned and knocked out tanks that have been examined, no instance has been recorded of a tank that has been hit by R.P. and escaped major damage."
RP are very effective on guns (20mm guns are blown to pieces), tanks, barns and huts. Brick houses have a large hole knocked in them and "considerable havoc wrought inside". Anti-personnel effects are limited, as the rocket tends to bury itself, and on concrete structures and thick masonry such as churches the damage inflicted is superficial.
The morale effects of rocket attack appear considerable. Enemy PWs report that all personnel except flak gunners hide from aircraft from 1 to 10 minutes after the completion of an attack, expecting the attackers to return for a second strafing pass. "It appears quite definite that it is the nature of the attack that upsets the Germans and not the physical damage which it causes."
RP Typhoons are also reported to have a considerable heartening effect on friendly troops.

From Salt (VA is vulnerable are) -

WO 291/538 A preliminary estimate of the destructiveness of various projectiles against MT and guns

Projectile Effect on MT// Field guns

25-pdr TNT// No trials;VA probably about
500 sq ft//Small

25-pdr 60/40 Amatol VA about half TNT// Smaller than TNT

95mm TNT// Apparently better than 25-pdr TNT//Better than 25-pdr TNT

4.5"// VA about half 5.5"// Considerably smaller than 5.5"

5.5" 80lb shell// Roughly equal to 100lb// Better than 100lb

5.5" 100lb shell// VA perhaps about 1200 sq ft

2" mortar// Small but unknown// Probably negligible

3" mortar steel bomb// About twice as good as 25-pdr
TNT; VA perhaps 800 sq ft//Small

3" mortar cast-iron bomb// Small but unknown// Probably negligible

4.2" mortar steel bomb //3–4 times as good as 25-pdr
TNT; VA prob. about 1500 sq ft//About equal to 5.5" 100lb shell

20lb 'F' bomb VA probably about 2000 sq ft// VA probably about 150 sq ft

40lb GP bomb// VA probably about 3000 sq ft// Rather better than 20lb 'F'

250lb MC or GP bomb// MC bomb VA of the order of
15000 sq ft//VA 5000 sq ft

500lb MC or GP bomb// MC bomb "slightly better" than
GP bomb//VA 7500 sq ft

1000lb MC bomb //VA probably 20–25000 sq ft //VA 12000 sq ft

The figures for 250lb and larger bombs are based partly on calculations and partly on Prof. Zuckerman's
report on Pantelleria.

For guns in pits the VAs will be about half these figures.

Presumably a square root of the vulnerable area would give the length and width of the zone and then you need to know the accuracy…

As to strafing accuracy, the report is an even bigger hassle to format. May be able to do it later.

The only time I've really successfully dumb-bombed in a flight sim is when I pulled over into a zero-gee inverted dive with the bombsight centered on the target. Dumped 3 loads of that JP233 as I fell, then lit the burners and pulled clear to engage some other target. Heard the thunder of a lot of bombs going off, and then I had the 'mission clear' banner pop up on the HUD. I had apparently hit the sub-carrier (primary mission target) with 3 aircraft's worth of kaboom that all hit at the same time.

It wasn't an accelerated dive-bombing attack, but it worked.

I know that dive bombers were used for two reasons in ship attacks: The first was to increase accuracy, and the second was to increase bomb effectiveness in piercing armor. After all, if you roll into your bombing stoop at close to 350mph, your bomb should be close to the speed of sound by the time it hits!

The bomb won't get to those kinds of speeds even if dropped from enough height to reach terminal velocity. Too much drag.

At dive bombing heights, the dive speed at release is going to be effectively the bomb speed at impact.

So the chance of you being shot down and killed is higher than your chance of hitting that panther with your rockets.
Assuming you can see the thing and you don't mistake a friendly tank for enemy one.

I wonder how many ground attack pilots realised the odds.

It seems those assigning aircraft to missions tended to put most aircraft on 'armed recce' rather than close support because the rate of return was greater in terms of disrupting supply etc.

It makes me wonder how much all the money spent building A-10s and similar aircraft and training up the crews would be wasted if they ever had to face a modern army with proper air defense close up to the FEBA….

As overbuilt as the A10 is, it has a pretty good survival rate for running into 'Steel Rain' air defenses (that is, a bajillion guns all pointed skywards)

Remember that it's designed to take hits from a 57mm AA gun, not to mention the various IR-guided missiles.

But really, I don't think any CAS (fixed-wing or rotary wing) can happen without at least local air superiority.

Apologies for coming to this late.

I believe this is the strafing accuracy bit goragrad referred to:

WO 291/1345	Film Assessment of Ground Strafing
Only 12 to 18% of the camera gun film for December to March
1944-45 was good enough to be used for assessment.  It was
stated that a gun-camera arrangement like that used by the
Americans would be preferable, as the current equipment stopped
filming as soon as the guns stopped firing, and so did not
record the impact of rounds then in flight.  The aircraft
involved in this assessment were Spitfires, Typhoons and
Tempests of 2 TAF attacking MT and locos.  Their shooting was
analysed into percentages as follows:
Code	Assessment							Loco	MT
A	Very good shooting, steady aim and many hits			7	3
B	Good shooting, steady aim during part of attack, some hits	35	29
C	Poor results, bad harmonisation suspected			1	1
D	Bad shooting, aim sweeping across target			17	17
E	Incorrect deflection for moving target				½	4
F	Side to side motion						1	3
G	Shallow dive, inaccurate aim					4	6
H	Steep dive, closing range too long				4	7
I	Closing range too long						½	-
J	Opening range too long						13	11
K	Short duration of fire						9	10
L	Too much bank							5	3
M	Wander of aim							3	6
Code B implies at least 1 second's worth of hits.
Visible results were:
			Locos		MT
Serious damage	        42%		32% (probably destroyed)
Some damage		46%		47%
No hits			12%		21%
Bursts fired varied from under 1 to over 10 seconds in
duration, with an average of 2.9 secs on locos and 2.5 secs on
MT.  The number of bursts is usually 1 or 2, sometimes 3 or 4
or even as many as 7 short bursts, which is unlikely to be
successful unless exceptionally accurate.
"Successful" pilots used the following:
				Loco		MT
Opening range, yards		600–800	     500–700
Closing range, yards		250–350	     250–350
Duration of fire		1½–3½	     1–3
Dive angle			10Ί–20Ί	     10Ί–20Ί
1,000 yards is too far to open effective fire.

This might be useful, too:

WO 291/811	Attack of army targets by fighter support
Dated 20 Apr 1945.  Air weapons considered are:
20mm HE/I fuzed 254 Mk IV
20mm SAP/HE/I
30mm Mk 108 German shell with "sensitive fuze"
6 pr HE Mk 1T fuzed 257 Mk II (instantaneous) or 244 Mk V (delay)
60mm Motley rocket fuzed 254 Mk II
60lb S.A.P. 3" rocket fuzed 865 Mk I (delay)
Attack of dispersed targets: Area of effect (thousands of square feet) per attack per aircraft.
Projectile	Rds		"Hard ground"			"Soft ground"
		per 	Disp.	Soft 	Armd 		Disp. 	Soft 	Armd 
		attack	 troops	tpt	tpt	Guns	troops	tpt	tpt	Guns
20mm HE/I/T	120	30	6	1	2	4	6	2.5	2
20mm SAP/HE/I	120	1	3.5	2.5	2	1	3.5	2.5	2
30mm (3 guns)	63	60	10	1	4	30	6	1	4
6 pr HE	4	4	3	1.5	1	4	1.5	1	1
60mm rocket	72	140	45	20	15	15	15	4.5	15
60lb SAP rocket	8	70	50	25	8	8	8	3	8
Attack of single targets: Expected effective hits and near misses per attack per aircraft.
Projectile	Hits per		"Hard ground"		"Soft ground"
		10 sq. ft.	Soft	Armd	Guns	Soft	Armd	Guns
				tpt 	tpt		 tpt 	tpt
20mm HE/I/T	32		5	1	1.5	5	1	1.5
20mm SAP/HE/I	32		3	2	1.5	3	2	1.5
30mm (3 guns)	18		9	0.6	3.5	6	0.6	3.5
6 pr HE		1.3		3	1.5	1.5	1.5	0.9	1.5
60mm rocket	0.77		1.5	0.8	0.5	0.5	0.25	0.25
60lb SAP rocket	0.045		0.9	0.4	0.15	0.15	0.06	0.15
"Of the weapons not at present in general use the 30mm shell (German) shows a marked 
advantage against dispersed troops on the assumptions made in this memorandum.  The 
60mm rocket being projected in larger number gives a greater chance of hitting, and
therefore of damaging light targets than the 60lb S.A.P. rocket.  Against tanks 
the 60lb S.A.P. has no rival."
"There can be little doubt that the moral effect of rockets is at present considerably 
greater than that of cannon, in both improving the morale of our own troops and 
depressing that of the enemy."
"The value of a weapon against a particular target depends very largely on the fuzing." 
Quicker fuzes are better against dispersed troops. Delay fuzes are preferable against 
vehicles in the case of hits, but may result in a largely buried
projectile and negligible fragmentation on soft ground.  If hits are unlikely to be 
scored, a quick fuze can be  used, relying on fragments to do damage, but these have 
no effect on heavy armour. The German "sensitive" fuze is assumed to be instantaneous.
The results listed under "hard ground" assume that all fuzing differences have been 
eliminated, that is, no projectiles have their fragmentation reduced by burying themselves. 
"Soft ground",  which "may be regarded as the normal case", is calculated to allow for
only 1 in 10 delay-fuzed projectiles giving effective fragmentation.

And there's a bit about incendiary tanks:

WO 291/780	Jettisonable petrol tanks used as aerial bombs
This paper is based on US trials and operations in  the Pacific, and refers to what we should now
call napalm tanks.
The weapon is described as a 165-gallon wing or belly drop tank, as fitted to the US P-47, filled
with thickened petrol, and the filler cap modified to hold a WP grenade with an all-ways fuze.  For
use over water, a sodium grenade is used.
At 300 mph, 6° glide angle, from 100 feet, the pattern produced is elliptical, 250–300 feet long from
the point of impact and 60–100 feet wide.  Burning time is 5–10 minutes.
"Targets recommended by the Americans are: men in slit trenches, hutments, wooden piers,
Japanese bunkers and undergrowth concealing defensive positions".
"Moral effects are extremely difficult to assess and may become much less important as the enemy
becomes accustomed to flame attack.  At present the moral effect of attack by flamethrowers is
considerable.  'Enemy resistance ceases when enough flame is used, irrespective of casualties.'"
(the quote is from "Gas smoke and flame warfare in France", Report 4W/161/1 of No. 4 Chemical
Wing, CTS.)
Effect on troops in slit trenches:  If the fuel is evenly spread over a 250Χ60 ft pattern, 95% of slit
trenches in the area will be neutralised for at least 30 seconds (experienced troops), and 65%
untenable unless casualties are accepted (second degree burns).  The vulnerable area of 1000lb MC
or GP HE bombs is given as 4,000 to 8,000 square feet, depending on the type of bomb and whether
men are crouching or standing in their trenches.   The vulnerable area of the petrol bomb is 12,000
square feet, regardless of posture.  "Air burst HE bombs are much more effective, but can only be
used in high-level attacks."
The effect on pillbox embrasures is not considered great.  Attacking with the wind behind is
recommended, so that flame and smoke will be blown into the embrasure, but the amount of fuel
introduced into the embrasure will not be great — less than a gallon, the minimum considered
necessary to be effective.  Still, it is stated that "The moral effect of being completely enveloped in
burning petrol for 30 seconds should be considerable."
Effectiveness against transport targets is shown by the following table, comparing vulnerable areas
for the 156 gallon (1000lb) drop-tank and 1000lb MC HE bomb, in thousands of square feet:
Bomb	Damage category
	A	B	C
HE	80	20	3*
Petrol	12	12	12
* = "Reports from theatres of war indicate that this figure (derived from trials) is too low, 
the risk of fire having been underestimated."
Damage categories are defined as:
A	Vehicle stopped, repairable by driver.
B	Repairable by workshop.
C	Unserviceable.
The amount of undergrowth cleared by different means, in square feet cleared per lb of munition, is:
Agent			Area cleared
2000lb bombs		8
Petrol gel		10
Plant poison		300
"It was found that 2000lbs was the minimum weight of HE bomb that could be used; smaller bombs
created more cover than they destroyed."
The report concludes that petrol is better than HE against personnel in slit trenches and massed soft
transport, and similar in performance for clearing undergrowth and against pillboxes, although
flame may have more neutralizing effect.  Finally, the following advantages when used in close
support of infantry are mentioned:
1. The way casualty effects fall off very rapidly at the edge of the area of effect means that troops
can follow up more closely.
2. The effect of the bomb is almost entirely forward of the point of burst.
3. Effects persist for 5–10 minutes, giving the infantry more time to get up from the bomb line.
4. There is no cratering.  Obscuration by smoke may either help or hinder, depending on the tactical
situation.

Thanks very much – just the sort of stuff I need.

One thing to bear in mind if looking at the RAF at least is that individual Typhoon squadrons were trained/equipped for either RPs or bombs, not both. Now obviously with pre-planned strikes, the squadron selected might (on a good day at least!) be one with the weapon judged most appropriate for the target set. But one presumes that for cab rank taskings, etc, you got the aircraft currently available, rather than specifically RPs or specifically bombs.