B-29 Defense from attacks below.
xvader
attacks from underneath?
More specifically, how were the two lower turrets aimable for attacks
from below, if the sighting stations were only at the front, two side
and top blisters?
I am curious as the Japanese had fighters with "schrange muzak" type
arrangements with upward firing guns and would have wreaked untold
havoc from the seemingly undefended ventral position.
Would love to hear from some B-29 experts.
Cub Driver
>I am curious as the Japanese had fighters with "schrange muzak" type
>arrangements with upward firing guns and would have wreaked untold
>havoc from the seemingly undefended ventral position.
Well, the major problem the Japanese interceptors had was that their
planes could scarcely operate at the B-29's maximum altitude, and
their guns were relatively ineffective until they mounted 37-mm
cannon. Of course, the 29s flew lower most of the time, since max
altitude wasn't very useful for them, either, since they couldn't hit
much from altitude.
Ramming seems to have been one of the more effective Japanese tactics,
Oblique 20 mm cannon on the Ki-46 Dinah were judged ineffective.
Ki-44s were fitted with up to 40 mm wing guns but weren't very
airworthy thus equipped.
See Japanese Army Air Force Aces by Henry Sakaida
http://www.danford.net/sakaida.htm
all the best -- Dan Ford (email: webm...@danford.net)
see the Warbird's Forum at http://www.danford.net
Vietnam | Flying Tigers | Pacific War | Brewster Buffalo | Piper Cub
tscottme
xvader <xva...@hotmail.com> wrote in message
news:bb0062e5.02071...@posting.google.com...
> Were the two lower turrets of the B-29 able to defend the bomber from
> attacks from underneath?
>
> More specifically, how were the two lower turrets aimable for attacks
> from below, if the sighting stations were only at the front, two side
> and top blisters?
>
The gun turrets on the B-29 were remotely aimed. I suspect that between
the turrets and the tail gunner all aspects were defended.
Brooks
The GE fire control system on the B-29 allowed for various positions to have
primary and alternate control of the various gun turrets, depending upon
how the primary fire control gunner (located in the top rear blister, IIRC)
set his switches in response to requests from the gunners. The side blisters
afforded pretty decent views of aircraft approaching from below and to the
rear, the tail gunner had a good view of the low approaches from the rear,
and the folks up front (bombadier?) had a good view of the frontal low approaches.
The lower gun turrets could be controlled from these various positions. Unlike
the early B-17s and B-24's, I am not aware of any real "blind spots" in the
B-29 defensive coverage (this info from my father, who was a left blister
gunner in the 314th BW).
Brooks
>
>
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Emmanuel Gustin
news:n3r7ju8hh0jeqjlav...@4ax.com...
> Oblique 20 mm cannon on the Ki-46 Dinah were judged
> ineffective.
The Ki-46 was armed with an oblique 37 mm Ho-204. It
also had two 20mm Ho-5 cannon, but these fired forward.
The Dinah was too lightly constructed and had a too low
rate of climb to be a successful interceptor.
> Ki-44s were fitted with up to 40 mm wing guns but
> weren't very airworthy thus equipped.
The 40 mm Ho-301 was light for a gun of its calibre.
But its muzzle velocity was unacceptably low, even for
intercepting bombers: Just 245 m/s. Rumours about
20-mm and 37-mm cannon on the Ki-44 are unproven.
--
Emmanuel Gustin <Emmanuel.gustin -@- skynet.be>
Military Aircraft Database, Fighter Guns Page on
http://users.skynet.be/Emmanuel.Gustin/
Emmanuel Gustin
news:bb0062e5.02071...@posting.google.com...
> More specifically, how were the two lower turrets aimable for attacks
> from below, if the sighting stations were only at the front, two side
> and top blisters?
From the side blisters the gunners could look and aim downwards.
But not straight down, that is true.
> I am curious as the Japanese had fighters with "schrange muzak" type
> arrangements with upward firing guns and would have wreaked untold
> havoc from the seemingly undefended ventral position.
Yes, but most of these were nightfighters or where more successful
when operating at night: Ki-45-KAI-d, J1N1-S, P1Y1-S... The oblique
guns were very useful for a nightfighter because it could get very close
without being noticed and then had a large target, silhouetted against
the night sky. For day fighters such armament systems were less attractive.
Most of the dedicated B-29 interceptors had forward-firing 30mm or
37mm cannon, even 75 mm cannon. Few of these were completed.
The Ki-46 with its oblique 37mm cannon was the exception, but it
wasn't successful because it lacked the required performance.
The point is moot, really. By 1944 the USAAF had no illusions
whatsoever about the ability of bombers to operate without fighter
escort, even B-29s. Besides, the armament suite of the B-29 did
have its own problems; it asked quite a lot of the technology of the
time. I don't think the USAAF would have liked to rely on it.
Brooks
"Emmanuel Gustin" <Emmanue...@skynet.be> wrote:
>"xvader" <xva...@hotmail.com> wrote in message
>news:bb0062e5.02071...@posting.google.com...
>
>> More specifically, how were the two lower turrets aimable for attacks
>> from below, if the sighting stations were only at the front, two side
>> and top blisters?
>
>From the side blisters the gunners could look and aim downwards.
>But not straight down, that is true.
>
>> I am curious as the Japanese had fighters with "schrange muzak" type
>> arrangements with upward firing guns and would have wreaked untold
>> havoc from the seemingly undefended ventral position.
>
>Yes, but most of these were nightfighters or where more successful
>when operating at night: Ki-45-KAI-d, J1N1-S, P1Y1-S... The oblique
>guns were very useful for a nightfighter because it could get very close
>without being noticed and then had a large target, silhouetted against
>the night sky. For day fighters such armament systems were less attractive.
>
>Most of the dedicated B-29 interceptors had forward-firing 30mm or
>37mm cannon, even 75 mm cannon. Few of these were completed.
>
>The Ki-46 with its oblique 37mm cannon was the exception, but it
>wasn't successful because it lacked the required performance.
>
>The point is moot, really. By 1944 the USAAF had no illusions
>whatsoever about the ability of bombers to operate without fighter
>escort, even B-29s.
I don't think that is quite accurate. Until the seizure of the airfields
on Iwo Jima, and Okinawa, there was no fighter support available for the
B-29's until those islands were taken and fields made operational. The first
missions from the Marianas (Saipan and Tinian) were conducted prior to the
end of 44 (November, IIRC), and Iwo was not in our hands until early March
45. Between those dates, the Superforts acted alone; even after those islands
were captured, not all missions had fighter support provided (ISTR my Dad's
first missions in Mar/Apr timeframe were not escorted).
Besides, the armament suite of the B-29 did
>have its own problems; it asked quite a lot of the technology of the
>time. I don't think the USAAF would have liked to rely on it.
Complex, yes. But also reportedly very effective. My father said the Japanese
fighters they did encounter were rather reluctant to press home attacks in
the face of relatively accurate defensive fires. One thing is sure, the B-29's
defensive gunnery capabilities were greatly superior to those fielded on
other contemporary aircraft (and the FCS was good enough to warrant copying
by the Russians when they built their post war Tu-4's).
Brooks
>
>--
>Emmanuel Gustin <Emmanuel.gustin -@- skynet.be>
>Military Aircraft Database, Fighter Guns Page on
>http://users.skynet.be/Emmanuel.Gustin/
>
>
>
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
Walt BJ
- the 29s were in formation. There would always be at least one other
B29 nearby to help defend the target B29, usually 2 or 3 there to help
out. And at night since Japanese AI radar was weak and the B29s pretty
fast it wasn't an easy task to find one even though the night B29s
only had tail turrets installed so they coukld carry an 8-ton
bombload. I'd say the biggest danger to the day bombers was losing an
engine (the R3350 still was full of bugs) and being forced down to a
lower altitude where JAF fighter performance was rather more adequate.
Walt BJ
Brooks
wal...@mindspring.com (Walt BJ) wrote:
<snip>
> the night B29s
>only had tail turrets installed so they coukld carry an 8-ton
>bombload. I'd say the biggest danger to the day bombers was losing an
>engine (the R3350 still was full of bugs) and being forced down to a
>lower altitude where JAF fighter performance was rather more adequate.
>Walt BJ
I think it would be incorrect to generalize that B-29's conducting night
missions only did so with a tail gun only configuration. My father's unit
(330th BG, 314th BW) conducted both dqay and night missions, with all gun
turrets armed and ready. The 315th BW, which arrived later in the war with
the B-29B and its Eagle radar, apparently did fly tail gun only missions,
but I have not seen any definitive evidence that the 73rd, 313th, or 58th
BW's ever did so, or did so on a regular basis.
Brooks
Cub Driver
>The point is moot, really. By 1944 the USAAF had no illusions
>whatsoever about the ability of bombers to operate without fighter
>escort, even B-29s. Besides, the armament suite of the B-29 did
>have its own problems; it asked quite a lot of the technology of the
>time. I don't think the USAAF would have liked to rely on it.
Still, the 20th Air Force did exactly that, until Iwo Jima was
captured and Mustangs could be based there.
Even on the one great raid I studied in detail, the "thousand-plane"
raid of August 14-15, there were Mustangs in the air but nowhere did I
see a reference that they actually escorted the bombers. (On the other
hand, there was virtually no interception and no B-29 was shot down,
despite the claim in the Caiden-Sakai book "Zero!") Evidently they
just went on hunter-killer missions of their own, and helped make up
the 1,000 a/c Hap Arnold wanted to put over Japan in one coordinated
raid.
(As I recall, one Mustang pilot was lost.)
Guy Alcala
> wal...@mindspring.com (Walt BJ) wrote:
> <snip>
>
> > the night B29s
> >only had tail turrets installed so they coukld carry an 8-ton
> >bombload. I'd say the biggest danger to the day bombers was losing an
> >engine (the R3350 still was full of bugs) and being forced down to a
> >lower altitude where JAF fighter performance was rather more adequate.
> >Walt BJ
>
> I think it would be incorrect to generalize that B-29's conducting night
> missions only did so with a tail gun only configuration. My father's unit
> (330th BG, 314th BW) conducted both dqay and night missions, with all gun
> turrets armed and ready. The 315th BW, which arrived later in the war with
> the B-29B and its Eagle radar, apparently did fly tail gun only missions,
> but I have not seen any definitive evidence that the 73rd, 313th, or 58th
> BW's ever did so, or did so on a regular basis.
I've read several good books on the B-29 and especially the fire raids, published
in the last 5-10 years. From what I recall, on the first Tokyo fire raid LeMay
ordered the guns removed from the a/c (or maybe it was just the breech blocks,
the one account I have a clear memory of said something about removing the firing
mechanism), and they didn't carry ammo except for the tail guns, although they
did carry full crews for some reason (I guess for crew integrity and/or so
everyone could finish their tours together). I don't know that it would be
possible in the Marianas to remove the turrets and still maintain
pressurization. Maj. Gen. (Ret.) Charles W. Sweeney mentioned in his book that
he attempted to modify one of the 509th's B-29s either in the unit or by a local
maintenance depot, forget which, by removing the turrets and installing fuselage
patches, to see if it could be done locally. Patches installed, the a/c was
pressurized in the hangar. At some altitude well short of operating altitude the
patches failed, and it was clear the a/c would have to come from the factory that
way, which they were (along with removing the turrets, the A-bomb support in the
bomb bay was added, plus the a/c had fuel-injected engines and reversible props).
Guy
Brooks
I have been reading everything I could get my hands on regarding B-29's for
most of my life, and have repeatedly encountered the "Lemay orders the guns
removed" snippet, which has seemingly become by conventional wisdom accepted
as normal modus operandi for all B-29's. But I have yet to come across any
specific memoirs from any crews other than those in the 315th BW that mentioned
ever actually having done so. Some aircraft may have done so, but I know
that those in the 330th BG/314th BW apparently never did.
I don't know that it would be
>possible in the Marianas to remove the turrets and still maintain
>pressurization.
I always assumed it was a matter of removing the M2's from the turrets, not
the turrets from the aircraft. The guns could be removed for maintenance,
and their weight would have added up. Another item reportedly removed was
some of the protective armor inside the aircraft (a more realistic COA, IMO,
especially in view of the relative ineffectiveness of Japanese defenses as
the war drew to an end).
Maj. Gen. (Ret.) Charles W. Sweeney mentioned in his book that
>he attempted to modify one of the 509th's B-29s either in the unit or by
a local
>maintenance depot, forget which, by removing the turrets and installing
fuselage
>patches, to see if it could be done locally. Patches installed, the a/c
was
>pressurized in the hangar. At some altitude well short of operating altitude
the
>patches failed, and it was clear the a/c would have to come from the factory
that
>way, which they were (along with removing the turrets, the A-bomb support
in the
>bomb bay was added, plus the a/c had fuel-injected engines and reversible
props).
>
>Guy
The original "Silverplate" B-29's were sort of a breed apart; even the blisters
were apparently faired over, leaving only a small viewing port for a scanner.
I don't believe that later (post-war) Silverplates received as radical a
makeover (retained guns and blisters, IIRC).
Guy Alcala
I'd agree that's the tentative conclusion I've come to. Thinking about it harder,
ISTR that the one source that mentioned removing the 'firing mechanisms' (maybe
they pulled electrical solenoids rather than breechblocks) specifically denied that
the guns were removed on that mission.
>
>
> I don't know that it would be
> >possible in the Marianas to remove the turrets and still maintain
> >pressurization.
>
> I always assumed it was a matter of removing the M2's from the turrets, not
> the turrets from the aircraft. The guns could be removed for maintenance,
> and their weight would have added up.
Some of the less reliable sources have claimed the turrets were removed, but those
accounts seem to be mixing up the time frame and confusing the specialized 315th
with the regular wings. Unless things were radically different for the B-29s with
their remote turrets, the guns would be removed after each mission and turned in to
ordnance, being cleaned and lubed either by the gunners themselves or ordnance, so
pulling them for a mission would be a matter of not installing them. Weight
savings would be 650 lb. for the (10) guns themselves, plus the considerable weight
of the ammo, and the fuel to haul it both ways. The low altitude profile meant
they didn't need the fuel for the long climb to altitude, and the taking of Iwo
meant they didn't have to dogleg to stay out of its radar range, saving some
more. Many sources also claim that the 20mm was often removed and replaced with a
.50 cal. From what I recall, they managed to up the bombloads from about 7,000 to
14,000 lb. average on the first Tokyo fire raid. The wing on Guam (314th, IIRR),
which had further to go, carried less.
> Another item reportedly removed was
> some of the protective armor inside the aircraft (a more realistic COA, IMO,
> especially in view of the relative ineffectiveness of Japanese defenses as
> the war drew to an end).
Hansell, before he was replaced by LeMay, apparently had 1,600 lb. stripped from
the empty weight (probably had sound insulation and various other 'non-essential'
items removed), and more experience and better profiles and fuel management allowed
them to pull a BB fuel tank, saving another 4,600 lb. or so.
Guy
Brooks
I'll ask my Dad about that; I am not aware that guns were routinely removed
after every mission, but thought they were merely cleaned and rodded "in
situ".
Weight
>savings would be 650 lb. for the (10) guns themselves, plus the considerable
weight
>of the ammo, and the fuel to haul it both ways. The low altitude profile
meant
>they didn't need the fuel for the long climb to altitude, and the taking
of Iwo
>meant they didn't have to dogleg to stay out of its radar range, saving
some
>more. Many sources also claim that the 20mm was often removed and replaced
with a
>..50 cal.
Actually, that was apparently a common thing. My Dad indicated his aircraft
(he had two--his crew rotated stateside mid-tour for Lead Crew School and
gained a new aircraft on their return) had the 20mm removed and retained
only the two .50 cal MGs in the tail. Reasoning was not as much weight as
it was the slow rate of fire of the 20mm, and its different trajectory from
the accompanying MG's.
>From what I recall, they managed to up the bombloads from about 7,000 to
>14,000 lb. average on the first Tokyo fire raid. The wing on Guam (314th,
IIRR),
>which had further to go, carried less.
The 314th was indeed on Guam; Dad was at North Field. For some reason I was
thinking that another wing also operated from Guam as well...
>
>
>> Another item reportedly removed was
>> some of the protective armor inside the aircraft (a more realistic COA,
IMO,
>> especially in view of the relative ineffectiveness of Japanese defenses
as
>> the war drew to an end).
>
>Hansell, before he was replaced by LeMay, apparently had 1,600 lb. stripped
from
>the empty weight (probably had sound insulation and various other 'non-essential'
>items removed), and more experience and better profiles and fuel management
allowed
>them to pull a BB fuel tank, saving another 4,600 lb. or so.
>
>Guy
Yeah, that would agree with my readings. Interesting side note--my first
company commander in the Army was the son of the last wartime commander of
my father's bomb group. Small world!
Brooks
"Brooks" <broo...@127.0.0.1> wrote:
>
>Guy Alcala <g_al...@junkpostoffice.pacbell.net> wrote:
>>Brooks wrote:
>>
>>> Guy Alcala <g_al...@junkpostoffice.pacbell.net> wrote:
>>> >Brooks wrote:
>>>
>>Unless things were radically different for the B-29s with
>>their remote turrets, the guns would be removed after each mission and
turned
>in to
>>ordnance, being cleaned and lubed either by the gunners themselves or ordnance,
>so
>>pulling them for a mission would be a matter of not installing them.
>
>I'll ask my Dad about that; I am not aware that guns were routinely removed
>after every mission, but thought they were merely cleaned and rodded "in
>situ".
I talked to Dad this evening, and he said that while the aircrew did not
pull the maintenance on the guns (they had been trained to do so, but in-theater
they had armorers on the ground crew that handled that job for them), he
thought that most of the cleaning and maintenance was done without normally
removing the guns from the turrets.
Brooks
<snip>
The Enlightenment
Could you explain how sighting was accomplished. It looks like the
aiming unit was a reflector sight.
Was range estimated by adjusting a circular recticle about the known
wingspan of the attacking aircraft?
Was the unit more advanced: like a fighter gyro sight that could also
predict the "lead" required? By tracking the target for a few moments
befor firing?
I had heard that when B29s were used over Korea the B29s computers
were not fast enough to handle the Mig 15 Jets.
It appears to me that much of the B29s invincibillity relied upon its
performance. If confronted with advanced piston aircraft such as
TA152C-3
which had a 30mm High Velocity Mk 103 cannon and a service ceiling of
48,000 ft and speed of 470mph it would have been as vulnerable as a
Liberator was to FW190A and Me109Gs ( if not more vulnerable as Mk103
firing might commence beyond the range of the B29's 0.5 inch caliber
Browings )
Peter Stickney
bern...@yahoo.com.au (The Enlightenment) writes:
>> Complex, yes. But also reportedly very effective. My father said the Japanese
>> fighters they did encounter were rather reluctant to press home attacks in
>> the face of relatively accurate defensive fires. One thing is sure, the B-29's
>> defensive gunnery capabilities were greatly superior to those fielded on
>> other contemporary aircraft (and the FCS was good enough to warrant copying
>> by the Russians when they built their post war Tu-4's).
> Could you explain how sighting was accomplished. It looks like the
> aiming unit was a reflector sight.
Yes, that's right.
>
> Was range estimated by adjusting a circular recticle about the known
> wingspan of the attacking aircraft?
That's right, as well
>
> Was the unit more advanced: like a fighter gyro sight that could also
> predict the "lead" required? By tracking the target for a few moments
> befor firing?
Yep. There were 2 gyros in the sight, which tracked azimuth and
elevation rates. The gunner, using the variable reticle, tracked
range adn range rate. The azimuth, elevation, rnage, and az, el, and
range rates were fed by the sight into an electromechanical analog
computer, which muched on that data, mixed in the bomber's altitude,
airspeed, and temperature information, seasoned it with some gravity
drop and parallax info, (Cause the sights weren't in the turrets, and a
sight could be controlling several turrets at once), and then aimed
the turrets assigned to that sight to hit that target. If the system
were tuned and maintained, it worked quite sell, after it had been
debugged. (GE, the designers of the sights, had to go to the company
that made railroad signalling equipment to learn how to make
electronics that would hang together under severe vibration.)
>
> I had heard that when B29s were used over Korea the B29s computers
> were not fast enough to handle the Mig 15 Jets.
That's true. The sights are limited by the rates that the gyros, and
their feedback springs, can handle. A 600 mph MiG-17, making a pass
on a 270-300 mph B-29, was at the high end of those limits.
> It appears to me that much of the B29s invincibillity relied upon its
> performance. If confronted with advanced piston aircraft such as
> TA152C-3
> which had a 30mm High Velocity Mk 103 cannon and a service ceiling of
> 48,000 ft and speed of 470mph it would have been as vulnerable as a
> Liberator was to FW190A and Me109Gs ( if not more vulnerable as Mk103
> firing might commence beyond the range of the B29's 0.5 inch caliber
> Browings )
Well, I don't think that that quite follows. While the sights may
have had some trouble dealing with closing velocities higher than 400
mph, no piston fighter, nor any of the straight-sing jets, (Including
the Me 262, it didn't have enough wing sweep to make any difference,
nor enough power to go fast enough in level flight for the transonic
effects to make any difference, either), is going to have the
performance to slash through a B-29 formation. Maneuver margins at
altitude were very small. It didn't take much of a turn to have the
bottom fall out from under you, and you'd drop a mile or so before
you'd get things back together again. This isn't as important to a
bomber, which is a stable platform with a wing loading much lower than
the fighter, as it is to an interceptor. The fighter's got to pull
lead, and be able to break away at the end of the pass. Otherwise,
he'll end up giving the gunners (and the ballistic computer, in the
B-29), a no-brainer, no deflection shot. The effective range of an
aircraft gun in '45, unless it had a really low muzzle velocity, or a
lousily shaped bullet, was limited more by the ability to sight the
guns as anything else. Here, again, the B-29 has an advantage. With
a computer taking the guesswork out of aiming and firing, you're
probably more likely to hit. The .50 cal bullet had very good
ballistics, outperforming the 20mms at high altitude. (The B-52 tail
guns went from 2 M24 20mm to 4 .50 cal M3s for a reason)
A B-29 was a world of difference from a B-17 or a B-24.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
Emmanuel Gustin
> Reasoning was not as much weight as it was the slow rate of fire of
> the 20mm, and its different trajectory from the accompanying MG's.
I always find that curious. Yes, the 20-mm fired only at about
600 rpm, against 750-850 rpm for the .50"s; which could probably
be boosted to 900 rpm or more by the gunners if they tweaked
the mechanism (risky and against regulations, but many did AFAIK).
And American-made Hispanos were never very reliable. But
different trajectory? The Hispano and Browning .50" had quite
similar trajectories.
The P-38 had the same mix of .50" and 20mm cannon --- You
can find the bore sighting chart for the P-38 on
http://www.zenoswarbirdvideos.com/More_P-38_Stuff.html
Emmanuel Gustin
news:39556695.02071...@posting.google.com...
> It appears to me that much of the B29s invincibillity relied upon its
> performance.
Against Japanese aircraft, certainly. Almost none could operate
effectively at the high altitudes of the B-29. The Japanese were
only too well aware of this and started several projects to develop
high-altitude fighters, but none of them produced results before
the war was over.
> If confronted with advanced piston aircraft such as
> TA152C-3 which had a 30mm High Velocity Mk 103 cannon and
> a service ceiling of 48,000 ft and speed of 470mph it would have
> been as vulnerable as a Liberator was to FW190A and Me109Gs
> ( if not more vulnerable as Mk103 firing might commence beyond
> the range of the B29's 0.5 inch caliber Browings )
I doubt that would have happened. The obvious choices would
have been the Ta 152H high-altitude fighter (not the Ta 152C
which was essentially a fighter-bomber version) and the Me 262.
Also, the weapon of choice against bombers was the MK 108,
not the MK 103; the effective range of the MK 108 was rather
short, but it had a higher rate of fire and two MK 108 only
weighed as much as a single MK 103.
Likewise, the Japanese weapon against the B-29 would have been
the Ho-155, a 30 mm cannon in the same class as the MK 108,
but based on the Browning mechanism preferred by the Japanese
AF (they developed versions of the Browning in 12.7mm, 20mm,
30mm, and 37mm). It would have been installed mainly in Ki-84s.
The Japanese equivalent of the Ta 152H was the Ki-87,
a turbosupercharged high-altitude fighter, but only one prototype
was completed. There was also a twin-engined Ki-108, but again
only prototypes were flown.
--
Emmanuel Gustin <Emmanuel.gustin -@- skynet.be>
Fighter Guns Page & Military Aircraft Database on
http://users.skynet.be/Emmanuel.Gustin/
Brooks
"Emmanuel Gustin" <Emmanue...@skynet.be> wrote:
>"Brooks" <broo...@127.0.0.1> wrote in message
>news:3d35...@news.newsgroups.com...
>
>> Reasoning was not as much weight as it was the slow rate of fire of
>> the 20mm, and its different trajectory from the accompanying MG's.
>
>I always find that curious. Yes, the 20-mm fired only at about
>600 rpm, against 750-850 rpm for the .50"s; which could probably
>be boosted to 900 rpm or more by the gunners if they tweaked
>the mechanism (risky and against regulations, but many did AFAIK).
>And American-made Hispanos were never very reliable. But
>different trajectory? The Hispano and Browning .50" had quite
>similar trajectories.
Hey, dad was only actually there for the big show, and all of the aircraft
in his unit apparently removed the thing. As a gunner himself, and having
a fairly decent memory, I would not discount his version.
>
>The P-38 had the same mix of .50" and 20mm cannon --- You
>can find the bore sighting chart for the P-38 on
>http://www.zenoswarbirdvideos.com/More_P-38_Stuff.html
You can bore sight weapons of various trajectories to have the same focal
point at range X, no doubt. But at all other ranges two weapons with different
trajectories will have different impact points. I am no expert on the WWII
"old" 20mm round, but I would have a hard time believing it had the same
relatively flat trajectory of the .50 round.
Brooks
>
>--
>Emmanuel Gustin <Emmanuel.gustin -@- skynet.be>
>Military Aircraft Database, Fighter Guns Page on
>http://users.skynet.be/Emmanuel.Gustin/
>
>
>
>
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
Brooks
My Dad flew a training mission(s?) out of Muroc (now Edwards AFB) where they
had some early jets (I would imagine early P-80's) conduct simulated firing
passes at them, and he said they had a real problem getting a solution on
*them*, so the Migs must have been a real handfull.
>
>
>> It appears to me that much of the B29s invincibillity relied upon its
>> performance. If confronted with advanced piston aircraft such as
>> TA152C-3
>> which had a 30mm High Velocity Mk 103 cannon and a service ceiling of
>> 48,000 ft and speed of 470mph it would have been as vulnerable as a
>> Liberator was to FW190A and Me109Gs ( if not more vulnerable as Mk103
>> firing might commence beyond the range of the B29's 0.5 inch caliber
>> Browings )
>
>Well, I don't think that that quite follows. While the sights may
>have had some trouble dealing with closing velocities higher than 400
>mph, no piston fighter, nor any of the straight-sing jets,
That would not jive with the experience my Dad discussed with me; the "straight
wing" jets still caused plenty of additional difficulty for the gunners (though
I would imagine not to the degree the later Mig/F-86 class would).
(Including
>the Me 262, it didn't have enough wing sweep to make any difference,
>nor enough power to go fast enough in level flight for the transonic
>effects to make any difference, either), is going to have the
>performance to slash through a B-29 formation. Maneuver margins at
>altitude were very small. It didn't take much of a turn to have the
>bottom fall out from under you, and you'd drop a mile or so before
>you'd get things back together again. This isn't as important to a
>bomber, which is a stable platform with a wing loading much lower than
>the fighter, as it is to an interceptor. The fighter's got to pull
>lead, and be able to break away at the end of the pass. Otherwise,
>he'll end up giving the gunners (and the ballistic computer, in the
>B-29), a no-brainer, no deflection shot. The effective range of an
>aircraft gun in '45, unless it had a really low muzzle velocity, or a
>lousily shaped bullet, was limited more by the ability to sight the
>guns as anything else. Here, again, the B-29 has an advantage. With
>a computer taking the guesswork out of aiming and firing, you're
>probably more likely to hit. The .50 cal bullet had very good
>ballistics, outperforming the 20mms at high altitude. (The B-52 tail
>guns went from 2 M24 20mm to 4 .50 cal M3s for a reason)
>
>A B-29 was a world of difference from a B-17 or a B-24.
Yeah, and the crews knew it (and were thankful). Dad found the B-17 OK, but
a bit cold and uncomfortable (and his one experience having to handcrank
the landing gear down was not apprently real fun), but he rather disliked
the B-24. The B-29 was tops, other than its early propensity to suffer inflight
fires and blow up, leaving little or no trace...
Brooks
Emmanuel Gustin
> Hey, dad was only actually there for the big show, and all of the aircraft
> in his unit apparently removed the thing. As a gunner himself, and having
> a fairly decent memory, I would not discount his version.
I am not blaming him :-). I just don't find these arguments (which I have
heard before) convincing enough to decrease the firepower of their rear
turrets by about 60%. So I was wondering whether there was another
reason.
> I am no expert on the WWII "old" 20mm round, but I would have a hard
> time believing it had the same relatively flat trajectory of the .50
round.
Similar muzzle velocities, a dimensional advantage for the larger
projectile, and a more streamlined shape for the .50" round. That
gave the .50" an advantage at long range. But the P-38 charts show
a quite good match out to 500 yards.
Brooks
"Emmanuel Gustin" <Emmanue...@skynet.be> wrote:
>"Brooks" <broo...@127.0.0.1> wrote in message
>news:3d36...@news.newsgroups.com...
>
>> Hey, dad was only actually there for the big show, and all of the aircraft
>> in his unit apparently removed the thing. As a gunner himself, and having
>> a fairly decent memory, I would not discount his version.
>
>I am not blaming him :-). I just don't find these arguments (which I have
>heard before) convincing enough to decrease the firepower of their rear
>turrets by about 60%. So I was wondering whether there was another
>reason.
I talked to him today, and he said they also did not like the rate of fire
the 20mm offered. A source I have here indicates that the 20mm was removed
when they found the majority of attacks were head on and not tail chases
(bringing it back to matter of weight reduction versus minimal useable firepower
improvement).
>
>> I am no expert on the WWII "old" 20mm round, but I would have a hard
>> time believing it had the same relatively flat trajectory of the .50
>round.
>
>Similar muzzle velocities, a dimensional advantage
And disadvantage (more drag due to increased surface area).
for the larger
>projectile, and a more streamlined shape for the .50" round. That
>gave the .50" an advantage at long range. But the P-38 charts show
>a quite good match out to 500 yards.
Were the muzzle velocities really close? ISTR that the old 20mm (not the
modern rounds) had almost no "bottleneck" (less propellent?). And the gunners
wanted to engage at maximum range; I would imagine that was somewhat more
than 500 yards (we fired small arms qualification out to about 330+ yards).
It may very well have been that the trajectory problem was much worse towards
the outer edge of the envelope). Regardless, the 20mm was found wanting,
and the crews did not mourn its demise.
Brooks
Emmanuel Gustin
> I talked to him today, and he said they also did not like the rate
> of fire the 20mm offered.
Well, it WAS lower than that of the .50"s, although not as much as
some people have imagined -- about 600 rpm against 800 - 900 rpm
for the .50"s.
(It seems to have been a fairly common belief in the wartime USA
that the rate of fire of cannon was much lower, even as low at
100 rpm; but I doubt that trained gunners suffered from such
delusions.)
> >Similar muzzle velocities, a dimensional advantage
>
> And disadvantage (more drag due to increased surface area).
Yes, but the sectional density factor is better. For projectiles of
similar shape and speed, drag increases with area and the mass,
but kinetic energy and momentum with the volume. The result is
that the ratio of energy loss to 'stored' kinetic energy favours the
bigger projectile. So the bigger guns tend to have longer ranges,
but the streamline shape of the .50" was much better than that of
the cannon rounds (this was one of the few efforts the USA made
in weapon design before the war, because of its shoestring defence
budgets) and it outranged the 20mm. IIRC the US Navy concluded
that the 20mm was worth about three .50"s at short and medium
range, but only two-and-a-half at long range.
> Were the muzzle velocities really close? ISTR that the old 20mm
> (not the modern rounds) had almost no "bottleneck" (less propellent?).
The Hispano M2 had a 20x110 cartridge. It fired its HE round
(130 gram) at 880 m/s. For comparison, the .50" M1 incendiary
(41 gram) started out at 900 m/s, the M2 AP (46 gram) at 855 m/s,
and the M8 API (43 gram) at 890 m/s.
The 20x110 cartridge did have some neck, similar to that of the
.50", but proportionally less. The Hispano also had a quite long
barrel because of its origins; Marc Birkigt designed it to be installed
between the cylinder banks of a V12 engine. (The British lopped of
some of the barrel in the Mk.V and reduced muzzle velocity to
850m/s. The USA did the same in the post-war M3 (Navy) and
M24 (air force).)
> And the gunners wanted to engage at maximum range; I would imagine
> that was somewhat more than 500 yards (we fired small arms qualification
> out to about 330+ yards).
The theoretical effective range of the .50" was about 800, but the
probability of hitting anything at distance was almost non-existent.
Normal effective shooting distances were below 250, even for
fighters.
Tamas Feher
> > It appears to me that much of the B29s invincibillity relied upon its
> > performance.
> > If confronted with advanced piston aircraft such as
> > TA152C-3 which had a 30mm High Velocity Mk 103 cannon and
> > a service ceiling of 48,000 ft and speed of 470mph it would have
> > been as vulnerable as a Liberator was to FW190A and Me109Gs
> > ( if not more vulnerable as Mk103 firing might commence beyond
> > the range of the B29's 0.5 inch caliber Browings )
>
> I doubt that would have happened. The obvious choices would
> have been the Ta 152H high-altitude fighter (not the Ta 152C
> which was essentially a fighter-bomber version) and the Me 262.
> Also, the weapon of choice against bombers was the MK 108,
> not the MK 103; the effective range of the MK 108 was rather
> short, but it had a higher rate of fire and two MK 108 only
> weighed as much as a single MK 103.
Don't forget the R4M unguided missiles of Me-262. The Schwalbe killed many B-25
with that weapon.
I don't know why korean/chinese/russian pilots did not use unguided missiles
with MiG-15 to down the B-29s. There was a box-shaped underwing pod of 57mm
missiles for the Mig-15. It is included in the plastic 1/72 scale kit of
Mig-15bis by czech KP firm.
Sincerely: Tamas Feher.
Brooks
If their velocities were similar, I'd think that would argue for a rather
different trajectory (much more flat for the smaller round).
>
>The 20x110 cartridge did have some neck, similar to that of the
>..50", but proportionally less. The Hispano also had a quite long
>barrel because of its origins; Marc Birkigt designed it to be installed
>between the cylinder banks of a V12 engine. (The British lopped of
>some of the barrel in the Mk.V and reduced muzzle velocity to
>850m/s. The USA did the same in the post-war M3 (Navy) and
>M24 (air force).)
>
>> And the gunners wanted to engage at maximum range; I would imagine
>> that was somewhat more than 500 yards (we fired small arms qualification
>> out to about 330+ yards).
>
>The theoretical effective range of the .50" was about 800, but the
>probability of hitting anything at distance was almost non-existent.
>Normal effective shooting distances were below 250, even for
>fighters.
250 sounds extremely close for a B-29; I can't see the gunners waiting for
them to close that much before engaging. I read an account today where Galland
indicated he liked to hit B-17's by firing initially at about 650 yards--the
bomber would of course prefer to fire from an aven longer range. And I thought
the .50 cal effective range was a bit more than 800 yards, especially with
the GE FCS.
But no big deal either way. Enjoyed the exchange of ideas.
Brooks
>
>--
>Emmanuel Gustin <Emmanuel.gustin -@- skynet.be>
>Military Aircraft Database, Fighter Guns Page on
>http://users.skynet.be/Emmanuel.Gustin/
>
>
>
>
>
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
Unknown
>
>250 sounds extremely close for a B-29; I can't see the gunners waiting for
>them to close that much before engaging. I read an account today where Galland
>indicated he liked to hit B-17's by firing initially at about 650 yards--the
>bomber would of course prefer to fire from an aven longer range. And I thought
>the .50 cal effective range was a bit more than 800 yards, especially with
>the GE FCS.
>
>But no big deal either way. Enjoyed the exchange of ideas.
>
>Brooks
Lancaster for ASW work we were told to open fire at 1000 yds, not
that we'd hit much at that range but it tended to inhibit the
enthusiasm of any possible submarine gunners when they saw tracer
whizzing by.
--
Gord Beaman
PEI, Canada
"Old age is no place for sissies" -Bette Davis.
Brooks
Don't know about the abilities of the mount on your aircraft, but the .303
and 7.62mm class rounds are plenty lethal at well over 1000 yards. I would
be surprised if the B-29 gunners were not trying to engage at 800-1000 yards
(will have to ask Dad, but during his 15 combat missions he never had the
opprtunity to actually shoot at a Japanes fighter--says something about both
the B-29's defensive reputation and the status of the Japanese air defenses
in 45).
Emmanuel.Gustin
: If their velocities were similar, I'd think that would argue for
: a rather different trajectory (much more flat for the smaller round).
Well, look at the P-38 chart:
http://www.zenoswarbirdvideos.com/Images/P-38/38BSC.gif
Not more than 2 inch difference out to 500 yards. At similar muzzle
velocities the larger round should normally have the flatter
trajectory, but the better streamlining of the .50" evens it.
P-38 pilots were usually praising their armament installation for
its consistent pattern over long ranges; there were complaints
about the reliability of the Hispano but not about its trajectory.
: 250 sounds extremely close for a B-29; I can't see the gunners waiting for
: them to close that much before engaging. I read an account today where Galland
: indicated he liked to hit B-17's by firing initially at about 650 yards--the
: bomber would of course prefer to fire from an aven longer range. And I thought
: the .50 cal effective range was a bit more than 800 yards, especially with
: the GE FCS.
Well, perhgaps 250 is short for opening fire. It would be the
normal distance if you really want to hit
the target; except for a handful of expert shots. Most men would
underestimate the range anyway. At 800 shots could be fired in
the hope of distracting the enemy, but with little hope of hitting
anything. At that distance a fighter would be only a speck and
quite hard to see, and the dispersion of the gun would become
significant.
I am not sure that the GE system, for all its sophistication,
was necessarily more accurate than a local-controlled turret
with a decent gunsight (near the end of the war gyroscopic
sights were introduced). I have been told that the distortion
of the fuselage under flying loads, or the local heating if it
was exposed to the sun from one side, resulted in measurable
aiming errors; because the gunners were sitting at a distance
from the guns. So aircraft were towed into cool shaded hangars
to test the accuracy of their gunnery systems for factory
acceptance tests; what they did in combat was another matter.
The central fire control systems of the B-29 and the later
B-50 remained more or less one-off experiments. The B-36 had
remote, retractable turrets, but they were under direct control
of a gunner seated close to them, AFAIK.
Emmanuel Gustin
Brooks
"Emmanuel.Gustin" <gus...@hhipe.uia.ac.be> wrote:
>Brooks <broo...@127.0.0.1> wrote:
>
>: If their velocities were similar, I'd think that would argue for
>: a rather different trajectory (much more flat for the smaller round).
>
>Well, look at the P-38 chart:
>http://www.zenoswarbirdvideos.com/Images/P-38/38BSC.gif
>Not more than 2 inch difference out to 500 yards. At similar muzzle
>velocities the larger round should normally have the flatter
>trajectory, but the better streamlining of the .50" evens it.
I'd prefer to see a chart out to 800/1000 yards, to be honest. I believe
what you are seeing here is the boresight chart required to acheive a common
weapons zero at some prescribed distance X. I am not sure that an 800 yard
chart would not show something a bit different.
>
>P-38 pilots were usually praising their armament installation for
>its consistent pattern over long ranges; there were complaints
>about the reliability of the Hispano but not about its trajectory.
>
>: 250 sounds extremely close for a B-29; I can't see the gunners waiting
for
>: them to close that much before engaging. I read an account today where
Galland
>: indicated he liked to hit B-17's by firing initially at about 650 yards--the
>: bomber would of course prefer to fire from an aven longer range. And I
thought
>: the .50 cal effective range was a bit more than 800 yards, especially
with
>: the GE FCS.
>
>Well, perhgaps 250 is short for opening fire. It would be the
>normal distance if you really want to hit
>the target; except for a handful of expert shots.
Uhmmm...I don't think so. 250 yards is actually pretty darned close.
Most men would
>underestimate the range anyway. At 800 shots could be fired in
>the hope of distracting the enemy, but with little hope of hitting
>anything.
No, in the case of the GE sight there was no estimation of range--the computer
did that for you based upon the wingspan input.
At that distance a fighter would be only a speck and
>quite hard to see, and the dispersion of the gun would become
>significant.
Huh? I have shot *human torso* size silhouettes at 330 yards plus, over open
sights. A fighter aircraft offers a rather larger silhouette at the range
of 800 yards than I think you would imagine.
>
>I am not sure that the GE system, for all its sophistication,
>was necessarily more accurate than a local-controlled turret
>with a decent gunsight (near the end of the war gyroscopic
>sights were introduced).
My resources say it was; and my dad says it was a heck of a lot more accurate
than the turrets in the B-24's/B-17's that he trained on.
I have been told that the distortion
>of the fuselage under flying loads, or the local heating if it
>was exposed to the sun from one side, resulted in measurable
>aiming errors; because the gunners were sitting at a distance
>from the guns. So aircraft were towed into cool shaded hangars
>to test the accuracy of their gunnery systems for factory
>acceptance tests; what they did in combat was another matter.
I would think that would have afforded a more realistic simulation of the
combat situation than you might think. The key would be to have uniform conditions
throughout (the very cold temps experienced during high altitude operations
would tend to ensure a more or less uniform condition overall as well).
>
>The central fire control systems of the B-29 and the later
>B-50 remained more or less one-off experiments. The B-36 had
>remote, retractable turrets, but they were under direct control
>of a gunner seated close to them, AFAIK.
I believe the B-36 used a very similar system, with the gunner operating
from a sighting blister and using a computerized weapons sight developed
from the B-29 model.
Brooks
>
>Emmanuel Gustin
Emmanuel.Gustin
: I'd prefer to see a chart out to 800/1000 yards, to be honest. I believe
: what you are seeing here is the boresight chart required to acheive a common
: weapons zero at some prescribed distance X. I am not sure that an 800 yard
: chart would not show something a bit different.
I don't think I have seen charts that far out. (IIRC there
may be some trajectory drop values in the Cobra! book by
Matthews, but I don't have that at hand now.) Most data
cover shorter distances, because these were more relevant
for air combat. Let me repeat this contribution by Dave
Everest to an older discussion:
Reference the similarity of trajectory of .5 Browning
and 20mm Hispano,here are the gravity drops of the
.5 Ball MI and the 20mm Ball Mk1Z (Tracer M1 and Tracer
Mk1Z in parentheses)
Distance Gravity drop .5 Gravity drop 20mm
(yards) (feet) (feet)
100 0.209 (0.210) 0.19 (0.20)
200 0.890 (0.880) 0.78 (0.82)
300 2.070 (2.070) 1.84 (1.94)
400 3.84 (3.82) 3.44 (3.61)
500 6.29 (6.25) 5.68 (5.95)
600 9.46 (9.4) 8.66 (9.00)
: No, in the case of the GE sight there was no estimation of
: range--the computer did that for you based upon the wingspan
: input.
That was a common solution with reflector sights throughout
the war, although less sophisticated ones: Rings indicated
the range that corresponded with a given size for a given
wing span. Sights often had range input settings labeled
with enemy aircraft types. A problem with the system was
that aircraft recognition tended to be quite bad, but
luckily fighter wing spans were not too different.
: Huh? I have shot *human torso* size silhouettes at 330
: yards plus, over open sights. A fighter aircraft offers
: a rather larger silhouette at the range of 800 yards
: than I think you would imagine.
Don't forget that the surface area decreases quadratically
with the distance, and that the frontal area of WWII fighters
was as small as possible. There is also a big difference
between looking for a target that you know to be there in
a certain direction, and scanning the sky for a possible
attacker.
: I believe the B-36 used a very similar system, with the
: gunner operating from a sighting blister and using a
: computerized weapons sight developed from the B-29 model.
With computerised sights, yes, but as far as I know
without the central fire control system of the B-29.
Gunners could not e.g. control other gun turrets than
their own.
Emmanuel Gustin
Brooks
Thanks; I found this more valuable than the P-38 boresight chart. I would
concede that the ballistics issue is unlikely to have been a factor based
upon these numbers.
>
>: No, in the case of the GE sight there was no estimation of
>: range--the computer did that for you based upon the wingspan
>: input.
>
>That was a common solution with reflector sights throughout
>the war, although less sophisticated ones: Rings indicated
>the range that corresponded with a given size for a given
>wing span. Sights often had range input settings labeled
>with enemy aircraft types. A problem with the system was
>that aircraft recognition tended to be quite bad, but
>luckily fighter wing spans were not too different.
Dad said that aircraft recognition and knowledge were a major part of his
gunnery training; they would "flash" images on a screen and they would have
to identify the aircraft in question. I would doubt that the GE system was
infallible in this regard due to inevitable human error, but it apparently
was still much more accurate than using iron sights, as was the case with
the other bomber defensive systems of the day.
>
>: Huh? I have shot *human torso* size silhouettes at 330
>: yards plus, over open sights. A fighter aircraft offers
>: a rather larger silhouette at the range of 800 yards
>: than I think you would imagine.
>
>Don't forget that the surface area decreases quadratically
>with the distance, and that the frontal area of WWII fighters
>was as small as possible. There is also a big difference
>between looking for a target that you know to be there in
>a certain direction, and scanning the sky for a possible
>attacker.
True, but I still think they were picking up bogies at relatively long ranges
in *most* cases, and they definitely wanted to engage at max effective weapons
range. In this vein (and contrary to what I have just written), my Dad told
me of the one occasion when he saw a Japanese fighter close enough to engage;
seems one had slipped in on their formation without being detected at all,
and when the right blister gunner finally saw it (he had apparently diverted
his attention elsewhere) it was flying rather close formation underneath
them and to the rear of their wing. He finally let out a yell and tried to
get onto the target, but the fighter peeled off to the left, leaving Dad
to watch him disappear low and to the left from his left blister. He was
hollering to have the CFC gunner give him the guns, but the CFC had already
apprently given them to the right gunner, and by the time he switched back
to Dad on the left side the Japanese fighter was out of range. He laughed
about it when he told me the story...but I doubt there was much laughing
that day in the gunners' compartment!
>
>: I believe the B-36 used a very similar system, with the
>: gunner operating from a sighting blister and using a
>: computerized weapons sight developed from the B-29 model.
>
>With computerised sights, yes, but as far as I know
>without the central fire control system of the B-29.
>Gunners could not e.g. control other gun turrets than
>their own.
Right. I think they used the sight system only, with its lead computation
capabilities, but I agree the CFC system was not used to control other turrets.
Thanks for the info!
Brooks
John Keeney
Emmanuel.Gustin <gus...@hhipe.uia.ac.be> wrote in message
news:ahc163$rgjqq$1...@fu-berlin.de...
> Brooks <broo...@127.0.0.1> wrote:
>
> : If their velocities were similar, I'd think that would argue for
> : a rather different trajectory (much more flat for the smaller round).
>
> Well, look at the P-38 chart:
> http://www.zenoswarbirdvideos.com/Images/P-38/38BSC.gif
> Not more than 2 inch difference out to 500 yards. At similar muzzle
> velocities the larger round should normally have the flatter
> trajectory, but the better streamlining of the .50" evens it.
Looking at the chart, Emmanuel, I'ld say it's for an intended
procedure of to converge them at 350-400 yards which
is naturally going to show good results out to 500.
Look at the near end: 50 yards out the 20mm is 3" lower
than the bottom 50s reflecting the lower mounting in the plane.
In the next 300 yards it has made up this initial disadvantage
by having been angled higher but at 500 yards the parabola
has peaked and it's all ready an inch back down. I'm afraid
the divergence has all ready started between the lines of fire
and at 750 yards is going to meet or (more likely) exceed
that at 50 yards.
Hmm, we ought to be able to model it given the data in the
chart if anybody knows off hand the high difference of
the mounts.
John Keeney
>
> Huh? I have shot *human torso* size silhouettes at 330 yards plus, over
open
> sights. A fighter aircraft offers a rather larger silhouette at the range
> of 800 yards than I think you would imagine.
330 yards, Brooks? What an odd distance, 300m firing range?
I've shot the 250m pop-up silhouettes and had little problem
putting a 3-4 round burst in one (seldom hit with the
occasional 5th round).
Brooks
Yep, the standard US Army qualification range target array starts at 50 meters
and increases by 50 meter intervals to a maximum range of 300 meters. Targets
appear as randomly ranged singles and doubles, with 20 exposures in a prone
supported position, and 20 exposures in a foxhole/unsupported position. I
was one of those strange guys who was more likely to snap off a shot at the
50 meter target and miss, while dropping the 300 meter target with fair regularity
(a factor of taking one's time (at least, what time was given) on the far
out targets and rushing the close up "easy" (or so assumed at the time) targets,
I guess). All firing done from semi-auto setting (we only used full auto,
or later three round burst, on night ranges--but even that later changed,
with semi being the setting used for later night quals).
Brooks
Brooks
Yep, the standard US Army qualification range target array starts at 50 meters
and increases by 50 meter intervals to a maximum range of 300 meters. Targets
appear as randomly ranged singles and doubles, with 20 exposures in a prone
supported position, and 20 exposures in a foxhole/unsupported position. I
was one of those strange guys who was more likely to snap off a shot at the
50 meter target and miss, while dropping the 300 meter target with fair regularity
(a factor of taking one's time (at least, what time was given) on the far
out targets and rushing the close up "easy" (or so assumed at the time) targets,
I guess). All firing done from semi-auto setting (we only used full auto,
or later three round burst, on night ranges--but even that later changed,
with semi being the setting used for later night quals).
Brooks
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
Peter Stickney
Well, to throw some fuel into the fire (or is that "fool", I never can
qute tell), I found myself curious about just what a WW 2 bomber
turret could track accurately, and in browing aeound, found
http://www.navylib.com/, which has a good section on the various
turrets used on the B-24/PB4Y, and thus the B-17 as well, and
http://www.btinternet.com/~steven.ballance/ballance/main.htm
Which does the same thing in amazing detail for the turrets used on
the various models of the Halifax. I wasn't able to find anything on
the GE system for the B-29, but we'll take these as a starting point.
The navylibs site has the gun harmonization diagrams for the various
.50 cal turrets. The guns are harmonized for 1,000 yds. ('bout 900m)
That may seem a bit long, but with the relatively narrow mount, I
suppose it doesn't make much difference.
Both the U.S. and Brit turrets have a maximum tracking speed of about
30 deg/sec, with a higher speed available to slew quickly to a new
target.
This got me playing with the back on an envelope, and a few things
popped up. For the sake of ease of number crunching, let's call the
max tracking rate (The upper limit of the variable speed controls)
as 500 mils/second. This is going to equate to various speeds at
different distances, but it's a lot easier to figure out.
Both the bomber gunners and the interceptor pilot have to somehow
solve how much lead to pull to hit the target. This is going to be a
combination of the target's apparent crossing speed, and teh range to
the target. We'll assume that the sights are solving that. (Gyro
sights, which were late war equipment, and I don't want to get into
the math for it right now. Anyway, I've come up with a handy table
that relates crossing speed (or overtake, depending on the angle) to
angle rate in mils/sec.
These nombers are for Vc for eather 0 aspect or 180 degree aspect,
with both the bomber & fighter on the same or opposite headings.
A 45 degree angle off will give speeds of 0.71 of these. 30 degrees
angle off gives speeds of 0.5. To do the full thing gets more
complicated than I want to get, here. Let's just call this the
maximum deflection shot, for the sake of simplicity.
Apparent Angle rate, Mils/sec
Speed 3000'/910m 1000'/300m 500'/150m
60 mph/100 kph 29 88 176
120 mph/200 kph 58 176 352
180 mph/300 kph 88 264 528
240 mph/400 kph 117 352 704
300 mph/500 kph 146 440
360 mph/600 kph 176 528
420 mph/700 kph 205 616
480 mph/800 kph 234 704
540 mph/900 kph 264 792
As you can see, the closer that the fighter is to the bomber, the
faster the crossing speed is, and the slower the apparent speed is
that can be tracked. A prop fighter, BTW, vs. a B-17 would, in a pass
from behind, co-heading, have an overtale speed of about 180-240 mph.
Vs. a B-29, the overtake would be on the order of 120-180 mph.
An early jet, like an F-80 or Me 262, would overtake a B-17 at about
340-350 mph, and a B-29 at 280-290 mph.
As you can see, if a fighter were to cruise past at 1,000 ft distance,
it would be vulnerable up to an overtake of 360 mph. At 500 ft
distance, teh vulnerable overtake would be 180 mph.
(This is hard to do without all the Fighter-Pilot Hand-waving).
Of course, real attacks don't work that way. Attacks from behind were
typically lead curve-of-pursuit attacks, where the fighter's pulling
the approprate lead for the aspect & angle, changing it's apparent
crossing speed with the bomber to end up, hopefully, directly behind
the bomber, co-heading and altitude, and at teh optimum range for a
killer shot. It's not that easy, of course. The slower the overtake,
the longer the run, and the less the lead angles (for both the
fighter and the bomber gunners, is. This gives an easier shot, and
more time to aim. Our mythical interceptor, making a pass from behind
our stereotypical B-17/B-24/Lancafax, will take 6 seconds to close
from 1000m, (Bomber's sighting range), to 300m (fighter opens fire).
from 300m to 150m (fighter breaks off) takes a bit less than 2 seconds.
In order to be able to generate enough overtake to close on the target
from the perch, the initial position can't be too far offset to the
side, and the lead angle will be faily small. For an Me 262, the
range cleses from 1000m to 300m in 4 seconds, and from 300m to 150m
in 'bout 1 second. This allowed a pursuit curve to start from a
higher offset, requiring the gunners to pull more lead, and by the
time the zero-deflection shot occurred, the fighter was too fast to track.
You can see why the Me 262 didn't have a lot to fear from the bomber
gunners in the Eighth Air Force, being at the top end of what could be
tracked.
Against our B-29 type target, with a piston-engined intercetor, the
fighter closes from 1000m to 300m in will take 10 seconds to close
from 1000m, (Bomber's sighting range), to 300m (fighter opens fire).
from 300m to 150m (fighter breaks off) takes about 2.7 seconds.
For the Me 262/F-80, the closure from 1000m to 300m takes about 5
seconds, and the gun run from 300m to 150m takes about a second and a
half. That's about what the top end of what the turrets could
probably handle.
One futher random spark on the B-29 20mm gun - It only came with the
60 round drum magazine. With that short a time of fire, the extra
punch was probably considered not worht the weight and complication.
A couple of points about the B-36 system. I thought it used the same
centralized control as the B-29, but that wasn't the case. However,
it may not have been due to system aspects, as it were. Using the
age-old "hold my eye next to the model & squint" approach with my
Monogram 1/72nd B-36, it appears that no gunner's position had enough
of a line of sight to use the covered arcs of multiple turrets. That
beast was _huge_.
Brooks
The B-29 had a problem handling frontal attacks, which was the reason the
4-gun turret replaced the original twin mount in the upper-forward position.
The folks at Eglin were proposing using a manual turret to remedy that shortcoming,
but the USAAF instead decided that doubling (or increasing by one third,
if the lower forward turret was also engaging) the amount of lead tossed
out was a better solution, and stuck with the GE FCS. I would imagine that
the high closure speeds made it difficult for the rudimentary "computer"
to keep up with the solution process (and this agrees with your conclusions
regarding later jet attacks, where the USAF found in Korea that the GE FCS
just was not able to handle the Mig-15 adequately).
>
>One futher random spark on the B-29 20mm gun - It only came with the
>60 round drum magazine. With that short a time of fire, the extra
>punch was probably considered not worht the weight and complication.
Sounds reasonable. For whatever reason, it was not widely used; even the
early aircraft that did have it apparently removed it rather early on.
Brooks
>
>A couple of points about the B-36 system. I thought it used the same
>centralized control as the B-29, but that wasn't the case. However,
>it may not have been due to system aspects, as it were. Using the
>age-old "hold my eye next to the model & squint" approach with my
>Monogram 1/72nd B-36, it appears that no gunner's position had enough
>of a line of sight to use the covered arcs of multiple turrets. That
>beast was _huge_.
>
>--
>Pete Stickney
> A strong conviction that something must be done is the parent of many
> bad measures. -- Daniel Webster
>
>
>
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
Billy Beck
"Emmanuel.Gustin" <gus...@hhipe.uia.ac.be> wrote:
>Brooks <broo...@127.0.0.1> wrote:
>: Huh? I have shot *human torso* size silhouettes at 330
>: yards plus, over open sights. A fighter aircraft offers
>: a rather larger silhouette at the range of 800 yards
>: than I think you would imagine.
>
>Don't forget that the surface area decreases quadratically
>with the distance, and that the frontal area of WWII fighters
>was as small as possible.
Here's a perspective: when I sit at the hold-short line watching
an airplane ahead of me rolling for takeoff down the 6000' runway, and
when he's a third of the way along that length, I'm pretty sure I
could shoot right straight at him with a weapon that could do it.
Your average spam-can is smaller than a WW II fighter, and I'm usually
looking at 'em more or less straight at their six o'clock. I don't
have a problem seeing them.
This...
>There is also a big difference
>between looking for a target that you know to be there in
>a certain direction, and scanning the sky for a possible
>attacker.
...is a considerable point, but I might expect trained gunners to
be able to acquire aircraft better than me.
This is a very good discussion, you guys.
Billy
VRWC Fronteer
http://www.mindspring.com/~wjb3/free