The prone postion for tail gunners versus turrets.

[The Enlightenment]

American and British aircraft were known for their use of power driven
tail turrets. In the case of British aircraft the aircraft was
designed around the turret. (It must have been effective: British
bombers showed no loss in performance compared to more sexy looking
yank aircraft which seemed to have less nimble but more streamlined
looking tail turrets, the Wellingtons performace was remarkable for
its small engines)

Tail armament was however rare for Russian, Japanese, Italian and
German bombers. When it did appear if usually consisted of a gunner
in the tail or (nose) in a prone position opperating a gun manualy. I
can't see a problem with this except that the allowable movement would
probably be limited to +/- 25 degrees.

The Germans were capable of making power driven turrets and tested
british style rear turrets for the He177. The loss in speed and the
cost in skills short germany must have disuaded them and the fact that
their small 2 engined tactical bombers would not have accepted maned
tale turrets gracefully. It appears that their objective were 400mph
bombers like the Ju 288 with remote control barbetts in the dorsal,
ventral and tail position. (Bomber B due in 1942 failed for reasons
to do with engine delays for unknown reasons). Some german bomber did
have remote controlled tail armament.

Back to the prone position. Intitially this postition seemed poor to
me but then I read the sumarised results of extensive German WW2
research which indicates that it was comfortable for 1 to 1.5 hours
and that the G tollerance in this position was much higher than the G
tollerane of a sitting pilot.

The reseach is sumarised here:
<http://www.luft46.com/prototyp/berlin9.html>

The cost in CD (Coefficnt of Drag) I estimate as follows: 1 meter (40
inch) diameter flat hole of 0.77 m2 area in the tail of an aircraft to
me seems to add a coefficint of drag of about 0.2.

( A bullet has a CD of about 0.30 and a near perfect streamline
0.1-0.05 so I assume the conversion of a strealine tail to a flat cut
off would result in a
Cd = 0.78 x (0.3 - 0.05) = 0.2 on the basis of the kamm effect.

The power this would absorb at 440 mph or 200 meters/second would be
calculated from this.

drag = 1/2 x Cd x Area x air density x speed^2

extra power = drag x speed x 1/prop efficiency.

Doing those caculations for an air density of 0.5 at about 25,000 feet
and a prop efficiency of 0.75 I come up with a maned rear gun
absorbing about 2000N force or 200 kg drag at 200m/sec which would
require 533kW or 700hp.

At 100m/sec spped or 220mph the drag is only 500N (50Kg) and the power
only 66kw or about 100hp.

For 150m/sec or 330mph the firgures are:
1150N drag (115kg)
225kw power (300hp)

******************

It seems to me that a 400mph aircaft with tail armament was possible.
I daresay a mosquito would not have suffered too much in speed if the
tail had of been completely redesigned to accomodate a prone tail
gunner. Little other armament would be necessary.

In other words an aircraft so fast it would be very difficult to
intercept and upon which only a tail chase attack would be possible.

It also looks like that speed did not suffer much at speeds below
330mph.

I of course have not include the effect of weight of such an
installation.

[Keith Willshaw]

"ArtKramr" > wrote in message
...
> >Subject: Re: The prone postion for tail gunners versus turrets.
> >From: "Keith Willshaw"
> >Date: 7/21/03 4:06 AM Pacific
>
> > in the tail or (nose) in a prone position opperating a gun manualy. I
> >> can't see a problem with this except that the allowable movement would
> >> probably be limited to +/- 25 degrees.
> >>
>
> Limited action on a tail gun no problem???? I would say it is rather a
severe
> problem.
>
>

I agree but I didnt say that, the poster who calls himself
'The Enlightenment' did so.

Keith

[Keith Willshaw]

"ArtKramr" > wrote in message
...
> >Subject: Re: The prone postion for tail gunners versus turrets.
> >From: "Keith Willshaw"
> >Date: 7/21/03 6:54 AM Pacific Daylight Time
> >Message-id: >
> >
> >
> >"ArtKramr" > wrote in message
> ...
> >> >Subject: Re: The prone postion for tail gunners versus turrets.
> >> >From: "Keith Willshaw"
> >> >Date: 7/21/03 4:06 AM Pacific
> >>
> >> > in the tail or (nose) in a prone position opperating a gun manualy.
I
> >> >> can't see a problem with this except that the allowable movement
would
> >> >> probably be limited to +/- 25 degrees.
> >> >>
> >>
> >> Limited action on a tail gun no problem???? I would say it is rather a
> >severe
> >> problem.
> >>
> >>
> >
> >I agree but I didnt say that, the poster who calls himself
> >'The Enlightenment' did so.
> >
> >Keith
> >
> >
>
> Sorry about that Keith.
>

No problem , just trying to keep the record straight, I get enough
things wrong on my own :)

Keith

[The Enlightenment]

"Keith Willshaw" > wrote in message >...
> "The Enlightenment" > wrote in message
> om...
> > American and British aircraft were known for their use of power driven
> > tail turrets. In the case of British aircraft the aircraft was
> > designed around the turret. (It must have been effective: British
> > bombers showed no loss in performance compared to more sexy looking
> > yank aircraft which seemed to have less nimble but more streamlined
> > looking tail turrets, the Wellingtons performace was remarkable for
> > its small engines)
> >
>
> While the Air ministry specn called for turrets I rather doubt the aircraft
> was designed around them , especially since the Halifax used BoultonPaul
> turrets while those on the Strirling and Lancaster came from Frazer Nash.

Yet they were physically very similar. The whole shape of British
aircraft seem to have been designed around them. Whereas the B17 was a
conventional aircarft with a conventintional tail that had its tail
cone replaced with spherical gun turret. There is no way a B17 could
have accomodated a British style turret. Even a B24 Liberator would
have difficulty.


>
> I wouldnt exactly describe the Wellington as having small engines
> either. The mk 1C had two 1000 hp Bristol Pegasus XVIII's and
> the Mk X had a pair of 1675 hp Britsol Hercules engines

A lot less than a B26 which had much more powerfull engines in the
2200hp range.

Some marks also had merlins and perfomed. All had good performance in
the 280mpp to 300mph range, powefull armament (the front and rear
turrets had such a good range of traverse and elevation a dorsal
turret was unnecessay I expect)



>
> > Tail armament was however rare for Russian, Japanese, Italian and
> > German bombers. When it did appear if usually consisted of a gunner
> > in the tail or (nose) in a prone position opperating a gun manualy. I
> > can't see a problem with this except that the allowable movement would
> > probably be limited to +/- 25 degrees.
> >
>
> The Germans experimented with gun turrets but rejected the idea
> because of the extra drag, late model He-111's did have a
> single remotely operated gun in the tail cone and the Ju-88
> had a rotating disc with gun mount at the rear of the cockpit

I've never understood this 'remote controlled gun' in the tail cone.
Was it remotely trigered or could it be trained as well? The latter
Do 217 had a similar arrangement I believe.

The Arado 234B jet bomber could carry a pair of 20mm cannon that were
fixed but aimed by periscope.


>
> > The Germans were capable of making power driven turrets and tested
> > british style rear turrets for the He177. The loss in speed and the
> > cost in skills short germany must have disuaded them and the fact that
> > their small 2 engined tactical bombers would not have accepted maned
> > tale turrets gracefully. It appears that their objective were 400mph
> > bombers like the Ju 288 with remote control barbetts in the dorsal,
> > ventral and tail position. (Bomber B due in 1942 failed for reasons
> > to do with engine delays for unknown reasons). Some german bomber did
> > have remote controlled tail armament.
> >
> > Back to the prone position. Intitially this postition seemed poor to
> > me but then I read the sumarised results of extensive German WW2
> > research which indicates that it was comfortable for 1 to 1.5 hours
> > and that the G tollerance in this position was much higher than the G
> > tollerane of a sitting pilot.
> >
> > The reseach is sumarised here:
> > <http://www.luft46.com/prototyp/berlin9.html>
> >
> > The cost in CD (Coefficnt of Drag) I estimate as follows: 1 meter (40
> > inch) diameter flat hole of 0.77 m2 area in the tail of an aircraft to
> > me seems to add a coefficint of drag of about 0.2.
> >
> > ( A bullet has a CD of about 0.30 and a near perfect streamline
> > 0.1-0.05 so I assume the conversion of a strealine tail to a flat cut
> > off would result in a
> > Cd = 0.78 x (0.3 - 0.05) = 0.2 on the basis of the kamm effect.
> >
> > The power this would absorb at 440 mph or 200 meters/second would be
> > calculated from this.
> >
> > drag = 1/2 x Cd x Area x air density x speed^2
> >
> > extra power = drag x speed x 1/prop efficiency.
> >
> > Doing those caculations for an air density of 0.5 at about 25,000 feet
> > and a prop efficiency of 0.75 I come up with a maned rear gun
> > absorbing about 2000N force or 200 kg drag at 200m/sec which would
> > require 533kW or 700hp.
> >
> > At 100m/sec spped or 220mph the drag is only 500N (50Kg) and the power
> > only 66kw or about 100hp.
> >
> > For 150m/sec or 330mph the firgures are:
> > 1150N drag (115kg)
> > 225kw power (300hp)
> >
> > ******************
> >
> > It seems to me that a 400mph aircaft with tail armament was possible.
> > I daresay a mosquito would not have suffered too much in speed if the
> > tail had of been completely redesigned to accomodate a prone tail
> > gunner. Little other armament would be necessary.
> >
> > In other words an aircraft so fast it would be very difficult to
> > intercept and upon which only a tail chase attack would be possible.
> >
> > It also looks like that speed did not suffer much at speeds below
> > 330mph.
> >
> > I of course have not include the effect of weight of such an
> > installation.
>
> The mosquito was much too small to provide a 3rd crew position
> at the rear, you would need a remote operated turret with periscope
> sighting as on the A-26 Invader. Given that mosquito loss rates
> were as low as they were and the utility of such guns was doubtful
> it seems likely such a solution would not have been adopted.

Low drag guns can also be installed on the sides of the fueselage, Me
410 style or in the rear of the engine nacells.

The problem with perisopes seems to have been the difficulty in
detecting the aircraft. I don't know if episcopes / periscopes
improved.

However I still suspect that a simple rear gunner lieing in the prone
position could be built not to reduce speed too much.

[The Enlightenment]

(ArtKramr) wrote in message >...
> >Subject: Re: The prone postion for tail gunners versus turrets.
> >From: "Keith Willshaw"
> >Date: 7/21/03 4:06 AM Pacific
>
> > in the tail or (nose) in a prone position opperating a gun manualy. I
> >> can't see a problem with this except that the allowable movement would
> >> probably be limited to +/- 25 degrees.
> >>
>
> Limited action on a tail gun no problem???? I would say it is rather a severe
> problem.
>

At 350mph to 400mph few other attack angles would be possible. I
expect angels outside of that could be defended by waist guns or
similar low drag arrangements.

[ArtKramr]

>Subject: Re: The prone postion for tail gunners versus turrets.
>From: (The Enlightenment)
>Date: 7/21/03 6:04 PM Pacific Daylight Time
>Message-id: >
>
(ArtKramr) wrote in message
>...
>> >Subject: Re: The prone postion for tail gunners versus turrets.
>> >From: "Keith Willshaw"
>> >Date: 7/21/03 4:06 AM Pacific
>>
>> > in the tail or (nose) in a prone position opperating a gun manualy. I
>> >> can't see a problem with this except that the allowable movement would
>> >> probably be limited to +/- 25 degrees.
>> >>
>>
>> Limited action on a tail gun no problem???? I would say it is rather a
>severe
>> problem.
>>
>
>At 350mph to 400mph few other attack angles would be possible. I
>expect angels outside of that could be defended by waist guns or
>similar low drag arrangements.


The speed of the plance can't make up for the restricted field of fire of the
guns. And no wayion hell can the waist guns overlap the tail gun to compensate
for a limited f ield of fire..Guns designed with limited fields of fire are
poorly designed and/or poorly installed. Some day I'll tell you about the B-26
nose gun mess. But not now.ONemore pooint. Guns ar enot supposed to have
limited fields of fire. They are supposed to have the widest fields possible.
Got it?


Arthur Kramer
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

[[email protected]]

(ArtKramr) wrote:

>>Subject: Re: The prone postion for tail gunners versus turrets.
>>From: (The Enlightenment)
>>Date: 7/21/03 6:04 PM Pacific Daylight Time
>>Message-id: >
>>
(ArtKramr) wrote in message
>...
>>> >Subject: Re: The prone postion for tail gunners versus turrets.
>>> >From: "Keith Willshaw"
>>> >Date: 7/21/03 4:06 AM Pacific
>>>
>>> > in the tail or (nose) in a prone position opperating a gun manualy. I
>>> >> can't see a problem with this except that the allowable movement would
>>> >> probably be limited to +/- 25 degrees.
>>> >>
>>>
>>> Limited action on a tail gun no problem???? I would say it is rather a
>>severe
>>> problem.
>>>
>>
>>At 350mph to 400mph few other attack angles would be possible. I
>>expect angels outside of that could be defended by waist guns or
>>similar low drag arrangements.
>
>
>The speed of the plance can't make up for the restricted field of fire of the
>guns. And no wayion hell can the waist guns overlap the tail gun to compensate
>for a limited f ield of fire..Guns designed with limited fields of fire are
>poorly designed and/or poorly installed. Some day I'll tell you about the B-26
>nose gun mess. But not now.ONemore pooint. Guns ar enot supposed to have
>limited fields of fire. They are supposed to have the widest fields possible.
>Got it?
>
>
>Arthur Kramer

Jesus...sounds kinda unhealthy to have aircraft machine guns with
an unrestricted field of fire...no?.
--

-Gord.

[Cub Driver]

I think a seated gunner has a much better range of vision and motion
than one lying prone.

I think of the B-17 tail gunner as seated. Weren't the guns beneath
him and he aimed with a little stick?

Japan had no heavy bombers, and Germany and Italy didn't have much in
that line. Japanese bombers often had a "stinger" in the tail. It
tracked the dorsal (do I mean dorsal? -- upper) gunner's weapon, and
he could fire it with a lanyard for the times when he might otherwise
shoot off his own tail. The Navy Betty I think had a genuine tail
gunner, but the Japanese did not go in for mechanical turrets. You
just sat out there in the breeze.

The Japanese even went in for "dust bin" guns, essentially a hinged
platform that could be lowered from the bottom of the aircraft, The
gunner (presumably strapped down) lay on this "door" and fire away. It
would be raised when the plane wanted to increase speed for a getaway.

Several of the AVG Flying Tiger pilots in their diaries or combat
reports mention their shock when they see a Japanese gunner slump
dead. He was that much out in the open.

all the best -- Dan Ford
email: www.danford.net/letters.htm#9

see the Warbird's Forum at http://www.danford.net/index.htm
Vietnam | Flying Tigers | Pacific War | Brewster Buffalo | Piper Cub

[John Halliwell]

In article >, The
Enlightenment > writes
>However I still suspect that a simple rear gunner lieing in the prone
>position could be built not to reduce speed too much.

I guess it puts a lot of weight (the gunner) very far back, which would
probably have large effects on handling. Just fixed guns with lots of
tracer might be effective, especially as a tail chase was quite likely.

The ultimate gunnery system in WWII, particularly for night ops was
probably the radar guided system used on some Lancasters (Village Inn
perhaps?). Whether this could have been incorporated into a small tail
turret remotely controlled from the cockpit is another question.

--
John