North American Aviation NA-98X 'Super Strafer'

[robunos]

From the 'Old Machine Press' blog :-

http://oldmachinepress.wordpress.com/2012/09/02/na-98x-super-strafer/

North American Aviation NA-98X 'Super Strafer'

A 1943, North American Aviation (NAA) design for an improved attack bomber that would provide the firepower of the B-25H but with substantially improved performance. This was intended as an alternative to the delayed Douglas A-26B Invader.
Power was to be provided by a pair of Pratt & Whitney R-2800 air-cooled radial engines housed inside low-drag cowlings and driving a pair of four-blade propellers with spinners.
The twin fins were to be replaced by a conventional single-tail, altering one of the B-25’s most notable characteristics. The wing tips were to be square-cut, permitting the ailerons to be extended farther outboard to provide better roll control. Armament improvements were to include a computing gun sight and a new low-drag canopy designed by North American for the top turret. Otherwise, the aircraft had the same armament as the B-25H, including the 75mm cannon.
In early 1944, a less ambitious alternative was submitted to the Army Air Forces. This proposal was to take the existing B-25 airframe and apply many of the enhancements from the improved NAA design. A B-25H-5 (serial number 43-4406) was chosen as a testbed for the modifications, which no longer included the single tail and four-blade propellers. It was given the designation NA-98X by NAA and nicknamed Super Strafer. Since it was not designed for any USAAF requirement, it never carried an official USAAF designation.

The first flight of the NA-98X took place on March 31, 1944, and it was found that the Super Strafer performed well. However,on April 24, 1944, the aircraft suffered a major structural failure and crashed, killing both pilots on board. Following the crash, all further work on the NA-98X project was abandoned even though the RAF had shown interest after a test flight.

See also http://www.secretprojects.co.uk/forum/index.php/topic,242.msg42723.html#msg42723 replies #56 and #'57.

cheers,
Robin.

 

[blackkite]

The empennage was changed to a conventional single-tail? :-[ altering one of the B-25’s most notable characteristics

 

[famvburg]

I wonder what's so low-drag about that canopy.

 

[Stargazer]

The empennage was changed to a conventional single-tail? :-[ altering one of the B-25’s most notable characteristics

The testbed retained the regular tail configuration:

[quote author=robunos]In early 1944, a less ambitious alternative was submitted to the Army Air Forces.[/quote]

 

[robunos]

I wonder what's so low-drag about that canopy.

I thought that, too, when I looked at the image. I can only assume, that as the turret was supplied by the turret manufacturer as GFE, that it was not possible for it to be modified...

cheers,
Robin.

 

[WJPearce]

Hello,

The "low-drag canopy" for the top turret was part of the proposed aircraft (drawing) and not on the modified B-25H (images). The cut and paste from the original site chopped the article up a bit. You can't tell from the drawing as posted but in looking at a clearer version, the top turret appears to be smaller, with just enough room for the gunner's head and the font panel (between the guns) is slopped. Since it was just a drawing, I do not know how NAA planned to get over the GFE issues.

Here are the pertinent parts from the original article to hopefully clear things up.

In 1943, North American Aviation (NAA) created an internal design for an improved attack bomber that would provide the firepower of the B-25H but with substantially improved performance. This evolution of the B-25 line was intended as an alternative to the heavily-armed and delayed Douglas A-26B Invader. Power was to be provided by a pair of Pratt & Whitney R-2800 air-cooled radial engines housed inside low-drag cowlings and driving a pair of cuffed, four-blade propellers with spinners. The empennage was changed to a conventional single-tail, altering one of the B-25’s most notable characteristics. The wing tips were square-cut like a P-51’s, rather than rounded, permitting the ailerons to be extended farther outboard to provide better roll control. Armament improvements were to include a computing gun sight and a new low-drag canopy designed by North American for the top turret. A compensating sight was to be used in the tail turret and illuminated reflector optical sights for the waist guns. Otherwise, the aircraft had the same armament as the B-25H, including the 75mm cannon.

In early 1944, a low-cost and less ambitious alternative was submitted to the Army Air Forces. This proposal was to take the existing B-25 airframe and apply many of the enhancements from the NAA internal design. A B-25H-5 (serial number 43-4406) was chosen as a testbed for the modifications, which no longer included the single tail and four-blade propellers. It was given the designation NA-98X by NAA and nicknamed Super Strafer. Since it was not designed for any USAAF requirement, it never carried an official USAAF designation.

The new aircraft was powered by a pair of 2,000 hp Pratt & Whitney R-2800-51 engines with 15 minutes of water injection, all housed in A-26 cowlings. Large conical spinners were used on the three-blade propellers. The squared wing tips allowed the ailerons to be extended by one foot, and the control system was changed to lighten the stick forces. Except for the removal of the fuselage blister gun packs, the aircraft had the same armament as the B-25H.


Regards,

 

[robunos]

The cut and paste from the original site chopped the article up a bit.

Bill,
I didn't post the text from your blog verbatim, in part because I wanted people to go there and read it for themselves, but at the same time, the policy here is to not just post a bare link, as these can disappear, but post some text and images, to be retained on the server.

cheers,
Robin.

 

[WJPearce]

Bill,
I didn't post the text from your blog verbatim, in part because I wanted people to go there and read it for themselves, but at the same time, the policy here is to not just post a bare link, as these can disappear, but post some text and images, to be retained on the server.

cheers,
Robin.

Hello Robin,

Absolutely not a problem. I did not mean to imply that you did a poor job of bringing the info to this site. It just appeared to me that some were getting the wrong impression and I wanted to correct it. I'm glad people are stumbling upon the articles on my humble site and spreading them around the net. I just hope I got all my info (and spelling) right.

Thank you,

 

[lark]

A bit additional info...

A separate proposal for a Double Wasp Mitchell was a B-25J with R-2800's and 18 MG's (?)
(question mark by me)

*Known as the NA-108X Strafer Bomber ,this was to have a single vertical tail.

From 'American Bomber Aircraft Development in WW2' By Bill Norton-Midland Publ. page 39

The NA-108X is also mentioned in 'Wings of Fame' vol 3 - B-25 Mitchell Variants page 139.

Question: Could the single tail attack aircraft depicted on
the artist impression in the first post by Robunos be the NA-108X ?

 

[Stargazer]

A separate proposal for a Double Wasp Mitchell was a B-25J with R-2800's and 18 MG's (?)
(question mark by me)

18 machine guns?? Wow. That would have been a super-super-Strafer!

 

[J.A.W.]

AFAIR, the flak in the ETO was too hot for 'super-strafer' type ops by such aircraft.

Even the P-38 & Mosquito suffered prohibitive losses when used in this way (anti-shipping excepted)..

The Luftwaffe came to the same conclusion - with respect to CAS losses to its twin engine types too.

The A-26, when it did show up - was used in the medium bomber role (as was the P-38!) like-wise.

 

[lark]

Star...,I wonder were they could put the 18 MG's , hence my question mark..

 

[Stargazer]

Star...,I wonder were they could put the 18 MG's , hence my question mark..

Indeed! Perhaps it was a typo for "8" (which, given the size of the aircraft, would already be quite a feat to fit in the airframe!)

 

[Orionblamblam]

Star...,I wonder were they could put the 18 MG's , hence my question mark..

Indeed! Perhaps it was a typo for "8" (which, given the size of the aircraft, would already be quite a feat to fit in the airframe!)

18 make sense. Two in the tail turret, two waist guns and two in the top turret account for six of them. In the illustration, there are two MGs on either side of the nose in "blisters," and four more projecting from the nose (a total of 14 MGs), with a 75 mm cannon. Replace the cannon with only 4 more .50 M2's and you have your 18.

 

[CostasTT]

The standard B-25J (solid nose) had 8 in said solid nose, 4 in blister packs, 2 each in the dorsal and tail turrets, plus 2 in the waist positions. Total 18. So the number is perfectly realistic.

 

[Stargazer]

The standard B-25J (solid nose) had 8 in said solid nose, 4 in blister packs, 2 each in the dorsal and tail turrets, plus 2 in the waist positions. Total 18. So the number is perfectly realistic.

Thanks CostasTT. I wasn't aware there were that many on board a Mitchell. Wow!
And thanks Orionblamblam, too.

 

[lark]

Spread over the whole airframe , it makes sense indeed.

 

[Jemiba]

IIRC in the case of the A/B-26 Invader, the dorsal turret could be locked in the forward
position and triggered by the pilot. So forward firing of the turret guns should have been
possible here, too, ahough maybe still triggered by the gunner, bringing the number of
guns firing directly forward to 14 !

 

[CostasTT]

The standard B-25J (solid nose) had 8 in said solid nose, 4 in blister packs, 2 each in the dorsal and tail turrets, plus 2 in the waist positions. Total 18. So the number is perfectly realistic.

Thanks CostasTT. I wasn't aware there were that many on board a Mitchell. Wow!
And thanks Orionblamblam, too.

You are welcome. The solid nose Invaders also had a similar number of guns: 6 (early) or 8 (late) nose guns, 4x2 underwing gondolas (early) or 6 wing guns (late), plus two guns in each turret. I don't recall seeing a 8-gun nose/4-underwing pod combo, which would raise the number of guns to 20, but according yo my books the 6-gun wing appears to predate the 8-gun nose.

 

[lark]

Now that the armamant question is solved , can we
conclude that the single tail aircraft in Robunos initial post is
the NA-108X Strafer Bomber mentioned by Bill Norton in his book?

 

[joncarrfarrelly]

Now that the armamant question is solved , can we
conclude that the single tail aircraft in Robunos initial post is
the NA-108X Strafer Bomber mentioned by Bill Norton in his book?

Not really as the illustration in question also appears in Norm Avery's North American Aircraft book;
on the same page as a more radical tandem V-3420 powered attacker, and is captioned as leading
to the NA-98X:

 

[lark]

I have the book also with these illustrations, but it puzzles me
that the NA-98X flew with a twin tail and shortened wings...

 

[Stargazer]

Now that the armamant question is solved , can we conclude that the single tail aircraft in Robunos initial post is the NA-108X Strafer Bomber mentioned by Bill Norton in his book?

Not really as the illustration in question also appears in Norm Avery's North American Aircraft book;
on the same page as a more radical tandem V-3420 powered attacker, and is captioned as leading to the NA-98X.

As you rightly say, the single-fin artist's concept pre-dates the built NA-98X itself and is described by Norm Avery as "B-25H based". Neither Avery's book nor the NA- designations index in Kevin Thompson's Volume 2 mentions an "NA-108X". If such a designation ever existed, maybe NAA considered at some point to create the Strafer prototype by modifying a B-25J (NA-108) instead of a B-25H (NA-98)?

 

[lark]

There's light at the end of the tunnel...!
Thanks Star..

 

[Steve Pace]

In my book B-25 MITCHELL in the Warbird History Series published by Motorbooks International in 1994 I described the aircraft in question as follows:
The Strafer-Bomber
On 17 March 1944 NAA's Inglewood, California engineering department completed a presentation pamphlet on a new type of Strafer-Bomber airplane based on the NA-108 (B-25J) version of the Mitchell. With the approval of NAA management the Strafer-Bomber idea moved forward.
As proposed, the Strafer-Bomber was to have a five-man crew: pilot, navigator, flight engineer/gunner, radio operator/waist gunner, and tail gunner.
Its maximum armament, as projected, was to be 18 .50 caliber machine guns with 7,200 total rounds of ammunition. This consisted of eight fixed forward-firing nose guns (400 rounds each), four fixed forward-firing side guns (400 rounds each), two movable upper turret guns (400 rounds each), two movable waist guns (200 rounds each), and two movable tail guns (600 rounds each).

I hope this clears thing up for you all. -Steve Pace

 

[Stargazer]

I hope this clears thing up for you all. -Steve Pace

It does indeed, thanks Steve! This shows how no book on any subject can ever be definitive as certain authors manage to dig out stuff that others haven't, and reversely. Only the three books combined give us the whole picture!

And so in chronological order we have 1°) USAAF request (late 1943? number?) > 2°) NA-98X Super Strafer proposal (early 1944) and prototype modification > 2°) alternate NA-108X Strafer-Bomber proposal in pamphlet from (March 17, 1944) > 3°) first flight of NA-98X (March 31, 1944) > 4°) crash of NA-98X > 5°) cancellation of whole program by USAAF.

It would be interesting to know if other companies responded to that USAAF request for proposals and what the specifics of it were.

 

[Steve Pace]

NA-98X was prototype for B-25H. -SP

 

[Stargazer]

NA-98X was prototype for B-25H. -SP

I guess when Avery writes about the NA-98X program being canceled, he only talks of the "Super Strafer" variant. Still, your claim that NA-98X was the "prototype for B-25H" comes in direct contradiction with Norm Avery's claim that the NA-98X "was modified from B-25H, 43-4406". Who's right, who's wrong? Not being a Mitchell specialist, I'll leave it to others to answer.

Meanwhile, here is the paragraph about the NA-98X from his book North American Aircraft 1934-1998 Volume 1 (Narkiewicz-Thompson):

Early in 1944, in response to a USAAF request, North American submitted a proposal for a B-25 powered by 2000-horsepower Pratt & Whitney R-2800-51 engines. With the course of the war still not decided, a more powerful variant of the Mitchell offered great possibilities, especially as a high-speed strafer with the eight-gun nose. Nicknamed Super Strafer, a prototype of the new design, the NA-98X, was modified from B-25H, 43-4406. Visible differences from the standard H model were ailerons of increased span, square wing tips, Douglas A-26 engine cowlings and prominent propeller spinners. To avoid restructuring the wings, the test plane was re-lined at 340 mph, as the desired data could be obtained within that parameter.
When test pilot Joe Barton made the first flight on March 31, he realized what the B-25 could have been, had the R-2800 engines been available at its inception. After numerous qualitative flights by NAA pilots, the test program was taken over by USAAF Major Perry Ritchie, who repeatedly exceeded flight restrictions. On April 24, after several low-level, high-speed passes over the NAA flight ramp, he pulled up into a steep spiral climb. Both wings separated at the landing-light stations and the plane crashed, killing Ritchie and a crewman. The NA-98X program was canceled, even though the design was not at fault.

 

[Steve Pace]

B-25H (43-4406) was fitted with R-2800 engines and crashed during flight test. -SP

 

[GTX]

Related?

 

[EwenS]

The standard B-25J (solid nose) had 8 in said solid nose, 4 in blister packs, 2 each in the dorsal and tail turrets, plus 2 in the waist positions. Total 18. So the number is perfectly realistic.

Thanks CostasTT. I wasn't aware there were that many on board a Mitchell. Wow!
And thanks Orionblamblam, too.

You are welcome. The solid nose Invaders also had a similar number of guns: 6 (early) or 8 (late) nose guns, 4x2 underwing gondolas (early) or 6 wing guns (late), plus two guns in each turret. I don't recall seeing a 8-gun nose/4-underwing pod combo, which would raise the number of guns to 20, but according yo my books the 6-gun wing appears to predate the 8-gun nose.

The 6 internal wing guns replaced the underwing gun pods from the A-26B-50 block and the A-26C-45 block in March and May 1945 respectively. The 8 gin nose was then introduced on 246 A-26B-61 and -66 block between May and Aug 1945 to replace the 6 gun nose of earlier production. Post war the 8 gun nose was retrofitted to an unknown number of earlier airframes.