XB-28

[KJ_Lesnick]

My question about the North American XB-28 is fairly simple: I know the basic purpose of the plane, a high-altitude B-25 successor.

The problem is I do not know what the bomb-load is because of conflicting information, sometimes on the same source: 4,000 pounds is the normal cited load, yet 6,000 pounds is mentioned as well.

I'm not sure what to make of this: Does this mean

• That the normal maximum internal load is 4,000 with the ability to carry 2,000 external?
  
• The normal maximum internal load is 4,000 with the overload provision for 6,000 internal?
  
• The normal load intended for combat would be 4,000 pounds, but maximum was 6,000?
  

[kerick]

My search revealed that the 4000 lb figure is probably the most accurate, or at least the most commonly quoted. The 6000 lb figure is either a misprint or wishful thinking. Even if the aircraft could lift it the target better be pretty close to the end of the runway. The 2000 lb figure is probably used when the target is at maximum range. Every aircraft has to trade payload for range, whether its bombs, passengers or cargo. So 2000 lb for long range, 4000 lb for not so long. Range in between means bombload in between. I saw no mention of external loads. For its mission I would not expect that. Hope this helps.

[jcf]

4000lb max: twenty 100lb or eight 300lb or two 1,000lb or two 2,000lb.

Max combat range 2040 miles with 600lbs.

[KJ_Lesnick]

JCF,

1. Maximum range was 2,040 miles with 600 pounds of bombs: Is that a typo?  Can the A-26 do that (ferry range is 3,200, 1,400 to 1,800 with 3,000 if I recall right)
2. Why was it called a medium when the A-26 wasn't?

[jcf]

No, it's not a typo.

Do the math, 2,040 miles at over 370mph at 35,000 feet = a lot of fuel, fuel = weight.

Perhaps because the B-28 had a B prefix and the A-26 had an A prefix, and as such was outside of the bomber classifications? 

[KJ_Lesnick]

JCF

No, it's not a typo.

Okay, but I'd almost swear on Joe Baugher's site, it said 2,040 miles with 4,000 pounds of bombs

Perhaps because the B-28 had a B prefix and the A-26 had an A prefix, and as such was outside of the bomber classifications? 

Actually, aside from your snide remarks: The A-26 was generally considered to be a light-bomber as well as an attack plane.  It did have a maximum internal load of 4,000 pounds, a total of 6,000 pounds, and at the XA-26A, had a range of 1,800 miles with 3,000 pounds of bombs.  I would not be surprised if it possessed a twin-stage supercharger (which is not a big "if" as the A-20A had them), or a turbocharger, it would have been able to have flown as far (2040 miles) with a greater load than the XB-28.

[wuzak]

The A-26 was generally considered to be a light-bomber as well as an attack plane.

By whom?

I would not be surprised if it possessed a twin-stage supercharger (which is not a big "if" as the A-20A had them), or a turbocharger, it would have been able to have flown as far (2040 miles) with a greater load than the XB-28.

The A-20A had Wright R-2600s.
The A-26 had Pratt & Whitney R-2800s.

The A-20A had single stage two speed engines.
The A-26 had single stage two speed engines.

Turbocharger installations are heavy, particularly for teh R-2800, requiring the C-series turbo.

What the turbo does not help (at least directly) is take-off power. Which is a key to an aircraft's ability to lift a load.

[famvburg]

A turbo does help for take-off in hot and high conditions.

[KJ_Lesnick]

wuzak

The A-20A had Wright R-2600s.
The A-26 had Pratt & Whitney R-2800s.

Correct

The A-20A had single stage two speed engines.
The A-26 had single stage two speed engines.

Really, I thought the A-20 had a two-speed blower and the other single-stage.  Regardless, twin-stage, twin-speed with inter-cooling would have helped.  Sounds advanced but the F4U had two-stage superchargers, and intercoolers, so it can be done.

Turbocharger installations are heavy, particularly for teh R-2800, requiring the C-series turbo.

What is a C-series?

[wuzak]

Turbocharger installations are heavy, particularly for teh R-2800, requiring the C-series turbo.

What is a C-series?

There were two major types of turbo built by GE during the war - the B-series and C-series.

I can't recall if they were sized based on a capacity range or power capability, but the C-series was for bigger engines, such as the R-2800.

The R-3350 in the B-29 used two B-series turbos.

The R-2800 in the P-47 used a C-series (or CH, for high altitude).

The V-1710s in the P-38 used a B-series.

The R-1830s in B-17s used B-series.

The R-1830s in B-24s used B-series.

The R-4360 in the XF-11 Rainbow and XF-12 used two B-series - at least I don't think they were C-series. I'd have to check.

[jcf]

http://www.enginehistory.org/Turbochargers/GETurbochargerData.jpg
From the AEHS site.

[KJ_Lesnick]

JCF,

Thanks