Attack and Bomber Classifications

[KJ_Lesnick]

pyro-manic

The point is that the "range of standards" is so diverse that it's completely pointless to try and call them standards.

Actually, I've done some guesstimates a few posts in.  You're telling me that's as good as it got?

As to your question about the A-20, it was a light bomber because it was lighter than the medium bombers of the time.

1. What other medium-bombers existed in the era?

2. Was the DB-7 and A-20 considered the same aircraft according to the USAAF or RAF?

3. The earlier payloads carried by the A-20 (around 1,760 lbs) would increase to around 2,400 by the time the A-26C was flying: Why was the payload lower from the outset?

→ Was it due to the size of the bomb-bay changing (i.e. repositioning of structural members, fuel-tanks above the bay)?
→ Was it due to the arrangement of the bomb-shackles (allowing more bombs to be shoehorned into the bay)?
→ Was it due to the structural strength of the landing gear?
→ Was it due to the structural strength of the wing and fuselage?

Yet again, I suggest you get hold of a book on the A-20 to find out all the details about development and differences between the variants. I suggest this one as a starting point: http://www.amazon.com/Douglas-Havoc-Boston-Crowood-Aviation/dp/1861266707

I'll put it on my list...


Librarian

I'm no expert on these matters but the Americans produced a few 'pocket-bombers' for the export market...Boston/Havoc, Baltimore, Maryland.

Their size was based on export requirements?

The Douglas really came into its own when Kenney and the 5th AF started using them as strafers.

Following the TV Trope "More Dakka".

When Douglas shut down A-20 production to concentrate on the Invader he was VERY unhappy, tried to keep the A-20 production going as he had a thorough dislike for the A-26, as did all his pilots.

Why?

[Librarian]

I'd honestly leave the answer to more informed sources, my memory now is very poor for subjects I used to throughly enjoy reading about. I'd suspect the answer is yes and WWII got in the way. All three designs were very heavily used over the Med/Africa/Italy( the latter not so much)...maybe range played a part.

An aircraft that hasn't been mentioned and really chucks the cat amongst the pigeons when dealing with specs etc is the HE177. As a redesigned a/c with four SEPERATE engines it was apparently rather good. High level interference turned a promising design into a curate's egg.

[pyro-manic]

The point is that the "range of standards" is so diverse that it's completely pointless to try and call them standards.

Actually, I've done some guesstimates a few posts in.  You're telling me that's as good as it got?

Yes. Drawing up your hoped-for exacting standards and specifications would be pointless, due to the constant, rapid progress of technology, tactics and requirements. By the time some committee had decided on them, they'd be utterly obsolete and useless, and a whole new set would have to be drawn up and the cycle repeated. That's before you include unforeseen private developments like, for example, the Mosquito, which deliberately broke the rules and was very successful as a result.

[KJ_Lesnick]

pyro-manic

Yes. Drawing up your hoped-for exacting standards and specifications would be pointless, due to the constant, rapid progress of technology, tactics and requirements.

Even in the interwar period?  From the 1930's to 1935 the payloads seemed about the same for the light bomber category.

That's before you include unforeseen private developments like, for example, the Mosquito, which deliberately broke the rules and was very successful as a result.

It deliberately broke the rules in that it had no defensive armament and was made of wood; I don't recall it having any issues with payload as a light bomber (1,000 pounds initially, though bumped up to 2,000 due to a new bomb). 

As I recall a medium bomber is generally classified as a plane that can deliver a medium payload a medium distance, correct?

[chiglet]

It deliberately broke the rules in that it had no defensive armament and was made of wood; I don't recall it having any issues with payload as a light bomber (1,000 pounds initially, though bumped up to 2,000 due to a new bomb). 

According to Wiki
The Mossie had a Range of 1300nm with a bomb load of 4000 lb

The B25 [classified as a Medium bomber] had a range of 1174 nm with a bomb load of 3000 lb
In mitigation, the B25 had 6 crew, the Mossie had 2

[KJ_Lesnick]

The Mossie had a Range of 1300nm with a bomb load of 4000 lb

Initially the load of was only 1,000 pounds (4 x 250), it was quickly updated with a redesigned bomb that weighed 500 pounds and had a shorter tail, so it was now 2,000 pounds (4 x 500), later on 2 x 500 pounders were added to the wings which increased the load to 3,000 pounds; a pair of drop tanks could be carried there in lieu.  The fuel tankage inside the plane was increased as time went online allowing it to fly further, and and eventually more advanced merlins were added increasing critical altitude (the exhaust pipes were also reshaped to produce some thrust).

The 4,000 pound load might have been specific to the ability to carrying a 4,000 pound cookie: It required a bulged bomb-bay door, and a slight reduction in fuel capacity as well if I recall.

The B25 [classified as a Medium bomber] had a range of 1174 nm with a bomb load of 3000 lb

I thought the first B-25's had longer ranges...

[pyro-manic]

That's before you include unforeseen private developments like, for example, the Mosquito, which deliberately broke the rules and was very successful as a result.

It deliberately broke the rules in that it had no defensive armament and was made of wood; I don't recall it having any issues with payload as a light bomber (1,000 pounds initially, though bumped up to 2,000 due to a new bomb).  

It broke the rules in that it had much, much greater performance than a "traditional" bomber design with defensive armament, as it dispensed with those and used the resultant weight reductions to achieve much higher speed and greater range and payload. Had de Havilland stuck to "the rules" and built a traditional light bomber then the result would have been nowhere near as effective, useful or flexible.

The 1930s were a period of enormous advances in technology. You go from wire-and-canvas biplanes to all-metal monocoque aircraft with 1000hp engines. To suggest that a specification drawn up in 1930 would be even slightly relevant at the end of the decade is frankly daft. As an example, take a look at this list (Air Ministry specifications for the 1930s) and compare some aircraft at the top of the list to those towards the end....

[Librarian]

Librarian

When Douglas shut down A-20 production to concentrate on the Invader he was VERY unhappy, tried to keep the A-20 production going as he had a thorough dislike for the A-26, as did all his pilots.

Why?

All I remember was that the A-26 produced no gains in performance/payload over the A-20 whilst being a more manpower intensive aircraft to both fly and maintain. The view from the cockpit, for the pilot, whilst adequate port was non-existant starboard...the A-20 was a narrow cockpit single seater with good visibility both sides.

A-26 production was from two factories, I think one was Tulsa. One concentrated on Bs and the other Cs. Kenney very reluctantly took the plane (they'd had 2 or 4 to try out) but demanded a 'Kenney Special'. Eight gun nose, removal of wing guns/pods, removal of lower turret with an extra fuel tank and a redesigned canopy. These were produced and delivered in overall olive-drab but didn't reach the Pacific before the end of hostilities. A very good book on the subject with a comprehensive list of serial numbers for each aircraft was published by Crowood...I think its quite rare now on the collectable scene.

Model companies still get it wrong. This is Italeri's new boxing

http://www.model-making.eu/products/A-26B-INVADER.html

If you look at the 1945 Phillipines machine that was one of Kenneys Specials but they've put in the lower turret....it shouldn't be there. The planes received a neutral grey underside on arrival so that is correct.

[wuzak]

3. The earlier payloads carried by the A-20 (around 1,760 lbs) would increase to around 2,400 by the time the A-26C was flying: Why was the payload lower from the outset?

→ Was it due to the size of the bomb-bay changing (i.e. repositioning of structural members, fuel-tanks above the bay)?
→ Was it due to the arrangement of the bomb-shackles (allowing more bombs to be shoehorned into the bay)?
→ Was it due to the structural strength of the landing gear?
→ Was it due to the structural strength of the wing and fuselage?

I'd suggest due to power.

And/or lowered safety margins for MTOW.

[KJ_Lesnick]

Wuzak

1. Why was the DB-7 able to carry 2,000 pounds and the A-20 carried less?
2. Was the DB-7 and A-20 considered by the USAAF and/or RAF to be variants of the same plane, or different planes?
3. When you say safety margins for MTOW, what do you mean?

[wuzak]

1. Why was the DB-7 able to carry 2,000 pounds and the A-20 carried less?

Weight.

The A-20 weighed more emoty than the DB-7 did gross. Some of that is due to the heavier engines, but no doubt due to additional equipment - such as self-sealing fuel tanks.

2. Was the DB-7 and A-20 considered by the USAAF and/or RAF to be variants of the same plane, or different planes?

I guess so. The A-20 was the DB-7 built to USAAF requirements.

3. When you say safety margins for MTOW, what do you mean?

I am suggesting that theye became more comfortable with higher weights for take-off as they gained experience with the aircraft.

[KJ_Lesnick]

Weight.

The A-20 weighed more emoty than the DB-7 did gross. Some of that is due to the heavier engines, but no doubt due to additional equipment - such as self-sealing fuel tanks.

But wouldn't the extra engine power compensate for the extra weight?  Unless you're talking about the strength of the landing gear...

I guess so. The A-20 was the DB-7 built to USAAF requirements.

So it was considered the same basic type?

I am suggesting that theye became more comfortable with higher weights for take-off as they gained experience with the aircraft.

So you're talking about takeoff-speeds, landing-speeds, and controllability speeds?

[chiglet]

So you're talking about takeoff-speeds, landing-speeds, and
controllability speeds?

Not really. VR/V2 VRef and VMCA are ALL a factor of weight and temperature
eg, V2 at 15000 lbs  20 deg C is [say] 115 mph at 17000 lbs is say 124 mph for the same parameters

[Librarian]

Also, the A-20 had a heavier power-operated turret, the DB-7/Boston lot had manual.

[jcf]

The power turret was introduced at block A-20G-20-DO, earlier variants and A-20G blocks -1 through -15 had manual guns.

Joe Baugher runs down the DB-7/Havoc/Boston/A-20 similarities differences here:
http://www.joebaugher.com/usattack/a20.html

http://www.joebaugher.com/uscombataircraft.html