A proper heir to the SBD

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tomo pauk

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Apr 3, 2008
Or, something else to design and manufacture instead of the SB2C. The 1st flight needs to happen before March 1st 1941, ie. a tad later than it was the case with SB2C, so the engineers have a bit less of a pressure to make it work. It needs to have a bomb bay of at least same size like it was the case with the new-gen attackers for the USN. Powered by the engines that US industry can provide in good numbers, using aerodynamics, materials, propellers, guns and electronics of the day. At least a 2-seater, folding wings are mandatory. Range of at least 1000 miles with the full bomb bay and internal fuel, and 1500 with drop tanks added. Obviously, fully carrier capable, even with big take off weights. Max speed of at least 320 mph bombed-up & clean, while being docile at low speeds.
In service before May 1942.
 
Hi,
Looking at other US single engine planes attack planes from that timeframe I see;

Name/ID 1st Flight In service HP Max Wt
TBF Avenger 8/7/41 Mid 1942 1700 15,536 lb
TBY Sea Wolf 12/22/41 ------ 2100 18,940 lb
SB2A Buccaneer 6/17/41 1943-1944 1700 14,289 lb
SB2C Hell Diver 12/18/40 ~11/11/43 1900 16,616 lb
A-31 Vengeance 3/30/41 5/42 1600 14,300 lb

All but the Sea Wolf is listed on Wikipedia as having some form of the Wright R-2600 engine (the Sea Wolf is listed as using the P&W R-2800 engine). As such I would probably start with one of those two engines.

Additionally, at his time it appears that both technology and operational theory/tactics were evolving greatly. As such I'd suspect that if you were to try and stick closely to your initial design requirements (with very limited in-process design changes) you could produce an aircraft more quickly but it may be more likely to either be somewhat outdated when built or it may become more quickly outdated and less flexible in service. So there will likely be a trade-off between how quickly you want it in-service and how state-of-the art it is when entering service.

I suspect though that there may be a couple areas that you could try and pin down early to hopefully try and address some of these issues, such as;
  • bomb capability (Wing) - I would try and avoid anything like special recesses in the wings for only specific size/shaped bombs and instead focus on designing the wings to fit either some sort of standardized fitting general type lighter bombs or drop tanks
  • bomb capability (Centerline) - I would likely think that a bomb-bay would be best at this point in time, and that there would probably be a desire to make it capable of the largest bomb typically carried aboard a carrier, but other design factors may limit that.
  • wing location - the use of an internal bomb bay make result in the need to mount the wings at a mid fuselage height.
  • wing fold - a folding wing would seem likely necessary for the size of plane at this time if the plane is to be carrierborne.
  • max length - although there may be a desire to keep length short for hangar storage and to possibly for more on an elevator lift, shortening an airframe can cause other design issue and it would probably be best to not overly constrain the designhere if possible. All the planes above, except for the Hell Diver appear to be about 39-40ft in length, which sounds like a good target for any alternate design.
  • wing area - I would suggest something in line with the other designs listed above would be a good starting point
  • Other features - I would also probably suggest trying to avoid anything potentially overly complex like
    • revolving mulitgun powered turrets
    • complex landing gear retraction mechanisms
    • wing mounted cannons (at least initially)
Regards

Pat
 
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From all the above it looks like maybe something along the lines with a revised (perhaps slightly smaller) two seat Sea Wolf might be the best bet, but from what I understand limited production capacity in the US meant that the Sea Wolf production was delayed until a new factory in Allen Town PA was completed in late 1943. As such other similar planes could potentially also be delayed. I believe that Brewster production was also delayed somewhat by the need to build a new plant in Bucks County PA.
 
Pity they couldn't have started the AD-1 sooner. That would have been quite the plane in 1942 though without the R-3350 to give it all that oomph, I doubt it would have been practical.
 
The small TBU certainly has an appeal.
How about something like the Hell-bomber (tm)? A Hellcat lookalike, with a bomb bay under the level of the wings. It already has Fowler flaps so the low-speed abilities will be fine. Fuel tanks go in the wings (as much as Grumman does not like the idea ;) ). Should be a speedy attacker even with an 1-stage R-2800.
Another suggestion might be the 2-seat Corsair, with the bomb panier/bomb bay under the fusleage. Relocate the intercoolers and oil cooler under the engine a-la Hellcat if needed, so more fuel can be packed inside.
 
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It's a shame the Curtiss SC Seahawk showed up so late.
The two seat SC-2 may have been a candidate.
While it had either fixed gear or a float, it may have been possible to have retracting main gear designed in.
It did have folding wings, too.

If Wright can whip up their fine 800TSBA1 turbocharger earlier, why not?
(that turbo was with hollow bladed turbine, enabling the close-coupled installation to the engine; about 1000 was produced for the SC-1; unfortunately, there is no single SC-1 remaining today)
The U/C retracting - something like what the P-36/-40/F4U/F6F had? It can also double as the dive brake.
Another engine of choice might be the 2-stage supercharged R-1820-48, one such engine was delivered in January 1941. Or indeed the 2-stage R-1830.
 
Hi,
One of the things that stuck out to me about the OP was the 320 mph top speed requirement. Looking at the SBD, SB2A, SB2C, A-31, TBF and TBY the base plane that gets closest to the appears to be the TBY at 312 mph (according to Wikipedia) [with a 2100 HP engine] whereas the Dauntless (SBD) with a 1200 HP engine is listed as having a top speed of 255 mph. As such, I'd suspect that it would likely be out of the realm of what was capable at the time to try and re-engine the SBD up to meet the OP's requirements.

As for a two-seat F6F or F4U I'd suspect that both could be feasible, though within a few years during the war single seat versions of these planes were potentially close to being just as capable at attack as earlier war two seat aircraft which may raise questions as to why build a two seat version (though I guess that would be using hind sight that may not have been available in the early 1940s).

Pat
 
I don't see how it could have practically been done on that time frame. The closest I can come up with is to put a rocket booster in the tail of an SBD. There are all kinds of things wrong with this idea, but it's the best I can do.
 
So the OP is looking for an aircraft with first flight early 1941.

Not much consideration has been given to the ships that this aircraft is to fly from. That produces some physical limits on your design, just to get it to sea.

In 1939/40 the USN are working on the design of the Essex class. 11 ships ordered in 1940 with the first laid down April 1941. The detailed Spec for these ships, issued to the builders in 1941, contains a number of items that directly affects the design of any aircraft intended to operate from them.

Weight limits
The hydraulic aircraft lifts (elevators to USians) were stressed to carry 28,000lb. They were powered by two motors each capable of moving 14,000lb combining to lift the full load. The Spec set cycle times in each configuration. BUT the USN wanted to lift TWO aircraft at a time. In practice during WW2 this was rarely done, it proving quicker to avoid the time taken to carefully position both.

So to keep your carrier operating in the event one motor fails, your empty aircraft weight can't exceed 14,000lb probably a bit less, assuming you will fuel and arm them on the flight deck.

Physical dimensions
The two main Essex lifts were to be 44x48ft.

Allowing some working space around the airframe on those lifts, and the need to carry two at a time, fuselage length can't exceed about 40ft. Folded wingspan can't exceed about 22ft

When you get them to the hangar, folded height can't exceed 17ft (hangar height under the beams in an Essex was 17.5ft). Not all the space between the beams was taken up with gallery deck so as to allow unfolding an aircraft for maintenance in some parts of the hangar. That then imposes a max height during that operation of about 24ft.

Taken together those requirements place a limit on the wingspan if you opt for F4U/SB2C style wingfold.

So when you look at the various designs that is why they all come out at a max length of no more than bout 40ft or so (TBF/TBM, TBY, even the AD-1. SB2C was a bit shorter), with a wingspan of 50-57ft (TBY was the largest).

Catapult and arrester gear limits
These were BuAer supplied items for installation by the ship builders. These equipments also had weight limits. I can't immediately put my hands on the figures for the Essex class, but they will also affect aircraft design.
 

USN was already about to receive big and heavy aircraft for their carriers: F4U, SB2C, with TBF, F6F and TBU in pipeline. Something not bigger nor hevier than those designs should cut it here.
 
It also needs to apply a bit of foresight, to be capable of operating as both a torpedo bomber AND a dive bomber. So it needs a bomb bay at least 14ft long to take the Mk.13 torpedo.

The USN requirement for the SB2C to be torpedo compatible dates to late 1940 AIUI. It was tested as such from late 1942 but was not put into practice then as it took too long to switch the aircraft between roles, something which involved removal of the bomb doors.
 
The small TBU certainly has an appeal.
How about something like the Hell-bomber (tm)? A Hellcat lookalike, with a bomb bay under the level of the wings. It already has Fowler flaps so the low-speed abilities will be fine. Fuel tanks go in the wings (as much as Grumman does not like the idea ;) ). Should be a speedy attacker even with an 1-stage R-2800.
Another suggestion might be the 2-seat Corsair, with the bomb panier/bomb bay under the fusleage. Relocate the intercoolers and oil cooler under the engine a-la Hellcat if needed, so more fuel can be packed inside.
The F6 was already a crack dive-bomber right out of the box. That's where the B in VBF comes from. The way many are accustomed to thinking of these one would think they were in VF squadrons. Those were the F4Us. The F6 didn't need a second seat because it could take care of itself. The SBDs were the ones that needed to run from the carrier fighter CAP. You look at the training logs in these F6s and you'll see all the bombing runs they did. Still, instead of thinking of them as bomber-fighters, which they were, many still conceive of them as just fighters.
 
It needs to have a bomb bay of at least same size like it was the case with the new-gen attackers for the USN.
All the dive bombers carried two 500lb bombs or a single 1000lb bomb or assorted smaller. The 1600lb AP didn't show up until after Midway although it was development earlier. In time for the 1939 issue of specification?
The Torpedo bomber/s had a bigger bomb bay.
Powered by the engines that US industry can provide in good numbers,
Wright R-2600 with 1700hp, about 661 built by March 1942, many thousands later. Late war SB2Cs got 1900hp engines.
P & W R-2800 with 1850hp, about 2450 by March 1942, none after, production changed to 2000hp engines.
Range of at least 1000 miles with the full bomb bay and internal fuel,
Curtiss SB2C could just about do it, carrying 1000lbs bombs and 330 US gallons.
and 1500 with drop tanks added.
Now things get dicey. An extra 200 gallons (1200lbs) for take-off?
Obviously, fully carrier capable, even with big take off weights
See above and also see catapult capacity.
Max speed of at least 320 mph bombed-up & clean,
And now we are asking for around 10-16% more speed (give or take) over the 3 two seat dive bombers that were built.

Yes the SB2C was more than a bit of a dogs breakfast for a number of reasons.
But the chances of getting a faster airplane with a bigger bomb bay and using the same engines are pretty small.

And these are navy planes, ranges are for around 170-180mph cruising speeds.

I would also note that many of the range/endurance numbers in this chart make no sense, at least to me.
Substitute 1600lb bomb for 1000lb, use the same amount of fuel (330 gal), cruise 3mph fast and gain 450 miles worth of range ?? o_O
What am I missing?

Forget any of the R-1820/R-1830 engines, you don't have enough power to get off the deck unless you use large amounts of Jato rockets.
 
The F6 was already a crack dive-bomber right out of the box.
F6F held 250 gal internal, An SB2C carried 330 gals internal.
Ranges were close, until you start hanging bombs off the bottom of the F6F.
The fighter bombers worked at short range and worked very well. For long range?
Until the Japanese forces were degraded you need both. Or you need a squadron of F6Fs with a drop tank and one bomb each escorted by a Squadron of fighters in order to reach the target. If the fighter bombers drop bombs and defend themselves the target was not get bombed and the defending forces can claim a successful defense.

Obviously things changed from 1941-42 to 1944-45 but it wasn't just tactics/technique.
 
The Torpedo bomber/s had a bigger bomb bay.

Torpedo was supposed to be carried by SBC2 already by, at least, January 1943, so no change here.

Now things get dicey. An extra 200 gallons (1200lbs) for take-off?
And now we are asking for around 10-16% more speed (give or take) over the 3 two seat dive bombers that were built.

Well, this is sorta a challenge, as it can be expected in an what-if. If the requirenent is 300 mph, that would not represent any challenge, since it was achieved by existing aircraft.
An early SB2C with a 2000 HP R-2800 instead of 1700 HP R-2600 is already close to the speed requirement, especially with better exhausts than the SB2C had on the R-2600.

But the chances of getting a faster airplane with a bigger bomb bay and using the same engines are pretty small.

Bomb bay is the same as on the SB2C. Engines can be better, and with a better installation.
We can also note that none of the big boys attackers (TBF, SB2C, TBU, SB2A) was outfitted with Fowler flaps. Application of that device allows for a smaller wing (for lower drag) while retaining the lift capabilities.
 
Torpedo was supposed to be carried by SBC2 already by, at least, January 1943, so no change here.

Bomb bay is the same as on the SB2C. Engines can be better, and with a better installation.
No, to "fit" the torpedo into the SB2C required removing the bomb bay doors or fastening them open. tilting the torpedo so that while the tail was inside the bomb bay the nose of torpedo hung down. Speed and range takes a hit.
20411_torpedo_fitted_with_a_wooden_drag_ring_mar45.jpg

Note that the bomb bay doors end about where the landing gear goes.
We can also note that none of the big boys attackers (TBF, SB2C, TBU, SB2A) was outfitted with Fowler flaps.
Not sure you want to use Fowler flaps on a dive bomber?
The US dive bombers used perforated flaps top and bottom for dive brakes, you may not get the lift you are looking for with perforated surfaces.
Even with the torpedo planes they may not be a good idea, depends on attack profiles of the planes, It also depends on the pitch change during partial deployment and it also depends on the max speeds for deploying the flap/s in combat vs when landing. Fowler flaps also need a certain amount of space behind the rear spar and they need a certain amount of strength (weight) in the rear spar to handle the loads.

Unless you use a time machine you don't get the better cowls/exhaust in production in early 1942.

I would also note that the R-2800 with 2000hp for take off only has about 1600hp at 13,000ft vs the R-2600 B series (1700hp at T-O) having 1450hp at 12,000ft and max continuous
is 1450hp at 13,000ft vs 1350hp at 13,000ft (both engines running at 2400rpm).
Performance at altitude is not proportional to the take-off power.
 
No, to "fit" the torpedo into the SB2C required removing the bomb bay doors or fastening them open. tilting the torpedo so that while the tail was inside the bomb bay the nose of torpedo hung down. Speed and range takes a hit.
Thank you, I stand corrected.

Not sure you want to use Fowler flaps on a dive bomber?
The US dive bombers used perforated flaps top and bottom for dive brakes, you may not get the lift you are looking for with perforated surfaces.

Unless you use a time machine you don't get the better cowls/exhaust in production in early 1942.

Fowler flaps give better lift for the same wing area vs. the flaps' types these aircraft used. The wing can be smaller for same lift; a smaller wing is less draggy (for the same profile and t-c-c).
American engineers are aware of the Fowler flaps by the time Lockheed Model 14 is introduced in service, in 1937.

The Vultee Vengence have had the 'fence' type of dive brakes that were deploying both under and over the wing, a type later employed on A-36. The undercarriage can also be deployed as dive brake, if it is similar to what P-40, F4U or TBU had.
I'm okay with better exhausts became reality in late 1942 :)

I would also note that the R-2800 with 2000hp for take off only has about 1600hp at 13,000ft vs the R-2600 B series (1700hp at T-O) having 1450hp at 12,000ft and max continuous
is 1450hp at 13,000ft vs 1350hp at 13,000ft (both engines running at 2400rpm).
Performance at altitude is not proportional to the take-off power.

We gain some speed by installing the R-2800, gain some speed and range once the better exhausts are retrofitted, and we gain some speed and range via application of a smaller wing outfitted with Fowler flaps.
Granted, we can gain even more if a 2-stage engine is installed, even such a R-2600 if the 2-stage R-2800 is not available.
 

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