Fast bombers alternatives for 1939-40

[Shortround6]

I am on a tablet and have not figured out how to cup and paste but a Google search for "He 111 dropping bombs" should bring up a video.
The bombs flip 180 degrees pretty quick but they may not being going in exactly the same direction. The framing of the shot is fairly tight and bombs aren't stabilized yet as they exit the shot.

 

[don4331]

I think the thick wings were part of the problem with the Typhoon.

The Henley had some promise though, granted. And nowhere near the problems of the Typhoon that I'm aware of.

Another (to me) promising option would be the little Miles M.20

Miles M.20 - Wikipedia

en.wikipedia.org

330 mph with fixed undercarriage is pretty impressive to me. Very good rate of climb too. It had the 8 gun armament. Also had an 870 mile range and 5 hour endurance on internal fuel (granted, going very slow I'm sure).

What about a four gun M.20 with a bomb cradle underneath?

The Miles M.20 has a 20% thick wing at root; same as the Henley...

We will note the 350mph speed was for a clean prototype and it dropped to 330 when "combat equipment" was installed.

While still impressive, I think the Henley would prove to be superior for a production, in service aircraft.

 

[bf109xxl]

That would make for a very neat install - but weren't the vertical cells in the early HE111s a bit of a handicap for accurate bombing?

The Soviets tested both early and late versions of the 111 with Soviet bombs and never complained about any problems with bombing accuracy when dropping from internal bomb bays.

 

[SplitRz]

The Soviets tested both early and late versions of the 111 with Soviet bombs and never complained about any problems with bombing accuracy when dropping from internal bomb bays.

I'm not so sure about that. I'm sure I've read that the issue was that the bombs were unstable as they entered the slip-stream and wobbled/tumbled about and took time to stabilise - and that hampered accuracy as they didn't drop in a neat 'stick'. That may be because the German bombs were mounted tail first inside the HE111. Not much an issue for mid to high level carpet bombing, but surely one for high speed and low level release?

I'll dig around when I have time to try and find a source - but here's an illustration - through dramatized, these are real 111's

Wobbly bombs!

 

[Howard Gibson]

I think the thick wings were part of the problem with the Typhoon.

The Henley had some promise though, granted. And nowhere near the problems of the Typhoon that I'm aware of.

Another (to me) promising option would be the little Miles M.20

Miles M.20 - Wikipedia

en.wikipedia.org

330 mph with fixed undercarriage is pretty impressive to me. Very good rate of climb too. It had the 8 gun armament. Also had an 870 mile range and 5 hour endurance on internal fuel (granted, going very slow I'm sure).

What about a four gun M.20 with a bomb cradle underneath?

Watch out for Hurricane top speeds. The Miles M.20 with a Merlin_XX was faster than a Battle of Britain Hurricane. When Hurricanes were equipped with Merlin_XXs, the top speeds were about the same. Eric Brown was not impressed by the M.20's handling. Was it an improvement over the Hurricane?

Someone has brought up the presence of armament. Be careful when looking at the performance of prototypes.

 

[SplitRz]

I am on a tablet and have not figured out how to cup and paste but a Google search for "He 111 dropping bombs" should bring up a video.
The bombs flip 180 degrees pretty quick but they may not being going in exactly the same direction. The framing of the shot is fairly tight and bombs aren't stabilized yet as they exit the shot.

Yup! Its my contention that increased airspeed and low altitude and the bombs not describing a predictable ballistic parabola would definitely impact accuracy. Maybe our aircraft doesn't need that level of accuracy if tossing out frags or napalm, but if its looking for pinpoint targets like a ship or a Gestapo headquarters, I'm not sure its going to cut it.

 

[Howard Gibson]

I'm not so sure about that. I'm sure I've read that the issue was that the bombs were unstable as they entered the slip-stream and wobbled/tumbled about and took time to stabilise - and that hampered accuracy as they didn't drop in a neat 'stick'. That may be because the German bombs were mounted tail first inside the HE111. Not much an issue for mid to high level carpet bombing, but surely one for high speed and low level release?

I'll dig around when I have time to try and find a source - but here's an illustration - through dramatized, these are real 111's

Wobbly bombs!

A number of British bombers, including the mosquito, had Bombay doors held closed by bungee cords. The doors were forced open by the weight of the bombs. Is that any better?

If you drop a bomb while you are installing on an He111, do you want it to land on its nose?

 

[bf109xxl]

I'm not so sure about that. I'm sure I've read that the issue was that the bombs were unstable as they entered the slip-stream and wobbled/tumbled about and took time to stabilise - and that hampered accuracy as they didn't drop in a neat 'stick'.

The speed of the 111 was low enough that these effects were not significant.

That may be because the German bombs were mounted tail first inside the HE111. Not much an issue for mid to high level carpet bombing, but surely one for high speed and low level release?

Well, the term "high speed" is hardly applicable to the 111. And I suppose it rarely had to bomb from low altitudes.

I'll dig around when I have time to try and find a source - but here's an illustration - through dramatized, these are real 111's

The Soviets paid considerable attention to the aerodynamics of bombs and bomb bays - for example, on the Tu-2, they ensured reliable release of large-caliber bombs from the internal bay without additional mechanisms during dive bombing. Therefore, I am almost certain that if they had discovered any problems with the accuracy of bomb dropping on the 111, they would have reflected them in their reports. But I have not yet come across any mention of such problems.

 

[SplitRz]

A number of British bombers, including the mosquito, had Bombay doors held closed by bungee cords. The doors were forced open by the weight of the bombs. Is that any better?

No.

The Blenheim had bungee cords on the bomb doors - and they were a known and widely acknowledged source of inaccuracy.

Like most contemporary aircraft, the Blenheim's bomb bay doors were secured closed by bungee cords - relying on the weight of its 1000lb bomb load to force the doors apart when they were released. With no way of knowing how long it would take the bombs to force the doors open, bombing accuracy was extremely poor.

It was reflected in the design of the Mosquito - which did not use bungee cords. Have a look here inside a Mosquito bomb-bay: actuated doors:

If you drop a bomb while you are installing on an He111, do you want it to land on its nose?

Provided its was connected and disarmed/armed correctly, whilst dropping a bomb during loading was going to be dangerous regardless, it would make almost literally no difference.

The fuse of a bomb was not usually in the nose like a kids toy pistol percussion cap - but operated by a firing pin within the nose, body or tail of the bomb which was only unlocked after the bombs arming prop had rotated a set number of revolutions within the airstream.

 

[SplitRz]

The speed of the 111 was low enough that these effects were not significant.

I know. But we're talking on a thread about a hypothetical high-speed bomber, aren't we? Hence my point about the questionable logic of using vertical bombs cells.

 

[Steamed_Banana]

Watch out for Hurricane top speeds. The Miles M.20 with a Merlin_XX was faster than a Battle of Britain Hurricane. When Hurricanes were equipped with Merlin_XXs, the top speeds were about the same.

yeah but the M.20 had fixed undercarriage! I think if you put in retractable undercarriage you'd get another significant speed improvement.

Eric Brown was not impressed by the M.20's handling. Was it an improvement over the Hurricane?

Someone has brought up the presence of armament. Be careful when looking at the performance of prototypes.

If speed was say, 20 mph faster, altitude performance and climb were similar, and range was a bit better, then I think it would be worth pursuing, though the smaller wings make it a bit less maneuverable in terms of turn rate, it may well have had a better roll rate which could compensate for that.

 

[tomo pauk]

IMO - the supposed 350 mph turn of speed looks more like a figure from the sales brochure, than a real number. We can recall that the P-40F, with a tad better engine, a much thinner wing and with the retractable U/C was making about 360 mph. Or, the D4Y doing 360 mph with more HP, again the thinner wing and the retractable U/C. Even 330 mph seems fairly optimistic.

If the fixed U/C is all good and well, a fixed-gear Spitfire with the Merlin III would've probably do 330 mph. Play a bit with the cooling system (relocate all of it in the beard position) so the bomb is not fully exposed in the slipstream and a second cockpit can be had, and as a bombed-up aircraft it should've been doing a bit over 300 mph? Note that Merlin III was a reality 3 years before the Merlin XX.

 

[SplitRz]

If speed was say, 20 mph faster, altitude performance and climb were similar, and range was a bit better, then I think it would be worth pursuing, though the smaller wings make it a bit less maneuverable in terms of turn rate, it may well have had a better roll rate which could compensate for that.

Smaller wings and wing area also have a large bearing on load carrying capacity in the form of wing-loading (and its effect on take off distance, stall speed etc) so other aspects to consider too if this bird is going to be carrying more than a couple of 250lb bombs... Was the M.20 flapped?

 

[tomo pauk]

Bf 109E was carrying a 250 kg /550 lb bomb, despite it's small wing.
About the M.20 - there is ample space for the undercarriage to be retractable there.

 

[GrauGeist]

If you're going to go to the trouble of rebuilding the Miles M.20, why not save time and just go with Boulton-Paul's P.94 instead?

 

[Steamed_Banana]

If you're going to go to the trouble of rebuilding the Miles M.20, why not save time and just go with Boulton-Paul's P.94 instead?

Only real thing wrong with the Defiant that I can see was in fact the turret. I mean the wing is pretty wide but that could be 'clipped'

 

[GrauGeist]

Only real thing wrong with the Defiant that I can see was in fact the turret. I mean the wing is pretty wide but that could be 'clipped'

The BP P.94 was the turretless version of the Defiant.

 

[yulzari]

Are we perhaps veering off towards a fighter bomber? That was the way things were going IOTL.

For a true high speed bomber we need to have a concept of what constitutes a minimum bomber range and bomb load. You can sling 1,000, 1,500 or even 2,000lb of bombs under a Kittyhawk but you are not going to carry that across from the UK to Germany and back. You can carry an 1,800kg bomb under a Junker JU87 but it can barely stagger from the Pas de Calais to London and back.

What constitutes 'high speed'? A Savoia SM79 was a high speed bomber at 290mph flat out when you are trying to intercept it with a Gloster Gladiator MkII over Albania in 1941. Rather less of a high speed bomber when intercepted by a Supermarine Spitfire MkVIII in 1944.

If we look at OTL 1,000lb was a medium bomber bombload early in the war and 350mph more of an aspiration than reality. The original Mosquito was barely more than 20mph faster than a period Spitfire.

 

[Shortround6]

to expand on a few things.

For a true high speed bomber we need to have a concept of what constitutes a minimum bomber range and bomb load. You can sling 1,000, 1,500 or even 2,000lb of bombs under a Kittyhawk but you are not going to carry that across from the UK to Germany and back

Heck, you are not going to get a Kittihawk from Norwich to Amsterdam with 1000lbs of bombs and get back. Operational radius is much shorter than "book" ranges because formation flights require more throttle jockeying to maintain formation. Also endurance/range is dependent on the endurance of the first plane in the formations take-off time, how long it circles while later planes take-off and form up.

If we look at OTL 1,000lb was a medium bomber bombload early in the war and 350mph more of an aspiration than reality. The original Mosquito was barely more than 20mph faster than a period Spitfire.

Yes, this shows the problem.

Let's take the Spitfire and turn it into a high speed bomber, ala the Henley.
Slightly enlarge the tail (a small bit of drag)
lengthen the fuselage by about 4 ft to hold the rear seater (a little more drag)
Build stub wing to mount the existing wings to. Need more wing area for take-off but more drag
Build bomb bay of just two 250lbs or for two 500lbs bombs? 250lb bomb is 10.3in in diameter and the 500lb is 13in in diameter. Or a single 500lbs bomb with two 250lbs option? Henley did not have the single 500lb option. You do need clearance for for the racks and for the armorers to work so bomb bay is going to add more than 10.3 to 13 in the the height of the fuselage. More drag.

You can take 6 guns out of the wings (or 7?) to save weight and a bit of drag (all those slots in the bottom of the wing) but you may want to use the inner gun bay/s for fuel tanks.

You can cheat and use the Merlin X engine instead of the Merlin II in the Henley but the main difference between the II and III was the propeller shaft to suit different propellers.
We can also use hindsight and figure that a tactical bomber needs good speed at 1500-5000ft and not 15-17,000ft and using low gear in the Merlin X (or just use a Merlin VIII engine) will give us better performance at low altitude.
Having an engine that gives over 1000hp at sea level instead of 880hp may mean we can use a smaller wing and still get out of the airfield.
But let's recap, Henley lost over 20mph (maybe as much as 30mph) compared to a Hurricane I.
Actual range is certainly up for dispute. Henley got about double the range of a Hurricane I using the same amount of fuel?
A single engine bomber is certainly cheaper than a twin. It may not be a good purchase, unless the goal is fill up squadrons with numbers.

 

[tomo pauk]

Let's take the Spitfire and turn it into a high speed bomber, ala the Henley.

Agreed 200%.

Slightly enlarge the tail (a small bit of drag)
lengthen the fuselage by about 4 ft to hold the rear seater (a little more drag)
Build stub wing to mount the existing wings to. Need more wing area for take-off but more drag

Good points.
The stub wing might house a 250 lb bomb on each side, internally?

Build bomb bay of just two 250lbs or for two 500lbs bombs? 250lb bomb is 10.3in in diameter and the 500lb is 13in in diameter. Or a single 500lbs bomb with two 250lbs option? Henley did not have the single 500lb option. You do need clearance for for the racks and for the armorers to work so bomb bay is going to add more than 10.3 to 13 in the the height of the fuselage. More drag.

Two 500 lb bombs will not fit, unless the bomb bay is (very?) long.
Deeper fuselage can be preceded with the beard radiator, so the drag penalty is not paid twice (1st for the deeper fuselage, 2nd time for the cooling drag). Beard radiator also counter-balances the now heavier aft half of the A/C, and leaves more volume in the wings.

But let's recap, Henley lost over 20mph (maybe as much as 30mph) compared to a Hurricane I.
Actual range is certainly up for dispute. Henley got about double the range of a Hurricane I using the same amount of fuel?

Seems like the loss was 20 mph.
Henley not just used the more voluminous wing than the Hurricane, but there were no guns or ammo there, so it probably carried much greater tankage.

A 'fat Spitfire' that looses 25 mph vs. the Spitfire I will still get 330 mph.

(for the Germans, a 'fat 109' would've been interesting)