What if America built De Havilland Mosquitoes instead of the B-17 Flying Fortress?

[wuzak]

The B-17 had two external racks (one under each wing) that could accommodate up to a 4,000 pound bomb (per rack).

Yes, but how far could they carry them? What was their performance?

B-17s did carry 2 x 4,500lb "Disney" bombs in 4 missions, the longest being to Hamburg. Did they use the external racks at other times?

 

[wuzak]

That is for sure - looking at crew numbers a B-17 carries ten and includes two pilots.
Mosquito two crew with one pilot. That means you can crew two mossies with 6 left overs from one B-17 crew. One of the B-17 crew would need to be retrained as a Navigator and that would be a problem unless they used the USAAF lead navigator idea to get them on target as then the radio operator can get them home (as often happened in real life)

There was a navigator on the B-17 crew, so that would be transferrable. Transferring to the Mosquito, he would have to be trained as a radio operator and in bomb aiming for altitude missions.

In the Mosquito, Bomb aiming at low altitude was done by the pilot.

 

[FLYBOYJ]

There was a navigator on the B-17 crew, so that would be transferrable. Transferring to the Mosquito, he would have to be trained as a radio operator and in bomb aiming for altitude missions.

In the Mosquito, Bomb aiming at low altitude was done by the pilot.

I don't see the operation of the radio a big deal, bomb aiming, another story.

 

[pbehn]

I don't see the operation of the radio a big deal, bomb aiming, another story.

The radio operator took in information concerning things that changed after the mission started. If the target was obscured by cloud and you had to switch for example then you need a new course to a secondary target.

 

[FLYBOYJ]

The radio operator took in information concerning things that changed after the mission started. If the target was obscured by cloud and you had to switch for example then you need a new course to a secondary target.

And that can be easily handled by the pilot and during flight training one of the major things learned during navigation (while in flight training) is course deviation.

 

[pbehn]

And that can be easily handled by the pilot and during flight training one of the major things learned during navigation (while in flight training) is course deviation.

Over enemy held territory, avoiding major flak and enemy airfield risks? Bill Runnels said that fighter escorts used to ask for a "fix" heading when they departed the bombers, after flying for hours over clouds where you are is a calculation and a probability, not a fact. The discussion frequently involves all that a Mosquito did. To avoid enemy A/C at high or low level Mosquitos changed direction often. Accurate bombing includes statistics from bombing by electronic aids, those are operated by the co pilot.

 

[FLYBOYJ]

Over enemy held territory, avoiding major flak and enemy airfield risks?

Yes -

Bill Runnels said that fighter escorts used to ask for a "fix" heading when they departed the bombers, after flying for hours over clouds where you are is a calculation and a probability, not a fact.

Although it is, but if you know how to "dead reckoning" (which was the standard method of navigation) you should be OK. Getting a "fix" from another aircraft is other plus as well as using LF nav aids to follow an AM frequency. Operations in the Pacific involved a lot of "DR" and sometimes pilots didn't have the luxury of a radio aid.

The discussion frequently involves all that a Mosquito did. To avoid enemy A/C at high or low level Mosquitos changed direction often. Accurate bombing includes statistics from bombing by electronic aids, those are operated by the co pilot.

Yes and agree, but many of these tasks can be done by a single pilot, and many times they were, but as stated, the additional crewman takes a lot of the workload off the pilot. Going back to the original point - aside from performing bomb aimer duties, I don't think it would take much to take the average B-17 navigator of the day and train him up to fly second crewmember in a Mosquito.

 

[MiTasol]

Yes and agree, but many of these tasks can be done by a single pilot, and many times they were, but as stated, the additional crewman takes a lot of the workload off the pilot. Going back to the original point - aside from performing bomb aimer duties, I don't think it would take much to take the average B-17 navigator of the day and train him up to fly second crewmember in a Mosquito.

I agree and the same with the bomb aimer or radio op from the B-17. Bomb aimers had at least basic nav abilities and enough technical background to learn the radios reasonably easily.
Many of the US and UK radios were identical except for what they were called. All the common SCRs had UK designations. Many were actually Brit sets made under contract in the USA.

 

[GrauGeist]

Yes, but how far could they carry them? What was their performance?

B-17s did carry 2 x 4,500lb "Disney" bombs in 4 missions, the longest being to Hamburg. Did they use the external racks at other times?

They used them on quite a few missions into France and the low countries.

I don't have any of my books available at the moment, but I posted some info on it as well as pics in another thread several years ago - I'll see if I can find those posts.

 

[GrauGeist]

Yes, but how far could they carry them? What was their performance?

B-17s did carry 2 x 4,500lb "Disney" bombs in 4 missions, the longest being to Hamburg. Did they use the external racks at other times?

Ok, found the thread.

Here's the rack mounting illustration from the armorer's guide:

Here's the post showing the racks in use:
Fake B-26 photo?

And here's another post with photos and mission details:
Fake B-26 photo?

 

[FLYBOYJ]

IIRC I think the B-17 had about a 200 mile radius with full internal bomb load and external racks (17,600 lb)

 

[wuzak]

IIRC I think the B-17 had about a 200 mile radius with full internal bomb load and external racks (17,600 lb)

What baout with only the external load of 2 x 4,000lb?

 

[GrauGeist]

The B-17 could carry six 1,600 pound bombs internally, so two 4,000lb external bombs would have had to be for a specialty mission.

The external racks were designed for 1,000, 1,600, 2,000 and 4,000 pound bombs.

If the B-17 were only carrying two 4,000 pound bombs (and no internal ordnance), it's range would have been close to an 800 mile radius.

 

[wuzak]

The B-17 could carry six 1,600 pound bombs internally, so two 4,000lb external bombs would have had to be for a specialty mission.

The external racks were designed for 1,000, 1,600, 2,000 and 4,000 pound bombs.

If the B-17 were only carrying two 4,000 pound bombs (and no internal ordnance), it's range would have been close to an 800 mile radius.

Yes, missions where bomb sizes up to 2,000lb aren't big enough.

I am not so sure about the 800 mile radius. First, the extra drag would have an effect. And second, I thought missions of 800 mile radius had no more than 5-6,000lb bombs internally?

 

[Howard Gibson]

I would agree with that but the Mosquito bombing at low altitude is far more accurate than the B-17 can ever be.

Let's be careful here. Mosquitoes flew low-altitude day bombing missions. In 1942/1943, they flew
726 day day bombing sorties, often deep into Germany. They lost 48 aircraft, for a total loss rate of a quite substantial 6.6%. The Mosquito has an excellent mission survival rate because they stopped doing this.

With a two-stage supercharger and the bulged bomb bay, a Mosquito could exceed 400mph with the 4,000lb cookie, at 30,000ft. It exceeded 400mph by more, after it dropped the 4,000lb cookie. Until very late in the way, Germans fighters could not do anywhere near 400mph at 30,000ft, so Mosquitoes were fairly safe from fighters. The 4,000lb cookie was just a big can. Was anybody developing a powerful bomb that could be dropped accurately, and mounted into a Mosquito?

The old, single stage supercharger Mosquitoes were faster than the two-stage supercharger Mosquitoes at low altitude, which is one of the reasons they kept building them. A fighter plane like a Spitfire or a Mustang requires high performance anywhere from sea level to 40,000ft. A bomber like a Mosquito, needs to be fast at its intended altitude, 30,000ft, or 1,000ft. All the other altitudes do not matter.

 

[GrauGeist]

Yes, missions where bomb sizes up to 2,000lb aren't big enough.

I am not so sure about the 800 mile radius. First, the extra drag would have an effect. And second, I thought missions of 800 mile radius had no more than 5-6,000lb bombs internally?

The B-17 was rated at 1,000 mile radius with a 6,000lb internal loadout.
Altitude, weather and such will create differences.

With only a load of two 4,000lb external bombs, the range (factoring for drag penalty) will of course be less.

 

[wuzak]

Let's be careful here. Mosquitoes flew low-altitude day bombing missions. In 1942/1943, they flew
726 day day bombing sorties, often deep into Germany. They lost 48 aircraft, for a total loss rate of a quite substantial 6.6%. The Mosquito has an excellent mission survival rate because they stopped doing this.

The day missions didn't all run at low level. About 1/3 of them were at medium/high altitude. The higher altitude missions were largely in the first few months of operations. The loss rate was trending down with more low level missions.

The big trick to reducing loss rates was to increase the number of bombers on a mission. The example I use is a similar number of B-17s were being shot down in missions over Germany in early 1944 as were used in mid-late 1943. The main difference in loss rates was that 3 to 4 times s many bombers were being sent.

It is doubtful that had double the number of Mosquitoes (1,452) been sent on the same number of missions that there would have been the double the number lost (96). More likely the number lost would be similar to the historic number.

For the same period what were the losses for B-17s operating over Germany unescorted?

 

[wuzak]

With a two-stage supercharger and the bulged bomb bay, a Mosquito could exceed 400mph with the 4,000lb cookie, at 30,000ft. It exceeded 400mph by more, after it dropped the 4,000lb cookie. Until very late in the way, Germans fighters could not do anywhere near 400mph at 30,000ft, so Mosquitoes were fairly safe from fighters.

The Mosquito Mk.IV had similar performance to the German fighters at low level.

The 4,000lb cookie was just a big can. Was anybody developing a powerful bomb that could be dropped accurately, and mounted into a Mosquito

The British developed the 4,000lb Medium Capacity bomb. This was a general purpose type bomb with a charge-to-weigh ratio of 58%. Some 25,000+ were dropped by bomber command, including a few by Mosquitoes. The 4,000lb MC was designed for use at low level, as the 4,000lb HC could break apart in such scenarios.

There was also the earlier 4,000lb GP bomb, which had a charge-to-weight ratio of 30%.

 

[MiTasol]

Let's be careful here. Mosquitoes flew low-altitude day bombing missions. In 1942/1943, they flew
726 day day bombing sorties, often deep into Germany. They lost 48 aircraft, for a total loss rate of a quite substantial 6.6%. The Mosquito has an excellent mission survival rate because they stopped doing this.

With a two-stage supercharger and the bulged bomb bay, a Mosquito could exceed 400mph with the 4,000lb cookie, at 30,000ft. It exceeded 400mph by more, after it dropped the 4,000lb cookie. Until very late in the way, Germans fighters could not do anywhere near 400mph at 30,000ft, so Mosquitoes were fairly safe from fighters. The 4,000lb cookie was just a big can. Was anybody developing a powerful bomb that could be dropped accurately, and mounted into a Mosquito?

The old, single stage supercharger Mosquitoes were faster than the two-stage supercharger Mosquitoes at low altitude, which is one of the reasons they kept building them. A fighter plane like a Spitfire or a Mustang requires high performance anywhere from sea level to 40,000ft. A bomber like a Mosquito, needs to be fast at its intended altitude, 30,000ft, or 1,000ft. All the other altitudes do not matter.

Note that I suggested transit at altitude which takes advantage of that high altitude performance then drop down purely for the bomb run to get the accuracy. Yes it will be partially vulnerable to attack from above during climb out after dropping its load but its high climb rate with no bombs and less than half fuel will minimize this.

 

[Macandy]

Considering the survivability and comparable bomb loads,would we have been far better off with the former? Would we even have built the lumbering Liberator had we had thousands of these?

What 'comparable' bomb load?

Maximum bomb load of a B-17 was 17,600lbs