Bristol Blenheim vs. Dornier Do-17

[tomo pauk]

Two unsung bombers, and among the 1st night fighters. In the time of initial production they were as fast as current fighters (or faster), while by 1940/41 nobody regarded them as great asset (minor air forces had to make do), yet were used years after that.
What would be your pick?

 

[rank amateur]

Indeed unsung warriors. Both had a decent speed and a rather poor bombload. If I had to pick the better bomber I would consider the Do because of the better trackrecord. if I had to pick a nightfighter I would lean toward the Blenheim although I understand the Kauz was rather popular.

 

[Vincenzo]

data from my old thread http://www.ww2aircraft.net/forum/av...ned-bomber-outbreak-world-war-ii-11804-4.html

Bristol Blenheim IV (2 Bristol Mercury XV 920 hp, 905 hp at TO, 995 HP max for 5')
crew: 3 Wing span 17.17 m Lenght 12.98 m. Wing area 43.57 m^.
weight: empty 4441 kg max 6532 kg (load 6122 kg).
fuel: 2125 liters, oil 117 liters (can add 2 tank of 227 liters in bomb bays)
bombs: internal 454 kg, external 145 kg
weapons: 3/5 7.7 mm
Speed max 428 km/h at 3595 m.
cruise 319 km/h at optimum alt.
ceiling 8.31 km (6.7 at full load)
at 1524 m. in 3.7'
at 3048 m. in 7.2'
climb slight over 450 m./1'
range 2350 km (full internal fuel, 454 kg bombs, cruise at 272 km/h)
range 3140 km (full internal fuel no bombs)

Dornier Do 17Z-2 (2 Bramo 323P Fafnir, 1000 Hp)
crew: 4 W.S. 18 m., L. 15.8 m., W.A. 55 m^
weights: empty 5210 kg, max 8845 kg
fuel: 1550 liters, oil 204 liters (auxiliary tank in a bomb bay 896 liters)
bombs: internal 1000 kg
weapons: 4/6 7.92 mm
speed max 424 km/h at 4000
ceiling 8.15 km
at 1000 m. in 3'18''
climb 390 m./1'
range 1150 km (500 kg bombs) [probably this is not a range]
range 3000 km (max fuel not bombs)

the Do 17Z has the advantage of larger bomb bay (for true two baies, 4x250 kg vs 2x500 lbs), the Blenheim larger fuel capacity can be compensate with using a bomb bay fitted with a fuel tank. two "fast" bombers of late 30s nothing of exceptional.

 

[Juha]

Very close running thing but I'll choose Do 17Z. A bigger max bomb load, better coordination betwen pilot and AGs possible, excellent German self-sealing for fuel tanks. As a night fighter, at lest 17Z-10 had 2 20mm cannon plus 4 x 7,92mm mgs vs 5 x 7,7mm mgs (one in wing) in Blenheim fighters. Z-10 and IVF had practically same max speed, appr. 420km/h, but IVF climbed better. Z-10 could carry reasonable bomb load, if used as a night intruder. But after all Do-215 was in fact 17Z with DB 601Aa engines, and 215B-5 night fighter had max speed in order of 485km/h, different sources give different max speeds from 465km/h to 500km/h.

Juha

 

[Siegfried]

The Do 215 was an export version of the Do 17 with DB601 engines, all produced actually served with the Luftwaffe rather than being exported. It had a speed of 470kmh or 292 mph. Some variants of the Do 17 also used this engine and had the same superior speed as did the early Do 17 use DB600 engines (the DB601 added fuel injection). However as D Bender has pointed out Arguments between the RLM and Daimler Benz over factory investment funding in the mid/late 1930s left the Luftwaffe with a shortage of DB601 engines and so all DB601's went into fighters. With the Bramo 323 radial engine the Do 217Z speed was only 255mph instead of 292mph.

I think the Do 17 was significantly superior. Its armament and twin tails gave an almost all round defense and had the 292mph DB601 version been common it would have been rather difficult to intercept by Hurricanes. As the DB601 developed into the DB601N and DB601E into a 1350hp engine the speed and abillity to add armour would have kept the aircraft competitive till early 1942. The replacement of the MG15 and MG17 guns with MG81Z (twin belt fet guns) the firepower would also have kept up.

 

[Vincenzo]

Do 215 is very fast (for the time) the dauergeschwindigkeit was 488 km/h at 5000 meters (Bomber configuration 20x50 kg bombs), the Hoechsgeschwindigkeit maybe 498 km/h at 4500 meters (the number is not sure readable)

 

[Shortround6]

While the two planes are in a sense contemporaries the Do 17 is a larger aircraft. 26% more wing area, 17% heavier empty, up to 35% heavier loaded to max. It is not surprising it has more capability. I would also note that the HP figures given in the #3 post for the Blenheim are for 100 octane fuel which the majority of Blenheims did not get until 1940-41.

 

[davebender]

Bear in mind the Do-17 ended production during 1940. Total production was only about 500. The Blenheim bomber remained in production a long time. Total production about 4,400.

If nothing else we've got to give Germany credit for replacing Do-17 level bombers with He-111 level bombers. From 1941 onward the He-111 was the Blenheim bombers competition.

 

[Vincenzo]

. I would also note that the HP figures given in the #3 post for the Blenheim are for 100 octane fuel which the majority of Blenheims did not get until 1940-41.

thanks for the correction, have you the numbers with the 87 (or what else) octane fuel?

 

[Shortround6]

If nothing else we've got to give Germany credit for replacing Do-17 level bombers with He-111 level bombers. From 1941 onward the He-111 was the Blenheim bombers competition.

Not even close. The He-111 was competing with the Whitley and the Wellington.

 

[davebender]

Those also. Plus the B-17, B-24, B-25, B-26, Lancaster, Halifax and Sterling. From 1941 onward the He-111 was the backbone of Germany's level bomber force for the remainder of the war. Sometimes supplemented by Ju-88 dive bombers performing level bomber missions.

 

[Shortround6]

thanks for the correction, have you the numbers with the 87 (or what else) octane fuel?

I believe the Power is 725hp at 2650rpm and 5lbs boost for take off, 825hp at 2650rpm at 3.5lbs boost at 13,000ft for 30 minute rating and 840hp at 14,000ft at 2750rpm and 5lbs boost. Numbers are from Lumsden and seem to match with a 1938 copy of Janes all the worlds aircraft and the 1941 edition of "Aircraft engines of the world".

 

[Shortround6]

Those also. Plus the B-17, B-24, B-25, B-26, Lancaster, Halifax and Sterling. From 1941 onward the He-111 was the backbone of Germany's level bomber force for the remainder of the war. Sometimes supplemented by Ju-88 dive bombers performing level bomber missions.

Even in 1940 the He-111 was competing against the Whitley and the Wellington and not the Blenheim.

 

[Glider]

The Hampden is a better comparison for the Do17 very similar size, weight and performance

 

[Juha]

I agree with Glider.

Juha

 

[Vincenzo]

data for Hampden

Handley Page Hampden I (2 Bristol Pegasus XVIII, 1050 hp)
crew: 4 W. S. 21.08 m., L. 16.33 m., W. A. 62.06 m^
weight: empty 5344 kg, max 9525 kg
fuel: 2973 liters
bombs: internal 1814 kg
weapons: 4 7.7 mm
speed max 409 km/h at 4205 m.
cruise economical 269 km/h at 4572 m, max 349 km/h at 4572 m.
ceiling 5.79 km
at 4572 in 18' 54''
climb 299 m/1'
range 3034 km (with 907 kg bombs)
range 1762 km (full load)

 

[Glider]

I give it to the Hampden, if only for the better range/payload and it was also a useful torpedo bomber

 

[Vincenzo]

Hampden is sure a best level bomber, it like me, but take in the count that the Hampden is larger of Ju 88 (also if is lighter)