GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
I like the concept, though - when retracted, it conformed to the radius of the fuselage.
But agreed, when extended, it looked like something out of the adventures of Flash Gordon.
the Blenheim in battle of britian
- Thread starter steveyd
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But agreed, when extended, it looked like something out of the adventures of Flash Gordon.
Thumpalumpacus
Lieutenant Colonel
My god, that turret got a bad haircut.
Quick sketch of what I have for the Blenheim (EDIT: added a couple more):
Blenheim I - weight supposedly 10,960 lb
Blenheim IF - figure from 'The British Fighter Since 1912' re: A.G. Williams
Blenheim I - 11,776 lb (+5lb sq/in)
Blenheim IV - 14,500 lb (+5lb sq/in) - boost override (+9lb sq/in)
Blenheim IV - 13,190 lb (same aircraft)
No mention of the turret's position on any of the tests. If I was forced to make a guess I'd say it was retracted.
I suspect the two blue Mk.I lines are for +3.5 lb boost, which was the Mercury VIII without the boost override pulled. For +5 lb they'd be about 2 mph faster and 2,000 feet lower (EDIT: added in thin lines to sketch this out).
Going back on my earlier post -- judging by the lines here I suppose it's not unreasonable for a fast, light, Mk.IVF to make 292 mph.
A couple of different sources have the speed loss by adding the gun pack as about 6 mph. With the weight saved by loading the gun pack instead of the bombs, speed ends up being about the same I'd say.
Blenheim I - weight supposedly 10,960 lb
Blenheim IF - figure from 'The British Fighter Since 1912' re: A.G. Williams
Blenheim I - 11,776 lb (+5lb sq/in)
Blenheim IV - 14,500 lb (+5lb sq/in) - boost override (+9lb sq/in)
Blenheim IV - 13,190 lb (same aircraft)
No mention of the turret's position on any of the tests. If I was forced to make a guess I'd say it was retracted.
I suspect the two blue Mk.I lines are for +3.5 lb boost, which was the Mercury VIII without the boost override pulled. For +5 lb they'd be about 2 mph faster and 2,000 feet lower (EDIT: added in thin lines to sketch this out).
Going back on my earlier post -- judging by the lines here I suppose it's not unreasonable for a fast, light, Mk.IVF to make 292 mph.
A couple of different sources have the speed loss by adding the gun pack as about 6 mph. With the weight saved by loading the gun pack instead of the bombs, speed ends up being about the same I'd say.
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Shortround6
Lieutenant General
According to some sources the Mercury VIII was good for 840hp at 14,000ft (no RAM?) and 725hp for take-off on 87 octane fuel.
The Mercury XI & XII used different supercharger gear and were good for 890hp at 6000ft and 830hp for take-off on 87 octane.
The highest figures for the Mercury XV seem to be 995hp at 9,250ft and 905 for take-off on 100 octane fuel. Power may have been down to 840 at 14,000ft?
Some of the later Mercury's used the lower supercharger gear of the XI/XII or used a cropped impeller?
The Mercury 31 used in the Hamilcar glider was rated at 870hp at 4,500ft using 4.25lbs(?) or 965hp at 1000ft using 6.75lbs.
corrections, additions welcome. Lumsden is not a lot of help as the charts in the back don't show ratings with 100 octane fuel and some of the power ratings/tests in the text don't match the figures in the charts.
The Mercury XI & XII used different supercharger gear and were good for 890hp at 6000ft and 830hp for take-off on 87 octane.
The highest figures for the Mercury XV seem to be 995hp at 9,250ft and 905 for take-off on 100 octane fuel. Power may have been down to 840 at 14,000ft?
Some of the later Mercury's used the lower supercharger gear of the XI/XII or used a cropped impeller?
The Mercury 31 used in the Hamilcar glider was rated at 870hp at 4,500ft using 4.25lbs(?) or 965hp at 1000ft using 6.75lbs.
corrections, additions welcome. Lumsden is not a lot of help as the charts in the back don't show ratings with 100 octane fuel and some of the power ratings/tests in the text don't match the figures in the charts.
Shortround6
Lieutenant General
The Max speed at 15,000 may be accurate or slightly off.
The engines gave max power at 14,000ft with no RAM and Ram may have allowed the engines to make max power at 15,000. However 15,000ft is a rather "convenient altitude when you are listed speeds every 5,000ft.
Max speed may have been at 14,800 or 15,300ft????
The part about "Extra power was provided by fitting Bristol Mercury XV radial engines giving 995 hp, " Is misleading.
Yes the Mercury XV could be run at 995hp but that was 9,250ft. (again no RAM) where the air is thicker and there is more drag. Now perhaps the extra power (the Mercury VIII made less than 840hp at 9,250ft) meant that the Blenheim IV was faster at 10,000ft, it should have been. but was it faster at 10,000ft than the MK I was at 15,000ft?
The XV engine should have been good for 840hp at 14,000ft, much like Spitfires had Merlin IIIs that could give 1310hp at 9,000ft using 12lbs of boost but power fell to the normal 1030hp at 16,250 (or higher with RAM).
The engines gave max power at 14,000ft with no RAM and Ram may have allowed the engines to make max power at 15,000. However 15,000ft is a rather "convenient altitude when you are listed speeds every 5,000ft.
Max speed may have been at 14,800 or 15,300ft????
The part about "Extra power was provided by fitting Bristol Mercury XV radial engines giving 995 hp, " Is misleading.
Yes the Mercury XV could be run at 995hp but that was 9,250ft. (again no RAM) where the air is thicker and there is more drag. Now perhaps the extra power (the Mercury VIII made less than 840hp at 9,250ft) meant that the Blenheim IV was faster at 10,000ft, it should have been. but was it faster at 10,000ft than the MK I was at 15,000ft?
The XV engine should have been good for 840hp at 14,000ft, much like Spitfires had Merlin IIIs that could give 1310hp at 9,000ft using 12lbs of boost but power fell to the normal 1030hp at 16,250 (or higher with RAM).
The Blenheim's turret was powered, the retractable ventral dustbins were merely gun positions essentially the same as on a Vickers Vimy or a Gotha G IV. Bomber defensive armament changed very little between the Great War and the mid to late 30s until the advent of the power turret. The enclosed cupola had been installed in aircraft beforehand, but accuracy and aiming changed little since the Great War until the powered turret. It wasn't invented by the British but was first put into a service bomber with the RAF. This is a power-operated turret (it's actually a two-seat fighter turret fitted to a Hawker Demon) and despite its primitive appearance improved accuracy. The working gear was courtesy of Frazer-Nash (hence the FN designation but the company's name was Nash & Thompson and was a division of the Parnall Aircraft Company. Boulton Paul built the first power turret fitted to an in-service bomber).
RAFM 08
Power turrets offered greater accuracy via improved aiming and actuation of the turret. An increased rate of fire could be achieved through multiple guns, but turrets were heavy and required their own power source, whether self-contained like Boulton Paul turrets or part of the aircraft's hydraulic system, like the Nash & Thompson and Bristol turrets.
Their introduction came with problems, however, such as ingress and egress of the crewmember and keeping him comfortable and also in training. Air gunnery training prior to the power turret was universal as it had been in the Great War, shooting at banners towed by other aeroplanes, and with the introduction of turrets on RAF bombers, gunnery accuracy fell through the floor during the 30s. The C-in-C Bomber Command instigated a centralised gunnery training system for the British armed services to improve this. By the time BC was carrying out its first raids against the Germans, things hadn't improved much. It was a steep learning curve.
Power turrets offered greater accuracy via improved aiming and actuation of the turret. An increased rate of fire could be achieved through multiple guns, but turrets were heavy and required their own power source, whether self-contained like Boulton Paul turrets or part of the aircraft's hydraulic system, like the Nash & Thompson and Bristol turrets.
Their introduction came with problems, however, such as ingress and egress of the crewmember and keeping him comfortable and also in training. Air gunnery training prior to the power turret was universal as it had been in the Great War, shooting at banners towed by other aeroplanes, and with the introduction of turrets on RAF bombers, gunnery accuracy fell through the floor during the 30s. The C-in-C Bomber Command instigated a centralised gunnery training system for the British armed services to improve this. By the time BC was carrying out its first raids against the Germans, things hadn't improved much. It was a steep learning curve.
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