Blenheim engines

The “Big Bristols” tee-shirt is still a popular line – available through the Blenheim Society, helping keep the world’s only airworthy Blenheim in the air!

I had a couple at the time Steve, long forgotten by many.

Trolley Aux

I will remember for a long time seeing the Lead for the Blenheim Society (Betty George) wearing her “Happiness is a big pair of Bristols” T shirt, complete with head on view of a Blenheim image.

Indeed, although this was also driven by the deeper fuselage of the maritime attack Beaufort, so that the pilot sat higher, whereas the Blenheim pilot sat low in the fuselage to reduce drag. By the time the Beaufort was being designed it was understood that the lower the engine on the wing, the lower the drag. Something that was too late for the Halifax but in time for the Lancaster.

There are three aspects to this.
Firstly, Bristol will not have considered fitting anything other than Bristol engines to the Blenheim. So the next engine up is the Taurus, which does indeed have a smaller diameter.

The slightly later Beaufort had ‘underslung’ Taurus engines, so maybe they did address the issue?

I think what has been forgot to be mentioned is

They are BIG BRISTOLS !!!

Coat, Hat, Exit stage left,,,,,,,,

The Blenheim has an excellent all round view especially to the rear…from the Air Gunner/Radio Operator’s position.

Anne

And since the Merlins were less powerful, it made the single engined performance marginal IIRC. However, the ‘power eggs’ designed for the Beaufighter II were adapted for the Lancaster I think?

It is interesting all this talk of power
When then blenheim was on the drawing board the most powerful engine available was an engine designed in the 1920’s, it was the first radial engine to achieve one horsepower per one pound weight,it was fuel efficient and was producing more power than the merlin. So Bristols in their wisdom used the best aero engine for the job THE BRISTOL MERCURY.

The Blenheim pilots view is more than acceptable but the navigator is restricted in the mk.1 hence the elongation in the later versions

There are three aspects to this.
…
Thirdly, from the point of pilot’s view, the Mercury may be taller but it is shorter. Just which aspect of the pilot’s view is the more important?

Also, the role of the aircraft meant that all-round visibility wasn’t as important as it would have been on a fighter. Even on more modern twins with significantly smaller engines the view to the side can be severely restricted. It’s something you learn to live with as a pilot.

Bristol did fit the Merlin to the Beaufighter but only, I believe, when there was some doubt about the supply of Bristol Hercules engines being adequate to meet wartime demand.

And since the Merlins were less powerful, it made the single engined performance marginal IIRC. However, the ‘power eggs’ designed for the Beaufighter II were adapted for the Lancaster I think?

Bristol did fit the Merlin to the Beaufighter but only, I believe, when there was some doubt about the supply of Bristol Hercules engines being adequate to meet wartime demand.

There are three aspects to this.
Firstly, Bristol will not have considered fitting anything other than Bristol engines to the Blenheim. So the next engine up is the Taurus, which does indeed have a smaller diameter.
Secondly, as pointed out above, you can’t just drop such a significantly different and more powerful engine into a design. More power = bigger prop = wider centre-section, and so on. Even a Taurus would have required significant rework and restressing, potentially leading to a new aircraft.
Thirdly, from the point of pilot’s view, the Mercury may be taller but it is shorter. Just which aspect of the pilot’s view is the more important?

The Merlin engines would be heavier and longer (although more powerful) and this would push the centre-of-gravity forward surely? Then there would be the cooling to consider; where would the radiators go, under the wings or a ‘chin’ installation like the Lancaster?

Overall I think the Merlin would be too big for the Blenheim: (even without a radiator) it is at least half as heavy again as the Bristol Mercury and nearly twice as long, and most of the weight in a Mercury is further back, in line with the cylinders.

No, I wouldn’t call the Merlin a ‘smaller’ engine at all!

The longer nose was to just to provide room for a navigator/bomb aimer station, the pilot seat remained in the same place as the Mk1. The view does appear to be compromised by the engines but I have never seen it criticized so it might look worse than it really is.

Richard

I think that is why they put the longer nose on it. but I am sure some more knowledgeable will be along soon.