Hercules or Merlins

[Peter-RB]

I am fascinated by the old D-Day films and newsreels that are coming on the History channel just at the moment, the thing that is arousing much interest is the pictures and films of the Lancasters with Hercules Radials and some from the North African defeat of Rommels lot with Wellingtons fitted with Merlins..

My question is, was it done for a special reasons fitting Lancs with Hercs and the Wimpeys with Merlins or was it purely down to engines available to use at that time, and or A/c build, also in the lancs which engines performed better,
Ie power or ease of operations, servicing and the like, my old dad liked the Hercs but he was a little biased due to always flying with Beaufighters. when he was here this question never came into my head, now he's gone,... I need the combined knowledge of you more enlightened men who seem to be the font of all knowledge re things that fly or spin or go bang. :ok:

Peter R-B.

[LowNSlow]

I think it was done to provide an alternative supply of engines.

The Lancaster II with Hercules engines was slower than the Merlin powered I and III even though the Herc was 200 bhp up on the Merlin. Apparantly it was down to the aerodynamic disturbance caused by the Hercs having to be mounted with the nacelle above and below the wing (to maintain the thrust line?) compared to the Merlin nacelle being below the wing. I have no idea about the Wimpey!

[Jhieminga]

Quoting from Andrews and Morgan's 'Vickers Aircraft since 1908' (Putnam, 1988, p326):
In accordance with the change of official policy regarding the choice of the most powerful engines available for any class of aeroplane rather than specifying tare weight as the criterion, the design of the Wellington Mk II was begun in January 1938, with the Rolls-Royce Merlin as an alternative power plant. This action had the additional advantage of unbroken supply in the event of delay in the production of air-cooled engines.
I cannot add much more about it but hope that this may perhaps answer your question.

[Rory57]

In his book "I kept no Diary" Rod Banks, who headed the Ministry of aircraft production's Engine accessories branch, mentions the Hercules engined Lancaster as being a precaution against lack of Merlins, a situation that did not occur due to Packard building so many Merlins so succesfully.

Further he mentions the Merlin engined Halifax as suffering because the propeller thrust line was too high.

He also makes the point that the Merlin was cheaper to build than the Hercules, about half the cost! He does not refer to the installed cost, presumably radiators etc would make that cost difference smaller overall.

With ref. to the Lancaster, it must be remembered that both Merlin and Hercules engined versions came to be in the hurry caused by the Vulture engined Manchester's failiure.

The Whitley was, I seem to remember, initially powered by an Armstrong Siddeley radial, not succesfully hence the change to Merlins.

[Herod]

Yes, the Whitley had Armstrong Siddeley engines, Tigers. No 78 Squadron RAF has as its badge a "twin-tailed tiger", a reference to both the aircraft and its engines.

[reynoldsno1]

The Beaufighter II had Merlins - was pretty much a failure and not repeated on subsequent versions...

[Flash2001]

My uncle flew a tour on various marques of Halifax. He told me that the Hercules was always preferred to the Merlin.

After an excellent landing etc...

[rolling20]

IIRC, the Lancaster Mk II came about due to a perceived shortage or Merlins, due to either production issues, or enemy action.
I believe the MK II was late entering service due to the fact that the factory producing the engines was bombed! Eventually Packard Merlins became readily available ( MK III) and domestic Merlin production was never seriously threatened and the MK II was phased out. The Mk II had limitations , poor fuel consumption, lower celling and reduced bomb load, but engine wise was less vulnerable to enemy action than the water cooled Merlin.