Halifax & Lancaster, Radials and Merlins Question

[At Sea]

Hi,  excuse my ignorance but the Merlin engined Halifaxes were not as highly rated as the later Radial engined Mk.III versions.

However conversely the Radial engined Lancaster II was not as good as the Merlin powered versions.

 

Is this simply a case of right aircraft  / engine combination, or is it a case that the other mods made to make the Halifax III are the source of improvement and if they had been fitted with the same Merlins as the Lancaster B.III that they would have been a better aircraft?

 

Just one of those things that always puzzled me.  

 

Thanks.

[FatFlyHalf]

My best guess is that the Halifax III was regarded as significantly improved because of a combination of modifications to the fin and rudder, wings (outboard) and the adoption of powerful, air cooled, radial engines.  It wasn't just the engines that were changed.

 

However, the Halifax III still did not have the service ceiling or load carrying ability of the Lancaster I / III or X.

Edited October 8, 2017 by FatFlyHalf
spelin mistke

[Graham Boak]

The main problem with the Merlin Halifax was that the engines were mounted too high on the wing, whereas the Lancaster benefitted from later research that placed them lower giving less drag.  Early ones suffered from the draggy BP Type C turrets in the nose and dorsal positions, plus a number of excessive detail requirements.

 

The Air Ministry refused to allow HP their deeper bombbay design, although the wing strength limit would probably have prevented carrying the Grand Slam.

 

[Work In Progress]

As Graham says, plus the fact that the Merlin Lancaster benefited from significantly better-developed versions of the engine than the early Merlin Halifaxes, though the Halifax did catch up with the 20-series Merlin later, and it still didn't perform like a Lancaster.

 

However there were a lot of engine failures in service with the Halifax I / Merlin X combination, which cast something of a pall over the aeroplane alongsde its aerodynamic problems.

 

Graham's point about the shallow bomb-bay is a good one. Once the 4,000 lb 'cookie' came in, the Halifax could only carry it with partially opened bomb doors, which increased drag. didn't help.

 

All that said, though, the airframe came good with the B.III, and a late-war B.VI was a pretty good night heavy bomber by any standards. Arguably a B.VI was a better all-round piece of kit than a Lancaster II, with very similar Hercules power, providing you didn't need to carry the largest bombs for a given mission.

 

 

Edited October 9, 2017 by Work In Progress

[malpaso]

I think the Halifax also suffered from a bad reputation (as well as its real problems) because it had been around in Bomber Command's earlier efforts where methods and systems were less refined and less successful, whereas by the time the Lanc came along in numbers it was all more organised.

 

Hence even now you find comments that the Halifax was more likely to be lost on a mission than a Lanc, but the crew more likely to survive as POWs.  But as the Halifax was in service much, much earlier the figures would be skewed anyway.

 

From what I have read, as well as the draggy turrets, the aircraft itself was considerably heavier than intended even when first flown, and in service mods just made that situation worse.  Halifaxes just kept getting built to keep things going whereas BC effectively lost virtually two years of Avros actually being in service for the Manchester becoming the Lancaster.

 

Cheers

Will

[Graham Boak]

I'm not sure that the Lancaster really had any unfair preference when it came to engine deliveries.  The Mk.II had the Merlin XX, of course, but all the problems didn't go away.  The preferred Merlin 22s (Mk.II series 1a) were still mounted in the high position: there was a single Mk.II ser 2 with low-set cowlings but by then the Hercules variant was on its way.

 

I suspect that part of the problem was that the engine nacelle/cowling was based on that for the HP56's Vulture, and so may have been slightly fatter than desireable.   The ease of conversion to the fatter Hercules may be relevant here.  Apparently there was a unwanted flow problem from the wing/cowling intersection, which leads me to suspect a link to the rudder locking problem but I don't think that it has ever been discussed or even linked in print.   This is possibly also linked to the vibration problem which was cured by the 4-blade prop - had that been more widely available earlier there may have been less failures.  There is an interesting book from the RR Historical Trust entitled "RR and the Halifax", which is spoilt by an insistence that the problems were all due to HP not going with the RR "power egg" approach.  Methinks that the original Halifax cowling/Gallay cooling system was designed before the RR "power egg"/Morris block radiators were actually available.  (Plus they didn't do all that much to the Beaufighter or Mosquito either...  but that's getting into different stories.)

 

The shallow bombbay was not unique to the Halifax of course, but was common to other RAF bombers of the design period (Hampden, Wellington, Stirling) and stemmed from the prewar weapon requirements.  The largest store required was the long 2000lb SAP bomb, which had the same diameter as the smaller bombs.  The reason for the deeper Avro bombbay appears to stem from the requirement that the Manchester also had to be a torpedo bomber: something that HP requested be removed for the HP56 and hence the Halifax. 

 

Malpaso has posted whilst I was typing.  I disagree that BC lost any significant time: the success of the Lancaster was partly due to the advances in technology in the years between the designs.  Notably the low-mounted engines, and the Morris block radiators.  The slightly bigger span wing didn't hurt, either.   Had Avro gone straight to a 4-Merlin design it would have been a less impressive machine than the eventual Lancaster - and suffered all the aerodynamic development problems of the Manchester itself.

Edited October 9, 2017 by Graham Boak

[Work In Progress]

Nothing 'unfair' about the Lancaster having better Merlins than the Halifax I,  it was simply due to timing. There was a lot of improvement of the Merlin between the first production Halifaxes rolling off the line in October 1940, only a couple of months behindthe Manchester, and the start of Lancaster production in October 1941.

 

My point about the Merlin XX being better than the X was not particularly made with regard to outright performance (I agree the nature of the installation was more influential in that regard than minor variances in installed hp), but also with regard to the improved reliability of the 20-series.

Edited October 9, 2017 by Work In Progress

[sloegin57]

30 minutes ago, Graham Boak said:

Apparently there was a unwanted flow problem from the wing/cowling intersection, which leads me to suspect a link to the rudder locking problem but I don't think that it has ever been discussed or even linked in print.   

There was an attempt to cure this by the introduction of a small half conical fairing between the outboard side of the inboard engine and the leading edge of the mainplane.  It appears to have had little effect.

 

Dennis

[Graham Boak]

In 1944 Coastal Command were calling for the replacement of their Mk.XXs by Mk.22s because of poor reliability.  Of course, by then some of their Mk.XXs could have been rebuilds and hence decidedly old.    However, beyond this (perhaps special) case the problems with the Merlin in the Halifax weren't restricted to the handful with the Mk.X.  I'll have to resort to my references for the details, but as I recall the Merlins were having to be overworked to maintain the desired cruise speed and altitude, and so range was adversely affected.  This could have been due to high drag or higher weights, but once the unwanted excrescences and role-equipment were removed I don't think that the Halifax was particularly overweight.  (We're not talking about the Stirling here...)

[malpaso]

Graham,

My point about the lost two years of Avros was the gap between when the Manchester should have been ramping up in service (1941 = at which point they knocked it on the head) to when the Lancaster really arrived in numbers in 1943.  During that period the Halifax was available and had to take the burden (with the Stirling, Wellington and an ever-diminishing handful of Manchesters) of BC effort.  But as you say, those two years of design (say 1940-42) were when real improvements were made to airframes and engines in the light of experience and expanding knowledge, to some extent across most combatant nations.

Cheers

Will

 

[Work In Progress]

It's hard to be sure that one is comparing like-for-like, but for what it's worth, published empty weights for a Halifax B.III seem very similar to those published for contemporary Lancasters. Of course the lower aerodynamic efficiency is likely to mean you end up loading more fuel for a given trip, so more weight from that source.

[nuuumannn]

The early Halis had numerous faults, not just the engine installation or excessive drag, perhaps the most serious being excessive rudder over balance, which was dealt with in the D shaped rudders installed on Mk.Vs - before fitted to the III, which was, as was often the case during the war, originally intended as an interim until the arrival of the Hali IV. A good book that examines the engine installation issues is Rolls-Royce and the Halifax by David Birch, published by the Rolls-Royce Heritage Trust. It goes into considerable detail.

[At Sea]

Great replies, thanks guys!

[PeterMG]

Finding out the issues with the Halifax has been quite difficult, and direct comparisons with the Lancaster few and far between.  But the Halifax I and II with Merlin's had the engines mounted too high on the wing which caused aerodynamic issues as well as big issues with the exhaust, and probably the biggest issue.  Basically ejector exhausts pointed directly at the wing leading edge.  Therefore some form of manifold to direct exhaust flow away was required, which in turn glowed cherry red and could be easily seen at night from some distance.  Every effort to make the exhaust less visible resulted in an increase in drag. The situation was never resolved satisfactorily. 

 

Now all of this would not have been a huge problem if the aircraft did not have so much inherent drag. Even when all the modifications where applied, with streamlined nose, revised tail-plane and fins, and extended wingtips, the Halifax needed considerably more boost to cruise, and this was its achilles heel.  Prior to the modifications full throttle (max continuous) was often needed just to cruise 2 or 3 knots above the stall.  Bomb load had to be traded for fuel and often bombs were jettisoned to make the target.  The engines were never going to last long when pushed so hard. (150 hours if lucky and water leaks didn't occur) And the fact that the Halifax had such a poor margin between its cruising speed and the stall led to much of the handling issues and unrecoverable spins. 

 

Perhaps this comparison will help to demonstrate the point.  Both aircraft at 60,000lbs

 

Lancaster      18,000 feet   speed 175 indicated     2300 rpm  +3 boost

Halifax          18,000                   168                  2950         +8

Halifax          18,000                   128                  2660         +51/4

 

Full supercharger was impossible to use when the Halifax was above 16,000 feet.  A Merlin series 60 version was built and tested, HR756, which was some 40 mph faster than the Hercules powered MkIII. My impression of the story of the Halifax, is of a manufacturer not very interested in anything other than getting bombers out the door.  In retrospect they produced far to many marginal aircraft that were more of a danger to their crews than the enemy. 

 

[Aeronut]

This is an interesting discussion and it got me delving into my archive for another Lancaster / Halifax comparison.

The Halifax is well known as a glider tug aircraft, less well known is the fact that the Lancaster was also tested as a glider tug.

The table below takes its information from two AFEE reports  AFEE/T1 Halifax II as tug for Hamilcar and AFEE/T11 Part 2 Lancaster R5606 as tug for Hamilcar. I've chosen test points as close as possible for the best comparison. The conclusion of the reports was that the Lancaster was the better tug, but as it was also the better bomber the role of glider tug was destined to be one its not remembered for.

 

    TUG                   Glider                Altitude            RPM            Mixture              Boost                    Airspeed

Lancaster I         Hamilcar             9000 ft             2650             Rich                    +5                         149 TAS

  46000 lb            36000 lb

 

Halifax II             Hamilcar              8700 ft             2850            Rich                   +8.9                       149 TAS

45000 lb              34500 lb

                         (undercarriage

                           jettisoned)

[Peter Lloyd]

On 10/17/2017 at 9:06 AM, PeterMG said:

 My impression of the story of the Halifax, is of a manufacturer not very interested in anything other than getting bombers out the door.  In retrospect they produced far to many marginal aircraft that were more of a danger to their crews than the enemy. 

 

This seems to have been Harris's view as well.  Beaverbrook set up contracts as Minister of Aircraft Production that had this weakness: the incentives were all for airframes-out-the-door, as befitted the situation in August 1940.  Harris spent a lot of time writing spiteful memos about Handley-Page, including a memorable one where he suggested Stalin would have dealt with them more appropriately.  There were certainly lots of quality control issues that added to drag, and which were addressed by the Mk III.  A good source on this is a book called The Relentless Offensive.

[Brian]

There was also a statistic showing, on average, more crewmen got out of the Halifax than the Lancaster in the event of a shootdown

[Michael51]

18 hours ago, Peter Lloyd said:

This seems to have been Harris's view as well.  Beaverbrook set up contracts as Minister of Aircraft Production that had this weakness: the incentives were all for airframes-out-the-door, as befitted the situation in August 1940.  Harris spent a lot of time writing spiteful memos about Handley-Page, including a memorable one where he suggested Stalin would have dealt with them more appropriately.  There were certainly lots of quality control issues that added to drag, and which were addressed by the Mk III.  A good source on this is a book called The Relentless Offensive.

Thanks for the source: always so helpful.

 

I have just purchased that book.

 

Michael

Edited October 26, 2017 by Michael Enright