MOST UNDERRATED AIRCRAFT OF WWII?

[wuzak]

That last was using information from Tony Buttler, British Experimental Combat Aircraft of World War II.

On 12 September 1942, the aircraft made its 10th flight. Captain Baker had just taken off when the engine seized, a result of a sleeve drive crank failure. Low to the ground and without any options, Captain Baker put the MB3 down in one of the many small fields lined with hedgerows and other obstacles surrounding RAF Wing. The aircraft clipped a pile of straw and crashed through a hedgerow at high speed. The MB3 cartwheeled, broke apart, and caught fire. Captain Baker was killed instantly.

Martin-Baker MB3 Fighter

This also lists Buttler as a source.

 

[swampyankee]

It may well have had greater greater volumetric efficiency in general or especially over certain examples. However poppet valve engines have considerable variation in volumetric efficiency so unless we know what is being compared such a statement doesn't mean much.
That is to say that perhaps a sleeve valve cylinder shows a 2% increase over poppet cylinder A and a 10% improvement over poppet cylinder B.
Obviously the advantage over Cylinder B is substantial and even the difference between the sleeve valve and the average of the poppet valves is a noticeable one. However if the difference gets down to 2-3 % while the statement is still accurate does the cost/complication of the sleeve valve justify the development of engines using it?

Well, nobody outside of the UK put sleeve-valve aircraft engines into service, so I'd say most engineers of the era would say "no." Sleeve valves have some advantages, and at least as many disadvantages.

 

[Juha2]

Juha, do you have a 'root cause analysis' which sheets home fault to the Sabre engine,
- in the case of Capt Bakers' fatal crash?..

I don't have any specific source now in hand, IIRC I have somewhere one article on the MB fighter series, but cannot remember where. I have some books on engines but IIRC none have detailed describtion on the MB 3 crash. Besides what is in Buttler's book quotes above Bowyer writes in his Interceptor Fighters for the Royal Air Force 1935-45 that during the maiden flight of the MB 3 the Galley radiator was found to be unsuitable. But Baker was not too worried and Napier representatives agreed, stating that there was no danger in a further flight. But during the second flight again coolant became excessively hot and the plane was grounded. Some mods were made in radiator but the plane crashed duringits 10th flight and Baker was killed. Bowyer notes that engine overheating had not been solved.

As for the dismal H-P Hereford - as I recall, the engine development writer LJK Setright likened
the use of the Dagger, ( which was intended for a fighter, such as the MB 2) in a medium bomber,
as akin to putting a Formula 1 racecar engine in a bus, & then expecting it - to do well at the task..

On Dagger Bowyer writes that attemps were made to persuade Supermarine to fit a 24-cyl Napier Dagger in their latest design, Type 300, but Supermarine strongly resisted. At least Supermarine trusted more on RR than Napier. IIRC in all books I have read Dagger suffered from reliability and maintenance problems. And Merlin worked well on fighters and bombers as did most of engines, Bristol Hercules, DB 60x series, BMW 801,R-1820, R-1830, R-2800, Jumo 213 etc. IIRC only on CC AW Whitley GR types there were significant troubles with early Merlins. So if Setright is correct, Dagger was fairly unique engine during late 30s early 40s, suited only for one type of aircraft.

 

[Shortround6]

From Wiki so..........
Napier-Halford Dagger I

1934 – 650 hp.

Dagger II
1938 – 755 hp

Dagger IIIM
1938 – 725 hp

Dagger VIII
1938 – 1000 hp, intermediate altitude supercharger, initially known as E.10

Now please note the Dagger is down on power compared to the Merlin at any given time. In 1930 the Dagger is making 1000hp at 8,750ft while the Merlin is making 1030hp at 16,250ft. The Dagger at 15,000ft is comparable to the Peregrine only it weighs over 280lbs more which pretty much cancels out the radiator on the Peregrine and we all know what happened to the Peregrine.

 

[Glider]

My latest option for the most underrated aircraft of WW2 would be the Beaufighter. It was a success in all its roles in all the theaters it operated in, had a number of important firsts and is overshadowed by the Mosquito. The Mossie was a better aircraft but the Beaufighter deserves some time in the limelight and not being stuck in the shadows

 

[tomo pauk]

...
On Dagger Bowyer writes that attemps were made to persuade Supermarine to fit a 24-cyl Napier Dagger in their latest design, Type 300, but Supermarine strongly resisted. At least Supermarine trusted more on RR than Napier. IIRC in all books I have read Dagger suffered from reliability and maintenance problems. And Merlin worked well on fighters and bombers as did most of engines, Bristol Hercules, DB 60x series, BMW 801,R-1820, R-1830, R-2800, Jumo 213 etc. IIRC only on CC AW Whitley GR types there were significant troubles with early Merlins. So if Setright is correct, Dagger was fairly unique engine during late 30s early 40s, suited only for one type of aircraft.

There was probably other reason than Supermarine having more faith in Merin/RR than in Dagger/napier - Merlin III was making more than 50% more power at 16300 ft than Dagger. Even the Kestrel of late 1930s was making more power at altitude than Dagger.

 

[Juha2]

Hello SR6 & Tomo
yes but IMHO it also shows that if Dagger was an engine especially designed for fighters, it wasn't so impressive, being heavy for its power and with an indifferent supercharger.

 

[J.A.W.]

Doubtless the rapidly advancing airframe tech ( & size/mass) during the `30s meant that the time had
come for larger more powerful engines. The Dagger had been left behind by this, & Napier acknowledged it,
hence Halford & Tryon commenced work on the Sabre, as a result.

Napier had flown the 1st '1000hp' engine in the `20s, ('Cub') before airframes were able to cope with it.

The sad outcome for Capt Baker was one of the reasons the Air Min prefered such advanced work
to be the province of established makers, who were likely to have a broader outlook design-wise,
esp' for fundamentals such as cooling capacity & in MB's case - fin area/control authority.

As for engines in tanks, many much more bulky aero-engines were fitted to them, even radials!
Liberty engines were 'powering' British 'cruiser' tanks, a large Christie design, ( cousin to the T-34),
so I'd doubt that space considerations would be a significant factor, ( a Merlin would/did fit).

 

[J.A.W.]

Well, nobody outside of the UK put sleeve-valve aircraft engines into service, so I'd say most engineers of the era would say "no." Sleeve valves have some advantages, and at least as many disadvantages.

Much more to it than that.

Getting a new application working well is a big effort, so makers such as P & W & R-R, who certainly knew
that sleeve valve advantages were real, having tested their mettle, in metal - made a commercial
decision to stay with developments of their established, if old-fashioned designs - for mass-production.

Roy Fedden & Frank Halford both had experience with DOHC 4V poppet valve cyl heads,
& both well knew that sleeve valves had real advantages over them, let alone pushrod 2V cyl heads.

 

[pbehn]

From what I read the problem wasn't so much of the design of the Sabre but of mass producing it.

 

[wuzak]

Much more to it than that.

Getting a new application working well is a big effort, so makers such as P & W & R-R, who certainly knew
that sleeve valve advantages were real, having tested their mettle, in metal - made a commercial
decision to stay with developments of their established, if old-fashioned designs - for mass-production.

Roy Fedden & Frank Halford both had experience with DOHC 4V poppet valve cyl heads,
& both well knew that sleeve valves had real advantages over them, let alone pushrod 2V cyl heads.

Still don't like auto-wrap?

 

[swampyankee]

Much more to it than that.

Getting a new application working well is a big effort, so makers such as P & W & R-R, who certainly knew
that sleeve valve advantages were real, having tested their mettle, in metal - made a commercial
decision to stay with developments of their established, if old-fashioned designs - for mass-production.

Roy Fedden & Frank Halford both had experience with DOHC 4V poppet valve cyl heads,
& both well knew that sleeve valves had real advantages over them, let alone pushrod 2V cyl heads.

The engineers at P&WA and Rolls Royce certainly knew the advantages of sleeve valves; they would have been reading the same journals and technical reports as Roy Fedden and Frank Halford, and they were all capable of doing the same sort of math. The engineers and the management at those companies also could look at their disadvantages and do a cost-benefit analysis, and conclude that sleeve valves were not worth the bother. Instead, they constructed highly optimized, very carefully designed engines that could sustain high outputs, be mass produced by subcontractors with no prior aviation experience, and perform reliably in service. Napier leapt onto the sleeve valve bandwagon and produced a complex engine that they couldn't manufacture without outside technical assistance and machinery that didn't exist in the UK.

 

[J.A.W.]

Still don't like auto-wrap?

Whassat? Is it anyfink like gladwrap? L.o.l...

 

[J.A.W.]

The engineers at P&WA and Rolls Royce certainly knew the advantages of sleeve valves; they would have been reading the same journals and technical reports as Roy Fedden and Frank Halford, and they were all capable of doing the same sort of math. The engineers and the management at those companies also could look at their disadvantages and do a cost-benefit analysis, and conclude that sleeve valves were not worth the bother. Instead, they constructed highly optimized, very carefully designed engines that could sustain high outputs, be mass produced by subcontractors with no prior aviation experience, and perform reliably in service. Napier leapt onto the sleeve valve bandwagon and produced a complex engine that they couldn't manufacture without outside technical assistance and machinery that didn't exist in the UK.

Yet, amazingly somehow, the backyard tinkerer, poor bloody Brits did get their 'Hyper' mill into combat,
& usefully so, unlke the mighty US military-industrial complex, which only produced the 'Hype', but not the engines..

 

[J.A.W.]

From what I read the problem wasn't so much of the design of the Sabre but of mass producing it.

Yep, the fact that the RAF kept their Sabres flying hard ( the manner which suited them best) right up to the mid `50s
- indeed, proves that very point.

 

[wuzak]

The engineers at P&WA and Rolls Royce certainly knew the advantages of sleeve valves; they would have been reading the same journals and technical reports as Roy Fedden and Frank Halford, and they were all capable of doing the same sort of math. The engineers and the management at those companies also could look at their disadvantages and do a cost-benefit analysis, and conclude that sleeve valves were not worth the bother. Instead, they constructed highly optimized, very carefully designed engines that could sustain high outputs, be mass produced by subcontractors with no prior aviation experience, and perform reliably in service. Napier leapt onto the sleeve valve bandwagon and produced a complex engine that they couldn't manufacture without outside technical assistance and machinery that didn't exist in the UK.

Rolls-Royce/Ricardo built a couple of sleeve valve engines before Napier did.

Namely the RR/D and RR/P. These were converted Kestrels, the first an unsupercharged Diesel and the latter a (IIRC) supercharged petrol version.

The theory at the time (~1930) was that the poor quality fuel would hamper power increases. So they turned to Diesel, as that could cope with poor quality fuels.

Secondary to that, it was shown by Ricardo that the sleeve valve could cope with higher compression ratios than the poppet valve engine. But, as so often is the case, the problem became moot as fuels improved and the sodium cooled exhaust valve was invented.

Rowledge, who had moved from Napier to Rolls-Royce in the early 1920s, also designed the Exe, which first ran in 1936, about 15 months before the Sabre did.

And, of course, there was the Crecy. This evolved from Ricardo's work on a 2 stroke sleeve valve Diesel, becoming the spark ignition Crecy later on. Napier was also involved with Ricardo's research early on, and this may have led to the development of the Sabre.

 

[Shortround6]

Yet, amazingly somehow, the backyard tinkerer, poor bloody Brits did get their 'Hyper' mill into combat,
& usefully so, unlke the mighty US military-industrial complex, which only produced the 'Hype', but not the engines..

Granted the US had a number of flops but this bashing of entire countries isn't getting us anywhere nearer to the truth is it?

Napiers lack of machinery (chronic throughout both England and the United States at this time) called for six Sidestrand Centerless grinders to be shipped via the Queen Mary from the US to England to help solve the crisis.
This set back the P & W Kansas city plant (which built ONLY "C" series R-2800s as used in F4U-4s, and P-47M&Ns) 6 weeks until replacements could be obtained. By the the end of 1944 this plant was making over 400 engines a month so this aid to Napier cost over 600 engines in 1944.

While troublesome in service the R-2800 "C" did hit one HP per cu in with it's crappy old fashion 2 OHVs and pushrods. Post war "C"s were good for 2400hp with water injection for take-off using a 2 speed one stage supercharger in routine service in airliners.

I would note that both Curtiss and Packard had used 4 valves per cylinder on their V-12s back in the early 20s so the concept and advantages were not unknown to american engine designers.
Also P & W (and Wright) were using basically hemispherical combustion chambers with widely staggered valves even on their small engines.

Without actual flow tests of the heads involved we are pretty much whistling in the dark.

 

[J.A.W.]

Indeed S-R 6, a century ago the Napier Lion featured DOHC 4V, & *crank-end pressure lubrication,
along with jets on the conrods to squirt-cool the slipper pistons of its oversquare recip' core..

I'd heard that those 'oft quoted' special grinders - were actually an artefact of the Brit propsal to have Chrysler Corp
licence-build Sabres to slot into Bell-made Typhoons along with GE turbos.. & had been 'cash & carry' owned..

Len Setright once 'elegantly' described the R-2800's ability to maintain its impressive output figures - in flight, as "ephemeral" & duly contrasted them with the Sabre's service rating capability of an hour in 'climb power'..

Even the air-cooled Bristols could tolerate higher CHT's than that notably excellent P & W mill,
& without the 'power-fade' caused by heat-soak - which powerful radials were prone to suffering from.

Indeed Hawker test pilot ( & WW 2 ace) Neville Duke delivery flying a Centaurus Fury overseas, in the late `40s beat the record time from London-to-Rome which had been recently established by the Vampire jet.

There is a NACA research paper which tests sleeve valve port/time/area & flow co-efficients,
they also demonstrated useful swirl, not having a large poppet head obtunding the quick-opening port..

*R-R finally emulated this feature of the venerable Lion's lube-tech, for the final hi-po Merlin series..

 

[J.A.W.]

This link: http://www.flightglobal.com/pdfarchive/view/1947/1947 - 1491.html to 'Flight',
provides a data table in which the final Sabre iteration appears capable of these best economy figures:

57 (imp) gallons per hour @ 2,500rpm on +0.5lbs boost - for 900hp @ 11,750ft,
anyone got a C-type R-2800 (from an F4U-4 spec chart, maybe) to compare?

Also worth a comparison - as sleeve-valve/poppet & radial/V12 - are the Merlin & Hercules data sets,
esp' given these two saw use as alternative 'power-egg' installations - in various airframes..

Edit: added further link;
& this 'Flight' link: http://www.flightglobal.com/pdfarchive/view/1944/1944 - 2008.html
presents a chart showing the volumetric efficency of the Bristol Hercules - in 1944..

 

[pbehn]

Yep, the fact that the RAF kept their Sabres flying hard ( the manner which suited them best) right up to the mid `50s
- indeed, proves that very point.

What proves what point? The Typhoon was retired in October 1945, presumably before winter started because the engines had to be kept constantly warm and run up through the night in the previous winter. How many Sabre Tempests were in service post war?