Westland Whirlwind alternative engines?

[Shortround6]

I think castigating RR for not developing diesel tank engines is one of the sillier things I've seen on here. They didn't set out to design tank engines at all, they were in the business of building aero engines. The fact that the Merlin made a decent engine for a tank in the form of the Meteor was just a happy chance.

Why not have a go at them for not developing speed boat engines, it makes as much sense, or criticise Wright for not developing diesel tank engines.

Well. actually RR did develop a speed boat engine, sort of. A few fast craft were equipped with a marine Merlin but the idea went nowhere when they figured out that they needed all the Merlins they could get for aircraft.
Wright didn't develop tank tank engines but the Guiberson company did use Wright engines as a basis for several different tank engines.

 

[stona]

Anyone know how many launches/MTBs were Rolls Royce powered? I seem to remember that some were powered by American V-12 petrol engines, but I could be wrong, this is not really my thing.
Cheers
Steve

 

[Shortround6]

I have seen a number of "70" marine Merlins supplied but at 2 or 3 engines per boat and some engines held as spares I have no idea how many boats were actually Melrin powered.
I believe it was after they decided to not use Merlins that they tried to use Issota-Fraschini engines.
The Vast majority of British small fast craft were powered by American engines. Packard supplied thousands of V-2500 marine engines for Vosper and Thornycroft boats and Fairmile Ds
The Fairmile A, B and Cs were powered by American Hall-Scott engines.

 

[Ascent]

Well. actually RR did develop a speed boat engine, sort of. A few fast craft were equipped with a marine Merlin but the idea went nowhere when they figured out that they needed all the Merlins they could get for aircraft.
Wright didn't develop tank tank engines but the Guiberson company did use Wright engines as a basis for several different tank engines.

That was kind of my point. And the Wright R974 was used to power thousands of M4 and M4A1 Sherman's. The engines were used because they were available and filled a need, they weren't created specifically for those tasks.

 

[rochie]

A few belated comments:

1. I would be quite careful with Rubbra's memoirs as any sort of gospel. After all, he is extremely dismissive towarss direct fuel injection and turbocharging. Both areas in which R-R failed miserably. In the section dealing with the the Merlin's valve gear, he fails to admit that R-R screwed it royally by adopting those fixed cam followers, whose problems were never completely solved. V-1710, DB 600 srs and the Jumo 211/213 all used roller followers.

2. If Dowding dismissed the Whirlwind as a night-fighter for "high landing speed", he was incompetent as landing speed alone is meaningless in determining how easy an airplane is to land.

3. The idea that the Hurricane could do all the Whirly could do is obviously horseradish. The Hurricane is among the most overrated aircraft of WW2. E.g. Russian pilots disliked it s lot and Finnish Buffaloes made mincemeat of opposing Hurricanes. It was considered one of easiest opponents to shoot down.

4. A feasible alternative engine might have been the R-1820. If W-pedia is correct on the Peregrine's weight, the Cyclone did not weigh much more and gave 1200 hp on 100 octane at that time.

 

[tomo pauk]

...
Everybody praises the German direct fuel injection but few want to actually consider it's faults.
1. RR got a drop of 25 degrees C in the intake due to the fuel vaporization in the supercharger and manifolds. This allowed for slightly higher boost pressure to be used.
2. The German fuel injection as used did not allow for running extra rich and using the extra fuel as coolant allowing for higher boost.
3. The German fuel injection as used did not allow fro running extra lean and allow for long range flights in non-combat environments.
4. The German fuel injection used many more parts than the British carburetors. RR did not make their own carbs, they bought them form an outside vendor, so did the American engine makers.
Who was going to make the direct Fuel injection systems for the British and what else was NOT going to get made?

Perhaps RR glosses over the last part a bit easily but it is a very real concern to the British.

1 and 4: people rarely mention that big/powerful V12s with single carb, like the Merlin and V-1710, needed backfire screens installed before cylinders, meaning a loss of rated altitude vs. an engine that does not have backfire screens. Eg. on the V-1710 difference was 1000 ft at 1-stage engines, 1500 ft on turboed. RR (and some other engine manufacturers, not just from the UK) purchased bad carbs - switch to the 'fuel pump' type ('pressure injection' as the called it acros the pond) gained 8-10 mph for the Spitfire V, plus 1500 ft worth of ceiling. Fuel pumps were installed after half of the war passed. Further, the bad type of carb meant that ice guard is needed for really hi-alt flying, again an 8 mph loss.
Granted, carbs were far simpler things.
2. BMW 801D certainly used extra-rich fuel mixture as a mean for cooling the engine when extra boost for more power was needed, managing 1900-2000 HP in low gear from mid 1943 on (before they swithched to a simpler system).

 

[Shortround6]

The Men at RR figured that a 25 degree C drop in intake temperature was good for about a 10% increase in gas flow through the supercharger. It changed the compression ratio of the supercharger from a theoretical 2 to 1 to 2.12 to .

This was at sea level at temperatures between 0 and 15 degrees C to begin with. It was also with "fresh" gasoline.
Old gasoline often has some of the most volatile components already evaporate out. Or "fresh" gasoline held in the aircraft tanks on a hot day.

As the intake temperatures fall with increased altitude the rate or effect of vaporization also falls, until 0 vaporization occurs at temperatures between -20 degrees C and -40degrees C however this is counteracted to some extent by the lower air pressure. The 0 evaporation temps being for a pressure of 760mm. lowering the air pressure to 300mm ( a bit over 23,000ft) lowers the 0 vaporization point about another 18 degrees C.

For practical estimates a drop of 20 degrees C can be used (8% increase in mass flow?) up to 20,000ft with the 20 degree drop being an overestimate at higher altitudes.

Numbers are from the Rolls-Royce Heritage Trust book "The Performance of a Supercharged Aero Engine" by Stanley Hooker, Harry Reed and Alan Yorker. Much of this section of the book (pages 33-34) is based on a paper by Oscar C. Bridgeman "The Equilibrium Volatility of Motor Fuels from the standpoint of their use in Internal Combustion Engines." from 1934.

It should be noted that this evaporation is for the fuel before it reaches the eye of the supercharger. Once it has been subject the to the temperature rise in the supercharger the temperature of the mixture entering the intake manifold/s is subject to the full 25 degrees C drop.

Please note that a Merlin XX engine has a temperature rise at full throttle of 145 degrees C through the supercharger.

I would also note that the Allison, P & W , Wright and Bristol engines (and many others) also got a similar "boost" from fuel evaporation.

 

[herman1rg]

Great piece of information

 

[tomo pauk]

The Men at RR figured that a 25 degree C drop in intake temperature was good for about a 10% increase in gas flow through the supercharger. It changed the compression ratio of the supercharger from a theoretical 2 to 1 to 2.12 to .
...
Numbers are from the Rolls-Royce Heritage Trust book "The Performance of a Supercharged Aero Engine" by Stanley Hooker, Harry Reed and Alan Yorker. Much of this section of the book (pages 33-34) is based on a paper by Oscar C. Bridgeman "The Equilibrium Volatility of Motor Fuels from the standpoint of their use in Internal Combustion Engines." from 1934.
...
Please note that a Merlin XX engine has a temperature rise at full throttle of 145 degrees C through the supercharger.

I would also note that the Allison, P & W , Wright and Bristol engines (and many others) also got a similar "boost" from fuel evaporation.

Thank you for the detailed post.
Re. RRHT book, I do have a few questions, not that I'm saying youre obliged to find answers to them willy-nilly. Like - is i clear from the book how much a performance penalty represented the installation of the float-type carb on, say, Merlin, vs. pressure injection ('fuel pump')? Any carb vs. no carb at all? In 'no ram' condition as well as with ram air? Is it clear how much the flame traps ('backfire screens' in US parlance) were a detriment to the rated height? How much did a necessity to have some sort of heating of the carb was involving how a big turbulence of the airflow through a carb? Was there any benefit from fuel evaporation in the cylinders of a direct-injected engine? Fuel consumption differences?

 

[Shortround6]

The book is pretty much concerned with the Merlin XX engine and in fact seems to be a reprint of a book or papers first published in 1941 so many of your questions do not apply.
It has a lot of formulas and charts and seems to be a handbook for RR (or allied?) engine designers on what they had accomplished up until then with a lot of comparisons between theory and test flight results.
The section on ejector exhaust manifolds for example starts on Page 16 and runs to the end of Page 22 but there are some full page charts in there.

Please remember the one of Hookers claims to fame was realizing that some of the formulas that were in text books on supercharger design were wrong. Getting useful formulas that were backed up by flight testing was a good step in the advancement of supercharger design.

There is a short section on the effects of forward facing air intakes.

 

[tomo pauk]

Thank you again.
Basically - instead of naming the book, say, "1934-1941, design practies at Rolls Royce V12 aero engines department", someone named it "The Performance of a Supercharged Aero Engine" - not just as if radial and diesel engines don't exist, but no one else in the world is/was designing aero engines?

 

[Shortround6]

To be charitable one might look at the title "The Performance of a Supercharged Aero Engine" as being about one particular supercharged aero engine and not a compendium of ALL supercharged aero engines. Most of which the engineers at Rolls Royce had little or no first hand knowledge of in 1941.
I have no idea how much distribution the book actually had at the time but most companies were not going out of their way to share their research and development with their competitors.

There are charts showing results of calculations in comparison to flight test results and differences between RR flight tests and flight tests by Hawker Aircraft. Or differences between ground tests and flight tests to see the variations (check on theory).

 

[ChrisMcD]

Thank you for the detailed post.
Re. RRHT book, I do have a few questions, not that I'm saying youre obliged to find answers to them willy-nilly. Like - is i clear from the book how much a performance penalty represented the installation of the float-type carb on, say, Merlin, vs. pressure injection ('fuel pump')? Any carb vs. no carb at all? In 'no ram' condition as well as with ram air? Is it clear how much the flame traps ('backfire screens' in US parlance) were a detriment to the rated height? How much did a necessity to have some sort of heating of the carb was involving how a big turbulence of the airflow through a carb? Was there any benefit from fuel evaporation in the cylinders of a direct-injected engine? Fuel consumption differences?

As a slight digression, have you come across Rod Banks' work sorting out the Fiat engine on the Schneider Trophy Macchi-Castoldi M.C.72?

Macchi Aeronautica Archives - This Day in Aviation

Shows the lethal effects of backfires when the ram effect was not taken into account!

 

[stona]

1938 A&AEE report gives the landing run for the Whirlwind as 635 yards, well within the capabilities of airfields of the time.

It was not the safest aircraft to fly. According to the two relevant squadron ORBs 132 pilots flew the Whirlwind operationally, and 46 were killed.

The conversion to fighter bomber was not always popular either. Unofficial, that is before A&AEE, tests were carried out by F/L Rudland on 12th August 1942, who described the loss in speed and various other factors caused by the bombs before promptly putting in for a transfer, concluding with the words

"If I had wanted to drop bombs I would have flown a Lancaster."

As far as the engines go, when the first Peregrines were delivered in February 1940 the decision had already been taken to limit production to 290 units, barely enough for the 114 Whirlwinds built, so it did die with its engines. There was never a serious effort to re-engine the aircraft, despite Petters letter to Leigh-Mallory, who had little influence on which aircraft the Air Ministry/MAP produced anyway.

Cheers

Steve

 

[Shortround6]

The safety would have to be put into context. Like pick another two squadrons operating similar missions in the same area and compare losses for a similar period of time.
Some pilots thought they stood a better chance in crash landing in the Whirlwind as the engines/nacelles usually hit first and took a fair amount of the impact, without coming back into the cockpit like some single engine fighters.
Some pilots made it back due the twin engines. Some may not have made it back due the twin engines, poor engine controls, lack of feathering propellers and cross over fuel systems.

Low altitude strafing/bombing missions are usually high risk.

Some fighter pilots only want to fight other aircraft.

I would also note that the bomb racks on the Whirlwind were pretty basic,

Compared to the racks + fairings fitted to Typhoons, Tempests

Hurricanes

Wartime reporting being less than accurate

 

[Old Wizard]

 

[stona]

I would also note that the bomb racks on the Whirlwind were pretty basic,

They were also time consuming to retro fit, the entire outer wing section had to be removed.
Why waste time developing a special fairing for an aircraft operated by two, usually under strength, squadrons?

Low altitude strafing/bombing missions are usually high risk.

17 of the 46 were killed in flying accidents, not in action.

For this the two squadrons claimed 13 enemy aircraft destroyed and 18 damaged, though one was a Blenheim of 1401 Meteorological Flight and doesn't count. That is no reflection on the Whirlwind squadrons, these things happened unfortunately, probably more than we'll ever know.

Cheers

Steve

 

[stona]

Tactics for making bombing attacks on shipping: It took a lot of aircraft to protect the actual fighter bombers.

OUTWARD FORMATION - ANTI FLAK FIGHTERS

Anti-flak fighters leading, in Flights line abreast, with aircraft line abreast 1,200 yds between Flights, 50 yds between aircraft, &100 feet above sea-level.

BOMBERS

In sections line abreast 50 feet above sea-level & 400 yds behind the anti-flak fighters.#2s in each section flying two spans out and one length behind their #1s. In this formation, the leaders are in the best position to choose the targets. If eight aircraft are used, repeat the formation for four aircraft, Flights astern.

ATTACKING

Fuse bombs & put both selector switches to the 'on position immediately on setting course.
Swing into the best position on sighting enemy (1.e. abeam or up sun). It is better to spend two minutes doing this than to attack without thought immediately on sighting. In the formation given above, each section of bombers will be able to follow the corresponding anti-flak Flight onto target.
Time your attack so that you are about on target as the anti-flak fighters break away. If both you and the Spit boys have your finger out, the last anti-flak cannon shell should beat your bombs to the target by a short head. In this way, less flak will be experienced as often the fighters draw the ships' fire.
Concentrate on your bombing run, make this absolutely on the deck. Fly straight at your ship, and plant your bombs on the waterline.
Keep your camera button pressed on your run in so that you can prove to the Intelligence Officer that it was a 4,000 tonner, not a 150 ton coaster. Most Intelligence Officers have never heard of a ship of more than 1,000 tons anyway, and you will be able to say, 'I told you so', when the combat film comes back.
Do not jink, it serves no purpose and only spoils your aim.
Do not fire your cannon, it is nice to hear the noise, but you cannot do both jobs at once, and will only make a cock of both. Leave anti-flak to the Spits.
Both aircraft in a section must attack the same ship. Better one ship at the bottom than two damaged.
Both aircraft should pass over the ship practically together. In this way the early demise of the #2, who might otherwise be blown up by his leader's bombs, will be avoided.
After bombing, pull over the masts (recommended) & get down on the deck again. DO NOT career wildly over the sky under the impression you are taking evasive action.This only makes everyone's job, particularly the escort, more difficult.
Keep Station. The leader will throttle back immediately after leaving the target area to make this easier.
If attacking at night you will naturally attack into the moon. Bank sharply, right or left, keeping ow, immediately after. If you keep straight on you will make a nice target silhouetted against the moon.

REMEMBER - FLAK LOOKS A LOT WORSE THAN IT IS

RETURNING HOME

Bomber leading, Sections line abreast, & 100 - 150 yds apart. The #2s 100 yds behind and 100 feet above their #1s.
Anti-flak will escort, the former escort giving rear cover.
Defuse Selector switches to 'off' before crossing the coast.
Do not shoot a line to the Intelligence Officer about the size of the ship. An M-Class minesweeper looks like a destroyer. A destroyer looks like the Scharnhorst. Be modest, halve your estimate of tonnage, & wait until your camera films have been developed.

Cheers

Steve

 

[Shortround6]

They were also time consuming to retro fit, the entire outer wing section had to be removed.
Why waste time developing a special fairing for an aircraft operated by two, usually under strength, squadrons?

I agree with the 2nd, but then don't complain or use the lower performance as a strike against the Whirlwind.

17 of the 46 were killed in flying accidents, not in action.

For this the two squadrons claimed 13 enemy aircraft destroyed and 18 damaged, though one was a Blenheim of 1401 Meteorological Flight and doesn't count. That is no reflection on the Whirlwind squadrons, these things happened unfortunately, probably more than we'll ever know.

How many pilots were lost in flying accidents by the first two Typhoon squadrons over a similar span of time?

Or even Hurricane squadrons?

17 pilots lost due to accidents is still 17 too many but it took another 10-15 years for flight safety to really become an important part of ANY air forces culture.

Using enemy aircraft destroyed as a measure of a strike fighters success seems a bit biased. How many Railroad wagons and locomotives were shot up even before the bombs arrived, How many coastal craft? Other assorted ground targets? A few mission were against distilleries, what 20mm shells were going to do against a distillery I have no idea but they were among the targets ordered from on high.
One also has has to ask how many Blenheim crews were saved by using Whirlwinds as bait instead of Blenheims in those "lean forward into France missions."

 

[stona]

Using enemy aircraft destroyed as a measure of a strike fighters success seems a bit biased.

It served operationally as a fighter for almost two years, from December 1940 until October 1942, and for a bit more than half that time, until December 1943, as a fighter bomber. It is usually most remembered for the latter and shorter period.
263 Squadron diary for 1st December 1943:

"Our new Typhoons have arrived, with their shiny paint and fittings they rather make the ole faithful Whirlies look a trifle shabby. The latter have given stout service and the squadron have been very proud to fly them."

Many of the men who flew the obviously liked them, but they were aware that they were coming to the end of their useful service life. After a celebratory dinner given by Westlands for the squadron (described in the diary as a 'piss up', a term familiar to any English english speaker) the next morning

"Greenish googly faces peering into the CO's office were informed of a Squadron Balbo over Westlands. Three lines of (incredibly crooked) Whirlwinds staggered over Yeovil. If the worthy workers were not impressed, the staff of the Watch Office had their full quota of entertainment by a talk over the R/T by S/L Baker entitled 'Words not in the English Dictionary' or 'Pull your fingers out you bastards.'"

There were never enough of them to make a significant difference to anything. I think that the most that ever flew together on any one mission was fourteen (when 263 conducted their own anti-flak flying 'Whirlwinds with bomb racks removed'), and generally it was a couple of flights, often escorted by squadrons Spitfires.

Cheers

Steve