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Inline VS Radial

Discussion in 'Miscellaneous' started by CAC, Apr 6, 2021.

  1. CAC

    CAC Ace of Spades

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    Boeing XB-38 powered by Allison V-1710V engines

    [​IMG]

    A rough comparison would be:

    Inline - 526 kph - 5300km range

    Radial - 461 kph - 6000km range

    Was speed sacrificed for range?

    How would American aircraft have gone if powered by inline engines? Specifically the Merlin range?
    The US and Japan struggled with designing a good inline engine, one that could compete with the radials...Whilst Germany and in particular Britain designed excellent inline engines. Some of the most lauded aircraft of WW2 - Mustang, Spitfire, Lancaster, Mosquito and Hurricane were powered by this engine. How much of their success was the aircraft and how much do all these aircraft owe their reputations to the Merlin?
    The US correctly thought that the radial was more reliable than the inline...this was in the 30s when inline engines hadn't matured as a technology...but by WW2 this was no longer the case. Why wasn't the Merlin phased into production for all aircraft? Does politics rear its ugly head again here? I read some reasons, but none that were insurmountable...
    The radial is air cooled, which is reliable once airborne (but a problem sitting on the tarmac). The inline had a reasonably heavy cooling system that could break down...one rarely hears of over heating radials in flight, but not so for the Merlin inline. So what is the benefit of a radial...it was comparatively easier to build than an inline...but again, not an argument that means much to me given the production might of the US and UK...

    So...Do these aircraft owe their reputations to the inline/Merlin?
    How would the air war have panned out if more aircraft, particularly multi engined aircraft been fitted up with inlines?

    Some British bombers fitted radials, then inlines, then back to radials...showing that it could be done.
     
    Last edited: Apr 7, 2021
  2. Takao

    Takao Ace

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    Not politics, but reality.

    How long will it take to convert all radial production to Merlin production?

    How long will it take to convert all subcontractors producing radial parts to producing Merlin parts?

    Also, I think you have confused reliability with survivability. The radial continued to run with a cylinder or two missing. With the US focus on daylight bombing, it is understandable that they would want engines that continued to run after taking significant damage.

    Also, a factor would be - at the beginning - limited supercharger/turbocharger production - because their was only one supplier(GE if memory serves).
    How well will an unaspirated Merlin perform at high altitudes?
     
  3. CAC

    CAC Ace of Spades

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    Hmmm...reality? So what you are suggesting is that factories couldn’t retool or that it would be too much trouble? We are not only talking war here but total war. We are talking people’s lives...we are talking American prestige...it’s a complete furphy that it would have been all too much of an ask. I did use the term ‘phase into’...one factory retools while others continue to make radials until it is their turn, after a couple of tries the change over would become quicker and easier. They made the Packard Merlin so it was all too possible. Note I’m not saying ALL aircraft should have had the Merlin or even an inline...just those in frontline service.
    How long did it take to tool for the Packard Merlin...how long for each new aircraft that came into service? How long to tool up for the new radials coming online? It’s a non arguement except for the worst period where numbers where more important than quality/performance. The initial stages of the war for the US in other words.
    Britain and Germany proved you can make both...so why would the US struggle? They wouldn’t. IMO it was because of the initial decisions around the radial were concreted...’jobs for the boys’...deals made around a dinner table...kick backs...National pride...and American stubbornness around things non American were to blame. The Merlin was clearly superior in most instances, the P-51 was an example of the US biting the bullet, I think because they wanted a fighter that could take on the 109s on an even playing field (the 51 was designed with lessons learnt from the 109 and spitfire). - The 47 being the fall back in case of failure.
    Perhaps they thought the Allison would become what the Merlin became...but that never really happened. Although between you and me I think the Allison inline was still a nifty design. (But they were up against names like Daimler and Benz and Rolls Royce).
    Survivability and reliability are interchangeable in this situation...survivability equals reliability and reliability equals survivability...let’s not squabble over words. Plus the relative simplicity of the radial over the inline and the extra years of evolution is what made it more reliable...the designers weren’t thinking bullet holes...
    We are arguing between a draft horse and a thourabred...one works all day everyday...the other brings awesome performance with a greater chance of injury. I would go for performance when dealing with the enemy...fighters and bombers.
     
    Last edited: Apr 7, 2021
  4. CAC

    CAC Ace of Spades

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    And as a second, though related question...why wasn’t the P-40 given the Merlin? Why wasn’t the P-38 given the Merlin? If it was good enough for the frontline fighter P-51, then why not for other aircraft?
     
    Last edited: Apr 7, 2021
  5. Carronade

    Carronade Ace

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    The P-40F and -L did have Merlins. The -K, -M, and -N had progressively improved versions of the Allison, considerably more powerful than earlier models.

    Of course it's not just the engine. None of the P-40s could match the performance of newer designs like the P-47 or -51 (not surprising, really). And late-war P-40s were used largely for ground attack.
     
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  6. CAC

    CAC Ace of Spades

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    Good answer...and the 38? You have to admit...the 38 would have been the scariest thing in the sky with Merlins...
     
  7. Biak

    Biak Adjutant Patron  

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    The P38 was a "dog" until the Brits' stepped in with Good old English "You can do better mate". Supercharger. Google has the story.

    The hardest thing to do in the USA is change something for the better. Turf-wars and power grabs - read Ego stroking - cause delays and exorbitant cost overruns. Couple that with politicians striving to show their brilliance in all matters both mundane and Scientifically advanced studies, to gain a few voters.
    Retooling a factory is the easy part, look how fast we, the US, did it in 1942.
     
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  8. CAC

    CAC Ace of Spades

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    A great and honest answer...explained better than my attempt...(I was blown away when Colt wasn’t renewed in respect to your description)
     
  9. Biak

    Biak Adjutant Patron  

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    Not sure what you mean about Colt, ....on my first cup of coffee so slow start to the morning.

    Today's drawbacks (IMO) include the fact the majority/a lot? of US brand companies aren't in fact US companies. Mining is a large employer with Union scale wages near here, all foreign owned for the most part.

    Basically if it pays well (and you have/get that job) or has that " I want/need that appeal " American Pride gets subverted to individual Me First gratification.
     
  10. Takao

    Takao Ace

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    Do you have a link?

    You see, the British never received a P-38 with a supercharger. The initial order was placed by the French, which who wanted to simplify maintenance & supply, so they ordered their Lightnings without turbo-superchargers or counter-rotating propellers. When France collapsed, the order was handed over to the British. Of the 667 P-38s ordered by France, 143 were to have been without turbo-superchargers, and 534(Lightning IIs) were to have the F-Series engine, turbo-superchargers, and contra-rotating props. However, only one was produced as a Lightning II, and it was retained by the USAAF. The rest of the Lightning II order were completed as Fs & Gs and retained by the US. The only Lightnings handed over to the British were 3 of the original French order that lacked turbo-superchargers.

    So, the British had nothing to do with the fitting of the turbo-supercharger...That had already been done with the XP-38 & YP-38s.
     
  11. Takao

    Takao Ace

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    The older models could not, but the P-40Q could. However, it was not put into production, because the Mustang production was already in full swing and meeting demand.
     
  12. Takao

    Takao Ace

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    No, I am saying it would take too long. Packard only started to produce the Merlin in August, 1941, but did not begin producing in earnest until early 1942

    We are talking about Total War...Getting their firstest with the mostest. Not getting their lastest with the bestest.

    And this is going to take how long? With the attendant drop in production.

    Packard agreed to build Merlins in September, 1940. They produced their first one in August 2, 1941.
    .
    Correct...It's an non-argument. Why switch from a Pratt & Whitney R-2800 Double Wasp to a Merlin?

    They didn't. The Merlin was only as good as it's supercharger at high altitude...Which should be your argument.

    Survivability is the ability to function with damage, reliability is the ability to function over time.
    My car engine has functioned reliably for many years...Now if I took a slegehammer and bashed bits off it, how would it function?

    The first air-cooled radial aircraft engine was produced in 1903...The first inline aircraft engine was produced in 1903...Extra years of evolution - None.
     
  13. CAC

    CAC Ace of Spades

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    Man...where do I start.
    Too long for what? No one new how long the war would go for...Packard took approx six months to begin in Ernest...that’s a little slow, a lack ‘inspiration’ perhaps...I’m sure if you were being bombed on a daily basis you might hasten that turn around, I’m thinking of Britain. And yet six months is still fine in terms of a major factory going online...’Phased in’ you could have four major factories (let’s face it, we are talking America here, way more than four if needed) in two years...plenty of time to make a significant difference in the air war.
    Getting firstest with mostest was, as I said a priority early on with the US...it can’t be argued in my opinion, that the US was in a perpetual state of catch up...at some point they had the breathing room to develop and develop hard...take some risks even, design wise. But I digress.
    Attendant drop in production...one factory, even a major one could be absorbed, especially in a place like the US. If it was a problem, another factory would have been made to compensate...or am I over estimating the ability of the US.at the time? I think not. Other countries dealt with these problems.
    Your point about the Pratt and Whitney is well taken, and one of the arguements I was looking for...this is muscle without grace...but that’s American design for you! : ) I need a slap.
    The Merlin wasn’t as good as its super charger, that’s a silly statement. Would you say that about a V8 engine in a car? It ignores 98% of the rest of the engineering of the engine. Enough said. At altitude it needed one...so? It got one.
    Your car wasn’t designed for a hammer anymore than aircraft engines are designed for bullets, (other than some had critical elements hidden as far inside the engine as possible...only in some engines. Clever) The analogy should be if I crash I have more chance of survivability...but the reliability of your steering and tires prevent the accident in the first place, making your overall survivability in driving that car greater. It certain situations they are interchangable...Again it’s a quibble in my eyes...have your way on this one.
    The radial was favoured for a number of reasons, it was simpler and more reliable which was becoming important with the growing amount of dead flyers early on. Being favoured it was developed ahead of the inline...but I have a feeling you know that. The inline was an early conception, liked for it streamlining.
     
    Last edited: Apr 8, 2021
  14. Biak

    Biak Adjutant Patron  

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    Do I have a link?

    One of several; Der Gabelschwanz Teufel - Assessing the Lockheed P-38 Lightning

    The P-38 was clearly a hot performer and the UK Air Ministry and French AF soon took an interest in the type, seeking a non-turbocharged variant with identical powerplants (and same sense prop rotation) to the Curtiss Tomahawks at that time ordered in significant numbers. Designated the Model 322B and F respectively, the RAF promptly sought a total of 667 of these aircraft, a far cry from the 60 or so which Lockheed expected the US government to purchase. Unfortunately, the buyers did not appreciate the limitations of the V-1710 without turbochargers and Lockheed negotiators accepted the order in spite of the known discrepancy and objections from engineering.

    The RAF was unhappy with the 322, as its high altitude performance was inferior to the then current Merlin 40 series powered Spitfire V. The 322 had by that time also demonstrated problems due compressibility in dives which caused 'Mach tuck', a severe nose down pitching moment due to the aft of the CoP. This often led to the breakup of the aircraft and usually, loss of the pilot. Like prop rotation sense impaired engine out handling. The 322 affair escalated into a major dispute between Lockheed and the RAF and in the end, all Lightning I airframes were transferred to the USAAF which used them as trainers, under the designation of P-322. The turbocharged Lightning IIs became USAAF production P-38Gs.

    To validate my comment above ;


    Interestingly, the performance problems could have been fixed by fitting Merlins, Lockheed engineers considered this seriously enough to do a paper study in 1941 which indicated that Merlin XX powerplants would provide superior performance, while improving reliability
    The US Army however rejected the idea (it has been stated as under the influence of US commercial interests) and thus sentenced the P-38 to engine problems which were not solved until mid 1943.

    forgot to add : https://apps.dtic.mil/dtic/tr/fulltext/u2/a604401.pdf
     
    Last edited: Apr 7, 2021
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  15. Sheldrake

    Sheldrake Member

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    Not every aircraft could be powered by Merlin engines.

    #1 Until Packard started to build Merlins in quantity in America there was a shortage of Merlin engines with the Spitfire, Hurricane and Lancaster taking priority. The utterly brilliant idea of turning the Merlin into a tank engine was delayed in implementation because aircraft had priority and the first Meteor engines were made from reconditioned damaged engines that could not be used in aircraft.
    //2 Other engine makers were turning out engines that could be put to good use. There were lots of commercial and practical reasons why the entire aero-engine industry could not be turned over to building the Merlin.
     
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  16. Carronade

    Carronade Ace

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    I've had that thought, remember discussing it with a friend years ago. My guess was that with -47s and -51s in service, major modifications to the -38 weren't a priority. Of course it did improve considerably in later models.

    As noted, vulnerability to damage was an issue with inlines, but that would be mitigated in four-engine aircraft like the Lancaster or the XB-38.
     
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  17. Takao

    Takao Ace

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    Unfortunately, the quote does not support your contention, that it was the because of the British.

    The part you should have highlighted...
    Lockheed knew it would be a "dog" without the turbos....And, surprise, surprise, surprise...It was a "dog" without turbos.

    The customer is always right....No matter how wrong they are.
     
  18. bronk7

    bronk7 Well-Known Member

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    good thread...interesting information ..thanks
     
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  19. Biak

    Biak Adjutant Patron  

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    Damn I didn't know this was a test.
    Fortunately I've learned a valuable lesson over the last 4 - 5 years. Sure Okay.
     
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