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Tempest Mark V research


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4 minutes ago, VO101Kurfurst said:

Sure sure.

 

Thankyou for this compelling argument.

I would also like to point out that the Tempest on the alternative BoBp box art is a Sabre IIB series aircraft.

 

bobp-tempestv-cropped.jpg

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1 hour ago, VO101Kurfurst said:

 

Regardless of what may seem logical or not, it is a fact that the RAF decided to revert to +9 lbs once the V-1 menace was over. 'Tis what it says, black on white. Its for the Sabre IIA I might add. The document is dated sometime September 1944. Its part of a document that says that all UK based Squadrons shall revert to 130 grade anyway after the V-1 threat has ended.

 

Now it makes sense given how poorly the Sabre was constructed and how unreliable it was. + 11 was definietely pushing things in an already very unreliable engine, which may have been OK for operations above / near the British Isles, when pressed with the need to intercept the very fast V-1s by all means, but not OK when over enemy territory, in operations. Now that it could do with 130 grade at +11 is not so shocking, the Sabre, being a big engine with high rpm, could do with far less extreme manifold pressure than for example Merlins.

 

Were Sabre IIBs an exception? Perhaps, but how many of them were in operations? Judging that production started only in September, I would excpect Sabre II As produced from long before to be the majority and the Sabre II Bs the minority in Tempest units.

No the document says 'intension to reduce'.. Whether that happened or not is not stated.

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3 hours ago, VO101Kurfurst said:

Now it makes sense given how poorly the Sabre was constructed and how unreliable it was.

Where do you get that from? It was a succes despite the constant political backstabbing by RollsRoyce and it is the only inline engine that eventually was in the power class of the Wasp Major, an engine twice the displacement and at almost half the weight.

 

Sabre IIB was the engine commonly used when the sqadrons were transferred to the continent. By the end of March '45, some of the Tempests were mounted with the VA, giving 3050 hp WEP power. So much for unreliable.

 

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VO101Kurfurst

The reliability issues that sorrounded the Sabre all over the place. In Normandy, Typhoons had reoccuring problems with Sabres spontaniously cathing fire on start up. Typhoon pilots even had semi humorous signs  painted on the aircraft telling the ground crew what to do in case of engine fire

 

‘Dont Just wave your hands - try putting the damn thing out of fire’ or something along these lines.

 

Even the Germans noticed it in their technical reports. In a report dated december 1944 they laconically stated that the engine would need a redesign from scratch to make it workable.

 

Does not sound so reliable to me. It was basically discontinued as soon as the war was over.

 

Its a cool engine and I like Napier’s weird designs quite bit, but the Sabre was crap to begin with and only become mildly acceptable for operations even after much development.

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You can ignore kurfurst on this one too guys, it's a well known fact across many scholars that the Sabre IIA and IIB was one of the most reliable piston aeroengines ever designed other than the ground fire issue which was never solved. There are books and books on this.

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VO101Kurfurst

Close that scholar and never open again. Be sure.

 

German report from 27 December. Several Sabre IIAs were test run by DVL, the German Aerodynamic Research Institute. A high rate of failures was observed.

 

 

48BB1D53-09FA-4D2F-B5AF-975EB4E8FC54.jpeg

Edited by VO101Kurfurst
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Not Tempest engines so almost certainly not modified IIAs. Irrelevant. Tempests had a lower engine failure rate than 130 octane Merlins.

Edited by Talon_
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36 minutes ago, VO101Kurfurst said:

Close that scholar and never open again. Be sure.

 

German report from 27 December. Several Sabre IIAs were test run by DVL, the German Aerodynamic Research Institute. A high rate of failures was observed.

 

 

48BB1D53-09FA-4D2F-B5AF-975EB4E8FC54.jpeg

If i was employed by the RLM, I would have written something like that as well. Funny enough they mention the Sabre V that without significant alterations in fact got a nice 25% power increase.

 

And yes, Coffman engine starters are temperamental. No one used them if there was even the slightest possibility of an alternative.

 

Also, if it was an unreliable engine by 1944, there must have been a significant number of aborted missions. There weren't. At least nothing unusual compared to other aircraft. Also, it is slightly funny to say that the engine was a dud, when in fact it powered some of the most importat (and successful) types of (British) aircraft for over three years. RollsRoyce surely would have loved to supply Griffons, but for that it would have to succeed and kill Napier first to get a hold of its shops to get added capacity. They tried. And failed. At least initially. The Napier engine worked. The best racing engine of the war. ;) Thus, the fact that it was discontinued has nothing to do with its reliabilty but was a political decision. But in the end, when engines were in less demand, you cut the fancy stuff. Oddly enough, the Centauris was also a "compliacted" sleeve valve engine. So it was really just about allocating ressources. And Napier pulled the short straw.

 

22 minutes ago, Talon_ said:

Not Tempest engines so almost certainly not modified IIAs

Tempests had IIB form the start and later on VA. Seems the Germans found some Typhoon remains. The German Flak gunners must have brough them plenty.

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4 minutes ago, ZachariasX said:

Tempests had IIB form the start and later on VA. Seems the Germans found some Typhoon remains. The German Flak gunners must have brough them plenty.

 

Tempests had modified IIAs that brought them up to IIB standard if built pre-september 1944. Four modifications were needed.

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1 minute ago, Talon_ said:

 

Tempests had modified IIAs that brought them up to IIB standard if built pre-september 1944. Four modifications were needed.

But  these modifications were done at the factory?

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1 minute ago, ZachariasX said:

But  these modifications were done at the factory?

 

They could be done at the airfield.

For those interested, the manual for the Tempest Mk V target tug is available here: http://www.deutscheluftwaffe.com/archiv/Dokumente/ABC/a/Alliierte/Tempest TT MK 5 manual.pdf

 

@Jason_Williams Tempest cockpit diagrams and pictures inside - shows the modifications from a normal Mk V

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8 hours ago, VO101Kurfurst said:

 

This document leaves no doubt that that +11 lbs was cleared for the Sabre II by M.A.P. only for the duration of the V-1 menace (i.e. summer 1944) and was then reverted to +9 lbs in September 1944, after the V-1 raids were over.

 

It appears +11 lbs was more of an 'act of desperation', valid for a limited scope (V-1 hunting) rather than an officially sanctioned boost for normal operations.

 

 

 

Except I am not talking about the Sabre IIA, but the Sabre IIb, a different engine, whatever beef you have about the Allies getting 150 Octane fuel, fact is the Sabre IIb, which was most definitely fitted on Tempests by 1945, could reach +11lbs boost on 130 octane fuel

 

Another image

http://www.flight-manuals.com/napsab-pn.html

yhst-25743750278216_2244_262414401

yhst-25743750278216_2244_262661667

 

 

 

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VO101Kurfurst
10 hours ago, RoflSeal said:

Except I am not talking about the Sabre IIA, but the Sabre IIb, a different engine, whatever beef you have about the Allies getting 150 Octane fuel, fact is the Sabre IIb, which was most definitely fitted on Tempests by 1945, could reach +11lbs boost on 130 octane fuel

 

Another image

http://www.flight-manuals.com/napsab-pn.html

 

 

Thanks for the images. There is no doubt that the Sabre IIBs were rated for +11 lbs, and as noted it was possible on even the standard 130 grade fuel. This leaves us with the question - how many Sabre IIAs and Sabre IIBs were there in operations. I understand later series of Tempest received the IIB, but how many in operations had the IIA and how many the IIB.

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If you consider thatby september 44 the IIb was in production, (IIb factory equipped aircrafts arrived on the continent a bit later), then all replaced engines from this point on were IIbs.

The modification from a IIa to a IIb was a relatively simple one, and during the month of January, at Volkel, the last 13 aircrafts with serviceable IIa were modified to IIb, the rest having had their engines replaced at this point...

 

Basically all of them starting january, and a majority around November and on.

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VO101Kurfurst

This seems quite reasonable Quinte. I had the description of the Tempest series and their engines and other modifications, by production batches, but I cannot find them at the moment.

 

Do you have a reference to the modifications done at Volkel? 

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First production batch of 100 aircraft built by Hawker aircraft Ltd., Langley, Buckinghamshire. JN729-JN773, JN 792-JN822, JN854-JN877. Most aircraft completed as Series 1 (with long barrel Hispano Mark II cannon) and some as Series 2 (with short barrel Hispano Mark V cannon); some aircraft retrospectively modified to Series 2 standard. One aircraft, JN750, completed as a Tempest Mark II. Deliveries to RAF commenced 12-43, completed 5-44; average rate of production, approximately four aircraft per week.

 

Second production batch of 300 aircraft built by Hawker Aircraft Ltd, Langley, Buckinghamshire. EJ504, EJ518-EJ560, EJ577-EJ611, EJ626-EJ672, EJ685-EJ723, EJ739-EJ788, EJ800-EJ846, EJ859-EJ896. Series 2 aircraft, Sabre IIA engines with modifications, short-barrel cannon, spring tab ailerons. Deliveries commenced 5-44, completed 9-44; average rate of production approximately 18 aircraft per week.

 

Third production batch of 199 aircraft built by Hawker Aircraft Ltd, Langley, Buckinghamshire. NV639-NV682, NV695-NV735, NV749-NV793, NV917-NV948, NV960-NV996. Sabre IIB engines and spring tab ailerons. Deliveries commenced 9-44, completed 2-45; average rate of production approximately 12 aircraft per week.

 

Fourth and final production batch of 201 aircraft built by Hawker Aircraft Ltd, Langley, Buckinghamshire. SN102-SN146, SN159-SN190, SN205-SN238, SN253-SN296, SN301-SN355. Sabre IIB engines, universal armament provision and drop tank plumbing. Deliveries commenced 1-45, completed 6-45; average rate of production approximately 9 aircraft per week. SN 368-SN416 cancelled in 1945. 

644886882_ScreenShot2018-08-16at10_05_37.png.60d02ac87517cf8ad7a2d464bd111441.png

 

IIA (modified) tempests at the start of operations

 

image.png.cd272d90077c68648e7895432882a4d4.png

 

 

821253829_ScreenShot2018-08-16at10_05_53.png.c01b638797104750c68c5b0e483c13cc.png

IIBs arrive in force

Edited by Talon_
switched images by mistake
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18 hours ago, ZachariasX said:

 

What is the date of the document?

The document was an appendix to another dated 18 September 1944, which I shall link below (note that if you click on the "Appendix "A" " it will take you to the document he linked), the stated reason to revert back to 130 in September was for logistical reasons rather than that of reliability (except for Mossie NF exhaust stacks).

http://www.wwiiaircraftperformance.org/150grade/18-sept-44-doc.html

Also, it was in September that the Tempest squadrons rejoined the 2nd TAF so they would have to have reverted to 130 anyway, at least until the 2nd TAF started to use 150 that is. They were always meant to be part of the 2nd TAF but as we know the V1 blitz got in the way.

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18 minutes ago, VO101Kurfurst said:

Do you have a reference to the modifications done at Volkel? 

I'm at work right now (and being thoroughly efficient at that), so I don't have access to all of those. There is one online (this) but how I came to the conclusion that these were the last 13, I can't remember. I can try and look in my stuff tomorrow. Had to do with the number of serviceable tempests in 122 wing during January, that's all I remember.

 

5 minutes ago, Talon_ said:

snip

While that classification seems about right, it's still a gross simplification, especially since so many modifications were done in the field.

For example, photographic evidence shows that aircrafts from all four batches were eventually able to carry the streamlined droptanks. The Series 1 and 2 thing is not very clear either, since it seems now accepted that series 1 would designate the first 30 or so aircrafts that were built using Typhoon parts (thus not sporting, for example, the same wain wing spar attachment). So giving them Hispano Vs still doesn't make series 2 aircrafts. Almost none of those were still in combat by our timeframe, though.

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Some more beef to this, here from Clostermans report to Broadhurst.

 

[...]

TRADUCTION D'UN RAPPORT D'OPÉRATIONS

 

3/12214/83 H Q./OR 17

 

from :

3.0973 Acting Squadron Leader P. N. Clostermann D. F. C. et Bar Detached from French Air Force for active service, as Officer Commanding numéro 3 (F) Squadron RAF to : ViceAir Marshall H. J. Broadhurst KBC DSO DFC. Air Officer Commanding 83 Group-II TAF H. Q. Squadron Operational Report numéro 17

[...]

 

II. Matériel.

 

L'unité est complètement rééquipée de Tempest V, type B, à moteur Sabre VI B et hélice Rotol en remplacement des types A, hélice De Havilland, depuis le 1/2/45.

 

Les performances à basse altitude et l'accélération sont nettement supérieures. Cependant il serait souhaitable d'introduire rapidement en première ligne le Tempest II à moteur Centaurus en étoile, pour les quatre raisons suivantes :

 

a) Vulnérabilité trop grande à la flak du Sabre VI refroidi par liquide.

 

b) Consommation d'huile trop élevée de ce moteur sans soupapes après trente heures de vol, ce qui réduit notre rayon d'action.

 

c) Le système de filtrage à la prise d'air des carburateurs est trop fragile, et de plus les filtres Vokes enlèvent trop de puissance pour le décollage

 

d) L'essence à 130 d'octane obligatoire pour le Sabre VI B est une source sans fin d'ennuis d'approvisionnement et d'allumage. Les manœuvres de roulement au sol sont très ralenties par le fait que les pilotes sont obligés de dégorger les moteurs toutes les minutes et avant le décollage pour éviter la formation de plomb sur les électrodes.

[...]

Clostermann, Pierre. Le Grand Cirque: Mémoires d'un pilote de chasse FFL dans la RAF (Documents (Rso)) (French Edition) (Kindle-Positionen7790-7800). Flammarion. Kindle-Version.

 

It is remarkable that Closterman is talking about the Sabre VIB in conjuction with the Rotol spinner and prop blades. He also is talking of it as the Tempest VB, surely a field label as it was given to the Spit IX LF that was called the "Spit IXB".

 

The power output at 4000 rpm he specifies either 2950 hp in case of his freshly picked up JF-E:

J'ai un des nouveaux moteurs de 2950 CV et une hélice Rotol à larges pales – ça déménage !

Clostermann, Pierre. Le Grand Cirque: Mémoires d'un pilote de chasse FFL dans la RAF (Documents (Rso)) (French Edition) (Kindle-Positionen5373-5374). Flammarion. Kindle-Version.

 

Taken together, he is officially talking about a Tempest VB, using a Sabre VIB engine with Rotol spinner and prop, delivering 2950 hp at 4000 rpm, at WEP (you had to break a wire to get that power).

 

About how the aircraft hanldes he states his opinion as the following (same report, 3/12214/83 H Q./OR 17):

[...]

Contrairement aux autres types de chasseur (P 47, P 51 ou Spitfire), les performances pratiques sont nettement plus élevées que les performances calculées. En piquant à deux degrés seulement sous l'horizon la vitesse de 700 km/h est atteinte en moins de 30 secondes. La maniabilité qui laisse à désirer en dessous de 400 km/h est remarquable au-dessus de 510 km/h. Les ailerons sont très sensibles à haute vitesse, et la souplesse de la profondeur compense une certaine instabilité longitudinale à basse vitesse. Le Tempest VB est stable en piqué rapide et offre une excellente plate-forme de tir. La puissance de feu est très grande avec quatre canons de 20 millimètres, mais ces canons Hispano type V à tube raccourci ont des enrayages trop fréquents. Une mise au point du dispositif d'alimentation est nécessaire. L'adoption du Gyro Sight VIII (Collimateur gyroscopique à correction de tir automatique) ne semble pas répondre à une nécessité urgente. De plus la visibilité en avant serait trop réduite du fait de son volume. Le personnel, peu entraîné à son emploi, l'utilise en fixe. [...]

Clostermann, Pierre. Le Grand Cirque: Mémoires d'un pilote de chasse FFL dans la RAF (Documents (Rso)) (French Edition) (Kindle-Positionen7805-7811). Flammarion. Kindle-Version.

 

In short he considers the Tempest:

  • superior in performance than P47. P51, Spitfire.
  • two degrees dive brings 700 km/h top speed within less than 30 seconds.
  • <400 km/h it doesn't handle well
  • >510 km/h it handles remarkably well
  • excellent gun platform
  • He doesn't think that it is "urgetly needed" to add a gyro sight. It would block some of the view to the front.

 

His recollection about the power output of all the Tempests he flew is not always totally consistent, but there is a pattern, he indictes power outputs as following:

  • @1000 meters, 940 hp output, two drop tanks: 580 km/h IAS
  • fast cruise: 1'625 hp output, no droptanks, 640 km/h IAS
  • top speed: +13 lbs boost, 3850 rpm, 735 km/h @ 5000 meters.
  • WEP: 3000 hp @ 4000 rpm, 780 km/h.

I think these specs, as he stated them when introducing the tempest are sort of an amalgam of both what he was used to and max. specs obtained chasing V1's. But he insists that the engine used 130 octane.

 

 

What we surely can put ad acta, is that the Sabres in service from  winter 1945 on were only rated at 2'400 hp. They worked a lot on these engines. And what was makeshift improvement (even factory side is less likely to survive in the Archive than original specs. Especially when a company folded like Napier.

 

Edited by ZachariasX
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That Sabre VI-b is most likely a typo, as there are a ton of them in that edition (I'm assuming here you have the Le grand cirque 2000 edition).

 

The Sabre VI is basically a Sabre V, but modified to be used with an annular radiator and cooling fan. It was most certainly not used in any combat operational Tempest V. The power outputs cited here are those of the Sabre VII. That one was used in the Tempest VI, which resembles a Tempest V but with the wings of the Mk II, basically.

 

Edit: On the other hand, though, some tempests (likely from the very last batch starting at SN-2XX) were delivered with a strenghthened crankshaft and the new Rotol prop. Those were indeed cleared for +13lbs boost and 3850 rpm. I've never seen power figures, or even performance figures for those, though.

Edited by Quinte
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34 minutes ago, Quinte said:

That Sabre VI-b is most likely a typo, as there are a ton of them in that edition (I'm assuming here you have the Le grand cirque 2000 edition).

Yes, that was my thought as well, they really were not very careful in editing the book. That's why I was saying it is not always consistent what is written there.

 

Although typos are one thing, general descriptions are another.

 

I very much suspect as you are saying here:

35 minutes ago, Quinte said:

Edit: On the other hand, though, some tempests (likely from the very last batch starting at SN-2XX) were delivered with a strenghthened crankshaft and the new Rotol prop. Those were indeed cleared for +13lbs boost and 3850 rpm. I've never seen power figures, or even performance figures for those, though. 

That the Rotol propeller Tempests are of this batch, effectively being Tempest VI without the wing radiator and wing carb intake. But in the cold winter 1945, cooling must have been sufficient without the added radiator. And for a makeshift solution it must have been ok. Much in contrast to flying the Middle East where Tempest VI were stationed later.

 

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=362nd_FS=RoflSeal
2 hours ago, VO101Kurfurst said:

 

Thanks for the images. There is no doubt that the Sabre IIBs were rated for +11 lbs, and as noted it was possible on even the standard 130 grade fuel. This leaves us with the question - how many Sabre IIAs and Sabre IIBs were there in operations. I understand later series of Tempest received the IIB, but how many in operations had the IIA and how many the IIB.

Numbers are irrelevant considering past and future examples of rare mods in this game.

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23 minutes ago, ZachariasX said:

that the Rotol propeller Tempests are of this batch, effectively being Tempest VI without the wing radiator and wing carb intake. But in the cold winter 1945, cooling must have been sufficient without the added radiator. And for a makeshift solution it must have been ok. Much in contrast to flying the Middle East where Tempest VI were stationed later.

 

I've assumed as much for a while, but it clearly is not as simple as that, at least when it comes to that WEP clostermann mentions.

First, not all late tempest Vs came with the rotol prop, or some had it replaced back with the DH one in the field, as photographic evidence suggests. The latter seems unlikely, so it seems Langley made them with whatever prop they had at hand.

Second, while there is very little information about a Sabre IIc, I've assumed that it was, indeed, a short-lived version of the future sabres. Some sources state it was indeed similar to the VII. And it was fitted to the Tempest V, at least for sure post-war, when converted to TT Mk5. And the  VII had a water-methanol injection system, which could have been the WEP mentionned by Clostermann... except that it was not tested before 46.

Maybe, though, the Sabre IIc was basically the Sabre Va without the wing rad and carb intake... But the Sabre Va doesn't have WEP nor the power outputs claimed by Clostermann.

 

 

All in all, it seems impossible to say what was really going on with those very late Tempest Vs. In fact I'm curious to see how they will model a "normal" Tempest, because as far as I know, there is very little serious information about its performance, outside of tests made on two aircrafts at the AFDU, which were very early production Series 1 Tempests, albeit retrofitted with a bunch of stuff as time went on, running on +9 lbs boost at best.

Edited by Quinte
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ACG_Talisman

This September 1944 extract from an Anti-Diver (150 Octane fuel) Tempest V Sqn Operations Record Book is interesting.  It shows that with Anti-Diver (V1 flying bomb) interception duties tailing off, the Sqn, as part of a whole Tempest Wing, was flying over Europe on operations.  Other missions over Europe followed, after which they were eventually transferred to 2nd TAF.

 

(To help read the text, click on it to highlight in blue and/or use the Windows magnification feature.)

 

1to10sept1944-sm.jpg

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Of the 40 Tempests lost to engine failure only one (1) was because of fire on startup.

The Typhoon and Tempest Story, Thomas/Shore

 

It does not give a reason for the e/f but some could be from enemy fire.

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11 hours ago, Talon_ said:

August 1944, Tempests modified for 150 octane fuel. This clears IIAs to +11lbs and potentially IIBs to +13lbs

 

This would explain the use of ratings higher than officially documented. If by August 1944, the engines were capable of such ratings, then it makes sense that by Winter 1945 these mdoifications were used in the "IIB" Sabres, effectively allowing +13 lbs and 4000 rpm, in cases where water/methanol injectors were installed in the last batch of Tempest V. As for the water/methanol injector, I doubt that many planes would have had them. Only some from the last batch with Rotol props, and not before March 45.

 

It really seems the Sabre VA and VII were a very gradual development from the IIB in the first half of 1945 and planes would gradually be fielded with the dernier cri, before the VA then was deemed as standard for a last batch of Napier powered Tempests. Cooling was then added, water/methanol injection removed, as it would fly great without it and there was not really a need anymore for it.

 

 

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12 hours ago, ZachariasX said:

 

This would explain the use of ratings higher than officially documented. If by August 1944, the engines were capable of such ratings, then it makes sense that by Winter 1945 these mdoifications were used in the "IIB" Sabres, effectively allowing +13 lbs and 4000 rpm, in cases where water/methanol injectors were installed in the last batch of Tempest V. As for the water/methanol injector, I doubt that many planes would have had them. Only some from the last batch with Rotol props, and not before March 45.

 

It really seems the Sabre VA and VII were a very gradual development from the IIB in the first half of 1945 and planes would gradually be fielded with the dernier cri, before the VA then was deemed as standard for a last batch of Napier powered Tempests. Cooling was then added, water/methanol injection removed, as it would fly great without it and there was not really a need anymore for it.

 

 

AFAIK Napier didn't test the Water Methanol injection before 1946, on the Sabre VII. It was not used on the Va, and certainly wasn't available during the war.

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6 hours ago, Quinte said:

AFAIK Napier didn't test the Water Methanol injection before 1946, on the Sabre VII. It was not used on the Va, and certainly wasn't available during the war.

Napier Sabre Heritage Trust goes no later than 1945 in listing all variants. They state that this injector system was developed in summer 1945, raising permissible boost to +17.5 psi with a combat rating of 3‘055 hp at 2‘240 ft. altitude.

 

I‘m really unsure about is wether the methanol injection was really deployed or not. The problem with this is that Clostermann wrote specs in his diary at a time where there the type ratings were not written up formally. It is also not clear what exactly happens when he used „surpression“ in his last batch Tempest V, a thing he wouldn‘t mention in his first ride.

 

What we do know is that at +11 psi boost and 3‘850 rpm most likely was rated maximum for „all things Napier“ in Tempests once they got reequiped in Volkel by beginning of 1945.

 

Thus I would expect the throttle and rpm just moving to this max ratings. But then, the first thing Clostermann mentioned (and he does so a couple of times) is the +13 psi boost. Now I would expect running the engine at 3‘850 rpm and +11 lbs boost, upping revs to 4‘000 would give +13 psi boost. Butthat is not how he put it. He stated +13 psi boost at the same 3‘850 rpm, *and then you could additionally up rpm to 4000*, indicating that Napier in fact did play with the gearing of the supercharger during spring 1945 already.

 

Napier goes no higher than +15 psi boost without the injector system, producing 2‘600 hp at 3‘850 rpm. In this sense, it is deabatable what „surpression“ could have meant. Clostermann described it as a „sudden, dramatic surge in power“ once you are breaking the wire. I doesn‘t sound like just being able to walk boost past +13 psi. He also doen‘t mention a boost rating in this state.

 

 

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I meant 45, not 46, so my bad. Still I'm fairly sure that those experiments (water methanol) were conducted post-war. I can't find where I read that right now, though.

 

Once again, I'm quite suspicious about Clostermann's accounts. For example he indeed claims that the whole No.3 squadron was reequipped with Rotol-prop Tempests by the 1st of February (that's before he even started flying Tempests). Yet his own log books show that this is definitely not the case.

He himself flew NV994 extensively (the majority of his victories in No.3 squadron were obtained on that crate), and that was definitely a DH prop tempest. SN222 may have had a Rotol prop, but he lost that one to (american, iirc) flak and had to belly-land it.

That's only in 3 squadron, but his previous tempests (in 56 and 274 squadrons) also sported De Havilland props (even flying older EJXXX planes).

 

In fact, photographic evidence shows that them Rotol props were quite rare. Which makes his statement unreliable, at best. In fact, even his own service dates don't match between the book and the logbooks. 

 

The conclusion to this is that there may have been some +13lbs boost tempests by the end of the war (so outside the timeframe for our campaign), but they were a minority.

For BoBp purposees it'd make sense to have two settings, +9lbs 3700rpm as an early setting (starting in mid september), and a late setting of +11lbs 3850 rpm from mid-January. An intermediary setting at +11lbs 3700rpm could also be introduced in between. That's a lot of development work, though.

 

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40 minutes ago, Quinte said:

For BoBp purposees it'd make sense to have two settings, +9lbs 3700rpm as an early setting (starting in mid september), and a late setting of +11lbs 3850 rpm from mid-January. An intermediary setting at +11lbs 3700rpm could also be introduced in between. That's a lot of development work, though.

Agree, for the game these would be the settings. Not sure an intermediate setting would make sense though, because it would be considerable additional work and there would be fewer data available to calibrate the som against. Sabre IIA and IIB specs are more at hand and less controversial. Having the IIA would certainly help getting a Typhoon at some point sooner as well.

 

Clostermanns account indeed remains enigmatic and can only serve as indication for more thorough research. But what is apparent is that toward spring they really brought along some new installations that also got conveniently swapped with material already delivered to the field. I think any aircraft with permissible ratings beyond the +11 boost was rather unique.

 

I‘ll check what photos of those Tempests I have. Should give an indication about the prevalence of Rotol props.

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VO101Kurfurst
6 hours ago, Quinte said:

 

For BoBp purposees it'd make sense to have two settings, +9lbs 3700rpm as an early setting (starting in mid september), and a late setting of +11lbs 3850 rpm from mid-January. An intermediary setting at +11lbs 3700rpm could also be introduced in between. That's a lot of development work, though.

 

 

Its quite sensible to me too, and it would be nice to see both Sabre IIA and IIB ratings for early/late or low/high if you like. Basically this would give you typical late 44 and early 45 configurations and would cover most important variants, i.e early and late batch.

 

I would leave it out the intermediate setting, that’s just a lot of work for very little difference.

 

Hisso Vs and and spring tab ailerons would be nice ideas for mods as well but we might be asking for too much.

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Mid-January seems late considering deliveries of Sabre IIB planes started in September, and the Sabre IIAs of 2TAF's Tempests had mostly been uprated back in the UK before deployment for V-1 chasing.

 

As noted above, only the first batch of 100 aircraft were without spring-tab ailerons, Hispano Vs and +11lbs.

 

Edited by Talon_
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This document was made meaningless in late September 1944 with the fitting of the four IIA upgrades, Mod No Sabre 158/297/433/435s for +11lbs on 100/130.

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5 hours ago, VO101Kurfurst said:

Hisso Vs and and spring tab ailerons would be nice ideas for mods as well but we might be asking for too much.

Hispanos V and spring tab ailerons would have been standard on all machines or close, for all our campaign.

 

4 hours ago, Talon_ said:

Mid-January seems late considering deliveries of Sabre IIB planes started in September, and the Sabre IIAs of 2TAF's Tempests had all been uprated back in the UK before deployment for V-1 chasing. 

 

September itself is pretty much irrelevant since you don't have any Tempests on the continent before the 29th. Now the uprating was for 150 octane fuel use, and was at 3700 rpm, but they didn't get that fuel in Grimbergen.

Also NVXXX aircrafts don't appear much until way later. Deliveries started in september to the RAF (GSUs), sure, but not to frontline units.

 

Edit: all in all, a late october mod for 11lbs, 3700rpm would make sense. But that's three different settings, having just two would be fine to me. Then again, in that case it is just a case of reducing power from an other setting, so why not.

 

 

Edited by Quinte
addition and typo
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Lots of Sabre IIBs to go around, like this one being fitted into a 440 Sq RCAF Typhoon in Eindhoven in 1944. There's no doubt Tempests were buzzing around with them well before Christmas.

 

https://www.pinterest.co.uk/pin/342625484142735828/

 

The modification from IIA to IIB was a new propshaft, a small metal cam and the boost control capsule. A crankshaft, a cam and a valve.

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