The SE5: Engine Troubles and Myth-Busting

[No.23_Starling]

Salute pilot friends,

 

Being the cool guy that I am, I've been reading every book and source I can get my hands on surrounding the SE5a and its various engines - I've provided a full list of these below as recorded by Sturtivant and Page. Some of the books give part of the story, and some of them are simply inaccurate. What I've tried to do is look at the test data we have, then tie that back to the engineering and science to provide some kind of explanation.

 

1917's SE5a

The first thing to note here is that only 5 squadrons had the type by the end of 1917 (see below), making it uncommon but likely more established on the lines than the Dr1. This version had the 200hp French-made HS8B engine, a geared version known to be problematic due to gear breakdowns, or if they were very unlucky one of the British variants. It also drove a 4 bladed prop as seen in many photos. There have been community suggestions that the 4 bladed prop and geared engine somehow made this version slower than the Viper version and a better turner - the data on speed does not concur, and the engineering does not make sense here either. Both the French-made HS8B and the Viper produce 200hp, both use the same airframe, and both have similar loaded weights. Likewise, we have no evidence to suggest substantial differences in prop pitch between the 4-bladed version and 2-bladed; the prop transfers the power of the engine to the air, and the pitch would have more of an impact on turn performance than the number of blades. The only reference to performance difference on the prop variants is in Alex Revell's High in the Empty Blue, where pilots noted more issues with torque using the 4 bladed version. I'm sure @Holtzauge can give more on the engineering behind this.

 

In terms of speed and climb, the test data I have (see below, used by AnP for the RoF model) suggests that the 200hp French-made HS8B version actually outperforms or matches the Viper version, which makes sense given that both output the same HP and are similar in weight. I can find no evidence either from the engineering side, or contemporary sources that point to a 'turning' SE5a in 1917, and having the 'Viper' SE5a in 1917 maps is an issue more on its rarity than performance.

 

Early 1918 SE5as

This is where it gets messy. The HS8B engine was a big issue for the British (and French) due to the gearing which broke constantly. Likewise, the 8B engines being built on license in France went first to the SPADs of the French not to the British. Attempts to build an English HS8B engine produced poor results, and the test data for these show a much reduced performance (see data below). We also know from sources that eventually the British just stuck whatever engine they could find into SE5a airframes, resulting in a mess of performance and quality.

 

In early 1918 the French were busy upgrading their SPAD XIIIs to high compression, and ace James McCudden decided he didn't want to wait in line to get his high compression pistons. Christopher Cole in McCudden VC notes how the upgraded 220hp French engine provided additional climb and ceiling to reach the German Rumplers above 20k feet - this must have been true as he added a number of these to his tally thereafter.

 

From an engineering perspective, the SE5as lucky enough to have an upgraded 220hp French-made HS8Bc should have been the best performing version of the war, however I cannot find any test data for this version to substantiate this assertion.

 

Viper SE5a

Most people dont seem to realise that the Viper was an upgraded HS8A engine, fitted to the SPAD VII and earlier SE5, created by Wolseley when they accidentally received a shipment of the older 150hp in error. Through some tinkering they managed to get 200hp out of her (compression ratio increase, balanced crankshaft, transverse magnetos - see Alec Lumsden, British Piston Aero-Engines and Their Aircraft) keeping the benefit and ease of direct drive. 

 

What made this engine so successful was simply the fact that it was direct drive (no more gearing breakages), it matched the French-made HS8B 200hp engine or thereabouts in performance (see data below), and could be made in numbers to be fitted to the awaiting empty airframes. Where confusion seems to occur however is around the Viper somehow providing better performance than the HS8B 200hp engine. Jon Guttman in SE5a vs Albatros DVa writes that the new Viper gave an extra "7mph and improved rate of climb"; I think Jon has been a bit misleading here as he gives data for A4845 as being an SE5 without saying if it's the 200hp or 150hp, whereas other sources have this as an early SE5 with the 150hp engine tested in March 1917 (see below) - of course it would be faster than the 150hp version! With the same power output and loaded weights I cant see how it gave better performance.

 

 

I conclude thus:

1. There's no evidence for a 'turning' SE5a in 1917, just a 200hp version with an unreliable gearing system. The SE5a likely turned just fine vs most German opponents - I suggest reading @Holtzauge's book on this point if you want to understand the science

2. The engines were a mess in early 1918 as Wolseley struggled with their 200hp HS8B clones, and the French wouldn't provide the British with enough of their own HS8Bs

3. The definitive SE5a for speed, climb, and turn, should have been the HS8Bc 220hp engine, as used by McCudden and fitted to the SPAD XIII

4. The Viper SE5a didn't perform much better than the HS8B version; it was a breakthrough because it was direct-drive (didn't break all the bloody time) and could be produced in numbers to help mass produce the SE5a in the summer of 1918.

 

Salute all! Let me know if I've made any mistakes etc.

 

 

S.E.5/5A Engines (from the The S.E.5 File by Sturtivant and Page).

 

Non-geared engines.

 

    150 hp Hispano-Suiza 8Aa (low-compression, non-geared)

    150 hp Wolseley Python I (license version, as above)

    200 hp Hispano-Suiza 8Ab (high-compression, non-geared)

    180 hp Wolseley Python II (license version, as above)

    200 hp Wolseley W.4A Viper (high-compression, non-geared, comparable with 220:240 hp geared versions but somewhat different design by Wolseley)

 

Geared engines.

    200 hp Hispano-Suiza 8Bd

    200 hp Hispano-Suiza 8BCa

    200 hp Hispano-Suiza 8BCb

    200 hp Hispano-Suiza 8BDa

    200 hp Hispano-Suiza 8BDd

    200 hp Hispano-Suiza 8BEa

    200 hp Hispano-Suiza 8BEb

    220 hp Hispano-Suiza 8Bc

    220 hp Hispano-Suiza 8Be

    200 hp Wolseley Adder I (1170 rpm)

    200 hp Wolseley Adder II (1170 rpm)

    200 hp Wolseley Adder III (1170 rpm)

    200 hp Sunbeam Arab I (different design, test installation only)

    200 hp Sunbeam Arab II (different design, test installation only)

 

 

 

 

 

 

Edited March 22, 2023 by US103_Rummell

[ST_Catchov]

14 hours ago, US103_Rummell said:

The SE5a likely turned just fine vs most German opponents - I suggest reading @Holtzauge's book on this point if you want to understand the science

 

You knew I'd ask this didn't you Rummy! ? Does the book shed any light on the accuracy of the energy loss issues as exhibited by FC's Se5a Viper? 

 

But only if it's okay with Holtzy. ?

 

14 hours ago, US103_Rummell said:

Being the cool guy that I am

 

There's not many of us left.

[No.23_Starling]

1 hour ago, ST_Catchov said:

 

You knew I'd ask this didn't you Rummy! ? Does the book shed any light on the accuracy of the energy loss issues as exhibited by FC's Se5a Viper? 

 

But only if it's okay with Holtzy. ?

 

 

There's not many of us left.

It examines sustained and instantaneous turn performance. The energy loss / retention of some of the German scouts is part of the reason the in-game SE5a is a terrible dogfighter - he also looks at zoom.

 

I think you’d really enjoy it.

[Holtzauge]

1 hour ago, ST_Catchov said:

 

You knew I'd ask this didn't you Rummy! ? Does the book shed any light on the accuracy of the energy loss issues as exhibited by FC's Se5a Viper? 

 

But only if it's okay with Holtzy. ?

 

 

About energy retention: The testing done so far comparing sustained turns at higher altitude (5km) suggest that FC is being quite optimistic for most aircraft (as in the turn times in-game are shorter than in the book) with two exceptions:

 

The Nieuport N.28 and.........drumroll........

 

The S.E.5a!

 

Speaking about the book Catchov: Why be such a cheapskate?  Buy one! It all goes to a good cause: Stocking up my wine cellar! 

 

17 minutes ago, US103_Rummell said:

I think you’d really enjoy it.

 

This!

[ST_Catchov]

1 hour ago, Holtzauge said:

About energy retention: The testing done so far comparing sustained turns at higher altitude (5km) suggest that FC is being quite optimistic for most aircraft (as in the turn times in-game are shorter than in the book) with two exceptions:

 

The Nieuport N.28 and.........drumroll........

 

The S.E.5a!

 

Hmm interesting .... and a conundrum.

 

2 hours ago, Holtzauge said:

Speaking about the book Catchov: Why be such a cheapskate?  Buy one! It all goes to a good cause: Stocking up my wine cellar! 

 

I can't help being cheap! I've spent a fortune on shrinks. But I'm considering ....

[US103_Baer]

On 3/23/2023 at 7:38 PM, ST_Catchov said:

 

Hmm interesting .... and a conundrum.

 

 

I can't help being cheap! I've spent a fortune on shrinks. But I'm considering ....

Highly recommend the book Catchov. It's a reference you'll keeping coming back to.

 

 

[FuriousMeow]

I assume you all, or some of you, were around in the RoF days? If you'll remember there was that final patch that did some "things" to several planes. The Camel, for example, had its engine replaced with a sewing machine and the Albatros series were given some very optimistic turn rates. Prior to that the Se5a was fairly competitive with the Albs. There were other planes that were randomly changed. The basis for these changes have always irked me, but I'll leave that off the forums.

[ST_Catchov]

4 hours ago, US103_Baer said:

Highly recommend the book Catchov. It's a reference you'll keeping coming back to.

 

I've considered it and it's probably too technical for me to really enjoy. But I wish @Holtzauge all the best with sales as he's a nice guy and really deserves some reward for the major effort put into it.

 

My greater interest is whether the devs utilise the technical information in the book to correct the flaws in various FC flight models?

[Holtzauge]

8 hours ago, FuriousMeow said:

I assume you all, or some of you, were around in the RoF days? If you'll remember there was that final patch that did some "things" to several planes. The Camel, for example, had its engine replaced with a sewing machine and the Albatros series were given some very optimistic turn rates. Prior to that the Se5a was fairly competitive with the Albs. There were other planes that were randomly changed. The basis for these changes have always irked me, but I'll leave that off the forums.

 

I was a late joiner to WW1 sims and only bought RoF after that patch so have only heard about how the planes behaved before that. IIRC then things were done to the Camel’s and Dr.I’s speed and Sopwith Triplane’s turn performance? But that the Albatros’ turn performance was tuned up at the same time was news to me. I always thought that the reason the Albatros was turning so well in-game was due to it being one of the first planes introduced and that FM’s at the time was very much work in progress. Because based on the physics of the plane, it has very few features that would suggest it as a good turner. And with the un-compressed Mercedes D.IIIa engine we have in-game, its specs suggest that it should be a dog both in terms of climb, ceiling and turn performance. A D.IIIaü engine would of course change things, but that is not what we have in-game.

 

5 hours ago, ST_Catchov said:

 

I've considered it and it's probably too technical for me to really enjoy. But I wish @Holtzauge all the best with sales as he's a nice guy and really deserves some reward for the major effort put into it.

 

My greater interest is whether the devs utilise the technical information in the book to correct the flaws in various FC flight models?

 

Thank you for those kind words Catchov! And I too really hope the devs will find the book interesting and will want to engage in discussions around possible performance tuning activities.

 

 

Edited March 26, 2023 by Holtzauge

[1PL-Husar-1Esk]

3 hours ago, Holtzauge said:

I was a late joiner to WW1 sims and only bought RoF after that patch so have only heard about how the planes behaved before that. IIRC then things were done to the Camel’s and Dr.I’s speed and Sopwith Triplane’s turn performance? But that the Albatros’ turn performance was tuned up at the same time was news to me. I always thought that the reason the Albatros was turning so well in-game was due to it being one of the first planes introduced and that FM’s at the time was very much work in progress. Because based on the physics of the plane, it has very few features that would suggest it as a good turner. And with the un-compressed Mercedes D.IIIa engine we have in-game, its specs suggest that it should be a dog both in terms of climb, ceiling and turn performance. A D.IIIaü engine would of course change things, but that is not what we have in-game.

If i remember correctly, Alb just got higher level speed. 

 

it's good that after those years devs admitted that december 2014 patch was a mistake (Petrovich post). That's why they ported FMs to FC as they were before that patch. Unfortunetly they realised this  too late, after 2 FMs were allready ported (Spad 13 and Dr.1) , Spad was not affected by december patch but Dr.1 was , so only Dr.1 FMs is nerfed in FC.

 

This Dr.1 nerf - weaker engine (lower level speed) give him ability to turn tight  (just turn with max elevator pull to the bely ) and do not worry about G.  

 

BTW what do you think about that when most central planes can be turrned with max elevator pull and  air streams do not break off, how that even be possible in real life without violent accelarated stall ? As the airscrew were generating enough thrust to compensate violent stall and make control surfaces be effective enough.

Edited March 26, 2023 by 1PL-Husar-1Esk

[Holtzauge]

2 hours ago, 1PL-Husar-1Esk said:

If i remember correctly, Alb just got higher level speed. 

 

it's good that after those years devs admitted that december 2014 patch was a mistake (Petrovich post). That's why they ported FMs to FC as they were before that patch. Unfortunetly they realised this  too late, after 2 FMs were allready ported (Spad 13 and Dr.1) , Spad was not affected by december patch but Dr.1 was , so only Dr.1 FMs is nerfed in FC.

 

This Dr.1 nerf - weaker engine (lower level speed) give him ability to turn tight  (just turn with max elevator pull to the bely ) and do not worry about G.  

 

BTW what do you think about that when most central planes can be turrned with max elevator pull and  air streams do not break off, how that even be possible in real life without violent accelarated stall ? As the airscrew were generating enough thrust to compensate violent stall and make control surfaces be effective enough.

 

I only model performance so control authority is not something I could say anything about. But given how unstable most WW1 aircraft are, I would have expected that there was plenty of up-elevator available even at stall. Given that he has flown a lot of WW1 birds, maybe @Chill31 can enlighten us?

 

About the Albatros D.Va turn: OK thanks for the info. But whenever the turn capability was tuned in there, I have a hard time seeing that it’s not overperforming as it is now with the D.IIIa engine it has modeled.

 

About the Dr.I’s turn: Both it and the Camel are turning very much better in-game than my estimates. The difference is especially large at 5 km altitude where the in-game turn time is only 60-70% of what I estimate on pages 187-188 in my book.

 

Edited March 26, 2023 by Holtzauge

[1PL-Husar-1Esk]

35 minutes ago, Holtzauge said:

he difference is especially large at 5 km altitude where the in-game turn time is only 60-70% of what I estimate

Seldom we fight at that high altitude especially using rotaries, but if in game prediction model to calculate turn performance  produced this is off  high altitude results   it also must be off in lower altitudes (but the difference is not so noticeable) I presume ?

[FuriousMeow]

The Alb turn was indeed tuned, I remember them specifically getting better in turn fights after that patch. Speed alone wouldn't have done that. 

[Holtzauge]

The differences are smaller at lower altitudes (maybe 80 instead of 60% for the Camel & Dr.I) but the main issue I think is how the other aircraft like the Albatros, Nieuport and S.E.5a stack in relation to each other in terms of turn performance which affects all altitudes.

 

[ZachariasX]

I think the drag penalty at higher AoA (and induced drag in general) are modelled somewhat tame in FC and especially conservative in RoF. IMHO, it was basically "missing" induced drag (and airframe drag at high AoA) that lead tho ThePatch™, because it made some aircraft incredible clown cars, maintaining all their energy while doing the wildest maneuvers. In consequence they were able to do things that are way beyond any real possibilities of those crates. Correcting such with performance penalties of course led to the controversal results we had back then.

 

Still, I find low speed drag penalty very benign. It is where I see the main cause from the FC performance figures deviating @Holtzauge's results. This not just through performance hits, but by little effects on control authority.

Edited March 27, 2023 by ZachariasX
bloody typos

[Holtzauge]

Yes, the induced drag is a big contributor to the differences I think. In addition maybe engine power/thrust at higher altitudes. Granted, I think very few of us spend times at really high altitudes in-game to notice, but I seriously doubt the Fokker D.VIIF had a ceiling as high as 9000 m IRL.

 

[No.23_Starling]

16 hours ago, Holtzauge said:

Yes, the induced drag is a big contributor to the differences I think. In addition maybe engine power/thrust at higher altitudes. Granted, I think very few of us spend times at really high altitudes in-game to notice, but I seriously doubt the Fokker D.VIIF had a ceiling as high as 9000 m IRL.

 

I was involved in combats last night at 16k feet and there were DVIIFs easily sailing over me a couple more thousand up. It’s getting more common now on a Sunday night where you’ll mostly see DVIIs and DXIIs.

18 hours ago, 1PL-Husar-1Esk said:

Seldom we fight at that high altitude especially using rotaries, but if in game prediction model to calculate turn performance  produced this is off  high altitude results   it also must be off in lower altitudes (but the difference is not so noticeable) I presume ?

If you read @Holtzauge’s book you’ll see that there are still issues plaguing the N28 etc down low. Turn performance between a lot of the plane set gets even closer at SL as the higher compression alt engines lose their advantage.

[Chill31]

On 3/26/2023 at 10:04 AM, Holtzauge said:

 

I only model performance so control authority is not something I could say anything about. But given how unstable most WW1 aircraft are, I would have expected that there was plenty of up-elevator available even at stall. Given that he has flown a lot of WW1 birds, maybe @Chill31 can enlighten us?

 

@1PL-Husar-1Esk I think the question is: do WWI airplanes have enough control authority to make it have accelerated stall in turns?

 

Yes, BUT it depends on how the turn is done. A clmibing or level turn is much easier to achieve an accelerated stall. The Dr.I will not accelerated stall in a descending turn.  It does get extreme drag with full aft stick, but it is controllable the whole time.

 

The Camel will achieve an accelerated stall, but it is not violent. I could hold full aft stick and the nose would bounce from stall to stall. When the Camel stalls, those stops tracking. When the nose stops, it accelerates out of the stall and starts tracking until it stalls again.  

 

WWI planes do not have ceazy violent stalls, but some are far more gentle (think Fokker) than others.

[Holtzauge]

@Chill31: IIRC then Javier Arango said much the same thing about the Camel ailerons: They are neither very effective and have huge control forces. How does the Dr.I behave? Can you give us a rough idea about how control forces rise with IAS? In the other thread you said about two hands are needed on the Camel at 110 mph. What about the Dr.I at that speed?. And what about higher speeds still? Say in a dive going 125-150 mph?

[No.23_Starling]

Hi all, a few questions for you all further to the post above. I found a photo from an auction for a Wolseley Viper showing the counterweights on the crankshaft which contributed to its performance whilst adding 18kg in additional weight. They are likely the blocks opposite the piston connection:

 

 

According to Manuel Lage, Hispano Suiza in Aeronautics, this fixed an issue with the license built Wolseley 8A/B engines with broken crankshafts, but I can also see how it helped to improve engine efficiency.

My first question to you all is how the transverse magnetos, oil pressure regulating value, and oil dry sump added to the available HP?

 

Second question is why did Hispano Suiza wait until 1919 before incorporating these improvements to the old 8A engine (named type 41) in their SPAD VIIs to get the 200hp+ if the British were using it in numbers by summer 1918? Is there evidence of it appearing in the SPAD VII in 1918 that anyone has seen?

 

@ZachariasX @Holtzauge any ideas on either?

 

From Lage’s book:

 

 

Edited February 5, 2024 by No.23_Starling

[Holtzauge]

@No.23_Starling: I'm guessing the boost in power comes from the increase in compression ratio from 4.7 to 5.3. The other stuff, the redesign of "the transverse magnetos, oil pressure regulating value, and oil dry sump" were probably good additions as such but the added power output is most likely due to the increase in compression ratio, just as it was for the Mercedes DIII series.

 

BTW: What happened to Rummel? Has he transformed into a Starling? 

[No.23_Starling]

3 hours ago, Holtzauge said:

@No.23_Starling: I'm guessing the boost in power comes from the increase in compression ratio from 4.7 to 5.3. The other stuff, the redesign of "the transverse magnetos, oil pressure regulating value, and oil dry sump" were probably good additions as such but the added power output is most likely due to the increase in compression ratio, just as it was for the Mercedes DIII series.

 

BTW: What happened to Rummel? Has he transformed into a Starling? 

Rummel has joined the RFC ?

 

The compression ratio can’t be the full story as that was essentially the Wolseley Python II engine listed above (the same as the SPAD VII 180hp 8A engine).

 

The counterweights and other modifications must have been responsible for the extra 20hp, and these were also included in the Type 41 engine developed by Hispano in 1919 (see above). I’m assuming the counterweights could have allowed for more efficient transfer of power to the prop due to reduced vibrations? I don’t see how the magnetos or oil system could have increased power other than the latter reducing engine wear and potentially allowing for higher RPM.

Edited February 6, 2024 by No.23_Starling