# Rotary or inline?



## Readie (Nov 16, 2011)

* A quick straw poll.*

If you were an aviator in WW1 would you prefer a rotary or inline engine to power your aeroplane?

I'm on the fence ( unusually ) with this one...

Cheers
John


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## FLYBOYJ (Nov 16, 2011)

Inline. When I was in A&P school we had a rotary (Gnome le Rhone). An engineering marvel but when you saw it operate and saw the amount of oil it would throw it would make you shiver!


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## Aaron Brooks Wolters (Nov 16, 2011)

Isn't a rotary different from a radial or am I mistaken? Aha, went looked. With a rotary engine, the engine case rotates around the crankshaft. With a radial engine the crankshaft is what rotates. So, I've answered my question.


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## davebender (Nov 16, 2011)

Mercedes Engine History | The Vintage Aviator
I'll take a reliable Mercedes D.III inline six over a rotary engine if given a choice.


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## nuuumannn (Nov 16, 2011)

I'll take your Mercedes D III and raise you a Rolls Royce Falcon.


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## tyrodtom (Nov 16, 2011)

They also had V-8's, the Hispano-Suiza in various models, also other manufactors made V8's also, Wolseley, Sunbeam and others. 
The Spads and SE-5 were both mostly powered by HS engines. 
I'd prefer a SE-5a with the 200hp Wolseley V8.

The rotaries used castor oil as a lubricant, mixed with the gas, like a 2 cycle. With all the oil it sent out with the exhaust, it had to be a extra fire hazard, plus we all know what swallowing castor oil will do to a person. But rotaries made very good power for their weight.


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## nuuumannn (Nov 17, 2011)

It's interesting to note that other than the Rolls engines, the British failed to produce an original in-line design that was really good. The Wolseley was essentially a Hisso built under licence but with better tolerances in manufacture, which made it more reliable. Among some of the duds were the Sunbeam Arab, again designed to substitute the Hisso V8, the Siddeley Deasy Puma, not producing anywhere near its rated horsepower, anything by Sunbeam, really - Mohawk - extensively used, but unreliable - Maori - unreliable and narrow usage. The Beardmore Galloway Atlantic - promising but overly technical and plenty of room for improvement, which led to the Siddeley Deasy Puma, hardly an improvement at all.


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## Readie (Nov 17, 2011)

_View: https://www.youtube.com/watch?v=j6PnKUEFX8g_

One of my favourite WW1 fighters is the Camel but, what a plane to learn to fly and control...jeeez.

John


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## Readie (Nov 17, 2011)

tyrodtom said:


> plus we all know what swallowing castor oil will do to a person.



Seeing the Red Baron appear out of the clouds would have a similar effect 

John


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## davebender (Nov 17, 2011)

That's one engine I don't want. Reliability was horrible. Fighting the Red Baron is bad enough. Fighting the Red Baron with a defective engine would make me wonder why I volunteered for flight training to get out of the infantry.


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## Readie (Nov 17, 2011)

The Camel turned rather slowly to the left, which resulted in a nose up attitude due to the torque of the rotary engine. But the engine torque also resulted in the ability to turn to the right in half the time of other fighters, although that resulted in more of a tendency towards a nose down attitude from the turn. Because of the faster turning capability to the right, to change heading 90° to the left, many pilots preferred to do it by turning 270° to the right.

Ummm...the line in is looking good to me. But, which one?
John


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## tyrodtom (Nov 17, 2011)

Sort of amazing that they would build over 48,000 engines and power over half of the Allied figters with them if they were "unreliable"
Granted the geared version, the HS-8Bb, did have problems with the reduction gear, but the ungeared verisions of the Hispano served well enough.

Volunteering to fly was just a good way to get out of the cold and mud, everybody at the time realized that flying was just as likely, or maybe more likely, to kill them as the trenches, flying was just a more plesant way to die.


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## davebender (Nov 17, 2011)

> Sort of amazing that they would build over 48,000 engines and power over half of the Allied figters with them if they were "unreliable"



Chauchat - Wikipedia, the free encyclopedia
It's also sort of amazing France would built 262,000 of the awful Chauchat light machineguns. Five times as many as the Lewis LMG. But they did.


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## nuuumannn (Nov 17, 2011)

tyrodtom said:


> Sort of amazing that they would build over 48,000 engines and power over half of the Allied figters with them if they were "unreliable"



Nah, they were pretty crap! Maybe that's an oversimplification. They _were_ unreliable, but the fact behind their mass use was that they had a good power to weight ratio. I've read plenty of tales of cylinders coming off in flight, glow plug lines snapping, props being shed, fuel lines being blocked. poor maintenance in the conditions at those front line airfields suffered wouldn't have helped.

An interesting thing I once heard from a (current) Camel driver; he told me that part of the reason behind the high accident rate in training whilst flying the type was because of mismanagement of the fuel system. 






Fuel pressure on the Camel was created by the little propeller driving a fuel pump; without this, the engine would stop. Failures of the mechanism were not unheard of either. He also said that he found the Camel not any more difficult to fly than other WW1 types he had flown (I can't really argue with him!). A lot of it was pure inexperience and a lack of a proper training syllabus. A bit like throwing a rookie driver who learned on a Suzuki Swift straight into an F1 car!


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## Readie (Nov 17, 2011)

_View: https://www.youtube.com/watch?v=644Ar2ZEp4A_

Ummm..get shot in the trenches or get shot in the air?

John


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## nuuumannn (Nov 17, 2011)

Nice link there John, but the history one doesn't mention that it was Australian Lawrance Hargrave who designed the rotary, he built a model driven by compressed air. The French built the first one capable of powering a full size aeroplane, but Hargrave came up with the idea first.

"Always treat your kite like you treat your woman... Get inside her five times a day and take her to heaven and back!"

Faaantastic! 

"This isn't the Women's Auxiliary Balloon Corps, your'e in the twenty Minuters' now!"

That about sums it up, really.


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## Readie (Nov 17, 2011)

Great humour. Black Adder is my favourite as it laughs at us in away that wouldn't be PC these days...

I christened the RIB coastal patrol team I was coxswain in the '20 minuters' as it was about 20 minutes before we got airborne at 35 knots in the South West approaches swells and someone landed hard on their arse 

John


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## evangilder (Nov 17, 2011)

tyrodtom said:


> Volunteering to fly was just a good way to get out of the cold and mud, everybody at the time realized that flying was just as likely, or maybe more likely, to kill them as the trenches, flying was just a more plesant way to die.



Don't know if it was a more pleasant way to go if you're on fire. They didn't wear parachutes, so if you caught fire, you would burn all the way down. 

On the engine question, I always thought it would be more of a mechanical nightmare with rotary engines versus radial. If only the crankshaft is spinning, it makes the rest of the attachments like fuel lines and plug wiring a heck of a lot easier. I'd take an inline over a rotary any day.


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## tyrodtom (Nov 18, 2011)

In the trenches they had rats, lice, cold, mud, the constant stink of death, and that was just their daily existance without the extras thrown in by combat, gas, artillery, small arms fire of all sorts, trench raids, and you could be burned to death in the trenches too, they had flame throwers in WW1 also.

If you were flying most of your time was spent in a lot more plesant surroundings, until the grim reaper made his call.

One of the memories of my boyhood was one of our local WW1 veterans, Chant Kelly. His description of living in the trenches was vivid.
He said take you average outdoor privy ( do you city boys even know what i'm talking about ?) get down in the hole, live, eat, and sleep in it for a couple of weeks, that's what the trenches were like sometimes. A level of filth and misery most modern people can't even imagine.


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## Readie (Nov 18, 2011)

We forget drowning in the first submarines or getting blown to bits in the exploding Dreadnoughts at Jutland.

RFC for me chaps.

John


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## evangilder (Nov 18, 2011)

I get where you're coming from, Tom, the wording threw my off. Aside from the unpleasantness of combat, life outside of it was cushy for the air crews.


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## nuuumannn (Nov 18, 2011)

I'm sorry, I'm going to whimp out here. UK based RNAS maritime patrol flying boat for me (Felixtowe F.2A powered by two very reliable Rolls Royce Eages), chaps! On the WEST coast!


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## davparlr (Nov 18, 2011)

I believe that the rotary was not throttleable. It was either off or on and needed to be burpped on ground maneuvers. I think I like something else.


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## tyrodtom (Nov 18, 2011)

The later war rotaries were throttleable to a small extent, like 25%. Formation flying would be about impossible otherwise.


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## evangilder (Nov 19, 2011)

From what I heard from a guy that used to the fly the Fokker DR.1 replica, the Sopwith controlled speed by "turning off and on" cylinders. I think it was with fuel flow, hence the castor oil to keep the cylinder lubricated. You would see it smoke like crazy on the lower speed passes. Here is some of the smoke.


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## FLYBOYJ (Nov 19, 2011)

I believe throttle was controlled by grounding out the magneto.


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## Readie (Nov 19, 2011)

Rotary engine control
It is often asserted that rotary engines had no carburetor and hence power could only be reduced by intermittently cutting the ignition using a "blip" or coupe momentary push-button switch, operating in a manner directly opposite that of a kill switch for other types of internal combustion engines, which grounded the magneto when pressed, shutting off power to the spark plugs and stopping ignition. However, rotaries did have a simple carburetor which combined a gasoline jet and a flap valve, or "bloctube" style throttling device, for throttling the air supply. Unlike modern carburetors, it could not keep the fuel/air ratio constant over a range of throttle openings; in use, a pilot would set the throttle to the desired setting (usually full open) then adjust the fuel/air mixture to suit using a separate "fine adjustment" lever that controlled the fuel valve.

Due to the rotary engine's large rotational inertia, it was possible to adjust the appropriate fuel/air mixture by trial and error without stalling it. After starting the engine with a known setting that allowed it to idle, the air valve was opened until maximum engine speed was obtained. Since the reverse process was more difficult, "throttling", especially when landing, was often accomplished by temporarily cutting the ignition using the blip switch.

By the middle stages of World War I, some throttling capability was found necessary to allow pilots to fly in formation, and the improved carburetors which entered use allowed a power reduction of up to 25%. The pilot would close off the air valve to the required position, then re-adjust the fuel/air mixture to suit. Experienced pilots would gently back off the fuel lever at frequent intervals to make sure that the mixture was not too rich: a too-lean mixture was preferable, since power recovery would be instant when the fuel supply was increased, whereas a too-rich mixture could take up to seven seconds to recover and could also cause fouling of spark plugs and the cylinders to cut out.

The Gnôme Monosoupape was an exception to this, since most of its air supply was taken in through the exhaust valve, and so could not be controlled via the crankcase intake. Monosoupapes therefore had a single petrol regulating control used for a limited degree of speed regulation. Early models also featured a pioneering form of variable valve timing to give greater control, but this caused the valves to burn and therefore it was abandoned.[1]

Later rotaries still used blipping the ignition for landing, and some engines were equipped with a switch that cut out only some rather than all of the cylinders to ensure that the engine kept running and did not oil up. A few 9-cylinder rotaries had this capability, typically allowing 1, 3, or 5 cylinders to be kept running.[4] Some 9-cylinder Monosoupapes had a selector switch which allowed the pilot to cut out six cylinders so that each cylinder fired only once per three engine revolutions but the engine remained in perfect balance.[5] Some documentation regarding the Fokker Eindecker shows a rotary selector switch to cut out a selected number of cylinders suggesting that German rotaries did as well.

By 1918 a Clerget handbook advised that all necessary control was to be effected using the throttle, and the engine was to be stopped and started by turning the fuel on and off. Pilots were advised to avoid use of the cut out switch as it would eventually damage the engine.[1]

The blip switch is, however, still recommended for use during landing rotary-engined aircraft in modern times as it allows pilots a more reliable, quick source of power that lends itself to modern airfields.[4] The landing procedure using a blip switch involved shutting off the fuel using the fuel lever, while leaving the blip switch on. The windmilling propeller allowed the engine to continue to spin without delivering any power as the aircraft descended. It was important to leave the blip switch on while the fuel was shut off to allow the spark plugs to continue to spark and keep them from oiling up, while the engine could easily be restarted simply by re-opening the fuel valve. If a pilot shut the engine off by holding the blip switch down without cutting off the fuel, fuel would continue to pass through the engine without combusting and raw fuel/air mix would collect in the cowling. This could cause a serious fire when the switch was released, or alternatively could cause the spark plugs to oil up and prevent the engine from restarting.

I lifted this from wiki as I couldn't find a more succint article to post.

Sounds very fiddley to control and get the best out of to me.

John


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## FLYBOYJ (Nov 19, 2011)

Good info! I believe the one at the A&P school I went to had a blip switch


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## evangilder (Nov 19, 2011)

Good stuff. Could you image trying to fly formation with one of those?!?! It's usually subtle changes to controls and throttle for formation flight. It must have been a nightmare!


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## nuuumannn (Nov 19, 2011)

Nice pic of a Camel, there, Evan. Whose? Marked as Billy Barker's famous B6313. Good info Readie; beat me to it.

Here's a quote from Gene de Marco, who regularly flies Peter Jackson's Camel:

"In order to descend you cannot simply cut the power and glide down. There are many unusual characteristics to consider. If during the descent or glide, the ignition is cut without closing the fuel valve, the chance of fire is very real. While the engine is turning it is fed fuel by a centrifugal fuel pump, this fuel, if not burned will be exhausted into the cowling. Any fuel collected in the cowling will certainly ignite when the 'blip' button is released again, bad when you are flying a wood, wire and fabric aeroplane. 

Second, the oil pump is also gear driven and is always pumping castor oil into the engine whenever it is windmilling; this may oil foul the spark plugs if they are not kept "warm" during the descent. In order to keep from "oiling up" the spark plugs, the Gnome manual says to keep the ignition turned on and reduce the fuel, this hasn't proved very effective in reality. Third, you must be extremely careful not to overspeed the engine when 'blipping' it on and off during a glide as the revs pick up quite rapidly when going downhill."

This about the notorious handling of the Camel:

" The right turn is more of a manoeuvre... the aeroplane tends to dive and roll when turned to the right under power, the gyroscopic force and large torque factor make turning power difficult to control when turning right in addition to the small rudder, cannot compensate for this gyroscopic effect. I was expecting some surprises so the first time I was rather apprehensive and experimented with different power settings and turn rates and a freshly packed parachute. I did find that a tight turn to the right under full power could not be stopped once initiated, even with full left rudder and opposite aileron; the only way was to cut the power and recover.

Straight and level flight requires some work; the pilot must constantly "blip" the engine on or off or choose a position on the selector switch that will allow the engine to run at partial power. Trim is also an issue, there is no adjustable trim tab and most of the WW1 aircraft I have flown seem to be tail heavy, requiring a substantial amount of forward stick."






Gene de Marco meets his crowd after another sortie over the Front. That's Kermit Weeks with his back turned walking toward his new Albatros in the background.


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## Readie (Nov 19, 2011)

With all this to contend with I'm surprised the Camel pilots had the time to look out for never mind engage with the Boche...

No wonder Ball preferred the SE5a

John


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## tyrodtom (Nov 19, 2011)

Ball didn't prefer the S.E.5, he preferred his Nieuport 23. 56 Squadron let Ball keep a Nieuport for his own use. He'd do squadron patrols with SE, but usually do his solo patrols with the Nieuport.


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## Readie (Nov 19, 2011)

tyrodtom said:


> Ball didn't prefer the S.E.5, he preferred his Nieuport 23. 56 Squadron let Ball keep a Nieuport for his own use. He'd do squadron patrols with SE, but usually do his solo patrols with the Nieuport.



Albert Ball - British WWI Ace
February, 1917

He returned to flying in France in February, posted to Number 56 Squadron, along James McCudden, Gerald Maxwell, Arthur Rhys-Davids, and others. Disliking the S.E.5a, the squadron's standard mount, he was allowed to fly a Nieuport on his solo patrols. Like Mannock later on, Ball became erratic. He kept killing, but became tired, shaken, and ill-tempered.

By early May, he had added eleven more victims, raising his score to forty-two, then the top Allied ace. *He reluctantly recognized that the new SE-5a was superior to the Nieuport and he made the transition.*

Tom,
You may be right but, this my understanding that Albert Ball VC (eventually) preferred the SE5a
Cheers
John


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## tyrodtom (Nov 19, 2011)

He may have been more accepting of the SE5 after some time, but he kept the Nieuport till the last. It was returned to the depot after his death.


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## davebender (Nov 19, 2011)

What happens if you are bounced by the enemy while doing all this "blipping"? You are likely to be dead before getting your engine back to full power.


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## tyrodtom (Nov 19, 2011)

When you watch them blip them on a video, it recovers in about a second, faster than giving a regular engine more throttle.

You can do the same thing with a car engine, just cut the ignition switch off for a second, and cut it back on. If you're going down the road while doing this, it'll just jerk and recover instantly. Say bye bye to your muffler if you try this though.


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## nuuumannn (Nov 20, 2011)

davebender said:


> What happens if you are bounced by the enemy while doing all this "blipping"? You are likely to be dead before getting your engine back to full power.



Pretty much, but that was the difference between an average fighter pilot and a great one; knowledge of their aircraft and its quirks would have been second nature to them, giving them enough time to think about what really mattered in such a situation, like shooting down the blighter who just shot at them. I'd imagine, like in all air to air combat, the ones having to think too much about things like engine management at crucial moments would have become toast pretty quickly.


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## tyrodtom (Nov 20, 2011)

Quirky the rotaries might have been, but the rotary engined Sopwith Camel shot down more aircraft than any other allied design.


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## Readie (Nov 20, 2011)

tyrodtom said:


> He may have been more accepting of the SE5 after some time, but he kept the Nieuport till the last. It was returned to the depot after his death.



Fair enough Tom. 

I wonder why the Camel passed Ball by? It was an effective fighter in the right hands.
Any ideas?
John


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## tyrodtom (Nov 20, 2011)

Ball was KIA in may 1917, the Camel never made it to the front till the next month.


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## Readie (Nov 20, 2011)

tyrodtom said:


> Ball was KIA in may 1917, the Camel never made it to the front till the next month.



Thanks Tom. Quite right.


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## Gixxerman (Dec 27, 2011)

Readie said:


> Seeing the Red Baron appear out of the clouds would have a similar effect
> 
> John



It's just delighful isn't it John, you get no chutes, the planes themselves (at least in the early years) are hardly sturdy designs the engines thans to the oils they use the fumes they generate encourage serious, um, 'trouser accidents'.
As Baldrick said, wars a horrid thing, ting-aling-aling.

Happy new year.


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## tyrodtom (Dec 27, 2011)

We all know what castor oil will do if you swallow a little, i'm not really sure how much you'd breath in thru the exhaust, because the exhaust would have been directed away from the pilot, but the oil to the valves was a constant loss system. So a lot of oil is going to be flying around.

But in all the reading i've done about WW1 pilots, all they'll ever say is the oil spray made them sick, and they don't get very descriptic. Maybe that generation wasn't very comfortable writing about it in explicit terms.


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## Gixxerman (Dec 27, 2011)

tyrodtom said:


> We all know what castor oil will do if you swallow a little, i'm not really sure how much you'd breath in thru the exhaust, because the exhaust would have been directed away from the pilot



It wasn't so much the exhaust I was thinking of tyrodtom, more the fumes of oils being liberally doused around a hot engine being blown back to the cockpit area.



tyrodtom said:


> But in all the reading i've done about WW1 pilots, all they'll ever say is the oil spray made them sick, and they don't get very descriptic. Maybe that generation wasn't very comfortable writing about it in explicit terms.



I think you have something there I agree.


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## tyrodtom (Dec 27, 2011)

Speaking of parachutes in WW1. The Germans has no reservations about their pilots using them when they were finally reduced in size enough to be practical for aircraft.

Ernst Udet was saved by a parachute after a midair collision with a French aircraft.


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## Readie (Dec 28, 2011)

tyrodtom said:


> We all know what castor oil will do if you swallow a little, i'm not really sure how much you'd breath in thru the exhaust, but the oil to the valves was a constant loss system. So a lot of oil is going to be flying around



Shades of my Triumphs BSA bikes....good for the soul 

John


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## Gixxerman (Dec 28, 2011)

John, I remember that smell vey well.....I recall the older classic bikes and racing bikes using it, glad I didn't get too close too often now that mention has been made of the possibilities of 'explosive dire-rear' coming from the fumes.
Eeek!


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