Rotary or inline?

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.

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!

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.

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

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.

I believe throttle was controlled by grounding out the magneto.

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

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

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!

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.

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

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.

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.

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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

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.

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.

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.

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.

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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.

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

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.

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Fair enough Tom.

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

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