A very interesting topic. If you search for blipping in theaerodrome forums, you'll find a lot of info on the subject. I have not seen any reference to using the blip switch during a patrol or combat, and read that most early war pilots seem to have relied on just a couple of settings: idling, and full speed (as mentioned below). However, maybe someone has a reliable source which states otherwise.
A couple of interesting posts on the aerodrome....
"This is a big topic, and not without controversy, so you might want to search the forum for "Monosoupape" (note the spelling); but briefly, here goes:
Like most internal combustion engines the rotary engine was controlled by adjusting the flow of fuel and air into the cylinders. Loosely speaking, if you let in more fuel, the engine runs faster.
In most rotaries (including the early, pre-Monosoupape Gnomes) this was done by giving the pilot two control levers, one for the petrol and one for the air, which altered the flow into the carburettor (which the engine certainly did have). The "throttle" is the air lever. In theory you could adjust the positions of the levers to give a range of engine speeds. In practice this was tricky to achieve, for several reasons, and most pilots seem to have relied on just a couple of settings: idling, and full speed. Pilots were taught to land with the fuel supply cut off completely, because it was much too difficult to land in the modern way, with the engine running but constantly adjusted.
The Monosoupape was (partly) an attempt to make all this simpler by giving the pilot just one lever, to control the petrol. The air flow was effectively fixed. Unfortunately, because of the way a rotary works, this made it difficult to achieve any setting other than full speed.
The purpose of the blip switch was to cut off the electricity to the ignition system, which of course stops the engine from firing. It suffered from several disadvantages. The switch itself was not always reliable (as Cecil Lewis, for one, found out the hard way) and could give you an electric shock. Its use was regarded in some circles as unprofessional. It was strongly discouraged while in flight, because the propellor would continue to windmill round, and the engine would therefore keep sucking in oil, petrol and air, and blowing the unburned mixture out of the exhuast valves. This could lead to oil deposits fouling the spark plugs, which then might not work when you released the blip switch; while a build-up of unburned mixture under the engine cowling could start a fire.
For all these reasons the blip switch was mainly used to keep the speed down while taxying. This is said to produce a characteristic on-off engine noise. However, it is also the case that an idling rotary may misfire on some cylinders, producing a similar sort of noise.
This lack of control was not seen as a problem in the heyday of the Mono engine (say, 1914-16) because formation flying (which requires constant small adjustments to the engine speed) was not much practised. When formation flying became essential, engine design changed. Later rotaries often had adjustable ignition systems, enabling the pilot to select the number of cylinders that would fire, and hence to control the engine speed. They also seem to have been better tuned to allow a range of fuel-air settings to be found, at least while you were airborne and well away from the ground."
and from our own Bletchley says:
"If you use the 'Search' function you will find that there has been a great deal written here about rotary engine throttles and engine control. I think the 'blip' switch was mostly meant to be used on the ground, for taxiing the aircraft - although, as others have said, it could also be used on the final approach. WWI Pilots were taught to land most rotary engined aircraft by switching off the supply of fuel to the engine at the fuel-cock, and then gliding in. If they had misjudged the landing, the engine could quickly be brought back to life by switching the fuel supply back on. Using the 'blip' switch when the engine was running at full power was officially discouraged, on all but the early Gnome rotaries, as the alternating surge and drop in power could damage the engine and, if held down too long, could flood the engine with unburnt fuel that could cause a fire beneath the cowling when the 'blip' was released. The correct procedure was, in most cases, to throttle the engine back to a near idle setting before using the 'blip' switch. The 'blip' switch was necessary because nearly all rotary engines had an unusualy high 'idle' speed of around 800 rpm in the air (less, maybe 500 or 600 rpm on the ground), so they could not be fully throttled back in the same way as a stationary engine without risk of killing the engine. Here are some training notes by Lt. Leighton from 1917:
Sopwith Pup (80 hp Le Rhone)
Engine controls:-
1. Petrol Main Tap
2. Petrol Fine Adjustment Lever
3. Throttle Lever
"The engine must be throttled down to 950 rpm when the scout will fly at 60, 70 or 80 mph. To make certain of having engine on landing, the throttle and petrol should be closed as far back as possible but with the engine running smoothly, then the switch may be used. It is safer to use the main switch until one has become quite accustomed to the machine, as one's thumb is liable to slip off the thumb switch button... Glide down at 65 mph, flatten out and float along as close to the ground as possible, just holding the machine off and doing so as long as possible."
Sopwith Strutter (110 hp Clerget)
Controls, as above.
To taxi out: try and taxi out on throttle using the switch as little as possible. Always remember to cut down your fine adjustment when you throttle down.
To land: shut off your engine. If above 500 ft. turn your petrol off and leave switch on. If at 500 ft. turn petrol on and switch off. Coming down from a good height, try engine occasionally. Watch your pressure when engine is shut off. Pull your empennage wheel back to come down at 65 mph. At first come in straight until you can do 'S' turns. Allow yourself plenty of room to land in case you come in too fast..."
Note: the reference to 'main switch' is, I think, to the magneto switch, the 'blip' switch being referred to here as the 'thumb switch'.
Bletchley"
