Sopwith Triplane mishap at Old Warden today
Its very unlikely that the AAIB would investigate an incident such as this.
What they are very unlikely to do is to conduct a field investigation with all that that entails.
W8 - partly true. If anyone actually took the time to watch the youtube video I linked to earlier, the mishap pilot himself describes the way rotary engines are controlled for landing and mentions the Sopwith Triplane.
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Is it not possible to idle a rotary?
A rotary behaves rather like a simple model glo-plug engine in that it either runs or it doesn't according to mixture. There's no throttle, it's either on or off.
Due to the considerable inertia of that big wooden prop and several cylinders plus crankcase all whirling round it has huge inertia so stopping the combustion does little to slow the rotation.
There are two ways of robbing a rotary of it's 100% power, either shut the fuel (lever) off or cut the magneto (blip switch). Thus to achieve an average power level between 100% or more than zero the pilot needs to modulate the engine between "off" and "100%" by means of either the fuel lever or the magneto switch.
Hence "blipping". I assume one sets up a high approach with the engine inhibited - i.e. dead via the blip switch or fuel control at "off", which approach is reduced by the characteristic sideslip but interspersed with a burst of engine (by necessity at 100% intermittently - or as soon after restoration of sparks or fuel the damn thing chooses to respond) Watch videos of rotaries taxying - blaaaa! pause - Blaaa! pause, Blaaaa!
It's a pretty blunt way of controlling power by today's standards and as described in the video above each individual engine seems to have it's own way of responding - or not - or maybe.
Even so, smoke and engine noise on short finals shows that the engine is trying to light up again if not actually giving its all just yet.
It is a two-stroke after all. If it is running it'll smoke like hell - and smell like Heaven, of course!
Do the Tiger Club have their Stampes still? They were fitted with a basic "injector" fuel system that was allegedly based on Sir William Cobham's full inverted system (1920's) , derived from a rotary set-up using a fuel lever and an air lever only. You changed over from the nice but blue-side-up only carburettor to this devious two lever contraption that just gave you engine on or off - and then only if you had fuel and air levers precisely balanced (fugall power if you didn't) , tho regardless of attitude which made the Stampe nicely aerobatic. Still, it sure was a bit of a blunt instrument and one that astonishingly had lasted well into the late '80s when I last saw it. It impressed the heck out of me, I can tell you!
Magenta Line it isn't!
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Although a conventional carburetor, with the ability to keep the fuel/air ratio constant over a range of throttle openings was precluded by the spinning cylinder block, it was possible to adjust the air supply through a separate flap valve or "bloctube". The pilot needed to set the throttle to the desired setting (usually full open) and then adjust the fuel/air mixture to suit using a separate "fine adjustment" lever that controlled the air supply 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, although this varied between different types of engine, and in any case it required a good deal of practice to acquire the necessary "knack". After starting the engine with a known setting that allowed it to idle, the air valve was opened until maximum engine speed was obtained.
Throttling a running engine back to reduce revs was possible by closing off the fuel valve to the required position while re-adjusting the fuel/air mixture to suit. This process was also tricky, so that "throttling back", especially when landing, was often accomplished by intermittently cutting the ignition using the blip switch.
Cutting cylinders using ignition switches had the drawback of letting fuel continue to pass through the engine, oiling up the spark plugs and preventing the engine from restarting. Also, the raw oil-fuel mix could collect in the cowling. As this could cause a serious fire when the switch was released, it became common practice for part or all of the bottom of the basically circular cowling on most rotary engines to be cut away, or fitted with drainage slots.
By 1918 a Clerget handbook advised maintaining all necessary control by using the fuel and air controls, and starting and stopping the engine by turning the fuel on and off. The recommended landing procedure involved shutting off the fuel using the fuel lever, while leaving the blip switch on. The windmilling propeller made the engine continue to spin without delivering any power as the aircraft descended. It was important to leave the ignition on to allow the spark plugs to continue to spark and keep them from oiling up, so that the engine could (if all went well) be restarted simply by re-opening the fuel valve. Pilots were advised to not use an ignition cut out switch, as it would eventually damage the engine.
Pilots of surviving or reproduction aircraft fitted with rotary engines still find, however, that the blip switch is useful while landing, as it provides a more reliable, quicker way to initiate power if needed, rather than risk a sudden engine stall, or failure of a windmilling engine to restart at the worst possible moment.
Rotary engine - Wikipedia, the free encyclopedia
Four stroke Agaricus. The lubrication is a total loss system (castor oil) as with a two stroke, which may be the source of confusion.
Throttling a running engine back to reduce revs was possible by closing off the fuel valve to the required position while re-adjusting the fuel/air mixture to suit. This process was also tricky, so that "throttling back", especially when landing, was often accomplished by intermittently cutting the ignition using the blip switch.
Cutting cylinders using ignition switches had the drawback of letting fuel continue to pass through the engine, oiling up the spark plugs and preventing the engine from restarting. Also, the raw oil-fuel mix could collect in the cowling. As this could cause a serious fire when the switch was released, it became common practice for part or all of the bottom of the basically circular cowling on most rotary engines to be cut away, or fitted with drainage slots.
By 1918 a Clerget handbook advised maintaining all necessary control by using the fuel and air controls, and starting and stopping the engine by turning the fuel on and off. The recommended landing procedure involved shutting off the fuel using the fuel lever, while leaving the blip switch on. The windmilling propeller made the engine continue to spin without delivering any power as the aircraft descended. It was important to leave the ignition on to allow the spark plugs to continue to spark and keep them from oiling up, so that the engine could (if all went well) be restarted simply by re-opening the fuel valve. Pilots were advised to not use an ignition cut out switch, as it would eventually damage the engine.
Pilots of surviving or reproduction aircraft fitted with rotary engines still find, however, that the blip switch is useful while landing, as it provides a more reliable, quicker way to initiate power if needed, rather than risk a sudden engine stall, or failure of a windmilling engine to restart at the worst possible moment.
Rotary engine - Wikipedia, the free encyclopedia
It is a two-stroke after all
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By 1918 a Clerget handbook advised maintaining all necessary control by using the fuel and air controls, and starting and stopping the engine by turning the fuel on and off. The recommended landing procedure involved shutting off the fuel using the fuel lever, while leaving the blip switch on. The windmilling propeller made the engine continue to spin without delivering any power as the aircraft descended. It was important to leave the ignition on to allow the spark plugs to continue to spark and keep them from oiling up, so that the engine could (if all went well) be restarted simply by re-opening the fuel valve. Pilots were advised to not use an ignition cut out switch, as it would eventually damage the engine.
On the Shuttelworth aircraft, as it was on approach, the blue smoke points directly to 'blipping' just as it should - but sadly the port wheel struck the top of a post as I saw it. The rest was almost inevitable due to weight and forward speed. The reason will be heard in due time.
As always, it is good to hear the pilot was OK.
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of course the very low approach speeds of any WWI aircraft make a big difference when it all goes pear shaped - another 10 mph and he'd have turned right over - another 20 and it might have been a full on cartwheel
I never understood how many aviation pioneers walked repeatedly walked away from crashes until I realised the speeds they were flying at..........
I never understood how many aviation pioneers walked repeatedly walked away from crashes until I realised the speeds they were flying at..........
