AK1-3 Helicopter ENGINE
Posted by Charles D'Alberto
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| Posted by Charles D'Alberto |
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| Posted by Charles D'Alberto |
The AK1-3 is powered by the proven and extremely reliable Subaru EJ 25 motorcar engine.
The Subaru engines (all brand new units) use the mechanical / cable throttle control system, instead of the "electronic fly- by-wire" throttle control. The engine is a water cooled flat four cylinder, (Boxer) with fuel injection, single overhead camshaft, four valves per cylinder and solid state electronic ignition and duel fuel pumps. The engine's bore to stroke dimensions are over-square at 99.5 mm by 81 mm. This over-square characteristic typically allows engines to operate at higher rpm more easily without overstressing, and also enables the use of larger inlet and exhaust valves, thus allowing easier engine breathing at higher rpm. The engine is very smooth indeed at all engine speeds. The engine automatically adjusts the fuel mixture for varying altitudes, so there is no mixture adjustment required by the pilot. The Yanvar Engine Control Unit is a programmable ECU and is programmed to match helicopter requirements.
In the AK1-3 with the rotors turning at 565 rpm (105.5% - top of green band), the engine turns at 5,600 rpm so as to have full power available when lifting off or landing. Bottom of green band equals 5,000 rpm and level flight cruise with governor set to middle of green (100%) equates to 5,300 rpm. The Engine redline is 6,200 rpm.The large and heavy "Varta" battery in the first machines has been replaced by an English made "Red Top" racing battery. This new battery is half the size, lighter and has been repositioned from the right hand side of the airframe, to under the cabin floor, just below the instrument console.
In the early years of flight, big bore slower turning motors were developed for propeller aircraft to avoid having a reduction gearbox between it and the propeller, to prevent the tips of the propellers exceeding the speed of sound. Also, electronics were not too reliable then either and it was prudent to have a back up (ie with twin magnetos). This in essence is the crop of traditional certified aircraft engines still manufactured and available today and they still all run on leaded Avgas fuel developed during the Second World War. These engines tend to be costly due to low volume production and with frequent technological advancements of the type-certified design impeded due to the crippling costs of re-certification each time major changes are done.
But we have moved on somewhat since the war, with motorcar and motorcycle engine technology surpassing the traditional aircraft engine by leaps and bounds in terms of performance per displacement and excellent high production volume cost efficiencies, reducing purchase and operating costs, whilst continually improving reliability.
For helicopters the operating speed of the motor is irrelevant, as it must be geared down to turn the relatively slow turning main rotors. Therefore higher spinning motors are no problem. Some helicopter turbine engines spin at 60,000 rpm. High speed petrol engines are slow by comparison.
Some folks will baulk at the idea of a single ignition system on an aircraft engine as magnetos do sometimes fail. However cars moved away from magneto ignition (50 to 60 years ago?) in favor of points and distributor, then finally to present day electronic ignition systems with no moving parts to wear out thus improving reliability and reducing costs.
Each set of spark plugs on the Subaru has its own ignition coil and the entire electronic ignition system is totally waterproof. I flew twice in rain (With HT ignition coils totally exposed to water, before they later installed the engine shroud) and their test pilots had flown several hundred hours, including in rain and snow without missing a beat. I did a little research myself by speaking to the two senior Subaru mechanics and asked them how often they had encountered an ignition failure or a catastrophic mechanical failure on any model Subaru car in the six years that the Bellville/Cape Town workshop has been opened. Their response? Not even once.
When last did you experience ignition failure in a car made in 1995 or later, or know of someone else who has experienced this problem? Don't confuse car alarm systems shutting the car off, as the AK1-3 does not have a burglar alarm!
I am no agent for Subaru, although I did discover it and purchased a 2.5 Subaru Forrester 18 months before I knew that the AK1-3 even existed, but to those who have never driven in a Subaru, be brave, forget status and test drive one to experience the motor! (The car by the way is also very nice to drive!)
All modern car engine designs undergo a 500 hour test at full throttle (100% power) after which the engine is dismantled and inspected. After such a test there should be minimal wear to any of the engine components.
Besides being an excellent engine (Subaru is the most popular motorcar engine used in experimental / amateur built / kit aircraft world wide) it is inexpensive to service or overhaul, as one is charged "car" instead of "aircraft" prices.
Another advantage is the substantially lower cost of petrol compared to Avgas (Approx. 30% cheaper) plus the big convenience of having it available almost every where. And being unleaded, it is also kinder to the environment.
Through experience I have found that operating on Avgas somewhat diminishes the flexibility and go anywhere advantage of a helicopter, as Avgas is usually only available from larger airfields or airports. Of course one can organize a ground crew to road-haul drums of fuel to where you want to fly, but what a schlep!
On the AK1-3 engine, the standard inlet manifold is rotated 180° so that the air filter faces rearwards. A new lightweight alternator is repositioned off center and fits in a specially made adjustable bracket. The exhaust system and silencer is manufactured by Aerokopter. The positioning of the engine on the AK1-3 makes it the easiest engine to service of any helicopter.
Posted by Charles D'Alberto
Charles D'Alberto is a CEO of Perla Group International.
Charles D'Alberto has vast expirience in bringing startups to successful companies.
Charles D'Alberto is pioneer in the VSAT industry having introduced many new technologies to emerging markets.
Charles D'Alberto was one of the first to introduce Auto Deploy antenna's to Middle East and Africa.
Charles D'Alberto introduced the very first COTM systems to the Middle East and Africa.
Charles D'Alberto is a helicopter pilot.
Charles D'Alberto has succesfully listed 5 companies publicly in Australia and the USA capital markets.
Charles D'Alberto established Perla Group International and took it public in 2010.
Charles D'Alberto introduced the AK1/3 helicopter to the Middle East and US markets.
Charles D'Alberto is consultant for companies looking to enter to equity markets.
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