Europa-List Digest Archive

Tue 12/26/17


Total Messages Posted: 2



Today's Message Index:
----------------------
 
     1. 12:40 AM - Re: Cooling a Mono Classic (Ruedi Vogel)
     2. 01:59 PM - ACS key ignition switches (jonathanmilbank)
 
 
 


Message 1


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    Time: 12:40:05 AM PST US
    Subject: Re: Cooling a Mono Classic
    From: Ruedi Vogel <r.vogel@ggs.ch>
    Hi Kingsley I have had temperature problems just during the first flight with my Classic 912S, although temperatures in Switzerland are normally much lower as in your country. The engine stopped in about 120m AGL because vapour lock. You could read the full story in the Europa Flyer December 2016. There was no time for checking the temperatures. But I think the oil temperature was about 120C after take off, because the cooling effect during taxi and run up was not enough. This has been confirmed by additional tests. After some modification to the cowling the problem was fixed. See this link: http://www.theeuropaclub.org/building/cowl-and-cooling "Cooling 101 for Europa" This modification has been done to the cowling: - Enlarges the inlets for cylinders and radiators - Enlarge the duct ramp about 5cm each sides - Add a temperature sensor (LM335) on top inside the cowling for monitoring the temperature around the fuel system and contact to the MGL EFIS aux. input. That's all. Everything with temperatures seems to be OK now. Kind regards from fogy Switzerland. Ruedi Vogel, HB-YJF Am 24.12.2017 um 12:40 schrieb Kingsley Hurst: > I have a plain vanilla 80HP Mono Classic. Plumbing of the coolant > radiators are as per the book and the oil cooler is mounted underneath > the spinner as recommended by Europa. > Cylinder head and Oil temps were totally unsatisfactory until I made > two ugly fixed cowl flaps (temporary ones) that allow a better air > exit path. Today, with a ground temp of 38C (@400 ASL) I climbed from > ground level to 8,500 ft at 80kts IAS on full throttle and 5500 RPM. > Max CHT and Oil Temps reached were 102C and 116C respectively. In > cruise at 8500 ft on full throttle (22" MAP) and 5000 RPM with OAT of > 17C, the temps dropped to 70C and 84C respectively which is a bit cool > but easily fixed. I'm happy with the cooling at this moment but am > unsure how it will be in the hot conditions of North Western > Queensland where the ground temp is often around 42C to 45C but I digress. > After shutting down today, the OAT was 39C. CHT was 91C and Oil temp > 88C. After opening the hatches on top of the cowl, I felt the temps > of the two coolant radiators in the front of the cowl and one was > noticeably hotter than the other. This is understandable as both > radiators are in series. > Ignoring the complexity of the required plumbing, I then contemplated > what might happen if the coolant radiators were connected in parallel. > I reasoned that if in parallel :- > > * The temperature differential (deltaT?) between the coolant temp > and the OAT would be maximum on both radiators giving more > efficient cooling as opposed to different differentials in the > series set-up . > * The flow rate through each radiator would be halved so coupled to > the higher deltaT, I assume better cooling as a result. > > My question, > Does anybody have first hand experience with such a set-up and if so, > do you have any documented evidence of improved cooling as a result? > Cheers and all the best for the Festive Season to all. > Kingsley in Oz. -- Ruedi Vogel Wiesenweg 6 CH-3380 Wangen a.A.


    Message 2


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    Time: 01:59:54 PM PST US
    Subject: ACS key ignition switches
    From: "jonathanmilbank" <jdmilbank@yahoo.co.uk>
    This topic comes up from time to time and my belief is that if Rotax and Ducati felt that there was a problem, then they would have put out a written warning years ago. Yet there are many who swear that these ACS key switch units cause ignition and rough running problems. What's the proof of this? Here's an opinion which someone passed on to me, because he's about to change to separate toggle switches for grounding his Ducati ignition modules: "My local airport is KGVT, Greenville, Texas. It is home to the defense contractor L3 Mission Integration Systems. L3 employs thousands of engineers. I am fortunate to rub shoulders with many of these engineers both active and retired. I spent much of the day with a pilot/electrical engineer who has over 35 years designing and specifying aircraft electrical systems. We discussed the magneto switch when used with the Rotax Ducati ignition system. He agreed the notion of a magneto switch causing a failure of the solid state module with some type of "feedback" was poppycock. He also agreed the AC voltage on the Ducati kill circuit was less damaging to a switch than the P lead circuit on a magneto ignition. Lets look at the facts, how the system operates, and possible failure modes. The Rotax Ducati ignition uses a shorting wire to kill the ignition. It is only grounded on engine shutdown and during ignition checks. The shorting wire is grounded through the mag switch. If the shorting wire is disconnected or breaks, the engine continues to run. The only electrical things that could damage the ignition module are overvoltage and improper or shorted wiring. The Rotax engine dynamo supplies power to the modules. Voltage is limited by engine rpm. Current is physically limited by the size of the dynamo coils. It is impossible for the dynamo to supply excessive voltage or current to the modules. The vast majority of Ducati ignition module failures are wires breaking inside the insulation close to the module due to vibration. The premise that AC voltage present on the grounding circuit is too high for a magneto switch is unfounded. The voltage involved when grounding a Ducati module is similar to the voltage present on the P lead of most magnetos. The internal arcing with AC voltage is less than what would be present with a pulsed DC signal from a magneto. There is no reason to assume one or more toggle switches will last any longer than a standard magneto switch. While we have no doubt some standard type magneto switches have failed while in service on the Rotax engines, we do not believe they are the cause of ignition module failures. If the contacts on the magneto switch were to corrode or burn to the point where they no longer make continuity, the respective module would simply not shut down with the switch in the off position. I dont think LEAF, Lockwood or anyone else can explain how an open kill circuit due to a bad switch is the cause of ignition module failure. Advising aircraft owners to change the magneto switch to toggle switches is questionable. The magneto switches are aircraft quality devices with large contacts capable of handling high voltage and current loads either AC or DC. Magneto switches are used successfully on many Rotax 912 equipped aircraft without incident. The replacement toggle switches are largely unspecified. A 250 volt toggle switch can be a totally inadequate miniature device capable of only 0.5 amps. with quality or origin unknown. In summary, the Rotax Ducati ignition module kill circuit is not likely to damage a magneto switch or a replacement toggle switch. Nor is any switch, magneto or toggle likely to cause a failure of the ignition module. John Pitkin" Read this topic online here: http://forums.matronics.com/viewtopic.php?p=476797#476797




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