Nico

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About Nico

  • Rank
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  • Birthday 05/16/1945

Profile Information

  • Gender Male
  • Location Alhaurin de la Torre, Spain
  • Interests High Frequency electronics, antique radio's, flying

Nico's Activity



  1. Nico added a post in a topic how should I vent my header tank ?   

    Ed, my headertank is an aluminimum cylinder with, I think, approx 1 gallon,
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  2. Nico added a post in a topic how should I vent my header tank ?   

    Hi Mark
    I have the same, only one tank in the right wing and a vertical cylinder behind the co-pilot seat as header tank
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  3. Nico added a post in a topic how should I vent my header tank ?   

    Hi Ed
    I did forget to draw a component. Between the +12VDC and ground (at the input of the 78L08) there should be a capacitor of approx 10 uF, otherwise the stabilzer can oscillate.
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  4. Nico added a post in a topic how should I vent my header tank ?   

    Hello Ed
    Attached the diagram of the sensor.
    The NTC resistor in the fuel should be small and connected with very thin wires (e.g. 0.15 mm magnet wire) in order to have a low heat mass. I did glue the NTC at the end of a holow top end of a fishing rod using a small amount of epoxy. The wires go up through the fishing rod wich is glued in a hole in the center of an Metric 8 mm bolt (I guess you will use an other kind of thread...)
    In the diagram you see two measuring points MP1 and 2. Measure the voltage between the points and adjust the potmeter to approx 0.2 Volts when the NTC is in air and the other one is cooled by the topplate of the header tank. MP1 positive. 
    Cool the NTC in a drop of water at the top of the tank. The voltage should reverse. Adjust the potmeter until the voltage in air and cooled are approx the same but reversed.
    When you use 220 Ohm NTC resistors, the temperature of the NTC resistor in Air goes up (more dissipation) and the voltage difference will be bigger, but I found that not necessary. But when you can not get very small NTC resistors but e.g. the 3 mm drop type, than the heat mass is larger and 220 Ohms may be better.
    The reaction time of the sensor is approx 3 - 5 seconds. when the heat mass is low (Thin fishing rod, small amount of epoxy).
    The opamp can be about anything. I use a  LTC271  The LED current can be set by the resistor in the drain of the Mosfet. I use 100 Ohms and 4 LED's, 2 in series and two sets in parallel. Really quite bright. 
    I did glue the complete circuit at the top of the tank with Epoxy.
    About safetety
    The current to the NTC is limitted by the other NTC and by the 78L08 and can never reach dangerous levels. Do NOT use an 7808 stabiliser, than the current can become too large when the upper NTC shorts. 
    Kind regards
    Nico
     

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  5. Nico added a post in a topic how should I vent my header tank ?   

    Hello bandit Please take care. I had the same for 2 years and suddenly had two engine stops. The headertank CAN collect air, and an air bubble in the line from the wing tank absolutely can block your fuelflow. I saw it happening. I drained my header tank completely without nowing due to an airlock and had an engine stop during takeoff (I still could brake....) and one in air. I did cut the engine inmedeately when the RPM went down, the engine kept idling. I looked for a place to land and saw the fuel pressure rising again. I was very close to the airfield, so opened the engine slowly to 3500 RPM and could reach the runway... See also the contribution of Ed. I consider he FAA advice to have a levelsensor at the header tank in our type of planes a very good suggestion. I feel a lot safer and it warned me a coulple of times. I will draw the diagram to a readable version and will post it Ed. Thanks a lot for the info. I absolutely will go this way. I sprayed enough fuel over my plane...
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  6. Nico added a post in a topic how should I vent my header tank ?   

    I have only 1 tank, that may be the difference. I had the Spruce fuel valve in the line between the header tank and the wing tank. After 2 years of flying I had an engine stop. At ground, I investigated free flow and could not find an issue. Tested the engine, cleaned the carbs, nothing wrong. The next week, all ok. The week after that, engine stop in air. Investigated angain and I noticed NO free flow at all. I saw air below the shut-off valve. I knocked the air bulb until it passed the shut-off valve and the fuel started to flow again. I took the valve apart and saw that internally is is only 3 mm throughput!!! Very bad if the connections hav a 5 mm hole, than you fo not expect a throughput of only 3 mm.I informed spruce about it.. I replaced the valve with one that has a 6 mm throughput and the problem was gone. 
    I did read that there are approx 6 accidents due to airlock in our kind of planes, so I took the issue serious. The rest you can read above.
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  7. Nico added a post in a topic how should I vent my header tank ?   

    Thanks a lot EdMO
    If I put the vent tube at that place, I can attache a long tube inside the tank to reach to the far end of the tank wich is higher than the root end. Do you think that helps or is this altitude sufficient to ensure a good venting?
    I saw the level meters at Spruce, but the price was a little high. When you make it your self, it is only a few dollar. I designed and made electronics for aircraft and spacecraft, so no problem at all. It is super simple. When there are more people liking electronics, I can post the schematic diagram.
    Kind regards
    Nico
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  8. Nico added a post in a topic how should I vent my header tank ?   

    Hello Jim
    I am an electronic engineer. I did make a metric 8 mm hole in the topplate and did fit a M8 bolt with a center hole. Through the center hole I did stick approx 12 cm of the top end of a fishing rod (hollow). At the bottom end, I did glue a very small NTC resistor of 470 Ohms and did seal everything with epoxy. Two thin (0.2 mm)wires pass through the top end of the fishing rod giving electrical access to the NTC resistor. NEVER put the battery voltage to one of the NTC wires. Than a short circuit may give fire or explosion danger. 
    I designed a little circuit with a weatstone bridge that could measure the difference between two the same NTC resistors. One in the tank, one glued to the topplate of the tank. When the power applied to the bridge heats up the resistors (only milli watts and always current limited to prevent fire danger). The resistor in the tank will be cooled by the fuel and the resistor at the topplate by the topplate. As soon as the fuellevel sinks and the NTC resistor is above fuel level, it heats up approx 10 - 20 degrees more than the other NTC resistor and the bridge gives a voltage that can be connected to a LED flasher at the dashboard. Simple, reliable, easy to make your self and very low cost.
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  9. Nico added a post in a topic how should I vent my header tank ?   

    It seems that most people have the ventline as suggested by the construction manual and had to add a valve to prevent fuel loss through the vent line. I could not find an angle without fuel loss or pitot pressure in the header tank that gives fuel flow issues Paul. . I had to put the valve in the line as well as told by  Jim, and it works fine. The only problem I see is that, when I like to vent in air, fuel sprays out of the ventline when the air is gone over the plane, which I do not like too much.
    Ed, can you give me a bit more details about the place of the upper hole in the tank where you suggest to vent?
    I think that the recommendation to have a fuel warning alarm in the header tank when the level sinks, is quite important. It did alarm me e few times!!. Highly recommendable!!
    In order to prevent fuel loss out of the ventline when venting, I like to know what you guys think about a riser tube next to the winktank exit elbow that goes to the top of the tank at that position. I know it is not the higest point in the tank, but the other end of the tank (e.g. the neck of the tube where the cap goes on) is very difficult to reach for venting without damaging the fabric. 
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  10. Nico added a topic in Avid Flyer General Hangar   

    how should I vent my header tank ?
    I have an Avid flyer STOL, and flew without problem for almost 2 years. Than suddenly I had a few engine fails. I investigated and found the problem, air lock in the shut-off valve from the wing tank to the header tank. I did replace the standard valve by a homebrew valve with 6 mm throughput, mounted an electric Facet pump at the header tank exit  and solved the problem, though many times there is still air in the line below the elbow of the wing tank excit. I have to get the air out manipulating the electric pump at the exit of the header tank. I did write an article about the airlock problem end the valve.
    I also did make a header tank vent as described in the manual. But that was no success. When pointed forward, the pitot pressure in the header tank due to the vent did prevent the fuel flow from the wing tank. When pointed aft, it did suck lots of fuel out of the ventline. I could not find a way to vent properly and mounted a valve in the ventline. Now I vent the headertank at the ground and shut the valve before take-off. 
    It works well, but I am not really happy with this set-up because in principle it is possible that the header tank collects air when the aitcraft makes right turns. I followed the advise to mount a level alarm in the header tank wich gives me quite a safe feeling.
    I like to know if someone ever mounted  the vent in the wingtank by a riser tube next to the tank exit. Please comments.
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  11. Nico added a post in a topic leading edge cuff on KF 3 undercamber   

    A friend of me, actually my flight instructor, has put VG's under the hor. stab approx 4 inches before the stab/elevator separation. It gave him an astonishing 20 kM/hr max speed increase at his 912 powered apollo fox. Speed was 180, is now a little over 200 kM/Hr
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  12. Nico added a post in a topic In-line fuel shutoff valves   

    Take care with the in-line fuel valves, See the topic Air/vapor lock in general. I had two engine failures due to the valves.
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  13. Nico added a topic in Avidfoxflyers General Hangar   

    air/vapor lock in avid flyer
    I am Nico van Dijk, living in the south of Spain and owner of a stol avid flyer EC-YFP. Engine Rotax 582 After flying approx 25 hours total in this plane, I had a engine failure at take-off. I immedeately did cut the engine power and could brake in time. The engine remained running. After checking about everything, I could not find any problem. In order to be more sure, took the carburetters apart and cleaned them. Nothing found, no water, everything very nice and clean. Checked for water in the fuel again, nothing. Checked the free flow at the position of the fuelpump, approx 0.7 Litres/minute, ok. So I mounted a fuel pressure meter and a fuel level alam at the header tank and tested the engine at ground, all OK. I did take-off again, EG temp ok, power ok worked very fine. A week later I flew at 5400 RPM and had en other engine failure in air. Did cut the engine wich remaied running at 2000 RPM and looked for a place to land. While doing that, I saw the fuel pressur rising to normal, opened the engine slowly and could return to the airfield. There I tested everything again and found the problem, air or vapor lock. From the wing tank I had a small fuel valve from Aircraft Spruce number 05-0104x mounted in the line going to the header tank. There is an other of such fuel valves for panel mounting in the panel in order to prevent that the carb's flooding when parked for a long time. During a test run, I saw a vapor or air bubble underneath the fuelvalve between the wing tank and the header tank. This bubble did not pass the fuelvalve and did completely shut-off the fuel flow. After a few minutes, the fuel level in the header tank lowered and my alarm went off. I knocked the airbubble wich bit by bit started passing the fuel valve. As soon as it was gone, the fuel started flowing and the level in the header tank was restored. I checked the main tank end the fuelvalve for debris, were perfectly clean. So I took the fuelvalve apart and... surprise. The connections are 5 mm interior, but the valve has only a throughput hole of 3.15 mm (half the expected flow!), leading to the vapor lock problem. The bubble and the fuel can't pass each other in this small hole. I mounted a fuelvalve with a througput hole of 6.5 mm and the problem was gone. But there is an other such valve in my panel. So also vulnerable to Air / vapor lock. In order to prevent that I did mount a Facet pump (low pressure!!) near the output of the header tank so the rest of the fuel system is a little pressurized. So far everything is fine again. Fuel pressure at the Mikuni pump only approx 4 PSI, At the Facet pump only approx 3 PSI, when both on, 5 - 6 PSI I contacted Aircraft spruce about this. I explained, but no results yet. I think that the fuelvalve should have throughput hole the same size as you can see at the connections. This situation is dangeroeus and a vapor or air lock can happen any time. When selling fuelvalves, the seller should advertise the throughput hole!!! Kind regards Nico
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