Since planes must fly through all types of weather conditions in the same flight, IE-temperature, humidity and pressure changes, is the fuel system requirements different from a land based engine?
Well I’m not an expert on land based engines, so I’m sure my answer will not be complete, but I can point out a few differences of an aviation engine compared to my limited knowledge about automobile engines.
1. Transmissions - There is no transmission on an aviation engine. The pilot simply increases the throttle to increase fuel/speed of rotation.
2. Gasoline - Aircraft piston engines are typically designed to run on aviation gasoline. Avgas has a higher octane rating as compared to automotive gasoline, allowing the use of higher compression ratios, increasing power output and efficiency at higher altitudes. Currently the most common Avgas is 100LL, which refers to the octane rating (100 octane) and the lead content (LL = low lead).
Avgas is blended with tetra-ethyl lead (TEL) to achieve these high octane ratings, a practice no longer permitted with road vehicle gasoline. The shrinking supply of TEL, and the possibility of environmental legislation banning its use, has made a search for replacement fuels for general aviation aircraft a priority for pilot's organizations.
3. Carburetor Icing - I have never heard of carburetor icing in an automobile, but it can happen in an aircraft. When air and fuel enters the carburetor chamber, it is sped up (or slowed down) by the use of a mechanical venturi. The throttle valve (hinged inside the venturi) is used to dictate how much of the mixture is needed at a given time, and the carburetor supplies it accordingly. The problem of icing can occur right after (or during) the mixture passing through the venturi. As the mixture speeds up, the fuel can actually vaporize, creating a possible freezing situation. If this occurs, ice can form, which may restrict the flow of fuel and air into the engine.
Carburetor icing is easily corrected by using carburetor heat, which is air heated from flowing over the exhaust pipe. The Diamond aircraft I have been training on are fuel injected so I don’t have to worry about carburetor icing.
4. Fuel mixture – As the atmosphere changes with temperature and altitude the amount the amount of oxygen in the air is also impacted. This can cause the air to fuel mixture to be imbalanced. The pilot can control the mixture ratio from inside the cockpit.
5. Magnetos - I’m not sure what is the source of the electrical current that allows the spark plug to ignite the fuel on a car, but the magnetos are the source on a plane. Since this is so important, there is normally two magnetos just in case one fails. The pilot will test both magnetos during the pre-flight checklist.
6. Fuel Tanks - In most planes, the fuel is kept in the wings. Low winged planes will have a pump to send the fuel to the engine, while a high wing plane may utilize gravity. If the tank is in the wing, the pilot may have to manually switch the tanks during flight. To keep the plane balanced, the pilot wouldn’t want one wing to be full of fuel, while the other is empty.
On the Diamond aircraft I have been flying, the fuel tank is in the fuselage and does have a pump.
Now that you can fly solo, does this mean you are a pilot?
Being endorsed to fly solo means that I am a student pilot. There are many restrictions to how/where/when I can fly. I cannot have any passengers other than my CFI, my privileges expire in 90 days (unless my CFI endorses them again), and I’m limited on what maneuvers I can do.
For example, there are times when ATC may clear me to land, but will want me to stop at a certain point on the runway to allow other traffic to pass. This is called land and hold short operation (LAHSO). I am to inform ATC that I’m “unable”, since student pilots cannot accept this request. As you can imagine, if a pilot agrees to land without using the full runway, but fails, the outcome could be disastrous.
What is next in your training?
I have about 15 hours of flight time, and the minimum is 40 hours for a private pilot, so I still have a lot of training left. Of course, I will continue to enhance my basic skills of controlling the aircraft, but the hard work is yet to come. If you have been reading this blog for a while, you may have noticed that I haven’t gone anywhere (except one flight to the Lebanon airport). Most people fly so they can get somewhere, so the next big milestone will be a cross country flight. This requires navigation, weather predicting, calculating fuel consumption and much more. I’ll also need to spend some time flying at night. I’m expecting the next couple of months to be more challenging than the last couple.
Thank you for joining me on this adventure. Keep the questions coming, the research is making me a better pilot.
What do we know about propellers? I think most are made of wood, maybe Ashe like baseball bats, or maybe aluminum too. How is size and pitch determined? I've seen "props" with various numbers of blades, two, three and even four. What is the determining factor? Why are some mounted on the nose and some on the wings?
ReplyDeleteHow about wheel position? Tri-pod or tail dragger. Seems like with the tri-pod set-up the pilot would be less likely to catch a nose mounted "prop" in a steep angle or when landing "off runway". What is the real answer?