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Is this a dumb question?

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I'm not a pilot ... so it might be:Why do I have to turn on pitot heat?I was driving home tonight in about 6 inches of Global Warming that is currently falling on my driveway and I looked at the external temperature gauge that is on my vehicle and it told me that the outside air temperature was 28 degrees.Now, how come my airplane doesn't have one of those? And when the thermostat says the outside air temperature is nearing freezing, why doesn't my pitot heat just fire up automagically?And fire up the cabin heat for me too, while it's at it?Am I stupid, or are airplane designers? (I'm asking for it, I know!)

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The pitot heat requires a fair amount of amperage, and there really needs to be some moisture in the air. You can easily be at freezing temps with nothing to freeze.L.Adamson

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LAdamson is right. You don't ALWAYS need pitot heat when it's below freezing. As I understand it, many times, if a plane is at, say, 22000 feet, it might be -20degF, but it's far too dry up there for any significant ice to form.Same for icing. Doesn't happen as much at high cold altitudes. At low altitude, where there is often more moisture, that's when you can ice up, or neet pitot heat.At least as I understand things.RhettAMD 3700+ (@2310 mhz), eVGA 7800GT 256 (Guru3D 93.71), ASUS A8N-E, PC Power 510 SLI, 2 GB Corsair XMS 2.5-3-3-8 (1T), WD 250 gig 7200 rpm SATA2, CoolerMaster Praetorian case

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Really?It puts that much pressure on the aircraft systems that turning it on is a factor?As a non-pilot that seemed really odd to me. I gather from just using flight simulators that NOT turning it on when it's needed can be rather unpleasant; so I was just wondering why it's left up to the human.

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Any time you add automation to a vehicle, you add weight. You are also adding something that can break. And on top of it, every single system in the plane has to run through an exhaustive approval process with the FAA assuring its reliability, which costs unimaginable amounts of money.The goal of every airplane designer is to design a plane that is as reliable and light as possible. Hence, even today the pilot still has to control the mixture of the gas/air going into the carburator and FADECs are still a thing of the future. When was the last time you saw such a thing in an automobile?Thomas[a href=http://www.flyingscool.com] http://www.flyingscool.com/images/Signature.jpg [/a]I like using VC's :-)N15802 KASH '73 Piper Cherokee Challenger 180

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Also, when comparing car systems to airplane systems, think what the requirements are to drive a car and then compare that to the vigorous process of obtaining a PPL, and considering any idiot can drive a car, it makes sense that most systems are automated.Ian.

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"Hence, even today the pilot still has to control the mixture of the gas/air going into the carburator and FADECs are still a thing of the future."The DA-42 that I was doing my multi in had a pretty nice FADEC setup. No mixture or prop levers here. We actually had to get clarification from the FAA that the hours flown in it can be logged as complex, since the prop pitch is not directly controlled by the pilot. And it runs on Jet A. How cool is that? :-)

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Also understand that Flight Sim does not model the pitot heat function very well. The icing of the pitot is more on the temperature than on the moisture/temperature combination in the real world.In FS, turning on the pitot heat is required most of the time, especially for high altitude flight.As noted above - weight is everything in an aircraft - and the weight of the amount of money required to buy some automated systems is also a factor especially for small aircraft owners.

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>>And it runs on Jet A. How cool is that? :-)Isn't a DA-42 one of those Diamond aircraft, like a Diamond Katana?That's weird! Or is that getting more common? A piston engine running off Jet A. Does it have a carb'ed engine or is it fuel injected?RhettAMD 3700+ (@2310 mhz), eVGA 7800GT 256 (Guru3D 93.71), ASUS A8N-E, PC Power 510 SLI, 2 GB Corsair XMS 2.5-3-3-8 (1T), WD 250 gig 7200 rpm SATA2, CoolerMaster Praetorian case

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I don't think its a matter of being stupid. Some aircraft have auto heating of the pitot, etc. In the same token all airliners always have the pitot heat on while in flight.Most GA aircraft are not flying along at FL340 for 8 hours either. The vast, vast majority of GA aircraft fly VFR (since the vast, vast majority of private pilots are not IFR Rated). Flying VFR, you're not supposed to fly into any clouds, not supposed to be above FL180, and finding yourself in icing conditions will end up being the exception rather than the norm. So if we go on that premise, why bother to add the extra weight of an automated temperature sensing system when a 1 ounce manual switch would do the job just as well. And just as Geofa said, in most GA aircraft you have to pick your electrical "battles" quite carefully. If you are flying in with your landing lights on and the system decides to turn on your pitot heat, cabin heat and everything else you may find yourself declaring an emergency when your alternator can no longer take the load.Its much like the stupid automated headlights that come on when it thinks its dark enough and stay on while you walk into your house and similarly automated winshield wipers. While some people may well like these features, do I really need the car to turn its lights on and off or the winsheild wipers on and off...or am I not capable of seeing that its dark outside or its raining and take the appropriate action. Remember those automated seatbelts and talking cars that told you that your door was adjar and your parking brake was on? There is a fine line between automation and having one's intelligence insulted.As a matter of fact, most GA aircraft have so little automated features that an automated pitot heat would be the absolute last thing that one would think of when one would rather spend the money on a tricked out autoflight system with GPS slaving capability!

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A diesel! Wow, the other diesel planes I know about were from the 1930's. Maybe some ag planes are diesel too?One thing about diesels, they have advanced a lot in recent years, and in many ways they are a nice design, capable of burning some interesting fuels. And today's turbo diesels are works of art.I knew a guy who burned used transformer (electrical transformer) oil in his diesel for years.Do you know how diesels react to air/fuel mixture in an aircraft? Just like any other internal comb engine?RhettAMD 3700+ (@2310 mhz), eVGA 7800GT 256 (Guru3D 93.71), ASUS A8N-E, PC Power 510 SLI, 2 GB Corsair XMS 2.5-3-3-8 (1T), WD 250 gig 7200 rpm SATA2, CoolerMaster Praetorian case

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Not only has it to be autometd but in needs checking to demonatrate it's still functioning and hasn't failed. It would also probably need a manual backup to cope in the event of failure.It all gets just too complicated.

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Thanks everyone, for your input.I hadn't considered the weight-to-necessity ratio, which is understandable. And I had no idea that the electrical systems in GA aircraft were run so close to the edge of disaster that turning on your pitot heat might result in the declaration of a landing emergency.I don't know why, but I'm just amazed by that.

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It isn't really the edge of disaster. Many aircraft that fly today are older in age-my Debonair was a 1962 model. It was designed at a simpler time when there were just a few avionics that didn't draw much power and originally had a generator instead of an alternator. When aircraft started to get more avionics and equipment-the generator on this plane was converted to a 40 amp alternator(has to have Faa approval first)-but additional avionics and additional equipement like anticollision lights kept being added to the aircraft. Having everything turned on including the pitot and landing lights-(two of the biggest draws) could overtax the alternator. If you needed both on you usually turned something else you didn't absolutely need off, if the alternator wasn't keeping up-which sometimes happened and sometimes didn't. I finally converted it to a 60 amp alternator and was able to have everything on-of course that cost a lot of money-and some aircraft you can't get approval to do this. A company has to get special approval from the Faa to modify something like this-so even if you want to put a bigger alternator on it may not even be an option for the aircraft you own.Now flying a Baron I have two alternators. Still-when you want to test if the alternators are working you turn one of the alternators off- then heavy drains like the pitot heat and landing lights on-the pitot and landing light will take a pretty big draw on the needle.http://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg

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And, as the alternator has to create a higher amperage to satisfy the load, it's also taking some of the available "prop" horsepower from the engine to do it. It's just like turning on the air conditioner in a car, and feeling the loss of power.Happily, dealing with "experimental aircraft", I installed a 60 amp alternator on the Lycoming because of the pitot heat. And I may never use it; it just looked cool. But when I bought it, it was around $200. Now it's closer to $1900.00! Must be one of those "liability" things! :-hah L.Adamson

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You have to realize...a cheap Hundai automobile has more sophisticated technology than a $300,000 GA aircraft. Economy of scale has to do with it I suspect. Even Carborated engines are used in many of the GA aircrafts.:)Manny

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>It has more to do with those reasons mentioned above. It it>was easy to certify, they would just take the systems>developed for cars.>Within the homebuilt/kitplane/experimental market, where you're free to use engines of choice; the "argument" and preference's between certified aircraft engines and automobile derivatives goes on and on.The majority still prefers the air cooled Lycomings and Continentals.Auto engines require radiators along with anti-freeze that need to be shoehorned into a cowl without adding too much additional drag. They also need prop reduction units, with either belts or gears, to get the 5500-6500 rpms down to usable prop speeds of around 2700-3000 rpm. This adds more weight and another possible failure point.Then there is the electrical systems that depend on an operating alternator and battery, instead of "magneto's" should the main electrical system go off line. This requires additional redunency and weight, in one form or another.The "airplane" engine, also has a hollow crankshaft on the forward section for pressurized oil which operates the constant speed propeller. Using an auto engine requires an electric prop or just a fixed pitch.As to pricing, the certified aircraft engines are a lot more than the base price of a comparable horsepower modern auto engine. But by the time all the accessories are installed for the firewall forward, then the prices are rather comparable.These airplane engines are still somewhat 1930's technology, but in many ways, the simplicity and "weight" still beats the alternatives. Fuel injection is available and widely used, but carburetors still have their own advantages. Electric ignition systems may also replace at least one of the magneto's, while the other is still a backup.L.Adamson

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I'll tell you OP, they have it all wrong. It isn't because airplane designers are dumb (they are very clever) it is because pilots are dumb. You see if the designers made it all automated then student pilots (like myself) would never have to consider icing conditions and aeroplanes would be forever falling out of the sky. That's the real reason. (excuse me while I duck under my desk)

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