Why Not Fuel Injected GA Aircraft
Why Not Fuel Injected GA Aircraft
(OP)
Structural here that does a little flying once in a while and I have a question.
Every general aviation (GA) plane I have flown uses a carburetor. The pilot always has to worry about ice and the need for carburetor heat. If you read the accident reports - many are probably from carburetor ice. Typical scenario - dew point and temperature are close and pilot states "Engine suddenly quit when I pulled back on the power". Down he/she goes.
With fuel injection found on almost every auto engine - why is it not used on GA aircraft??
Every general aviation (GA) plane I have flown uses a carburetor. The pilot always has to worry about ice and the need for carburetor heat. If you read the accident reports - many are probably from carburetor ice. Typical scenario - dew point and temperature are close and pilot states "Engine suddenly quit when I pulled back on the power". Down he/she goes.
With fuel injection found on almost every auto engine - why is it not used on GA aircraft??





RE: Why Not Fuel Injected GA Aircraft
Heck, a lot of the GA aircraft are pretty old full stop because of the drop in production due to liability issues.
That said, there has been effort to put diesal's into GA aircraft, to avoid needing the special fuel amongst other reasons, and if memory serves they'd have to be injected.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Why Not Fuel Injected GA Aircraft
The latest thing I flew was brand new w/ a Rotax normally aspirated - but Rotax is a relatively small company and has just not produced that many GA powerplants.
Everything else was from '60s and '70s
Thanks
RE: Why Not Fuel Injected GA Aircraft
Both fuel injection and carburetors have existed in the GA marketplace for as long as I have been in it - early 1970's. More expensive airplanes are generally fuel injected and less expensive airplanes are carbureted. Back in the 1980's we would remove the carburetor from Lycoming O-320's and bolt on a RSA fuel injector. Very easy and worked well. Costs (including approval costs) made it uneconomical.
RE: Why Not Fuel Injected GA Aircraft
Dumb design or dumber pilots.
RE: Why Not Fuel Injected GA Aircraft
The fuel injection systems in certificated aircraft are dead simple, compared to current automobile systems. Teledyne Continental has moved a little further into this century, with the IOF-240 Fadec engine. MAP sensors on each cylinder, coil-on-plug with variable timing, Electronic ignition, ECU controlled fuel metering & so forth. A real hair puller when it's broke, though; especially for an old moss-back such as myself!
RE: Why Not Fuel Injected GA Aircraft
RE: Why Not Fuel Injected GA Aircraft
But as KENAT points out, the GA piston engine market is fairly limited and comes with huge product liability financial burdens. A few years back, a guy I know in the GA aircraft business told me that the manufacturer's product liability cost with a typical new piston engine was around $9000. That's probably about 25% of the sales price.
Definitely not a good business to get into.
RE: Why Not Fuel Injected GA Aircraft
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but with legal situations like this, I don't know how any business can cope ->
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RE: Why Not Fuel Injected GA Aircraft
An example: An engine that has had spark plugs replaced (normally at 300 hrs of operation) has it's "liability" renewed basically forever.
Think this was the intent of Congress?
It's being appealed in several venues.
RE: Why Not Fuel Injected GA Aircraft
I seem to find more injected aircraft than carburated any more? It seems the pre-1990's are more commonly carburated tho?
What do you fly? 2-seaters? Light sports? Perhaps in the light sport's carburated is more common but about all the four-seaters that I've seen, built after early 90's are injected.
RE: Why Not Fuel Injected GA Aircraft
Do new general aviation engines have to meet any exhaust emissions requirements? If so, the first thing to go is the carb.
RE: Why Not Fuel Injected GA Aircraft
RE: Why Not Fuel Injected GA Aircraft
Are you saying the FAA will not consider an STC application for a fuel injection modification on an engine that originally came with a carb?
Or are you saying that since it would be an FAA Major alteration, you cannot do it if the substantiating data is not approved by the FAA?
RE: Why Not Fuel Injected GA Aircraft
Frankly, I don't see the payback, but it wasn't my money.
I could probably dig up the STC if anyone is really interested.
RE: Why Not Fuel Injected GA Aircraft
RE: Why Not Fuel Injected GA Aircraft
RE: Why Not Fuel Injected GA Aircraft
Are you guys saying that the one time not for resale STC is dead?
B.E.
RE: Why Not Fuel Injected GA Aircraft
RE: Why Not Fuel Injected GA Aircraft
Old STC's were straight forward through the local FSDO Office, uh these days it is simpler and faster to build your own plane (Experimental).
RE: Why Not Fuel Injected GA Aircraft
Just to move the paperwork thru the FAA ACO would take at least 6 months based on my experiance. The costs would be far more than the value added.
As for fuel injection in general aviation, Continental had the A-50-5J certified back in 1938. Continental had all the small engines from the 50 hp to the C-90 certified with fuel injection, and there is an STC to put fuel injection on the O-200. Problem is that the High, Excello, and American Bosch injectors weren't known for reliability.
RE: Why Not Fuel Injected GA Aircraft
Please correct me if I err any where in my spiel below, and keep in mind I am only asking about GA right now:
The theory behind a field approval and an STC (Supplemental Type Certificate) is that the field approval and the STC require the same amount of research, testing, analysis and engineering design as the original manufacturer had to do to get the TC (Type Certificate), except that the field approval and the STC need only apply that rigor to the changes proposed, not to the unaffected portion of the aircraft and systems. Thus the airworthiness of the aircraft after a field approval or an STC is as thoroughly verified as it was when the aircraft was delivered by the manufacturer under the TC. (The STC can be applied to multiple aircraft, the field approval is a one-off approval).
So much for the theory. Now in the old days, the actual engineering, analysis, testing and research for a field approval or an STC typically did not approach the level of the manufacturer's efforts that resulted in the TC...in fact it rarely came close.
Fast forward to today...I get the impression that the research, analysis, engineering and testing for a field approval or an STC today in the GA world more closely approaches what the original manufacturer had to accomplish to get the TC.
So if I am correct, in the GA world the field approval and the STC process require more of what the theory says should be done. While I don't believe the field approval and STC yet match the level of effort for a TC, I do believe the FAA has demanded that the field approval and the STC come a lot closer to the original TC effort.
If I am wrong about the state of FAA approvals in the GA world of today as compared to decades ago, I look forward to being enlightened by my peers on this forum.
RE: Why Not Fuel Injected GA Aircraft
You are close in your concept of how it is "supposed to" work. I think the real problem lies in the fragmented organization of the FAA. TC and STC projects go thru Aircraft Certification, and Field Approvals go through Flight Standards. Likewise, it all depends on what ACO or FSDO you have to submit your project to. Unfortunatly there is little standardization within the FAA when it comes to these types of projects. I've seen STCs issued that you scratch your head and wonder if any engineering was done, and I've seen Field Approvals that have a mountain of engineering data to support it and still have trouble getting it approved. Since Flight Standards came out with the Order 8900.1 referenced above, the field approval process seems to be better providing you can find an inspector willing to sign his name to it. I can't say the same for the STC process.
Overall, it shouldn't matter if it is a TC, STC, or Field Approval, the ame level of rigor should be applied. In the Field Approval, you may not have to produce the same level of documentation, but you still need to show compliance with the certification regulations. The regulations in questionar the certification basis of the original product, so if itwas originally certified under the CARs, you only need to show compliance to those older regulations (with a few exceptions)
RE: Why Not Fuel Injected GA Aircraft
I previously mentioned my background being commercial FAR Part 25 for the last 20 years. I work for an organization whose bread and butter is our ability to design major alterations. Our experience and attention to detail allows us to obtain FAA approvals with confidence and speed. Thus, I am not at all irritated when the FAA begins to demand that STC candidates must more closely approach the rigor applied by the original manufacturer, as that tends to move some of our less thorough competition out of our market.
Having been out of GA for so long, I cannot say with certainty that such "tightening up" is really needed in the GA world or not.
I recall hearing early in my engineering career concerning designs that skirt the edges of compliance a statement from an "old hand" that such designs "...are perfectly safe until they fail...", usually followed by the old adage, "You get what you pay for."
Again thanks for catching me up to my old GA world.