Why Not Fuel Injected GA Aircraft 2

[MiketheEngineer]

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??

 

[KENAT]

... because most of the engines in GA aircraft are very old designs.

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.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MiketheEngineer]

Very good point that I hadn't thought about.

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

 

[johnSchwaner]

Economics

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.

 

[MiketheEngineer]

Figures... I just see so many "icing" crashes... makes you wonder??

Dumb design or dumber pilots.

 

[thruthefence]

Mooney Aircraft actually had a Certificated Porsche flat six, complete with Bosch electronic fuel injection, and fan cooling. It failed miserably in the market place.

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!

 

[johnSchwaner]

I had a carburetor ice detector installed in the late 1970's and flew several thousand hours with it and it worked; so the technology has existed for a long time. Tried to sell them without success. An old adage in the aircraft parts industry: "safety doesn't sell"

 

[tbuelna]

There are injected avgas GA piston engines. And the new diesel GA piston engines are all direct injected.

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.

 

[kontiki99]

GARA offered some relief ->

http://www.wilsonelser.com/files/repository/GARA_April2006.pdf

but with legal situations like this, I don't know how any business can cope ->

http://www.freerepublic.com/focus/f-news/2508765/posts

 

[thruthefence]

Gara has been circumvented in some court findings, by the legal "theory" that if ANY parts have been replaced on the product since "new", the GARA clock essentially starts over, (along with the liability)

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.

 

[vonsteimel]

Almost all the newer ones are injected. I never flown a carburated C-172. Our 152's at the flight school are carburated but everything else is injected. Our 172's, arrow's, senicas are all injected.

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.

 

[dgallup]

I have to believe that even in light general aviation the carbs must be going away. The carb manufactures are almost gone. Fuel injection has been at 100% penetration in automotive for industrialized nations for years, it is near 100% for motorcycles. Even single cylinder MX bikes are fuel injected now. Garden tractors and boats are fuel injected (not 100%). About the only new spark ignition internal combustion engines left with carbs are leaf blowers, string trimmers and the like.

Do new general aviation engines have to meet any exhaust emissions requirements? If so, the first thing to go is the carb.

 

[Knightflyer]

Hi Mike... The FAA will not let you change a certified aircraft engine that came with a carburetor to a fuel injected one.. Also you can't put that modefacation into a certified aircraft that came with a carburetor.. As it goes with Card-ice..just keep your eye on the EGT gauge and when it moves down.. pull carb-heat.. I have had carb-ice on start up at Truckey CA: at 6:00 AM. and carb-ice over Cottonwood AZ. at 8,500' under broken clouds in December and all the times I was able to keep that old continental ticking over.. It is the pilot's responsibly to fly safe. ... The Knightflyer!

 

[kontiki99]

Knightflyer,

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?

 

[thruthefence]

I disagree with Knightflyer, having been involved in the STC'ed installation of a fuel injected TCM IO-520 in an older Cessna 182, that was originally equipped with a carb engine. It was a bit labor intensive, requiring the installation of fuel injector bypass lines back to the fuel tank, and the installation of a small "header tank" aft of the firewall, under the cabin floor, which had to be vented through the original fuel vent system. A high/low pressure electric fuel pump was required, along with all the wiring mods, switches, circuit breakers, annunciatior lamps, etc.Lots of plumbing inside the aircraft, a new fuel flow indication system, & so forth.

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.

 

[Knightflyer]

HI Kontiki99 I read your bio. # one ..The answer is NO! The FAA will consider any appropriate paperwork application. Getting an answer back w/field approval is almost.impossible.. # TWO>> You know that any major alteration on anything must have field approval along with the 337,( along with an STC) The form, down at the bottom has to be signed off by the FAA. What I said was that its cheaper to buy the existing STC , (if any for model and type)> Than!, try to re-invent the old Wheel..I don't want to make anyone up set! But I would love to replace my 0-360's carburetor with a injection system, But it does not make financial sense . Good job MIKE>> it looks like you realy started something with you simple statement. Thanks, Knightflyer.

 

[Knightflyer]

HI: Thruthefence. I don't think you disagree with me at all.. It sounds like we are on the same page when it comes to changing out the carb. for an injection system.. Of course there are STC'S out there but its not cost effective to make the change.. For example... The price for the STC, engine and work to put an 0-360 into a 172 Cessna is more than $40,000. I have the STC! on MY P172D which has an old 0-360 with a New (2010) Hartzel constant speed prop.. but I have a carb!!!My Skyhawk was one of the original four that received the original STC that converts the six cylenders to the four cylender 0-360 Back when the STC was for the CESSNA 175. Any way it okay to have good conversation about anything that has to do with airplanes..If there is an STC.. buy it! Just don't try to get your own NEW STC. The cost is out of sight.. I am currently working on finishing my new oiling system for old continentals . and I have been told my people in the know that getting approval for it will be next to impossible.. Thanks.. Knightflyer

 

[berkshire]

Knightflyer and thruthefence,
Are you guys saying that the one time not for resale STC is dead?
B.E.

 

[thruthefence]

Not at all, but the field approval process has become very cumbersome, & time consuming. Nearly the same as certificating an aircraft.

 

[twalter]

As to older Cessna'a... 172N (1979) is carbed. The primer lock occasionally sticks and doesn't lock (uh why is the engine running rough, and I'm burning 15 gph?). No I would never do that!

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).