Over 100 years of Carburettor Engines...

[scifi]

And we still don't have a Carburettor that corrects for altitude.


In that time we have automatic Advance and Retard, automatic Chokes, some cars can even control the Climate..!


As the Mixture Control is controlled by the pilot, it is all too easy to get it wrong; First by not correcting when climbing; and more importantly, not resetting to rich when descended.


Do none of the carburettor firms have anyone working in R+D...

[Arthur Bellcrank]

Rotax Bing carburettors have HAC (high altitude compensating) giving automatic altitude compensation, leaning at altitude, to over 20,000 feet.

[ShyTorque]

Over 100 years of Carburettor Engines...And we still don't have a Carburettor that corrects for altitude.

And it's about time that all aircraft engine manufacturers did away with carbs and fitted fuel injection instead.

[scifi]

Quote.. And it's about time that all aircraft engine manufacturers did away with carbs and fitted fuel injection instead.


And that doesn't get us out of the back-woods either.
Still must set Mixture, and also Start a hot engine on Idle Cut Off.


Not to mention the 19th centuary ancient art of 'Priming'...
.
edit.. I forgot... What's all this 'Pump On' / 'Pump Off' routine all about...?
.

[ShyTorque]

Scifi, a well designed modern injection system would do away with the need for that. The injection system on engines such as the Lycoming are mechanical, ancient devices designed decades ago. They have no sensors, hence the need for the pilot to manually set the mixture and rely on witchcraft when it comes to starting procedures!

[wrench1]

scifi.


Something else to think about...


It's all about supply and demand. As for R&D... yes, everyone in aviation is always working on improvements. But it comes back to bang for buck.


Following Shy's example of a "modern" fuel injection system... I would fathom a rough cost of $50 to $100 million USD in R&D to get a altitude compensating system to the certification level. And who knows what the costs would be to get it to a production level.


Now add that cost into the cost of a new aircraft, or the cost of an STC (at least on my side of the pond) and you will find your average weekly flyer would not pay the difference between a "good-old-100-year-old-carburetor" and a new altitude correcting fuel injection system.


Now if you can get a team together and produce a certified system at less cost... you might have something to work with.


Good Luck
W1

[cyclic35]

While I'm not able to provide a reference just now, I'm fairly sure that some of the Claudel-Hobson carbs produced in the late 1930s had automatic altitude control.

As fitted to the Hercules 264 radial sleeve valve engines on the Varsity.
(5FTS Oakington)

[noflynomore]

$50M to develop an altitude correcting carb? Seems a vastly excessive amount to me.

Surely automotive injection systems are altitude compensating, and up to the altitude most light aircraft never exceed too? You'd only have to adapt the software to a different engine and off you go. What's so hard about that?

[wrench1]

Nofly:

It is not about the hardware. That's the easy part. There's probably 100s of existing fuel systems that could be adapted. Matter of fact, you can legally pull the entire fuel-injected engine from a car and put it in an aircraft-- so long as you certificated it under Experimental. (FAA wise)

The problem is when you want to install it on a Type Certificated aircraft, or more precisely a Type Certificated engine. That's where the money comes in.

Even if you use an existing fuel system, the entire system must be de-constructed to comply with the requirements of FAA certification.
This is just the surface:
http://www.faa.gov/documentLibrary/media/Order/8110_4C-CHG_1-5.pdf

Now if the TC holder is not interested in development, your only option would be obtaining a Supplemental TC. The kicker is you would have to do this (i.e., pay for) for each TC model you wish to install your system. This includes a bunch of engineering approvals, test beds, prototypes, etc.

I think it can be a little ridiculous as there is some neat stuff out there that could very easily be adapted and provide safe flight. But it's the regulatory system we have.

My personal favorite: EC135 helicopter transmission requires a "very special" oil as part of a modification. When you open the fancy box it contains a Castrol oil for Mercedes Benz transmissions. The only difference is a small sticker that says "ZF approved" with an additional cost of $25 a quart because it is "certified oil."


W1

[riff_raff]

What is this "carburettor" thingy being argued about?

[Progressive]

Actually, we do have carburettors that compensate for altitude. Most bendix and TCM carbs and fuel injectors have an "automatic mixture control" option which consists of a small sealed bellows attached to a needle valve in the fuel jet. As ambient pressure decreases the bellows expands and the valve restricts the fuel flow.

Digital auto lean can also be fitted to some approved aircraft models under an faa stc. See here
https://www.aircraftspruce.com/catalog/appages/autolean10-06034.php

The main reason aircraft dont have these systems is related to increased cost and complexity and decreased reliability.

[MarkerInbound]

Bendix-Stromburg pressure carbs on R-1830s and R-2800s took care of the altitude problems while climbing and descending. We'd move the mixture to the "Auto-rich" detent before takeoff and after cruise power was set it would be moved to "Auto-lean." Next time we touched the mixture was when the gear went down, back to Auto-rich for a possible go around. Since this is 1930's technology I'd say we've had the technology for 80 years.

[Zaphod Beblebrox]

Marker Inbound is dead on correct. The history of the Bendix-Strombourg carbs with auto mixture control goes back to prior to WWII.

Aircraft Carburetors and Fuel Systems: A Brief History - 08 (http://www.enginehistory.org/Accessories/HxFuelSys/FuelSysHx08.shtml)

You just don't find auto mixture on small engines.