Getting the Lead Out

[hharney]

Originally Posted by kilr4d

I think it's also worth noting that the Cirrus SR20 is powered by the TCM IO-360-ES. Highly unlikely that there would be a fuel change that grounds the SR20 fleet.

Apart from the fuel pump and prop governor it's basically the same engine as our Skymasters....

New SR20 has a Lycoming

[kilr4d]

Originally Posted by hharney

New SR20 has a Lycoming

Yes, but there's 18 years worth of TCM powered SR20's. Almost 1500 aircraft.

[YankeeClipper]

To aid in the information flow, the FAA presentation at AirVenture 2017:

https://www.faa.gov/about/initiative.../PAFI_2017.pdf

[hharney]

https://www.avweb.com/eletter/archiv...t=email#231381


Scroll down and find the layman's version of the current issues with the unleaded fuel replacement program. Sounds like things got a little sticky at the presentations in Oshkosh. Now the FAA says they are out of money and the original two companies that had been selected have to let more participants into the private party. What a mess.........

[n86121]

All combustion engines suck in fuel and air, misting the fuel to get the right ratio, light it off with a spark then blow the expanded hot gasses out the exhaust.

Everything else is merely a refinement of that formula.

My son has a highly modified race car. Oversize the turbo. Put a fat 3 in exhaust so it can breathe easier. Some larger injectors, and fuel pump. Reprogram the ECU on a dyno, and all is well. 350 HP out of basically a 120 hp engine.

So it would seem to avoid detonation, one could change the timing on our farm-tractor aircraft engines to accommodate lower octane fuel. While they may not put out exactly the same HP as before, no detonation issues.

Maybe you only get 180HP out of a 210 hp engine?
Maybe you can't go to 30k anymore.

So you de-rate the whole aircraft performance to what the engines CAN put out.
Better than writing off the whole asset.

The experimental guys basically have to do it.
While their engine performance is known,
the capabilities of the aircraft have to be found out empirically
given whatever engine is on it.

So like that, just go the other way.

Yeah, yeah, I know, FAA would never allow that. Blah blah blah..

BUT, subtract the bureaucratic impediments, and the physics seem undeniable.

An aircraft declared experimental is not bound.

What am I missing?

[JimC]

Originally Posted by n86121

What am I missing?

You didn't miss anything on the physics side. It's sound logic. It's the FAA that'll getcha (surprise!)

"An aircraft declared experimental is not bound." This is correct, but it is very difficult (bordering on impossible) to convert a certified aircraft to a usable experiential. Yes, you can move it to experimental R&D, but your operating limitations will be extremely restrictive. You can't get to experimental A-B without redesigning and rebuilding 51% of the aircraft. That's where all the homebuilts are.

[YankeeClipper]

Wouldn't it be better to hold out until they develop something that maintains current power, safely? I'm not sure I'd be shopping for a plane through this forum any more if I thought there were alternatives that didn't need de-rating.

Also, my reading suggests there are other considerations beyond detonation being addressed, such as erosion of parts that hold up fine in 100LL (not because of the lead itself). Non-linearities in combinations is another, as mentioned in the AVWeb write-up.