Sport Pilot Talk

roger lee wrote:“So, placarding not to fly above 120 kts won't do the trick. Instead, you have to determine what engine RPM would result in 120 kts calibrated (not indicated) airspeed, at sea level, on a standard day (+15 C, 29.92 in hg, zero relative humidity), and then mark that RPM on the tach with a yellow line, and never exceed that power setting except briefly for takeoff.”

Then what a waste of a turbo and money to get you there.

Probably, but maybe not if you fly at high altitudes where a normally aspirated engine loses a lot of rpm.

roger lee wrote:“So, placarding not to fly above 120 kts won't do the trick. Instead, you have to determine what engine RPM would result in 120 kts calibrated (not indicated) airspeed, at sea level, on a standard day (+15 C, 29.92 in hg, zero relative humidity), and then mark that RPM on the tach with a yellow line, and never exceed that power setting except briefly for takeoff.”

Then what a waste of a turbo and money to get you there.

Not a waste at all. You don't add a turbo to go faster at sea level. You add it to be able to maintain sea level power at altitude. Having sea level power at altitude in the thin air lets an airplane go much faster that the normal increase in true airspeed you get from a normally aspirated engine.

Roger, for me, the whole point of turbocharging is not to fly faster at sea level, but rather to maintain sea-level power at higher altitudes (or higher density altitudes.

<like Tom said...>

Whether it's worth it or not is still a question. LSA are relatively slow and simple airplanes and daytime, VFR only for Sport Pilots and those exercising Sport Pilot privileges and limitations. They can't be used in furtherance of a business, so it's mostly just fun flying. It seems a lot of us are older guys with an endurance of about 2 hours before we need a break.

The turbo-charged engine is a benefit flying faster at higher altitudes, but probably of little to no value flying at low altitudes. For lowlanders, flying with no wind or a tail wind, it would probably be worth-while to climb to higher altitudes to take advantage of the turbo-charged performance and thin air, even for just a 2 hour flight. With a head wind, most would probably stay at a low altitude since winds are usually stronger (but not always) at higher altitudes.

The turbo-charged engine would benefit highlanders almost every flight since they are usually flying at higher altitudes regardless of the wind.

Bottom line, it would depend on the cost. I doubt it would be cost effective unless you live and fly in higher elevations or you have nothing better to do with your money. Obviously, there are exceptions to this generalization.

I’m honestly back and forth on this subject. I have about a 100 hours behind a 914 powered Tecnam P2008, and it’s honestly a love hate relationship. I love that the engine is able to maintain 100 HP up to 16,000ft, but what I don’t love is having to reduce the power at altitude (9,500ft and above) to keep from exceeding maximum continuous RPM. Because of this, true airspeed actually goes down by 4-6 knots up at altitude, even though we’ve got all 100 HP available.

The sweet spot is about 5,500ft where we can obtain 125-127 knots true. With a constant speed prop at and above 10,000ft, that true airspeed goes to 140 knots with only 100 HP. Frustrating!

Well, The FAA says you are not to be trusted with anything more complicated than a ground adjustable prop because , well just because .. so you are stuck ...and what is really frustrating ... I can’t even get around that by upgrading to PP certificate.

Warmi wrote: I can’t even get around that by upgrading to PP certificate.

Well, actually, you can always modify to add a constant speed prop, and fly it with a PP or higher under US rules. Trouble is, it's no longer an LSA, and can never be again. And, you can't change your AWS to ELSA, since it's no longer an LSA. And you can't go to E-AB, since it's factory built. That only leaves experimental exhibition, or experimental R&D, both of which impose too many restrictions.

Easy solution. Get a Private Certificate and upgrade to an OLDER, turbo-charged aircraft. I used to rent a turbo-charged C182RG with flight director. What a cream-puff that was.

To make a turbo worth while you really need to have a variable pitch or constant speed prop. This is why Rotax setup the 914 & 915 for variable or constant speed props, not fixed pitched props. Even at high altitude you would still need to change the prop to be efficient.

roger lee wrote:To make a turbo worth while you really need to have a variable pitch or constant speed prop. This is why Rotax setup the 914 & 915 for variable or constant speed props, not fixed pitched props. Even at high altitude you would still need to change the prop to be efficient.

No doubt, but while not perfect optimization it is still going to have better performance at altitude than a normally asperated engine.

Yes, I agree. The 914 turbo fixed pitch prop combo is still partaking of half the cake. One day we might to get to have the whole thing!

Opened a new thread since this one was for the Turbo.