CESSNA LSA

On 8-Aug-2006, wrote:

Yeah, I really meant the parrot which is about 115 knots with 120 hp.


--If you believe in miracles. By the laws of aerodynamics, for a given
airframe (i.e. same drag characteristics) the airspeed in level flight will
increase as the cube root of the increase in power. According to the cited
webpage, the Parrot cruises at 75% with a 100 hp engine at 115 mph (100
kts). They PROJECT that 75% cruise speed will be 130 mph(113 kts) with a
120 hp engine. But according to the cube root law, you would need to
increase engine size to 144 hp in order to get 75% cruise to increase from
115 to 130 mph. In order to do it with only 120 hp you would have to have a
miraculous increase in propeller efficiency (not likely, and anyway you
can't do better than 100%) and/or a huge reduction in cooling drag (also
unlikely). More likely, 75% cruise with the 120 hp engine will be around
122 mph (106 kts).


-Elliott Drucker

actually...according to one sport cruiser dealer......the Sport Cruiser is
distributed by the same distributor as teh Sport Sting, which has a much
higher price tag. The distributor, on purpose, de-rates the Cruiser's speed
to improve the sales on the Sting.

I'll let you know. I'm flying a Cruiser next week.


wrote in message
news:Rd8Cg.17729$Qu4.9630@trnddc04...

On 8-Aug-2006, wrote:

Yeah, I really meant the parrot which is about 115 knots with 120 hp.


--If you believe in miracles. By the laws of aerodynamics, for a given
airframe (i.e. same drag characteristics) the airspeed in level flight
will
increase as the cube root of the increase in power. According to the
cited
webpage, the Parrot cruises at 75% with a 100 hp engine at 115 mph (100
kts). They PROJECT that 75% cruise speed will be 130 mph(113 kts) with a
120 hp engine. But according to the cube root law, you would need to
increase engine size to 144 hp in order to get 75% cruise to increase from
115 to 130 mph. In order to do it with only 120 hp you would have to have
a
miraculous increase in propeller efficiency (not likely, and anyway you
can't do better than 100%) and/or a huge reduction in cooling drag (also
unlikely). More likely, 75% cruise with the 120 hp engine will be around
122 mph (106 kts).


-Elliott Drucker

wrote in
news:Rd8Cg.17729$Qu4.9630@trnddc04:


On 8-Aug-2006, wrote:

Yeah, I really meant the parrot which is about 115 knots with 120 hp.


--If you believe in miracles. By the laws of aerodynamics, for a
given airframe (i.e. same drag characteristics) the airspeed in level
flight will increase as the cube root of the increase in power.
According to the cited webpage, the Parrot cruises at 75% with a 100
hp engine at 115 mph (100 kts). They PROJECT that 75% cruise speed
will be 130 mph(113 kts) with a 120 hp engine. But according to the
cube root law, you would need to increase engine size to 144 hp in
order to get 75% cruise to increase from 115 to 130 mph. In order to
do it with only 120 hp you would have to have a miraculous increase in
propeller efficiency (not likely, and anyway you can't do better than
100%) and/or a huge reduction in cooling drag (also unlikely). More
likely, 75% cruise with the 120 hp engine will be around 122 mph (106
kts).


-Elliott Drucker

It could also be the efficiency of the "100 hp" Rotax comparted to the
120hp Jabiru. Cooling drag WILL come into effect as the Rotax is water
cooled and generally not well baffled in the engine compartment except
for the radiator.

Also for some reason they want to put a 3 blade propeller on these Rotax
LSAs, and I mostly see 2 bladed props on Jabirus.

Maybe wont make up the whole difference, but time will tell I suppose.

--
-- ET :-)

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