EX2 cruise vs EX3 (Vno)

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Hi All

I would just like to find out why the EX3 has a Vno (bottom of the yellow arc) of 141mph I believe and the EX2 has a low Vno of 101mph.

How come it is so low on the EX2 ? I see even the original PA18 had a 122mph bottom of the yellow arc. Surely with a Constant speed system on the EX2 you would exceed this limitation in the cruise which seems very limiting.

Regards

[Pete D]

Different aircraft for different missions. Each aircraft has structure optimized for it's configuration.

The EX2 is only offered in fixed pitch configuration.


LSA Carbon Cub SS gross weight 1320, typical empty weight approx. 9xx, Vno 101, Vne 141 *fixed pitch only
EAB Carbon Cub EX2/FX2 gross weight 1865, typical empty weight approx. 1xxx, Vno 101, Vne 141 *fixed pitch only
EAB Carbon Cub EX3/FX3 gross weight 2000, typical empty weight approx. 11xx-12xx, Vno 140, Vne 170 *constant speed prop standard
weights in lbs, speeds in mph

Higher gross weights and speeds equal higher empty weights.

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Hi Pete

Thanks for the reply but I see in all the write ups, forums and aircraft demos the pilots fly well into the yellow arc in the cruise and publish it. Indicated airspeeds above 120mph. Do the EX2 owners comfortably cruise in the yellow ? Would you advise that if the prop is pitched for it ?

Regards

[Narwhal747]

Hi Pete

Thanks for the reply but I see in all the write ups, forums and aircraft demos the pilots fly well into the yellow arc in the cruise and publish it. Indicated airspeeds above 120mph. Do the EX2 owners comfortably cruise in the yellow ? Would you advise that if the prop is pitched for it ?

Regards

I only have 3 hours in an FX2 from this summer vs 300 or so in my FX3 but with the standard Catto prop the FX2 would cruise at about 110-115 MPH indicated at 2500 RPM at 2500-4500 ft and around 12-13 GPH fuel burn (running 200 F rich of peak due to the high power setting). As you stated this was in the yellow arc but fine in smooth air or with very very light turbulence. I flew it through some mountain passes and just backed it off to 2300 or so which was enough to slow it into the green arc when things got turbulent. 2300 RPM/100 MPH IAS was also a much more efficient speed in terms of fuel flow since you could pull it back to around 6-7 GPH and cruise lean of peak there without any engine roughness on the Titan 340 engine. Of course you'd probably need to pull back even more if you had an EX2 with the cc363i. As Pete stated there are structural differences between the 3 and the 2; this FX2 weighed about 1080 lbs empty on 31's vs my FX3 which is right at 1200 lbs with the same tires (granted I have IFR avionics, safety cables, acme shocks on every gear including the tail, the factory float kit as well as the typical FX3 fuselage differences). The 2 was definitely happier to fly short final approach in the high 30 MPH indicated range with only a little bit of power, just me and partial fuel vs the 3 that gets a little nose high and needs some significant power to get the nose high enough for those speeds.

IMG_0152.jpg

[Pete D]

Operation in the yellow are are allowed but must be conducted with caution and in smooth air per the AFM Template. Normal operating range is considered 40-101, green arc. (EX2)

airspeed markings.jpg

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Hi 747

Thank you for the Gen , I know it comes from a perspective of ignorance but I just don’t like the idea of spending time in the caution range. May I ask if you have a sample weight and balance for your EX3 to see if it would work with an Edge Performance engine from an aft CofG perspective ? Essentially the install removes 50 pound off the engine Bay Area but the CS prop fitted to the EP917 is about 36 pounds which I believe is slightly more than the trailblazer but I could be wrong

Regards

[Andy]

May I ask if you have a sample weight and balance for your EX3 to see if it would work with an Edge Performance engine from an aft CofG perspective ? Essentially the install removes 50 pound off the engine Bay Area but the CS prop fitted to the EP917 is about 36 pounds which I believe is slightly more than the trailblazer but I could be wrong.

The FX-3 forward CG limit is 70.5 inch and aft limit is 79 inch. My IFR capable FX-3 (not factory configuration) has empty mass of 1182 lb and empty CG at 70.7 inch. Most of my flying is solo and I keep about 50 lb in the aft cargo to put the flight CG where I like it. (case of water, tool bag, hiking boots, etc). With full fuel that's 75 inch which is very close to mid CG.

I have a calculated loading that puts the CG at the aft limit but have never actually loaded that way. Aft limit in my aircraft takes full fuel, 160 lb front seat, 170 lb rear seat, 100 lb fwd baggage (limit 100), 60 lb aft baggage (limit 60). That's not an unreasonable load for 2 people on a camping trip. With me in the front seat I hit aft CG limit before I reach max gross.

I revised my empty mass/CG by removing 50 lb at 15 inches (wild guess at the difference for the proposed engine change). That hits the aft limit with full fuel, 160 lb front seat, zero rear seat, and max load in both baggage areas. Also hits aft limit with 160 front, 170 rear, 60 forward baggage, 30 aft baggage.

If 50 lb reduction at 15 inch is reasonable then it looks like you'd need to add ballast forward of the firewall to have a useful loading. You'd need the exact mass and cg for each engine/prop to come up with real numbers.

[Andy]

but the CS prop fitted to the EP917 is about 36 pounds which I believe is slightly more than the trailblazer but I could be wrong

It's hard to find weight data for specific models of the trailblazer but one source says 43 lb.

https://hartzellprop.com/wp-content/...-HOMEBUILT.pdf