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Tom

Real World Cruise Speeds

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<... I want an airplane engine in mine ...>

Time to carefully examine what you're giving for what you're getting.

I could build my whole dream plane for less than what you'll pay for a TIO-540. Kind of doubt a TIO-360 will hack it at all.

Have fun. Good Luck .... Jim S.

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Jim,

 

Those numbers you mentioned that you and Phil went through, are they essentially the same ones Phil has on his web site? If not, can you post a summary of them?

 

I had ruled out RG as being too expensive for what it gives (~15 kts). If this is not the case I may have to reconsider.

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360 is it, just hope it is a two stroke, fuel inject, auto prop, single lever, turboed diesel

 

Mike

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>I am inclined to go with John Slade and Greg Richter and ignore takeoff and climb performance, setting up the prop exclusively for high end cruise...

 

I met with Greg yesterday. Did you know he is swapping out his rotary for a turbine? He doesn't even have wheel pants on his Cozy III. He invited me back to fly the new setup in March, so I guess we'll see about that "reduce drag" vs. "increase HP" argument. :D

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Rui,

<... numbers you mentioned that you and Phil went through, are they essentially the same ones Phil has on his web site ...>

The stuff I discussed with Phil had to do with spar structure. The Infinity gear is mounted on the forward face of the spar box. At touchdown, the impact generates a largish monent that would tend to twist the leading edge up. On braking, the stopping force applied to the spar through the gear leg is a large moment in the leading edge down direction. I was wondering what manner of reinforcement would be required to prevent possible damage - like a couple of spiral plies of uni on the spar carry-through. He pretty well convinced me that it was not a big issue.

 

<... ruled out RG ... too expensive ... gives (~15 kts) ...>

It might be the easiest 15 kts you ever buy. getting 15 kts with power can get hideously expensove. Suppose you went from 180 kts to 195. 195/180 = 1.083333. 1.083333^3 = 1.27 (1.083333^4 = 1.38). You will need to increase your power by 27% (if weight, etc. didn't change with power increase) to maybe 38% if weight did increase. From a 200 hp engine to start, that's 54-76 hp increase. That big an increase could get pricey. Doing it with other drag reduction mods can be slow going - you do this mod and then that one and pick up a knot or two each time. The faster you get, the tougher those kts are to come by.

 

As for performance estimates, the numbers on Phil's web site make sense to me. Nobody knows for sure since each airplane is unique and at that level, tiny deviations from optimum cost a lot.

 

If it was easy, everyone would be cruising 250-300 kts ... Jim S.

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Marc said

___________________________

 

Nat didn't see this on his plane, but it's not at all clear that his installation was ever developing full power, or that he had the appropriate propeller for the Franklin. I wouldn't use his installation as an indication.

___________________________

 

Talked to Nat and he did optimize for the franlkin, started with a new prop designed for 220 hp, couldn't "get the plane off the ground" with it

 

Went back to the lycoming prop and it worked.

 

Sounds to me that the franklin doesn't develope the hp that it advertises.

 

Thats a new one in the airplane business, all of the adds and performance specs are always truthfull

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I'm no expert but from the one ride i had with the plans built plane, lycoming 360 75% power, cruise ias 210@6000 feet and 1100 fpm climb from 3000 to 6000, tanks almost full, front seat weight about 216+160

 

Mike

If I get those kind of figures with the kind of plane I hope to build, I will be pleased.

Cozy Mk IV - Loaded Panel, and a few extra electronics gadgets.

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You can also go the Cozy site and see what owners claim they are getting from their aircraft. 180 MPH+ cruise does not seem that uncommon with 180-200HP powerplant.

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What is it that limits Vne? Is it control surface flutter? Is it structural strength of the whole aircraft?

 

I've seen references to a Vne of 190 kt, or about 220 mph. Anyone care to back me up on that?

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What is it that limits Vne? Is it control surface flutter? Is it structural strength of the whole aircraft?

There are a lot of things, flutter is one of them. Don't forget that as you approach Vne, you should only be operating in smooth air. That is so you do not cause structural damage to the aircraft.

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Maybe someone can explain this to me. I'm looking at the Velocity website and under the performance chart it says that Vne for the TXL is 200kias but its cruise speed is 250ktas. How can it cruise faster than it's designed to fly? I'm guessing this would make sense if I were actually a pilot.

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Maybe someone can explain this to me. I'm looking at the Velocity website and under the performance chart it says that Vne for the TXL is 200kias but its cruise speed is 250ktas. How can it cruise faster than it's designed to fly? I'm guessing this would make sense if I were actually a pilot.

TAS is IAS adjusted for density altitude and temp at that altitude.

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TAS would be the same as groundspeed if the wind was taken into account. Or said another way---TAS is the actual speed through the air (True Air Speed). Once you add or subtract wind---you have groundspeed.

 

IAS is the speed on the airspeed indicator. It substantially fall off with altitude (in space, your ASI would be zero even though you were orbiting at around 17000 mph.

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If you think about it, as altitude increases, air molecules are farther apart. So, at a given true airspeed (TAS) across the ground, fewer molecules are hitting the aircraft (and the pitot tube) the higher up you go. So, indicated airspeed (IAS) will be less the higher you go even though your true airspeed is the same. This might be kind of a backwards way of looking at it, but it works for me!

 

Structural and aerodynamic limits for aircraft are based on IAS because that is how fast the aircraft thinks it is going - based on the number of air molecules that are hitting it. It doesn't matter how fast you are actually moving across the ground.

 

Again, all this is assuming a no-wind scenario. TAS corrected for wind is your groundspeed (GS). Hope this helps.

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