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Speed?

F

F1 Rocket

Well Known Member
It was pretty smooth this morning and I logged the following data:

N14ZM
24"/2400 rpm
Altitude OAT Density ALT IAS TAS GPS avrg
3000' 25C 4900 167 180 188
6000' 20C 7800 168 189 199

21"/2400 rpm
10000' 14C 11800 159 191 201

It looks like my airspeed indicator is reading aprox 10 knots low. Other than that do these numbers look ok?
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The IAS and TAS look close to what I would see in my F1 with a 250 HP IO 540 and 3 blade MT. If your GPS runs were done correctly and are accurate you might want to look for a static leak INSIDE the plane or consider putting some type of airflow disrupter just in front of the static port.
 
Last edited:
Flo-Max...

Danny,

Congrats!!!! Numbers look good, what type Pitot tube do you have, bent tubing or a store bought Cessna type?

Smokey
 
smokyray said:
Danny,

Congrats!!!! Numbers look good, what type Pitot tube do you have, bent tubing or a store bought Cessna type?

Smokey
Click to expand...

I have the Dynon pitot mounted on a Gretz Aero mount. The Dynon design has a built in drain so it always has a leak at the pitot head. The rest of the pitot system is tight. I have checked the static system for leaks and it is tight. The static ports are flush mount ones from Cleveland Tool located in the rear fus. I've noticed they have changed the design on these so they mimic the Vans pop rivet type static ports.
 
F1 Rocket said:
The static ports are flush mount ones from Cleveland Tool located in the rear fus. I've noticed they have changed the design on these so they mimic the Vans pop rivet type static ports.
Click to expand...
I have communicated with several RV builders who had ASIs reading approximately 10 kt low caused by flush static ports. Two of them modified the static ports by gluing something on the outside to achieve a similar external contour to Van's pop rivet design - they reported that the airspeed error was very, very small after this mod.
 
Is the TAS a calculated EFIS number that is displayed and you wrote down? Or you calculated it?
 
Kahuna said:
Is the TAS a calculated EFIS number that is displayed and you wrote down? Or you calculated it?
Click to expand...

TAS was as displayed by the Dynon EFIS. I suppose it could be off but the only thing I can think of that would make it inaccurate is if the OAT was off. If there is something else please let me know. My OAT probe is mounted in the rear part of the tip rib. I mounted there becuse it is open to the outside air but shielded from direct airflow. I have checked it against a known thermometer and it is always within a degree or two sitting in the hangar. It does get pretty warm in the sun but it cools down once you get moving.
 
Mine reads about 10 knots low with the flush ports as well.

BTW, I've flown Dannys F1 and it really hauls (but at least it's quiet and smooth)! One of the fastest F1's around.

bob
 
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