Engine/prop question

[dasha149]

Hello ez drivers, Is someone in the EZ community flying with a constatnt speed prop? I am contemplating a 320 B3B that is set up for that - would it be a mistake to go this route because of weight considerations? Thanks,  David

[dave]

hello dasha,
  the only constant speed prop i know that is used (rare)  is an MT from germany..$10k....but if you look at the RAF plans....they do mention that constant speed props are bad for EZE's..(pushers)...
   its best to use what the industry has been using...just look at the racers..

[Waiter]

I have a MT constant speed. But it’s electric rather than hydraulic.  Double-check the clearance of the prop governor, to make sure you have room. I like the electric, because it was an easy retrofit, just run two wires. I also like the fact that I can run it in the “Variable Pitch” mode. This is nice for long cross countries, when I hear the engine rpms changing, I know something’s up.

The O-320 I have was originally configured for a hydraulic prop (1955 Apache), but I relocated the crank plugs so I could use a fixed pitch wooden prop.

The only problem I have, it spoils you.  I can get into and out of places that wouldn’t be possible with my old fixed pitch Great American.  I also like the fact that I can cruise along at 170 kts while turning only 2300 RPM. With the fixed prop, I could see 175 kts, but only while turning  2900 RPM.

A constant speed prop makes an EZ the plane it was designed to be.

Waiter
 

[Waiter]

I think Dave is refering to the use of Metal props. The problem with metal props is resonant frequency.  You've seen the wine glass get shattered by a tuning fork. The problem, unless you do significant resonance testing of your specific airframe / engine / propellor combination. Your EZ may emulate the wine glass. :shock:

The MT prop is a wooden substrate. Although wooden props also have resonant frequencies, they just can't generate the power required to do any damage.

Waiter

[Waiter]

I think Dave is refering to the use of Metal props. The problem with metal props is resonant frequency.  You've seen the wine glass get shattered by a tuning fork. The problem, unless you do significant resonance testing of your specific airframe / engine / propellor combination. Your EZ may emulate the wine glass. :shock:

The MT prop is a wooden substrate. Although wooden props also have resonant frequencies, they just can't generate the power required to do any damage.

Waiter