No More Grease Spots

This picture of the Whirlwind 151 (taken on an overhaul stand) clearly shows the snap ring that retains the shims holding tension on the blade. Pop that off, replace the shim, and no more leaks!

About halfway to Oshkosh last month, I started to notice spots of grease appearing on the canopy of our trusty RV-3. I've seen oil leaks before, and this wasn't one of those - this was grease, and the only place that could come from was the prop hub. I've also seen grease leaks before, and one thing the do share in common with oil leaks is that a very tiny amount can look much worse than it is. So I wasn't too concerned about it, cleaned the canopy at the fuel stops, and finished the tip to the show. Of course, I knew exactly where I could find the Whirlwind guys for the next week. AirVenture - what better place to have a technical issue? Continue reading "No More Grease Spots"

Simple Pitch Adjustment for DUC Hélices Prop

The Viking Engines display included this very interesting DUC Hélices ground adjustable prop from France. Why so interesting? Blade pitch is adjusted by inserting an allen wrench into the center of the hub; a twist of the wrench rotates all three blades at once, in sync.  Continue reading "Simple Pitch Adjustment for DUC Hélices Prop"

Propellers Suck

Hamilton Standard propeller on Douglas DC-3 Photo: By Z22 - Own work, CC BY-SA 4.0

No, I'm not being nasty - I’m just finishing up studying the material for the FAA's A&P Powerplant knowledge exam, and finding out all sorts of interesting things that the FAA wants me to know about propellers. Interestingly, some of them are actually true!  Well, truth is sometimes a matter of which vocabulary you are using, but when it comes to an FAA knowledge test, theirs is the only one that counts! Continue reading "Propellers Suck"

Prop War?

Whirlwind composite prop on David Sterling’s Lancair
This Whirlwind composite on David Sterling’s Lancair is the latest go-fast prop in the Reno Sport Gold pits.

For years Hartzell has ruled the roost in Sport class racing around the pylons at Reno. Their "race prop," as it’s universally called, has been found faithfully propelling nearly every front runner Glasair and Lancair for over a decade and it’s responded well as race speeds have steadily climbed. Continue reading "Prop War?"

Test Mule PSRU

Test mule prop speed reduction unit (PSRU)

Here's an interesting idea, a test mule propeller speed reduction unit. A very wide belt tension adjustment range allows the installation of almost any drive pulley diameter, thus many different reduction ratios (and matching propellers) can be test flown without major modification. Continue reading "Test Mule PSRU"


Even though I understand and am a big fan of dynamic power plant balancing, it never ceases to amaze how much difference it can make in an airplane that you have gotten used to before it is balanced - or rebalanced. Generally speaking, once you've done a good job of dynamic balancing, the airplane should stay smooth until something changes - a prop removal or overhaul, significant engine work, or a prop leading edge cleanup. But things wear and change gradually over time, and the slight change in balance goes un-noticed as the airplane just reverts to what we'd call "factory roughness" - the amount of imbalance that is acceptable for a mass production job, but that just isn't quite as good as it could be.

Dynavibe RV-3

Continue reading "Smooooth!"