This week Im getting to have some fun with the Hartzell team in Piqua Ohio, otherwise known as "Propeller Town." Ive been flying a very new and unique prop for them, designed by the infamous Les Doud that you often see on these forums. They are getting ready to make it publicly available. The blade design is an 8301-3 and as I mentioned in another post, its a game changer in my book. Why? Its the first composite prop of any kind, that performs on par with any of the metal props that have been the mainstay of our planes. Ive had many an opportunity to fly lots of props on my plane. But I digress, not the purpose of this post. I wanted to share with you what they do when they prepare to certify and release a product. Stress analysis. Not all propeller companies do this of course. But its one of the reasons why when a Hartzell prop goes on a plane, you have confidence that its highly engineered and well tested with the best of R&D with decades of experience. Particularly in our case as homebuilders, we do a lot of things that can influence the harmonics of a propeller. Hartzell likes to capture data with some of these differing items. Electronic Ignition is one of those items. High compression is another. I have Dual Ei and higher compression and a good candidate to stress test this combination.
The fist step is the special prop. They take a prop and outfit it with sensors. Being the geek that I am, Im fascinated with the
how. Little electronic strain gauges are placed in the prop at various stations.
Here is a closeup of the blade root. I thought this was a work of art in itself.
The second piece is the system that these sensors talk to. Mounted in the aft baggage.
Then I get to do my job. Go fly the plane through a series of profiles defined in their test plan. Various RPM's, MP pressures, speeds, climbs, descents, G's, acceleration tests (hard idle to full throttle back and forths
), Vx climbs to 10k', descents at 6k'/min, and so on. I had a ball abusing this prop. That poor governor. The acceleration testing reminded me of some of my rejoins during the air show. Abusive!
We go through a few of these flights as they download the data, review it, and decide where the prop got the most abuse. Then we go focus on that and do it again. More abuse. Sweet! Lets do it!
In the end all that gets plotted and painted in their fancy software and it goes along with the certification process. Just one step in the long process of certification and performance testing. Its an honor and a privilege to work with such a fine group of people. Its like going to an advanced engineering college class, being an intern, then being told, now go beat this thing to death. A great part of my job.
How Hartzell Tests a prop
Linear Mode
