---------------------------------------------------------- Yak-List Digest Archive --- Total Messages Posted Sat 08/13/22: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:27 PM - Yak 55M - Change in vibration when swapping props (Royden Heays) ________________________________ Message 1 _____________________________________ Time: 12:27:39 PM PST US From: Royden Heays Subject: Yak-List: Yak 55M - Change in vibration when swapping props I changed from the Russian 2 blade prop to the 3 blade MTV 250 diameter prop. With the 2 blade, general engine to airframe vibration as perceived in flight from the cockpit was proportional to engine RPM as expected. The prop was dynamically balanced. Albeit, vibration is a lot more than sitting behind a Lycoming in a Decathlon. I have never flown any other Yak 55M so have nothing to gauge. Engine mounts were new. With the 3 blade and stock M14P governor, vibration was very different from the 2 blade in the 70% to 85% RPM range. The vibration becomes harmonic in that range akin to a twin with RPM out of sync. The beat frequency is, I guess, around 3 or 4 cycles per second (Hz) and increases as PRM approaches 85% at which point it becomes imperceptible. After a dynamic balance there was no change. I wonder if it is the governor? I have read from Richard's website that the stock Russian governor is somehow underpowered for the MTV 3 blade. But I don't know the symptoms. Any comments. Have others had this problem?? Maybe this is just a feature of changing to an MTV, whether on a Sukhoi or Yak 18T? Royden Heays ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message yak-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Yak-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/yak-list Browse Digests http://www.matronics.com/digest/yak-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.