Synchronising is carried out to
- match propeller tip speed.
- match engine rpm.
- match blade phase angle difference.
Explanation from PART66Online
Synchronising adjusts the slave engine's governor so that all engines run at exactly the same rpm as the master, eliminating the slow beat caused by small rpm differences. Synchrophasing, by contrast, goes a step further and sets a fixed blade phase angle; plain synchronising only matches rpm.
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obrien99 asked · 5 Mar 2012
I was a bit unsure with this question, The props are synchronised by matching the engine RPM? but ultimatley this is to match the prop RPM. would you guys agree with this answer?
Community Comments (9)
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PART66Online
5 Mar 2012
I agree with you. Question is a bit complicated. Question bank refers to Jepperson Aircraft Propellers and Control page 132, but I don't have this book so can't check. If someone have it please be so kindly, send it to info@part66online.com
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obrien99
6 Mar 2012
i have got this book i will check and get back to you
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PART66Online
6 Mar 2012
Okay, submit your research here. :)
If you have digital copy of this book, send it please to info@part66online.com
If you have digital copy of this book, send it please to info@part66online.com
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obrien99
6 Mar 2012
"The synchronisation system is normally used for all flight operations except take off and landing. a master engine is used to establish the RPM to which all other engines(slave engines) will adjust"
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obrien99
6 Mar 2012
Still not a clear answer the synchronisation system works by matching all engine RPM's. But by matching the engine RPM the prop RPM should also be matched and therefore tip speeds matched. if the answer was "match prop RPM" i would have gone for that but still not 100% sure.
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PART66Online
7 Mar 2012
Agree, matching engine RPM = matching prop RPM, because reduction ratio is fixed. :) Question is blurry...
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TURIN
16 Mar 2012
This sounds like a piston engine question. A gas turbine engine may have a free power turbine so matching engine speeds is a nonsense. Matching prop speed is correct (in a gas turbine).
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alberto
7 Apr 2013
your right dimky i agree with you. When synchronising engine rpm your synchronising the propeller automatically as the prop have an epicyclic gear system.
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aerorodder1
23 Dec 2015
Obrien99 is correct the engine rpm is reduced or advanced to match the slave engine. On the MD-80 the switch is called "engine sync". If you didn't sync up,the passengers toward the rear of the plain right next to the engines would go crazy on a long flight. When we were kids, we would hum in front of a spinning fan mouths open,and move our noisy mouths until we could make these strange harmonies until would we found the one that would sync up perfectly. But in the interim there would be that specific warbling sound...well select an engine and sync and away goes the harmonics and vibrations. Don't care about props, sorry but if you want to advance in your carrer you'll have to work on turbojet or turbofan high bypass ratio engines.Small A/C has its place but the money is in the jets not props!
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