Aircraft Silencers

[flickoff]

I own an aerobatic aeroplane which is allegedly noisey. In my view aircraft like motorbikes and sports cars should be noisey, but this is not a view shared by the locals and more importantly the bloke who owns the airfield. He has "suggested" fitting a silencer to it. I understand West London Aeroclub are marketing such a devise, but it has not been certified for an AEIO360.

Does anyone out there have any experince or comments about fitting the thing to an AEIO360.

Do they actually work or is most of the noise from aircraft doing aeros from the prop. If so would a plastic MT type prop. make any appreciable diffference to the volume. I am happy to fit one of these but not some unapproved box of tricks which may or may not damage my engine!

If you don't want aircraft noise, don't live near and airfield!

[stiknruda]

Ah, Flickoff dear chap!

I was discussing the suject of noise from our similar type aircraft at the w/e with PFA's finest (JT) at EGBG.

I have an MT (wooden core) on mine and a Kevin Murray tuned 4into 1 exhaust which emanates in an eff off megaphone.

JT and others (inc the chap who just rebuilt yours!) were adamant that my combination was one of the quietest around.

The 2 others that I am v familiar with are far noisier than mine (KDR AWZ).

Do you run the factory std x-over 4 into 2?

I would have thought that there were noisier aeroplanes operating out of your home base - or have one of you just pissed off airport management? I don't know but maybe something like a roll on take off, might not be the best way to make friends?

Be good - are we still on for Eire?


Stik

[Mark 1]

Propeller noise is highly sensitive to tip speed (specifically tip relative Mach number), but exhaust noise is only approximately linear with power output. So as you go up in RPM for a given prop diameter the propeller noise will eventually dominate exhaust noise.

If you have a constant speed prop, then using a lower RPM and higher MP will generally be quieter, and a 3 or 4 bladed prop of smaller diameter will likewise be quieter at the expense of reduced static thrust.

In Germany, where the noise regs are more severe, you see a lot of exhaust silencers and 4 bladed props.

Balanced exhaust systems seem to improve power output, reduce noise and reduce shock cooling problems - its a pity they also weigh more.