Its hard to make an aircraft purchase decision on one factor like AP availability. Well maintained the M4 or SPZ will serve just fine and both can be supported.

The biggest factors in our decision on Mu2 revolved around its relatively miniscule footprint (fitting in a municipal hangar), it was 100knots faster than the owners previous plane, high wing (guess what he owned before). The fact that its built like a tank, easy to work on and maintain are huge bonuses.

They use Nut-Plates for every piece of mounted equipment and that alone won my heart!

I want one in the worst way...

I know where you can get a great one that is listed at $375K...

How is the interior sound level in the MU-2 in cruise?

Comfortable conversation without headsets?
Any absolute sound level measurements to judge possibility/likelihood of hearing loss for kids in the back?

I wouldn't say its atrocious...

But kids should use headsets.
On our short body (ad listed in OP) the noise really peaks right behind the pilot seats in the area of the prop arc. I did a recently 45 minute flight sitting in the back without headsets and it was fine.

There is a reason that the manufacturers went from three blade 2000 rpm props to four blade 1591 rpm props. The noise reduction that accompanies the slower four blade prop is enough so that many of those aircraft do not even have headset jacks in the cabin as the pax can do without. In contrast, many of the three blade 2000 rpm aircraft have headset jacks in the cabin because pax find it a requirement.

I found this first hand in the Merlin lineup and second hand info in the MU2 lineup.

Agreed. In my Marquise (long body, sale posting in the for sale forum), you really don't need headsets anywhere. I would say the noise is comparable to what you get in a turboprop commuter airline (Saab 340, Jetstream, etc.). No one in the back wears headsets. I'll wear a headset for takeoff/landing/approach airspace. In cruise I take it off and just listen to the speaker. Can talk to the copilot seat at normal voice.

I find the interior noise to be quieter than all but the newest King Airs. Significantly quieter than any piston single or twin (including the 421).

No question that the 3 blade MU-2s have louder interior noise than the 4 bladers, and the short bodies tend to be noiser in the cabin than the long bodies. I think its because the wing (and props) are farther back in the long body... Short body props are up near the cockpit (but not as far forward as a King Air).

I would say the same. I have ridden in the back of a Solitaire without headsets, and it was not bad. But I would want headsets if I were to do it often and for long periods.

Better than my 340 was, though not dramatically.

Yes, I have a stockpile of M4D stuff. About a dozen primary servos, 3 slip skid sensors, 2 trim servos, 1 computer box with cards, 2 control heads, 3 altitude cans, and misc stuff. Much of it came from a complete system I bought out of a 421.

I basically buy anything reasonably priced that is M4D off Ebay.

Yet, in 7+ years, I've replaced only two servos, nothing else has broken. One servo was a rebuilt bought through my mechanic ($3K) and another was a benched check servo from my stock. So the autopilot has been more reliable than I feared. Now I have about 5 boxes full of M4D stuff, and have made little use of it.

Mike C.

Sounds like good insurance and good luck!

Noisier in cockpit, less in passenger compartment.


It is a headset airplane. I have 7 Zulus, one for every seat.


These results were AFTER a sound deadening kit was installed in a K model (short body, very similar to mine).

I don't have numbers BEFORE the kit, so I would assume the numbers are 5-8 dB higher. The kit gets pretty good reviews. I have not done it since ANR headsets do the trick.

(SIL info: http://www.engineeringtoolbox.com/speec ... _1138.html)

If quiet is what you seek, then the MU2 ain't it. I would like it to be quieter, but I accept it to get the performance, economy, and robustness it offers.

Every plane is a trade off.

Mike C.

Thanks, Mike. Anyone have data on the long body/4-blades?

Quieter than (or even as quiet as) a 421 would be a huge positive factor for us, and probably enough for me to be willing to pay the 4-blade calendar expenses.

The only real way to know is to fly in both a 421 and an MU2 and decide.

Even if someone claims to have made measurements in each, there are so many variables in how you make such a measurement that it is unlikely the numbers truly correlate to passenger experience.

Mike C.

I've tried measuring sound level with an iphone app and found it did no help in terms of quantifying the passenger noise experience.

My wife says the MU-2 has a lower noise level than the C421. To me, it seems similiar, if not slightly higher than the 421. You can easily talk to each other in the back. Once I put ANR headsets in the back, they use them all the time. The benefits of ANR, XM Music and intercom make it very desireable.