Piper M600 grounded for wing spar issue

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Final Approach
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San_Diego_Pilot
http://www.flyingmag.com/wing-spar-issue-grounds-piper-m600-fleet

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Piper has grounded the in-service fleet of M600 single-engine turboprops after production workers identified a section of the aft wing spar that did not meet designed measurement tolerances. Piper notified the FAA of the discrepancy and ordered wing spar inspections to determine if the issue affects other airplanes, according to Piper CEO Simon Caldecott, who provided an update at EAA AirVenture in Oshkosh, Wisconsin, this afternoon.

“An issue with a vendor-sourced part was discovered in the wing,” he said. “Piper voluntarily decided to issue a mandatory service bulletin out of an abundance of caution. We hope to get the fleet back in the air very shortly.”
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Remind me again what's the difference between an MSB and an AD when it comes to non-commercial part 91? Does having a turbine engine versus piston engine affect that legality? Someone mentioned to me, certain things become mandatory when you fly with a turbine bolted on, versus remain optional when you fly with a piston bolted on, but I'm not spun up on the differences as a bottom feeder of this avocation...
 
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I almost break out in hives when I see a photo of a M600, TBM 900, or PC-12.

:D

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M600_June2016-navigation.jpg
 
I almost break out in hives when I see a photo of a M600, TBM 900, or PC-12.
The design aesthetic of these large single engine props is a challenge. I tend to agree on the Meridian and PC-12 line but the TBM's proportions seem better with some more stylistic elements to it

In general though, even something like the Saratoga or Six or Lance (or whatever) don't really seem to pass Boeing's "looks about right" rule. Beech got their proportions much better as did Mooney. Other than the Cardinal I won't even talk about high wings here... :D
 
The design aesthetic of these large single engine props is a challenge. I tend to agree on the Meridian and PC-12 line but the TBM's proportions seem better with some more stylistic elements to it

In general though, even something like the Saratoga or Six or Lance (or whatever) don't really seem to pass Boeing's "looks about right" rule. Beech got their proportions much better as did Mooney. Other than the Cardinal I won't even talk about high wings here... :D

I hate the turbine exhaust pipes, can't they both hide them and make the plane more aerodynamic?
 
I hate the turbine exhaust pipes, can't they both hide them and make the plane more aerodynamic?

It's somewhat minimal, but not irrelevant. ~5-10% of thrust is attained by the exhaust pipes on turboprop applications. More importantly though, that equivalent horsepower shaft rating they like to tout? It uses the combined thrust from the fan (prop) and exhaust nozzles, via conversion math for the latter, in order to rate the engine. So attenuating the exhaust architecture for cosmetic reasons also affects the engine rating. Not gonna happen...
 
It's somewhat minimal, but not irrelevant. ~5-10% of thrust is attained by the exhaust pipes on turboprop applications. More importantly though, that equivalent horsepower shaft rating they like to tout? It uses the combined thrust from the fan (prop) and exhaust nozzles, via conversion math for the latter, in order to rate the engine. So attenuating the exhaust architecture for cosmetic reasons also affects the engine rating. Not gonna happen...

You are right about 10% of the HP of the plane comes from the exhaust, but does not at all factor into the rating of the engine for the Piper aircraft. The M500 is rated 500 HP measured by torque at the propellor, the thrust from the stacks is an additional 50HP, giving an ESHP of 550 (so the extra 50 is not counted in any advertising). In the M600, same thing, 600HP at the prop, the additional 60HP resulting in 660 ESHP is not counted. I like the stacks btw. They are ceramic coated and never discolor or corrode like most stacks.

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If they use the manufacturers recommended maintenance program (as I'd imagine almost every 135 operator does), then the time limits set by MSBs are mandatory.

This is true. However, ops specs do vary depending on the FSDO and depending on the operation. For example, most 135s operating pistons comply with all the service bulletins for the engines and props, but not necessarily airframes. That's why most 135s have to overhaul props and engines at TBO (be it hour or calendar). However there are operators (such as Cape Air) who manage to work out arrangements with their FSDOs to run the engines way past TBO. I think they're getting around 3,000 hours between overhauls on their TSIO-520s, for example.

There are a lot of assumptions with 135s about what applies to them all, but it's important to also understand that while many things apply to most of them, they do not necessarily apply to all.
 
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