BeechTalk - BT

Username Protected · **Posted:** 23 Apr 2021, 15:10

Username Protected wrote:

PA-46-600TP
The life limit of the wing assembly, P/N 46W57A100-001 is 3,767 hours time in service

Shirley you jest..? This can’t be right...someone with an M600 tell me this is incorrect...Chuck? Seriously??? The M600 turns into a paperweight at 3767 hours?

Username Protected · **Posted:** 23 Apr 2021, 15:34

According to that document:

The M500 fuselage life limit is 10,145 hrs and it's wing is 13,349 hrs.

The M600 fuselage life limit is 6,143 hours and the wing is 3,767 hrs.

Surely there's an explanation for this. What possible explanations are there for this?

Was the M600 type certificate issued prior to the full fatigue testing completion (a full fatigue test can take a very long time) and an initial test and report issued to complete certification with the intent to continue testing and update the cert basis later?

Was there a fatigue failure that occurred during testing that indicated this low life limit and Piper chose to cert to that limit for now and then make structural mods and retest at a later date?

I'm sure there's a good story behind this. I can't believe that this isn't something that Piper is in the midst of addressing or has addressed already.

Username Protected · **Posted:** 23 Apr 2021, 15:35

The life limit of the tail is 7632hrs. But flying 200hrs/yr that would almost 40 yrs. You would also be on your second set of wings. Are these limits mandatory for Part 91 or are they more like TBO?

Username Protected · **Posted:** 23 Apr 2021, 15:43

Username Protected wrote:

Note this:

PA-46-600TP
The life limit of the wing assembly, P/N 46W57A100-001 is 3,767 hours time in service

Wow that is crazy. I'm not doubting you Mike, but how can this be right and how can Piper not have addressed this? Surely those planes should be flying up to 10,000 or even well past that??

Username Protected · **Posted:** 23 Apr 2021, 15:43

Life limit is an airworthiness thing, so applies to all operators.

The M600 did get a new wing from the M500, so the different time in service limit makes sense. However, that low of a life limit does not make sense. Alarming.

Username Protected · **Posted:** 23 Apr 2021, 15:47

Username Protected wrote:

Like most new planes, this will change over time with more data. This from Piper: "...For the M600 the published limits are based almost completely on analysis and we are currently performing fatigue testing scheduled to continue through 2020 to establish fatigue life limits comparable to the PA-46-500TP."

I will bet anyone the life limits are changed dramatically after fatigue tests.

Well, if the testing was scheduled for 2020 perhaps they’ve done it...and turns out they needed to adjust down based on the results.
After all, the hour limit as shown by Mike C above did go down recently, from 5132 hours to the current 3,767 hours. Why did that happen? Perhaps the testing in 2020?

Username Protected · **Posted:** 23 Apr 2021, 15:48

Username Protected wrote:

For the M600 the published limits are based almost completely on analysis and we are currently performing fatigue testing scheduled to continue through 2020 to establish fatigue life limits comparable to the PA-46-500TP."

That makes a great deal of sense. Certify the aircraft based on accepted analytical methods endorsed by the FAA which yield a higher conservative but certifiable design. Get the aircraft to market and get some cash flow rolling in while you complete the very lengthy conforming article fatigue test and then go back to update the cert basis once you have actual test data.

The downside to this approach is that it's highly possible that the fatigue tests highlight structural deficiencies which require airframe changes for articles already built and delivered. It will be interested to see how the testing goes.

There's no way Piper allows a 3,767 hr wing life limit to remain in effect. If that were the case, sales of new M600's would go into the toilet immediately.

Username Protected · **Posted:** 23 Apr 2021, 16:39

The TBM-700A fuselage was initially 4496 hours. Once a particular operator (Quest Diagnostics I believe) got there with their fleet it was increased until now it is 16,200 hours. A 700A just needs some inspections and a few small mods to get the increased life. Service history has alot to do with these increases, as the mfr can see where issue are (and are not).

The M600's new wing will get increased too as Piper either does more testing or the fleet has more hours. Nothing to get worried about, most new GA aircraft have low life limits initially.

Username Protected · **Posted:** 23 Apr 2021, 18:38

Username Protected wrote:

John's thoughts summarize my take on this as well but his words are much more relevant and powerful since he can provide first hand experience.

Cheyenne's have many nice characteristics as do Conquests but they are still old, old airframes that required a lot of TLC and even if they are well maintained, there is just going to be much more to be concerned about vs. a couple year old airframe. The other big factor there is the passenger experience. Take a non pilot into an M600 cabin and then a Cheyenne cabin. Yes the Cheyenne is a bigger airframe and twin screws but the experience from a non-flyer perspective is night and day.

If you're a non-pilot, which of these inspires more confidence and comfort?

The top one! Look at all the dials and switches!

Oh...you said nonnpilot...

Username Protected · **Posted:** 23 Apr 2021, 18:40

On resale likely to lose more on the newer airframe. MX from what I’ve learned would most likely be a wash if the cheyanne is actively flown and maintained.

Username Protected · **Posted:** 23 Apr 2021, 19:06

Username Protected wrote:

One of the most significant differences between these two choices is acquisition costs and depending on your usage scenario, there's a substantial financial benefit available if it's predominantly business usage.

Assuming the M600 is roughly $2M and the Cheyenne II is $500K, there's a $1.5M delta in acquisition cost. Assuming 100% business usage, that added tax benefit for the M600 is roughly $525K over a 5 year depreciation schedule or roughly $105K per year (assuming 35% tax rate). Obviously you're not entirely avoiding these taxes but kicking the can down the road. What is real is that you have an additional $105K free cash flow available annually for 5 years. Assuming you invest that $105K per year in an S&P500 index fund yielding 10% on average, you earn on the order of $36K per year ($180K over 5 years) in investment income with that added cash flow.

You'd have to do a more thorough financial comparison to take all factors into account but these comments about "$1M buys a lot of fuel / mx" misses the big financial picture.

Can I like and dislike the same post?

Username Protected · **Posted:** 23 Apr 2021, 20:25

Well so far nobody has an answer for why the hour limitation went down. I find that interesting.

Username Protected · **Posted:** 23 Apr 2021, 23:59

Username Protected wrote:

Well so far nobody has an answer for why the hour limitation went down. I find that interesting.

That's the most interesting aspect of the issue. it suggests that fatigue testing or further analysis contradicted the original number. That first number was likely supposed to be a conservative number that would be extended with further testing and instead it went the wrong way.

You still have a pretty serious problem even at the original 5132 hour life time. That's only 1365 more hours before the plane becomes scrap.

Mike C.

Username Protected · **Posted:** 24 Apr 2021, 00:06

Username Protected wrote:

Well so far nobody has an answer for why the hour limitation went down. I find that interesting.

That's the most interesting aspect of the issue. it suggests that fatigue testing or further analysis contradicted the original number. That first number was likely supposed to be a conservative number that would be extended with further testing and instead it went the wrong way.

You still have a pretty serious problem even at the original 5132 hour life time. That's only 1365 more hours before the plane becomes scrap.

Mike C.

Username Protected · **Posted:** 24 Apr 2021, 00:23

Username Protected wrote:

Let’s wait for the facts.

What facts do you expect to get? And when?

Wing life time initially set at 5132 hours.

Latest revision of TCDS reduces this to 3767 hours.

It is very rare for lifetimes to be reduced after entry into service.

At those lifetimes, amortized cost of the airframe is a substantial fraction of expenses.

Highest time M600 advertised is 2017 model with 1200 hours for $2M. The 2567 hours left thus cost $780 per hour.

The wing lifetimes apply to all operators, part 91 and otherwise. This is not a TBO, this is a life limited part. Wen the hours expire, it must be replaced or the airplane scrapped.

Mike C.

Piper Cheyenne II vs M600