Twin Commander

General Category => Airframe => Twin Commander Turbine => Topic started by: donv on June 10, 2019, 11:01:19 pm

Title: Ouch!
Post by: donv on June 10, 2019, 11:01:19 pm
So, in anticipation of my paint job (see thread below), I decided to replace the horizontal stabilizer boots. They were pretty beat up, with patches and so on, and it would be ugly to have new paint and these patched up boots. I think they take a lot of rocks and debris on takeoff, since my wing boots are fine.

So, they pull off the old boots... and find a crack in the leading edge. And, to make matters worse, Twin Commander now specifies a new, thicker leading edge... with the result that they can't replace just one side, they have to replace both!

Oh well... the good news is that Twin Commander has them in stock. The bad news is 70 hours of labor per side.

I've had pretty good luck with this airplane, so I really shouldn't complain... so I'm not.

And, since someone will ask, no, apparently it can't simply be repaired, even though it's a very small crack.
Title: Re: Ouch!
Post by: Adam Frisch on June 10, 2019, 11:42:02 pm
Wow! Is it the same procedure on the main wings should they find a crack? Doing mine soon.... :-\
Title: Re: Ouch!
Post by: donv on June 11, 2019, 12:25:46 am
I don't know... ask Dan Black. Hopefully yours doesn't have any cracks! The wings take less of a beating along the leading edge, from what I can tell.

I also don't know if the leading edge is all one piece... I would guess it is not, which limits the risk a bit.
Title: Re: Ouch!
Post by: Steve binnette on June 11, 2019, 12:58:28 am
I had my tail boots replaced in 2015 when I did everything else.  Not sure how much they cost.  They still look great and I think you are doing the right thing?  New paint needs good boots and lenses for lights.

The tail boots always take a bigger beating than the wings for the all the reasons Don mentions plus the radius is smaller.

That just makes it worse.
Title: Re: Ouch!
Post by: SKYFLYER on June 11, 2019, 07:20:36 am
Maybe I have Just been lucky... But I have never heard of a leading edge wing crack unless some impact damage caused it.

Which begs the question...  how many Commanders are flying around with cracks???  Never to be discovered unless the boots are removed.

Clearly there must be some overlying reason for the cracks if Twin Commander already has a "thicker" fix.

MY boots were all replaced new during the purchase years ago and I have not needed to replace any of them.  So I am now wondering what I might have under mine.
Title: Re: Ouch!
Post by: donv on June 11, 2019, 11:52:23 am
There is no way to know how many have cracks. Mine is quite low time (4300 hours), but maybe that means mine has also had fewer boot replacements, etc.

My wife was asking about "how bad is it?" from a safety point of view. I told her that if there was any sort of safety issue, they would have issued an AD, or at least a service bulletin. I don't think there is even a service letter-- the thicker skin is simply a "product improvement."

This is just a tiny little stress crack between two rivets, but what can you do?
Title: Re: Ouch!
Post by: Adam Frisch on June 11, 2019, 09:00:18 pm
Not bad at all. Also nice to get rid of the lumpy hangar rash under, right?
Title: Re: Ouch!
Post by: donv on June 12, 2019, 11:12:00 am
Yes. I don't think that was actually hangar rash-- my guess is it was from a rock thrown up by the props.

If I was cheap, I might have been able to source a used part and saved some money, but I don't really think that is the right way to go, especially for this airplane, which has had a continuous history of owners who did things "the right way."

I found out that the thicker skin change actually happened at the end of 980 production-- probably in preparation for the 1000.
Title: Re: Ouch!
Post by: Steve binnette on June 12, 2019, 12:31:56 pm
Do you know if there Is a serial number cutoff where they changed the skin thickness?
Title: Re: Ouch!
Post by: donv on June 12, 2019, 12:34:12 pm
I was told 95085. Of course, the last 980 was 95084, so I'm guessing that means it starts with the first 1000...
Title: Re: Ouch!
Post by: Adam Frisch on June 12, 2019, 06:16:39 pm
Was that due to that tail that came off in a thunderstorm? I do seem to recall that was a lot later than when the 1000-model was released, sometimes in the 90's. But was there another reason for this change?
Title: Re: Ouch!
Post by: donv on June 12, 2019, 08:33:58 pm
I do not think so. I believe there were some tail-related ADs, and I think for the 695B and Australian certification they had to strengthen the tail, but I doubt this was a part of that program. Could be, though, I guess.

Since they mentioned a serial number, I'm assuming it was a change made while the airplanes were still in production. I don't think the 980 was officially discontinued for a few years, even though they didn't make any after the 1000 came out (they did make some later 840s, though).
Title: Re: Ouch!
Post by: Bruce Byerly on June 13, 2019, 12:06:13 am
Both sides? Thatís a new one Don.  :(  Iím going to have to look into that ...

Adam - no, the wing leading edges arenít comparable.  There has been a ďsqueeze testĒ forever in the horizontals. They can take a beating in the ice.
Title: Re: Ouch!
Post by: donv on June 13, 2019, 01:12:29 am
Bruce, if you find out something different I'd be interested to know. Aero Air's inspection department is pretty thorough, and I believe they verified this with Twin Commander (I asked them to), but who knows...
Title: Re: Ouch!
Post by: Bruce Byerly on June 13, 2019, 01:11:50 pm
Bruce, if you find out something different I'd be interested to know. Aero Air's inspection department is pretty thorough, and I believe they verified this with Twin Commander (I asked them to), but who knows...

Don, I have great respect for Aero Air. Always have. In response to my question, our DOM said heís comfortable changing one side only. If thereís something precluding that from being legal, and there may be, Iíd be interested. Maybe itís interpretation and/or they donít think itís a good idea to change the stiffness from side to side?
Title: Re: Ouch!
Post by: donv on June 13, 2019, 04:42:16 pm
The word came straight from Twin Commander's structural engineer. Is it legal to only do one side? I don't know that, but it was Twin Commander's official recommendation to do both.
Title: Re: Ouch!
Post by: Bruce Byerly on June 13, 2019, 05:19:47 pm
The word came straight from Twin Commander's structural engineer. Is it legal to only do one side? I don't know that, but it was Twin Commander's official recommendation to do both.

May be that since you have to have the same boots on each side, and they had to replace the dissimilar boot, that they figure they are halfway there.  Probably comes down to ďrecommendationĒ vs. ďrequirement.Ē
Title: Re: Ouch!
Post by: donv on June 13, 2019, 06:06:17 pm
The boots on both sides were already going to be replaced. They were both pretty beat up.

That said, it may come down to that, although they didn't phrase it that way. They did say they've had to do it several times previously on 690s, including one they owned... so I'd guess they've double-checked.
Title: Re: Ouch!
Post by: donv on June 13, 2019, 06:30:19 pm
They forwarded me the email. It says "you will have to replace the other side as well since it would still be a -147 skin and these must be kept the same gage to keep the stiffness of the horizontal balanced.  Twin does not make the -147 longer since it was deleted and replaced with the -249."
Title: Re: Ouch!
Post by: Bruce Byerly on June 13, 2019, 07:07:48 pm
Got it. They ought to have tech support Dept on the same page . . .

Probably too busy trying to undo the mess the forestry service has done with their alert on the tail. Seems that some operators have forgotten to do some basic maintenance.
Title: Re: Ouch!
Post by: donv on June 13, 2019, 07:18:36 pm
What is the deal with the forestry service and the tail?

Also, FYI, they sent me the serial number effectiveness on the thicker tail leading edge skin. It looks like 96069 and subsequent on the 1000s and 15039 on the 900s had the thicker skin from the factory.
Title: Re: Ouch!
Post by: Bruce Byerly on June 13, 2019, 10:55:25 pm
Fuselage station 386 I believe. Vertical attach point. There were clearly visible long cracks found on the bulkhead and attach frame of a particular 690 that showed evidence of working over time. Seems like it should have been caught earlier but, in any case, demonstrates why the area is inspected and is important. The latest model planes had design changes in the area.  Approximately 26 planes have been repaired over the years.  Iím sure you will be hearing more about this as awareness and safety are everyoneís priority.
Title: Re: Ouch!
Post by: Adam Frisch on June 14, 2019, 06:50:49 pm
Does it only apply to 690's, Bruce?
Title: Re: Ouch!
Post by: Bruce Byerly on June 14, 2019, 11:18:27 pm
Does it only apply to 690's, Bruce?

Adam, from my perspective, thereís nothing in particular to apply other than good practices. The focus is on 690ís as they are most common and are flying the majority of the forestry work, tens of thousands of hours per year. Low level in the summer.  Itís hard work.

But, I know itís always been prudent to look closely at the tail of any Commander and should be part of regular inspections.  I ferrried one that had half of the rivets holding the lower vertical spar together sheared. Turned out that it had been damaged in a tornado at some point as I recall. 

Itís a little like that leak that you dealt with. The plane was talking to you and it just took someone to actually look at it to see the issue. Iím fairly certain that thereís nothing new about any of it.  They are proven and capable (just look at the one that flew with half the tail knocked off!) but need to be kept up with just like any plane.
Title: Re: Ouch!
Post by: donv on June 15, 2019, 01:36:25 am
Well, mine only gets better. When they opened up the stab, one side was fine but the other side had two ribs with mis-drilled holes (from the factory) and one rib with a crack in it. All repairable, and in fact at least one of the ribs is in stock at Twin Commander, but still...
Title: Re: Ouch!
Post by: Bruce Byerly on June 15, 2019, 01:53:16 am
Well, mine only gets better. When they opened up the stab, one side was fine but the other side had two ribs with mis-drilled holes (from the factory) and one rib with a crack in it. All repairable, and in fact at least one of the ribs is in stock at Twin Commander, but still...

Are they mis-drilled if they made it this long?  Seems like they might get grandfathered in . . .  :P

Itís never fun to spend money on things that donít make it shinier, faster, or easier to fly but hopefully itíll be good for the next 30 years.
Title: Re: Ouch!
Post by: donv on June 15, 2019, 11:25:41 am
That's what I thought too! I also said, well, didn't some inspector at the factory sign off on this, hence it's good?

But the answer was, maybe, but as far as they're concerned, it's not good.

All in all, I'd prefer that they repair it, but it irks me that the factory did that.
Title: Re: Ouch!
Post by: Steve binnette on June 15, 2019, 11:54:25 am
That is so weird Don.   Do you have any photos?
Title: Re: Ouch!
Post by: donv on June 15, 2019, 12:00:29 pm
Sure...

Title: Re: Ouch!
Post by: SKYFLYER on June 15, 2019, 03:58:11 pm
Sort of makes one wonder how long it has been flying around like that...
Title: Re: Ouch!
Post by: donv on June 15, 2019, 05:05:20 pm
39 years!

Sort of makes one wonder how long it has been flying around like that...
Title: Re: Ouch!
Post by: donv on June 19, 2019, 08:58:18 pm
And the saga goes on... one of the leading edges was damaged in shipping. Twin is now sold out, of course, but Aero Air has someone who can make one... just adds another week or two on. Now I'm starting to miss some trips, which is annoying.
Title: Re: Ouch!
Post by: donv on June 23, 2019, 10:05:58 pm
Adam, I hope your airplane's luck isn't contagious! Mine is right there by her, although with about 4 other Turbo Commanders. Still hoping to be back in the air by next week, even as I have had to cancel several trips...
Title: Re: Ouch!
Post by: Adam Frisch on June 24, 2019, 10:19:53 am
Don't get too close!  ;)
Title: Re: Ouch!
Post by: donv on July 02, 2019, 12:49:04 pm
End of next week... maybe. If Adam's airplane doesn't send any more bad luck my way!
Title: Re: Ouch!
Post by: Adam Frisch on July 03, 2019, 07:18:20 pm
I don't think money problems are contagious!  ;)

Title: Re: Ouch!
Post by: donv on July 17, 2019, 12:16:46 pm
Finally back in the air!
Title: Re: Ouch!
Post by: donv on July 23, 2019, 11:58:43 am
Back in the air, but now no autopilot! And they think it's some part that is unobtanium...
Title: Re: Ouch!
Post by: Bruce Byerly on July 23, 2019, 10:07:09 pm
Back in the air, but now no autopilot! And they think it's some part that is unobtanium...

Now thatís an ouch!  What part is it?  I was just marveling at the smoothness of an AP106 today thinking about the good service they keep giving.
Title: Re: Ouch!
Post by: donv on July 23, 2019, 11:34:36 pm
It's an "aileron rate sensor" and apparently it was a change they made with the Jetprops.

That 980 you're parting out doesn't happen to have Collins avionics, does it?

They think they've found one in "as removed" condition, so we'll see.

Of course, I'm always skeptical that this little box, after almost 40 years, happens to fail while the airplane is in maintenance... They did do the 900 hour autopilot check, so maybe it was disturbed or something.
Title: Re: Ouch!
Post by: Steve binnette on July 24, 2019, 02:03:39 pm
Sorry to hear that Don.

Going into MX is like going into a hospital.  Things just pop up!!
Title: Re: Ouch!
Post by: donv on July 24, 2019, 02:06:06 pm
I just wish that for once, it would actually work better coming out than it does going in!
Title: Re: Ouch!
Post by: donv on July 25, 2019, 12:37:01 pm
They found one and claim it works, so we'll see later today...
Title: Re: Ouch!
Post by: donv on July 31, 2019, 08:48:25 pm
Finally back and going!
Title: Re: Ouch!
Post by: Adam Frisch on August 02, 2019, 09:25:54 pm
You got my 680V cooties by being parked next to it! ;)
Title: Re: Ouch!
Post by: Steve binnette on August 03, 2019, 01:15:17 pm
Excellent, glad to hear you are back in the air.