The Unexpected Drop of MP at 12K Ft

[Sherman]

Re: The Unexpected Drop of MP at 12K Ft

Alex-Glad you were 'calculating' and it worked out fine. We have talked these cables 'to entity' and as we all have shared-the cables, the flexible ends, the rod ends, the adjustments are 'pretty critical' for dependable and safe control - - as well as our own 'Mental Security'. I just changed mine last fall as the flex joint was a bit loose -even though Beechhurst cable was 2 yrs. Once off was not really a problem, so have 2 spares now.
also on our T0-360s- watch the carb mixture SEAL behind the carb lever. Seasonal Temp changes can cause air leaks after a few years. And examine that mixture bracket while you replace the waste gate cable. Bracket can Crack at the 90 deg turbo mounts. Wrote it up ladt fall/Annual. Doesn't always show in cutoff position. As critical as wastegatemps cable. Please do post pic of where cable broke.

 

[atjudge]

Re: The Unexpected Drop of MP at 12K Ft

The Longer I own my TC, the more I realize that with any issue with the throttle cable, trouble shooting should begin at the Turbo end and work backward. Will say alot of time.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

Great job flying the airplane Alex!! Glad you and wife are ok..

Thank you Terry! I really do appreciate it.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

Nice job I'm glad it all worked out well.

Thank you Rod.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

Alex-Glad you were 'calculating' and it worked out fine. We have talked these cables 'to entity' and as we all have shared-the cables, the flexible ends, the rod ends, the adjustments are 'pretty critical' for dependable and safe control - - as well as our own 'Mental Security'. I just changed mine last fall as the flex joint was a bit loose -even though Beechhurst cable was 2 yrs. Once off was not really a problem, so have 2 spares now.
also on our T0-360s- watch the carb mixture SEAL behind the carb lever. Seasonal Temp changes can cause air leaks after a few years. And examine that mixture bracket while you replace the waste gate cable. Bracket can Crack at the 90 deg turbo mounts. Wrote it up ladt fall/Annual. Doesn't always show in cutoff position. As critical as wastegatemps cable. Please do post pic of where cable broke.

What were the symptoms of the carb mixture SEAL issue? Just curious. Always good to hear insights from owners that have the experience.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

I got some photos of the wastegate cable from the mechanic at Flightline in Tallahassee. Unfortunately its policy for them not to allow owners in their shop while they are working. Otherwise I would have more pictures. They were also the only shop on the field.

You can see the photos via this link.

https://www.dropbox.com/sh/5104l9d2jm3sgs6/AADmCQeRePI2Kodne3caUvQIa?dl=0

 

[Commander91gm]

Re: The Unexpected Drop of MP at 12K Ft

I got some photos of the wastegate cable from the mechanic at Flightline in Tallahassee. Unfortunately its policy for them not to allow owners in their shop while they are working. Otherwise I would have more pictures. They were also the only shop on the field.

You can see the photos via this link.

https://www.dropbox.com/sh/5104l9d2jm3sgs6/AADmCQeRePI2Kodne3caUvQIa?dl=0

I realize you were in a bind and stuck on a field but I would never do business with an FBO that wouldn't allow me to access the plane while they're working on it that's absurd. I'm not quite sure what I'm looking at -in the last photo there are two different cables and the one on the left is nothing like what the turbo cable should look like. I'm wondering if that was what you had in the plane? The one on the right looks like the proper cable.

 

[alim]

Re: The Unexpected Drop of MP at 12K Ft

I realize you were in a bind and stuck on a field but I would never do business with an FBO that wouldn't allow me to access the plane while they're working on it that's absurd. I'm not quite sure what I'm looking at -in the last photo there are two different cables and the one on the left is nothing like what the turbo cable should look like. I'm wondering if that was what you had in the plane? The one on the right looks like the proper cable.

so root cause :

- Wrong cable used (wrong cable length).
- Action worked the cable over time - putting stress on it
- The cable snaps after 118 hours. Is that the fracture point we see in pic #1 ? Logs should show cable part # for wrong cable. i.e. do we know how the wrong cable got introduced at all ?
- Cable snaps, turbo doesn't close - power falls off , giving you about ~20 MP, allowing you to do a controlled descent to landing.

Sequence of events correct ?

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

I realize you were in a bind and stuck on a field but I would never do business with an FBO that wouldn't allow me to access the plane while they're working on it that's absurd. I'm not quite sure what I'm looking at -in the last photo there are two different cables and the one on the left is nothing like what the turbo cable should look like. I'm wondering if that was what you had in the plane? The one on the right looks like the proper cable.

The cable on the left is the new Lycoming cable, part number LW-14714. Reconfirmed with two different Lycoming tech reps on the phone to be safe.

Just to recap, the old cable was built by Beechhurst based on duplicating the one the previous owner had on the aircraft which was longer and incorrect. Beechhurst thought the TCA was different than the TC and proceeded to duplicate.

Please share your thoughts.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

I realize you were in a bind and stuck on a field but I would never do business with an FBO that wouldn't allow me to access the plane while they're working on it that's absurd. I'm not quite sure what I'm looking at -in the last photo there are two different cables and the one on the left is nothing like what the turbo cable should look like. I'm wondering if that was what you had in the plane? The one on the right looks like the proper cable.

so root cause :

- Wrong cable used (wrong cable length).
- Action worked the cable over time - putting stress on it
- The cable snaps after 118 hours. Is that the fracture point we see in pic #1 ? Logs should show cable part # for wrong cable. i.e. do we know how the wrong cable got introduced at all ?
- Cable snaps, turbo doesn't close - power falls off , giving you about ~20 MP, allowing you to do a controlled descent to landing.

Sequence of events correct ?

Pic #1 shows where it snapped.
Wrong cable reproduced by duplication of previously installed cable used by the previous owner. Beechhurst thought TCA was different than TC and proceeded.

Just replaced with $1,200 Lycoming LW-14714 cable.

Rest is close enough.

 

[Commander91gm]

Re: The Unexpected Drop of MP at 12K Ft

There should be very little stress on a properly built and installed cable. I am confused because I see no way to stress that cable enough to fracture a 1/4 inch or so shaft. Had to be something wrong with that shaft on the end of the cable.

 

[alim]

Re: The Unexpected Drop of MP at 12K Ft

There should be very little stress on a properly built and installed cable. I am confused because I see no way to stress that cable enough to fracture a 1/4 inch or so shaft. Had to be something wrong with that shaft on the end of the cable.

If the cable is 8 inches longer than spec and as you push the throttle, cable pushes the waste gate valve but allows it to bend as well instead of pure translational motion (correct length cable) to the wastegate Butterly valve - I could see a longer cable develop a sweet spot for bending (repeated stress) and eventually snap. Just a theory ..

of course we could install an 8 inch longer cable , move the action by hand and see what happens. How do we confirm the rod end is dry. Cant really tell in that pic.
i.e. if the rod end starts binding and then that binding forces the cable to bend than it otherwise would.

From the event description - it happened in cruise. i.e. steady-state - not when force was applied (initially or other changes). So the cable must be in a stressed position already (bend?) and then it finally gives. Just theorizing ...

Alex - did you notice any stiffness in throttle movement in flights prior to ? (E.G on go-arounds, etc ?)

 

[Commander91gm]

Re: The Unexpected Drop of MP at 12K Ft

It does look like it broke where the flexible cable transitions to the solid end. On a proper length cable that end is inside and supported by a sheath.

 

[alim]

Re: The Unexpected Drop of MP at 12K Ft

Btw - Alex

you aren't unique in this predicament. The original lycoming part is expensive.
With the correct beechurst replacement - its acceptable but as it isnt Teflon lined - 2-3 yrs before you go "gasoline cleaning".
But owners in the past have certainly improvised. You ended up inheriting someone else's bad decision making (a cable is a cable).

When I bought my TC in 2000 - the power cable was binding. When I brought it into shop and we examined what was in there - it was an unapproved cable and not beechurst - no idea where it came from. I have 2 dead stick landings to show for it (had to cut mixture on final) as power wouldn't come down below 20 MP.

I replaced it with the expen$ive lycoming cable and over the years haven learnt proper care and feeding. So replacements are infrequent and makes the expensive cable kinda worth it. I keep the beechurst cable as backup (as you have now) since it does take a while to source the right lycoming part (how long did it take you? ) I bought mine last yr with a 6 week lead time and only just installed it this annual in July along with a new heim joint (do them both I say).

But back to proper care and not feeding - this should last you a decade.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

Btw - Alex

you aren't unique in this predicament. The original lycoming part is expensive.
With the correct beechurst replacement - its acceptable but as it isnt Teflon lined - 2-3 yrs before you go "gasoline cleaning".
But owners in the past have certainly improvised. You ended up inheriting someone else's bad decision making (a cable is a cable).

When I bought my TC in 2000 - the power cable was binding. When I brought it into shop and we examined what was in there - it was an unapproved cable and not beechurst - no idea where it came from. I have 2 dead stick landings to show for it (had to cut mixture on final) as power wouldn't come down below 20 MP.

I replaced it with the expen$ive lycoming cable and over the years haven learnt proper care and feeding. So replacements are infrequent and makes the expensive cable kinda worth it. I keep the beechurst cable as backup (as you have now) since it does take a while to source the right lycoming part (how long did it take you? ) I bought mine last yr with a 6 week lead time and only just installed it this annual in July along with a new heim joint (do them both I say).

But back to proper care and not feeding - this should last you a decade.

No stiffness at all. I had just climbed from 8K to 12K feet about 8 mins earlier. All I noticed was the MP moving around about an inch which is unusual. Then it just happened.

It did not take me long to get the cable. Airpower got for me. Apparently this cable is used on other airplanes also.

I sure hope that your prediction materializes and not only does it last a long time but also just gets stiff instead of breaking when in needed of replacement.

The last thing on my mind was that a cable like this would snap. My throttle and mixture cables came from McFarlane. All the fancy avionics and autopilot wont matter much if the throttle cable snaps. Still, I feel confident because I know this is very unusual. I am looking forward to picking up the plane in the next couple of days. Hopefully making it to Georgia at the end of the month.

Glad to know you made it safe on a dead stick. Not many do.

 

[alim]

Re: The Unexpected Drop of MP at 12K Ft

Btw - go through the logbooks.
I have transcribed mine into a .xls for easy historical searches.

See a pattern before 2000 ? I bought the plane in august 2000


Before that - the previous 2 owners had been fighting this issue for how long ?
Notice - new cable from factory new airplane 1976 lasted till 1991. - no issues.
In 1991 - the new owner had it lubed regularly ..and see the issues pop up ?

in 2000 :
The last 3 entries are mine - where I installed the correct cables to waste gate , followed by the correct cable inside the cabin.
No issues till 2017 - I guess it was time - but I'll take a 17 year interval anyday

I searched for all entries relating to waste gate cable or throttle cable issues.

LOGBOOK:

07/02/1976. Airplane is born . First flight log
10/10/1977 Throt Cable Lubed
05/11/1978 100 Hr: Lubed Throttle Cable 395.2. <B>-no issues 1976 till 1991. No logs of cable lube found in annual inspections 1978-1991 </B>
<mark>03/15/1991. ANNUAL INSPECTION ; Turbo Wastegate lubed ;
05/24/1992 ANNUAL INSPECTION ; Turbo Wastegate cable lubed
06/24/1992 Installed Turbo WasteGate Cable
03/23/1995 Replace Throttle Cable
08/21/1995 Annual Inspection ; Rod End on Wastegate Replaced ; </mark>
08/26/2000 N976MA - used to be 4534W acquired by me.
11/22/2000 Replaced LW 14714 Cable; LW15765 Rod End <B>-replaced properly now in 2000 by me (I just bought it here - lots of binding at power)</B>
10/02/2001 Replace Throttle CABIN CONTROL CABLE 46135-21 - <B>some binding here but happened cold as well - so not a heat/wastegate cable issue </B>
07/30/2018 Replaced LW 14714 Cable; LW15765 Rod End - - <B> No issues for 17 yrs. in 2017 - symptoms : Stiffness after 1 hr flight. Noticeable on adding power on go arounds</B>
Current : now +10 hrs after annual and cable replacements. No issues.

Go through your logbooks to see what they did to it ...

Hence I stand by the ... it should last a decade if you don't feed it.

 

[alexnor]

Re: The Unexpected Drop of MP at 12K Ft

Btw - go through the logbooks.
I have transcribed mine into a .xls for easy historical searches.

See a pattern before 2000 ? I bought the plane in august 2000


Before that - the previous 2 owners had been fighting this issue for how long ?
Notice - new cable from factory new airplane 1976 lasted till 1991. - no issues.
In 1991 - the new owner had it lubed regularly ..and see the issues pop up ?

in 2000 :
The last 3 entries are mine - where I installed the correct cables to waste gate , followed by the correct cable inside the cabin.
No issues till 2017 - I guess it was time - but I'll take a 17 year interval anyday

I searched for all entries relating to waste gate cable or throttle cable issues.

LOGBOOK:

07/02/1976. Airplane is born . First flight log
10/10/1977 Throt Cable Lubed
05/11/1978 100 Hr: Lubed Throttle Cable 395.2. <B>-no issues 1976 till 1991. No logs of cable lube found in annual inspections 1978-1991 </B>
<mark>03/15/1991. ANNUAL INSPECTION ; Turbo Wastegate lubed ;
05/24/1992 ANNUAL INSPECTION ; Turbo Wastegate cable lubed
06/24/1992 Installed Turbo WasteGate Cable
03/23/1995 Replace Throttle Cable
08/21/1995 Annual Inspection ; Rod End on Wastegate Replaced ; </mark>
08/26/2000 N976MA - used to be 4534W acquired by me.
11/22/2000 Replaced LW 14714 Cable; LW15765 Rod End <B>-replaced properly now in 2000 by me (I just bought it here - lots of binding at power)</B>
10/02/2001 Replace Throttle CABIN CONTROL CABLE 46135-21 - <B>some binding here but happened cold as well - so not a heat/wastegate cable issue </B>
07/30/2018 Replaced LW 14714 Cable; LW15765 Rod End - - <B> No issues for 17 yrs. in 2017 - symptoms : Stiffness after 1 hr flight. Noticeable on adding power on go arounds</B>
Current : now +10 hrs after annual and cable replacements. No issues.

Go through your logbooks to see what they did to it ...

Hence I stand by the ... it should last a decade if you don't feed it.

This is very interesting.

I did not change the rod ends this time. Can certainly do soon.

I was wondering of if any of you are putting the cable through "Fire Sleeve" before installing it.

 

[kgrant]

Re: The Unexpected Drop of MP at 12K Ft

Hey I just got in here. Pic #1 shows both the throttle & wastegate rod ends on same side of the throttle rocker arm. That puts A LOT of stress on that transition from the solid to flexible cable point.

The wastegate rod end should be installed on the opposite side of the rocker.

If you look up from the bottom at those cables at the carb, you can see the abrupt transition at the bracket. Also notice they used solid nuts instead of castle nuts that would give the joints more freedom.

I think the overall difference in length is irrelevant. It only matters if the mounting adjustments are incorrect. The TRAVEL distrance is what matters. k

 

[kgrant]

Re: The Unexpected Drop of MP at 12K Ft

found a picture (I think this is actually Joel's) of the correct cable to rocker installl...k

 

[alim]

Re: The Unexpected Drop of MP at 12K Ft

Yeah that’s his carb leak pic . I used it last year to fix the rocker arm routing last year when i initially ran into stiffness issues.