New member

[Greg]

Let me introduce myself, My name is Greg Sandling and I work for Thermocouple USA, located in Irvine Ca. We manufacture the thermocouple probes that are a part for the Allison T56/501 Engine. I was wondering if anyone new of a pilot I could ask some questions of pertaining to real life situations they have while operating the aircraft, so we could better understand there needs in our manufacturing the T/Cs. Like what is crossover and how is it really on the coordinator position? It would be extremely valuable to be able to start a correspondence with someone. Thanks [email protected]

[Steve1300]

I welcome you to the group. I would suggest,though, that if you have a question concerning the usefulness of thermocouples, that pilots aren't the folks you need to speak to. You might want to speak with those who install them, inspect them,and replace them.

In this forum, as far as I know, your questions can be posted here. There are some career engine folks who answer posts here to have been dealing with thermocouples longer than other members here have been alive.

[INS/Dopplertroop]

My welcome to you too.

There is an old, old Lockheed Service letter in pdf, under Herkapedia, that talks to C-130 Thermocouples from toenail to backteeth. Might be quicker to find by putting thermocouple in the search box up top.

Although dated, you may find it interesting in a historical sort of way.

Jerry Rice

[pjvr99]

For the most part, thermocouples either work or they don't. I wouldn't know the difference

from one manufacturer to another. A specification is created by the designers/engineers, and

it's up to the manufacturer to manufacture to specification. Once in a while, a bad batch

slips through and we go through a phase of cracked casings, disintegrating ceramic, what-

ever. I can tell you about hunting for the 1 or 2 broken thermocouples out of 18, causing

problems during starting and take off, but that's what I get paid to do :-)

Glad to answer any other questions you may have. BTW, welcome to HerkyBirds

PJ

[Steve1300]

For those of you who sit left seat, but happen to be avid maintenance oriented types as well, sorry if I made it sound like you guys are too ignorant to talk about thermocouples. In every norm, there are exceptions.

If I wanted to discuss the faults/benfits of GCA/PAR or reliance on GPS approaches, I wouldn't look my for A&P for advice. But that's me.

There would also occasionally be an A&P who is into that kind of thing, but it is not where I'd go looking.

[Dan Wilson]

If you are looking for input as to "real life situations" like inflight, then you will need to be talking to the FE's (Flight Engineers) as they are "supposed" to know all about them and can relate what kind of inflight experience they have had and indications they saw with the malfunctions.

As to repair/replacement and ground troubleshooting you will want to talk to engine specialists.

Most pilots only know how to make "house big" and "house small" with the yoke (okay many of them know more than that).

Dan

[jetcal1]

For the most part, thermocouples either work or they don't. I wouldn't know the difference

from one manufacturer to another. A specification is created by the designers/engineers, and

it's up to the manufacturer to manufacture to specification. Once in a while, a bad batch

slips through and we go through a phase of cracked casings, disintegrating ceramic, what-

ever. I can tell you about hunting for the 1 or 2 broken thermocouples out of 18, causing

problems during starting and take off, but that's what I get paid to do :-)

Glad to answer any other questions you may have. BTW, welcome to HerkyBirds

PJ

Try getting a T/C tester 6685-01-569-7682 R/R P/N 23076502. Runs about 90 seconds per test. Still gotta' pull 'em though. :(

[pjvr99]

Try getting a T/C tester 6685-01-569-7682 R/R P/N 23076502. Runs about 90 seconds per test. Still gotta' pull 'em though.

I've got a better chance of ......... ah well, if I don't buy the ticket, I won't win the lottery. Tnx for the PNo

[jetcal1]

I've got a better chance of ......... ah well, if I don't buy the ticket, I won't win the lottery. Tnx for the PNo

My understanding is that most crews toss the T/C during the Isochronal. The tester has an ROI on the first Isochronal. Do two Inspections where you test the TC's instead of tossing them, and you now have a reduction in maintenance costs.

Even my manager understands saving money!

[SonnyJ]

Welcome Greg!

Jetcal1; as for testing the T/Cs and they check good in ISO is no guarantee there will be a reduction in MX costs. What is the likelyhood those T/Cs that checked good are going to survive until the next inspection interval? Having them pass during ISO and then fail sometime between inspections can easily eat up the "savings or ROI" garnered in ISO. With today's technology there should be a way to more accurately predict the life of thermocouples so a proper inspection interval (whether it be a condition or time change task) can be established. To me one of the things that is overlooked is what are the ramifications of changing, removing or extending inspection intervals. How much more unscheduled MX is being introduced from these actions? Like the T/C; they are a high cost consumable item and replacing them when they fail seems cost effective. However, you can find yourself spending more money in increased unscheduled MX and lost operational time versus replacing them during the scheduled MX interval. I am not saying this is the case with T/Cs but it can be if there isn't some follow through with recommendations like this.

Greg,

If you can either provide an accurate analysis to determine the failure rate, characteristics and distribution or build a thermocouple that has predictible wearout characteristics will be where to look to improve thermocouples. Unfortunately, thermocouples exhibit hiddien failure characteristics and usually are not evident until several have failed. Currently, pulling them for inspection is the the most likely choice to determine the condition of T/C's. As for arbitrarily replacing them the most advantageous and cost effective way or conditionally replacing them, I am not sure. Good luck with this.

IMHO,

Sonny

[jetcal1]

Zombie,

I agree too an extent. Obviously operating conditions play a large part of it. With the T56 in particular, I would be more concerned about sand then salt for example. Because of these variations along with those in manufacturing, a T/C will have a life limit.

However, determining where a midlife T/C is sitting in terms of insulation and resistance and establishing a conservative baseline should be sufficient in most applications.

I understand your caution in extending the life of the T/C onboard the engine, but stand by my statement; “establishing a conservative baseline should be sufficient.â€

A good test set will check for the hidden damage that a visual inspection cannot.

The test I mentioned is capable of performing the checks with the units installed. But, like you, I believe a visual inspection should be performed. The MkI eyeball will find things that electronic testing will not.

Unfortunately, due to differences in operating environments today’s technology cannot grant your desire to predict the life of the T/C, a good conservative testing regime can extend the life of many T/C’s while eliminating the degraded units before they have a chance to cause any secondary damage.

Also, I think I created a bad idea in my last post when I wrote:

“Do two Inspections where you test the T/C's instead of tossing them.â€

That should be read as: “testing the T/C’s on two engines.†While I believe the T/C will make it to the 2nd Isochronal…..I sure wouldn’t make any bets beyond that.