Ageing Gas Turbs the latest

It is a concern to some Rob, remember the early gas turbines late / post war etc were built without any lives on them at all and were never expected to last but a few years, so you could legally be flying a 1945 meteor with its original engine in it in theory, something the manufacturers would never have envisaged.
You go back to 1945 and you would have been laughed out of the building if you had said I intend to buy one of these in 60 years time and fly it as a leisure pursuit.

As for 20 years, you do realise that although a private piston spam can has a life placed on the engine of 12 years and XYZ hours, ( plus an allowable 20% extension by the CAA) If that aircraft is privately owned then the engine can continue in service ” on Condition” after the life period laid down by the manufacturer has expired. It is one thing I always thought was wrong.

I believe when the RAF accepted the Meteor into service they quoted that both engines required less maintenance per flying hour than the Merlin in Spitfires.

Problem with the elastomers in those old control systems is that they’re everywhere. Every last unit is full of them, there’s no real way to assess their condition from the outside and a failure of any one of them could have serious consequences. There’s been several strip inspections of legacy fuel control units over the years that have revealed deteriorating elastomers and one failure where a diaphragm was partly submerged in old fuel for many years leaving the dry half air damaged. Much as I hate to see old machines consigned to never run again it really is about time these things are pulled down and properly overhauled if they’re to keep on running.

Yes but that wold be the case with a brand new engine.

You know where the faults are going to be and you go looking for them. That to me is safer than simply relying on the life of an item.

I understand that, hence trend logs of old etc, but what I am saying is the manufacturer has deemed their product has a safe life of XYZ, the CAA say with experience that can continue on, ( and it’s only the CAA that do this ) but you are on a downward curve in both terms reliability or safety in that respect. I look after and have looked after loads past TBO, but the inherent risk is there, it is just a strange situation in that a School aircraft as an example must adhere to the life limits as it is safer, where a private one can ignore them, especially as failure in both cases can often have the same result… the man on the ground will not know that the two aircraft flying over his house are operating to two different standards.

Back to gas turbines, the manufacturer of modern engines based on experience from past products using materials can judge their safe operating lives..
Engines are built these days for long term reliability and longevity on the wing, neither was really the case during the early days, and the fact that no lives were ever established on a calender basis must be a cause for concern, hence these publications focusing on deterioration of consumables. The same can be said equally for a piston engine, as they too use similar consumables..

FB, what I was trying to get across is there are two standards in play and either can still kill the innocent bod on the ground, it should really be a single standard, and in my eyes the tighter one of the two. You got to a point where a fault you could see was the cause to reject it, it is the ones you cannot that kill.

Yes but that wold be the case with a brand new engine.

You know where the faults are going to be and you go looking for them. That to me is safer than simply relying on the life of an item.

FB, what I was trying to get across is there are two standards in play and either can still kill the innocent bod on the ground, it should really be a single standard, and in my eyes the tighter one of the two. You got to a point where a fault you could see was the cause to reject it, it is the ones you cannot that kill.

Some very broad generalisations there. GR24 to which you refer has strict limitations on which engines that can exercise the privilege. For example it only applies below a certain horsepower, it also relies on submitting a more restrictive maintenance inspection routine to the overseeing authority – be it CAA, LAA, or BGA for acceptance. So yes, you are running well over o/h periods, but with a much stricter maintenance schedule to ensure “condition monitoring”. From personal experience, we got 4000 hours out of a Lycoming (twice o/h) and we only pulled it because the magneto drive gear was worn which meant we had to keep retiming the mags.

As for insulators in the mags, the aging material was highlighted in the report and as such the recommended o/h life was slashed from 500 hours to 250 hours by the CAA. If you then follow the servicing instructions and test the mag properly, if it passes, then no problem, if it fails then it’s rejected. Several companies are working on material substitutions as such so when the supply of good insulators has completely dwindled there will be alternatives.

As long as service schedules are adhered to and adjusted when problems arise, there is no real problem with extend life operations

FB

This reminds me a bit of the safety recommendation that came out of PL983’s crash in France in 2001. The AAIB found that an insulator in the magnetos was not functioning as it should and these items could be over 50 years old. As mentioned, we are running these engines far beyond their originally intended service life and this can lead to strange and previously unrecognised problems.

It is a concern to some Rob, remember the early gas turbines late / post war etc were built without any lives on them at all and were never expected to last but a few years, so you could legally be flying a 1945 meteor with its original engine in it in theory, something the manufacturers would never have envisaged.
You go back to 1945 and you would have been laughed out of the building if you had said I intend to buy one of these in 60 years time and fly it as a leisure pursuit.

As for 20 years, you do realise that although a private piston spam can has a life placed on the engine of 12 years and XYZ hours, ( plus an allowable 20% extension by the CAA) If that aircraft is privately owned then the engine can continue in service ” on Condition” after the life period laid down by the manufacturer has expired. It is one thing I always thought was wrong.

Am I the only one shocked by this being applicable to ‘For any applicable turbine engine with calendar time greater than 20 years since last overhaul’ . How many engines flying have not had a overhaul for 20 years? That seem to be a awfully long time for a engine to go without a overhaul?