Engine designs that have problems 22

[enginesrus]

Since the one thread I started, is headed way off topic, reason for this.
Engine designs that have problems or have had them.
I'll start with the 3 valve Triton.
This guy explains. Has data from others that deal with the same problems.

https://www.youtube.com/watch?v=xcN_WcGr4BU

 

[Alistair_Heaton]

You think car engines are bad...

You should see the aero engine issues.

We have been waiting 3 years now for P&W to redesign the engine bleed duct system to get rid of the acoustic harmonic which was causing disck failures.

 

[enginesrus]

Alistair Heaton, I'm not just pointing out car engines failures. All IC engines here, not a huge turbine person though, but I would like to hear more about the P&W, tell us more about it.
I remember not too long ago one of the recip aircraft engine manufactures had a huge problem with failed lifters, from out of house manufacturing outfits. I have searched for that article and is now nowhere to be found. Personally I have never been impressed with those small aircraft engines, especially the construction methods.

 

[Alistair_Heaton]

There is an issue with the low pressure compressor and its failure.

It's to do with the swap over between the high pressure bleed and low pressure. There are operational procedure changes to protect against it.

I am positioning today and just on the phone. When I get near a computer I will do the subject more justic from a pilots point of view. There will be others in the forum who can do the engineering of the problem more justice.

 

[Alistair_Heaton]

Right in about 2019 there was 3 inflight engine failures on the A220

The lp compressor rotor was found to be the common failure point due cracking.

The FAA required frequent boroscope inspections after an initial grounding inspection.

It started just after a FADEC software update in 2019.

Crews had to manually limit the max N1 during climb from memory to 93% by taking the Auto throttle out. You could reengage it during the cruise but most of us didn't because if you hit some sink the AT would then power up to over 93% and then the engines would require an inspection which took 36 hours because it had to be left to cool otherwise you would melt the borescope and then the inspection done and paper work. So we just left it out and set a N1% and left it there.

There is something going on with the bleed duct system. If you have ever heard one after start it makes a howling noise after the APU is turned off and the engines take over the bleed power. While there is no load it uses the lp port off the LP compressor and when load comes on at low power settings it needs the HP port. As it swaps valves there is a resonance generated. It does this in flight as well when you power up configuring to land. It is extremely distinctive. IN fact some pilots use it to let the family know they will be home in the next 40 mins. They power up and down a couple of times, while flying near their houses.

Medium term solution was to up date the FADEC software with the new limitations which reduces the climb thrust and now we can keep the AT in.

Long term is they are going to mod the bleed system and then update the FADEC again after that.

There is something else going on with the rear turbine seals at the moment and deltaP over them at high altitude and low thrust settings leading to the premature failure and high oil consumption. We deal with that by starting a slow decent early so it keeps some power on until we get to lower levels and higher static pressure.

Its a good engine from a pilots POV but its definitely different to a none geared fan. You almost have to manage it like a turboprop engine. I suspect some of the issues are related to long time Jet pilots doing stuff that was deemed good practise on a old school jet engines and its not the way the engine was designed to be operated.

 

[JohnRBaker]

I know this doesn't belong here, but I know Alister follows this thread and I figured he'd be interested. Considering that this guy had less then 100 flying hours, it looks like he did a really good job, even managing to almost park the plane at a pull-off. Too bad the plane didn't have a horn as that might of helped with the people I'm sure he surprised when he passed over and then landed in front of them:

Terrifying Video Shows Plane's Emergency Landing On Highway As Cars Whiz Past

A novice pilot was forced to use a North Carolina highway as a runway after his plane's engine shut down.

https://www.huffpost.com/entry/plan...olina-vince-fraser_n_62cb5aebe4b02e0ac915a89b

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Alistair_Heaton]

I did my PPL in Ormond beach in 2000.

Highways were the defacto option with engine failures. You just have so many of them in certain areas. And they are long wide and straight unlike other countries.

The traffic is going at the right speed to boot for most light aircraft landing.

There is double figures worth of highway landings after engine failures in the USA per year. It just this one was caught on video.

The lycoming o engine aero engine series is relevant to this thread. It was designed in 1955 and no real changes to it since and its still in production getting fitted to new aircraft. Twin magnetos for the sparkplugs. Survives abrupt cooling and students abusing it in the circuit. Not very efficient though.

They have to be overhauled every 1500/12 years hours operating though. Think the official time is less than 1500 but you can get an extension after certain checks.

I might add I never had an off runway engine failure in my 1100 hours of piston flying. Cancelled many flights with dodgy mags. Turbine engines are so much more reliable.

 

[enginesrus]

Turbines can have their share of problems. And those problems especially in the aircraft world, are many thousands of dollars more than comparing to the older piston engines of the past. How many millions does an average jet engine cost to overhaul? Big radial engines now are still under the 1/4 million range if even that much for an overhaul, and yes they still are on the job in many different areas of the world.

 

[TugboatEng]

CF6 engine does 40,000 hours on wing.

https://www.geaviation.com/press-re...rican-airlines-sets-cf6-80c2-time-wing-record

The first scheduled inspection overhaul is at 18,000 hours.

Meanwhile, check out this table for the R-4360 in a fleet of C97 aircraft. It shows in 1965 that only 12% of engines didn't have failures within their overhaul period.

You're doing well if you get to 1500 hours between overhaul.

http://www.enginehistory.org/Piston/P&W/R-4360/r-4360_service.shtml

So turbine engines require far fewer overhauls. Also, a turbine engine can do the work of 3+ of the largest recip engines which improves economy even more.

 

[SwinnyGG]

I'm a licensed pilot, typed on a couple of different hells, 2 piston, 2 turbine; (although not a professional one.. I probably have .1% of Alistair's accumulated hours) and based on that experience.. implying that piston aircraft engines are more reliable than turbines is yet another hilarious incorrect opinion to add to the growing list.

Airlines aren't in it for charity. If piston engines were more cost efficient, that's what they'd be using.

 

[Alistair_Heaton]

Never flown a supercharged petrol aviation engine.
Remember the theory stuff we had to learn about them..

The Lycoming o-235 was what I spent most of my uneventful time on. And we regularly used use extensions on them. They were needing a 50hour service every 7-10 days at the school I was instructing at even in winter in the north of Scotland Inverness.

Got loads of time on the Garrett tp331. Its pretty bullet proof.

Never flown the cf6 but you never hear anything about it.

Turbines are just so much less work to start and manage. The Fedec engines are much less than the old ones which were massively easier than piston.


And I don't place much value on flight hours. These days I pick up 8 hours in one day with 2 flights. Rotary pilots 8 hours is 16 plus approaches and landings and lord only knows about thermal cycles which is in my opinion is what kills aero engines along with miss handling. Which is another thing which helps with modern engines the pilot doesn't actually control it. They submit Thier wishes to the fadec. And it will sort it out for you. Old engines you could over temp them, shock cool them, over boost in a movement of one lever.

 

[enginesrus]

Tugboat, yeah all we have to compare to the modern day aircraft power plants turbine vs recip is the latest and greatest turbines to 1940's and 50's piston engines. Back in the days not long after chart was made, all engineering stopped on large aircraft piston engines. With the talk of electric motors in aircraft now, that would mean re introducing the propeller on airliners. Redesigning a high performance recip engine for large aircraft now could produce an engine that has 2x the efficiency of a turbine using way less of the same jet fuel, and producing more power than a battery laden aircraft would. I think they hate the idea of regressing back to pistons.

 

[SwinnyGG]

Redesigning a high performance recip engine for large aircraft now could produce an engine that has 2x the efficiency of a turbine using way less of the same jet fuel

You do realize that if this was true (it isn't.. but I digress) and you did it yourself you could make hundreds of millions of dollars on this product

What's stopping you?

 

[TugboatEng]

Propfan is a thing.

https://en.m.wikipedia.org/wiki/Propfan

 

[Alistair_Heaton]

As an aside they are going down this route with the latest generation of geared fan jet engines which the PW1500G is one of them the NEO and MAx have them as well.

The fuel savings are utterly collosal. Which was the main driver behind the MAX being developed in such a screwed up way.

As an example of real life fuel burns.

In cruise with a full load landing at max landing weight cruising at mach 0.78 we will burn 1800kg/hr. if we go economic mode around europe we can get 1600kg an hour with a full load in the back MAch .72 which is very near what we used to burn on the Q400 with 70 pax in the back at 1000kg/hr but with double the number of pax and much faster. The ATR might be an ugly uncomfortable, slow pain in the bum to everyone else, but it burns 600 kg/hr.

A 737 500 (which is nearer the same weight and capacity than a NG) doing the same thing approximate same weight will burn 2800 kg/hr. This is taken from the real life at work.

Some of that will be better aerodynamics because the neo and max don't get that marked a difference. But they still get a huge decrease in fuel burn but I don't have any real life knowledge that I have seen or experienced.

I do have real life experience a bit as ground crew with DC3's which were used for pollution control in Scotland. The R-2000 Twin Wasp engines were labour intensive from every level. You had 120 seconds after shut down to get 4 oil trays in otherwise it would sigh and dump its life fluids all over the apron and you would spend the next 3 hours scrubbing the concrete to decontaminate it. Pilot wise required a musician level of talent to adjust a power setting both in precision and timing. Flew it once but never landed it. And refueling it was a colossal pain , one of us used to have to go sit on the wing and hold the fuel gun in the hole. Do one wing then go do the other. Which may have just been a feature of that particular aircraft. And it uses utterly colossal amounts of petrol. From memory it took 3000 ltrs of petrol. Which gave it a range of 1300 nm in optimum conditions. low level it used to burn that in 2 hours spraying.

Just for fun when I started flying it I worked out the fuel burn per seat between the a220 and my old Merc E class 3ltr which I was getting 5.3 ltrs per 100km out of on long runs at 90 km/hr. It was getting very close km travelled per seat fuel burn. All previous types it was double at least the fuel per km per seat on previous types.

They want to add variable pitch fan blades to the next generation, but I suspect I will be in a box before they come along.

 

[TugboatEng]

Funny story, my personal truck has an engine with a known problem. The main bearing webs crack at the outer bolt holes. The cracks eventually propagate into the water jacket. I like this example because the thicker fatter stronger aftermarket has always suggested solutions that never worked. In 2001 GM gave the molds to International to continue production. International's solution was to reduce the diameter of the outer main cap bolts from 12mm to 10mm and that solved a 20 year long issue with cracks.

 

[enginesrus]

Tugboat, what engine? So they essentially added more material to that area? Less clamping force?

 

[CWB1]

Fuel burn ~ emissions, so I'd say its safe to assume aircraft and autos will both continue in the direction of less is gooder.

 

[TugboatEng]

GM 6.2/6.5 diesel. No material added, they reduced the size of the bolts.

 

[JohnRBaker]

Effectively, material WAS added since the pilot drill for the 10mm tapped holes removed less material than did the pilot drill for the 12mm tapped holes.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[TugboatEng]

This was supposed to be my weekend project but apparently it's illegal to buy a camshaft bearing tool in California and I messed up the first bearing with my homemade tool.

Anyways first pic is my dead 6.2 block. Second pick is updated 6.5 block with smaller boots on the 3 center main caps.

Do note that the first engine was removed from service due to head gasket failure and that these cracks did not cause issues when running.