Radial vs liquid cooled engines

[swampyankee]

I have flown only single engine stuff, but I do know when you have an engine out on a twin you also pull out the running engine as well, back to low to no power and recover then slowly add the power. And not doing so is why an engine out on a twin can bring it down.

Some time ago, when I was trying to get a PPL (and before I found that migraines are disqualifying), I found it written that light twins had higher accident rates than comparable singles.

 

[gumbyk]

Sure glad the FAA doesn't agree with you, if they did all the jet passenger aircraft would have 4 engines again.

You don't seem to understand the difference in reliability between turbines and piston engines...

 

[gumbyk]

Agreed. That's why the company reverted to modified 172's for the role. Far better downward visibility, and far lower maintenance costs, even with the extra fuel tank STC's. But somebody had the brilliant revelation that a twin would be safer. And they then selected an aircraft with props swinging in the same direction, so if you lose the right engine, you lose rudder authority.

That's what Vmca is for; above this you have enough rudder authority, below it you don't. You may not have enough power available to maintain height, and if you're low, the natural instinct is to try to maintain height, and the speed washes off.

 

[PWR4360-59B]

You don't seem to understand the difference in reliability between turbines and piston engines...

I just find it so funny that just because I won't agree with something, I am then told I don't understand something. What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it. And that is one of the main reasons for the reliability issues. Actually the turbine parts are under way more stress than the recip parts and if they were not replaced on a certain schedule then turbine reliability would not be so good. I've heard the turbines have high TBO's because the critical parts changes are just considered normal maintenance.

 

[Shortround6]

I just find it so funny that just because I won't agree with something, I am then told I don't understand something. What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it. And that is one of the main reasons for the reliability issues. Actually the turbine parts are under way more stress than the recip parts and if they were not replaced on a certain schedule then turbine reliability would not be so good. I've heard the turbines have high TBO's because the critical parts changes are just considered normal maintenance.

A lot of what you seem to believe sounds like it is based off of things you "heard".
Not read or to found in maintenance manuals or factory maintenance publications /notices. People are objecting because a lot of what you "heard" runs counter to what most everybody else is hearing.

A generic manual for the P & W PT6 engine can be found here: http://www.caijets.com/pdf/KnowYourPT6A.pdf
specific manuals for individual engine models may be harder to come by but this seems to have some decent information.

I would note that a some Lycoming and Continental flat fours and sixes only make to their suggested engine lives because "critical parts changes are just considered normal maintenance". Like changing cylinders on an individual basis if they develop cracks before (hundreds of hours before) the lower end reaches it's overhaul life limit. Since large radials have been out of normal service for decades getting information on engine life may be a bit difficult leaving us with what was done in the 40s/50s/60s.

 

[Clayton Magnet]

A generic manual for the P & W PT6 engine can be found here:

Don't forget the "C" in P&WC, its the most important part

 

[gumbyk]

I would note that a some Lycoming and Continental flat fours and sixes only make to their suggested engine lives because "critical parts changes are just considered normal maintenance". Like changing cylinders on an individual basis if they develop cracks before (hundreds of hours before) the lower end reaches it's overhaul life limit.

The Lycoming IO-360 platform is fairly bomb-proof now - 4,000 hrs TBO isn't uncommon (without cylinder changes) if its de-rated to 160-180 hp.

There isn't a modern piston engine (that I'm aware of) that is able to be run 'on condition' like turbo-shaft type engines are. The Honeywell LTS series of engines had the lowest component life of 5,600 hours from memory, it was all higher than that for everything else.

What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it.

Have you ever been to or worked in an engine overhaul shop? I know a lot of people who would disagree with that insult you just threw out there.

Please, back up 'what you heard' with some figures, even of they're from memory.

 

[PWR4360-59B]

The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
Engine shop? Yes not aircraft though.

 

[wuzak]

The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.

So, piston engines are better because they are more complicated and harder to put together?

Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.

Ignoring the many thousands of people who have built up engines in their back yards, many of whom have done so with good instruction manuals rather than deep technical understanding.

Ease of assembly is a result of good engineering.

 

[gumbyk]

The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
Engine shop? Yes not aircraft though.

BWAHAHAHAHAAA!!!!

REALLY?

Sorry, you just showed your ignorance....

 

[Ascent]

I spent five years in the engine bay at RAF Marham doing engine strip and build, nice to know that the RAF could have saved a fortune on mine and my colleagues training.

Gas turbine maintenance is a very technical job despite what you may think.

 

[fastmongrel]

I spent five years in the engine bay at RAF Marham doing engine strip and build, nice to know that the RAF could have saved a fortune on mine and my colleagues training.

Gas turbine maintenance is a very technical job despite what you may think.

But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers

 

[soulezoo]

The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
Engine shop? Yes not aircraft though.

Having worked on both Turbines (TF-33, CF6-50C2, J69) as well as light aircraft recip (A & P licensed mech), I know what it takes for both. I find this post insulting and ignorant. (On edit, I am thinking he probably thinks blade blending is what you do to add wheat grass to your margarita)

 

[soulezoo]

But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers

You may appreciate this...
On the CF6-50C2, there is a part colloquially referred to as the "motorcycle engine" (resembles a cylinder from an old Triumph or Norton) amongst other things. This "motorcycle engine" is an integral part of the operation of the thrust reversers. In another parallel universe, a looong time ago, when in a hostile environment a long way from home, I had to resort to a hammer to unstick this damned thing so we could get the hell out of Dodge. Definitely not a tech manual moment I was proud of. But we got out.

 

[Ascent]

But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers

To be fair children with hammers is probably a good description of half the lineys I worked with.

(For the non RAF types, lineys is the nickname for the flight line mechanics)

 

[soulezoo]

To be fair children with hammers is probably a good description of half the lineys I worked with.

(For the non RAF types, lineys is the nickname for the flight line mechanics)

Glad you spelled that out. I first read that as "Limeys". I was thinking, "well who else would you expect to be there aside from Limeys?" LOL sorry, no disrespect intended.

 

[PWR4360-59B]

Truth always hurts.

 

[MiTasol]

Here's one for the air cooled crowd. And a picture.............is worth a thousand words. Oh, and I realize I just kinda stuck this in here so I apologize for that but a friend asked me to post this here so......I did.

Good photoshop job. It is a spare cylinder still with the transport blank and desiccant plugs in it

 

[MiTasol]

The thing is, if this happens in a mono block, the engine quits. Radials for the most part have a habbit of continuing to run for quite a while after this happens.

Except that on a radial when an articulating rod breaks the end attached to the crank often flails around and beats the sh*t out of the inside of the crankcase and the disconnected induction tube allows large volumes of fuel air mixture to vent to atmosphere totally disrupting the mixture ratio -- one or both causing the engine to stop instantly. And yes I do know from first hand experience.

 

[MiTasol]

With all the anecdotes in this thread about P-47s, F6Fs etc making it home having lost a pot in combat, it has to be asked, was the R2800 especially prone to losing cylinders due to combat damage? Maybe the lack of stories about Spitfires coming home with pistons hanging out the top of the engine just reflects that the Merlin didn't lose cylinders.

Losing a pot does not mean it became totally disconnected like shown in the Photoshop picture. Usually it means the head disconnected from the barrel due to damage or cracking or one of the pushrod ears broke off through the rocker arm pivot bolt holes due due to damage, cracking or over-torquing the rocker shaft bolt.