Warbird Information Exchange

Hi Guys,

I'd love to hear some real-life accounts of what happens when aero engines are abused in various ways....

E.g.

High RPM before sufficiently warm
Overboost for an extended period
High boost low RPM
Incorrect mixture settings causing detonation/preignition
etc. etc.

Do you just wear your engine out sooner with bits of metal floating around in the sump or can the effects be immediate and catastrophic?

Would also like to understand why wartime emergency power was limited to X mins.....what kind of bad things could happen if it was used for a longer period and why?
Would temps become too high after this time or would components start to break?

I figure there's a wealth of hands-on experience on this forum. Perhaps some of you have spoken to current or veteran ground crew too?

Any help would be much appreciated.

Thanks!

I've removed lower cowlings on a Mustang and had small bits of pistons and piston rings fall out on the ground if thats what you mean.

Over time internal parts of these engines changed due to knowledge gained in there use and the operational requirements to produce more power to match the opposition. Fuels also changed to enable higher power to be produced with less detonation.
Rolls Royce Heritage Trust has a series of books on the various Merlin models and the changes made during the production years. Graham White also has a great book out on the various Allied engines.

Generally if the A/C is Radial Powered and covered with oil that looks like Metal Flake you had a catastrophic failure. Merlins have been known to almost saw themselves in half from the connecting rod, or what is left of it, spinning like a dado saw blade.
Under lean mixture conditions or detonation pistons will melt creating holes.

If an engine is making metal for any reason you have a sick engine that needs to be repaired.

AAFO.com has many past Reno Racing coverage archived so there is photos of various extreme problems highlighted there.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

Not done my me but, what I know about factually.

*Very cold morning, no warm-up, Lycoming I0-540: shortly after take-off the insufficiently lubricated (cold oil) hydraulic tappet seized in the bore. Result: broken case. Trip delayed two weeks.

*Deliberately set full rpm approx. 25 rpm above redline. Owner claimed a person could safely do that. There was enough margin in the design, so he could get extra power.
Connecting rod bolts failed.(after perhaps 30 hrs operation). Owner lived with no injuries. Airplane....well....

*Excessive leaning to save on fuel costs:(this is very common) torched exhaust valves.
exhaust pipes deformed enough to break or warp and cause engine compartment damage.

Thanks for the great info guys.

Any more experiences out there?

Cheers

A table of engine parts at Reno this year…. Some are virtually duplicates. I did a quick upload for someone a month or so ago……

http://gallery.me.com/tnmark/100379

Rich may be able to let us know if: (all radial engine parts)

(In photo 19)
Is the top of the piston on the right is “normal”, if not it may have had some heat damage from detonation……

(In photo 14)
Is the top of the rod bent to the right to work better in right handed radial engines?

(In photo 16)
Is the side of the piston “relieved” to allow more range of motion in the wrist pin for the con rod?

(In photo 12)
If the nuts are too tight do you normally remove the cylinder from the crankcase with a torch?

Merlin’s Magic (P-51) had some engine parts on the table in their pit, there was a piston (and I have a photo, just finding it is a challenge) of a MELTED piston, I don’t know how it stayed attached to the rod or moved in the cylinder….

Plus I have a couple shots of the engine from RELENTLESS after the engine came apart at Reno the year before.... When it came by it sounded like someone missed a shift on a superbike and the engine spun to about 20,000 RPMs (which it did when the prop came off)... Fortunately Kevin is a MASTER PILOT and landed it safely even with some weight and balance changes from the missing parts...

Mark H

_________________
Fly safe or you get to meet me .......

Mark,

#19 Neither of those piston crowns are normal. The one with the valve head in it is self explanatory...valve head broke off and made cupped the head of the piston. The other piston in the shot looks like it had some smaller hardware beating around in the combustion chamber. Piston crown should be very smooth over its entire contour.

#14 The rod was bent either from mechanical damage from something caught between the piston head and combustion chamber roof or hydraulic lock. It could very likely be the mating rod for the badly cupped piston with the valve head in it.

#16 Some pistons are relieved but not like that! That could be a fatigue failure or a stuck skirt (Clearance got too tight from overheating)

#12 No! My guess is from the damage to the lower cylinder skirt, the case was destroyed so they decided to make a show and tell piece out of it

John

Reduced power take offs in the big radials...

_________________
"There are two types of people here; airshow whores and airshow prostitutes. The whores, like you and I, do airshow stuff for free, whereas the prostitutes are paid" - Reg Urschler

No guts, no glory Those engine parts look normal,,,,, for an over worked engine

_________________
A&P/I.A., A.A.S./Aviation Maintenance technology
Warbird salvage/recovery
One day I'll get that P-40!

Glad you guys liked the pictures...... I thought the bent rod was the best. If you've never seen one in person, its one big tough (well tough looking) chunk of iron and to bend it like that takes a lot of force.......

Mark H

_________________
Fly safe or you get to meet me .......

Hi.
Always owned motorcycles,rather big bore very simple push rod,two valves per cylinder,Moto Guzzi.
I don't think they would continue to run with anything like some of the damage i've seen in the photographs,very sturdy indeed,and the radials are clearly almost bulletproof.
How can an engine possibly go on with a couple cylinders shot off and shedding big pieces ?
In a couple of the pics a valve 'mushroom' is resting on top of the respective piston.Boom boom,bang bang !
Also,what type of remedial action(s) would they need,it's clearly not just changing the offending part(s) ?

100LL & R2800 running 115/145 power = bad things.

The airplane in my avatar lost an entire cylinder (jug, piston, rod, everything) out the bottom while on a ferry flight home from a charter one day. We'd been stressing to the crews to run no more than 1100HP cruise and 50" MAP on takeoff due to the lower detonation threshold of 100LL even with ADI but some of the guys just wouldn't listen. They were constantly running 56.5" on takeoff and 1400HP cruise, power settings those engines and birds hadn't seen since the 1960's. As a result, we were loosing engines in as little as 150 hours, maybe getting 300 out of them on average between overhauls. Usually the maintenance guys would catch them before we got a failure, but it still was getting to be expensive for the owners. Finally after the cylinder I think the crews got the message and suddenly we were getting 900+ hours between overhauls.

Lesson - treat the engines right and they'll treat you right.

BTW, the stuff about reduced power in a big radial is bunk. You don't hurt the engine running reduced power as long as you're still using a charted power setting, thus why we used 50" MAP, which is METO for the R2800, and thus not doing anything unusual. I'm not sure where people started thinking limiting power usage with 100LL to METO and no more was bad for the engine, but there's no evidence to back up the claims. It's the guys who start using power settings like Stage 3 alternate climb power settings or something oddball like running 100LL and using 85 Octane or 115/145 power charts.

Ive got a cup of case parts where a #5 cylinder was once held down.

_________________
Long Live the N3N-3 "The Last US Military Bi-Plane" 1940-1959
Badmouthing Stearmans on WIX since 2005

This is not about a Warbird but it still deserves mention. I was contacted by a guy I know who has about eight general aviation aircraft and he asked if could go to Florida with him to work on one of the aircraft he has down there. I jumped at the chance, but like we all know when you see the plane it is worse than how it was described to you. This particular airplane was purchased sight unseen and he didn't even know if it could fly or if either engine would start. Anyways, the right engine had the turbo unit and exhaust removed and just laying inside the bottom cowling, while the left engine had no vacuum pump installed. After standing out in the blistering hot Florida sun for three days, changing tires, cleaning and repacking wheel bearings, changing strut fluid and adding nitrogen, fixing rear passenger door, oh did I mention that once we got there the owner told me he forgot the keys in Ohio, back to plane, checked and cleaned, regapped plugs from left engine, checked mag ,engine timing they were close so adjusted them. The owner wanted to start the left engine which I was steadfastly against, not just because the vacuum pump was gone, but also because I didn't think it would be a good idea to run fuel that had been sitting for eight years through the engine. I went over to the hangar to have lunch and visit the throne and when I came out I heard an engine running but didn't pay much attention because this airport is a busy airport. Upon walking out of the hangar the owner was sitting in the cockpit and had the left engine running with oil pumping from it. I yelled for him to shut it down, he came out of the plane and walked over and said "that's not good, where do you think the oil is coming from"? Rather politely I explained that the oil was coming from where the vacuum pump should be. So there the owner was cleaning oil off of the tarmac. I have not gone back since.

_________________
A&P/I.A., A.A.S./Aviation Maintenance technology
Warbird salvage/recovery
One day I'll get that P-40!

So,what needs to be done when an engine is ravaged like those of the photos ?
Complete rebuild,which substanties in ?

easiest but most costliest is a complete overhaul. Majority of the time the engine can be repaired. PC spills over to other posts!

_________________
A&P/I.A., A.A.S./Aviation Maintenance technology
Warbird salvage/recovery
One day I'll get that P-40!