Loss of an engine
 

Sometimes, and hopefully all the time, the loss of an engine is something we train for but never have to actually use. Well after 35 years of flying, I had my first engine out. I took off Sunday with the intention to visit a number of airports for the MnDOT aviation passport program. I left the Austin, MN airport where I keep the plane in the winter and landed at Owatonna. About 10 min after taking off from Owatonna I noticed my oil pressure on the rear engine dropping, and then bouncing from just above 0 to the bottom of the green line. I made the call to shut off the rear engine and secure it.

The flight from that point back to Austin was about 12 min. It was a quieter 12 min than normal with a lower airspeed but tracking solidly at 3500'. Greased it in back at Austin. I felt totally comfortable and didnt think twice about my actions. The plane flew hands off and going through the check list was a piece of cake.

Something let lose in the oil system, had oil everywhere inside the cowling and on the outside of the plane.

As they say, bad things come in 3's:

1. loss of an engine
2. The tremendous oil loss was on the main wheels. After touchdown, and on the roll out and breaking, the tire rotated on the wheel shearing off the valve stem and giving me a flat tire which is interesting at 50 mph- had to put on a loaner on the taxiway to get it to the shop
3. 5 planes in the shop ahead of me.....3 of which have no engines. Mechanic said I will be grounded till around February......

The single engine flying was amazing and actually pumped me up about the abilities of the Skymasters. The whole ordeal was a nonevent and I struggled way more with the flat tire than the loss of the engine. I love them!!

Fine job Tom. Bummer about the failure but yes, this is why I own my SkyMaster for 19 years and counting. They do offer reassurance in the event of the failure you just experienced. Good luck with the repair and please report back what actually caused it.

Thanks,

Ed

Good job Tom - and thanks for sharing. Glad to hear that you stayed focused and professional with the engine shutdown. Look forward to hearing of the cause.
Jeff

Were you able to fully feather your prop? (I keep wanting to ground test my feathering mechanism, achieve full feather, but they have it designed so you can’t do that.)

Good on you for keeping the oil pressure gauges in your scan. You may have saved yourself a much larger bill.

I'd be willing to bet your leak is a pretty simple fix. I'd bring in another A&P before I let my airplane sit for three months because the one shop is backed up!

oil pressure
 

Tom - super glad to hear it worked out to be a "non-event". I have a T337C and had an eerily similar situation. Turns out that it was the little oil feed line going into the top of the turbo on the rear engine. You might check to see if yours is cracked or has a hairline fracture. If so, voila - less downtime. BUT, do not just replace it with the same part number. The newer model T and P planes came with a stronger more reinforced feed oil line to the turbo. It is legal to upgrade to that part....also make sure you change out the check valve if you replace that line, with the newer check valve.

In any case - fantastic news that all is well. Better to be on the ground wishing you were in the air, than in the air wishing you were on the ground : )

follow up
 

Thanks for the comments! To follow up with some of you:

1. Mine is normally aspirated so no turbo oil line

2. Yes, the prop fully feathered. The plane almost leaped forward as soon as the prop feathered.....the drag was VERY noticeable. I can see why you gotta get them feathered ASAP on an engine loss on take off.

3. Mechanics are slim pickens around here no others at this airport and no way to get it to another airport.....and the places I am familiar with at those airports are backed up as well. My best shot would be a "mobile mechanic" and I havent heard of any around here, but it is something to look into. However, with the holidays and winter coming (lots of snow up here typically) it doesn't bother me too much. I have access to a 172 so I will still be able to get in the air. I like living in the rural part of the country, but it does have its drawbacks.

4. Based on the amount of oil lost in short order, it would seem to be on the pressurized system unless there is a gaping hole in the case, which I doubt - the engine was running normally otherwise. All of the oil is on the passenger side, and I am thinking oil cooler. I have Air Wolf remote oil filters front and back, so nothing related to the F and M oil filter adapter - and besides, that unit would be located on the other side of the engine where there is only residual oil from the other side.

5. Engine instruments are part of my scan. Its never more than a few min between flying and looking at the engine instruments and fuel levels. My pressures and temps are rock solid and the pretty much the same all the time. So it is very noticeable to me when something is off.

We have snow forecast for Friday, so he will not be busy fueling planes this weekend and I offered to help him out with both my plane and his backlog. He took me up on that so hopefully will be starting with him this weekend. I would at least like to get it degreased and get the side and top cowls off and really take a closer look and see if we can see anything obvious and go from there.

I will keep the group updated as things progress.

My guy is also solo. (Although another with his own customers just entered the shop.) nothing would get done if I solely counted on him. He’s covered up. And they consider the skymaster weird, different and difficult bird. (I see that, can’t memorize it like a 172 seen over and over again.) Fortunately he’s not too bashful taking care of a couple warbirds with very unique problems. So the deal is I launch in and do the work. I compensate (without him asking) even if he doesn’t touch it, for oversight and keep him in the loop but try not to slow him down. These guys are getting farther and farther between. The young crowd doesn’t seem to want to do it.

Perhaps it came in 4's. You always hope for the front engine to be the failed one...

Having said that, your tale certainly inspires (kudos and) confidence that either can be a "nonevent".

Well done Tom! I wish for airplane a speedy recovery!

Thinking out loud here. You say you shut down engine at bottom of the green oil pressure which should be adequate lube. No mention of engine running badly. You didn’t say if committed to a tear down. If find oil leak and repair it, maybe a really good inspection (with good results) will get back up and going sooner than February? Perhaps a quick decision point would be pulling the filter this weekend and looking for metal. Then checking for cracks (case, cylinder). Might quickly categorize as major vs a leak repair and back into the air sooner.

update
 

To clarify, my oil pressure had dropped to the bottom of the green and was then bouncing between about 10 psi (there is no "10 psi" indication, but it was just above 0) and the bottom of the green.

On the advice of one of the other members I am working with the mechanic for me to do the work and he will look over my shoulder. I will be starting work on it next weekend starting with the oil cooler and oil pressure line. Based on the rate of oil loss (4 quarts in about 6-7 min) it has to be a pressurized part of the system OR a monstrously large hole in the case. All the oil is from the back half of the engine so it is not the crank seal or the prop governor system and the rear engine does not have an unfeathering accumulator. I am hoping for a smoking gun - cracked oil cooler/blown gasket. I doubt it is the oil pressure line as that is small and the gauge was still working, albeit low and fluctuating.

Even if I have to pull the engine, me working on it with his assistance will get it hammered out before he would be able to get to it.

I have rebuilt a lot of hot rods and bracket drag cars and no less than 25 car engines, so I am not a stranger to a wrench and safety wire and reading a maintenance manual, so this is easily in my wheelhouse. In fact it kills me that I cant legally change my own starter!!!

I will keep the group up to speed on what I find out!

My experience be it correct here or not.....if the rear engine alternator nuts ever come loose, the alternator will drop and let the oil out, just throwing it there.....happened to me IN MEXICO.

Excellent! Another easy thing to check, thanks for the insight!!!

Does your bird have the engine access hatch in the rear firewall? I've heard of A&Ps that didn't know it was there and caused themselves lots of extra work. Use it if you've got it!

smoking gun
 

Well, every now and again things just come together. I took off the cowling and looked at the back of the engine and found a gaping hole where a mag should be.......see attached. The drive gear was dislodged and stuck between the mag and the accessory case. I pulled the gear out and amazingly enough, found all the other parts to the drive side of the mag in the bottom of the cowling. All the bearings were still in the gear as well, and no marks on it. I am having a hard time figuring out how all that stuff ended outside the engine instead of all ground up.......My lucky day????

Obviously the nuts that lock down the mag just dont fall off in 1 minute - they work themselves loose, so this had been happening over time. My plane had been leaking more oil this year than last year, and I am going to point the finger at one of the mag hold downs coming loose. The other hold down was still in place, and must have been enough to keep it from rotating and messing up the timing. All my pre-flight mag checks are accompanied with a 75 rpm drop, match by both mags.....so no timing issues.

I spent the day taking off the cooling baffles and getting access to the mag. Next trip i will bore scope the accessory case to make sure all the gears look fine, remove the mag, check the parts and order any replacement items.

As a followup to mshac, my plane is older and does not have the access panel. It is on my list of things to do though......

Glad to know you got it figured out. How about a pic of all the parts you found in the cowling?

Like you said, those nuts didn't come off suddenly. Not sure how long ago your last annual was, but I'd be a little suspicious that the mags were checked properly.

I once had a mechanic forget to tighten the plugs after an annual. He had them in finger-tight. During the flight home, one of the plugs blew out of the cylinder. It was a Tomahawk, so only three cylinders left, and running rough as a cobb. I declared an emergency and limped to the nearest airport in a controlled decent as I could not maintain altitude.

Suffice to say, I never used that IA again.

Did the rear mags not too long ago. Those hold down bolts are tough to get to and can see where someone may not have got one “tight tight”. Be careful on reassembly. Don’t be bashful about removing parts to get good exposure.

Without that rear access panel from the cabin (I don’t have one) accessing the rear magneto is problematic and probably what earns the skymaster reputation of “difficult to work on.”

This is not the first time on this forum we have heard of nuts coming off the accessory case on the rear engine. All these are hard to get at spots - so it is important to use NEW lock washers or NEW locknuts when installing mags, Alternators, etc.

Not so much on piston engines, but high frequency vibrations can also back nuts off the studs. I suspect though in your case Tom, it may have been worn out or improper hardware.

Done - but engineers shouldnt set timing
 

The plane is done and put back together. Initial run up was good. Gonna fly it this weekend to verify oil leakage. Installed all new hardware on the mag, including the rubber drive gear bushings. The cost of aircraft parts is crazy....the rubber mag bushings are only $6 a piece (which surprised me how cheap they were), but the junky little snubbers that are mounted on the #2 cylinder valve cover and push against the oil cooler are $125.........that is crazy.....But from what I have read on them, you need to replace them about every 500 hours so they dont wear on the oil cooler. So I took care of that as well.

I spent over an hour trying to time the mag so that the lights and buzzer would indicated that they are EXACTLY in time. I got it where they were within about a 1/8" (at the end of the blade) rotation. Finally the mechanic grabbed me and the buzz box and took me to 3 planes with the cowling off and showed me that none of them set the box off at the EXACT same time.....he said that if I could get them to do that I should buy a lottery ticket. When I read both mags should be timed at 20 degrees, the engineer in me says that what they really mean is 20.000000 +/- 0.000000 degrees........

I am excited to be in the air again and am thankful that my mechanic is open to supervising my work. Thanks for the input on this project!

This all sounds like good news. Good luck with the flight Tom! Report how it goes!

Famous Skymaster lines...
 

As I heard it said,

a Skymaster had an engine failure in Vermont, over the mountains, in winter, IFR at night.

The Controller asked, "Are you declaring an emergency?"

The Skymaster pilot replied, "No, I am declaring an inconvenience"

--

You are flying IFR, or night, or etc, and hear a loud 'clunk.'

Complete the following sentence, "Darn, I wish I was flying in a __________"

tough nuts
 

Tom,
Those mag hold down nuts are a bugger to get torque properly. I'm not surprised that they came loose. Hopefully you got the engine shut down in time and no damage.

When we got our 336, the mag mounting gaskets were shot and leaking all over the place. It was a pain to get the mags removed and replaced and properly torqued. Gotta take a lot of stuff off to get access to those nuts. Can't hurry it, just gotta bite the bullet and take stuff apart.

Steve

access
 

You are 100% correct....you have to remove things and take your time. Removing the baffling (which you have to remove other stuff to get out) lets you at least see the inside nut/stud. I taped the washer to a flexible shaft to be able to get it in there and slip it over the stud. The lock nut was easy enough to stick in a socket with an extension and get that in there - just have to find the right extension combination so that it is a little longer than the mag, but not too long to hit the firewall.....then it is one click on the ratchet at a time as you spend the next 5 min getting the nut to snug up......

With one mag out, the other is much easier to get at - I re-torqued those nuts too.

The alternator looks like it would be super fun to get out of there..........

I sometimes wonder, while shoulders deep on the rear engine of a Skymaster……
If the Wright brothers had to work on the rear engine of a Skymaster, if they’d say…..”Let’s just stick with bicycles!!”
Lol🤪🤣

I bet that rear engine access hatch mod is looking really attractive right about now...:cool:

It is to me.

Last I checked, the STC for that access hatch was pretty expensive.

I am sure the STC is somewhat costly in comparison to what it is - cutting a hole in the firewall. I think Aviation Enterprises is the only one that has the STC. I have not talked to them yet, but do you remember how much it was?

I wonder if you could buy one off a parts plane, like that yellow P-model that's being parted out on here? I attached a pic of the access hatch on a pressurized model, I have no idea if its different on a non-pressurized.

STC?

As far as I can tell it would be a minor alteration. Many Skymasters have that access panel.

Dan

I asked Owen about this earlier this week, and he is currently offering (through December) the kit for $2k, down from 3k, and $2.5k for installation vs 3.5k normally.

What is required for installation??
 

I can see the benefit, but $4,500 installed buys a lot of AP time.

How complex to install?

Any installation manual available to get an idea of it?

There's a theory in the Bonanza world that if an option was offered on a later model, it can be added to an earlier model without an STC. There's reasonable limits to this line of thinking of course.

An example is installing a modern instrument panel in an older Bonanza. This is done frequently, and I don't think there is any STC for it. You just do it.

Same thing with switching out the early nose gear brace with a beefier one from a later model. Again, you just do it. Its a factory part approved for later models.

Or upgrading the controls to modern ramshorns - you just do it.

There are many other examples I could cite, but you get the idea.

This line of thinking could potentially be applied to the rear access hatch.

A couple years ago it was around $4000 for the rear access hatch STC when I talked to Aviation Enterprise without install. Was looking at a number of items they had or had STC for. As reported, price is down. However, get nervous thinking about cutting that rear firewall. Would hate to contemplate replacing it if something screwed up.

I also have to get some real world feedback on the impact to cabin noise. Sure enough, there is the argument to be made that all bets are off on noise issues, at least on early models. But noisier is worse no matter how I slice it, ANC be damned.

There can be no arguing this point. The inner conflict comes in when you try to get a price check on the safety aspect of it. You unfortunately cannot pay an IA to not get frustrated and give up early when checking the two bolts on that mag.

I think Owen's estimate on labor was 40 hours.

Access hatch…another line of thinking
 

AC 43.13b gives some good advice on making repairs to metal skins and structures. Imagine your rear non-pressurized firewall had corrosion or a crack and your remediation efforts resulted in a hole in the rear firewall. A forward-thinking A&P & IA team would be expected to fabricate an acceptable repair to that area, consulting the appropriate service manuals. The same enterprising A&P & IA team could agree to make the repair removable, thus creating an access hatch where one was not previously. Such a repair would probably be a minor repair logbook entry or at most a major repair needing a form 337 citing the appropriate repair manual as approved data.

I like the way you all think! As we know, if you look in the FAR definitions, "common sense" is not listed. The old models do not have the embossed area like the picture of the pressurized version. Based on the description of the STC, it appears that you cut the access hole, reinforce it with angle and then add nut plates to which a cover/seal would be screwed down to.

Unfortunately in this day and age, it is harder to find a mechanic willing to do minor alterations. I have also heard of other mechanics going through log books and disagreeing with the previous mechanic who did something as a minor alteration. That was the subject of an article in AOPA's legal section.

I think it is a good addition, but until I get it installed I am just going to have to ask the mechanic to spend the extra time and take out the baffles to check all that stuff and charge me for it......