Skymaster safety record: Engine Failures?

[w1bw]

Greetings, everyone. I'm a new member to this site, though I've lurked here on and off for the last year or so. First, thanks to Kevin and the others for making this a very useful place.

Second, an introduction...

I'm not (yet?) a Skymaster owner. I'm a 260 hr PP-ASEL-IA, and I own a 1985 Skylane. I love it. But I'm in a new phase of life which has caused me to think seriously about a twin. I now have two young daughters (4 and 2), so the stakes are raised! We also now have an island vacation home, and doing the weekly commute this summer, I've found that I'm probably spending at least 15% of my flight hours over the ocean beyond gliding distance to land, especially since this has been an IMC-full summer here in the northeast, and the IFR routings give me less flexibility in that regard.

I've always been interested in Skymasters ever since I had a high school girlfriend with one (well, her father had one). I'm currently thinking seriously about normally aspirated models. I have to ask one serious devil's advocate reality-check question, though.

There was another thread about real-life engine failures. This supported a notion that has been in the back of my mind. Anecdotally, there seems to be a very high rate of engine failures in Skymasters. It seems that almost every article I've read in various magizines include owner comments of the form: "CLT is a great thing, because when I had my engine failure(s), it was no big deal...".

In general, it's a testimony to the design that people with such experiences are happy with the outcome (at least the ones here to write about it), but it's somewhat alarming to me that no one has any trouble finding ample real-world power failures, including this forum. Sooner or later, it can bite someone. Aviation Consumer references an NTSB study which ranked the Skymaster 16th out of 20 in fatal accident rates related to engine failure. I understand that the picture would be better if a bunch of people didn't try to take off on one engine, but still....

Is the Skymaster a great concept with a poor implementation, is this just rotten luck, or are these statistics dominated by stupid pilot tricks? It seems clear the people in this forum are highly motivated by safety. I do math; I understand the sample sizes are not large, and limited past actual results don't imply that it is inherently less safe. But we should all attempt to understand why we think we will do better than those who have come before us. I'm sure everyone here has rationalized this in one way or another, and I would like to hear.

After all, if I didn't think the Skymaster would be safer for my current flying situation, I'm more than happy with my Skylane!

--bruce

[Kevin McDole]

Bruce,

You ask some good questions. The bottom line is that Skymasters do not have a better safety record than other light twins. It is not a panacea.

Why?

The majority of accidents come from two causes: fuel exhaustion and continued VFR into IMC. Centerline thrust does solve that. Skymaster pilots get in trouble in these areas just as much as others. But notice, you will not see VMC roll as the cause for an accident in a Skymaster - as is sometimes the situation in conventional twins.

Remember also, that virtually all light twins are seriously anemic with one engine out. This means that if you lose an engine on takeoff, you're looking at 200 or 300 fpm climb rates in standard conditions (as benchmarked with a new airplane). If you're already at altitude - and engine out is not a problem, but on takeoff an engine out is a serious problem. The Skymaster at least does not compound this with a control problem (asymmetric thrust)..

How often do engines fail? We all have anecdotal evidence. I remember an instructor trying to reassure me in a 172: “These engines never fail. I’ve been flying for 3,500 hours and I’ve only had one engine failure.” That was not very reassuring. Consider the simple statistics: with 2 engines, you’re twice as likely to have an engine failure. However, the chances of having both engines fail is several orders of magnitude less than a single losing it’s one and only engine. Over water – I’d certainly like that advantage. Of course, remember there is the very real possibility that what kills one engine will kill them both (bad fuel, ice, lack of fuel, etc.)

You have to start with the decision: single vs. twin? If you have made the decision to go twin, then you have to weigh just how much does the asymmetric thrust/VMC issue concern you? I think you’ll find that people on this board are very concerned with that – and as a result are fanatical believers in the Skymaster.

If you haven’t taken your multi engine training yet, that will be a good learning experience. Virtually all of the training deals with the asymmetric thrust problem. Get your ME rating and see how much the asymmetric thrust scares you. I have around 100 hours in the Cessna 400 series planes and prior to each take-off I rehearse what’s going to happen if I lose an engine. I look over my shoulder at the unsuspecting passengers who have no idea that I’m thinking about the fiery crash that possibly lies ahead. In the Skymaster I know I can control the plane with an engine out – if I am unable to climb, if there is some flat terrain ahead, I can definitely set the plane down safely.

The question is what demons make you lose sleep? If it’s asymmetric thrust, the Skymaster is the answer. Flying's no fun when you're worrying.

[Mark Hislop]

Bruce:

I can't add much more than Kevin's fine post. However, I would like to state that there is nothing wrong with the Skymaster design that would cause them to have more engine failures than any other aircraft. The claim that the rear engine always runs hot is largely an old wives tale. Some think that the Continental 360 isn't a very robust engine, but there are a lot of them out there on many types of aircraft, and if properly cared for, they are very reliable. As a matter of fact, I think they are more reliable that today's big bore (520's and 550's) Continentals.

I think you may have gotten an erroneous conclusion from the engine failure thread. Yes, there have been failures, but no more and no less than other aircraft. And an engine does fail, the CLT makes the failure much easier to deal with.

Mark

[WebMaster]

The single biggest cause of engine failure is fuel exhaustion. Stupid pilot tricks. The next biggest cause is continuing to fly, with a failed engine. An engine failure is an emergency, and should be treated as such. You would never consider taking off in a 310 with one engine feathered, yet the accident reports have mulitple incidences of exactly this sort of thing happening. The most recent one I remember was up in BC, 2 years ago, on a short strip. Like the others, it too was fatal.

I, like you, do a fair amount of travel over water, Lake Michigan. I am comfortable doing this, because I have 2 engines. Someplace else I wrote about coming out of PWK, in IMC, at night, and being kept to 3K (2300 AL) for a long time over water. Not an issue for me, I have 2 engines, 2 vacuum pumps, 2 alternators, 2 regulators. All the systems are independent, and interdependent. Mine is a normally aspirated model.

I hope that Bob Cook and Ernie Martin will jump in here, because they both have homes in the Bahamas, and fly, over ocean, a lot. They fly the Skymaster for exactly the reason most of us do, e.g., it's a safer twin. I'm hoping that Brian Von Herzin joins in as well, because Brian has flown his skymaster to Europe, on mulitple occasions. A lot of over water for those trips.

Stupid pilot tricks will get you in trouble, no matter what you fly. I have done a couple, and lived to tell about it, vowing to NEVER do that again. My wife and I enjoy our skymaster, and feel safer in it.

[Ernie Martin]

I'm one of the pilots who Larry mentioned fly over waters almost weekly to the Bahamas. I also have a Master's in mechanical engineering from Caltech and spent a lot of time researching the very issues you're struggling with before I bought my first Skymaster. Incidentally, we have another thing in common: my daughter was 6 when I bought that airplane.

So, here are my views:

1. I agree with all that is said above and the rest of the points below are largely for emphasis/expansion (read: I don't have much more to add).

2. The reliability of the Continental IO-360 engines, after allowing for the ADs that have been implemented, is indistinguishable from that of other reciprocating aircraft engines. In short, they don't fail more frequently. You hear about engine failures in Skymasters because the pilots like to talk about them, for the simplicity of recovery.

3. Because the aircraft is so easy to operate and so forgiving, many of the accidents have occured because some pilots haven't given it the respect it deserves. They hop in and fly. No pre-flight check, no visual confirmation of fuel. And because they're built like a tank, many proceed into IMC when they shouldn't.

4. The fuel system is a bit complicated and needs attention. Mistakes here have led to accidents. Indeed, in a very brief published flight report on the aircraft -- I'm talking like one paragraph long -- they included this statement: "fuel system requires familiarity" (emphasis mine). It's not a big deal, but most Skymasters have lots of fuel capacity with auxiliary tanks, and knowing how to manage the fuel system is important. I have a "Fuel Supply Management" page in my "backup" skymaster website at www.SkymasterUS.com which provides the required familiarity and where you can go read the flight report I mentioned.

5. Because they look weird to some -- perhaps not macho enough -- Skymasters are cheaper than comparable aircraft. Some people who bought this cheaper aircraft soon discovered that maintenance costs are like for other twins, didn't have the money, and skimped on maintenance. Many a Skymaster has been bought like this, missing ADs, with poor annual inspections, etc. This has led to accidents.

OK, that's the technical stuff. Let me turn to the mundane. I wouldn't fly over water outside gliding distance of land in a single. And I wouldn't be caught dead in a regular twin, principally because I'm not sure that in a failed-engine-at-takeoff emergency I'm gonna do everything that needs to be done precisely to save my family. Not if you fly occasionally, not if you're preoccupied with something else (money, time delays, spouse hassles) at take-off. I want the extra margin of safety.

But the basic principles of flying remain. If you treat it for what it is -- a complex, high-performance, retractable-gear, variable-pitch-prop, twin engined aircraft -- and if you maintain it properly, and if you do thorough pre-flights, and if you stay proficient, then the Skymaster is indeed a very safe aircraft, probably much safer than other twins.

Ernie

[w1bw]

Thanks for the thoughtful responses. As I said up front, I'm being intentionally provocative in order to get to the bottom of a little lingering doubt, but I'm 90% convinced that the Skymater is a good fit to our future flying needs.

So let me follow up with some real data. I spent an hour or two this morning going over all the fatal Skymaster accidents over a 20-year period (1 Jul 83 to 30 June 03). This isn't anything definitive (just my conjecture), as I am making pretty quick judgements from the NTSB synopses. but here is what I found.

There were 40-something fatal accidents in Skymasters over that period. I'll throw out the ones for which cause was unknown, or the two shot down by Cuba, or the pilot who died of natural causes in flight. Here's what we're left with:

9 vfr->imc or scud running
6 controlled flight into terrain (5 night, 1 low-alt maneuvering)
5 low-altitude stalls (1 departure, several circling maneuvers of various kinds)
4 other loss of control (incl spatial disorientation)
3.5 fuel exhaustion, mismanagement, or contamination
3.5 single engine takeoff attempt
2 mechanical problems (1 engine failure, 1 cockpit lighting failure at night)
2 extreme wx (icing, thunderstorm)
1 midair collision
1 oxygen problem (amazing story)
1 bad landing
1 hit terrain on go-around
1 departure with control locks in place

Since I specifically brought up numerous anecdotal stories of engine failures, I'll note that only one fatal accident definitely involved an engine failure in flight. The pilot noted falling oil pressure on rear engine, turned around to go back to home airport, made it as far as the pattern before the engine failed, but he mis-judged the approach (too high) and tried to go-around. He did not successfully maintain altitude and landed in a pond.

There was another loss of control in which the pilot reported a problem (no specifics) shortly after takeoff into IMC, then lost control. No problem was identifiable from the wreakage. And a third in which a pilot reported an engine failure, but everything appeard normal from the wreakage after subsequent flight into terrain in IMC below minimums; both engines appeared to be developing normal power at time of crash.

There were also several of what I call Stupid Pilot Tricks above and beyond poor judgement of vfr->imc, etc. Two aircraft had no record of maintenance over the last 5 and 10 years, respectively (and pilots to match). Several single-engine takeoff attempts. One pilot had no license at all, and two apparently had no multi, and one was not IFR current. And one departure with control locks on.

Of the single-engine takeoff accidents, two were clearly intentional without starting one engine. Another was unclear whether it had been running in the takeoff roll, but it wasn't at liftoff. And another was known to have only partial power on the rear, but took off anyway, only to have the front quit shortly after takeoff because of water in the fuel; this is one which hadn't been annualed in many years.

Then there is the most amazing story of the Skymaster which got normal air rather than oxygen in a refill...I assume we've all heard that one.

All-in-all, I find this exercise reassuring. Skymaster systems didn't seem to play large role in the accident data. Most are the usual suspects.

--bruce

[WebMaster]

Excellent Analysis.
The oxygen one was most amazing, pilot died, but passenger lived. That's probably the only reason they figured out what happened. Breathing compressed Air. 18% O2.

A note on icing. Winter before last I was learning to fly our skymaster, and working on IFR rating at the same time. One of my training flights was night, in IMC with rain/ice. Landed with 4 inches of ice on the front of the radome. The deice boots worked, but we had so much airframe ice that the airplane had to be pitched up to maintain altitude. Not something I will ever do again. Many of them have de-ice boots on, but none of them are certified for flight into known ice.

[Bob Cook]

Can't add much.

One accident (survived) when a 337 bounced off the ocean during a routine patrol (out of florida). Returned to Miami with bent props.

second one, bounced off an ice buildup in the artic. ripped off rear prop, bent tail, smashed gear doors. Landed safely with a bent front prop. Pilot complained of excess vibration.

After an engine failure, the good engine takes you to the airport... not much more can be said. I fly over lots of water all the time.

Ernie.. my fuel system is either "on" or "off"... not very complex.

Bob

[Ernie Martin]

Bob:

I agree that newer birds have easier fuel systems. Like yours, my 1973 337G just has NORMAL, CROSS-CONNECT (to the opposite tank) and OFF. But my 1969 337D had auxiliary tanks, so you had NORMAL, CROSS-CONNECT, AUXILIARY and OFF, and it's the management of such systems that require more attention.

BTW, even our "simple" fuel systems should be understood to safely use the cross-connection feature. For instance, why you shouldn't cross-connect until you've made room in the normal tank for the returning fuel/vapors, and why in single-engine operations, if you cross-connect so as to utilize the fuel originally intended for the failed engine, that tank will run dry twice as fast as you expect. But it's true that the newer systems are much simpler.

A thought to Kevin, given the valuable statistics compiled by Bruce, is to change the name of this thread to "Engine Failures and Fatality Records", so this thread will pop up when people do searches on these words.

Ernie

[Frank Benvin]

Even the simple fuel system can bite you. Our friend had a 1973G. The tanks would cross feed on the ground so he would fly both engines off one tank to even them up. Dad went flying with him one day and saw him do this and warned him not to. Well they flew across the pond 32 miles in our 337
to pick up his 337 on the way back flying at 1500 feet together dad hears him call an emergecy. Double engine failure. He ran the tank dry.He was able to light them back up a few hundred feet off the deck and make it home.

Frank

[Kevin McDole]

I don't know about the '73 G model, but my '77 P337 is placarded such that takeoff & landings must use the "non-crossfeed" setting. The front engine must be set to left - and the rear must be set to right.

[Ernie Martin]

Kevin:

In the '73 it's not placarded. It's in the POH but not on the panel. And systems like these are in most twins. Yet people make mistakes.

Ernie

[Jose L. Ichaso]

Bruce,

After finishing my flight instruction for private and instrument rating on 172`s and 152`s, and knowing in advance I would be flying overwater to islands 30 to 100 miles offshore, mountain areas, and over rainforest, with my wife and then my one year old son, it was a quite straight to go to a multiengine, and easier to get to the Skymaster. I agree completly about Ernie`s statements, and after six years and two more kids ( 1.6 years and 3 month girl ), I love more than ever my choice and my machine capabilities. Here I attached a document about the safety record of the Skymaster I kept updated until 2002. Hope this could help you, and anyone who visit this site.

Best Regards,

Jose L. Ichaso