Second engine is only guaranteed to get you to crash ??


#1

Every time I hear this I JUST SHAKE MY HEAD :frowning:(((

ON ANOTHER NOTE: “a second (piston) engine is only guaranteed to get you to the scene of the impact”

This statement is SOOOOOO not true I’ve had 2 engine failures, one in a single engine which resulted in an off airport landing and $65K worth of damages and no airplane for 8 months. One engine failure in my twin during climb out IFR 900ft ceiling with a safe return shooting the approach and landing without loss of life or limb. Thanks to a second engine and SIMCOM recurrent training every 12 months.


#2

That’s called “denial”.

Your statistical pool consisting of one member is meaningless.

Nor do I have any doubt that your annual recurrent training was mandated by your underwriter.

Regards,

James


#3

Did I miss something here? Seems like I walked in on the middle of a conversation and both people are talking to someone else… :slight_smile:


#4

I must have missed the same thing as you, BT. I thought I’d left that discussion back in a different room, but as I walked into this one, there they are again, talkin’ ‘bout the same ol’ thing.


#5

There is always somebody who will argue for the sake of arguing (like my wife).
The old 1 engine vs 2 engine argument has been around forever.
My observation is this: Anybody who claims that 1 engine is safer than 2 probably can’t afford to fly a twin or go to Sim training :slight_smile:

If my wife and kids are going to be in it I would prefer 2 engines regardless of “who” requires the annual training.


#6

I don’t recall anyone saying that a single engine aircraft is safer than a twin, just that a twin engine aircraft isn’t inherently safer than a single.

Yes, it’s an old argument.

Regards,

James


#7

Certainly pilot experience, skill, and maintenance are major factors. However, there is no question that you are twice as likely to experience an engine failure in a twin aircraft than in a single. The odds of an accident in the post-engine-failure scenario are what is questionable.


#8

Good observation. Hard to argue with. Any It will cost roughly twice as much to operate.


#9

2000 GA Accident Aircraft Data Used in Annual Review: ntsb.gov/aviation/2000_GA_An … w_Data.xls

2000 is the latest year for this annual synopsis.

More aircraft of ALL types were lost due to loss of control, either inflight or on the ground, than loss of engine power.

Of particular interest is how many aircraft, of both types, were lost or damaged due to “Loss of engine power (total) - nonmechanical”, an FAA/NTSB euphemism for running out of fuel!

If you don’t have enough fuel on board to refill your Zippo, it really doesn’t matter how many engines you have hanging off the aircraft.

The number one cause of aircraft loss or damage is due to collision, either inflight or on the ground, again something that isn’t helped by how many engines you have.

Measuring an airplane’s inherent safety by the number of engines it has is naive, at best.

Regards,

James


#10

That’s an intuitive statement, Daniel, not a statistical one. It depends on the engine. If the single engine in a plane is rated to fail once every 4,000 hrs and the twin engines in another plane are rated to fail once every 6,000 hours, one would think the engine failure in the twin would be only 2/3 to 1 1/3 times more likely than in the single engine plane.

However, the odds of having a double engine failure are infinitely greater in the twin-engine plane than in the single. That statistic could be enough to generate a phobia for some fliers.

(As any pilot will recognize, I have NO idea how engines are rated for failure probabilities.)


#11

Aircraft engines aren’t rated like hard drives (MTBF=Mean Time Between Failures). They quit when they quit. If there was a way to predict it somebody would get rich.

They do have a TBO (Time Between Overhauls) but that’s a guess at best. It is usually 1600-2000 hours and varies with the model. Many fail before TBO, some make it past. Depends on a compbination of how the engine is manufactured, maintained, operated and fate. Especially the fate.

Anyway, when there are two engines on an airplane, they are always the same model, perhaps counter-rotating. That always means the failure odds are twice what one of that model engine would be.


#12

Anyway, when there are two engines on an airplane, they are always the same model, perhaps counter-rotating. That always means the failure odds are twice what one of that model engine would be.

I wish I were a better statistician than I am. The odds of any engine’s time to failure is a Gaussian (bell-shaped) curve centered on expected mean time to failure. If there are enough statistics, you can get a meaningful Standard Deviation. If the manufacture of the engines is tightly quality-controlled, the SD will be small and the curve will become high and narrow.

I believe that it’s the 2 SD point that contains 99% of the area of the curve. In other words, there’s less than a 1% probability that the engine will fail earlier than (Mean hours - 2 SD). With a narrow curve, that’s not going to be at the ‘50% of engine life’ mark.

If there’s no significant chance of one engine failing at 50% of its expected lifetime, the failure odd of two engines is not twice the failure odds of one engine. In fact, if both engines are installed new at the same time, it’s reasonable to expect that one engine will fail before its mean expectation time and the second will fail later than its mean expectation time. Thus, for a new plane, the odds of the first failure of an engine is little different from the expectation of the time of failure of the engine in a single-engine environment. Certainly not twice as likely; maybe just 20% more likely.

Now as the plane ages and the engines acquire different repair histories or if one engine is replaced before the other, then the peaks of the mean expected failure curves drift out of sync with each other. In the WORST case, they get 180 degrees out of phase with each other (like offset sine curves). Then, and only then, are the odds of engine failure twice as much with two engines than with one.


#13

Or in other words, they quit when they quit. :slight_smile:


#14

But always at the most inopportune time!

Is there anyone who didn’t already know from scuttlebutt that your IP would reach up and pull the throttle on an engine on climbout when you were getting your multi rating??

It was a real Chinese fire drill for me when they did it if I was under the hood and fighting my learning curve.

In the Caribou it was a non-event, as long as you weren’t at MTOW or H&H. Just feather the affected prop and POR.

Regards,

James


#15

That’s a hard statement to argue with. :laughing:

It’s sorta like the world I’d spent ten years working in – stocks.

Stocks go UP …or…
Stocks go DOWN

Whoopee! :laughing:

And then someone wants to apply statistics to it. DUH!


#16

Actually I think the person up the thread who said that pilots in the “single is safer” league tend to be those that can’t afford to fly twins is probably closest to the truth. I would feel safer in a twin assuming that everything to do with my technique is in top shape. The problem is that time and money don’t allow for that. Chances of being at the top of your game in an engine out incident in a single is simply better for pilots of my experience (700 hours/20 years/comm/multi) and inclination than is likely in a twin.


#17

I wouldn’t think you are twice as likely to have an engine failure in a twin vs. a single because ON AVERAGE wouldn’t twin’s have better built engines with better quality components, have more precise fuel delivery, probably more likely to be hangered, more likely to have constant speed props, less likely to be flown at full throttle, be treated better because of a higher time/knowledge pilot (incl. better starting procedures, being cooled better when needed (cowl flaps), not shock cooling on descent, watch for overheating, watch fuel level, etc.), and probably maintained better because the average twin owner has more money to do so, and possibly because he has more knowledge on maintenance then the average single engine pilot. On average.
And I’m only referring to piston engines.


#18

I have about 2500 hour Total Time, about 200 Multi, and currently fly a single engine airplane. Its not always about single versus multi though. Turbine versus piston is another factor. I feel tremendously more comfortable flying the PC-12 than I ever did flying a piston twin, like a seneca, or seminole, or cessna 310, or 402. The PT-6 is one of the most reliable engines around. As for “a single driver cant afford any better,” tell that to F-16 drivers. or Steve Fossett (the globalflyer)
A lot of you who think that 2 is always better than 1 are living in the past. Thats exactly how we all used to think. If 2 is better than 1, then 3 must be better than 2, and 4 must be better than 3 and so on. If more engines is safer, why the hell would anyone want to fly in a death trap like the 757, 767, 777, 320 series etc with ONLY 2 engines?
In a perfect world, every multi-engine pilot would always be at the top of their game, and handle an engine failure textbook perfect. But it is not a perfect world, and many pilots lose proficiency in engine-out procedures soon after passing their checkrides.
Ignoring safe landings following an engine failure of either a single or a multi (because if if it was landed safely, theres no record of it), If a multi engine airplane were to crash following an engine failure, it almost always results in fatalities. Why? In a single you really have no choice in the matter. Engine fails, pitch for best glide, attempt re-start, aim for flat spot. When a multi crashes it is usually due to improper procedures, namely, getting too slow and flipping over. I have read countless reports of a twin with an engine failure, but in flyable condition, crashing on short final, or after attemping to go around, or immediately after takeoff. This usually is the result of getting below Vmc and flipping over. (i can somewhat understand how this happens, as the correct procedure for correcting this is to REDUCE power, and NOSE DOWN, which is exactly opposite what the other side of your brain is telling you, which is go up, go up, go up, go up.) Given the choice of going in nearly inverted and nose down; or gliding into the trees in a controllable fashion, I would choose the latter.
I know we’re talking about “which is safer” but you also have to consider the fuel efficiency, performance, and maintenance of a single engine also.


#19

Pete the Pilot was trading flying stories with Aaron the Arrogant, when Aaron started in on a particularly juicy tale: “Well, I got that story beat. There I was, rolling down the runway for takeoff in my Piper Twin Comanche. Suddenly, as I was approaching takeoff speed, a cow just ambled onto the runway right in front of me! I pulled back hard on the controls and got into the air, and I swear I don’t know how I didn’t graze that cow’s back! He he, ‘graze,’ no pun intended”, Aaron deadpanned, elbowing Pete jokingly. Sensing he was losing his audience, though, Aaron quickly continued, “But that’s not all! To top it off, not 5 seconds after takeoff, my left engine quit on me!” To this, Pete raised an eyebrow in interest. Aaron gestured self-assuredly as he went on, “Thankfully, I was able to use my skill and lightning reflexes to save the situation. I immediately went to full power on my right engine and pulled the nose up to keep the plane in the air and all I had to do was make a quick turn to land on the perpendicular runway to my left”, Aaron finished with great gusto. Pete, with an amused look on his face, said, “Well, that’s a great story, Aaron, but because you are sitting here telling it, I know it didn’t actually happen.” How does Pete know?

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