That second engine...

[hindsight2020]

So I knocked out got my ATP-MEL last weekend (now I truly have a license to quit the military LOL) and with a total of 4 flights in the twin version of my personal airplane, to include engine shutdowns and OEI work, it was quite an interesting experience to say the least. Even down here in lowland Texas, at 90F+, these things are truly not twins, was the impression I walked away from. To be fair, I was able to hold blue line + 10 at around 5k, and do so configured around pattern altitude with simulated feather condition, but that was @ 500 undergross LOL. I did some spaghetti chart chasing with my typical family mission of 2+1 in the Arrow, and for the same cruise power setting endurance I'd be looking at sub 200fpm climb rates OEI down here in the summer. Not exactly the performance I'd like to have on initial climbout below 1k AGl when one decides to crap out.

All that said, I can certainly see owning one of these 4-banger "dual singles" if my mission involved living in South Florida and bopping around the Caribbean. This video kinda drove it home for me

Gotta give it to the guy, not even enough life vests for all onboard. There's no way I'd live in the Keys and not own a 2 man raft and SOSpenders for all occupants. Better lucky than good I guess.

 

[OkieFlyer]

I have heard folks talk about the lack of single engine performance of many twin engine planes here on POA. It seems the most commonly used word is "anemic." This boggles my mind a bit. It seems like people expect the plane to maintain a really good climb rate on one engine. Why? And, why is 200-300 fpm considered "anemic" when an engine poops in the bed? If you lose an engine in a single, it's going back toward earth, period. I would think that if that second engine gets you anything besides a one-way ticket back to mother earth, then it's a win. To still be able to achieve a positive rate of climb on one engine sounds like heck of a deal. I went flying with a friend a couple weeks ago in a PA-28 140 in similarly hot conditions, fuel up to the tabs, 2 up, and our initial climb was only around 300 fpm until we got over the plowed fields and got some help from thermals. If you are driving a plane that will still go anywhere in the upward direction, however slowly, when an engine takes a dump, that is one heck of a margin of safety IMO.

I'm not picking on you, hindsight2020, but I've long been bumfuzzled by people's expectations of single engine performance in twins. A twin should perform nicely with both screws turning, and do well enough on one engine that you can set it down at the nearest runway instead of the nearest flat spot on the ground. Pardon the rant. Just my opinion, and not just about this particular thread.

 

[luvflyin]

Makes night flying less worrisome also. And over mountainous terrain. Even if they can't hold altitude it can give a lot more time and distance to come up with a plan. As far as the low, slow and heavy issues go, you're in no worse shape pulling the good engine if you have to, to keep from rolling over, than you would have been if the engine that quit was the only one.

 

[mondtster]

I'm not picking on you, hindsight2020, but I've long been bumfuzzled by people's expectations of single engine performance in twins. A twin should perform nicely with both screws turning, and do well enough on one engine that you can set it down at the nearest runway instead of the nearest flat spot on the ground. Pardon the rant. Just my opinion, and not just about this particular thread.

This is the exact mentality that gets the people in trouble that you're picking on. Not all twins will maintain altitude, much less do well enough that make it to an airport to land. And, if you keep pulling up on it to try and keep the airplane in the air things will get real ugly.

 

[Fearless Tower]

This is the exact mentality that gets the people in trouble that you're picking on. Not all twins will maintain altitude, much less do well enough that make it to land. And, if you keep pulling up on it to try and keep the airplane in the air things will get real ugly.

And why some people survive in twins and some don't. It's about training and mindset.

The advantage of twins is more than a second powerplant. With a twin, you have more redundancy in other systems as well. Two vacuum pumps. Two alternator/generators, in some cases dual hydraulic sources. I've experienced vacuum and alternator failures in twins and they were complete non-events. The problem that a lot of folks have is that the redundancy comes at a high price in fuel, maintenance and training. If you can wrap your head around that, a twin is a good option.

 

[Twin_Flyer]

And why some people survive in twins and some don't. It's about training and mindset.

The advantage of twins is more than a second powerplant. With a twin, you have more redundancy in other systems as well. Two vacuum pumps. Two alternator/generators, in some cases dual hydraulic sources... The problem that a lot of folks have is that the redundancy comes at a high price in fuel, maintenance and training. If you can wrap your head around that, a twin is a good option.

I feel a lot better at night and over lumpy ground...

 

[mondtster]

And why some people survive in twins and some don't. It's about training and mindset.

The advantage of twins is more than a second powerplant. With a twin, you have more redundancy in other systems as well. Two vacuum pumps. Two alternator/generators, in some cases dual hydraulic sources. I've experienced vacuum and alternator failures in twins and they were complete non-events. The problem that a lot of folks have is that the redundancy comes at a high price in fuel, maintenance and training. If you can wrap your head around that, a twin is a good option.

Agreed on the training part, although I personally think that the guys who would have trouble with flying OEI in a twin would also have a bit of trouble in an emergency situation in a single.

The redundancy of systems is what I like about the twins, plus having the extra power (when everything is working right) is nice. It comes at a price though (fuel and maintenance costs), but I really personally don't get enthused about flying a lesser airplane in bad weather in anything less.

 

[Fearless Tower]

Agreed on the training part, although I personally think that the guys who would have trouble with flying OEI in a twin would also have a bit of trouble in an emergency situation in a single.

I agree completely. I've said this before, but I think it is worth repeating. There is a huge emphasis in training on VMC, but what really kills people in twins is stalling with asymmetric thrust.

 

[mscard88]

Just think of it as losing 80% of your performance, not 50% like many think. FAA doesn't require any minimum rate of climb in a light twin. When I took my ME CFI w/ the FAA Inspector in an older C310 he took the controls and said go ahead, fail one (simulated of course). I did and he couldn't hold altitude and said this thing's a pig!

 

[hindsight2020]

If you are driving a plane that will still go anywhere in the upward direction, however slowly, when an engine takes a dump, that is one heck of a margin of safety IMO.

I'm not picking on you, hindsight2020, but I've long been bumfuzzled by people's expectations of single engine performance in twins. A twin should perform nicely with both screws turning, and do well enough on one engine that you can set it down at the nearest runway instead of the nearest flat spot on the ground. Pardon the rant. Just my opinion, and not just about this particular thread.

Oh no sweat, I engage these threads for the purpose of exchanging ideas. I can tell you that to me, the difference between a lackluster climb rate in a single and one in a twin, has to to with the dynamics of touchdown. I much prefer to impact the ground in a much lighter, slower single with half the gas on board, than a twin holding blue line, with a much higher sink rate when I pull the second throttle. What kills people is the siren song of thinking, yeah I can pull out of this one at sub 200fpm.

To normalize the discussion, I'll give you my perspective as a pro. The FAA sets IFR OEI departure climb gradient circa 200ft/NM, or standard, otherwise higher if stated as such. Do the math: you ain't making that on most these 4-bangers. The FAA specifically exempts their design certification by carving out the OEI climb criteria from the sub 6k sub 61kt VSO airplanes, in order to account for this deficiency. To me, that's all I need to hear. They're not twins to me and it would be hazardous to treat them as such on departure. That's a lot of tight circling you're gonna have to do to keep that sucker clear of low close-in obstacles, with asymmetric thrust ready to pounce on any control input hiccup on your part, never mind the distinct possibility you won't be able to climb at all with any turn of consequence. Coffin corner.

Thus, even thinking of these airplanes as a "twins", is imo terrible negative transfer, unless the only twins you've ever flown are part 23 sub 6k sub 61kt twins. It certainly was for me when I first started the engines on the seminole, then did one OEI demonstration and convinced myself to never ever describe them as such, as a professional turbine multi pilot.

I can tell you with confidence, if I handled go/no-go criteria on the B-52 as I have to in a seminole, people would die. Likewise, treating a seminole with the go/no-go criteria of a Buff, would leave me hitting the parking lot at blue line with double the fuel to ignite as that of my Arrow.

So I disagree with your position; the lackluster and negative-transfer-prone nature of light piston twins is not overstated imo. They are to be treated as singles for takeoff. You're not climbing to pattern altitude with any sense of safety margin, so you're better off running it off the runway at taxi speed and cashing the insurance check. To me, you need to be established well above 500' AGL and past the close-in obstacles before you can reap the benefit of powerplant redundancy on these spam cans. And don't misunderstand, just as I suggested by the original post, there is a mission set for which that redundancy is valuable. Takeoff is not it, and it's not a "just a couple" seconds like some people suggest. It takes actual minutes before you're in that regime imo. Of course, you can ameliorate these limitations by lowering the weight you're willing to depart with. But that becomes an economic argument, which is a different issue altogether.

 

[Velocity173]

I have heard folks talk about the lack of single engine performance of many twin engine planes here on POA. It seems the most commonly used word is "anemic." This boggles my mind a bit. It seems like people expect the plane to maintain a really good climb rate on one engine. Why? And, why is 200-300 fpm considered "anemic" when an engine poops in the bed? If you lose an engine in a single, it's going back toward earth, period. I would think that if that second engine gets you anything besides a one-way ticket back to mother earth, then it's a win. To still be able to achieve a positive rate of climb on one engine sounds like heck of a deal. I went flying with a friend a couple weeks ago in a PA-28 140 in similarly hot conditions, fuel up to the tabs, 2 up, and our initial climb was only around 300 fpm until we got over the plowed fields and got some help from thermals. If you are driving a plane that will still go anywhere in the upward direction, however slowly, when an engine takes a dump, that is one heck of a margin of safety IMO.

I'm not picking on you, hindsight2020, but I've long been bumfuzzled by people's expectations of single engine performance in twins. A twin should perform nicely with both screws turning, and do well enough on one engine that you can set it down at the nearest runway instead of the nearest flat spot on the ground. Pardon the rant. Just my opinion, and not just about this particular thread.

It's because they're used to flying high performance stuff where an engine failure is a non event on take off. Friend of mine just got checked out in the UC-35 and said engine failure on take off is nothing. Still climbs a few thousand per min. If he were to go back to light twins, he'd probably say the climb rate was anemic.

 

[OkieFlyer]

Oh no sweat, I engage these threads for the purpose of exchanging ideas. I can tell you that to me, the difference between a lackluster climb rate in a single and one in a twin, has to to with the dynamics of touchdown. I much prefer to impact the ground in a much lighter, slower single with half the gas on board, than a twin holding blue line, with a much higher sink rate when I pull the second throttle. What kills people is the siren song of thinking, yeah I can pull out of this one at sub 200fpm.

To normalize the discussion, I'll give you my perspective as a pro. The FAA sets IFR OEI departure climb gradient circa 200ft/NM, or standard, otherwise higher if stated as such. Do the math: you ain't making that on most these 4-bangers. The FAA specifically exempts their design certification by carving out the OEI climb criteria from the sub 6k sub 61kt VSO airplanes, in order to account for this deficiency. To me, that's all I need to hear. They're not twins to me and it would be hazardous to treat them as such on departure. That's a lot of tight circling you're gonna have to do to keep that sucker clear of low close-in obstacles, with asymmetric thrust ready to pounce on any control input hiccup on your part, never mind the distinct possibility you won't be able to climb at all with any turn of consequence. Coffin corner.

Thus, even thinking of these airplanes as a "twins", is imo terrible negative transfer, unless the only twins you've ever flown are part 23 sub 6k sub 61kt twins. It certainly was for me when I first started the engines on the seminole, then did one OEI demonstration and convinced myself to never ever describe them as such, as a professional turbine multi pilot.

I can tell you with confidence, if I handled go/no-go criteria on the B-52 as I have to in a seminole, people would die. Likewise, treating a seminole with the go/no-go criteria of a Buff, would leave me hitting the parking lot at blue line with double the fuel to ignite as that of my Arrow.

So I disagree with your position; the lackluster and negative-transfer-prone nature of light piston twins is not overstated imo. They are to be treated as singles for takeoff. You're not climbing to pattern altitude with any sense of safety margin, so you're better off running it off the runway at taxi speed and cashing the insurance check. To me, you need to be established well above 500' AGL and past the close-in obstacles before you can reap the benefit of powerplant redundancy on these spam cans. And don't misunderstand, just as I suggested by the original post, there is a mission set for which that redundancy is valuable. Takeoff is not it, and it's not a "just a couple" seconds like some people suggest. It takes actual minutes before you're in that regime imo. Of course, you can ameliorate these limitations by lowering the weight you're willing to depart with. But that becomes an economic argument, which is a different issue altogether.

I mostly understand what you're saying. I'll tell you this, an old Apache 150 on one noisemaker will out climb my C-182 with one engine out any day of the week. I find the engine out performance on the venerable Skylane to be quite anemic, despite being a high performance bird

 

[mscard88]

I find the engine out performance on the venerable Skylane to be quite anemic, despite being a high performance bird

I've heard that about the Skylane. Wonder why....

 

[SkyDog58]

 

[edo2000]

... Of course, you can ameliorate these limitations by lowering the weight you're willing to depart with. But that becomes an economic argument, which is a different issue altogether.

It's not as much an economic argument, if you are using the twin for transportation for a couple of people and no freight. I agree that at gross weight, medium high density altitude, engine failure at very low altitude might very well end with an off-airport landing. However, as a past owner of a C310, I seldom was near gross weight and, operating in Alaska, I was often in low density altitude conditions. Thus, in most cases, I was flying a machine with redundancy that was available from VMC on.

I do hear what you are saying, though. And, of course, another downside of a twin is that engine failure probability is 2X that of a single.

 

[hindsight2020]

It's not as much an economic argument, if you are using the twin for transportation for a couple of people and no freight. I agree that at gross weight, medium high density altitude, engine failure at very low altitude might very well end with an off-airport landing. However, as a past owner of a C310, I seldom was near gross weight and, operating in Alaska, I was often in low density altitude conditions. Thus, in most cases, I was flying a machine with redundancy that was available from VMC on.

I do hear what you are saying, though. And, of course, another downside of a twin is that engine failure probability is 2X that of a single.

Good points all around. For the scenario presented by the safety video, I'm more than comfortable with the opportunity cost of potential for engine loss on initial climbout. I consider an off-runway crash straight ahead in a twin a preferable outcome than a ditching with family on board, especially if I make the decision to abort early and just skid off the end of the pavement. Obviously for anything requiring IFR-quality climbs above 3k msl, turbo equipment is really a necessity OEI.

It's interesting how our predilections work. Most people look at flatland IMC or night in a single and think it's a game of Russian roulette. Though night generally only presents itself on my mission when flying solo (where pretty much anything goes), I do either on occasion with family and don't think much of it. Yet I see people crossing the bahamas on a lance loaded with family and bags to the gills, no raft on board. My eyes pop out my sockets, yet these folks clearly think nothing of it. I suppose I attribute that bias to my survival training in the military. It left me with the distinct impression I much rather handle a post crash survival scenario with family on land, than water. I suppose if I did or valued mountainous crossings as part of my flying, I would also consider the piston twin a worthy alternative.

 

[Twin_Flyer]

And, of course, another downside of a twin is that engine failure probability is 2X that of a single.

Now you've done it...

 

[coloradobluesky]

Mathmatically it is P(1) + P(2) - P(1) * P(2)
where
P(1) is the probability of engine 1 failing
P(2) is the probability of engine 2 failing
The P(1) * P(2) is the probability of both engines failing, which is very small because both P(1) and P(2) are very small numbers below 1 and when you multiply them it gets even smaller. So small you can ignore the P1*P2.

From a practical standpoint the probability of an engine failure in a twin is very close to twice that of a single. So close you can just say it IS twice (since the P(1) and P(2) arent really accurately known anyway).

 

[denverpilot]

Around here, climbing in a light twin in summer isn't an option on a single engine. Maybe 100 ft/min if you're lucky in the turbo ones. Not going up at all in a non-turbo.

 

[MauleSkinner]

To normalize the discussion, I'll give you my perspective as a pro. The FAA sets IFR OEI departure climb gradient circa 200ft/NM, or standard, otherwise higher if stated as such. Do the math: you ain't making that on most these 4-bangers. The FAA specifically exempts their design certification by carving out the OEI climb criteria from the sub 6k sub 61kt VSO airplanes, in order to account for this deficiency. To me, that's all I need to hear. They're not twins to me and it would be hazardous to treat them as such on departure.

If you're assuming that all Part 25 airplane take offs meet 200 ft/mile, you might want to stay in the military.

I once showed my Chief Pilot & D.O. what the 96 ft/mile engine-out performance they were planning for the jet looked like...I was accused of trying to wipe out half the flight department,

I can tell you with confidence, if I handled go/no-go criteria on the B-52 as I have to in a seminole, people would die. Likewise, treating a seminole with the go/no-go criteria of a Buff, would leave me hitting the parking lot at blue line with double the fuel to ignite as that of my Arrow.

I can tell you with confidence that most multi engine pilots could tell you that with confidence as well. You have to fly the airplane you're in, not the one you wish you were in.

 

[James_Dean]

Just anecdotal, but when I lost one in the 310 I was glad to have had the other engine to get me safely to the ground next to a warm hangar. Of course I was above a layer with known icing and was going to a destination that was 600/3 so I probably wouldn't have been there in a single anyway. In other words - this whole debate to me is about the kind of flying to want to do. Casual flier? Get a single and know your limits. Want to get somewhere on a reasonable schedule in lots of conditions? Get a twin with all the goodies, fly it with margins to spare, fly it a bunch and get regular training.

 

[PPC1052]

The advantage of twins is more than a second powerplant. With a twin, you have more redundancy in other systems as well. Two vacuum pumps. Two alternator/generators, in some cases dual hydraulic sources. I've experienced vacuum and alternator failures in twins and they were complete non-events. The problem that a lot of folks have is that the redundancy comes at a high price in fuel, maintenance and training. If you can wrap your head around that, a twin is a good option.

No doubt that's a benefit. But it would seem that you could get those without a second engine without the capital, maintenance, and fuel expenses of a second engine. Sorry for the non sequitur.

 

[Fearless Tower]

No doubt that's a benefit. But it would seem that you could get those without a second engine without the capital, maintenance, and fuel expenses of a second engine. Sorry for the non sequitur.

There is truth in that. These days, there are indeed many options available to add the redundancy to singles. I have no problems with someone who chooses that route. Although I have noticed that there are single pilots who use that argument to bad mouth twins and yet they won't actually spend the money to install the tech in their own singles.