Twin engine or Single engine? (Dumb question)

FloridaPilot

FloridaPilot

Pattern Altitude
Joined
Mar 10, 2014
Messages
2,456
Location
Florida
Display Name
Display name:
FloridaStudentPilot
Hello,

I was comparing singles to twin engine airplanes and I didn't notice a drastic difference in speed and performance. Do pilots prefer twins because they feel it's more safe? (Because most likely both engines won't go out at the same time) or is it because twins have slightly more power then singles?


As always thanks for your input!
 
FloridaPilot said:
Hello,

I was comparing singles to twin engine airplanes and I didn't notice a drastic difference in speed and performance. Do pilots prefer twins because they feel it's more safe? (Because most likely both engines won't go out at the same time) or is it because twins have slightly more power then singles?


As always thanks for your input!
Click to expand...

Not many singles out there cruise at 180kts.
 
Out here in the west, there are not a lot of places to dead stick an airplane in the day time, never mind at night. I picked a twin with two little engines instead of a single with one big engine for that reason. The result is that I don't go faster than a high performance single, but my fuel burn is about the same too.
 
Slightly more power than singles? I'd say it is more common for them to have roughly double the power of a comparable single.

Redundancy, power, increased load carrying capability, and higher cruising speeds are what I like about them. I'd take the fuel bill of a typical single over a typical twin anytime however.
 
FloridaPilot said:
Hello,

I was comparing singles to twin engine airplanes and I didn't notice a drastic difference in speed and performance. Do pilots prefer twins because they feel it's more safe? (Because most likely both engines won't go out at the same time) or is it because twins have slightly more power then singles?


As always thanks for your input!
Click to expand...

Pilots prefer twins. Get it? (Sorry--had to do that!)

Seriously, I think pilots like twins for redundancy, and a bit of a speed increase. I like flying twins because I love the sound of two throaty gas-guzzlers either side of me!
 
spiderweb said:
Seriously, I think pilots like twins for redundancy, and a bit of a speed increase. I like flying twins because I love the sound of two throaty gas-guzzlers either side of me!
Click to expand...

This pretty much.

A twin gives you redundancy both in engines and other systems like vacuum, hydraulic...etc. I will fly IFR in a single, but much prefer the twin for serious IFR. Twins typically are a little faster and have more payload, but not that much considering the penalty of the additional weight of the second engine and it's systems. On other words, they can do a little more, but not necessarily as efficiently as a single.

Also a lot if people like to fly twins because in addition to the above, many aspire to fly professionally and ME time is highly valued.
 
When you compare twins to a comparable single, the primary advantage is redundancy and safety (if you know what you're doing). The reality, though, is that once you get past entry-level twins, there are no comparable singles. An A36 Bonanza vs. 58 Baron will find the Baron faster. There is no piston single comparable to an Aztec (a Saratoga/Lance is no faster on the same fuel and smaller cabin with more expensive engine). Then get into the Navajo/Twin Cessna range and the Malibu would be the only "almost close" option, but has low payload and size is smaller than a 340.

Even the 310 doesn't have a comparable single. An A36 is smaller and slower. A Saratoga/Lance is smaller and way slower.
 
Well part of the reason is more drag associated with two engines and generally they're bigger than their SE counterparts. My Glasair cruises at the same speed as a Twin Comanche on the same IO-320. Difference is they redundancy and have room to move about, where as I'm crammed in like a Sardine. Always going to be sacrifices when it comes to performance.
 
Velocity173 said:
Well part of the reason is more drag associated with two engines and generally they're bigger than their SE counterparts. My Glasair cruises at the same speed as a Twin Comanche on the same IO-320. Difference is they redundancy and have room to move about, where as I'm crammed in like a Sardine. Always going to be sacrifices when it comes to performance.
Click to expand...

But those aren't equivalent planes otherwise. Compare a Comanche 250/260 to a Twin Comanche and you'll see a bit more speed for a bit more fuel. Simply saying single vs twin doesn't tell the whole story.
 
Known ice, 12in radar, nose baggage compartment, redundancy and performance.
 
FloridaPilot said:
Hello,

I was comparing singles to twin engine airplanes and I didn't notice a drastic difference in speed and performance. Do pilots prefer twins because they feel it's more safe? (Because most likely both engines won't go out at the same time) or is it because twins have slightly more power then singles?


As always thanks for your input!
Click to expand...

Twins make more noise.
 
Some pilots like twins because they enjoy a good cry once a year at the annual. :)
 
Last edited:
Ted DuPuis said:
But those aren't equivalent planes otherwise. Compare a Comanche 250/260 to a Twin Comanche and you'll see a bit more speed for a bit more fuel. Simply saying single vs twin doesn't tell the whole story.
Click to expand...

occasionally I fly a pa24-260 and a plain pa30-160. One travels at 160kts on 15.4gph, the other 160kts at 16gph. No real difference.
 
Most twins have considerably more installed horsepower than the equivalent single (even the relatively modest PA30 has a 60hp advantage over the PA24-260), but obviously drag and complexity is added. In addition, feeding the extra engine eats into the useful load; even though most twins have more useful load than an equivalent single, a 200 or 300 pound advantage can get eaten up by an increased fuel burn. In general, there will be a slight performance benefit to the twin, but not enough for most people to justify the added costs.

That said, twins offer redundancy; and, as others have mentioned, not just in terms of an extra engine. A second vacuum pump or alternator could be just as important as a second engine in night IFR. The value of that differs from person to person, and for many, is worth the extra cost.

Plus, twins are fun and cool... and when buying a plane that counts for something too, even if we don't want to admit it!

weilke said:
occasionally I fly a pa24-260 and a plain pa30-160. One travels at 160kts on 15.4gph, the other 160kts at 16gph. No real difference.
Click to expand...

My experience in a PA24-260 puts us around 155 knots on 12 to 13 GPH... that last 5 knots is costing you a lot of money!
 
TUPilot said:
My experience in a PA24-260 puts us around 155 knots on 12 to 13 GPH... that last 5 knots is costing you a lot of money!
Click to expand...

This was for the purpose of an apples-apples comparison. Sure, you can pull back and get a better nm/gal, same thing you can do with a twin.
 
The missions tend to be different, most twins have a higher payload and of course need to haul and burn more fuel, so it doesn't always equate to a much higher payload over a given distance. :D
Personally, I like twins for the larger cabin and speed. With a family of five, plus a dog and a daughter's boyfriend, I tend to either fly alone or with 4+ folks. No one in my family is considered petite, or even close. :rofl: So the extra room and payload is valuable to us. The single vs twin safety argument will never be solved here, so I won't get into it, people have to do what they are comfortable with doing. :D
I like two engines when I am in IFR, icing or even at night, but I do fly night VFR in a 182 and would fly IFR at night in it, but my minimums are a little higher than a twin. ;)
 
Anytime I see a twin vs single thread, I'm tempted to post "And we're off!" but this one didn't turned into as much of a religious war on safety as I thought it would :)
 
Depends also on pilots abilitys in clutch city. I know of two instances over the years, where a pretty competent pilot in a twin lost it due to an engine out in bad weather. He shut down the good engine on a go round by mistake, killing himself wife and children. The other apparently just could not keep up with things happening on final , one engine out , stalled, died. The CFI, a good friend said in practice, they responded well every time and stated they had pretty high time with no previous problems....until they did. Then just recently, the doctor in the MU2 among others.
 
If you try to do a single engine go-around for real, you're not doing yourself any favors.

0/0 and OEI with no better landing options? Yeah, I'll land anyway.
 
I would not do a OEI go around in anything that was not turbine powered.
 
Jhernandez04 said:
It's a safety factor. Redundancy can save lives.
Click to expand...

If I fly a twin and one of the engines go out, (Say the right engine) can the left keep the entire plane in the air? I would probably be forced to land? Wouldn't it be the same situation with a single?
 
Kristin said:
Out here in the west, there are not a lot of places to dead stick an airplane in the day time, never mind at night. I picked a twin with two little engines instead of a single with one big engine for that reason. The result is that I don't go faster than a high performance single, but my fuel burn is about the same too.
Click to expand...


That is a good reason, especially if you get the same fuel burn. So if you were to get something like a Cirrus with the CAPS system wouldn't it be somewhat similar?
 
spiderweb said:
Pilots prefer twins. Get it? (Sorry--had to do that!)

Seriously, I think pilots like twins for redundancy, and a bit of a speed increase. I like flying twins because I love the sound of two throaty gas-guzzlers either side of me!
Click to expand...

It took me awhile but I got it. :lol::yesnod:
 
FloridaPilot said:
If I fly a twin and one of the engines go out, (Say the right engine) can the left keep the entire plane in the air? I would probably be forced to land? Wouldn't it be the same situation with a single?
Click to expand...

Depends on a lot of things. Weight, airplane (horsepower), temperature, height of terrain...etc.

Most of the trainer twins will struggle to maintain anything more than 2-3000' at max gross. Bigger twins can go a little higher. All twins will have a single engine service ceiling that may or may not keep you above the terrain. You have to know your airplane and the conditions you are flying in.
 
dans2992 said:
I would not do a OEI go around in anything that was not turbine powered.
Click to expand...

All depends on how much load vs excess HP one carries. At the end of a flight with me, my luggage, and 45 minutes of fuel, I'd SE go around, no worries.

One thing people mention in the lis is load and redundancy. With accessories redundancy is true, with power for lift though, redundancy is an inverse function of load. Cut yourself a 10% margin off gross, and you now have some reasonable expectations of some OEI performance, if you can cut 20% off your load, you're doing well. If you fly like I do normally and take off fuel fuel at mid weight leaving 750lbs available, then with 260hp a side, I have reasonable expectations of climbing out well on one below 5000', and maintaining climb to over 7500'.

I fly a 310 because the way I operate, I get a lot of reserve everything, and I love having reserves. For all those reserves, I pay a fuel penalty that gets me 9.5 nmpg. I also rarely run my engines above 55% power, and I run them hard LOP with low CHTs and white dust as the only residue in my exhaust.

I realize this is anecdotal, but my last twin I did three precautionary shut downs due to loss of oil in flight, landed each safely in major metropolitan areas of California on a runway, and repaired it each time for less than $200 and a couple hours of lost time changing a hose. Had I been flying a single, twice I know I would likely not have made a runway before lunching an engine, the other time I likely wouldnt have survived; engines are $30k, not having to spend that 3 times was nice, as was making the runway with one caged, especially shooting an ILs into OAK to 90'.

Twins buy options, a couple of those options are deadly, but you can choose not to exercise those options. Options always cost money, but what costs more money is speed; specifically the last 10% of available speed. The cost of operations increases parabolicly from L/D max to top speed, the more you are willing to cut your speed, your decrease in cost is inversly exponential.
 
Having lots of fuel is a safety item. Electrical or comm failure in IMC? Fly to VFR and land (if you have the range), fly AROUND the bad weather etc. If you reduce fuel load to increase single engine performance, you are making a tradeoff of one to the other.

Twice as many engines means twice the likelihood of an engine failure. Twice as likely to survive an engine failure? If so, its even steven. Has to be MORE than twice as likely.
 
Fearless Tower said:
Depends on a lot of things. Weight, airplane (horsepower), temperature, height of terrain...etc.

Most of the trainer twins will struggle to maintain anything more than 2-3000' at max gross. Bigger twins can go a little higher. All twins will have a single engine service ceiling that may or may not keep you above the terrain. You have to know your airplane and the conditions you are flying in.
Click to expand...

I remember a charter I flew in a Seminole because the client insisted on two engines. Not only was it more crowded with three pax but I was struggling to stay on top at 12,000 feet over the Cascades. Cherokee Six would have been more comfortable and more capable.

Bob Gardner
 
coloradobluesky said:
Having lots of fuel is a safety item. Electrical or comm failure in IMC? Fly to VFR and land (if you have the range), fly AROUND the bad weather etc. If you reduce fuel load to increase single engine performance, you are making a tradeoff of one to the other.

Twice as many engines means twice the likelihood of an engine failure. Twice as likely to survive an engine failure? If so, its even steven. Has to be MORE than twice as likely.
Click to expand...

I usually take off with over 930nm worth of fuel, and still have 750 lbs left. If I am flying less than 200 miles though, taking all that fuel is no safety factor at all. Being able to get under the weather is typically a more realistic option than flying around it, when I'm flying cross country at 100', I'm much more comfortable in my 310 than I was in a PA-12. Most major systems that would really impact your fuel load are ones you can't really get around, you either wait, go under, or punch through.

Besides all of which, carrying extra fuel over the CONUS isn't much of a safety margin issue, this country is littered with fuel stops if you have to divert. You can talk yourself into believing whatever, it doesn't matter, chances are definitive that you will die whether you fly a twin, a single, a whoppyflopter or sit on the ground and never look up.
 
FloridaPilot said:
I thought Mooney's do that?
Click to expand...

A number of complex singles do that. Bonanzas, long-body Mooneys, 210, SR22, Malibu and others. Most of them have 300+hp engines, some with turbochargers. The all-in cost to operate one of those fast singles is not that much less than the cost to operate a basic twin like a B55 Baron or Cessna 310.

For example, a comparison between the A36TC for a single and the B55 as a twin. The A36 has a longer cabin, but both will be good aircraft to transport 4 with some luggage:

The price on a 'factory rebuilt' (reman) TSIO520-UB as used on the turbo Bo is $53,720, the cost for two IO470L engines as used on the B55 is $68,000. So your engine reserve for the B55 is going to be $37/hr, on the TC it is $30/hr. Same with fuel burn, to go lets say 180kts, you may burn 17.5gph in the TC and 23gph in the B55. Your hourly variable maintenance on the twin has to deal with 24 additional spark-plugs, 2 extra magnetors, 1 extra starter-clutch, an extra alternator and some hardware that you wont find on a single (e.g. a gas powered furnace to heat the thing). The rest of the airframe is very similar.

So between a 'bare bones' B55 and a A36, the additional expenses are not twice but maybe 25% more. At current prices, you can find a B55 with similar engine times and equipment for 50-80k less than an A36. If you either have to borrow the money to buy or account for it somehow otherwise, that difference in entry price may affect your total cost to own.

In both aircraft types, you can get systems like weather radar and deicing equipment to extend your capabilities for summer and winter flying. Both times, those systems are quite common on twins and less common on singles. They also tend to be a lot more expensive to add to a single and dont work quite as well. While you can have an A36 with a radar pod and TKS deicing, it will cut into your useful load, speed and add considerably to purchase price. A E55 or B58 Baron otoh can be had with known icing equipment and weather radar in the nose. Again, additional systems come with additional maintenance bills.
 
Last edited:
Twin-engine aircraft have two engines because they can't fly on one.
 
weilke said:
A number of complex singles do that. Bonanzas, long-body Mooneys, 210, SR22, Malibu and others. Most of them have 300+hp engines, some with turbochargers. The all-in cost to operate one of those fast singles is not that much less than the cost to operate a basic twin like a B55 Baron or Cessna 310.

For example, a comparison between the A36TC for a single and the B55 as a twin. The A36 has a longer cabin, but both will be good aircraft to transport 4 with some luggage:

The price on a 'factory rebuilt' (reman) TSIO520-UB as used on the turbo Bo is $53,720, the cost for two IO470L engines as used on the B55 is $68,000. So your engine reserve for the B55 is going to be $37/hr, on the TC it is $30/hr. Same with fuel burn, to go lets say 180kts, you may burn 17.5gph in the TC and 23gph in the B55. Your hourly variable maintenance on the twin has to deal with 24 additional spark-plugs, 2 extra magnetors, 1 extra starter-clutch, an extra alternator and some hardware that you wont find on a single (e.g. a gas powered furnace to heat the thing). The rest of the airframe is very similar.

So between a 'bare bones' B55 and a A36, the additional expenses are not twice but maybe 25% more. At current prices, you can find a B55 with similar engine times and equipment for 50-80k less than an A36. If you either have to borrow the money to buy or account for it somehow otherwise, that difference in entry price may affect your total cost to own.

In both aircraft types, you can get systems like weather radar and deicing equipment to extend your capabilities for summer and winter flying. Both times, those systems are quite common on twins and less common on singles. They also tend to be a lot more expensive to add to a single and dont work quite as well. While you can have an A36 with a radar pod and TKS deicing, it will cut into your useful load, speed and add considerably to purchase price. A E55 or B58 Baron otoh can be had with known icing equipment and weather radar in the nose. Again, additional systems come with additional maintenance bills.
Click to expand...

I'm a newbie, but the overall added expenses of owning a twin doesn't seem worth it to me. If it was a significant difference then I believe I would see different. Don't get me wrong, twins are beautiful but with that added expense I could fly more in a single to me it's all about getting in the air.

What started the question was an article I read at the AOPA website:

http://www.aopa.org/News-and-Video/All-News/2013/June/1/Dogfight-Twin-versus-single.aspx

The article said: "History shows piston twins are no safer than afflicted singles. In fact, engine failures that result in accidents are more likely to be fatal in twins."
 
Twins do have their advantages, but as fuel costs rise, so does the cost delta...

Look how many piston twins are in production today. Not many, and of those that are, they're not hot sellers.

If money was absolutely no concern, sure I might fly a twin (421 would be nice), but like most of us, I don't live in such a world.

Plus, if money really was no concern, I'd be going turbine anyhow...
 
Last edited:
Before Charles Lindbergh crossing of the Atlantic on a single two attempts were made on twins by other pilots, they were never found. Amelia Earthart crossed the Atlantic on a single but was lost on a twin.

On typical piston twin you have 12 cylinders. On a typical single you have four cylinders. Assuming a cylinder failure at 2000hrs for a 4 cylinder that will put the twin at a cylinder failure at every 700hrs.

Airlines prefer twins vs four engines or three engines because of the economy and dispatchability. FEDEX opted for the Caravan single vs a twin for the same reasons.

On take off at max power the probability of an engine failure is twice on a twin than on a single.

On a crash the single engine the engine provides a shield that is not on the twins.

To me there is no added advantage on piston twins but more maintenance and fuel costs.

There are singles like the Mooney Acclaim or the SR-22 that fly faster and cheaper than most piston twins.

José
 
Last edited:
Piloto said:
Airlines prefer twins vs four engines or three engines because of the economy and dispatchability. FEDEX opted for the Caravan single vs a twin for the same reasons.

On take off at max power the probability of an engine failure is twice on a twin than on a single.

On a crash the single engine the engine provides a shield that is not on the twins.

José
Click to expand...

Caravan is a turbine, hardly comparable.

Engine failure in a single on takeoff means 100% probability for a forced landing. On a twin, not so. Not a valid argument.

Single engine provides a shield? No it doesn't. It just means your firewall is pushed against your face with more force.
 
Overwater solo? I'd probably still do it in a single. With the family on board? Hell no. Twin or nothing.
For that mission set, I see the value of a twin. For everything else over land? Not at $6/gal and engines at 30K+ a pop, I don't.
 
You must log in or register to reply here.
Back
Top