Can we put the myth that singles are as safe as twins to bed now?

[AdamFrisch]

From another forum: 93% of non commercial accidents are in singles, 7% are in twins. The FAA says that singles are flown 12.16 million hours per year and twins are flown 1.82 million hours per year in the US. That means that singles have twice as many accidents per flying hours as twins.

Wherever that figure that we've heard bandied around for the last decades comes from, I don't know (Dick Collins, I'm looking at you), but they're not true according to these documents:

http://www.aopa.org/-/media/Files/AOPA/Home/Pilot%20Resources/Safety%20&%20Proficiency/Accident%20Analysis/Nall%20Report/ASI%20GA%20Scorecard%202011_2012.pdf

General Aviation and Part 135 Activity Surveys - CY 2010 (http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/CY2010/)

[abgd]

According to your first link, page 6, 23/82 or 28% of twin accidents were fatal, but 141/883 (16%) single fixed-gear accidents were fatal. 66/229 or 28% of accidents in single-engine retractibles were fatal.

Your twins may or may not be half as likely to be in an accident, but if you do then you're about twice as likely to be killed in said accident. On the other hand, perhaps it's fairer to compare the single engine complex aircraft to the twins. But we don't have enough information to do that.

Then, you would expect your average twin pilot to be considerably better trained than your average sep pilot. So if you're about equally likely to be killed in a twin or a single, then it probably implies that twins are more dangerous.

So no... not settled.

[AdamFrisch]

The figures I kept hearing were always accidents, not fatalities. Which in this case is in favour of twins. It is reasonable to get a higher number of fatalities in a faster moving aircraft. But it's muddled, I'll give you that.

[Blues&twos]

As with most things in life, things are never simple.It depends what you're saying...are the aircraft themselves inherently less safe ( so with the same quality of pilot, weather, airport etc and training) the SEPs would have more accident, or that th SEP category is operated in a manner which attracts more incidents? This was one of abgd's points. There are so many external factors that itwould be impossible to categorically say one way or the other. Aaah, statistics, eh?

[piperboy84]

Adam I think looking at the type of equipment used for the accident numbers is misleading.

If you take a sampling of say 100 GA pilots, probably no more than 10% fly twins, I would guess that the vast majority of that 10% in addition to having MEP training will have Instrument and maybe even commercial or some other advanced certificate like ATP and some type of recurring training program even if they are non commercial flyers. Where as i suspect that the other 90% of GA pilots who fly singles stopped there official training path upon receipt of their PPL with just flight reviews as further "training".

If you looked at the the equipment (SEP/MEP) from purely a hardware reliability standpoint like you would any other machinery the mean time to failure providing both get similar maintenance is probably not that far apart.

Like most things in life, it's the the operator that is the weak link and usually due to training.

[yakhunter]

Also, how many of those single accidents were in aerobatic types. Clearly this kind of flying far more likely to end in an incident that your usual twin transit.
Unless the data can be broken down in further detail, then as usual, the stats are not accurate enough to be precise.

[charliegolf]

93% of non commercial accidents are in singles, 7% are in twins.

If 93% of non commercial flights were undertaken in singles, the stats are immediately less than useful. What's the proportion of flights undertaken by singles:twins?

CG

[Pace]

On the whole pilots who fly singles range from very experienced competant and current to complete idiots who should not be allowed to fly a kite and there are a whole mass in between.
While the same probably applies to MEP pilots the idiot section is probabaly a lot smaller.
We all Know the benefits of flying a twin over fog, at night, low cloud over water etc but its when the one engine fails that the twin pilot does not fare so well but for me that is a currency and training issue.
A twin has more power and in my book power is safety.
So yes I am sure with both engines running a twin is more capable and safer other than when you move to top of the range singles

Pace

[Blues&twos]

interesting, yakhunter. Along similar lines, are aerobatic aircraft more or less likely to crash? :)

[Tay Cough]

93% of non commercial accidents are in singles, 7% are in twins.

Meaningless without indicating the proportion of hours/flights flown be each.

[RTN11]

Also comes into this is the number of rotations.

Surely SEP aircraft fly largely 40-60 minute sorties, so have a high number of take offs and landings, which are clearly the most safety critical part of the flight.

Twins on the other hand will fly 2 hours or more as a typical flight, long times spent in the cruise, possibly even on autopilot, all skews the figures, so you can't directly compare the two as they are operated so differently.

It's impossible to reach a meaningful conclusion, even with all the stats.

[englishal]

I think the basic facts speak for themselves. You are more likely to have an accident in a single than a twin, however you want to bend the stats. Makes sense as well, you have redundant systems on a twin.

IF an engine fails in a twin and IF it is handled correctly, it could be no more than an inconvenience at worst. IN a single, you ARE going down. If you are lucky you will pull off a decent off airport landing with no damage, if you are exceedingly lucky you will land back on a runway and if you are unlucky you might die or destroy the aeroplane.

[obgraham]

IF an engine fails in a twin and IF it is handled correctly, it could be no more than an inconvenience at worst. But therin lies a problem. I've seen any number of reports of very experienced pilots not handling engine failure on takeoff correctly. With obviously disastrous results. Single engine failure on takeoff? -- land straight ahead. Walk away.

I agree -- the issue is complex and not easily answered.

[RatherBeFlying]

The airlines are really good when the statistic is fatalities per passenger mile -- helps to have a couple hundred bods behind and only do long flights;)

A metric that may be less biased is fatal accidents per flight, but that number in the GA fleet is a matter of extrapolation from hours flown -- hence unreliable.

We can look at accident reports to gain a sense of specific accident factors, especially those that kill people.

[DLT1939]

"We all Know the benefits of flying a twin over fog, at night, low cloud over water etc but its when the one engine fails that the twin pilot does not fare so well but for me that is a currency and training issue.
A twin has more power and in my book power is safety."


Yes, but how many twin pilots appreciate that when one engine fails they can lose as much as 90% of their excess power. Excess power being the power in excess of that needed to maintain straight and level flight. This is worth reading:


Accident Prevention Program (http://www.safeaero.net/accident_prevention_program.htm)

[cockney steve]

something else to consider.....the twin is a damned sight heavier than s single with similar pax. capacity...and to play devil's advocate....there are a fair number of singles with light structure, light wing-loading and slow flight characteristics....the twin is generally faster. yes, I'm aware the new light composites are very slippery and appear to have little redundant strength-margins, but they're not a significant percentage of the GA fleet, are they?

Are 3-axis Microlights included?

Figures are pretty meaningless unless there area lot more specific parameters attached to the results, however, it would be interesting to see these various sub-categories analysed by number of flights and total flight-hours, average flight -hours etc. I have a sneaking suspicion that Regulated Flexwings are the safest powered, other than Powered gliders....

[glendalegoon]

while I don't have the figures to back it up, I've seen twins get into trouble not so much on takeoff, but in descent.

You know right away if an engine quits on takeoff.

But in a descent, you might not notice (at a lower power setting) until you level off in the circuit/pattern for the downwind. I saw a video of a 421 augering in near chicago losing one on the descent.

Twins are nicer, but only if you are ready to fly with one shut down. I mean nicer in that they are usually better equipped.

[Pace]

I have about 800 hrs in single pistons and 3000 hrs in piston twins! i would never dream of flying some of the weather I have flown in the twins in a single! icing, at night, over long stretches of water, over fog banks, low cloud and strong winds and turbulence.
Ok a twin is a real aeroplane :ok: and a single a toy for nice days :E unless its a TBM 850 or Pilatus PC12 :ok:

Pace

[mad_jock]

it only turns into a real plane pace when it has a toilet fitted. And one that flushes at that :D

Or it can pull over 3g

PS only teasing I love flying cubs and the like. Well actually anything that's fly's and I can fit my arse into. It doesn't need to have an engine.

[Pace]

MJ

I was half teasing ;) I think it is hard to compare as a twin and single USUALLY have a different mission profile and the pilots USUALLY tend to be more experienced ! I stress the word usually as there can be very experienced capable pilots who fly singles in **** :suspect:
Most singles are not equipt for serious weather flying a case of different horses for different courses

Pace

[Romeo Tango]

It seems to me from the above that the twin/single safety question is marginal at best.

A single is much cheaper, simpler and greener, gets into short strips, easier to maintain etc etc. In my book that trumps a twins imagined(?) slightly improved safety (if they are, in practice, any safer anyway).

[Pace]

RT

A Single piston is safe if it is used within its limitations and the pilots limitations. Hence my jokey reference to toy aeroplanes :ok: It is not safe when singles are flown in bad weather, in icing conditions, at night, over water, fog low cloud. wind shear etc then the twin becomes a far far safer machine.

We have done twin safety to death but a twin falls down when an engine fails in the climbout that i put down to inadequate training which should be directed at light piston twins and currency.
Something like a Seneca has an approach speed of 80kts almost the same as a faster single! Twin training is too much directed at climb at all costs and not enough at shut both down and land in a field or do what a light twin does well fly level engine out.

Used properly within their limitations and within the pilot limitations both are safe go out of those limitations which are very different and neither are safe

Pace

[Romeo Tango]

I think we are getting (again) into risk perception here.

My daughter is happy to ride animals that often seem to hurt her and there is a high risk of the horse doing something random and killing her or paralyzing her for life. This is considered perfectly acceptable and many are happy for their teenage darlings to do this without any formal training.

But if I get government approved training and fly her IFR at night in a single engined aircraft this is considered by some to be "not safe" and a silly risk.

Flying a well maintained single engined aircraft in bad weather, at night, over water etc is perhaps not as "safe" as in a turbine twin but it is perfectly safe enough and a much better risk than many things that people do. The single also has many other advantages that suit me far better than any twin.

[Pace]

RT

I agree with your sentiment especially regarding riding horses which is a scary occupation.

We had a long thread on something simular! I try to fly always having an out or never doing anything which becomes Russian Roulette.

Flying a single at night any distance unless its a Cirrus with a BRS is for me flying with no outs if the engine goes bang.

Then its the case of switching on the landing lights approaching the ground! If you like what you see leave them on if you dont like what you see turn them off again:ok:

The same goes over long stretches of ocean, over fog banks, over low cloud etc.
If a pilot wants to play Russian Roulette thats his/her perogative whether you should play that game with unknowing passengers is another matter

Pace

[Flyingmac]

As a child I got around with a pony and trap. My uncle always drove two-in-hand, saying that if one horse dropped dead he could still get home.

I never did have a death in harness. Nor did he.:bored:

[Romeo Tango]

Pace

I do not mind playing Russian roulette as long as there are enough empty chambers, and not too many loaded ones! You are playing the same game in your twin - there are still things that can go wrong and kill you, it's just less likely.

As has been said many times before it depends what risk you regard as acceptable.

I'm sorry you no longer like flying single engined aircraft over water etc but that's up to you.

[Big Pistons Forever]

I think it is pointless to make the single vs twin a binary argument as in one is safer than the other. There are just too many factors that apply

The only relevant fact on this issue that IMO matters is the fact that the second engine only increases safety if the pilot has the skill and knowledge to deal with the engine failure scenario in any part of a flight.

My personal observation is that maintaining true proficiency requires a significant investment in training and practice and that the majority of private twin owners are not willing to make the commitment.


Ok a twin is a real aeroplane :ok: and a single a toy for nice days :E unless its a TBM 850 or Pilatus PC12 :ok:

Pace

The TBM850/Pilatus PC12 are extremely efficient and capable airplanes which can beat the pants off any T-prop twin....until the pilot light in the engine goes out :uhoh:

I bet every one of those PC 12/TBM pilots who have had the engine fail sure wished they were in a King Air. :hmm:

[Desert185]

When I was a full time flight instructor a long time ago, the Chief Flight Instructor set WX minimums for piston dispatch. 600-2 for a single and 200-1/2 (or IFR mins) for a twin. In retrospect, I think that was wise given the circumstances of the flight training operation.

I know when I had a throttle cable disconnect shortly after takeoff in a Piper Arrow (and a resulting slow loss of power), I was grateful that the weather allowed me to circle to another runway and land. Oh, and don't forget to pull the prop control back if you need to when the engine quits or you pull the mixture because there is no throttle control.

Doing practice approaches below mins in a single is really not necessary when they can be simulated with a hood...but that's me at this stage of my life. I am happy to fly the spam can only when the weather is better than marginal. Other's mileage may vary, however.

[englishal]

In order of safety, powered flying machines are safest in this order:

Hovercraft :D
Multi-engine Jet
Multi engine turbo prop
Single engine TP
Multi engine piston
Single engine piston

You can probably insert in there between MEP and SET a Cessna 337 though :) These seem like very good value for money and a great compromise between Single and Multi if you don't want any asymmetric issues....

[Pace]

E

Your list is interesting yet not unexpected!
I fly business jets an engine failure or need to shut an engine down is a non event ! On one engine the jet will outperform a SEP !
The performance of a jet soon clears ALL the weather while a piston single or twin is stuck in the worst!
A jet tends to live in CAS takeoff to touchdown
The pilots will normally be professionally trained and experienced!
Some of the same can be said for the SEP turboprop!
A turbine is far more reliable than a piston with hundreds of bits wirring around !
Piston twins will generally be flown by more experienced pilots and will tend to be more weather resilient than an SEP piston!
So your list confirms what I would think!
Fly within your limits and the aircraft limits and all will be safe!
Those aircraft limits are very different between a piston single / twin / turboprop/ and jet and the problems occur when pilots fly out of their or the aircraft limits or safe operating conditions

Pace

[FANS]

i.e. in inexperienced hands, a twin has twice the likehood of an engine failure causing a crash!

[john ball]

I agree, on a twin you have twice the chance of an engine failure ----- which in the case of many twins means you are going down if fully loaded and the field you are going to land in will have to be longer as your approach speed will be higher. Slightly far fetched, but I would rather be in a PA28 with a dead engine going for that small field in Kent rather than a Piper Apache with six occupants and full fuel and a engine failure on the left !!! Obviously does not apply to the PC12 versus King Air argument.

[Pace]

John

Not true most piston twins fly very happily on one engine level! In my stupid days (nothing much changed :E We shut a Seneca engine down after leaving bournemouth an flew it all the way to france in such a state only restarting to land in france.

If you mean at 200 feet in the climb? yes you have a point but then pull both back and take to a field! At 400 FEET don't even attempt a blue line climb but go for level flight and once nicely trimmed and stable in level flight fly a low level circuit and land or gently step climb using the trim.

The seneca cruises at 128 its one engine out and feathered step climb till you get back to 100 kTS (10 above blue) and hold altitude again until speed builds.
ok if weight is good go for blue line and climb away.

But consider all the options and choose the right one which maybe taking to a field.
How many times in the multi engine rating do pilots practice PFLs as in singles my guess NONE! No wonder pilots fixate on climb at all costs and often at a high cost!!!
Seneca approach speed 80kts Saratoga approach speed (single) 80 KTS other than more weight but beefier brakes whats the difference between landing a Saratoga and Seneca in a field ?

Pace

[Desert185]

All sounds good when at sea level on a standard day...and maybe not close to GW. Anywhere between Reno and Denver on a summer day with an engine out in a NA twin is another story. If I had a twin, I would want it to be at least turbo-normalized. High density altitude is not your friend when down to one engine.

[Pace]

Desert185

Damn that knocks my old friend the Baron 55 out of the loop but not my beloved Seneca five which is turbocharged, waste gated and intercooler :ok:
Good on one up to 16500 feet
Moral to that is do not buy a Baron 55 if operating in high lands choose a boring old Seneca :E

Pace

[wsmempson]

I think the main problem with trying to compare the relative safety of flying twins verses singles is that whilst the machinery is more or less a predictable constant (i.e. one PA28r-200 will fly very much like another, as will one Seneca III fly much like another) the quality of pilots differs hugely.

Whilst I can't claim to have analysed the statistics in any great detail, save for reading all the AAIB reports that have come my way over the last 10 years, the impression that I have is the twins tend to have different accidents to singles, and the more popular the model, the more accidents it will tend to have.

Hence, if you were a spaceman coming to the planet earth and trying to decide which SEP to fly based on the sheer number of accidents, you might decide to avoid Piper Warriors in favour of BD-5's, on the basis that Warriors had more accidents...

There are huge variables in mission profile between singles and twins, with the bulk of the hours in singles being taken up with training and short flights with lots of landings in the hands of the inexperienced, verses twins being flown longer distances very often in instrument conditions, but the biggest variable is in the quality of the nut behind the wheel - i.e. the pilot.

If someone can come up with a way of putting the same quality of pilots, with the same levels of experience, talent and qualifications in both singles and twins and then compare the accident rates, you'll have a meaningful study.

Until then, you'll merely have a bunch of people using statistics as a drunk uses a lamp-post; for support, not illumination.

[m.Berger]

No, clearly not.

[mad_jock]

I never did have a death in harness. Nor did he.

did you have one that started farting on you or went lame?

[Sillert,V.I.]

I'd say the light twin is more dangerous during the takeoff phase and then safer for the remainder of the flight.

Personally speaking and being coldly analytical about my own shortcomings, I'd likely make different mistakes in a twin vs a single. With a twin, I'd likely press on after EFATO & try to keep flying when I'd be better off chopping the power on the remaining engine & landing ahead; or be flying overweight :=; with a single, I'd likely be flying where I've no business being without a second engine & have no safe options for a forced landing :=:=.

Fortunately, my propellors have always kept turning and advancing age seems to bring with it a greater sense of caution - and responsibility.

[dubbleyew eight]

most vintage aeroplanes are singles.

there are some twin engined vintage aeroplanes around.

the question I suppose would be answered if the percentage of vintage singles exceeded the percentage of vintage twins that were in the non vintage original environment.

[Ridger]

From what I witnessed following a few hours P2 in a Twin Commanche alongside a superb P1, I'd say the other salient variable is workload, or at least the potential for workload to square rapidly if things stop working as advertised. It is very easy to point to cases of mishandled engine failures and declare a training deficit (plausibly so in some cases, and I think Pace and others make some excellent points) but it also depends on how high the workload was at the time. As WSMempson said, twins tend to be operated differently and from my own very limited twin experience, they do appear more demanding in terms of monitoring, and operating more complex nav equipment - at faster speeds than are typical for most SEP flights. One might say twins are operated quite similarly to Cirrus SR20/22 so perhaps we have been comparing the wrong fruits...

[Pace]

Ridger

Workload ? Yes a twin is faster but then the jet I fly is a lot faster than the twin! Is the jet harder ? I would say no but not having flown a single for a while I might find a single harder!
Everything is relative including speed and in some respects a Jet is easy to fly I also find a twin is easy to fly but maybe workload is more to do with lack of familiarity!
If it fits like a glove you do not need to think when operating the aircraft and that goes for single, twin , jet !

Pace

[englishal]

I'd say the old twins (you know, the ones with 6 levers :) ) are hardest to fly. The new FADEC twins are much easier to fly. I then flew the Citation Mustang and that is easier to fly than both of the others :), and if you are used to the G1000 setup of the Twin Star, a doddle. The only thing is that it is a bit quicker and things happen a bit faster but all in all it is a piece of p*ss to fly and even easier than the Twin Star when it comes to engine out.

(Emergency decent was the most fun bit of my training - 17000 to 9000 in 45 sec - which is a vertical speed faster than a free fall parachutist :}).

Begs the question....why hasn't FADEC made it to the petrol engines?

[mad_jock]

fedec I think only works using fuel metering injection systems.

[Pace]

its is strange that in a jet up high you have no feeling of speed, a waypoint 400 nm away seems to take forever and you then wish your jet would fly at 1000 kts.

the same goes for a single and a twin.

Where speed does come into it is when you get behind the aircraft and that can easily happen in a single flying low level at 70 KTS a twin flying at 120 KTS or a jet flying at 250 KTS.

In a jet you usually have an FO so He/She takes a lot of the load (A good one They do most of the mundane work allowing you the Captain to sit back and look the part :E A bad one and they increase the load as you are forever checking or rectifying what they do :{

you need to be so familiar with the aircraft that your hands instinctively fly around the cockpit to the correct switches with little brain power involved.
Only then is your brain power freed up to deal with the unexpected.

If your brain power is struggling to simply fly the aircraft any additional loading from the unexpected soon overloads and the workload becomes too much.

Pace

[Ridger]

I agree with you Pace, never a truer word spoken - clearly knowledge, training, currency and therefore familiarity can be reasonably considered components of competence. What I didn't explain at all well in my post was that workload, as a term, relates better to how busy you are, rather than how easy or difficult something is to operate. Although obviously there is a simplistic correlation between the two!

Even Bob Hoover (insert skygod of choice here....) would be busier approaching in a 90 degree crosswind than he would be into wind, even though the task itself would present no problem to him. So returning to the SEP v light twins debate, I would reasonably expect an aircraft with more systems to have greater potential to take even the most competent operator from being not very busy to incredibly busy in a shorter space of time!

[Desert185]

More systems generally result in more capability, and therefore easier to handle in similar circumstances. A 150 horse Apache with one caged landing in a gusty XW at a 4,000' elevation airport vs a 737 with one out doing the same thing, as an example.

Complication or capability?

[Ridger]

Absolutely. If everything works as advertised..

[Rodney Ram jet]

The question is a single engine as safe as a Twin is
only complex if you throw in all the variables. Like
the fact that the Aircraft manufacturers built a lot
of piston twins in the 50s and 60s that will not fly
on one engine at gross weight. And a lot of these
aircraft are in the hands of Pilots that barely fly
enough to maintain currency. But if you boil the
argument down to its essence, the only thing a
multi engine aircraft offers over a single engine
machine is a redundant power supply, so out of
all engine failures, single or multi, commercial
or private how many of each group make safe
landings. The problem is going to be coming up
with this number. If you have an engine failure
on a multi engine aircraft and make a safe
landing, with no damage or injuries their are
rarely any reports submitted to the FAA or NTSB
for the public to access. Case in point, in Alaska
they use DC6s a 4 engine machine to haul freight,
in 13 years hardly a month went by without seeing
one of these machines coming home with an engine
feathered, Ive even seen one DC6 come back with
two engines feathered on the same side, as I was
doing maintenance on these aircraft i was never
asked one time by the FAA for a report on an
engine failure. If you are having a debate on
which is safer a single or multi engine aircraft
shouldn't these numbers be plugged into the
equation. Out of all the multi engine aircraft
I witnessed with engine failures only one did
not come back, out of the single engine aircraft
with power failure only one Cessna Caravan
made a successful dead stick landing. 20 years
in aviation has taught me one thing for sure
aircraft power plants are designed, built and
maintained by men, and no matter what type
of power plant you have turbine or piston
if you run it long enough it will fail. Even
Pratt & Whitney says the failure rate of the
PT6 turbine engine goes up dramatically after
the third overhaul.