Double trouble: have twins suddenly turned deadly?

In the course of a few days, two old piston twins, a Model B55 Baron and a Piper Navajo, crashed, killing six in each case. There was a family of three, a friend, and two pilots in the Baron. They were going to a graduation. Professional folks, three couples, returning from a meeting were lost in the Navajo. Terrible tragedies.

The NTSB will be a while getting out probable causes so what I am going to share here comes mostly from newspapers and TV accounts as well as from NTSB preliminary information and some basic research. I am doing this to see what, if anything, has changed since I wrote an article entitled Double Trouble (what else?) on the same subject in AIR FACTS over 50 years ago. I’ll tell you in advance that while some things never change, others do. My main question about the recent accidents was whether or not they were related to the failure of one engine and the resulting asymmetric thrust.

Baron in VA
The Baron stalled and spun into the trees at the end of the runway.

The Baron was landing on a 2,999 foot long runway, it touched down about midfield, bounced some, and then the pilot apparently thought things were not going well so he aborted the landing, staggered into a go-around, lost control and crashed.

The first thing that came to mind was the center of gravity. In a basic Baron with six on board (three were teens but from the pictures they were grown) to keep the center of gravity in limits there has to be some weight in the nose baggage compartment. This was likely there, but the cg could have been close to the aft limit which means the airplane would have been none too stable in pitch.

A brief solo hop got the airplane together with another pilot and the five passengers. There was some discussion there about the fuel load which was apparently limited some because of the cabin load. The departure and flight appeared to have been routine.

A balked landing can be a whole ‘nother matter, though, especially when using a runway that is none too long for the airplane. There are trim changes, configuration changes and performance challenges. Couple that with the sudden stall characteristics of airplanes of that vintage, especially twins, and events can come to an unfortunate conclusion.

Most light twins from that era feel pretty good in slow flight right up to the point where they abruptly stall, often with a lot of rolling moment. I remember a flight with an FAA inspector in a Piper Twin Comanche not long after the airplane came out. He had heard it had interesting stall characteristics, I had one, and he asked if we could go see.

See we did and I can only say that we both agreed on the control inputs required for a recovery from inverted flight because we were both on the controls, both doing the same thing. Neither he nor I ever again flew a Twin Comanche well into a stall.

So nothing has changed over time. The aging fleet of twins is just as unforgiving of a pilot getting too slow too low as it ever was.

Piper Navajo
Why would both engines quit on a Navajo?

According to the NTSB preliminary report, the Navajo pilot reported that he had lost a fuel pump and wanted to divert to a nearby airport. En route to that airport, the pilot reported that he had lost the other fuel pump. I would presume that when he reported a lost fuel pump, it meant the engine had failed. After that the airplane descended steadily until it hit trees 1,650 feet short of the runway. Nothing in the report gave much hint about whether or not the pilot lost control of the aircraft but the condition of the wreckage suggests that as a possibility.

I have written about similar crashes involving one failed engine. The pilot usually starts the engine-out arrival with an abundance of stored energy, altitude and airspeed, and as the approach unfolds that energy is not used properly. The airplane winds up too low on approach and, with the added kicker of asymmetric thrust, the pilot gives away too much airspeed and one of those abrupt stalls I mentioned a moment ago occurs.

In this case asymmetric thrust does not seem to have been a factor and when the final report is issued there will likely be word on why both engines apparently failed. I can think of only one logical reason. Whatever the reason, there is not likely to be a lot new about this accident. It could have happened recently or at any time in the past 50 or so years.

There is no question that pilot skill plays a larger role in light twin accidents than it does in single-engine retractable accidents, for example. I think a go-around in a Bonanza is less demanding than one in a Baron and a single-engine or dead stick landing in a Piper Malibu should be easier than one in a Navajo. An engine-out landing should be easier in a Navajo but, unfortunately, that does not always seem to be the case.

It has often been said that a pilot buys a light twin and flies it successfully until one engine quits, then boom.

One thing that changed a bit over time with twins is the relationship between asymmetric thrust and accidents

Fifty years ago about 20-percent of the fatal accidents in light twins were related to the fact that the airplane had two engines and was attempting flight using but one of those engines. More than half those accidents happened during instructional flight. Recently almost half the twin accidents were related to asymmetric thrust and almost half those were in training. The sample today is much smaller and thus less meaningful.

Aztec on one engine
Vmc demonstrations at low altitude are a terrible idea.

There was a logical reason for so many training accidents years ago. The FAA required that Vmc (single-engine minimum control speed) demonstrations be done as low as possible but not below 500 feet a.g.l. Vmc is usually close to the stall. So here is the airplane perilously close to the stall at 500 feet when the power on one engine is retarded. It takes little imagination to see what might come next.

The first accident related to this policy came during a check ride being conducted in a Beech Travel Air by an FAA inspector. I knew three of the four people killed (two were observers) and one was a close friend. The date was July 22, 1958, which also happens to be the date I went to work for AIR FACTS.

Many more such accidents followed, usually in Beech Travel Airs and Barons and Piper Twin Comanches. If the trouble started high enough, the airplanes would come to the ground in a fully-developed flat spin. The Army lost one of its most experienced T-42 (Baron B55) instructors in a flat spin that I heard started at 5,000 feet a.g.l.

It took years but the FAA was finally convinced that its procedures led to awarding the rating to the survivors of multiengine training. The Vmc demonstration and training requirements changed pretty dramatically.

Two other things that helped with the training problem have been the Beech Duchess and Piper Seminole light twins. These airplanes are much more mannerly at the stall and Beech actually did full spin tests on the Duchess, including spins with one engine wide open and the other shut down, and it was always recoverable.

There are few flat spin accidents in light twins today, mainly because the airplanes that were prone to that are no longer used as trainers.

When teaching multiengine students, I insisted on landings with one engine secured, prop feathered and all that. This was controversial because some thought it involved too much risk. My justification was that I did not think multiengine pilots should be put into the position of having to do something (an actual engine out landing) for the first time with passengers on board.

The airlines were able to take the risk out of engine-out training with simulators. Unfortunately that can’t quite be fully accomplished in piston twins though some of the training aids available now come pretty close.

Plenty of attention was always placed on the vaunted engine failure on or soon after takeoff. All that training and practice was aimed at maybe two minutes of each flight. Most light twins will, in two minutes, get off the ground and up to, say, 1,000 feet in that length of time. Once there, and regardless of where and when the failure occurs, the challenge becomes getting the airplane safely back on the ground.

Piper Seminole in flight
Modern twin trainers like the Piper Seminole are much more forgiving.

Getting back down might not seem like much of a challenge. Apparently the FAA doesn’t think it is because in the official publication Flying Light Twins Safely there are only two short paragraphs about engine-out arrivals. Trouble is, there have always been more fatal crashes during engine out arrivals than after mechanical failures of engines at a critical time on takeoff.

I always liked to teach that there is a critical altitude above the ground when considering any engine out scenario. The altitude is the same for a departure or arrival and depends on how sharp the pilot is. It might be a couple of hundred feet for the ace of the base and a thousand for a lesser pilot.

On takeoff, this is the altitude from which you would have good options if an engine failed. On arrival it is the altitude below which you are totally committed to a landing, no go-round allowed.

Quite a while back (40 years ago) there was an actual Baron 58 engine failure at the worst possible time on a night takeoff from a normal-sized general aviation airport. A prominent politician and his family were lost so there was extensive discussion about the accident.

It was determined that the crankshaft broke and the engine abruptly lost power at or right after liftoff. The pilot apparently failed to retract the landing gear but he did attempt to continue and subsequently lost control and crashed.

If I recall, it was determined that, all things considered, if the pilot had done everything perfectly, it might have been possible to maintain control, climb slowly away, and fly to a successful landing. I have forgotten whether or not they addressed this but the pilot could also have aborted the takeoff and avoided the out–of-control crash that killed Congressman Litton and his family.

What I took away from all that discussion is that few pilots could master the burst of brilliance and fancy footwork required to handle an engine failure and continue successfully given those circumstances.

I’m talking about legacy airplanes here. Most consider that to mean those built before the drastic contraction of light airplane manufacturing in the early 1980s. Most of the airplanes considered are over 35 years old, many are as old as 60. I mention this because some of you might wonder about the Cirrus and Diamond airplanes in relation to the discussion. Simple. They weren’t born yet so are not considered here.

Cirrus SR22
Are modern singles killing the old piston twin?

It was always interesting to compare the piston twin and single-engine retractable accident picture. The airplanes were and are used for similar missions, mainly transportation, and are usually flown by pilots of similar training and capability. A lot of pilots thought they were buying safety with a twin and the numbers often showed that not to be true. Some of the retractable singles had lower accident rates than similar twins.

I looked at the relationship between accidents in these two groups of airplanes and IFR activity and nothing has changed much over the years. They are in the IFR system and are involved in fatal accidents in about the same ratios now as 40 years ago.

I did come up with one raw number that was quite surprising. I knew that both fleets are smaller, because of a lot of low production years as well as a lot of attrition. I also knew that the individual twins fly less now than then, mainly because of maintenance costs and the perceived need for payday loans at the gas pump. I also knew that this meant there would be substantially fewer wrecks today because hour-based accident rates have not changed all that much.

I had no idea how many less until I compared 01/01/2016 – 08/16/2016 with 01/01/1976 – 08/16/1976. You ready for this? 2016 – 12, 1976 – 70. Yikes. You can hardly look at that number and conclude that piston twins are having more trouble now than then.

My interest in this post was prompted by current events. It turned into a history lesson because it is becoming ever more apparent that the piston twin is slowly but surely joining the brigantine in the history of human transportation. Too bad because they sure were fun to fly.

53 Comments

  • I always loved the Beech 18 and even considered buying one for a short period in mid ’70s. I never really got around to finding out how difficult they were to fly. The Internet was not around then. I did know the old saying that a twin meant that when an engine quit you had another to fly to the scene of the crash. I also heard, rightly or wrongly, that the big issue was confusing which engine was out.

  • I’ve always wondered why push-pull designs like the Cessna Skymaster, which avoided the asymmetry problem, didn’t become more popular . I suppose they must have had some other drawback. It would be interesting if the experts on this thread shared their thoughts on this.

    • One drawback I’ve always heard was the terribly loud noise the 337 produced. Never heard it person though. I would love to see more air frames with that engine configuration in mind. I know the new Double-Ender is a 2 place, tandem bushplane with a push-pull engine setup. Most twins seem to worry me as a single engine pilot.

  • So well-written . As always !
    You summarized the chain of events leading to accidents very well. When load,CG and fuel are at their edge in light twins, no room for error when problems occur. As an amateur, but very serious and dedicated instrument private pilot, I’ll stick to single engine fixed gear Cirrus. Keep bringing great articles !

  • I do not have the same experience as Mr. Collins, but I do agree that practice landings in a light twin with an engine fully shut down is too high a risk for training. Especially given the statistics you list about the high number of accidents during training. This seems like the kind of activity better suited to a simulator. Is it that much different than a simulated engine out landing that you felt the risk was justified? I do understand your concern about doing it with passengers the first time, but we don’t do full engine-out landings in single engine planes, and all of us might indeed find ourselves doing it for the first time with passengers.

    • The concept here is ” training with an experienced CFI”, the risk is minimal once you learn how to do it safely.
      I fully agree with Mr. Collins in practicing real life scenarios.

      • I think you meant MEI (multi-engine instructor) and totally agree on some real world experience. I to do not have as much experience as Mr. Collins, but I do have over 10,000 hours of which 0ver 9,000 being in multi engine aircraft ( 2, 3, and 4 engine aircraft). I haven’t flown a single engine aircraft but once in the last 30 years…..lol.

        • Tim,

          CFI with multi engine rating and experience.
          CFI is a certificate. Multi engine is a rating.
          To be exact CFI with multi engine Land, Instrument Airplane ratings.

          Thanks

  • A question for Dick:

    Do you have any data available comparing the Piper Seneca, with its counter-rotating engines (and thus no “critical engine”) with competitive aircraft like the Barons, as regarding asymmetric thrust-related accidents? The counter-rotating engines feature has been discussed, if not advertised, as a safety feature, but I’ve never seen any data to indicate whether it makes a significant difference in accident rates.

    • I have never seen anything on that. The Seneca was never used a lot for training and the airplane has pretty tame stall characteristics but today it would probably have about the same record as the Baron. Both airplanes are now used primarily for transportation so the risks are pretty much equal.

      • I used both referenced twins for training ME applicants. The Seneca is a bit easier due to no critical engine.
        The Baron(58) is more demanding to the inexperienced pilot and consequently more dangerous.
        To the experienced and proficient however, is more capable in an engine out emergency, as long as the pilot acts ” swiftly and accurately”.
        I love the BE58 engine out performance,I just need to be ahead of the airplane.

  • My friend with over a thousand hours in a Navaho bets that the pilot here failed to switch tanks after running the inboards down to empty…… The fuel gauges show the quantity in the select tanks (either inboard or outboard), so the pilot must not have noted he was running the selected tanks down to dry…..flamed out both engines all the while having fuel in the outboard tanks…..

    • I fear the exact same issue played out in the Baron crash. If fuel was still selected on aux tanks (level flight only), and those tanks are low on fuel, they will “unport” and one or both engines will quit as the aircraft accelerates and pitches up.
      Richard is spot on as well about the aft CG and pitch instability at low speeds while on final to a short runway. Some extra speed calms the pitch oscillations, but not worth touching down with half of a 3000′ runway behind you.

  • Also, I think you need to look at the qualifications of the pilot’s involved including time in twins and currency in that particular twin aircraft!! This would include knowledge of all the systems. In my B55 before every take off and landing I brief myself as if I’m going to have an engine failure. I brief myself on obstacles on my departure path and arrival path including of course density altitude. Also, just prior to VMC, I scan my Engine Data Monitor to make sure nothing is starting to go South. If you have passengers on board, we all know the FAA requirement of passenger briefings.
    Practice but don’t feather. Set zero thrust to simulate.

    • Thanks Jim !!!!
      That’s the way to do it, always on your toes taking nothing for granted.
      I hope everyone befits from your personal checklist, myself included.
      Fly it as if it were the first time, no complacency.
      Cheers

  • Double Trouble

    My comment is a question. Is the fact that engineers have not successfully engineered out the asymmetrical phenomenon that happens with an engine. It seems as if Velocity Aircraft Co seems to have figured out how to greatly engineered out this phenomenon with their twin pusher.
    It seems that these accidents happens more times than need be resulting in many pilots and families lives lost. I’m a student pilot for the moment [ meaning until end of Oct./16] and read a lot about aviation especially accident analysis. I’ve learnt so much ” don’t do’s “from reading these types of articles.

    • Derrick,
      Engineers have solved the asymmetric thrust problem in numerous ways, the push-pull configuration of the Velocity airplane and the Cessna Skymaster only being one of the ways to do it. I personally was involved in a project which combined two PT6 turboshaft engines to drive one propeller; another way to do it. The bigger problem than asymmetric thrust is the startle factor one experiences when confronted with an airplane that used to climb 2000’/minute that has suddenly changed to one that climbs, maybe 200’/minute. The urge to pull back is very strong even if there is no asymmetric thrust: And that’s not good no matter how many engines are onboard.

      • Great point Stephen !!!
        That’s what I try to instill on my students practicing emergencies.
        The yoke needs to move instinctively to maintain proper A/A (angle of attach) without reaching the LOC (Loss of Control) regime.At the same time we need to know what our options are and execute a safe landing.
        Personal minimums checklist mitigates the risk.
        If we don’t know how to meet any Emergency, we need to find a good mentors and ask them to sharpen our shills.
        No excuses.

        • Chris – I think what Stephen is describing – “The urge to pull back …” – is not what you are describing. Of course you know very well that the problem with one engine making full power and the other one dead but unfeathered is that the pilot has to do a heckuva lot more than simply “not pull back”… and he/she has to do it almost instantaneously, particularly when losing an engine on takeoff down low as in a normal takeoff or a go-around.

          The pilot has to instantly lower the nose at least to a level attitude while simultaneously feathering the dead engine and applying strong rudder pressure opposite the dead engine. Otherwise, in a mere heartbeat the asymmetric thrust will roll the airplane over on its back and likely kill everyone on board before the pilot has but an instant to think about it.

          Of course, many twin pilots are also known to mis-diagnose the dead engine and instead feather the good engine. That happened to a twin-engine commuter aircraft in Taiwan a couple years ago killing everyone aboard.

          This is a far riskier scenario than losing an engine in a single engine aircraft during a go-around or balked landing. And in this scenario, it does not really matter much what the stall characteristics are of the airplane, be it a Piper Seminole or a Beech Baron, because the issue is NOT a stalled wing, the issue is dangerous asymmetric thrust at low (but still well above Vs0) airspeed, i.e. a “Vmc spin” or “backflip”.

          That is a very tall order even for pilots who are highly competent and totally situationally aware. Most real pilots aren’t, most of the time.

          • The other “instant decision” with an engine failure on takeoff in a twin is that the pilot has to know where his airspeed is with respect to Vmc when the failure initiates, for the actual conditions of the aircraft (gross weight, center of gravity, gear down or up, and field elevation/altitude) that determines the actual Vmc as opposed to the theoretical “worst case” Vmc for his aircraft … and, if he believes he is at or below this “actual Vmc”, then he has to do the opposite of what a pilot instinctively wants to do, which is to immediately yank power back on the good engine.

            Again, this is a might tall order for any pilot … to assess all of the above factors and make an instantaneous and correct decision … knowing that any delay in acting OR making the wrong decision will also ruin his day.

            That’s why the worst case scenario – losing an engine on a twin on take off at very low altitude – usually results in a very bad day for all involved.

          • P perceive
            P process
            P perform

            Have you studied and practiced the 3-P Model ?
            That’s not what the man wrote above your ill conceived comment.

  • Practice maneuvers and stalls
    I’ve been an instructor for 50 years and an engineer even longer
    Basically, single or multi, guys get their tickets and never do the air work again
    The bi-annual helps, but just practicing for one hour every 24 months just doesn’t hack it

  • Navajos have engine driven and electric fuel pumps. Electric pumps to be used for takeoff and landing. I can’t imagine that all four pumps would fail. I agree with the commentor that fuel tanks were probably not switched. Or maybe total fuel exhaustion.

  • Frankly, I doubt that an asymmetric thrust/engine failure was involved in the Baron accident; instead, it appears to be a pilot error, beginning with a too-fast long landing, attempts to force the plane onto the ground, and insufficient runway remaining, with trees rapidly filling the windscreen. At that point, airspeed would likely have decreased significantly, and a panicked pilot may have yanked the yoke back, the plane waddled out of ground effect urged on by a combined 520 horsepower, and stalled into the trees. The same thing would probably have happened in a high performance single, with the only difference being a stall from a lower altitude, or simply flying into the trees still in ground effect. Also, the overall scenario sounds a bit like it was prone to a problem: one pilot flys to another airport, picks up another pilot and four other people, then they fly to a college event and return. What were the qualifications of each pilot, and who was flying the airplane? Could this have been a demo flight to a prospective buyer looking to move up to a twin? A 2,999 foot runway is quite adequate for a B-55, unless one is not proficient in the airplane, and a long, hot landing and bouncing repeatedly sure seems to indicate a lack of proficiency. I have owned several Cessna 310s (30 years + of owning 310s alone) and also owned a B-55 a number of years ago – an early go-around would have prevented the accident, as it would have in a single. Of course, one must be current in any plane flown, and must stay ahead of it. This is especially critical in a twin, but also important in a high performance single, as well.

    In the case of the Navajo, excess air in the fuel tanks will turn any airplane, single or twin, into a not so efficient glider. I doubt either accident was a result of the airplane being a twin, as similar problems would, likely, have resulted from each situation in a fast single.

  • Richard, I read both of the articles and you have written them beautifully.
    My question is about the stall characteristics mentioned in the article, mostly how the wing flies well right utill it stalls hard. It seems to me this is likely a signifigant factor in these accidents because the pilot has no warning until after its too late to correct it. Granted, a pilot should know to keep the speed up on one engine, but during an actual engine out emergency pilot workload can be pretty high. I wonder if the accident record would look differently if Harry Riblett had completed his research and written his book before piston twins hit the market in the 1950s. It looks to me the piston twin safety record would greatly benefit if the airplanes had more docile handling characteristics to start with.

  • I have owned my Twin Comanche nearly 50 years. Years ago I modified it with the Robertson STOL kit and the right engine was replaced with the counter rotated version during the first round of engine overhauls. I consider it a real improvement in single engine safety. Vs is 63mph , Vmc is 75mph, I have flown home single engine twice from mountain terrain that had no single engine landing sites available. …broken oil cooler and fuel blockage caused by ice, I consider and plan my take offs with thought about go/no go if I lose thrust on one.

  • It is hard to land any airplane aft CG on a short strip, much less a fully loaded B55; first link. Waiting too long to recognize the necessary go around; second link. Trying to make the aircraft climb beyond its performance ability makes link number 3. Would have happened in a single just as well as a twin, IMHO.

    • Ronald, I think you nailed it.

      That airport can be challenging in a hot sunny day in a fully loaded airplane. It is not that the airport is particularly difficult, only that it can be unforgiving if you are near the margins, especially under full sun on a 95+ degree day no matter what airplane you fly.

      There is a reason you learn how to calculate take-off and landing distances required for every solo flight you take. It is to warn you when the airstrip that you intend to use is a tight fit for your airplane with today’s weather. It is to remind you to be extra careful on your landing because there is little room for error…TODAY. In this airplane, with this load, at this airport, and this prevailing weather. TODAY is the day to be spot on with your approach or be ready to abort early and go around. TODAY is the day your short field training counts.

      Sadly this warning was missed and the pilot and passengers paid for it wth their lives. So sad.

  • All pilots do well if they pass the practical test with the DPE.
    The certificate is a ” license to learn”, unfortunately many pilots do not continue education after the test.
    I see pilots who will do anything to find a CFI to get an ” easy” Flight Review so they can come back to the same person to ask for the same “easy” FR again.
    The retired FAA inspector I know calls that ” easy” CFI ” the Brother in Law “. It might sound funny but it is actually tragic.
    If my life and other innocent lives are at stake, why do I do such a crazy ting ?
    Is it due to ego ? Perhaps.
    I own the thing and nobody can tell me I can’t fly it ? Perhaps.
    To the contrary, there are those of us who really care, always willing to learn and humble, like many of the sensible pilots who commented above. Thanks !!!!

  • Like everybody else, I really regret that so many engine failure related accidents happened and took the precious lives of so many fine people.

    I am a graduate of the USAF Test Pilot School where I learned to flight test multi-engine airplanes while an engine is inoperative. Following retirement, I researched some 400 engine failure related accidents: 3.600 casualties in 25 years is way too much and not at all necessary. Unlike investigators concluded, the real cause of most of these accidents is that pilots, their instructors and also accident investigators do not get to learn the true story about the controllability of asymmetrical powered airplanes anymore. Most Airplane Flight Manuals and pilot course books present a definitely incorrect definition of Vmc and do not present the conditions that apply for the published Vmc (=Vmca) to be valid, which are: straight flight only while banking a small bank angle away from the failed engine (usually 5 degrees exactly, not max.!). If straight flight is not maintained or the bank angle is not 5 degrees, the actual Vmca is a lot higher, as is the drag, leaving no climb performance at all in many cases; a crash cannot be avoided. Turning at or close to Vmc while asymmetrical thrust is high is asking too much of the airplane; the vertical tail was not designed large enough to maintain control.

    If you are a pilot, and want to return home safely after you experienced an engine failure, please read my papers on the subject that can be downloaded for free from the downloads page of my website: http://www.avioconsult.com/downloads.htm.
    I also published an amateur video but with highly professional content on engine-out flight; please refer to the AvioConsult channel on YouTube, or click:
    http://youtu.be/Wbu6X0hSnBY. Over 11.000 views already.
    Other pilots or your instructors might tell you not to believe this, but my papers are written using my Test Pilot School course books and Airplane Design Series of books (by Dr. Jan Roskam, KU) used at Aeronautical Universities for sizing the vertical tail of a multi-engine airplane. This knowledge regrettably faded away from pilot training during the past 50 years.

    I also commented on an FAA course; even the FAA does not teach Vmca as Test Pilot Schools and aeronautical universities do, while their own Advisory Circulars/ Flight Test Guides are presenting the right theory.
    References are presented in the papers and on the downloads page of my website.

    Fly safely.

    • Harry,
      I’m a CFI for thirty plus years and I vividly remember my ME training as well as all the dual instruction given to my MEL students.
      I received MEL instruction that dealt with Vmc and instructed my students in a way that they knew what Vmc was and practiced Vmc demonstrations at altitude including stalls, engine out emergencies and all the rest per FAA PTS.
      What you are describing regarding Vmc is no different than what we learned and passed on to our students.
      The certificated accident pilots received the same training. The reason they are dead is because they did not meet the emergency for reasons outlined by this discussion.
      Not because they did not know what Vmc was. Perhaps they were rusty or complacent, sadly.As a teacher, I appreciate your effort to teach. The way you present your page, it looks like ” infomercial” to me. I like to think of myself as a teacher, not a professor.
      Thanks !!!

      • Chris,

        What Harry seems to indicate in his analysis of Vmca, and I alluded to in my comment above in this thread, is that, for most pilots most of the time, the notion of recovering from a full power/low airspeed loss of an engine on a port-and-starboard twin is just a fantasy. It is taught because someone has to go through the motions of certifying the twin pilots.

        Just because there are thousands of ME instructors who teach the published recovery procedure – up high, ever since the FAA learned, as Dick described, that low altitude ME maneuver training was a proven killer – that doesn’t make the notion of loss of engine recovery training any more plausible in actually preventing accidents.

        The problem isn’t the pilots – the problem is the mechanical port-and-starboard twin design itself.

        It really comes down to pilot luck, good or bad, rather than skill, if you fly a twin. If you suffer an engine failure immediately after takeoff, there is not a plausible recover scenario unless the pilot is fully on a hair trigger alert to instantly cut the power on the good side, assuming the pilot can make a correct decision as to which engine is bad (which is not a sure thing).

        The bottom line here really, the one that nobody likes to discuss, is that the port-and-starboard mechanical-engined twin is an inherently unstable, unsafe design. Safety is achieved mainly through good luck.

        The markets have spoken too. The perceived safety benefit of a twin has been debunked for decades – there is none, not when factoring in what actually happens most of the time when a twin loses one engine. And the economic argument is clearly on the side of singles. As a result, there are very few twins still being manufactured and sold today compared with singles.

        It seems it would be a lot easier and simpler to simply go with electro-mechanical drives, with internal combustion engines driving generators that power multiple electric motors on the wings so that thrust is maintained symmetrical at all times. NASA is experimenting now with designs that feature many electric motors distributed all along the wing leading edge. I think that is the future of multi-engine aircraft.

  • The article is about Light Twins.
    They have been around for many years and most of us deal with the problems on hand.
    Never heard any experienced self respecting pilot or instructor to claim anything more than what the under-powered LT can offer.
    The first think I teach my students is that LT airplanes are ” double trouble” as Dick very well put it. Simply stated, I draw a horse carriage on the board with two healthy horses pulling. One dies all of a sudden and the question is, who is pulling the carriage now ? One horse only and the load is higher now due to the dead horse causing more “trouble”.
    That makes every sensible student aware of the problem and we go deeper into performance charts and physics at play involving bad engines.
    We do ” air-work” at altitude for safety, as we do not do stalls in any airplane low. These procedures are an ever evolving ORM that were unknown in the early days.
    Correct Vmc demonstration to the DPE is a way of expressing ones knowledge and how to stay alive. The FAA does not advocate that we fly a LT at Vmc with the critical engine inoperative. It will never get you anywhere safely except the scene of the accident. It is all about LOC avoidance and lateral control, so we can have some extra time to mitigate the emergency.
    In the case of the ATR accident, thrown in the comment for sensationalism, it is a totally different animal and was designed to mitigate the loss of one engine and still climb as long as the pilots are ahead of the airplane.

    • C’mon, Chris … you’re being defensive here. There is no knock on instructors for trying to teach aspiring twin drivers from how to mitigate the fatal flaw of the port-and-starboard light twin design, despite the fact that doing so really doesn’t change the risk equation very much at all.

      Sure, we can spend our entire lives blaming pilots for not practicing enough, or getting too complacent, etc. etc. But a design that relies inherently on pilots behaving perfectly and instantaneously as if we are Super Men and Women is an inherently unsafe design that should be discarded in favor of better technology that is already here.

      There’s absolutely nothing new about “hybrid” electro-mechanical propulsion – it’s been the norm in railroad locomotives for 70 years now, in diesel submarines for 116 years, and in automobiles in the last decade and a half. And it is coming to airplanes as we speak.

      Indeed, with a hybrid powerplant, motive redundancy comes from having both an internal combustion engine and a battery to store power. It’s easy enough to hang multiple electric drive motors along the wing or in nacelles mounted on the fuselage, and electric motors with only a single moving part almost never fail.

      The problem is the design of the twin engined aircraft, not with the quality of the instruction or the quality of the human pilots. Any more than it was the fault of instructors or their students in the early days of aviation when those early aircraft tended to fall out of the sky at a horrifyingly high rate.

      As for the ATR accident, it is not that uncommon to feather the live engine. Indeed, within minutes of the press reports hitting the internet, on aviation websites quite a few of the professional pilots commenting immediately questioned if that was what happened just based upon how the aircraft behaved (it was caught on video) and their knowledge that shutting down the wrong engine is NOT a trivial or unlikely outcome. It’s not sensationalism – it is recognition that human pilots are not perfectly programmed machines, no matter how well we’re trained or how conscientious we all believe we are.

      As a professional trainer, you think the answer is always training, practice and “attitude”. I would submit that you sound like the proverbial hammer who thinks every problem is a nail. I also submit that any system that depends upon humans reacting perfectly is a poorly designed system.

      • What I hear you saying is, pilots need no practice on Light Twins.
        It is useless due to design limitations, some might survive purely by luck.
        How do you arrive there ? Have you any personal experiences on Light Twins ?
        If so please share it, not so much for me but for the sake of the pilot who might be saved after you enlighten all of us here.
        Thanks !!!!

        • Chris,

          With all due respect to your abilities as a professional flight instructor, I did not write that twin pilots don’t need practice – what I wrote is that the light twin training and rating regime does not result in safe operations in the real world because of flaws in the light twin design. Despite many decades of ME training and ratings, the result is still the same – a very bad accident is usually the result of an engine failure during the initial takeoff climb, which is precisely when an engine failure is most likely to occur.

          Indeed, think about it, Chris – one of the largest sources of fatalities in the ME fleet for decades was ME training flights at low altitude, with so-called expert ME flight instructors in the cockpit. How is a non-expert owner-pilot expected to do better than the experts?

          As they say in business, the bottom line is the bottom line.

          Practice and skill is simply not sufficient if the system being operated depends 100% upon pilots acting perfectly in order to survive a system failure.

          I am both a lifetime pilot and an engineer. In the world of engineering, the light twin aircraft represents a classic example of a fatal flaw in a single-point failure system. Good engineering practice always seeks to avoid designs where the results of a single point failure would be catastrophic, as with loss of life.

          So what should pilots do with this fatal flaw single point failure light twin?

          My recommendation is don’t buy or fly light twins with engines mounted on the wings until they are engineered to be safe as flown by real world imperfect pilots.

          The latest Diamond DA-62 is a start down the right path, with its FADEC engine controls and single-switch feathering. But it’s still far from safe until it also incorporates autofeathering and autothrottles designed to instantly balance thrust in the event of an engine failure … better yet would be hybrid power plants with multiple electric motors like NASA is working on. That’s the ultimate solution.

          I used to believe, like most pilots once did, that the light twin was the ultimate in light aircraft safety, and worth the extra purchase and operating costs over a single. Now we know better.

  • In the recent post I made, it was in a form of a question concerning the ” engineering design ” of the twin / multi-engine A/Cs to the story ” Double Trouble”. Just a reminder that I’m still a student pilot who’ll soon be a certificated pilot and after reading all of the comments posted since my post, my consideration to own a twin has really left me to only one choice. The Velocity Twin Pusher. Again, it seems to me that Velocity and Piaggio manufacturers/designers got the design issue right. HOWEVER, being an Operating Engineer of cranes; excavators and; 17 ton hi-lo for the energy utility in the NYC area, There Has Never Been A Substitute for Continual Training and Practicing of ALL associated tasks concerning operation of heavy equipment to remain proficient and safe. And last I heard, an A/C whether single or multi-engine is considered a type of heavy equipment ( being twins weight comes in at the 10.000 + lbs being on the bottom end just about where heavy equipment begin at ) that requires that level of professionalism. I’m not ruling out the design flaw of the traditional ME A/Cs [ as you can see I’m bias to the canard pusher types 🙂 ]because I do see a need to, if possible, to engineer out that extremely dangerous phenomenon that takes place when a critical engine goes dead. I’m a new pilot, yes. But I’ve had an interest in aviation since I was in grade school and now its has started up again with even more passion now that I’m an adult. But fellow pilots, instead of arguing and debating, let’s us come to an consensus to insist that we as pilots/operators of ME as well as SE to do whatever can be done to begin a journey to eliminate the senseless loss of lives in A/Cs whether it be due to mechanical problems or operating inefficiencies. Even if administrative controls needs to be implemented to deal with pilot errors. I really believe we already have good A/Cs even with what we consider to be design flaws but I believe we have a bigger problem surrounding inefficient pilots behind the controls of a complex pieces of equipment. No matter how light/slow; heavy/fast these pieces of equipment may be; the two categories still require skillful handlers behind the controls. And skills comes from Continual Training and Practicing which may be an 80% antidote for the design flaws of ME A/Cs. Just thinking out loud……

    • As far as your future choice of a multi engine goes, it will be up to you to decide.
      My only advise to students and experienced pilots is, I will not steer you to a specific airplane, sales people do that. I am in the education field, no matter what you buy it is my duty to make you better and safer by becoming your mentor.
      I’m here to tell you that becoming a statistic is an ever present danger when we defy the laws of physics.
      Focus on your current training and be as best as you can be. One day things will be clear for you as to what Light Twin suits your needs. I hope that day is long after you acquire good SE experience and Transition training to High performance and Complex aircraft.

  • Derrick,
    The real reason behind reading and commenting on Mr. Collins’s article is that, I trust his judgement and admire his experience. I always learn something from Dick,because I see myself as a learner.
    When I post a comment my aim is to help pilots like you become safe/ proficient and self sufficient in the quest of “always learning”, because as you stated very well training is endless.
    I take issue with others who have ulterior motives. Some want to attract traffic to their website by casting doubt so they can destabilize the unsuspecting for personal gain. Others want to satisfy their ego by professing something they do not really know.
    Things are simple for a true aviator, regardless of how long we fly, a student like you or an Ace like General Yeager use the same controls to fly an airplane, stick and rudder.
    On take off and climb for example on your C-150 you use right rudder and wings level to gain altitude and maintain runway heading. If a thermal or a sudden gust disturbs your desired attitude and heading, you correct sooner or later depending on your experience and skill. Eventually we learn how to correct almost instantaneously as Pilots in Command.
    Let’s try the same T/O and Climb in a Light Twin.
    Will you allow your heading, pitch, yaw and power take you upside down to the scene of an accident ? A sensible PIC will not allow that, I wager !!!!!
    No matter how violent the force, excluding air-frame and control surface failures, a PIC input should correct the problem including but not limited to throttle movements. Note that engine failures are not mentioned as an excuse ……
    ACS and PTS are designed to help us achieve and maintain Safety Culture. PTS have been around for a while ACS is new and is here because lots of good folks got together and worked hard to make Aviation Safer.
    When someone says they know more than you do, claiming that they and some other ” elite few” know the answer ? Think again…. and I suspect you know.
    Good luck with your journey of continuous education !!!!!
    ” Safety is no Accident”

  • Hey Chris,

    Here’s a question for the folks about design flaws in a twin is the ultimate culprit of ME accidents. How did Captain Sulley and his co-pilot manange to make a successful landing in water at that, with minimum injuries?” Now keep in mind that they had to deal with the same critical engine-out problem because both engines did not fail at the exact same time. I’m will to wager my entire yearly salary that it wasn’t by accident but surely be intent!! And that intent comes from continual training and practice!!!
    What do you think?

    • Derrick,
      One should not compare apples and oranges, as you know.
      The only similarities between Light Twins and Twin Jets are the number of engines and the airframe resemblance. The first has piston engines with propellers the latter has very powerful turbofan engines and surprisingly as large as it is has a very impressive (L/D) glide ratio about (20: 1). If an A320 lost one engine, the good engine is very capable of climbing at a very good rate and return home or continue at the point of no return so it can land at a suitable field.
      We need to reflect on Airline pilot training that is a state of the art repeated practice with no exclusions. The check pilots are training even harder and no one in the industry makes excuses about technical flaws.
      Without being very technical about light twins, one shall seek Multi Engine Rating long after they become very proficient in SE/ High Performance/ Complex aircraft. Then ME will be easier provided the pilot exercises common sense after thorough study of the ME manual ( I recommend the Jeppesen multi engine manual) and everything else available via http://www.faasafety.gov . Only then a well trained/ educated/ proficient pilot can see the ” light” and realize that there are pros and cons to every flight. The PIC makes all the correct decisions, some are very quick ( loss of critical engine) some are made the day before the flight,some during pre- flight, before T/O, on T/O roll, climb …and so on. If we GA pilots study and practice the way US air carriers do, then we will see the fruits of safety coming our way.
      Don’ t take my word for it, ask your current instructor or the FAA inspector at your local FSDO, they will show you the way to becoming a safe aviator and not a statistic.
      Good luck !!!!

  • Derrick,

    The answer to your question involves several factors, including not least that US Airways Flight 1549 lost both engines more or less simultaneously, and didn’t lose one engine while the other one was making full power. So the issue in that accident was never loss of control, just loss of all engine power.

    Secondly, turbine engines when they fail generally present a much lower drag factor than propellers that are unfeathered … an unfeathered prop engine making no power induces a great deal of drag that must be overcome by the running engine, and exacerbates the asymmetric thrust issue.

    Thirdly, highly trained, ATP-certificated and experienced professional two-person aircrews undergoing regular recurrent training including sim training of engine out drills that operate a modern airliner are not equivalent to the typical single pilot private pilot at the controls of a typical light twin. The latter may well have just the required ME training, who knows what gets tested in a biennial review .. and most likely never gets recurrent sim training.

  • Procedure, procedure, procedure. If you fly multi-engines airplanes you MUST know the engine-out procedures intimately and be ready to put them to use IMMEDIATELY while remaining calm and focused. Don’t rush it, but be methodical. You have time, but not all the time in the world – only several seconds in most cases. One cannot allow himself to relax and become anywhere near complacent until one has a couple of thousand feet of air between himself and the ground in a twin-engine aircraft. Until you reach the altitude from where you can muddle things over a little bit and make decisions, you must know ahead of time what you will do IF _______ happens. One big question that must be answered before you push the power up for takeoff is: “Will this thing maintain sustained flight on one engine?” Many light twins will not continue to fly for any useful distances on one engine under even lightly loaded conditions; they were never required to do so. KNOW YOUR AIRPLANE’s PERFORMANCE NUMBERS.

  • Mr. Truitt
    I fully understand and aware of those points that you have stated with no argument. However I’m hard pressed to believe that both engines became inoperable at the exact same time. Also you have agreed with me as well as Mr. Sandidge that, no matter how much of the flight envelope are known, it still comes down to the proficient pilots at the yoke of the A/C. So, no matter if it’s a Twin / ME / single, there still has to be accountable operators at the controls and accountable operators to me, are will trained and practice often. And if someone thinks that’s an over statement, try doing a 75 ton pick and a gust of wind pops up with that load dangling 150ft agl, and not be proficient to counteract that movement of the load before that time ever shows up; Oh Boy !!! ( I’m a crane operator )

    • Derrick – Check out the NTSB accident report as posted online on the US Airways Flight 1549 accident. The evidence from CVR and FDR as well as pilot reports show that both engines lost power immediately and simultaneously … which is what can happen when an aircraft penetrates a large flock of very large birds.

      There is no substitute for a highly trained and alert pilot in a loss of engine accident … but “reality intrudes” and the typical private light aircraft single pilot is not the equivalent of an ATP-rated professional airline two person crew.

  • Chris, and everyone else that responed,

    Thanks !!!!!!! Everyone post was well received (even the ones that seem to disagree) because I received some very valuable info that will surely with my journey to utilizing all of the resources available to me to become the best pilot I can be. Which in turn will be indicative of being part of a small group of individuals that has the ability to do what the majority group don’t do, but do at a High Level of Skill which makes piloting an AC so Elite…
    Thanks again.
    May God Bless everyone!!!

  • I more or less quit flying when I was looking at 500 hrs in twins to get a commercial rating . I could not see risking my life to fly planes that are unsafe . I got my twin rating in a Duchess with counter rotating props which eliminates the critical engine and improves odds of surviving an engine failure . I lost access to the Duchess and the alternatives were not satisfactory ! I have also been sailing and fooling around with boats for years and counter rotating outboards are standard on twin set ups and the increased cost for the counter rotating outboard is peanuts . Suzuki now makes an outboard that will turn the prop in either direction at the push of a button. I blame the FAA for not approving technology that would make twins safer at a reasonable cost !

Leave a Reply

Your email address will not be published. Required fields are marked *