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Eleven killed in Polish skydiving plane accident

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  • #16
    Originally posted by brianw999 View Post
    FFS ! Why are we all arguing the toss about this ?

    12 people went up in a plane designed for 8. An engine failed and 12 people died.

    ......and all you can do is have an "I can piss higher up the wall than you" competition. Wake up, it ain't rocket science. I can give you 5 personal experiences of this happening in the past, either from engine failure or weight overloading or a combination of both.
    The thing is that:
    - The fact that 12 people climbed in an airplane designed for 8 (design that includes 8 seats, probably 6 of which were removed) doesn't necessarily mean that the plane was overweight.
    - An engine failure in this twin doesn't need to lead to an accident, since this plane has single-engine climb capability.
    - If the plane was overweight, very likely it was just "slightly" overweight (say 15%). That by itself shouldn't cause an accident. I don't know of any case where a slight overweight caused an accident by itself.

    Now:
    - Engine failures in twins have caused many fatal accidents, even with no overweight, mostly when the pilot was unable to keep the plane under control.
    - Slight overloads have caused accident, many times when the plane was operating at the limit of it's "non-overweight" performance to begin with (example: high and hot).
    - An engine failure and an overweight, even is slight, is a recipe for disaster, since this kind of light twins have a positive but slim single-engine performance even if not overweight.

    So yes, very likely an engine failure, an overweight, or both, were contributing factors in this accident. Still, the high fatality of this accident makes me thing that that alone is not enough. If an engine fails and you can't achieve a positive climb, then trade altitude for speed, keep the speed above Vmc (and preferably at the blue line) and land wherever you can. The result will be likely a survivable off-field landing. This case, instead, sounds like an out of control scenario, and you can't blame the engine failure alone, and even less the overweight, for that.

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
    --- Defend what you say with arguments, not by imposing your credentials ---

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    • #17
      Originally posted by 3WE View Post
      ...Indeed.

      And, yes...
      I am not arguing (see quote above)

      But I am pissing higher than Brian.

      Gabriel- I dunno...I can think of a lot of crashes from light planes that are heavily loaded. As usual- your comments are factually correct; however, I'm willing to bet a beer that "W/B" is a significant contributing factor- even if you factor for a light fuel load, missing seats and doors and use gross weight as the denominator.
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

      Comment


      • #18
        And I agree.

        I've said a slight overweight alone.

        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
        --- Defend what you say with arguments, not by imposing your credentials ---

        Comment


        • #19
          Aircraft was N11WB, a PA-31P Navajo.
          Pressurized version of the PA-31 Navajo, powered by two 425-hp (317-kW) Lycoming TIGO-541-E1A piston engines.

          General characteristics

          Crew: one or two
          Capacity: five to seven passengers

          Length: 32 ft 7½ in (9.94 m)
          Wingspan: 40 ft 8 in (12.40 m)
          Height: 13 ft 0 in (3.96 m)
          Wing area: 229 sq. ft (21.3 m²)
          Empty weight: 3,930 lb (1,782 kg)
          Max. takeoff weight: 6,500 lb (2,948 kg)
          Powerplant: 2 × Lycoming TIO-540-A air-cooled six-cylinder horizontally opposed piston engine, 310 hp (231 kW) each
          Propellers: Two or three blade, metal, fully feathering, Hartzell propeller
          Performance

          Never exceed speed: 236 knots[33] (438 km/h (272 mph))
          Maximum speed: 227 knots (420 km/h (260 mph)) at 15,000 ft (4,600 m)
          Cruise speed: 207 knots (383 km/h (238 mph)) econ cruise at 20,000 ft (6,100 m)
          Stall speed: 63.5 knots (118 km/h (73 mph)) flaps down
          Range: 1,011 nmi (1,875 km (1,165 mi))
          Service ceiling: 26,300 ft (8,015 m)
          Rate of climb: 1,445 ft/min (7.3 m/s)


          From reading posts on a skydiving forum site the main concerns seem to be an overloading problem combined with an out of limits aft CofG which would have a severe detrimental effect on one engined flight and rudder controllability. That last comment comes from 2 pilots who fly Navajo parachute planes.
          The one part of all this that horrifies me is that the occupants seemed to have survived the impact (this frequently happens in parachute planes where everyone is squeezed in tightly together) but then subsequently were burned alive. I've had to stand back and watch this helplessly on one occasion in my ambulance service life and I NEVER want to have to see or hear that again. That experience haunts me and was what prompted my last post.
          Last edited by brianw999; 2014-07-12, 08:40.
          If it 'ain't broken........ Don't try to mend it !

          Comment


          • #20
            Very sad.

            Comment though: Can we please be careful with the way we use words like overloaded.

            As has been pointed out, 12 people on a Navajo is not necessarily 'overloaded' (5 to 7 people in seats is a very different operation to a jump operation). It isn't necessarily 'overweight', nor is it necessarily 'outside the CofG limits'. It may be one or more of these things, but just because there are 12 people doesn't have to make it so.

            An engine failure in an aeroplane like a Navajo may not be successfully resolved well within its limits of performance. That is the nature of this sort of aircraft.

            This isn't regular public transport, and there are significant risks in jump operations no matter how careful you are. Jumpers should be aware of this.

            That doesn't change the fact it is always very sad when there is loss of life in an aircraft accident.

            Comment


            • #21
              Originally posted by MCM View Post
              Very sad.

              Comment though: Can we please be careful with the way we use words like overloaded.
              As has been pointed out, 12 people on a Navajo is not necessarily 'overloaded' (5 to 7 people in seats is a very different operation to a jump operation). It isn't necessarily 'overweight', nor is it necessarily 'outside the CofG limits'. It may be one or more of these things, but just because there are 12 people doesn't have to make it so.
              No, It doesn't "necessarily" mean those things..... But there is a "high likelihood" of one or more of them contributing to this crash. Aft C of G movement for instance is a "high likelihood" when you consider that in a normal Navajo the seating ends forward of the exit door. In a jump plane there is almost always 3 to 5 jumpers in the area of the exit door so the C of G is going to move aft. As an example.... I was assisting in the loading of a six seater Piper Twin Comanche medevac flight. The patient was on a stretcher and three of us were loading him when the aircraft suddenly sat back on the tail. This happened because although there were only four of the certified six passengers on board we were too close to the rear and the C of G went out of limits aft.

              An engine failure in an aeroplane like a Navajo may not be successfully resolved well within its limits of performance. That is the nature of this sort of aircraft.
              Yes, especially if the C of G is very close to or out of limits. In such cases it is often said that, in the event of an engine failure the good engine will succeed in taking you to the site of your crash.

              This isn't regular public transport, and there are significant risks in jump operations no matter how careful you are. Jumpers should be aware of this.
              Oh so very true....which is why operations should have a extra degree of safety planning and why even more attention should be given to operating within safe limits.

              That doesn't change the fact it is always very sad when there is loss of life in an aircraft accident.
              The saddest part of all this, especially when you consider that adequate planning for the event of engine out operations might possibly have avoided these deaths.

              Let us remember those who lost their lives in such a horrible way. RIP.
              If it 'ain't broken........ Don't try to mend it !

              Comment


              • #22
                Brian, there is a mismatch between the airplane type and the general characteristics.

                As you said, the plane was a PA-31P, which is a pressurized, 2 x 425HP engines Piper Navajo.

                That means that the general characteristics that you and I gave are wrong. (including the 310HP engines in your list )

                The PA-31P has higher: power, empty load, MTOW, and speeds (stall, Vmc, etc...).

                Piper PA31 P Press Navajo

                Horsepower: 2 x 425 HP
                Top Speed: 243 kts
                Cruise Speed: 220 kts
                Stall Speed (dirty): 73 kts

                Gross Weight: 7800 lbs
                Empty Weight: 5004 lbs
                Fuel Capacity: 192 gal
                Range: 690 nm

                Takeoff
                Ground Roll: 1440 ft
                Over 50 ft obstacle: 2200 ft

                Rate Of Climb: 1740 fpm
                Rate of Climb (One Engine): 240 fpm
                Ceiling: 29000 ft
                Ceiling (One Engine): 12100 ft

                Landing
                Ground Roll 1370 ft
                Over 50 ft obstacle: 2700 ft

                With that data, we can see that the useful load is 2796 lb, about 200 lb more than the 2570 lb of the "normal" Navajo that I (and Brian) posted earlier, which makes an overweight a bit less unlikely or a bit less "intense".

                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                --- Defend what you say with arguments, not by imposing your credentials ---

                Comment


                • #23
                  On July 5, 2014, at 1605 local time, a Piper PA-31P airplane, United States registered N11WB, was destroyed when it impacted terrain after takeoff near Czestochowa, Poland. Visual meteoro...

                  According to statements of a representative of the Polish AAIB (PKBWL), the plane hit the ground in near vertical dive and 70-80 degrees left bank with left-hand engine non operating. The plane had a history of engine problems.
                  This makes any overweight and CG issue almost irrelevant. The pilot lost control of the plane after an engine failure. Yes, overweight has a strong impact on the single-engine climb performance (where the plane is barely able to climb when NOT overweight).

                  If the plane had crashed (or crash-landed) after not being able to sustain a climb, then overweight would be an important factor. But losing control after an engine failure is a pilot thing. If the plane remains above Vmc, there is enough control available. If the pilot can't achieve a climb at Vy(ef) (the best-climb speed with one engine failed), then he MUST accept a descent, but must never keep pulling up to get an impossible climb. The pilot must even consider reducing power on the GOOD engine to keep control. An engine failure in a twin SHOULD NEVER be more serious than in a single. If you can't handle any asymmetric thrust, then kill the good engine too.

                  Oh, and by the way, it's hard for me to understand how an aft CG could affect the single-engine controlability so badly. Yes, the arm between the rudder and the CG is reduced, but by how much? It's a couple of inches in many many inches. It's very different than the pitch stability where the wing, which is BIG and very close to the CG, is a major contributor. There a few inches can make a lot of difference.

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

                  Comment


                  • #24
                    Gabriel- I don't understand what you don't understand.

                    A loss of control from an engine failure should not happen but so often does. There's that famous stat that light twins have a higher engine failure fatality rate than singles.

                    Heavy and aft cg should not matter but it does... It's harder to maintain altitude and then when you loose it the aft cg can makes it that much easier to stall and harder to recover.

                    And dang it I tried some engine out stuff in msfs.... This thing isn't climbing but I'm watching airspeed... I think I'm watching airspeed oh shit stall spin crash burn... It happens and happens quick and it happens to good pilots and be stats say it happens a lot.

                    Yeah follow the procedure - speed is life - feather the prop but lower the nose and power back if need be run the memory checklist blah blah blah. Easy for us to say, but probably a lot trickier to do for real.
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                    • #25
                      By the way:

                      A de Havilland Canada DHC-6 Twin Otter 100 plane, registered N203E, was damaged beyond repair in an accident at Sullivan Regional Airport, MO, United States of America. There were seven passengers and one pilot on board. The airplane operated on a local flight out of Sullivan Regional Airport, MO ().
                      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                      Comment


                      • #26
                        Originally posted by 3WE View Post
                        Gabriel- I don't understand what you don't understand.
                        I don't understand what you think that I don't understand. I fully agree with your post and I don't think that I have said anything contrary to it. Rather, I think we are saying very much the same thing.

                        A loss of control from an engine failure should not happen but so often does. There's that famous stat that light twins have a higher engine failure fatality rate than singles.
                        Exactly. It's, like I've said, a "pilot thing".

                        Heavy and aft cg should not matter but it does... It's harder to maintain altitude and then when you loose it the aft cg can makes it that much easier to stall and harder to recover.
                        Ok, so now you are considering heavy AND aft CG simultaneously, not to mention the engine failure AND the pilot failure for not being able to keep control and to take off out of W&B to begin with.

                        Yes, heavy makes it difficult or impossible to maintain altitude, but not more difficult to maintain airspeed. An aft CG doesn't make it much easier to stall. Yes, it's a bit easier because less force is needed for a given change of AoA. Anyhow, stall is not the real problem here. Yes, it would be a huge problem, but you are in big shit much earlier. Go below Vmc (which is above Vs) and you'll see how the "no stall no spin" can be violated (ok, it's not the same kind of spin). About recovery, stall a twin with an engine died and the other one at full power and recovery will be impossible no matter the CG, unless you have A LOT of altitude and a spare brain of a different brand than the one that put you in this situation to begin with.

                        And dang it I tried some engine out stuff in msfs.... This thing isn't climbing but I'm watching airspeed... I think I'm watching airspeed oh shit stall spin crash burn... It happens and happens quick and it happens to good pilots and be stats say it happens a lot.

                        Yeah follow the procedure - speed is life - feather the prop but lower the nose and power back if need be run the memory checklist blah blah blah. Easy for us to say, but probably a lot trickier to do for real.
                        I never said or intended to say that it was easy. It is not. But you must demonstrate it to pass your multi checkride.

                        An important reason why engine failures in twins cause more deaths than in singles, is because twins have 2 engines and hence the have an engine failure twice as often (per airframe x hour). And while we've heard too often of mishandled engine failures where the pilot loses control, we never hear of the ones where the pilot manages to land on or off airport, which I am convinced are at least one order of magnitude more frequent than the loss-of-control crashes.

                        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                        --- Defend what you say with arguments, not by imposing your credentials ---

                        Comment


                        • #27
                          Ok Gabe- it's just that these sentences are very strongly worded when single engine twins spinning in is unfortunately not rare.

                          Yes, you go on to list disclaimers but those statements stand out.


                          Originally posted by Gabriel View Post
                          This makes any overweight and CG issue almost irrelevant.

                          An engine failure in a twin SHOULD NEVER be more serious than in a single.

                          Oh, and by the way, it's hard for me to understand how an aft CG could affect the single-engine controlability so badly.
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                          Comment


                          • #28
                            Originally posted by Gabriel View Post
                            But you must demonstrate it to pass your multi check ride.
                            Just like we have to be able to fly headings and altitudes and recover from unusual attitudes solely by reference to instruments to pass your ppl (yes ppl) check ride.

                            Then you have to do it again to pass your ifr check ride...
                            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                            Comment


                            • #29
                              Originally posted by 3WE View Post
                              Ok Gabe- it's just that these sentences are very strongly worded when single engine twins spinning in is unfortunately not rare.

                              Yes, you go on to list disclaimers but those statements stand out.
                              That's why "almost", "should" and "so badly".

                              You know what they say. Absolute sentences are almost always wrong (except that you can't use energy through the disk as denominator ).

                              But I see your point, so let me explain myself, again:

                              This makes any overweight and CG issue almost irrelevant.
                              Overweight is relevant for climb performance, especially single-engine climb (in a twin I mean). But not "directly" linked with loss of control during single-engine flight... unless... unless the pilot tries to sustain a climb which is unsustainable due to the overweight. Then he WILL lose speed and, eventually control. Indirectly, the overweight would be a factor, linked by the pilot's mishandling. And the CG? Later.

                              An engine failure in a twin SHOULD NEVER be more serious than in a single.
                              ... if the pilot does what he SHOULD do.

                              As you've said, pilots not doing what they should do is a major link in the chain of events in most accidents, not just loss of control in engine failures in twins. You mentioned flying solely by reference to instruments. But we could also mention, more linked to this accident, pilots that stall-spin-crash-burn-die in singles, sometimes after an engine failure, sometimes even when their only engine failed. So the event of this thread would fall in this same category of accidents.

                              it's hard for me to understand how an aft CG could affect the single-engine controlability so badly.
                              Here the key is the "so badly". An aft CG WILL affect the controlability in single-engine flight in a twin.

                              The pitch stability and control authority will be affected most, but here the engine failure is not really relevant.

                              The directional stability and control authority is affected little (because the distance between the CG and the tail will be only a few inches shorter in an arm that is a lot of inches long). And, not many know this, but the control authority in non-accelerated flight is not affected. Meaning that to hold the plane with no sideslip while flying at constant heading and speed you need the same amount of rudder regardless of whether the CG is at its forward or aft limit, or anywhere between or slightly outside. The difference will exist in the dynamic response of the plane where the restoring moment, and the damping moment will be smaller. But not that much.

                              In short, while there there is an effect, I don't think that a pilot would be able to note the difference.

                              In short, this pilot probably screwed it up. Like many other pilots did in the past and, unfortunately, many pilots will do in the future.

                              And while weight and balance was not, in my opinion, an important factor in how the accident developed (loss of control), if the plane was overloaded or out of CG, the pilot screwed it up too.

                              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                              --- Defend what you say with arguments, not by imposing your credentials ---

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                              • #30
                                Originally posted by Gabriel View Post
                                Here the key is the "so badly". An aft CG WILL affect the controlability in single-engine flight in a twin.
                                ??????????????????

                                See bold font.

                                Technically it probably doesn't "so badly"

                                But it generally makes stall behavior more nasty.

                                And add in asymmetric thrust and that it's not a Cessna 150 and you have an unfriendly spin machine.

                                The chain of events is so tightly linked that your paragraphs of the hell better aeroengineering are kind of moot. Technically cg does not greatly impact rudder authority but spins can follow stalls especially with single engine twins and cg can mess up stall behavior and it can all wind up in sequence VERY quickly.

                                If it didn't matter so much then why have RJ hosties and J-31 crews made me change seats?
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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