EXIT A SPIRAL DIVE

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LARRY TEACHES HOW TO GET OUT OF A SPIRAL DIVE IN A TRIKE.

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59 Comments

  • Rizwan Bukhari
    by Rizwan Bukhari 5 years ago
    Awesome, Awesome and Awesome
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Yup 3 secs to end the whole 2000 fpm ordeal if you do this right or push out, hit the throttle and cork screw into the ground and higher and higher speed. Biggest caution is unload the wing and keep it pulled in and very slowly let it out or you can exceed maneuvering loads
    BTW, should note that only well tuned wings will not worsen in 60 degrees bank and 1400 fpm descent. Most run of the mill wings will tighten up slowly if let go at this attitude
  • Tony  Castillo
    by Tony Castillo 5 years ago
    Great video Larry & Wes. Thanks for posting.
    TC
  • Jan Ferreira
    by Jan Ferreira 5 years ago
    by Wesley Frey 3 days ago F B C. Wait a while then allow A
  • Paul Hamilton
    by Paul Hamilton 5 years ago
    Wes, Thanks for helping Larry put this together.
    Larry, Thanks for providing your definition of what a spiral dive is. For this wing/trike, looks like a stabilized steep turn 60+ with no throttle.
    Glad your detailed description and demonstration is the same as mine. :) Reduce the angle of attack and roll out of the turn simultaneously and control your speed to ease out of the dive to minimize stress on the aircraft

    Nicely done and a help to all trike pilots.
  • John Young
    by John Young 5 years ago
    Quote "Fly as I tell you - not as I do" - Larry Mednick 2012

    Thanks Larry and Wes.
  • Dane HAUSER (www.sky-surfing.com)
    Great video Larry! I appreciate the caution/explanation you gave at the end of the video. When new students come to the flight school it's common for some to request I teach them many of the maneuvers in your videos (some I do, some I don't). Not all students understand how elite of a trike pilot you are and mistake some of the maneuvers as normal trike flying. This is one I will be happy to work on with students. Thanks! Dane

    www.sky-surfing.com
  • Douglas Donaldson
    by Douglas Donaldson 5 years ago
    Abid - how do we groom our "run of the mill" wings to become "well tuned"? I assume you are talking about more than tuning out a simple turn at cruise.

    Do you have a simple, safe test pilots can use to see if a wing is "well tuned"? - I mean other than flying you or Larry out to see us ;-)

    I would like to read more about this.
  • Paul Hamilton
    by Paul Hamilton 5 years ago
    I will say that Wes and Larry did a better job with the spiral dive recovery details than I did, but what happened to the “maneuver police force” for the spiral dive?
  • david coy
    by david coy 5 years ago
    larry i would like to thank you now i finally saw the video. verry informitive and educational renews my faith that trikes are quite stable and there must have been more going on in resent crashes and its really good the way you put this out there for demonstrational perpose with caution flag at the end. the average good day flyer should not get into this position easily but its good to be clear on how to get out of it.i also apreciate the fact that you made mention of the brs. ive talked to a lot of pilots who say theres no need for one but i think that a brs could of saved a few of these resent crashes .once again bravo on the non abiguious vidio with respect thanks
  • Captain X
    by Captain X 5 years ago
    Larry, I fully agree with the compliments David Coy and others gave you and Wes.
    Thank you and take care!!
  • david coy
    by david coy 5 years ago
    i was wondering if you could maybe talk a bit how maybe turbulant high winds rotor wind shear or down drafts and gust fronts might effect the result of the spiral or down wind turn in these conditions . what would be the result.maybe some info on that if you would be so kind ty
  • david coy
    by david coy 5 years ago
    or if power setting remained full on in spiral ty
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Hi Doug D:
    By messing with the wing hour after hour for some time and flying :)
    Really that's what it takes. New wings, no matter if tuned from the factory will always behave different after transport, different climate, after a few hours of flight and sail setting in. So unless the factory pilots fly them for 10 hours, they are not going to be tuned properly because the sail will set in about 10 to 20 hours. Nothing anyone is going to do about that. It's the nature of the beast.

    But there are some guidelines.
    No turns at trim are a good start.
    Positive pitch pressure seeking within 10% of trim speed from 1.1 Vso to Vne at increments of 5 mph test.
    No nasty breaks/roll to one side at stall. That always sucks and can be a bunch of things including the worse, tip stalling. If so the wing would be a handful in mild turbulence
    But try no turns at 1.1 Vso to 0.9 Vne in calm conditions at idle
    Also try above with power keeping S&L
    Try power off turning stalls at 30 degrees (start at 15 degrees and increase bank angle in increments of 5 deg). Is it predictable and easy to correct in rolling level or dos it feel like it wants to rollover?
    Try 45 degree bank flight at idle. At idle, the wing should hold its bank angle through 720 degrees both left and right.
    No huge sail flapping from Vso to Vne.
    No weird out of control tendency in rolling in rapid succession left to right and back at cruise power and idle at 1.3 Vso to Va. Start at 30 degrees bank angle roll and increase to 60 degrees bank angle roll for this in increments of 5 degrees.

    Then it's personal preferences as well. I don't like wings hat are too loose or ones hat make me feel like I didn't go to the gym the whole last year. One creates gaps in feedback loop in all configuration and one is just outright retarded and take the sport out of sport pilot. But that's just my personal opinion.
  • Ken Nussear
    by Ken Nussear 5 years ago
    Thanks for posting this Wes and Larry. One difference I note is that in the spiral dive question posed earlier you were in the spiral dive at cruize throttle. Do you recommend droppin throttle in that case?
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    Larry thanks for the freebie lesson. If I had a passenger and was close to max weight I think I would pull my BRS instead of chancing a component failure. Still floors me how people still do this intentionally. I had answered incorrectly. I said idle,push bar right, then pull in. Something to discus with my trike buddies. I like to learn by watching, I always find it interesting how you relax your left pinky finger on the bar(except in this case) when maneuvering. Just noticing quite some time ago in your some of your previous videos, has made me relax my hands deliberately which has made my controlling smoother and more fluid.
  • Douglas Donaldson
    by Douglas Donaldson 5 years ago
    Abid - Thanks! That's a great list. It seems like a reasonable evaluation program every few years or several hundred hours (if the wing is good) or a source of endless frustration (if the wing was born bad).
  • Captain X
    by Captain X 5 years ago
    Brian what if a component on the BRS failed on it's "test flight?"
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Brian: pulling BRS is much more dangerous than doing this simple few seconds recovery. Just pull in and roll level almost simultaneously and then you are just in a S&L dive and recover from that like you always do. Smoothly and deliberately. No abrupt moves. That is it. I would never pull BRS for this. It is a non-event if you follow these steps and it's over in 3 seconds
  • Dane HAUSER (www.sky-surfing.com)
    I absolutely agree. Pulling BRS is a last resort and would be much worse than just properly exiting a spiral dive. I practiced a few of these with a student this morning and it's interesting how their natural reaction is to push out on the bar. It seems irrational to pull in which is why I'm sure many pilots have fought it all the way to the ground. Larry does a great job of demonstrating the proper technique.
  • Larry  Mednick
    by Larry Mednick 5 years ago
    ..."Where is the video of the cruise speed and power spiral dive recovery? Pushed out at idle changes
    the answer. No need to pull in for speed if you already have it just roll out."

    Unfurtunately power-on in a spiral dive would make the video quite short. It would only take maybe 1/4 rotation before VNE maybe a half rotation... The purpose of the power-on scenario I posted was to make sure everyone knows to immediately take their foot off the gas pedal in a spiral dive (or get to the hand throttle quickly).

    I think to understand what is happening in a spiral dive is simple. The trike is CLIMBING! The trike is climbing towards the ground. What are things that increase a trikes climb?

    The spiral in the video was high G, high speed, coordinated flight, at least in the sense that the airflow over the wing was front to back even at 2:17 into the video. Sure the trike was nearly sideways falling like a rock, but it was indicating 102 MPH which by the design of my pitot tube means I had at least 102 MPH of relative wind coming head on. It has been my experience that I have never been able to slip any trike for more than just a few seconds. The very slip itself IS what coordinates a trike. Some trikes coordinate quicker when slipped and some track better, but like a weathervane it always points into the wind except for a second or two when the wind shifts rapidly. But thinking of a slip in a trike is similar to wind blowing sideways across a weathervane...

    So what is a death spiral to me? well... it's kind of like a PIO. it's when the pilot is creating the problem and not able to pilot the trike to the desired attitude. This would be one reason they might be exceeding the trike's limitations. there are only 2 things I am aware of to worry about in a spiral. 1) breaking the wing 2) the ground stopping your descent. Like many have said, "if you are flying within the limitations of the aircraft and you know how to stop the descent do it all you want..."

    Now the big question WHY???? pull the bar in and not just level the wings. I will be the first to admit that just leveling the wings will work in most cases even if the roll pressure is increased as others have noted. But also why is the roll pressure increase and why would you pull in. Does pulling in make the trike accelerate or speed up when the wings are leveled almost simultaneously?

    Remember the trike is climbing (sideways) the wing is producing more lift than needed in S+L flight.

    Can the wing stall in the spiral or could a stall have started the spiral? do booth wings stay stalled or just one? and if one which one? would moving the bar to the right work if the right wing was stalled?
  • Ted  Bailey
    by Ted Bailey 5 years ago
    I understand on the power, only mentioned it for clarity of my answer. If you have excess lift that wouldn't be from a stalled wing. Both sides are flying only the outside wing is producing more lift. Excess lift/energy and what to do with it has never been my problem. You can trade it for speed or altitude or roll 120 to the opposite rotation direction or just mush it off in a crazy ivan.
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    I figured that doing this maneuver would exceed my trike tolerances. I do have a 500 hr AC Ixess wing, it is a good wing. Even after all of this input I was still thinking it had a good chance of breaking. I still have a lot to learn.
  • Captain X
    by Captain X 5 years ago
    Well maintained, as all wings should be, I'd have no concerns in your iXess Brian. Great wing, great tendencies. Can spiral dive and recover without any problems. Very strong. As I've said many times, personally, I trust the light triangulated brute strength of a king-posted wing much more. Get the training, careful practice with an instructor, trust the wing and PIC the airplane through the sky and back home-- don't give up and become a passenger letting the plane take you where it may. BRS lets you become a passenger when there's no other choice of vehicle to pilot ; )
  • Flying  Frog
    by Flying Frog 5 years ago
    Brian, your wing can do this no problem. The ixess is very docile in a spiral dive and and has been tested to 6g, You will feel the G force as you exit, but it is no where near as much as 6g. I have done this many times with the ixess and the Bionix.
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    Thanks for the reassurances about my wing type. I guess overall this Spiral dive thing has me a bit unnerved. I havent done it and was taught to avoid getting into one. I tend to be a bit cautious about entering maneuvers that are advanced as this is. To be able to read and see how to manage it is to my benefit.
  • George B
    by George B 5 years ago
    Unussual attitude training with a good instructor is valuable for any pilot. You may not plan on getting in a steep decending turn (spiral dive) but there is nothing like hands on practical experience to feel and understand these flight dynamics. Once you are comfortable with this kind of recovery you can fly with greater confidence and not fearing the "unknown" parameters. This kind of training would certainly help in making the right BRS choise, both in when to deploy and when not to deploy, should such a situation arise. We all need good training and good instructors! The hours are long, the risk is high, and the pay is low : /
  • Dave Dodson
    by Dave Dodson 5 years ago
    Larry: Just your statement on how the trike is 'climbing' to the ground while in a spiral dive explained most of what you performed in the video to me. I admire the knowledge I read in these posts and everyones opinion and thoughts, but some just go over my rookie head.
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    My instructor Tracy doesn't know it yet but he's gonna get a phone call asking him for some " unusual flight attitude" training. I hope he doesn't include a extra hazard fee, wouldn't blame him if he did.
  • George B
    by George B 5 years ago
    That's great Brian. I hope you will enjoy the training and give us an update on how it goes.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Brian: That's great. I am sure Tracy will explain the actions required to get of this type of spiral dive quite easily and clearly. Remember, this spiral dive can happen in airplanes as well and you are guaranteed to fly the wings right off of any airplane if you decide to continue the spiral dive. This is not a spin either. This is something like a Cessna 152 after one turn spin and the resulting spiral dive in recovery. If you just continue that spiral dive, the wings will come off. Its not just a trike thing. Airplane curriculums have a full lesson about it. Airplane Flying Handbook talks about it but its not very accurate about recovery actions as it does not emphasize that it will be necessary to keep the stick or yoke pushed forward (lower nose) during recovery with pilot pressure. Allowing the pitch up suddenly can take the loads during recovery much higher than allowed 3.8 G's in an airplane as well. The first step they also teach in airplane spiral dive recovery just like trike is to close the throttle (go to idle).

    The biggest recognition that you are in a spiral dive versus a spin (btw, trikes are next to impossible to sustain a spin in, unless you constantly un-coordinate them by constant pilot action)
    1) Airspeed keeps increasing in a spiral dive going towards and past Vne. In a spin rate of increase of airspeed is very low and goes up and down
    2) G load keeps increasing in this type of a spiral dive. G-load does not increase in a spin. Increase in load factor also behaves to enhance what is perceived as lockout on controls in WSC and unloading is required to make it easier to level the wings
    3) Altitude is decreasing at higher and higher rate in this type of a spiral dive.

    Here are some example lesson plan materials from airplane guys about spiral dive recognition and recovery and that you can discuss with Tracy
    http://www.mpaviation.com/lessn10.htm

    http://www.langleyflyingschool.com/Pages/Spiral.html

    Here is another explanation from airplane guys. Just replace "PULLING" with "PUSHING" for trikes. The Physics and aerodynamics don't change much between trikes or airplanes.
    http://www.youtube.com/watch?v=ySHDicIlpqA
    Notice the words at around 5 minutes: "when you increase G load, you actually decrease your roll performance" (aka perceived lockout and hence the idea of unloading or pulling in on a control bar while rolling level works best every time, all the time)

    LOADING IN A TRIKE = pushing forward on control bar
    UNLOADING IN A TRIKE = pulling in on the control bar

    This is all standard run of the mill stuff if you understand what is happening in a turn, what happens in a rapid pull up, what effect application of power has at different attitudes and your aircraft due to its stability is always seeking trim AOA, not trim speed. Once you understand all of these then the scenario is simply a combination of these and recovery technique makes perfect sense knowing what the effect of all these factors is. Don't get caught in the "trike wings have billow shift" trap. Billow shift in a turn just helps roll, it doesn't create or even is the most significant factor in establishing a turn in flexwings.
    Just understand it all sounds much more difficult than it actually is. Its the understanding of what is going on and why do you have to do the things in the way you do them that's difficult not the actual actions in recovery. It is dead simple and easy and quick once you understand and do what is needed to be done which I agree is counter intuitive.
    Remember the best way to avoid getting into spiral dive of this sort is to not allow the nose to drop while initiating a steep turn or in a large roll upset due to weather, and that is done by pushing out the bar while entering and establishing bank. Lazy steep turns are what can initiate a spiral dive and can develop rapidly but even there the recovery should be a non-event if you know what you are doing.
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    Abid, thanks for the links and input. In my wing it takes a bit manhandling in real rough air. Tracy thinks Larry might be using his new small wing which is amazing for maneuvering. My wing will be significantly different when it comes to the pilots inputs on the control bar. I'll be putting the instructor bars and throttle on later this week for a lesson with Tracy. I've always been to avoid getting myself into this type of situation. I'm guessing the post I put up after the lesson will be revealing of my skill set.
  • Larry  Mednick
    by Larry Mednick 5 years ago
    One more thing... There is an added factor for trikes above and beyond fixed wings regarding G loading I don't see mentioned here yet.

    When a trike is pulling G's like it was in the video the wing tips wash out or twist up more due to the leading edges flexing under load. This in itself causes a pitch up motion which tighens the spiral when banked and also causes the trike to want to climb when the wings are leveled out. Until the G load is reduced the trike wants to climb. Pullng in the control bar helps compensate for the wings CL (center of lift) being further forward due to the increased washout.
  • Ted  Bailey
    by Ted Bailey 5 years ago
    The small amount of added washout in this load situation would only change the hands off bar trim position. The positive pitching caused by the washout mostly comes into play if the wing is stalling. The spiral dive is not a stall, the dive is the speed/gee producer. You suggest pulling in because the trike wants to climb, that is good but just one possible scenario. I would be interested is any real life documentation of a spiral dive folding a flex wing. Too many flex wing pilots have been doing this manuever for decades to not have a statical base to study.
    Another trike Straw Boogy-man?
  • Mike-in- Thailand
    by Mike-in- Thailand 5 years ago
    Great stuff Larry, many thanks for making this film; I found it very informative.
  • monty stone
    by monty stone 5 years ago
    wow! i need to read all this over and over! lots of info here. i won't intentionally enter a steep spiral, (most of my triking is at fairly low altitude) and recovery time would be absent, but learning what is happening, and why, plus how to remedy the situation is invaluable! thanks larry et al.
  • Joe Hockman
    by Joe Hockman 5 years ago
    Larry, very informative and thanks for posting. Speaking of pulling some Gs I thought I'd share an important consideration. Not every one can handle the Gs well. I have done quite a few spiral dives to loose altitude quickly but a few years ago I must have pulled one too tight and blacked out momentarily which scared the crap out of me. I have low blood pressure and clearly I was not getting enough blood flow to my brain. Reason I would not go on an agressive roller coaster ride wide with my kids. Clearly during a momentary blackout one is incapable of providing correct inputs to pull out of a spiral dive. I often wonder if this in combination with the some what anti-intuitive and incorrect thought that pitch up will help to exit that dive (but only makes a tighter spiral with higher Gs) may have been involved with some recent accidents for pilots that had very little prior exposure/experience with spiral dives. Don't know but it could be a possibility. Final thought, not only is there considerable individual to individual variability in blood pressure and tolerance for higher G maneauvers but there is also considerable dynamic variability (ie what a pilot may have been able to tolerate yesterday may not be what they can tolerate today which is dependent on many variables).
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    Joe, thanks for the comment. There are circumstances and conditions that far too many pilots do take into consideration.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Yeah what Larry mentions is generally termed as G due to G in trike wing/flex wing designers but to some this whole idea of G loading on aeroelastic delta wing structures generating more G's is not sold. This is significant on aeroelastic structures and less significant on more rigid wings. We had a long debate about this G due to G thing on some forum and some just did not/do not get it or buy it. But if you talk to people like Bill Brooks etc. they know exactly what that term means and what it implies.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    I don't know what is documented Ted but there are accident investigation in the UK, one at least with a Raven wing which the fatal accident resulted from locked spiral. There is a Streak-III Airborne accident investigation report by ATSB that ended in a fatality due to a spiral to the ground. There are some mysterious NJ accidents 7 years ago or so in NJ (one after running into the wake of a twin rotor large helicopter in very calm conditions resulting into a spiral all the way to the ground) but they were during the UL era and no official full investigation was done but that's my take on them anyway.

    This is just off the top of my head, I am sure there are others.
  • Paul Hamilton
    by Paul Hamilton 5 years ago
    Greta discussion everyone. Eventually, I am going to summarize and put this together in an aerodynamics and flight training package so nothing here will be lost. Appreciate all input/opinions. Thanks.
  • Ted  Bailey
    by Ted Bailey 5 years ago
    I remember the G due to G but this was only a possible factor @ extreme loads (3G+)not generally reached or exceeded in normal flight. I have never seen 3 gee in a spiral dive but agree with Joe on everyones personal limit to what their body can take g wise and not black out. Maybe that is a case for having the flight medical?Still sounds like a control problem, unless you are suggesting a design problem with certain wings? I was more curious of recorded structural failure resulting from a spiral
    dive. Unless caused by an abrupt manuever I have never heard of a wing failure in a positive load even if exceeding vne. I have no doubt pilot error has caused fatalities
    related to spiral dives. Great reason to include this in flight training, with training this should be like flying thru your own wake, a non-event.
  • Joe Hockman
    by Joe Hockman 5 years ago
    Not sure I believe in a locked spiral due to the wing being locked there and a pilot not being able to come out of it. My suspicion is that spiral dives to the ground are likely due to 1) PIC froze and locked their arms, 2) PIC provided incorrect inputs to the wing with insufficient altitude to correct, 3) spiral was some how exacerbated by turbulence, sink, shear, etc to an atitude that could not be corrected in time at low altitude, or 4) PIC became incapacitated due to black out or some other medical condition. I too have never heard of a wing coming apart in a spiral even when VNE is exceeded. Primary point I was attempting to make in earlier post is that all synapses must be firing correctly in order for PIC to come out of a spiral dive and that may not always be the case under higher G loads of tight spirals.
  • Adam Romanowicz
    by Adam Romanowicz 5 years ago
    Thanks for the educational discussion! For a low-hour pilot like myself these videos and discussions are invaluable. This is something I've put on the list to practice with my instructor.
  • Brian Reynolds
    by Brian Reynolds 5 years ago
    Adam I know it is a huge discussion to read but others do describe the circumstances that can cause this type of situation. Any turn that puts one of your wings into a stall ( such as a turn when you are close to stall speed, or a turn that causes your wing to stall such as a very steep bank 60 degrees. Most of us are taught to avoid these situations however to someone unprepared it can develop into a spiral dive that they dont know how to get out of.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Ted: The G due to G is not during a spiral but something that can and will tend to happen during recovery. I hope everyone understands that this spiral is one way which guarantees a trike will go past VNe and do so rather quickly. Regardless of your trike's pitch stability or if you could not take it to VNe with a pulled in dive, this spiral will get you there are past it pretty easily.

    When you go past VNe and then you get out of the spiral and recover, the trike will have a pretty good pressure to try and pitch up. That pitch up if not controlled will create G's and thus G due to G could result.

    Theoretically, if you are at 100 mph in the dive and pull up quick and your Vso is 40 mph, the load factor or G's you can develop instantaneously (for a fraction of a second) are
    100^2 / 40^2 = 10000/1600 = 6.25 G's

    Some trikes today will go to 120 mph rather easily in this spiral. Revo can go a good 130+ mph in such a situation within seconds. Airplanes will go way past their VNe's.

    The bigger the speed range, the bigger the potential G load factor. Nothing in aviation is free. There are plus and negatives to efficiency and increasing speed range as well.

    This potential theoretical G load and G due to G can certainly get you to the place where the wing will break off if pilot technique is bogus, not smooth and sloppy. Fortunately, this is a very unlikely situation to happen. People do spirals every day in trikes w/o knowing any of this and come out just fine. But if factor after factor gets piled up, it is possible to break the wing.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Well Joe :). Just because you "don't believe" it doesn't mean it doesn't actually happen. Although you are right in all seriousness, that the right pilot actions will allow recovery. Its never truly "locked" unless pilot does not know how to recover and follows intuitive actions. If you do recovery properly you will not perceive a complete lockout. If you do it incorrectly at a certain point you will perceive practically a lockout.

    This is from an ATSB spiral dive investigation report from 1995 (released 1996) for an Airborne Edge trike

    "The test pilot reported that discussions he had with experienced pilots indicated that the spiral dive was not a widely recognized condition among Trike pilots. If a wing drop at the stall was not corrected early, recovery from the spiral dive to normal flight could result in an altitude loss of up to 90 m. The recognition of, and recovery from, a spiral dive was not included in the Trike Pilot Training Syllabus. It was suggested that such training be included in the syllabus.
    The test pilot considered that the accident aircraft may have stalled and entered a spiral dive. A reflex action of the pilot may have been to attempt to raise the nose of the aircraft to recover from the dive. However, although this would have involved very high control forces, such an action by the pilot would have maintained the wing in a stalled condition, causing the spiral to continue."

    Similarly, I'll give you some links of just 3 fatal accidents in Australia on Airborne trikes where in spiral dives the wings LE broke in high G's encountered during an uncontrolled spiral dive.

    http://www.recreationalflying.com/threads/atsb-review-of-trike-accidents.1047/
    ATSB material review reports for these accidents:
    http://www.atsb.gov.au/media/24315/aair200601173_001.pdf

    There are other examples as well in the UK and in France etc. but this should illustrate the point sufficiently I think.
  • Tony  Castillo
    by Tony Castillo 5 years ago
    I think the key is to watch and control speed very carefully. If speed is increasing rapidly, recover soon.
    tc
  • Paul Hamilton
    by Paul Hamilton 5 years ago
    Roger that Tony. Speed is everything. Vs, Vy, Va, Vne. Most of my day at the office teaching students to fly is controlling speed to stay alive.
  • Ted  Bailey
    by Ted Bailey 5 years ago
    G due to G not a factor! except maybe under higher (much!) than normal flight loads. If your diving (unloading) where is the g load? (6 G worth of drag?) You get G from the turn or the recovery. So what forces would fold/fail the wing?

    What trike wing has folded from just exceding vne? None...? it is the recovery or pull out or up depending on pilot. I have been @ vne in spiral dive for long desents and never had it accelerate uncontrolled, always rolls right out when its suppose to. This must be a safety concern for the newest gen. trikes/wings.(trade off for 100mph?)

    Here is a real life set of numbers 80^2/55^2=6400/3025= 2.1157 G to do a loop using your math well under the designed positive load. (feels like 2.5 G, probably is with a safety factor) Sometimes you can just over think this stuff vne is not as finite
    in flexwings. A trike wing is overbuilt by a large factor when compared to HG wings.
    I can take a HG wing to ~twice the vne in a verticle dive and then suddenly pull up and into a loop(46 vne 85 in dive, 3.5 G) easy! In a trike I have to work hard to exceed vne by 10-12%. Both are rated for 6 G that makes most trike wings very strong. Maybe that why there are few if any wing failures under positive load in flight.

    I agree about ham handed pilots but training and practice are a sure cure.
  • Ted  Bailey
    by Ted Bailey 5 years ago
    Abid your examples are of Stalled wings in uncontrolled spiral dives and the wing failures were all from negative loads. How do you equate this with what the discussion has been. Wing not stalled and in positive flight modes? Think of the
    wing climbing toward the ground and excessive lift (quote Larry) Apples or Oranges?
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    No these are -NOT- stalled wings.
    The spiral started due to a stall on one accident. That does not mean that as spiral progressed one of the wings was stalled or more stalled than the other. That would be a spin and in the spin, airspeed does not keep increasing.
    There are various ways to do a spiral entry, stall without proper recovery and proper roll input is just one of them.
    This stuff is nothing new. Airborne XT which is a older than a decade trike has this same exact advice in the POH:
    "A spiral dive may develop after a stall if the bar is maintained at the forward limit and a large roll rate is allowed to develop. If this condition is not corrected it will lead to large and increasing roll attitudes (beyond the 60 degree limit). Increasing attitude, increasing speeds and large control bar feed back forces will occur. Incipient spiral dives can be terminated at any time by rolling wings level.
    If the spiral dive is allowed to develop to extreme roll attitudes, recovery is expedited by relieving control bar forces before rolling wings level and recovering from high-speed condition."

    This does not automatically mean that because you started a spiral dive due to a stall and improper pilot action on recovery, that that means that wing is going to remain stalled.

    I am not sure about Larry's climbing in a turn. I didn't really follow it to comment. I think numbers, vectors forces and component vectors. May be Larry is trying to dumb things down. In recovery after coming out of the spiral, you have a high chance of high positive G load and G due to G. You have to control pitch up attitude just as is explained here. Nothing new here either. This is the same for airplanes.
    http://www.youtube.com/watch?v=ySHDicIlpqA

    Sequence as explained is:
    Aircraft rolls into a bank but AOA is not increased.
    Vertical component of lift is not sufficient (less than weight) so the aircraft begins to "fall."
    Relative wind is now from below - so nose pitches down
    Aircraft is now descending so Thrust should be less than Drag - but it isn't- Result is that airplane accelerates.
    As speed increases lift increases - this will continue until lift reaches the required amount (note AOA is still as it was trimmed when the airplane rolled into the bank.)
    If bank increases more then speed must increase more.

    As for why outer leading edge on Delta wings will show negative G loading like break ...
    geometric washout, delta wing, flight at high airspeeds for -washed out- tips (remember extra positive loading increases washout at the tips) taking the tips to negative AOA and reversed loading can do what you are questioning. Trike wings that do this have significant washout from root to tip. You got to read the whole thing and read carefully. Here is the summary end from the report.

    "In all three accidents, the failure of the main wingspars had occurred near the wingtip. Qualitative analysis of the structural design and loading of the part during this safety investigation and the examination of the coronial findings from the Hexham accident, revealed that all main wingspars had failed under negative G loading. Such loading was likely if the aircraft entered or encountered flight conditions outside the manufacturer's specified flight envelope. Examination of material characteristics of the failed wingspars did not show evidence of material deficiencies that could have contributed to these accidents.

    The manufacturer's operating handbook prohibited all aerobatic manoeuvres including whipstalls, stalled spiral descents and negative G manoeuvres. The manual specified that the nose of the aircraft should not be pitched up or down more than 45 degrees, that the front support tube of the microlight and the pilot's chest limit the fore and aft movement of the control bar, and that the aircraft should not exceed a bank angle of 60 degrees.

    Review of photographs of the Airborne Edge, indicate that the wing adopts a degree of twist while in flight. Twist will effect the load distribution by shifting some of the lift from the tips inboard (i.e. more lift is generated in the middle of the wing). Given the structural restraint of the tip struts and battens located at the tip of the trailing edge of the wing, the aerofoil at the wing tip must adjust and try to align with the relative airflow. This results in a smaller amount of lift generated near the wing tips due to a reduced angle of attack to the relative airflow." (Or an aoa reduced below the zero lift aoa, i.e. reversed lift ... JB)"

    I hope that helps explains the seemingly contrary result of obvious negative loading break outward on the tips from an excessive positive loading on a highly geometrically washed out flexwing structure. Delta wings with aero-elastic structures like trike wings are interesting animals indeed but there is a science to them and they do make sense.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Ted: Regarding G due to G not a factor ... well it surely is. People like Bill Brookes with Ph.D's in aerodynamics and designing trike wings among other things are not just making it up.
    There is high G loads in the spiral dive itself.
    Second, if your spiral dive at VNe wasn't accelerating you were NOT in the spiral dive that we are talking about. You were in stable flight spiral. Accelerating spiral dive is something different. To me, even this very video where Larry is slowly accelerating is not quite a great representation of the most dangerous spiral dive we are talking about here to be very frank but it makes the point in the second half specifically (which is closer) by going to 2000 FPM spiral dive and recovering with correct technique which is absolutely not any different than it would be in an airplane except they also have to worry about the rudder position. If that spiral was allowed to develop further by pushing the bar out or by hitting the throttle, I can guarantee you that spiral dive would go to 2500 FPM in seconds more not minutes.

    This is NOT just a concern for newest generation of trike wings. Hate to break it to you. I gave you examples of accidents from 1995-6. Airborne Edge, Airborne XT 912 (12 year old design). Raven wing from UK (older than dirt), Alpha, Gemini Flash (older than dirt) trike wings. It just sounds like you have never been there. Perhaps we have seen it because we are flying wings in development when they are not as nicely behaved as they are afterwards development is finished and perhaps the tests that are done require actions that can put that scenario into action. Certainly no one wants to go there. I have heard denials here like this doesn't happen. That's rubbish. It happens. It may have even happened in the very recent Washington state fatalities. We won't know till they finish investigation. It probably happened in 7 year old mystery NJ fatalities.

    If the real world numbers are 80^2/55^2 and this is the speed range of your wing, its a lower efficiency artifact in action. That's a very narrow speed range. What you are saying here is that when you come out of a spiral in straight and level dive, you can only go to 80 mph and S&L your Vso is 55 mph. That is not even much above 1.5Vso. We are not dealing with just banked wings, this is for pulling out from the VNe to Vso in S&L dive scenario. Just to clarify.

    Well lets not even go to loops. I think there are aircraft made to do loops. WSC tailless aircraft are not for that.
  • Ted  Bailey
    by Ted Bailey 5 years ago
    No those were actual speeds with a classic level entry for a standard loop.
    VNE for that wing was 90 and stall 35 with the trim @ 50. Never said Bill made it up
    just not a factor unless your pulling mega G. But you have changed the scenario from Larrys question. Now Its become an uncontrollable death spiral from a tip stall?
    I have'nt had a tip stall or a lockout since 1983. How you get a tip stall when your trim is 20+ over stall must be serious pilot error. Personally If I believed all the cya stuff on the disclaimers listed on a new wing I wouldn't buy one or fly one.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Well Ted. I don't know what the issue is here. In an accelerating Spiral dive that every private pilot for airplane gets a full lesson on recovery and that is known to be an issue in the aviation world (and trikes are no different), you are pulling G's. Not just in the spiral but also possibly in recovery. Even PPG guys pull mega G's in such a spiral. Trikes are not special enough to get by without a possibility of an accelerating spiral dive.
    I said nothing about a tip stall.
    Its clear to me you have never actually been in an accelerating spiral dive and you don't believe it can really happen.

    Ok.
  • Abid Farooqui
    by Abid Farooqui 5 years ago
    Paul H:
    You better write something up on the accelerating spiral dive and recovery in your handbook. I would hate to think some newbie go out and do the steep turn maneuver and get hit by his own wake and let the nose drop and then tries to recover from it by pushing the bar out and hitting the throttle. If he is low enough, he will be splat into the ground and if he is high and doesn't know what is going on he will just keep tightening the spiral and pulling more and more G's till he goes past VNe and breaks off a wing
  • Paul Hamilton
    by Paul Hamilton 5 years ago
    Yes it is coming in a completely new chapter (Advanced Mneuvers)
    Paul Hamilton
  • John Olson
    by John Olson 5 years ago
    Meanwhile, we can just do what we've always done-go out and make some turns with the student until he hits his own wake good and hard and gets an impression of what it is and why it happened, a very basic maneuver.
  • Wesley Frey
    by Wesley Frey 5 years ago
    Someone said to correct quickly if you notice a high speed develope in the spiral dive. Then others bring up the danger of high Gs over stressing the wing. If you make a nose down turn and find yourself close to your allowed top speed (pilot or wing limit); the leveling can be delayed by maintaining that speed through the roll to level (holding the bar in) and slowly decreasing speed (letting the bar out), to avoid excessive Gs, which you can feel in your seat. It may be obvious in a pitch down (wing level) attitude to loose altitude, when the wing won't let you go to top speed, but not so obvious in a steep decending turn.
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