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  • #16
    I hear you Tyger. I'm not a US guy and so have in truth little idea of the practical detail of aviation in America. However in the UK you can (and I did) run a 912 on regular 95UL automotive fuel from temps as low as -5oC to 33oC with no issue and whilst our density altitudes in the UK are not +6/7000ft they are certainly over 3000ft+ during the summer, especially in 2018 which was very hot throughout July and August.

    Yet this isn't an attempt to deny what happened did take place - its exasperation that it happened. It would be interesting to hear the reflections of what was said between "victim", Rotax US and Auto-Gyro US because clearly 5 x similar engine outs are unacceptable and that everyone was able to walk away happily is to the credit of the pilot. Still it is not a scenario I would seek and actually given the nature of this very forum where is the highlight of the issue here? I'm not sure I can see it reflected in the Auto-Gyro part of this site.

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    • #17
      Personally, in practice, I have never found it terribly difficult to shed energy in a gyro, given how draggy they are and what a pitiful glide ratio they provide, and I've always been able to adjust pattern size/shaping and speed so that I have never required S-turns. It seems a little strange to me to describe a situation in which one has too much energy to land at the desired spot yet simultaneously be concerned about entering the the avoid region of the H-V diagram where inadequate energy for safe landing is the worry.

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      • #18
        I agree Waspy and I think anyone concerned ref HV curve in vertical descent (for example) do not understand the rational of HV curves - which protect against sudden and unexpected engine failure. Where you are back at flight idle established in a descent one might expect your awareness to be total.

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        • #19
          Originally posted by Philbennett View Post
          I agree Waspy and I think anyone concerned ref HV curve in vertical descent (for example) do not understand the rational of HV curves - which protect against sudden and unexpected engine failure. Where you are back at flight idle established in a descent one might expect your awareness to be total.
          Can you elaborate on this? How does the HV curve “PROTECT” against a sudden engine failure?

          You seem to be implying, with the total awareness during an engine failure, that the HV curve is moot and, for example, you can safely enter even into a “vertical descent”, as you say, without concern for how you’ll arrest that descent?

          Not being a helo pilot myself I can imagine that’s POSSIBLE for a helo with a variable pitch rotor but how about a gyro, with a fixed pitch rotor?

          Seems to me some of the stories we’ve heard on this board relate directly to gyros getting too slow too low to effectively be able to arrest their descent before touchdown.

          This is actually the essence of my OP: how to shorten a descent path while respecting the Hv curve. If it’s indeed acceptable to ignore the HV curve when the engine is out, then that offers options. I don’t think that’s accurate, though, in a gyro. “Parachuting” down is probably survivable in my Magni but would definitely bend it.

          Thanks for clarifying.

          /Ed

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          • #20
            In the gyro context, the protection comes from ensuring that one has adequate energy to provide time to react to an unexpected power failure while under power, and still retains enough energy after that reaction time to be able to arrest the descent rate with a timely cyclic flare. It is usually based upon assumptions about average reaction time, pilot skill, etc. If you stay out of the "avoid" region you should have ample energy on board from the combination of speed / kinetic and altitude / potential. (It is assumed that you have normal rotor rpm but as you observed, it is hard to extract that practically without collective pitch control, and for low mass rotor systems it doesn't store all that much anyway.)

            For approach purposes, when you are already at a low power setting, descending, with a spot all picked out, a sudden engine failure should be far less of a crisis. There are still combinations of speed and altitude that won't be conducive to a nice arrival, but the situation is different. If one drew an HV diagram for approach (they are typically drawn for climb and cruise) the avoid region would be substantially smaller and likely a different shape. I can't recall seeing one from any manufacturer. Combinations of altitude/speed that could be disastrous on climb-out if the engine surprisingly went quiet need not be so when you are already gliding downward and less dependent on having power available for the flight path you have planned.

            I don't think "parachuting" is the best of ideas (although there are some with long travel gear suspension who might fare better). Ordinarily, one would expect to terminate a vertical descent by pitching for speed, and then flare for touchdown, but the critical question raised by this is how low one can take the descent and still be able to complete the rest safely.

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            • #21
              There is no "fits all" answer.

              If your chosen landing spot is right below you and is otherwise a landable surface (not water, trees, rocks, swamp or other crashy substances), then IMHO it requires less skill and luck to maintain airspeed and do S-turns, circles or whatever is necessary to set up a normal engine-out glideslope. This is not to build up rotor RPM, it's to adhere to a uniform glideslope, to make your aim more accurate. Any buildup of RRPM before the last second just messes up your glideslope. So there's no need to pull big G's in your S-turns.

              Yes, a vertical descent can be used to bleed off altitude, but recovering airspeed from an engine-out vertical requires a steep dive and a stunning amount of altitude. It's a fairly radical maneuver that makes it much harder to guage your landing spot.

              OTOH, a vertical descent (probably one entered very low) is the thing to use when landing on water, in trees, or other surfaces that are going to trash your machine anyway. In this case, our goal is personal survival. A pusher gyro has far better crash protection when "pancaked" in than it does in a frontal crash.

              The Cierva-family machines had long-stroke gear that allowed routine landings from vertical descents; that feature, however, has since been un-invented. Perhaps this happened for the sake of simplicity, light weight and cost reduction. Certainly the technology has been around for nearly a century.

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              • #22
                Doug, I agree with all of that and it makes sense.

                WaspAir, I also agree with what you're saying and realize the "standard" H/V curve includes some "WTF?" time in it, to figure things out, and the latter is not needed when you KNOW the fan stopped blowing. Nonetheless there IS an H/V curve for engine-out, specifically for the reason Doug notes: I've always been surprised by how much altitude it takes to recover from 20mph with the engine at idle. I contend S-turns done at the proper speed allow more options and avoid a big drop.

                Phil's statement was "...ref the HV curve in VERTICAL descent" - not in STEEP descent. A truly vertical descent with a fixed-pitch rotor would give zero ability to flare. But the more forward speed, of course, the more ability to flare and land safely. Phil may have actually meant "steep" - or it may be a carry-over from helos (and I notice your pix is of a gyro with variable pitch rotor blades) - wasn't sure.

                I've piloted only Magnis, with their straight keel, so I was taught to always have good forward speed until right before touchdown. I was really surprised to see an ELA in the pattern and watch them "flare" about 10-15 feet up in the air: my first reaction was "holy cow - that's gonna be a hard landing!". I think the bent keel encourages people to be more aggressive about their touchdowns and that seems to work 99+% of the time. But, IMHO, some of the mishaps I've heard about on here seem to be related to getting bitten by that assumption. That's particularly true for gusty conditions, I suspect, where the air up through the rotor the pilot thought the wind had promised suddenly goes away and there's nothing else to convert to lift.

                By the way, this also relates to go-arounds. If one slows to 20mph, one simply cannot power out of that in our gyros; there needs to be a loss of altitude to gain enough speed to fly out of it (the "behind the power curve" discussion). In my Piper Warrior I'm always able to go around, even down to the last inch before touchdown, because I have enough lift from my forward speed and haven't slowed down too much. With the Magni that's almost the same because I carry 65mph until a foot or so off the ground. But slowing to 20mph 10 feet above the ground? You're committed to land at that point. I honestly don't know if y'all actually slow to 20mph at 10 feet, but the point is there comes an airspeed and altitude where you're committed and cannot go around with that method. Holding more speed avoids that.

                /Ed

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                • #23
                  Important points just doing response

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                  • #24
                    Phil if that gyro in the video post# 8 is yours, it needs a rotor track and balance, lots of 1/rev. Could I get a copy of the video I need a good example of 1/rev stick shake for my Rotor Track and Balance training program?
                    Mike

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                    • #25
                      Hey Mike - yes please take the video from YouTube. Yes you are right lots of 1P!

                      So the reference to the H/V curve are absolutely relevant. i.e. if you are back at flight idle and in an established vertical descent (I’m not clear on where the parachute term comes from but I’m referencing a usual vertical descent) then there is no surprise. Clearly you’d be a complete fool to continue the descent below a height that you knew recovery was possible. But the point remains that flight at slow speed with a reliance on the continued operation of your engine is very different to flight at slow speed with the engine back at idle because the attitude of the aircraft is totally different and your awareness / expectation is different.

                      Again if you watch my film on vertical descents then I think the technique for them is quite clear and the recovery to the glide consumes circa 150-200ft to achieve 60mph and the pitch attitude isn’t extreme.

                      https://youtu.be/w6NpQr5BKMc?t=75

                      I'm surprised the view re vertical descents and extreme measure and you can see (I think??) that the cockpit view doesn't look very dramatic.

                      To recap my point on S-turns and vertical descents.

                      The problem with S-turns is No.1 the danger is vision as you are either looking where you are placing the aircraft in the S-turn OR you are looking at where you ultimately want to go to OR you are looking at instrumentation. You can not do all things. So one video I posted was the guy doing S-turns and almost collecting wires. That was because he just wasn’t looking / wasn’t aware because he was too busy flinging the aircraft around. No.2 it is dynamic which requires more control input than a vertical descent.

                      I've even flown with guys who even loose sight of the field they were making an approach to and get lost!


                      The other point I’d like to make – and it is a very important point – is that it is one thing practicing all this to your local airfield but it is another to be putting these things into practice over open countryside, especially in a terrain as is typical in the UK when very often trees, fences, wires, hedges and other countryside furniture waits to snag you. Using S turns or doing orbits puts you at greater risk.

                      On the other hand if you have an engine out – which seems increasingly likely in a Cavalon using the recommended Rotax fuel of MoGas (I'd still like to hear the story!) – then you have two choices. Fundamentally you either need to get to your chosen field, or you are there and you just need to descend. So either set best glide speed and transit or descend vertically and position on a base leg to your chosen field.

                      I would find it quite incredible to believe that a pilot confident to S-turn his way accurately into a random field could not equally safely descend vertically to (say) 4-300ft on a base leg before recovering airspeed to 60mph and judge an accurate glide from there.

                      If you can’t judge your glide accurately from 300ft then that is something else but it strikes me I can’t think your S-turns are going to be done any better??

                      In the end like all things it is a matter of practice but you have to be realistic. You are flying for fun and with other distractions, it is better to make the task as simple as possible and just because you could do things and did things at your training airfield and got pretty good means what? 1000ft glide approaches with a few S turns over the perfect environment of an airfield doesn’t really relate to engine outs when the best field is where, which is how large, what shape, with other hazards?

                      Vertical descent – keep your eye on the field, looking for hazards, looking out of the window to ensure you recover on time and you only have 300ft to make a hash of! There is literally old one hazard once you are in range and that is recovery of airspeed but you can practice that effectively anywhere.

                      Finally there are a lot of guys getting hung up on approach/landing speeds but that (perhaps) comes from the very experienced guys having a legacy in single seaters which do not handle well on the ground. However unless you actually are flying an old single seater I’m not entire sure why people would want to use a compromised technique for an aircraft that doesn’t suffer the old vices. I leave you with the words of the FLIGHT test pilot in 1966 having tested Ken Wallis’ WA116. 40kt approach in a light single seater to level attitude. Hmm that seems a far cry from the zero/zero type approaches advocated. The key word is SIMPLE.
                      ….although there is no problem to a deadstick handling but, of course, the flare must be precise and is complicated by the approach angles involved—much steeper than for most light fixed-wing aircraft. Normal touchdowns from a power-on approach at 40kt are perfectly simple —just keep the aircraft level and the ground cushion will do the rest….

                      Comment


                      • #26
                        Originally posted by Vance View Post
                        I have had two engine outs in two different Rotax 914 powered Cavalons from a sinking float.

                        I have had one engine out in a different Rotax 914 powered Cavalon when the battery failed.

                        I have had five engine outs in three different 914 powered Cavalons from what I believe is vapor lock. We were using alcohol free automotive gas. Switching to 100LL appeared to solve the problem.

                        Most of these events happened at altitudes and temperatures not commonly found in England.
                        Based on the above quotation, I have three questions (for anyone to answer, not only Vance):
                        1) Why would a dead battery cause the engine to quit?
                        2) Why might 100LL be less susceptible to vapor lock than E0 unleaded?
                        3) Is there something in the design of the Cavalon that might make it more susceptible to vapor lock?

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                        • #27
                          (1) A 914 has two electric fuel pumps, the battery developed an internal short and the alternator did not make enough power to run the fuel pumps.

                          (2) Alcohol free unleaded automotive fuel may have a higher Reid Vapor Pressure (RVP) than 100LL. The Reid Vapor Pressure is a common measure of the volatility of gasoline. Vapor lock occurs when fuel, normally in liquid phase, transitions to vapor in the fuel line.Often in the winter months they raise the RVP in automotive fuel to make for easier cold starting.In my opinion this increases the tendency to get vapor lock.

                          When I switched to 100LL in frustration two of the Cavalons ran and started fine.I did not get a chance to put 100LL in the third.The automotive fuel was from two different sources but in my opinion both were formulated for winter.

                          (3) Yes, in my opinion the Cavalon has high under cowl temperatures; pattern work, high density altitude and the turbocharger exacerbate this. One carburetor is directly over the turbocharger and is often hot to the touch.
                          Pull the throttle back (set to idle at 1,800 engine rpm) and the engine would sometimes go quiet and would usually not restart.

                          One began to run erratically on climb out after it had died while landing on a cross country.The tank was half empty and we filled it with 100LL and returned home with no further issues.

                          The pressures and temperatures were all in the green in every one of the episodes and the second fuel pump was on.

                          It would typically start and run fine in about forty minutes if I had not run down the battery.

                          We did not find anything wrong with any of them.

                          I am not a Rotax trained mechanic but both of the A&P mechanics working on the engines were.
                          Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

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                          • #28
                            Originally posted by Philbennett View Post

                            Finally there are a lot of guys getting hung up on approach/landing speeds but that (perhaps) comes from the very experienced guys having a legacy in single seaters which do not handle well on the ground. However unless you actually are flying an old single seater I’m not entire sure why people would want to use a compromised technique for an aircraft that doesn’t suffer the old vices. I leave you with the words of the FLIGHT test pilot in 1966 having tested Ken Wallis’ WA116. 40kt approach in a light single seater to level attitude. Hmm that seems a far cry from the zero/zero type approaches advocated. The key word is SIMPLE.
                            [LEFT][COLOR=#111111][FONT=Arial][SIZE=12px]
                            In my experience an inexperienced pilot will be challenged in a thirty five knot touch down in a Cavalon on a concrete runway particularly in gusting and/or crosswind conditions.

                            I don't think of a less than fifteen knots of ground speed at touch down to be a "compromised technique."

                            A zero/zero type approach is not language I am familiar with.

                            I teach my clients to maintain approach speed (fifty knots indicated air speed in The Predator) until rounding out around 15 feet above the ground and run out of altitude about the same time they run out of indicated airspeed with a nice flare just before touch down. Typical touch down ground speed would be less than fifteen knots.

                            What is the relevance of the Ken Wallis test pilot report?

                            I have very little experience in what you may be referring to as legacy single seaters so they have no influence on my approach to landing.

                            Regards, Vance Breese Gyroplane CFI http://www.breeseaircraft.com/

                            Comment


                            • #29
                              Hey matey - sorry the relevance to the Wallis reference was that actually how different was it (technique wise) all the way back in 1966 with an aircraft that people may accept was a step further on from the Bensen B8M of the same period. Without wishing to go down a rabbit hole the 40KT was reference the approach speed not touch down speed - which nobody is referencing. He also talks of an obvious float rather than the zero/zeo (I.e you run out of height and speed at the same time and is a helicopter technique) landing similar to that described by JM. But anyway the wider point is we are all in an era where those with a lot of experience are often legacy single seat guys and sometimes it compromises operations in 2019 with factory type aircraft. I can not fly super slow circuits because the airfields in the UK mean I get under the feet of many fixed wings and at some point the complaints come and then you are banned, etc, etc.

                              On that engine issue Vance what did Autogyro and Rotax say?

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                              • #30
                                I've piloted only Magnis, with their straight keel, so I was taught to always have good forward speed until right before touchdown. I was really surprised to see an ELA in the pattern and watch them "flare" about 10-15 feet up in the air: my first reaction was "holy cow - that's gonna be a hard landing!". I think the bent keel encourages people to be more aggressive about their touchdowns and that seems to work 99+% of the time. But, IMHO, some of the mishaps I've heard about on here seem to be related to getting bitten by that assumption. That's particularly true for gusty conditions, I suspect, where the air up through the rotor the pilot thought the wind had promised suddenly goes away and there's nothing else to convert to lift.

                                With the Magni that's almost the same because I carry 65mph until a foot or so off the ground.
                                But slowing to 20mph 10 feet above the ground? You're committed to land at that point.
                                EdL, glad to read this, but where were you in that thread in which I advocated penetrating a gusty final with higher AS and a very low roundout?
                                You seem to carry more speed (and do so lower) after roundout than even I do. Prepare yourself for howls of disapproval.



                                In my experience an inexperienced pilot will be challenged in a thirty five knot touch down in a Cavalon
                                Without wishing to go down a rabbit hole the 40KT was reference the approach speed not touch down speed - which nobody is referencing.
                                Ah, Phil, now somebody else understands how it feels to be so inexplicably misquoted.
                                Rabbit hole indeed.

                                ___________
                                Regarding S-turns to lose altitude, it seems a FW technique vs. a gyro one.

                                Regards,
                                Kolibri
                                PP - ASEL complex (C172RG, Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, Sport Copter II, M912), soloed in gliders

                                "
                                When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

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