S-turns

[EdL]

This is kinda directed towards Phil but I appreciate others’ input.

The comment/video in another thread about S-turns was spot on re the fallacy of “loading up the rotor”, in my opinion, but I want to make sure the benefits of S-turns was not completely lost.

With my Piper Warrior, I have several tools for safely losing altitude quickly: pull in some flaps, do an aggressive slip, etc. With the gyro, I was surprised at how hard it could be to lose altitude while still preserving appropriate airspeed and staying outside the H/V curve. S-turns seemed to be a very useful tool for that. I do NOT do high-g and/or high-bank versions and do make sure I preserve my intended airspeed but they do have the effect of extending the flight path and make it easier/safer to touch down “right THERE” when needed. I only do them when lined up on the runway and when too low to safely do a 360 but I use them often when practicing engine-outs on the runway to a specific spot.

Thoughts/comments/suggestions?

/Ed

 

[Tyger]

At what altitude do you usually find yourself doing these?

 

[EdL]

At what altitude do you usually find yourself doing these?

Generally, below 500 (above that, a 360 or slow-flight is an option) and down to, maybe, 50 feet or so, decreasing how much I go left and right as I get closer. Obviously that varies a bit for the circumstances, such as if there’s a gusty cross-wind and I need to get well established for the touchdown. And I try to do most of the maneuvering up higher but that runs the risk of under-shooting the touchdown if you do too much.

It’s definitely something that should be practiced over a long runway if one opts to use it.

/Ed

 

[Tyger]

Ya, I personally would go the slow-flight route till as low as about 300 ft. I don't think I would mess around with an S-turn any lower than that, in any case. If I'm that far off the mark that late, I'll probably just go around. Undershooting can of course be corrected with a little power, assuming your engine hasn't well and truly quit. I wonder if former fixed-wing guys may be too wedded to engine-idle landings, as I think Phil Bennet has suggested.

 

[EdL]

To be clear (and I wasn’t), this is primarily practicing engine-out scenarios where, for example, you have a relatively small hole among trees or something. You’re right: it’s not good for salvaging a bad “normal” landing.

Day to day, I don’t do slow-flight below 500 feet but you’re right: I think the H/V curve for our Magnis is conservative plus if you’re fully aware you’re inside the curve and your engine is out, the top of the curve would be lower since you won’t lose altitude and response time simply recognizing an engine-out situation.

That said, I still am taken by how long it takes to bleed off excessive airspeed from a steep, rapid descent or recover airspeed from slow flight compared with my Warrior. Was just curious what others do for that; my concern is people may pull the stick back and parachute down, which will probably be survivable in most gyros but this seems like a reasonable alternative. My instructors seemed supportive of the approach and didn’t offer alternatives that I recall.

/Ed

 

[PJB]

Hey - Sorry I'd missed this, just been distracted with somethings. OK good question and before I answer about S turns I'd just like to give some context to my general view.

I am genuinely a big fan of gyroplanes and think for GA they have a lot going for them. IMO the reason they are not more popular is that for many they are a seen as a deathtrap and not because the aircraft defective but because very often there are silly piloting errors.

Now there are silly errors in all forms of aviation but the fact remains as a group "we" suffer by some margin from the over enthusiastic / over confident and dare I say it - some of that "rot" is set in from the start.

Here is a link to a lovely documentary on a microlight rally in the UK. You may have seen it before - if you haven't make a cup of tea and enjoy this TV gold before the video is blocked. It is a wonderful adventure tale and in many ways it reflects for a lot of us - myself included - why we go flying. It is very easy to adopt the moral high ground and forget what flying is about.... BUT. Frankly the airmanship in this film is horrific and sadly there are shades of gyroplanes in this.

I know one size doesn't fit all and I don't want to get into a huge moan up about who promotes what and XYZ doesn't happen at my school etc etc. Of course I am sure everyone is by and large professional but now and then we mess about OR we do not leave as much on the table as we should... If it goes wrong at that point it is going to hurt. YouTube is littered with little films that depict very poor airmanship by people that really should know better and if we reflect on a recent accident then again IMO part of the problem actually was airmanship. I digress.

S-turns. So my point about these is I'm not a fan because I can not see the rational. If you are high enough just use a vertical descent because they are far more useful - manly because the control inputs are far less, it is far more accurate and your vision is maintained throughout. If you are too low for a vertical descent then why am I going to teach a student pilot (remember the usual 10hrs P1 guy) to make very dynamic flight so close to the ground - which he then has to stop doing and then put accurate control inputs in so he can land.

It just makes no sense and if you aren't really making the S turns that dynamic then really are they S turns?

Again it risks a big back and forth and I am just giving my own view but I am really a big fan of keeping flight for students super simple and we can do more advanced things later on. In the UK I fly off an airfield with both grass and tarmac options but the tarmac is +1.1kms and the grass option is just under. My 10hrs P1 guys really doesn't need to land on a spot. It is utterly pointless.

Yes some will make the "Oh well how will your student fair in an engine failure.... landing accurately is a good skill" and yes a very good point BUT engine failure is preparing for the 1% while making it hard for the 99%. Why is it making it hard - because it puts pressure and it requires or encourages the use of technique that has increased risk - either lower speed approaches that can lead to high sink rates and a heavy landing or glide approaches which increase risk in a regular circuit and a more challenging round out. We can get on top of all of that but why make it harder than it needs to be??

Enjoy the film!

 

[Vance]

In the USA part of the FAA practical test standards for Sport Pilot, Gyroplane is about power off accurate landings.
B. TASK: POWER-OFF APPROACH AND ACCURACY LANDING REFERENCES: FAA-H-8083-21; Gyroplane Flight Manual.
Objective. To determine that the applicant:
1. Exhibits knowledge of the elements related to performing a power-off approach and accuracy landing.
2. Selects a reference point in the landing area for touchdown and reduces power to a zero-thrust position.
3. Adjusts glide path to terminate approach and touch down beyond and within 300 feet of the reference point.

With around 2,300 hours as pilot in command of a gyroplane I have had five engine outs powered by Rotax, Two powered by Lycoming and one powered by Subaru all without damage to the aircraft of injury to the occupants.

I feel learning to make emergency landings is a useful skill.

I also teach engine out on takeoff procedures even though they are not part of the practical test standards for Sport Pilot, Gyroplane.

We are also required to teach

B. TASK: HIGH RATES OF DESCENT AND RECOVERY REFERENCE: FAA-H-8083-21; Gyroplane Flight Manual.
Objective. To determine that the applicant:
1. Exhibits knowledge by explaining the aerodynamic factors and flight situations that may result in high rates of descents, and the procedures used for recovery.
2. Selects an entry altitude that will allow the recoveries to be completed no lower than 600 feet AGL.
3. Establishes a high rate of descent at a minimum airspeed with power below cruise setting.
4. Recognizes high rates of descent and recovers promptly to a best glide airspeed.
5. Recovers by demonstrating proper power management and returns to cruise airspeed.
6. Maintains a specified heading, ±10°.

It doesn’t take a lot of reading between the lines to see that the FAA does not endorse training vertical descents as an approach to land.

In my experience the altimeter lags in a vertical descent making it more important for the pilot’s eyes to be outside during a vertical descent to land.

I find that most low time pilots have trouble learning this skill even with the limitations the practical test standards put on it.

Add the close proximity of the ground rushing up at them and it makes for a challenging teaching environment.

For simulated engine out accurate landings I prefer teaching using three hundred sixty degree turns at the approach speed, S turns at the approach speed or increasing speed to steepen the descent.

I feel they can practice a vertical descent approach to land as their skills increase.

 

[PJB]

I knew this was going to happen!! Ohhh. OK.. I think engine failure wise I'm not sure what you do or what environment the aircraft are operating within BUT if I relate you stats to the UK then I think the differences will start to emerge. In the UK effectively the only Subaru powered gyro we can fly is the RAF2000 and there are few flying and not a single ex-student of mine has ever gone on to fly one in recent years. In the UK we have no Lycoming powered gyros (although I have many hours on various Lycomings in both Heli and Aeroplane) and the Rotax engine we do have are Rotax 9-series - 912 and 914.​

So for context for people who perhaps get one view otherwise... I've never had an engine failure (no doubt I will this coming week!) despite having similar hours P1 to yourself and in the UK as a whole - which includes some very experienced guys, one with over 7000hrs P1 in a gyro, I can only think of 1 x Rotax 9 series engine failure EVER in "factory built" gyros in the UK which was a Cavalon down with the instructor at Exeter and that was a manufacturing fault at Rotax after circa 400hrs as I recall. So if you had 5 x Rotax failures are 9 series related it would be interesting. If it is 2 stroke related then again in the UK pretty irrelevant in the current climate.​

However I predicted the debate didn't I in my prior post and again our final flight test is somewhat different. Your power off requirement has a lot of holes in it - for example when do you have to nominate the point, from what height? i.e. am I at 1000ft, nominate a point and close the throttle? Or do I fly the approach to 300ft, nominate a point and close the throttle? Does the examiner decide the points? Do I have a choice ? Do I have to do it away from the home airfield? What about entry speed? Because these things matter don't they? I can practice this at my home airfield for months within my own parameters and get pretty good... ​

indeed that is exactly what people do for...spot landing competitions for things like the world air games. Now go and YouTube things and see the shambles being made at the WORLD championships.. ​

Back to the point. Suddenly we threw +/-300ft (which is a 600 diameter circle with a bullseye) which makes spot landings less of a spot and more an entire runway in some cases. So again in the US (and its exactly the same as in the UK we have the same non-thinkers around the table when these things get made up) you can get very good at something that you don't actually need and in any event the test demonstrates to the examiner that you practiced it a lot at your home airfield. Well done FAA.​

Yes good job on the engine failures on take off - probably more relevant to the preservation of life than landing to a point - however not sure you do S turns as part of it? ​

However lets return to the rational - engine failure. Come on if you have a student with <10hrs P1 suffer any sort of failure then I think if they can walk away from the event they have done well. I don't really care if they float into the hedge beyond the runway or damage the aircraft when a more experienced man could have saved the machine. Where is the wind? Pick a spot as well as possible (wires, wires, wires and surface? the size and shape looks after itself frankly), forget the radio <1000ft, fly the aircraft, airspeed, airspeed airspeed to be accurate at 60mph. Be lucky in the UK that your airmanship meant you were not over congested areas and you had been looking for fields as part of your en-route.​

Over a built up area? Flying too low to have no options? Spot landing isn't going to help is it? We know how it does work out. If I was the FAA examiner I think the time spent on the spot landing nonsense - and no doubt the examiner special tips and hints lecture - would be better spent drilling airmanship for the 1% and a focus of the regular landings for the 99%. Oh and maybe some theory on engine maintenance.​

I don't see your item B as no vertical descent. Why do you read that? Further if you are using a 600ft AGL reference you boys have pretty poor altimeters if the lag and that height combination pose a threat! More than that enroute in the UK we fly on QNH so anything that references AGL across country the altimeter isn't really going to help beyond a best guess. Happily we fly by day in VMC... Again look at my vertical descent film.. I don't think there is anything very complex in any of that. Oh and you can see the terrain near my home. The little industrial unit we are next to is the Ford GT Le Mans program for Europe - like your Chip Gannasi.​

 

[Vance]

We have divergent ideas on teaching Phil, I don't think of that as a debate.

I don't share you opinion that Rotax 912 and 914 engines in gyroplane seldom fail.

I went through the seventeen accidents reported to the NTSB in 2017. Three of the seventeen were due to engine failure of a 912 or 914 powered gyroplane and one is a suspected engine problem but the final report has not been released yet..

Engine out emergency landing due to engine failure with no damage or injury are usually not reported to the NTSB.

I looked at my log to see my personal Rotax engine failures and realized I had underreported them, I have had eight. None resulted in damage or injury.

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.

In my opinion engines fail and people have to land.

The practical test standard is minus nothing, plus three hundred feet rather than plus or minus three hundred as you wrote. The minus nothing is because they feel landing long is better than landing short. The simulated engine out landing can be done anywhere although it is generally done from pattern altitude on downwind. Either you meet the standards or you don't.

I printed out the FAA Sport Pilot, Gyroplane practical test standards in post seven so you can read it for yourself.

There are many ways to hit the 300 foot spot. I do not recommend a slow steep descent.

Your "vertical descent" appears to me to be done at 20+ knots or miles per hour. I would refer to that as a steep descent at low indicated air speed.

To sum it up it reads to me that you feel engine out emergency landings aren't as important as I do and you advocate a low indicate air speed steep descent to accomplish an accurate engine at idle landing..

I don't discourage a low indicated airspeed steep descent, I just don't teach it although I often demonstrate it when the winds get over my training limit for the client's hours.

I advise the client to work up to a low indicated airspeed steep descent slowly on their own as they build hours.

 

[PJB]

This has thrown up something interesting hasn’t it and actually should be something much bigger than a conversation between me and you.

Just how is it possible to have two mature aviation countries speaking the very same language with the same supplier with such very different outcomes?

It can not be down to just misfortune that Rotax shipped the bad engines to the US and sent the good ones to the UK, unless the specifications are different? I do not know.

However at face value if you have had 8 Rotax 9 series engine failures then that is surprising. I think you alone possibly have had more engine outs that the entire UK instructor base over the last 10 years. But certainly the 5 x valour lock is a training issue especially with the US and its E85 automotive fuel, that has been flagged even in the UK for almost 10 years and our ethanol content is <10%. Plus just to highlight one key difference. In the UK the 912 motor is the common training aircraft not the 914. Perhaps as you say you are hotter/higher and need the performance?

Yet even where people need to land out I still do not square the ability of multi thousand hour pilots to make accurate approaches is not the same as for a new pilot. I think we are talking across each other.

The title of the thread is “S-turns”. I don’t see the rational for them in a gyroplane because their application suggests you have too much height/energy and you need a way to waste it. My overall point is that if you do a vertical descent I struggle to really see how you leave yourself in that state.

BTW vertical descent is an accurate term regardless of the IAS because it is vertical relative to a ground feature. It is not a ZERO airspeed descent, because in the event the wind speed was 20knts we would actually be travelling backwards at 20knts….. Come on basics.

I do think they are important to teach but in the context of their application. Clearly if your run rate for engine failures is 1 per 250hrs then it is a bigger focus than if the run rate is zero. In the end I have to cover the UK syllabus and my guys pass a UK test with an independent examiner, but that is not the point of the conversations here.

I respect you as a professional. My points are not specific to you or your methods. I am talking aloud and it is my firm conviction that as a group we focus our teaching efforts on the 1% which can not fail to detract from the 99%. The accident data absolutely supports that and wow what irony that the very first US fatal gyroplane accident in 2017 was actually a reasonably experienced guy practicing for that 1%.... How bloody terrible is that??!!

 

[Vance]

I am sorry you missed the part about it being alcohol free automotive fuel Phil.

It was just under 100 degrees F (38C) and four times it was at a density altitude of around 6,500 feet. Once is was 100 degrees F at around 2,500 feet density altitude.

The Rotax distributor was well aware of this problem and when I told them it was a gyorplane; he guessed it was a Cavalon.

I am not the only one who had floats sink in a 914.

I have not had a problem with a Rotax 912.

I don't know how training or a better pre-flight inspection would have helped with any of this.

 

[PJB]

My friend honestly relax. Just relax. I'm not trying to run you over, I'm not trying to suggest you are doing anything gash. When I post something its not about you. I don't lie in bed thinking about you, nor am I trying to promote anything. I have a school in the UK but currently it isn't operational because I am working on a government contract in the Middle East.

So to come back to the point of the thread and S turns. If they work for you great BUT the original poster actually asked for my view point and I have given it. It is nothing more nothing less, just my opinion.

You are right I did miss your point about no alcohol fuel. I made a mistake. It is easily done especially in aviation. We ended talking about engine outs. Again my opinion but I find the 5 x engine outs quite remarkable in the context of the experience in the UK. Perhaps others based over here could give an alternative view BUT I think after 2 or 3 engine outs in the entire community in the UK would create a lot of flap never mind 5 x engine outs with 1 instructor.

Now you say it isn't a training issue and then you post this:-

The Rotax distributor was well aware of this problem and when I told them it was a gyorplane; he guessed it was a Cavalon.​

So no training issue? Really? I mean honestly who is the a55hole here? Do Rotax USA not talk to their customer? Do the gyro builders not talk to Rotax USA? I mean WTF? Come on. That is a terrible situation that you call up the engine guy and he says... "Oh yeah we know all about that...was it a Cavalon by any chance" What as Andy Wall doing at this time?

 

[Vance]

I am trying to learn from you Phil.

When you share an opinion based on your experience that is divergent from my experience I like to understand why.

I now know that you mostly fly Rotax 912s in you training aircraft in England and like you I have had very little trouble with 912s. Only one that I can recall and because of old gas. We found the problem on the ground.

Thinking about my challenges with Rotax 914s vapor lock in Cavalons they have mostly been at high altitude and in hot weather. I realize there is not a lot of that in England or most of the USA.

It is interesting to me that you are less concerned about engine stoppage in flight than the FAA is and your reasons for it are interesting to me.

In support of your point of view about engine failures the FAA no longer has a practical test standard for accurate engine at idle landings for a Private or Commercial Rotorcraft-Gyroplane certificate.

In post 6 you recommend a vertical descent rather than S turns. That is interesting to me because it is divergent from my recommendations.

It has been my experience if a person is trying to hit a spot and are long it is usually because there is less wind than they anticipated and for me a vertical descent in low wind conditions is not a good approach for a low time pilot.

I recommend maneuvering flight and S turns or 360s because it is something most people are comfortable with.

I am always trying to become a better flight instructor and belong to multiple trade organizations so I can learn from other people's experience.

I have already learned a lot from you Phil and am grateful for the information you share.

 

[Gyro28866]

I don't feel that there is any real advantage to doing S Turns to "load the rotors" to gain rotor rpm. I say that, because within a second of returning to straight and level, the rotor rpm will revert to a steady state rpm for the loading and the additional rpm is lost almost instantly.
However, if you have to maintain a higher indicated airspeed on the approach, it will lengthen the "ground track" on the approach gaining a bit of time. This extra time may allow an already landed slow moving aircraft to clear the runway. But remember, when you buy some extra time on final, you may be crowding another aircraft on final behind you.
Personally, when flying my Dominator, I will just transition into a slow flight and cross control and yaw it to the left a bit. The slower IAS and impact on the GS will buy the extra time and with the yaw, I can see any traffic behind me. If I feel crowded, I do the safer thing and power up and GO Around.
However, my Dominator performance is remarkable. I can maintain a constant altitude with 75% power and 15 mph IAS. I do sacrifice some rotor rpm at this lower IAS, because of the increased AOI of the rotor;
in a descent like final. the rotor will loose another couple of rpm. I do keep this in mind when on a final approach, and will increase IAS on short final; if I should loose and engine, I want some energy to work with for the landing. It is not a good idea to operate with a minimum of energy in reserve.
Jus sayin.

 

[Tyger]

But certainly the 5 x valour lock is a training issue especially with the US and its E85 automotive fuel, that has been flagged even in the UK for almost 10 years and our ethanol content is <10%.

Just to correct a misperception, E10 is normally what people in the US use in automobiles these days. E85 is quite hard to find and can only be used in certain vehicles adapted for its use. E0 (i.e. "pure" gasoline) is readily available in my area (but not all areas). It is what I use in my Rotax 912, except when having to use 100LL (flying XC) which is the only gasoline available at the vast majority of airports.

 

[PJB]

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.

 

[WaspAir]

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.

 

[PJB]

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.

 

[EdL]

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

 

[WaspAir]

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.