WindRyder gyro accidents

[snowbird1]

I heard a rumor about the WindRyder gyro suddenly spinning backwards in flight. I checked the NTSB and only found one such accident- gyro on final approach @ 200' suddendly turned 90 and dove into the ground. I have heard of the same kind of problems on some other enclosed gyros. Does anyone have any info on this?

[barnstorm2]

I heard a rumor about the WindRyder gyro suddenly spinning backwards in flight. I checked the NTSB and only found one such accident- gyro on final approach @ 200' suddendly turned 90 and dove into the ground. I have heard of the same kind of problems on some other enclosed gyros. Does anyone have any info on this?

I am not very familiar with the WindRyders nor this incident. Could you post a link to the report?

My guess would be a bunt over. Bunt-over (PPOs) are common fatal accidents in all High Thrust Line (HTL) gyroplane designs that have a pitch instability and or an inadequate horizontal stabilizer to counteract the leverage of engine thrust in common flight envelops.

This would happen in both 1 and 2 place machines as well as enclosed and open.

Typically, NTSB reports of PPO accidents list a sudden pitch-over and list the cause as "pilot error" unable to maintain control of aircraft.

Often in a PPO the rotors will chop off the tail which would (or even give the appearance of) turn the aircraft suddenly before becoming a 'lawn-dart'.

If WindRiders are not HTL and have good pitch dampening then PPO is much less likely.

.

[mceagle]

Bunt-over (PPOs) are common fatal accidents in all High Thrust Line (HTL) gyroplane designs that have a pitch instability and or an inadequate horizontal stabilizer to counteract the leverage of engine thrust in common flight envelops..
Whoa there Tim!! I feel that your statement is a bit too all-encompassing. In my opinion 'bunt-over' accidents are more often than not the end result of diverging PIO. Even a CLT or dymanically stable machine can suffer from PIO although is is certainly less common. There is no doubt that there would be more total hours flown by HTL machines than others so surely that would account for a large percentage of the statistics. Given that, the Australian musters have argueably the lowest record for fatalaties per 100,000 hours - achieved largely on HTL machines.
Not making excuses, just stating what I consider facts.

[barnstorm2]

In my opinion 'bunt-over' accidents are more often than not the end result of diverging PIO. .

Tim, I agree that most if not nearly all PPO accidents start with a PIO. I was not trying to describe what gets you into a PPO but what allows a craft to have the design flaw that enables it to PPO.

HTL machines without a means of counter-acting the engine thrust off set can PPO.

CLT machines can not.


A HTL machine with a means of counter-acting the engine thrust off set is very much less likely to PPO and might even be PPO proof.

PPOs are the number 1 killer of HTL gyro pilots.

PPOs as described by witnesses and NTSB reports often include descriptions as depicted in my post.

.There is no doubt that there would be more total hours flown by HTL machines than others so surely that would account for a large percentage of the statistics. Given that, the Australian musters have argueably the lowest record for fatalaties per 100,000 hours - achieved largely on HTL machines.

I fly an HTL machine and the large percentage of my flight time is in HTL machines. Some have no HStabs and poor pitch stability with a high thrust line offset. Some have Hstabs, good pitch stability and a minor thrust line offset.

Some are every conceivable in-between mix of these attributes.

All things equal the machines with the highest thrust line off set, worst pitch stability and no HStab are the most likely machines to PPO.

HTL machines (if my understanding is correct) can be just as stable and PPO proof as a CLT gyro, if they are stable and have a properly designed HStab.

.

[snowbird1]

http://www.ntsb.gov/NTSB/brief.asp?ev_id=20001211X14280&key=1

Heres a link of one of the sudden turns and ground impact

[C. Beaty]

The WindRider accident referenced above is the one that took the life of CFI Harry Cordon of Little Rock, AR.

It was the same type of accident that killed Don Farrington in Lakeland.

Get a slab-sided machine yawed too far sideways and there may not be enough rudder/stick travel to recover.

I think Ron Herron was an eyewitness to Harry’s accident or if not, he had previously flown the machine and cautioned Harry to keep it straight.

[mceagle]

All things equal the machines with the highest thrust line off set, worst pitch stability and no HStab are the most likely machines to PPO.
.
Couldn't agree more with most of your post Tim. However you missed out the most common contributing factor of all in the above quote, and that is "pilot inexperience".

Chuck, I have not seen that written before but it always concerned me about the yaw stability of the Windrider and similar machines (and there are quite a few). A tripple tail is not much better than a small single tail in a sideways situation, and with a large frontal volume it is a recipe for disaster.
Perhaps also contributing to Ken's accident.

[barnstorm2]

How would you tell a slab-sided machine from one that is not?

.

[barnstorm2]

Couldn't agree more with most of your post Tim. However you missed out the most common contributing factor of all in the above quote, and that is "pilot inexperience"..

That was purposeful. When talking machine characteristics I prefer to consider what an 'all things equal' situation would be.

I have no doubt that low time pilots make up many of the PPO fatalitys.

I also know that many high time pilots and even CFI's have died in PPOs, so I am hesitant to insinuate that hours and pilot experience is a cure for PPOs.

.

[C. Beaty]

Tim O, as you know, when flying sideways you’re flying with the controls crossed up; stick into the direction of travel. I don’t know the rules but would guess that when the stick begins to move away from the direction of travel that you’ve reached the limits for your level of slab sidedness.

Tim Mc, the A&S 18A that Don Farrington lost his life in began as a single tailed monster but triple tails weren’t enough in Don’s case. One might expect that enough vertical tail could handle any amount of slab sidedness.

Bensen Days 2000(?) had been held a few days before the Sun-N-Fun flyin at Lakeland where Don was killed. At Bensen Days, Don had been flying the 18A well beyond its limits with extreme sideways flight and bank angles so it was not a surprise when I heard he was killed while doing the same thing at Lakeland.

[dcarr4321]

:help:
OK, I am not sure I understand the concept of flying sideways and the occurrence of PIO’s and bunt over incidents. Does this mean that the effectiveness of the horizontal and vertical stabilizer(s) decreases as a function of the angle of side slip?

That being the case; then flying with a 90 degree side slip to the relative wind would be the same as not having a horizontal and vertical stabilizer?

The trig evaluation would be: the effectiveness of the stabilizer is equal to (100% stabilizer effectiveness at 0 degrees side slip) times the (Cosine of the angle of side slip) ?

In other words, at 45 degrees side slip the effectiveness of the stabilizer is ½ and at 90 degrees side slip the effectiveness of the stabilizer is 0. ?????

Any comments?:noidea:

[Minnesota_Mike]

My understanding is that the "Dragy-nes" of the front overcomes the Stability of the Stab in the rear with the increasing degree of sideways slip...leading to one's possible irrecoverable permanent demise. I'm not sure anyone has a Tail big enough to overcome that much drag (or put another way...your Tail better have the ability to overcome the Nose...or else!).

[C. Beaty]

During severe sideslip, the airframe rolls away from the direction of travel. If the roll angle is so great that there is not sufficient stick travel to roll the opposite way and if there is not enough rudder power to correct the yaw, the jig is up. Depends on airspeed and slab sidedness.

[Minnesota_Mike]

Thank You Chuck...
That was a crucial factor I didn't even "see" in this excersie.
Ah yes...the balance of all things imperceptable related to the dance of Life.
I DO know have a lot to learn yet before I strap in.

[All_In]

During severe sideslip, the airframe rolls away from the direction of travel. If the roll angle is so great that there is not sufficient stick travel to roll the opposite way and if there is not enough rudder power to correct the yaw, the jig is up. Depends on airspeed and slab sidedness.Chuck, so if the "roll angle is so great" (does this happen so quickly the pilot cannot react and is that why they run out of sick?)
And does increasing the size of the rudder prevent or least help to reduce this tendency and give the pilot time to react?

[Mac]

A fixed vertical stabilizer provides forward stability. A rudder provides yaw force which rotates the craft around the center of gravity. When a vertical stabilizer is made to function as a rudder, forward stability is somewhat compromised.

The windryder has two vertical stabilizers/fins and a center rudder.

My guess/greatly speculating is that the wetted area ahead of cg slightly exceeds the wetted area behind cg and of the vertical fins when the rudder is moved to its extreme limit. Putting the craft into an exaggerated yaw initiated an adverse yaw where the nose of the craft veers further from the intended course. There is probably a gray breaking point where the yaw can not be overcome whether it is fast or just gradual.

With mast and -9 degree rotor angle rotating now even further away from relative wind, rotor rpm probably quickly decayed.

Good ole yanking and banking fun probably not a problem.

Any gyro with a large forward cabin without a sufficiently large fixed vertical stabilizer probably should not try to exaggerate too much yaw. Right stick and full left rudder with too much usable linkage may not be good.

[birdy]

During severe sideslip, the airframe rolls away from the direction of travel.
If thats the case, itd correct itself.
If it rolled away from the slip, itd slow the slip.

Putting the craft into an exaggerated yaw initiated an adverse yaw where the nose of the craft veers further from the intended course
If anyone 'lost it' here, they must be asleep.
Sure, you can yaw most cabed machines past the control limits of the rudder, but you still have the stick.

[C. Beaty]

I can see how my choice of words was confusing.

When flying sideways, the bottom of the machine swings away from the direction of travel, increasing the bank angle.

Machines such as the WindRyder and the A&S 18A have so much flat sided fuselage area below the rotor that the bank angle can become so great that with the stick on the stop opposite to the direction of slip, the bank will continue to increase. If that happens and there’s not enough rudder to straighten out the yaw, everything goes downhill in a hurry.

The FAA approved “fix” for the 18A was the addition of a “V” scribed on the windshield to indicate maximum bank angle. That’s a bit ambiguous because no distinction is made the bank angle of a coordinated turn and that of sideslip.

[dick]

When I fly sideways at airshows or whenever, I've always done it slow and "always" kicked rudder in the directions i'm sliping as to cup the air & rotate the Windryder in the direction i'm heading as to help prevent what everyone here is talking about. It can happend in any Gyro but in cabin inclosers even more so because of what Chuck is talking about..........Dick

[All_In]

Thank you gentleman that helped a great deal and I had missed the cross controlling portion of you explanation.

[Doug Riley]

In a gyro sideslip, rotor thrust applied at the rotor head overcomes the drag of the fuselage. The rotor is being used in a somewhat helicopter-ish mode, as auxiliary propulsion.

The fuselage drag is necessarily centered lower than the rotor thrust. We can't reasonably design a gyro that is "CLT" with respect to the rotor's sideways thrust -- the gyro will always be "HTL" in this regard, unless the pilot makes himself really small and rides inside the rotor head!

However, we can at least put the body's center of drag at or above the aircraft's CG. This will make it less likely that we will run out of the ability to "high stick" the gyro back to a level stance once it gets moving sideways. If OTOH the fuselage's sideways drag is centered lower than the body's CG, the gyro will tend to keep rolling steeper even when the stick is pushed in the direction opposite the bank. The drag alone creates a banking moment once the craft develops some sideways airspeed.

To help you avoid the low-center-of-sideways-drag trap:

The body can be built with a round cross-section instead of slab sides. This will require semi-reclining seating, with the pilot's feet near the level of his waist and well-raked seat backs. The whole cabin should be mounted in "CLT" position, not near the ground -- with appropriately long landing-gear legs. A large fairing around the mast adds some sdieways drag ABOVE the CG.

[Mac]

Hello Chuck
I may understand your explanation, the cabin area is acting much like a weather vane with the vane tip hung from the rotor head. Would rudder correction briefly increase rolling lift over the roll axis and turn into the bank?


Thanks Doug for your input. Took a lunch break while posting and just now noticed your post.

[Chris Burgess]

Just a short bit of info here. I have flown two WindRyders and three Air & Space 18A's. I flew the Windryder Harry was killed in. The 18A has in addition to the 45 degree bank limit (only stressed for 2.3 G's anyway), a 10 degree slip limit as well. It has an audible warning divice for slip and the "V" on the windscreen as CB indicated (FAA approved). These aircraft were not unstable in pitch but as discussed, you don't dare let the yaw get beyond the suggested 10 degree limit, unless of course you want trouble. The TwinStar has the same issue. I had one flip about 100 degrees in yaw once, and it was quick!!! We were in a strong right crosswind and got hit with a gust that started a left yaw. I was a little behind the student on it and we were flipped 100 degrees left in a heartbeat. I was lucky to roll the throttle off and apply hard left stick and regained control. I would prefer to not repeat that one. I never let the WindRyder yaw very far. I would suggest to anyone flying a cabin to control your yaw.

[barnstorm2]

Is there a 'rule of thumb' that can be applied when just eyeballing a gyro?

Like, take a photo of a gyro's side. Add up the body area. Add up the rudder surface area.

Would the resulting ratio be a fair starting point for a gyros susceptibility to slip issues?

The Twinstarr has a rudder issue that you need to be careful of. In the stock configuration (as I have) it uses seats with no support across the middle. Cloth seat covers are stretched across the open seat frame to form the seat. The seat covers are sourced from RANS.

If you have a passenger with a small butt the seat can touch the top of the rear rudder peddles, especially in a sharp turn.

The effect is what appears to be an uncommanded turn, even if you have your feet on the rear pedals.

I 'fixed' mine with a metal strap across the seat frame. a better fix is one like Gary or Brent's machines. They have made a wood seat frame that sits on top of the metal frame. This not only cures the rudder pedal issue but also raises the pilot and passenger up 3 inches which improves the thrust-line offset. 2 birds 1 seat.

.

[C. Beaty]

One way of checking whether the vertical tail is adequate or not is to take a side profile photo, paste it to a cardboard backing, cut it out with scissors and see where it balances on a pencil point.

This point is the centroid of area and it needs to trail the CG.

The same goes for the horizontal stabilizer but done with a vertical profile.

Not the full story but it’s a good starting point.

[barnstorm2]

Thank you Chuck!!

.

[Hognose]

The Army had a spate of UH-1 Huey mast-bumping accidents, which they addressed with training. A number of them were caused by pilots doing hard-yaw sideways flying in the UH-1D and subsequent models. You could get away with it in the short-fuselage B model. You could even get away with it in a D or H if the doors were open. Close the doors and you could not get away with it.

A bunch of widows and orphans sued Bell and the Army over mast-bumping fatalities, claiming that the teetering rotor was inherently unsafe. I think they didn't win, but I don't remember -- this was 30 years ago.

cheers

-=K=-

[Mayfield]

If you inadvertently get into an adverse roll yaw couple with something like an 18A; rudder the ball/yaw string straight before you try to pick up the low side with stick.

The roll "REALLY" gets your attention. It is very difficult to force yourself to leave the stick centered laterally until the yaw is sorted out.

As mentioned previously in this thread, trying to pick up the low side with lateral stick simply steepens the bank.

Jim