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UFO-HeliThruster Safety

The Topics covered below help us all understand why the knowledge of safety/design issues are paramount to good design:

  How safe is a UFO to fly?

  What happens if the engine dies - SUDDENLY?

  Can I teach myself to fly?

  I am an experienced Pilot! Do I need lessons?

  PPO, PIO and blade flapping examined and explained.

  Centre of thrust and horizontal stabilizers discussion.

  Questions regarding DRAG and its effects.

Hang Tests discussed and explained.

How safe is it to fly a UFO!

The UFO-HeliThruster has more stability and thus a larger safety margin than other gyros in its class. Why? The tail surfaces are larger and give good lateral plane area, in simple terms giving the tail more leverage to stabilize and control the gyro. Common sense dictated that by re-sizing the tail slightly larger that the minimum had to be and lengthening the tail slightly, there was a very large improvement in safety and controllability at a very small cost in weight and size. We know you'll agree that your confidence, and safety is well worth it.

The UFO-Heli-Thruster's fuselage is higher from the ground than most gyros. This when added to the fact that the rotor blades are also a little higher above the cockpit than on "standard" gyros results in greater safety, avoiding rotor strike. Also, the UFO-HeliThrusters design distance between the rotor disc and the thrust line of the engine is greater as well. Again, this increases safety by making it less prone to "tumble" (PPO) the gyro forward due to overly large control/throttle input combinations. Mac, the creator of the UFO Heli-Thruster took a close look at the safety record and stability problems of previous generations of gyros. He concluded and we agree, there is never any justification to risk controllability and flight safety. He identified the major design points they depended on, and quite simply increased the margins of safety dramatically with the improved layouts previously mentioned.

What happens if the engine dies - SUDDENLY?

This is one area that gyros excel in. Your rotor blades will keep turning and will maintain their flight RPM because of the air passing up through the rotating disc. Maintain forward speed of approximately 50 MPH while assuming a proper glide angle of approximately 25 degrees nose down and glide to a touchdown landing. If you had to be in any aircraft and you had an engine out, then make sure it is a gyro.

Can I teach myself to fly?

NO! Don't do it! We require our customers to agree to get training from an approved instructor in a two place, preferably side by side autogyro before we sell them a UFO-HeliThruster. All aircraft are potentially dangerous; therefore it is a must to get experienced help in learning.

I am an experienced Pilot! Do I need lessons?

Yes. The gyroplane is a completely different type of aircraft and does require getting used to, however, with some experience you should be flying sooner than those trainees without experience in any type of aircraft.

Following are Technical issues to do with autogyro flight and some answers to old problems now largely solved:

PPO, PIO and blade

flapping

First PPO "Power Push Over", by far the most dangerous of the three scenarios discussed here. What happens here is the gyro is deliberately forced nose down creating "Negative G". Negative G is almost always non recoverable. Gyros are NOT designed to do this maneuver. PPO is a flight maneuver (deliberate) at the top of a climb or a nose-down dive from level flight.

Further, an “innocent” POWER ON can bring about PPO! Innocent in that it should be a safe thing to do, that is, putting power on. If the design of the gyro has some fundamentals wrong with it, or a combination of them; high profile C of G, poor stability, insufficient tail profile, then when power is applied vigorously the propeller in such a craft can push the "top" of the Gyro forward while the "bottom" lags (drags) behind, thus inducing PPO. Technically what has happened in PPO is that the ROTOR has (in effect) been uncoupled from the aircraft. Therefore, if you unload the rotor (by making a zero-g maneuver) the rotor drag almost vanishes and the thrust of the engine will make the aircraft nose-down.

Power Push Over are done by people who are stupid, maybe to impress a crowd they will dive at high speed, pull out at the bottom which loads up the G forces (the rotor revs will automatically increase), they do a spectacular zoom upwards and when they reach the position when they stop climbing, we are in zero-g, for a second there is no incoming air to turn the blades, even worse the airflow is reversed, and this has a dramatic effect on stopping rotor revs. With decreased rotor revs a pilot pushes the stick forward, but it is too late; it is impossible to recover lost revs.

This sounds scary stuff and it is. We hope you aren't stupid enough to see if PPO is unrecoverable. But let's put this in perspective, when you fly an airplane you know you can't land it up side down, so you don't do it; with gyros you can't fly in zero-g so you don't do it.

Pilot Training an absolute must!

Your training will show you and train you to avoid wrong actions. Autogyros do not fly zero-g! Inappropriate or misguided actions can get you into a situation where you have little or no control over your aircraft, and a crash in zero-g circumstances is nearly always imminent. Flying a fixed wing inappropriately will also result in a crash, YOU MUST BE TRAINED!

For example: Training will include instruction on the remedies for situation likely to occur in flight. For example, you will learn what it feels like to approach zero-g and you'll be taught that when you approach PPO: Your actions will include - reduce power immediately.

MAST BUMPING, which can damage your rotor head, can also result from Zero-G unloading.

Good Design

Good design goes a long way toward avoiding aerodynamic problems. To correct a design that is faulty can often be helped by simple measures.

Simple? yes, practical? - Well that is another matter.

What UFO has done is start at the beginning! Not trying to revamp another's design. Once the design of the body etc had been produced the drag was calculated. Now care needs to be taken in designing where the thrust will be placed in relation to the vertical center of gravity. This is quite different in practice to simply sticking a "tail on a donkey"; the whole aircraft, its parts including the Horizontal and Vertical Stabilizers and even the Wheel Spats and exposed Landing Gear have to be considered. While the effect of Laminar flow technology really come into its own at higher speeds, its importance to stability cannot be taken as lightly as some manufacturers have done.

To throw yet another spanner in the works, the thrust at different loadings needs to be calculated too, as well as the gyro's attitude and behavior when coming into land. When all these factors have been taken into account and the results of "in flight tests" are known, there should also be put into the design some provision for adjusting the vertical position of the center of gravity, relative to the line of thrust.

AND WHAT IS BLADE FLAPPING?

MAST BUMPING and Ground Handling

Occurs at slow rotor speeds: Thanks to the invention of teeter hinge, gyros can fly! What they do is allow the advancing and retreating blades to position themselves independently of its "mate" according to the direction of travel re' advancing / retreating. It is these hinges that allow the blades some freedom of movement. Under normal loading blades flap as discussed in rotor mechanics, but they do not flap or bump dangerously, they are held stiff by centrifugal force acting upon them. Even so there is NOT unlimited movement neither does there need to be.

If the blades flapping movements are too large, the blades will hit stops. When this occurs it is termed MAST BUMPING from BLADE FLAPPING, the result is not only ungainly but is also dangerous, For while the blades are normally held outward at flying speed by the centrifugal force they are also "held back" by the load acting upon the rotor. Therefore mast bumping usually occurs at low rotor speeds and mostly on the ground (and/or unloaded rotor situation, that of zero-g maneuver).

PILOT TRAINING

Keep your rotor speed up!!! Obviously in flight, but also while on the ground and taxiing. If you were not aware, most accidents happen to pilots and their gyros during ground maneuvers.

While flying keep your rotor speed within the flight envelope. See the manufacturer for the exact figures: One machine can differ from another. Avoid, ALWAYS AVOID zero "G" maneuvers, and unnecessary rapid stick movement.

On the ground be extremely aware that your rotors are NOT at flight speed! They have not coned to their flight angle, they are not loaded to flight strength. With increased speed the rotors become remarkable strong, while under that speed they are quite supple. Even a minor thing like a sudden gust of wind can upset their balance and begin the flapping or bumping cycle. And, last but not least; while taxiing from rest to runway, especially over rough ground your rotors can easily be damaged. AND SO CAN YOU!

Good Design

As we have said elsewhere, good design basics are paramount. Where mistakes have been made in the past, let us learn from them. UFO-HeliThruster is a step, a very large step in the right direction.

PIO = "Pilot Induced Oscillation"

Pilot induced Oscillation - Caused by delays in the human reaction time. Also known as porpoising, which is caused by over control generally by the inexperienced. It can be likened to an out of control automobile that has lost the rear end in a cornering situation. First, the back end swings one way and then the other; with an inexperienced driver at the wheel the "fish-tailing" can become so out of control that the vehicle will spin. The inexperienced drivers responses are "out of sync" with the vehicles movements and rather than correct the "fish-tailing" the movements are exaggerated and become worse. In an autogyro the dangers are simply exasperated, for any aircraft crash has more potential for damage and loss of life.

Pilot Training

Being taught to fly by a Professional Qualified Instructor is really all that is needed. You need to understand HOW an autogyro flies, WHAT its capabilities are and what NOT to do. This cannot be had just from reading books or talking to your “mate” who has flown for years. You need to be taught by a qualified Instructor in a Dual Control Autogyro.

As was said in the piece above on “not landing an aircraft upside down”, surely this is fundamental stuff? So should be the knowledge of NOT putting your gyro into maneuvers and situations beyond its design parameters.

Good Design

Good design is paramount; UFO believes that their craft are tailor made to banish PIO from all but the foolish, for whom nothing but pain is waiting.

Centre of thrust and horizontal stabilizers

Questions about centre of thrust and horizontal stabilizers have never left the arena or autogyro design. Unfortunately too many "designers" have blindly followed the mistakes and faults of those who went before, ignoring the overwhelming design problems that have beset gyros for decades, problems that were evidenced in near misses, crashes and breakages, injuries and deaths.

It is true these topics have again been allowed to rear themselves; it is a nemesis. Retribution has come in the form of more accidents, cases not just involving broken machinery and hardware but people. Pilots know that risk management is crucial, but who would knowingly accept intolerable design flaws once they are known?

All designs evolve, that is one reason why UFO takes as their right, to alter any design without notice. IF WE DISCOVERED A BETTER WAY OF FLYING THEN YOU CAN BET WE WILL DO IT. Thus, when a problem is encountered its rectification is sought. The risks associated with poor design have been allowed to continue, it is time for a new breed of Autogyro.

A problem that recurs time and time again needs to be documented in order for the industry to learn by others mistakes and go on to better and better things. This has not generally happened within the gyrocopter industry. While the incidents are reported and collated, the causes of accidents have not been researched or approached in a scientific manner. Therefore, the problem persists.

When one begins to research this topic a good starting place is the historical "accident records" available through the CAA or FAA, through those files you will see the recurring theme played out over far too long a period. Secondly, and more up to date, though lacking an in depth analysis is the article of Jean Fourcade. Jean Fourcade (FJ) placed limits to his research and acknowledges this; there are so many other criteria that affect his findings that his conclusions are affected, in my opinion. So much so that his findings regarding the Centre of Gravity positioning being found by a theoretical mathematical formula is an issue. . . Our own Mac Gillespie considers two of these criteria, while he does not take issue with JF's conclusions as they are outlined, Mac does find issue when other criteria are added to the mix. Namely:

A Tail section that is placed in direct airflow.

The Tail Plain which combines a Horizontal and Vertical Stabilizer designed with Laminar flow characteristics, this vertical tail has a large relative area. Please note: These are not stand-alone features and cannot just be added or retrofitted to a gyro design. But when they are combined with (2) below they effectively eliminate problems suffered by other gyro designs.

A "near zero" drag body.

One of the issues not generally realized in "Centre of Thrust" discussions to-date is as follows:If an autogyro has its "Centre of Thrust (CT)" in relation to a crafts "Vertical Centre of Gravity (VCG)" say at neutral, and that autogyro is set up that way. Now let us say the gyro is sitting on the tarmac but empty of luggage, pilot and fuel. Then as soon as something is altered, fuel level - low / full, differently weighted passenger or pilot or no passenger. Say too, different weights of luggage or even apparel, then the craft is now NOT trimmed to the theoretical neutral "CT/VCG". But then neither is any other aircraft.

Consider too, that an autogyro that has been set up with one set of Rotors and has had another brand with identical dimensions but of different weight (specific gravity) material fitted; again the "CT" in relation to the "VCG" has been changed. Not very impressive in itself for we know of hang tests and the like, and surely they will re-arrange things for us? Maybe, but the issue is not at an end for should one fit wheel spats (pants/fairings) where once there were none now we have altered the "Centre of DRAG" in relation to that crafts "Vertical Centre of Gravity", although by a minuscule amount, maybe. In addition, we have altered the crafts Centre of Pressure.

What then is the answer? UFO believe that there needs to be more things addressed than just the "CT" in relation to the "VCG'. And that should include items like the Centre of Pressure - so far the arguments have been too simplistic.

Take as an example: An autogyro that has a traditional opened frame design and a moderately low CT/VCG. It is observed that when that craft comes into land, and the pilot in adding power causes the nose to come up: Then all is well! Let us also say that without the "ground effect" and in flight the same autogyro at say 60 mph puts power on again the nose will lift and, all is well.

However, let's now take the case of an autogyro that has a higher than neutral CT/VCG except this time the autogyro is not of traditional lines but has an ultra-slippery body with extreme low drag characteristics and a higher that standard Mast. This aircrafts CT/VCG cannot be set up the same way as the old traditional high drag fuselage and exposed pilot scenario! This aircraft does not conform to old theories and has to be treated in an entirely different way, just as a modern helicopter's performance does not conform to the boundaries of old ideas, neither does a modern autogyro conform to old and out of date designs.

Drag is but one of the differences here, and drag can be a determined enemy:
When one considers that at 30 knots air speed, a mere meter (39.39 inches) of square tube section of 38mm (1.1/5 inches) creates parasite drag in the order of 3.35 kgf (7.386 pounds) DRAG.

Thrust Line and the hang test.

Thrust Line

There are some recent articles that are doing the rounds and as your interest level must be high to be reading this, I would have no doubt that you are at least aware of them. Jean Fourcade wrote one of the better ones; in it he draws out some conclusions based upon open-air componentry and open air-frame gyros and generally ones based upon an older formulae. Those conclusions HE SAYS are not final as he restricts his analysis to relatively narrow parameters that were necessary for him. Nevertheless, his conclusions remain sound, and hopefully other manufacturers will sit up, take note and alter inherently unsafe designs. In doing so lives will be saved.

Now, according to J.F. the thrust line should be below or at the Centre of Gravity (vertically), and if placed there will allow the craft to be less likely to suffer PPO (Pilot Push Over). J.F. acknowledges the limitations of his research and this is where some later designs will differ from his conclusions. Mac Gillespie the designer of the UFO makes reference to the huge impact his (extremely low) drag body has, as it allows the UFO to "slip" through the air under acceleration. Just by itself this design goes some way to counteracting PPO. In addition, MG uses a laminar flow (very large) tail section fitted with (very large) horizontal stabilizers, again this design goes a huge way in preventing PPO (this too is acknowledged by JF). Mac answered some outstanding questions recently in the "Fly Gyro" British Magazine. Where he shows that there are some major criteria absent from the current discussion that still lay unsaid, and recent articles including the JF article are noted here.

O.K. enough of the theory! The UFO has been trialled and shows excellent handling, and in addition to this the engine bay and mounting system allows for adjustment of the Thrust Line, so that, it (thrust line) can be moved up and down. The trials were conducted and Mac, taking into consideration the:

1. Low Drag Fuselage and Wheel Spats.
2. The Laminar flow aerofoil and tail and of course its position and size.
3. The desired performance characteristics.

In so doing, MG of UFO decided upon a thrust line that gave a good overall performance, and to achieve that, the thrust line had to be just above the CoG. But, this is adjustable and rightly so.

Hang Test

All gyros without exception must be hang tested. It is a relatively simple procedure, and adjustment is made at the head. Basically, hang the gyro by its Head from a “crane” or a “rafter”, where adjustment is made for THAT gyros Center of Gravity.

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