Jump take-off vs. rolling take-off

PTKay

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Now, after several hours of gyro training
I have my doubts, what is safer: jump or rolling take-off.

As a FW pilot I find the rolling gyrocopter take-off a difficult
and dangerous procedure compared to FW.

In the FW you just watch V1, take off, level to Vx and up you go.

Not so in a gyroplane:
you have to take care of many actions (prerotator off, throttle up,
release brakes, back and then level stick) and parameters
(PRPM, RRPM, speed) at the same time, if you miss just one,
you can get blade flap, torque roll-over, mast bumping etc.

Some stated a gyroplane jump take-off is a stunt, but for me
a gyroplane rolling take-off is a stunt.

By a jump take off, you sit firm and still on the ground,
you have to take care only of the RRPM, holding your brakes,
until you are up to 150% flight, no risk of slow rotor, blade flap etc.

Then you switch rotor to flight pitch and up you go, full throttle,
no worries of taking off to early with slow rotor, keeping nose down,
avoiding ground hops etc. (You don't even bother releasing brakes.)

You just gain speed, keep the machine level and away you go.

Just my $0.02 worth... ;)
 

NoWingsAttached

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I dont' think you need to worry about torque rollover. But I see your point. Definitely, if I had the money to buy a jumper or the time to build one I would. It's a matter of comprimises in this world.
 

brett s

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Depending on the machine & how it's implemented, jump takeoff can introduce a whole bunch of other things that can bite. Just a different set of compromises, that's all.
 

PTKay

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Depending on the machine & how it's implemented, jump takeoff can introduce a whole bunch of other things that can bite. Just a different set of compromises, that's all.
I just can't think of many such things.

Engine out on jump or normal take-off is the same problem,
although on jump take-off you have much more energy stored in the rotor.

Opinions of those who actually did jump take-off would be appreciated.
 

Gyro28866

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PTKay:
"Engine out on jump or normal take-off is the same problem,
although on jump take-off you have much more energy stored in the rotor."
In a jump takeoff that energy is being converted as the rotor rpm are slowing, you have a small window to gain forward airspeed and get the rotor to an autorotative state, without the engine to drive you to that point. you will return to the ground. with near zero airspeed it can be a hard landing!!!
In a rolling takeoff you have the forward airspeed, an engine out is not a problem; normally.
 

PTKay

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David,

I assume you have the same prop and engine,
hence the same thrust, but no rolling friction,
so in the same period of time during the jump take-off (JTO)
you will reach higher speed than on the ground.

On top of it, you begin your JTO acceleration with, say 450 RRPM,
instead of 150-190 RRPM with which I start my normal Xenon
ground run.

It takes about 5 sec to reach 75kph and 300 RRPM on the ground
until I am supposed to take-off. Of course, if the engine quits
within those 5 sec, I am still ok, will just stop or short flare and stop.

If I jump, I hope to jump at least 10-15m up.

If the engine quits in the first second I will still have 10m alt,
and 400 RRPM to flare and land.
If it quits in the second second I may have just 300RRPM, 5m alt,
but at least some 20 kpm speed also to flare and stop.
And so on, every second the engine keeps running I will gain speed,
probably keep the altitude and keep the RRPM at flight level,
so all the time I will be able to flare and stop safely.

Of course it is another story doing a JTO in a confined area.

Eventually, also with a helicopter you do not go too high,
before gaining speed, if you don't have to, to be able to
autorotate and flare.

On the bottom line:
on JTO you have more energy stored (rotor + altitude + speed)
at any given moment than on normal take off (just rotor + speed),
to get you safe back to the ground...

...on the other hand at a normal take-off you are still on the ground. ;)
 

Vance

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Take off seems simpler to me in a gyroplane.

Take off seems simpler to me in a gyroplane.

Hello Paul,

In my opinion a gyroplane is a very simple device to take off compared to a typical conventional gear aircraft like a Stearman.

With the Stearman I can’t see where I am going, I watch for the speed to lift the tail, I have to be careful not to add too much throttle before I lift the tail, I am susceptible to crosswind gusts and have to manage the runway centerline that I can’t see and I have to initiate rotation at the correct indicated air speed. Once I am off the ground I have to be careful of my airspeed and select a V speed. Turns can be problematic because they exacerbate the tendency to stall and escalate the consequences. If the engine stops I have to get the nose down quickly to avoid a stall and aim for a runway I can’t see.

With the Predator when I am cleared to take off I release the rotor brake, richen the mixture, give her enough throttle to roll and press the pre-rotator button. At KSMX by the time I reach the centerline I am at 100 rotor rpm and go half back and soon I see 120 rpm and go full back. At 180 RPM I advance the throttle and somewhere around 40kts her nose comes up and at 45kts she waddles off the runway without my assistance. There may be a small course correction if it is windy and I didn’t manage my stick and rudder well. I have used up around 500 feet of runway. She will climb out nicely any indicated airspeed between 35 and 90kts. If I want to miss something the stick is all I need to manage it and I practice the engine going quiet on takeoff often. I simply pick a spot and land.

I have had the blades begin to flap on more than one occasion because I was rushing things or gusty winds and it was a non event. I simply get the stick forward and it stops. I don’t think I can flap the blades on lift off unless I try to rotate like fixed wing. If I let her lift off when she is ready things seem to work out.

I realize that a tricycle is simpler with better visibility but it still has the stall demon and requires cross controlling in cross winds. I still have to tell her when to lift off and pick a speed and stick to it. Engine outs on takeoff are often fatal in a fixed wing.

I can only imagine, read and listen to stories about a jump takeoff in a gyroplane because the Predator is not capable of a jump takeoff.

I would have trepidation because I don’t know what the wind is doing 40 feet in the air, it may not be favorable. We often get strong wind shear at 40 feet above the ground at KSMX. I don’t want the engine to stop because I don’t have enough airspeed to flair. To have the capability for jump take off I have added complexity and weight to the aircraft. To me it sounds like a poor tradeoff.

When I was learning to fly a gyroplane I was thinking of all the things to do in a helicopter and it added to the work load. Once I forgot about helicopters the simplicity of the take off process revealed itself to me.

I continually improve the subtleties of my takeoff in the Predator but the basics have remained the same for all gyroplanes I have flown.

Perhaps there is some unique challenge to the take off with the Xenon. I have not flown one but they look normal when I have seen them fly and they seem to have an adequate pre-rotator.

Thank you, Vance
 

ckurz7000

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Admittedly, I would really love to have jump take-off capability just for the kicks of it. But, flying fixed wings and gyros, I don't see much different at all between take-off complexity. In fact, particularly in a tail wheel airplane in a cross wind you have much more to balance just right than in your standard gyro.

In my gyro, the only thing I need to watch is to prerotate the rotor to above 200 rpm to be clear of any danger of blade flapping. Once you do that it's clear sailing, just like in a tricicly gear fixed wing. If you don't have a sufficiently powerful prerotator there is the added complexity of not feeding too much air through the rotor disk in order to keep the blades from hitting the teeter stops. But on the other hand, the engine out procedure is much safer, requiring less space to land or turn around.

-- Chris.
 
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brett s

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If I jump, I hope to jump at least 10-15m up.
Sitting at 15 meters & zero airspeed if the engine quits right as you jump you're going to land hard.

There's no "flaring" without airspeed & even with collective control that probably won't be pretty. Just like a helicopter in the same situation in fact...

You'd be better off with the much shorter jumps (5-10' max) everything but the Carter demonstrators typically get, or a jump to a couple hundred feet.
 

PTKay

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Vance,

as usual, very valid points.

Maybe my opinion is really biased.

I never flew a tail-dragger, spent most of my time on
Morane-Socata Rallye with automatic slats.

It was as forgiving regarding take-off speed, as a gyroplane:
if I rotated with speed too low, the slats would just pop out
and up we go, if the speed was to high, she would just
take off by herself not waiting for my rotation, just like a gyro.
Also a huge tail and powerful ruder gave her lots of authority
on cross winds.
(Accepted, as by manual, was 20knt crosswind component.)

And I never piloted a helicopter.

Brett,

you are right, either jump 100 feet, or not at all. :)

Chris,

maybe it is Raphael, who wants me to be on the safe side and
suggests rejecting taking off before certain speed is reached.

Keeping the nose down and speeding up by cross wind is not easy.
On the other hand taking off to slow and "mushing in" is also no fun.
 

Vance

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The most I have seen is a 50 foot jump.

The most I have seen is a 50 foot jump.

Vance,

I never flew a tail-dragger, spent most of my time on
Morane-Socata Rallye with automatic slats.

It was as forgiving regarding take-off speed, as a gyroplane:
if I rotated with speed too low, the slats would just pop out
and up we go, if the speed was to high, she would just
take off by herself not waiting for my rotation, just like a gyro.
Also a huge tail and powerful ruder gave her lots of authority
on cross winds.
(Accepted, as by manual, was 20knt crosswind component.)

And I never piloted a helicopter.

Brett,

you are right, either jump 100 feet, or not at all. :)

Chris,

maybe it is Raphael, who wants me to be on the safe side and
suggests rejecting taking off before certain speed is reached.

Keeping the nose down and speeding up by cross wind is not easy.
On the other hand taking off to slow and "mushing in" is also no fun.
Thank you for the kind words Paul,

I was told that the Scoata Rallye stalled at 50kts. Was I misinformed?

I wonder if Raphael is simply telling you not to rotate and let the gyroplane take off when it is ready.

In my opinion it only gets complicated in the explanation of why not rotate.

Explaining why any flying surface stalls including the consequences is complicated.

There are times I have intentionally taken off at less than 30kts just by allowing the rotor to come up to speed.

I don’t have a reason to make the gyroplane take off before she is ready so I don’t think about what would happen if I do.

In the Predator I don’t hold the nose down until we reach certain airspeed; I simply keep the tail wheel off the ground and she flies when she is ready. I seem to have adequate rudder to manage a takeoff in a strong cross wind.

The cross wind take off does slow the rotor acceleration.

It seems simple to me.

Is it different in Xenon?

As to your solution; as far as I know there has never been a gyroplane that would jump 100 feet in the air.

I don’t know how you would store that much energy in the rotor.

Typically with a jump take off gyroplane they over speed the rotor by 50 percent and then pitch the blades.

The highest jump I have seen was less than 50 feet leaving the aircraft in a precarious position if the engine should stop.

Thank you, Vance
 

Heron

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With the proper skill for the equipment at hand it is just a matter of choice. Without those, don´t mess with it . . .
You are thinking about when things go wrong and there is a difference, that asks for different actions.
After launch, it is impossible to abort a jump, the short roll can be restrained.
Heron
 

DennisFetters

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Go get some time in an 18-A and do a few jumps, and you will understand why it is not so easy and more risky.
 

birdy

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Paul, your just confusing yourself with over complicated annalisis. ;)
Gyros, same as any new machines, seem complicated and a strain on brain reserves wen you first start.
But once you tune in, you dont even think bout it.
Just prespin [ your feel will tell you wen to go], open the throttle [ feel will tell you how much], and istead of thinkn "push the stick forward as the nose comes up", think ", keep the stick level, no matter wot the nose dose".
IOW, fly the stick on TO, not the machine.

One point bout JTOs, if the collective is manualy fed in, instead of flickn a leaver/switch to go streight to autorotative pitch will give you much more control over how fast you burn rotor energy and how high you jump. Also gives you more options at the flair.
 

PTKay

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I was told that the Scoata Rallye stalled at 50kts. Was I misinformed?
In principle, yes, it's a misinformation.
The Rallye doesn't stall at all.
Iy behaves much like gyrocopter, that is, at critical speed the slats pop out,
and later the machine just sinks under full control, without any tendency
to spin. The ailerons are slated, the airflow on them
stays at high AoA and they retain full authority.
Huge Fowler flaps ad to the feeling. They give mors lift than drag.
Also the rudder is extremely effective.

So in general, you have something of gyro flying feeling,
without having to bother about rotor management,
especially on take off.
 

PTKay

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As to your solution; as far as I know there has never been a gyroplane that would jump 100 feet in the air.

I don’t know how you would store that much energy in the rotor.
Carter Demonstrator does, they have heavy tip weights to get
more inertia energy stored.

Typically with a jump take off gyroplane they over speed the rotor by 50 percent and then pitch the blades.

The highest jump I have seen was less than 50 feet leaving the aircraft in a precarious position if the engine should stop.
The "death triangle" is the same in helicopters, so nothing new,
and nothing more dangerous, but still a threat.
 

StanFoster

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In my opinion, if you are in a helicopter hovering at 100 feet at 0 mph, or in a gyro that just did a jump takeoff vertically to 100 feet expending all its extra rotor energy, if either loses an engine, both are in serious trouble. Stan
 

NoWingsAttached

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...With the Predator when I am cleared to take off I release the rotor brake, richen the mixture, give her enough throttle to roll and press the pre-rotator button. At KSMX by the time I reach the centerline I am at 100 rotor rpm and go half back and soon I see 120 rpm and go full back. At 180 RPM I advance the throttle ...I have had the blades begin to flap on more than one occasion because ...
i have been told to not be moving gyro unless the blades are spinning at least 100 RRPM. Sounds here like you are taxiing the entire time you prerotate, from zero to lift off. I am not the one to tell you how to fly, but this doesn't sound right from what little I know.

This is a recipe for a blade strike and disaster. Kids, don't do this at home.
 

Vance

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It seems to be working so far.

It seems to be working so far.

i have been told to not be moving gyro unless the blades are spinning at least 100 RRPM. Sounds here like you are taxiing the entire time you prerotate, from zero to lift off. I am not the one to tell you how to fly, but this doesn't sound right from what little I know.

This is a recipe for a blade strike and disaster. Kids, don't do this at home.
Hello Greg, Thank you for your admonition.

Last I looked at my log book I was well over 2,600 landings in The Predator and most of those is accompanied by a pre-rotation and a takeoff. Some are stop and goes.

I hit the rudder with the rotor once when the pre-rotator failed and I was crowding the blades on a short strip and hit a bump. I was almost half back at 60 RPM. It did very little damage and I flew her home after I repaired the pre-rotator.

Mark Givan, the designer of the Predator originally would hand start the blades from the back seat and then climb in to the front seat, buckle up and plug in. He looks strong but I doubt he can manage 100 rpm.

In the SparrowHawks and RAFs I have trained in we would stop on the runway and get the blades up to speed before proceeding.

My Toyota starter is very weak and I want to give it all the help I can.

I can’t hear the radio with the pre-rotator engaged so I feel particularly vulnerable when I am pre-rotating.

I am only rolling 10 to 15kts but it is not unusual to have a 20kt plus head wind making it 35kts of forward speed.

When I took off in a steady 50kt wind at King City I pre-rotated in place and kept adding power to keep from rolling backward.

I now keep the stick full forward until I see 100 rpm.

I would not suggest that I know enough to teach anyone anything about flying a gyroplane; I have only had my pilot’s license for a little over 3 years. I was reporting what appears to work in The Predator and asking if it was different in Xenon.

Most forum members know The Predator is one of a kind and peculiar.

Hopefully some more experienced gyroplane pilots will comment on their takeoff technique and what makes the Xenon so challenging for Paul.

Thank you, Vance
 
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