.

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
2,349
Location
Centre FRANCE
Aircraft
I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
In this situation, you can still increase the number of blades and so you will have more thrust with more power input
 

Abid

AR-1 gyro manufacturer
Joined
Oct 31, 2011
Messages
4,400
Location
Tampa, FL
Aircraft
AR-1
Total Flight Time
4000+ 472 gyroplanes. Sport CFI Gyro and Trikes
I've been building, flying and selling 145-165HP normally-aspirated, factory stock, carb & FI gyro engines that weigh 20 - 28 lbs less than the Edge turbo 912 since 2012. What's all the fuss? 10,000+ fleet hours, not a single engine-out in all of our 9 years.

My personal gyro is a 570 lb (DW) carbbed 145 HP Air Command Yamaha that I first flew November 2012, 9 years ago.
Relax.

Nuttin' to worry about, just be careful on those super-steep climbs, they require lots of rudder authority; work up to them like a race car driver works up to going 200 mph on the track, and throttle back when rolling out at the top of a climb.

Take-off and powering out of downwind turns is a dream. Once the nose comes up go full throttle and literally launch. None of this pushing the nose over and gaining AS nonsense before going climb, although when you're getting used to it it's better to continue going with that method for a while.

This Air Command tandem has a TOW of 795 lbs. with 1 hour of fuel and 200 lbs pilot w/ gear.

2021 Mohawk Aero YG4 Grass Field Take Off


If this is 145 HP and you are only at 795 lbs Takeoff weight then Rotax 915iS must be 165 HP just going by what I am seeing here. In other words, I don't think you are using anywhere close to 145 HP in this video at any point in my estimation. Also, the so called 160 HP Subaru powered gyroplanes, they certainly do not come anywhere close to the performance I see from a 915iS powered modern gyroplanes possibly because of power to weight or more likely (since I know the weights of a Dominator with such an engine I flew in) possibly because they are really never creating 160 HP at all. They just claim to.
 
Last edited:

N962GT

Newbie
Joined
Oct 25, 2020
Messages
69
Location
Northville, Michigan
Aircraft
Mohawk Arrow 140T
Total Flight Time
800 hrs
If you have horsepower to spare, a more wholesome way to use it is to employ a partial rotor drive, as Dick Degraw does.

The problem with putting excessive power to a propeller is that it leaves the rotor with nothing to do. That is, in a full-power climb, the prop supports a significant part of the weight of the gyro. This reduces the angle of attack of the rotor disk, much like cutting the string of a kite. The rotor responds to the lack of load* by slowing down. Then, at the top of the climb, when you again apply the gyro's full weight to it, you are risk for destructive flapping (retreating-blade stall).
__________________________________
* A rotor can't sense load directly. Instead, it reacts to disk angle of attack. When we say we "unload" a rotor, we mean that we reduce the rotor's disk angle of attack. We do that on purpose upon landing -- we push the stick forward. Some pilots refer to this as "killing" the rotor, a pretty apt term. Don't kill your rotor in flight; it just might return the favor.
Although this may seem reasonable it is wrong. I have NEVER experienced a SLOW ROTOR while doing extremely steep, sustained climbs with my YG4 in 9 years of doing so, and I do them 9 out of 10 times I fly, so many hundreds of hours flying with 5.44 - 5.8 lbs TOW per HP.

Air speed is air speed, regardless. If what you are saying were true then Barry Thigpen would never be able to loop that Dominator of his like we saw him do a few weeks ago (Youtube video) here above August, GA.

Maintain proper minimum AS and the rotors continue to spin at plenty of RRPM regardless of how much weight is carried by a high HP prop in a steep climb.

I will put a camera on the rotor tach and do a climb to prove it.

Reducing power at the top of steep climb to "roll out" is the only safe, reasonable way to fly, and was already mentioned, gyro rolls and double rolls excepted for the wild stunt pilots among us.
 

Vance

Gyroplane CFI
Staff member
Joined
Oct 30, 2003
Messages
17,156
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
The Predator has a Lycoming IO-320 rated at 160 horsepower. In a steep climb at 50kts she is likely around 2,400 engine rpm and making closer to 140 horsepower.

I have found reducing the weight the rotor sees reduces the rotor rpm.

In The Predator with an all up weight (1,400lbs) I typically see around 345 rotor rpm in straight, level un-accelerated flight. Solo with a light fuel load (1,100 pounds all up weight) reduces the rotor rpm to around 310 rotor rpm in straight and level un-accelerated flight.

In a full power steep climb at fifty knots indicated air speed I have seen the rotor rpm fall to less than 280 rotor rpm solo with a light fuel load. The minimum I would like to see is 270 rotor rpm so I keep an eye on it in a steep climb.

I have found indicated air speeds from 20kts to 100kts have little effect on rotor rpm in The Predator.

I reduce power at the top of a steep climb to maintain airspeed.
 

Attachments

  • 08.JPG
    08.JPG
    225.9 KB · Views: 1

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
2,349
Location
Centre FRANCE
Aircraft
I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Although this may seem reasonable it is wrong.

Air speed is air speed, regardless. If what you are saying were true then Barry Thigpen would never be able to loop that Dominator of his like we saw him do a few weeks ago (Youtube video) here above August, GA.
it seems to me you are forgetting two points:
1) it takes a bit of time for the rpm to change with rotor load, due to the rotational inertia of the blades: 3 to 5 s are needed to close 2/3 of the gap with the steady Rrpm.

2) The rotor load during the vertical climb of a loop is far from zero. It is worth Mgyro*Vf^2 / R (R being the local radius of the loop).
 
Last edited:

NJpilot

Gold Supporter
Joined
Aug 19, 2012
Messages
161
Location
Voorhees
I'm looking forward to electric power where it's easy to distribute power across 2 or more props eliminating torque issues.
 

Doug Riley

Platinum Member
Joined
Jan 11, 2004
Messages
6,713
Rotor RPM is a function of (1) rotor disk angle of attack and (2) airspeed. You need both to be non-zero numbers for the rotor to continue spinning.

As Jean Claude points out, the vertical part of a loop is not a straight line, but a segment of a (vertical) circle. Continuous rotor thrust is require to keep the vertical portion curved; without rotor thrust, the flight path will curve out-and-down, not in. IOW, the rotor is busy making centripetal force to maintain your circular flight path.

If you somehow had enough prop thrust to lift the entire weight of the gyro, you could fly straight up with the nose vertical, like a space shot. To stay on your straight-up path, you'd need to hold the rotor at zero disk AOA; otherwise the rotor would pull you out of your vertical path. In such a vertical flight in such a gyro, the rotor would slow down for the same reason that it will slow down on the ground if you level the disk.

A high level of prop thrust (but less than 100% of gross weight) will allow you to execute a straight-line, steep climb -- but if it's really going to be a straight line, less rotor thrust will be required. This means low disk AOA and lower-than normal RRPM.

You can maintain a larger disk AOA and RRPM, even in a high-thrust gyro, by gradually pulling the stick back during the high-power climb, or by banking as you climb.

But there's no escaping the arithmetic -- if prop thrust is supporting a significant part of the gyro's weight, you need less thrust from the rotor to maintain a straight flight path. That means lower disk AOA, and lower RRPM, at a given airspeed.
 

GyrOZprey

Aussie in Kansas.
Joined
Aug 8, 2011
Messages
3,129
Location
Whitewater KS
Aircraft
Butterfly Aurora N5560Z / Titanium Explorer N456TE & N488TE/ - trained in MTOsport 446QT/488FB
Total Flight Time
936
Too much HP power in gyros ...in the hands of the low-time gyro pilot...(even high-time FW pilots WITHOUT solid understanding of rotor loading /unloading & rotor management) ...HAS in the last year proven to be disastrous ...just look at the # of accidents involving 915powered gyros!

traditional teaching - learning rotor management & managing available power with lower HP engines ...has built some solid gyro pilot skills! ( Those pilots with substantial gyro time are respecting & ENJOYING their 130-160 HP power plants ...so far safely & without problems!)

Even highly experienced pilots can be fooled ....and goosing a high HP engine during a TO roll that is not going to plan (gusting X-wind resulting in an erroneous raising the nose wheel ...& no rotor tach to double check Rrpm) .....RESULTS in sickening noises & flying tail/prop parts!:eek::cry:
 
Top