Magni M24 Orion May 30, 2023 - Dauphin Island Alabama

[chrisk]

I can just assure you test flying and gathering data for POH to get glide ratios using sensitive altimeters and stop watches with many Rotax 9 series engines. Most of the time I got better glide with engine at idle.

This does not surprise me. Try standing behind an idling gyroplane. That wind you feel is thrust. That said, above a certain air speed, the prop would be driven, instead of driving and start causing drag.

And I'm wondering if you might comment on rudder authority with no power vs an idling engine. My experience is a reduction in authority is noticeable the closer you get to a zero speed landing.

 

[Abid]

This does not surprise me. Try standing behind an idling gyroplane. That wind you feel is thrust. That said, above a certain air speed, the prop would be driven, instead of driving and start causing drag.

And I'm wondering if you might comment on rudder authority with no power vs an idling engine. My experience is a reduction in authority is noticeable the closer you get to a zero speed landing.

Yes you are correct about it. The speed I use for approach is around 50 - 60 knots and there is residual thrust at that speed I believe.
The rudder authority of course reduces with low airspeed. In such cases gyroplane pilots should use a little power on approach but when you are truly dead sticking the gyroplane, that isn't possible so a faster approach speed a bit helps but as you flare you need to be already aligned and set up because rudder authority will disappear.
In AR-1, we did a very large rudder and the throw is 45 degrees so rudder does remain effective way down into the speed range but as always nothing is free. That comes at a cost of a heavy rudder pedal at faster speeds. I decided to redesign the tail in 2022 and reduce the size of the rudder with a shielded horn with weight in front of hinge line to make the rudder have less resistance. It is still larger than most gyroplanes in production but probably 40% smaller than previous rudder. The throw is still 45 degrees. In contrast for example, MTO Sport rudder is only 25 degrees and 29 degrees throw with a smaller rudder and the tail is 14 inches closer to the prop compared to AR-1.

 

[PJB]

so in terms of the distance of said float as it relates to this accident we are saying it would have made a difference?

 

[Abid]

so in terms of the distance of said float as it relates to this accident we are saying it would have made a difference?

It would but in this accident I am told the engine quit completely. I do not know why it did that. I would certainly like to know. Rotax included wiring harness uses that stupid Gafer tape on the wiring harness. That thing protects absolutely nothing against chafing anbd makes troubleshooting harder and hidden and I cannot believe EASA has allowed certification with that.

 

[PJB]

How high was he when the motor stopped??

 

[Doug Riley]

Wandering back to gliding at idle vs. ignition-off: It really does depend on the prop specs and the idle speed. A prop only makes (forward) thrust if its slipstream is faster than the surrounding freestream. If its slipstream is slower, then it makes backwards thrust a.k.a. drag.

I've flown gyros in which an idling engine stretches the glide, and others in which it doesn't.

In my teaching days, I made a point of doing an ignition-off landing with each student. I also do them myself rather often. At the rural airports around here, the risk of doing so is less than it would be at busier fields.

You should not do ignition-off landings until you've verified that rudder control still exists without prop blast over the tail. I'm told that some gyros lose rudder control ignition-off.

An engine-out glide is quite pleasant in a gyro, once you get used to the outrageous deck angle. It's quiet, and naturally there are fewer controls to manage. I take my hand off the throttle and put it in my lap, to avoid reflexively pushing it and expecting something to happen.

 

[EI-GYRO]

How high was he when the motor stopped??

Allegedly at altitude, but I'm guessing about 10 feet while flying low and slow and being filmed by a friend in a car. I'm a bit of a skeptic. I can't help it.

 

[Resasi]

A prop only makes (forward) thrust if its slipstream is faster than the surrounding freestream. If its slipstream is slower, then it makes backwards thrust a.k.a. drag.

There is a point at which an engine is at an idle thrust setting that creates neither drag nor thrust, this power setting known as 'zero thrust'. It is a factor of importance in multi-engine operations due to the significance engine failure plays in asymmetric flight after an engine failure. However in most, though not all multi-engine aircraft, fully feathering props are the norm. It is still however a factor as the possibility of the feathering mechanising failing.

I had such a case in a Twin Comanche doing an Instrument approach in actual conditions into El Paso when I had a runaway prop on the 'critical engine', this being an early model before contact rotating props were incorporated into the line. The air charge in the feathering system developed a sudden leak as we were on the localiser and had just hit the glide slope, the power reduction suddenly triggering the leak and resulting in the blades on the left engine going to fully fine pitch.

 

[knussear]

There is a point at which an engine is at an idle thrust setting that creates neither drag nor thrust, this power setting known as 'zero thrust'. It is a factor of importance in multi-engine operations due to the significance engine failure plays in asymmetric flight after an engine failure. However in most, though not all multi-engine aircraft, fully feathering props are the norm. It is still however a factor as the possibility of the feathering mechanising failing.

I had such a case in a Twin Comanche doing an Instrument approach in actual conditions into El Paso when I had a runaway prop on the 'critical engine', this being an early model before contact rotating props were incorporated into the line. The air charge in the feathering system developed a sudden leak as we were on the localiser and had just hit the glide slope, the power reduction suddenly triggering the leak and resulting in the blades on the left engine going to fully fine pitch.

That sounds about as fun as waking up in a snake pit!

 

[Resasi]

You're right! An approach in full IFR conditions is a somewhat higher stress than a normal VFR approach, and an engine failure during that event period does tend to require one's full attention...which is why it occurs a lot during sim recurrent training.

Luckily I was higher than the gents in question on the thread...and had another engine. The point is that in a twin you haven't just lost 50% of your available power, but have also incurred a fairly substantial weight and drag issue.

In this case rapidly reducing the power lever on that engine then gives you a limited opportunity to limit engine RPM, over-temping, and excessive drag. It now poses problems the event of any possible missed approach, and climb procedures.

So in this case here it makes the intended approach and landing somewhat more critical than would otherwise be the case.

In the case being discussed it seems he had no alternative and was going down and it was perhaps the lack of a optimal stop and drop landing that caused his nose wheel to catching, and then dragging the nose down hard.