Timing is everything!

Mayfield

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My friend Vance Breese's wonderfully written posts about his flights and the recent posts about a forum member landing his gyro, inspire me to start this discussion.

Timing is everything.

How high do I flare? How fast?

It depends!

What is our job when we land?

Our job is to arrest our descent with such precision that our main wheels touch the ground, softly, with almost no ground speed or vertical speed.

We do this by managing the energy state of the aircraft.

I know there are many ways to look at this energy state, so bear with me while I go over a little primer.

Let's assume we are approaching touchdown at 60 MPH at a 500 FPM rate of descent. That's 88 FPS forward and about 8.3 FPS vertically.

Just a glance at those numbers tells us that we are doing a power approach in our gyroplane. It's about a 10 to one slope. If we were power off and maintained 60 MPH airspeed our rate of descent would be about 1320 FPM if we maintain a 4 to 1 slope.

In both scenarios, it's our job to “use up” the energy of our descent to zero out horizontal and vertical velocity just as the main wheels touch.

When we pull back on the stick we both change the rotor thrust vector and, albeit temporarily, increase rotor thrust. We begin to use up the energy stored in the system.

Although I would like to pretend I can zero out horizontal and vertical velocity at the same time, I don't think that's a reasonable expectation.

Which one do we zero out first? The vertical velocity of course.

How fast do we pull back on the stick? It depends!

If we have a really good sense of how the energy exchange between vertical rate and rotor thrust change happens, we can do an exquisitely gentle pull starting quite high, 20 feet or more, and stop the sink a few inches to a couple of feet above the surface. It is imperative we do the initial pull gently or we will level off too high or balloon.

If we made a powered approach, we can now slowly reduce throttle even further. As throttle is reduced your kinesthetic senses will detect sink toward the surface. Your job, at this time is to arrest that sink with increasing back pressure on the stick. You want to pull just quickly enough to maintain the few inches of altitude as airspeed bleeds away.

If your timing is good you will run out of back stick and ground speed just as the main wheels touch. It's actually not very important if you have a little engine power still applied. The rapidly increasing drag has put you so far behind the power curve by now that the aircraft will land. If throttle is still applied at this time, reduce throttle to idle.

A power off approach is only different in that you need to arrest a greater descent rate. The flare may start higher, but still gently.

Now the disclaimers.

The “numbers” above are approximations. If you choose to apply any of these procedures, I encourage you to engage the many fine instructors on this forum. Flesh out and discuss these concepts. If we disagree, we can be civil.

I am absolutely not disagreeing with anything your instructors have taught you. They know you, your equipment, your skill level and aptitude.

The above paragraphs provide very broad-brush strokes.

I hope we can discuss "landing the gyro" and maybe get a little out of the discussion.

I have used several hundred words to say “Pull back on the stick just fast enough to level off. Continue back pressure at a rate that will maintain your altitude as airspeed bleeds away until the aircraft can't stay in the air.”

Jim
 
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TyroGyro

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On my test I employed my "freestyle" landing technique.

I am a very "gentle" pilot, who shies away from large inputs. Not always a good idea, I admit. Occasionally, large inputs are DEFINITELY required.

On the other hand, waiting.... - doing nothing - until that large input IS required, can be stressful, with risk of mistiming and over/under-doing it.

So, on my test, after the first roundout input, and the start of the float ,I would simply...

"check the nose", with maybe a half-inch slight rearward movement of the stick, pulsing about once a second.

I was doing something, slowing down while at about 2ft, ready to give that final LARGER impulse as I felt the gyro run out of energy and sink.

I was cheeky-enough to ask my examiner, as he was deliberating my future. "By the way, did you like my freestyle landing technique?"

"It certainly works !"
was his response as he gave me a pass....
 
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Vance

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Nicely written Jim and a goal to aspire to.

I hope readers will think about what you have written because they are the fundamentals of landing a gyroplane.

I start as Terry did teaching power on landings so the timing is less critical.

It is much easier to fix a power on landing that is not going well than a power off landing where they run out of airspeed before running out of altitude.

Because of the power-pitch-yaw coupling in many of the gyroplanes I have them stick with whatever the throttle setting is at twenty feet.

As I was preparing for my CFI practical test I found starting with power off landings impractical with most of my practice students.

Most of my clients still resist the transition to power off accurate landings and I am glad it is a practical test standard or I might not get them there.

Carburetor ice on the O-290 turned many of engine at idle landings into actual engine out landings in The Predator.

My advice to people who aspire to a Mayfield landing is to work up to is slowly and gradually.

I was pleasantly surprised that it worked out so well when I tried it yesterday despite having over 3,000 landings in my logbook.

I did not reach the aft stop; the touchdown was gentle and near zero ground speed.

Since I have become a flight instructor I have done fewer power off zero roll landings because I don’t want to set a bad example.

It is much easier to fix a power on landing that is not going well.

I am pleased when my clients can exceed the standard for engine at idle accurate landings and they usually have some speed when they touch down.

I may be at a disadvantage with my monocular vision and my compromised inner ear.
 
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Mayfield

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Thanks Vance, but as much as I appreciate the compliment it is certainly not a "Mayfield" landing.

It is simply the way to land a gyro as safely as possible. As you have surmised, it is easier to time the flare in a power on approach. Indeed, with a moderate headwind you will either need a little power at, or immediately after, touchdown to prevent rolling backwards unless you level the disc right away.

The stick reaching the back stop is aspirational for me. It's exactly the same as my aspiration when I'm driving my old Hatz, a C-152, my current Gobosh 700 or a gyro.

Once I level off and gently raise the nose to the landing pitch attitude, I strive to maintain that attitude until the aircraft simply doesn't have the energy to stay in the air any longer.

If I have done my job correctly the aircraft settles in from whatever altitude remains; hopefully a few inches, and the touchdown is almost unfelt.

Jim
 
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Gyro-nut

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I may not have the experience of 98% of the folks on this forum, but I think there's a time and a place for both power on and power off landings... and you should have both in your bag based on the situation.

I was trained by Gary Goldsberry in a Twinstarr. All landings early on in the training were power on (understandably). As I progressed in my skill level, they became closer and closer to idle but never at idle.

Once I started flying my tiny 447 air command and increased my confidence, just about all I ever did was idle landings. It's takes a bit of practice, but it sure came in handy the day I had an engine failure and had to put it down in a corn field (luckily, the corn was not very tall yet). Zero forward speed about 6" above the ground and dropped it in... no damage to the machine or pilot and the only damage to the crops was where the gear was sitting (well... and the trail from dragging it out :()

I still remember the first time when I actually touched the mains with no roll and didn't realize it had touched down (apparently coined the Mayfield landing)... unfortunately, it's never been repeated. LOL
 

Tyger

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Let's assume we are approaching touchdown at 60 MPH at a 500 FPM rate of descent. That's 88 FPS forward and about 8.3 FPS vertically.

Just a glance at those numbers tells us that we are doing a power approach in our gyroplane. It's about a 10 to one slope. If we were power off and maintained 60 MPH airspeed our rate of descent would be about 1320 FPM if we maintain a 4 to 1 slope.
I like your posting, but with regard to the above, it seems like you are equating "forward" velocity with the horizontal component of that velocity (which are clearly not the same during a descent).
 

WaspAir

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Pythagoras says with an 88 fps descending hypotenuse and vertical speed of 8.3 fps (500 fpm), the horizontal leg is 87.6 fps, not terribly different. In computing the glide ratio, it's a question of 10.56:1 vs. 10.51:1. The angle is less than six degrees (compare with 3 degree VASI slope).

(You can use 5280 fpm, 500 fpm, and 5256 for the same result).

Trigonometry can be pretty indifferent to one's ordinary intuition.
 
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Tyger

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OK but that's at the 10:1, "power-on" ratio. How about redoing those numbers at a 3:1 gyro-glide ratio, in that power-off descent to land?
Then it's more like a 16% difference between forward and horizontal speed, no?
 
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WaspAir

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At 60 mph indicated (hypotenuse) and 1320 fpm power off vertical descent rate (as suggested by Mr. Mayfield), the horizontal speed is 5112 fpm. The difference in glide ratio using sloping airspeed vs. horizontal speed is 4:1 vs. 3.87:1. The angle of the glide is about 14 degrees.

At a true 3:1 with 60 mph indicated on the hypotenuse, the horizontal speed is 5010 fpm or about 57 mph (not a 16% delta). The glide angle is about 18 degrees, with sink rate 1670 fpm. Using IAS would suggest 3.16:1 instead of 3:1.

A 16% speed difference would require over 30 degrees slope, or a ratio of 1.7:1 (parachute or space shuttle territory).
 
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Mayfield

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Thanks Tyler, Jon and Vance for looking at this thread again. Your discussions may help folks improve their landing procedure or at least bring it to mind for study and reflection.

Although not a panacea, understanding the importance of touching down at minimum ground speed can't be overstated.

Jim
 

Mayfield

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OK but that's at the 10:1, "power-on" ratio. How about redoing those numbers at a 3:1 gyro-glide ratio, in that power-off descent to land?
Then it's more like a 16% difference between forward and horizontal speed, no?
I am not very good at much beyond basic arithmetic Tyler, but my methodology was to think of it as a right triangle. Side a was 22 FPS (1320 FPM), side c was 88 FPS. That gave me side b (horizontal along the ground) 0f about 85 FPS and an approach angle of a little over 14 degrees.

Since I haven't looked at basic trig functions in more years than I care to think about, I used one of the online trig calculators.

If I made a fundamental error, I hope you or Jon will fix it.

Jim
 

Tyger

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Jim, I think your analysis is very good; such landings are something to aspire to, as Vance has said.
WaspAir has demonstrated that the difference between forward and horizontal speed is de minimis.
I confess to usually landing with a bit more forward speed than I would like, but to me that's immensely preferable to running out of energy when I'm still a couple of feet in the air. Happily, having some really good brakes (by Beringer!) helps kill any residual forward speed very quickly once all my wheels are on the ground.
I recognize that some folks here see landings at anything more than minimal forward speed as inelegant, but I do think they have their place, particularly on days when winds gusts are large and unpredictable.
I do wish I were better at doing landings as you describe them. On the other hand, I've done over 1500 so far, without screwing up most of them too badly. 🙃
 

Mayfield

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I recognize that some folks here see landings at anything more than minimal forward speed as inelegant, but I do think they have their place, particularly on days when winds gusts are large and unpredictable.
Absolutely Tyler. Although I aspire to always doing minimum energy landings, I also understand that the PIC must make the decision, appropriate to the total environment, for all phases of flight. Perhaps "Minimum energy commensurate with the conditions" more accurately describes my thoughts.

Jim
 
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