Ground effect in a gyroplane?

fara

AR-1 gyro manufacturer
Joined
Oct 31, 2011
Messages
3,459
Location
Tampa, FL
Aircraft
AR-1
Total Flight Time
3600+ .. New to gyroplanes
Xavier,
We have to compare the benefit to the power required OGE on the engine shaft .
Parasit drag 175 N (if S*Cd = 0.7)
Rotor drag 1020 N OGE
Total 1195 N OGE

Power on engine shaft = 1195 N * 20.1 m/s /0.6 = 39.8 kw
Hence a benefit of 8 %.

Now, I did this evaluation for a Cessna 150 (700 kg) at the same speed (flaps down) when the wheels are almost touching the ground (z/b = 0.19)
I get an benefit of 40% (assumed parasit Cd =0.5 included wings)

I think that's in the ball park. Nick Lapos states 8 to 10% in GE in autorotation as well
 

Martin W.

Active Member
Joined
May 10, 2020
Messages
186
Location
Winnipeg
If the trailing edge were to rub on the ground, so that air could not escape under the horizontal stabilizer, then the dynamic pressure (1/2 Rho V2) applied over the entire bottom surface would give a maximum of 250 N at 45 mph.
But the air is in reality never completely blocked and adding the leaks at the ends, I can't reasonably imagine this lift to be more than 100 N, which is still "negligible".

A bit off topic with a pinch of humor .... years ago I talked to a fixed wing pilot who had a landing gear malfunction (right gear would not come down) (he knew it would loop and maybe cartwheel ) so he elected to raise all his wheels and do a belly landing at his airport which damaged all the aluminum on the lower fuselage but otherwise intact.

He was a great pilot but an excitable french-canadian who had all the appropriate body language and arm movements as he told the story ... funny as heck to listen to .... .

He asked the firetrucks to lay some foam on the runway to prevent sparks and fire. He said he did a perfect approach , engines off , no wind , but overshot the foam halfway down the runway .... he said at 2 feet above the surface his wings were in full ground effect and "it refused to land where it was supposed to " ... "but I only scratched the bottom" (his words) ... we roared with laughter ... and of course we nick-named him "scratch"

I saw him again about 25 years later , he was about 66 years old and he was flying a 1000hp Dromader crop sprayer ... before I could say "hello scratch" he held up his hand with a stern look on his face and said "I dont scratch the bottom no more" .... "only this way now" .... then he reached around to his arse and gave it a vigorous scratch ..... another room full of laughter .... true tales from the pilots lounge ... where ground effect affects everyone differently.
 

bryancobb

Junior Member
Joined
Aug 2, 2010
Messages
5,041
Location
Cartersville, GA
Aircraft
Owned Brantly B-2b/Fly Kitfox III/Mini-500b
Total Flight Time
1350
My daughter went to SpaceCamp in Huntsville. When visiting once, I took note of one of Wernher Von Braun's quotes that was framed on the wall.
He said "One test result is worth one thousand expert opinions."

Now Vance has done a controlled test and has consistent results. I believe in what he found. We may never be able to explain it to our desired level of satisfaction, but it is accurate and true.

Some of you know that I am a ZERO hour gyro pilot. But aerodynamics and the physics of lifting a machine and occupants in any type of aircraft is SUBSTANTIALLY SIMILAR so I feel I am at least a tiny bit qualified to comment.

Here is what I see as agreeable pertaining to being in ground effect (below 1/2 rotor span) in gyros (at constant speed and power).
* The machine with occupants is a LOT heavier than air and MUST be deflecting a large amount of air downward for it to remain airborne.
* Airflow upward through the rotor only needs to be enough to act on the driving region of the blades to sustain adequate RPM.
* Vance has unequivocally demonstrated that "adequate RPM" is lower during an IGE pass than during an OGE pass in a gyro.
* Amount of lift needed to sustain flight at 3 feet and at a given speed, is equal to lift at 30 feet.
* If a gyro at 3 feet uses less energy to spin the rotor than one at 30 feet, that extra "3' energy" can be used to deflect more air downward.
* More air deflected downward at 3 feet than at 30 feet explains why the rotor then "self-regulates" and lowers its RPM until Lift=Weight.

Is this a plausible explanation?

I still have questions about how the total energy in the incoming air is used or wasted. Let's say hypothetically, the rotor system is published to be 75% efficient. Where is the 25% of wasted energy in the airflow consumed. Well some gets eaten-up by profile drag and parasite drag of the machine and some more gets consumed by the stalled (inner portion) of the rotor disk. Tip vortices chow-down some energy. The propeller eats up a little more and several other "consumers" I'm sure I haven't thought of take their toll. In reality, the 75% efficiency rating is an average. I would guess that efficiency goes way up IGE. Vance has proven that most of these decrease at least moderately IGE.

Induced drag (drag created by the production of lift) is equal at 3 feet and 30 feet because lift needed is the same. Now the usable 75% ave. can be divided as needed to keep lift constant.

Like I said, I still have questions in this area, but like Von Braun said in so many words, I understand and trust Vance's TEST RESULT.

Good Job Vance.
 

XXavier

Member
Joined
Nov 13, 2006
Messages
1,267
Location
Madrid, Spain
Aircraft
ELA R-100 and Magni M24 autogyros
Total Flight Time
664 gyro (Nov. 2020)
(...)
(...)

I still have questions about how the total energy in the incoming air is used or wasted. Let's say hypothetically, the rotor system is published to be 75% efficient. Where is the 25% of wasted energy in the airflow consumed.

(...)
(...)

100% of the mechanical energy delivered by the propeller during a flight, with the aircraft (any type of aircraft) returning to its starting place, ends up as an increment of the temperature 'of the surroundings'.
 

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
2,136
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)
Bryan,
When Verner Von Braun talked about testing, it wasn't about the vague sensations of the pilot, but about measurements carefully recorded for analysis. And when he talked about expert opinions, these were only opinions, not calculation results.

The pilot's observation that his rotor tachometer at the moment of take-off, when the gyro is still in ground effect, is lower than the value measured a few seconds later when the gyro is out of ground effect, is true. However, ground effect is not in question, only the delay required for the Rpm acceleration:
Steady, there is only 1/2 rpm less because smaller angle of attack, the axial rotor thrust is very slightly lower to carry the same weight.

I desagree with your statements
* If a gyro at 3 feet uses less energy to spin the rotor than one at 30 feet, that extra "3' energy" can be used to deflect more air downward.
* More air deflected downward at 3 feet than at 30 feet explains why the rotor then "self-regulates" and lowers its RPM until Lift=Weight.


To spin the rotor the same energy is needed at 3 feets as at 30 feet. This is just required by the profile power, and it comes from the flow of air through the disk, as a wind mulle (Usually 3.5 m/s * S disk, giving the power of: Axial force * 3.5 m/s)
With no profile loss, no airflow crossing the disk required for to spin the rotor, at 3 feets as at 30 feets, and the A.o.A disc is only due to the need of downward deflection. So, A.o.A at 3 feets is lower due to the lower downward deflection.

* Induced drag is equal at 3 feet and 30 feet because lift needed is the same.
When the lift is the same, proximity to the ground reduces the induced speed. For the Xaviers' ELA at 45 mph the induced speed is 1.45 m/s OGE and only 1 m/s IGE. So, with the same airflow through the disk, A.o.A not need to be as large and therefore the induced drag is lower IGE than OGE.
Sans titre2.png

Sans titre4.png
 
Last edited:

Resasi

Gold Supporter
Joined
Jul 2, 2007
Messages
7,902
Location
London/ Kilifi Kenya
Aircraft
Gyrs, RAF 2000/Mgni/Bnsn/Hrnet/Mrlin/Crckt/MT-03/Lyzlle AV18-A/Prdtor. Pax ArrowCopter
Total Flight Time
100+ gyro, 16,000+ other
This circular merry go round about ‘ground effect’ is isn’t, reminds me about the saying...

‘It has been calculated that it is impossible for a bee to fly.’

The fact remains, that it not only flies, but produces honey as well.
 

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
2,136
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)
Leigh,
Forget that saying. This bad calculation has just never been presented.
 

Resasi

Gold Supporter
Joined
Jul 2, 2007
Messages
7,902
Location
London/ Kilifi Kenya
Aircraft
Gyrs, RAF 2000/Mgni/Bnsn/Hrnet/Mrlin/Crckt/MT-03/Lyzlle AV18-A/Prdtor. Pax ArrowCopter
Total Flight Time
100+ gyro, 16,000+ other
Gentlemen, your comments prove my point admirably.

A lot of hotly disputed discussion about something that exists, and which should be enough for its practicality to simply be utilised.:)
 

Greg Vos

Active Member
Joined
May 26, 2019
Messages
351
Location
Cape Town
Aircraft
R44/22 H269/300 MD 500 Magni (all); Xenon RST; DTA; ELA; MTO
Total Flight Time
2480 odd (1300 gyro hours & counting)
Jerry is a 100 hour gyroplane pilot and a 20 hour gyroplane flight instructor.
He is a fixed wing and helicopter flight instructor too.
Raul and Jerry were both very generous and cordial with their time despite our divergent opinions.
How does a person become a gyro flight instructor with only 100 hours of stick time in a gyroplane? Sorry off topic but I’m curious? Or is it a typo?
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,361
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
How does a person become a gyro flight instructor with only 100 hours of stick time in a gyroplane? Sorry off topic but I’m curious? Or is it a typo?

From my memory of my conversation; Jerry was a Helicopter flight instructor and added on the Sport Pilot Gyroplane CFI. I asked him about his hours and that is where the 100 hours came from. I suspect it is a rough estimate.

To become a Sport Pilot Gyroplane Instructor with the FAA you need to fly and teach to practical test standards in a gyroplane.

It requires a sign off from a gyroplane flight instructor to take the check ride and a successful proficiency check ride with a sign off from a different flight instructor.

I signed off a fixed wing sport pilot flight instructor as a Sport Pilot CFI Gyroplane the day after I signed him off for Sport Pilot, Gyroplane. He had around 21 hours of gyroplane experience. He easily met the standards and was able to manage me as a recalcitrant student taking the controls at the appropriate times and providing appropriate guidance.

I think he will be fine.

It takes a Designated Pilot Examiner to give a primary student a practical test.

It takes a DPE to give a check ride for an initial CFI.

I have flown with some Certificated Sport Pilot Gyroplane Flight Instructors who in my opinion were not qualified.

I have flown with some certificated sport pilots who in my opinion could not pass a proficiency check ride with me.

In my research I have found that all levels of gyroplane flight instructors were the primary flight instructors for accident pilots and based on their number of students no one appears to me to be over represented.

All of this is spelled out in part 61 of the Federal Aviation Regulations.

I often call my Flight Standards District Office for an interpretation of the regulations.
 
Last edited:

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
Messages
4,978
Location
Colorado front range
Aircraft
Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
Total Flight Time
stopped caring at 1000
From my memory of my conversation; Jerry was a Helicopter flight instructor and added on the Sport Pilot Gyroplane CFI. I asked him about his hours and that is where the 100 hours came from. I suspect it is a rough estimate.
The FAA website reports Jerry Higman as:
Ratings:
COMMERCIAL PILOT
AIRPLANE SINGLE ENGINE LAND
AIRPLANE MULTIENGINE LAND
ROTORCRAFT HELICOPTER AND GYROPLANE
INSTRUMENT AIRPLANE AND HELICOPTER
and
FLIGHT INSTRUCTOR
AIRPLANE SINGLE ENGINE
ROTORCRAFT HELICOPTER AND GYROPLANE
INSTRUMENT AIRPLANE AND HELICOPTER

Those appear to me to be the full ratings, not Sport Pilot limited. In contrast, Raul Salazar is reported with :
Ratings:
PRIVATE PILOT
ROTORCRAFT HELICOPTER AND GYROPLANE
and
FLIGHT INSTRUCTOR
SPORT

If one already holds the full commercial helicopter rating, the commercial gyroplane rating is merely a class add-on to those privileges, requiring demonstrating proficiency (to the published standards) to a DPE or Inspector in a formal checkride, but without any minimum number of hours in the gyroplane class (61.63(c)(3) and (4)). I did that long ago with less than 9 hours of total gyroplane experience. To add the full gyroplane instructor rating to a CFI certificate with helicopter rating, one must hold a commercial rating in the the gyroplane class and also have 15 hours as PIC in that class per 61.183(j), and then pass the practical test. Thus, the total gyro hours for adding both the commercial and full CFI-gyro ratings can be very low for a competent helicopter CFI. I had only 98 hours in gyroplanes when I passed my CFI-gyro checkride about 30 years ago, and I could easily have done it sooner with fewer hours.
 
Last edited:

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,361
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
The FAA website reports Jerry Higman as:
Ratings:
COMMERCIAL PILOT
AIRPLANE SINGLE ENGINE LAND
AIRPLANE MULTIENGINE LAND
ROTORCRAFT HELICOPTER AND GYROPLANE
INSTRUMENT AIRPLANE AND HELICOPTER
and
FLIGHT INSTRUCTOR
AIRPLANE SINGLE ENGINE
ROTORCRAFT HELICOPTER AND GYROPLANE
INSTRUMENT AIRPLANE AND HELICOPTER

Those appear to me to be the full ratings, not Sport Pilot limited. In contrast, Raul Salazar is reported with :
Ratings:
PRIVATE PILOT
ROTORCRAFT HELICOPTER AND GYROPLANE
and
FLIGHT INSTRUCTOR
SPORT

If one already holds the full commercial helicopter rating, the commercial gyroplane rating is merely a class add-on to those privileges, requiring demonstrating proficiency (to the published standards) to a DPE or Inspector in a formal checkride, but without any minimum number of hours in the gyroplane class (I did that long ago with less than 9 hours of total gyroplane experience). To add the full gyroplane instructor rating to a CFI helicopter rating, one must hold a commercial rating in the the class and also have 15 hours as PIC in that class per 61.183(j), and then pass the practical test. Thus, the total hours for adding both the commercial and full CFI-gyro ratings can be very low for a competent helicopter CFI. I had only 98 hours in gyroplanes when I passed my CFI-gyro checkride about 30 years ago.
I stand corrected. Thank you
 

Greg Vos

Active Member
Joined
May 26, 2019
Messages
351
Location
Cape Town
Aircraft
R44/22 H269/300 MD 500 Magni (all); Xenon RST; DTA; ELA; MTO
Total Flight Time
2480 odd (1300 gyro hours & counting)
We have seen a number of rather avoidable accidents in SA with commercial pilots who have low hours on a gyroplane as we know a gyro is not a helicopter. A gyro is not a airplane either, in SA it’s a separate licence, a person holding a diffrent licence can get and qualify for a gyro pilot recreational licence with 20 hours of gyro flight, ( provided his other licence is valid) I doubt a com Pilot heli or FW with only 100 hours of stick ( ass in the gyro) is really equipped to pass gyroplane skills over to a student.

if you like you can google gyro accident SA and be assured in the very recent past the men that died were all comm or ATP with low hours on gyro.... so now you have low hours gyro Instructor giving instruction....😳

in SA a gyro pilot may apply to become a gyroplane instructor when he has accumulated 200 hours as PIC of gyroplane ( and do instructors course and check ride with a CFI) this will place him in the lower end of the instructor food chain until he has accumulated 500 hours of gyroplane actual in cockpit stick time. This is irrespective if he was or is a IF rated fighter pilot or even a p1 on heavy metal
 

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
Messages
4,978
Location
Colorado front range
Aircraft
Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
Total Flight Time
stopped caring at 1000
I doubt a com Pilot heli or FW with only 100 hours of stick ( ass in the gyro) is really equipped to pass gyroplane skills over to a student.
Fixed wing commercial privileges don't qualify you for a quick, no minimum hours, add-on commercial gyroplane rating. The rule is only for adding a class in a previously authorized category, and those are different categories. Rotorcraft category has two classes, helicopter and gyroplane. Airplane is a separate category, with classes for single- and multi-engine, land and sea (four combinations). If you want to add seaplane privileges to an airplane land rating, for example, that requires only training to proficiency with no minimum seaplane hours before the checkride, but if you have no rotorcraft category rating, you need to do all the gyroplane hours set out in the regs for everybody else before taking the gyro checkride. (By the way, this works in both directions; if you have commercial gyroplane privileges, helicopter privileges are an add-on class with no minimum hours.)

The required instructor recommendations and the DPE checkride are good filters blocking those who would advance too quickly, but the candidates under discussion are already instructors in other aircraft types. The practice has often been for initial full-CFI applicants to get a tough test from an FAA Inspector rather than a DPE (with many failures on first exam). I recall taking my CFI-Instrument Helicopter checkride with an FAA Inspector (no DPE available), and he intentionally made it as brutally difficult as humanly possible.

I did not feel I was dangerous to my students when I got my CFI-gyro rating at just under 100 gyro hours. I could fly a gyro to commercial standards (or better), I had instructional-level knowledge of gyro aerodynamics and operations, and I already had significant experience teaching and evaluating student performance as an instructor in other categories and classes.

P.S. All these comments are based on the full commercial/CFI requirements, not the Sport Pilot instructor rules. I do not have the same level of confidence in the effectiveness or safeguards in that less rigorous regime.
 
Last edited:

Tyger

Active Member
Joined
Nov 25, 2017
Messages
613
Location
Germantown, NY
Aircraft
Magni M16
Total Flight Time
350
By the way, this works in both directions; if you have commercial gyroplane privileges, helicopter privileges are an add-on class with no minimum hours.

As has been pointed out elsewhere on the forum, if you are looking to get a helicopter rating, it's a LOT cheaper to get most of your required rotorcraft hours in a gyroplane first...
 

Greg Vos

Active Member
Joined
May 26, 2019
Messages
351
Location
Cape Town
Aircraft
R44/22 H269/300 MD 500 Magni (all); Xenon RST; DTA; ELA; MTO
Total Flight Time
2480 odd (1300 gyro hours & counting)
As has been pointed out elsewhere on the forum, if you are looking to get a helicopter rating, it's a LOT cheaper to get most of your required rotorcraft hours in a gyroplane first...
This is just insane! How can gyroplane hours ever be seen as anything to do with a heli?certainly a heli is way more of a handful than any gyro, not sure how many of you guys on this forum are heli pilots, for those who are not let me add taking power with gyro as an example is simple .... a bit of yaw and a wee bit of pitch
...with a heli pulling power (raising the collective) brings a host or required actions and even just lowering the collective one needs to be twinkle toes on the rudder, not to mention if we bring in the matter of throttle in say the H269/300 that does not have a governor 😳
I love everything about America but this is crazy
 

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
Messages
4,978
Location
Colorado front range
Aircraft
Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
Total Flight Time
stopped caring at 1000
Nobody passes their heli checkride without being able to pull pitch safely, whether or not some of the logged hours were in gyroplanes. It may sound crazy to you, but the accident stats don't reveal any special danger from these regs.
 

Greg Vos

Active Member
Joined
May 26, 2019
Messages
351
Location
Cape Town
Aircraft
R44/22 H269/300 MD 500 Magni (all); Xenon RST; DTA; ELA; MTO
Total Flight Time
2480 odd (1300 gyro hours & counting)
Nobody passes their heli checkride without being able to pull pitch safely, whether or not some of the logged hours were in gyroplanes. It may sound crazy to you, but the accident stats don't reveal any special danger from these regs.
Wasp with respect passing a check ride or even a full flight test does not accelerate your experience this comes with stick time ...one cannot sugar coat this fact ? I’m from a diffrent school of thought and question what is is that statistics don’t tell us ?
 

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
Messages
4,978
Location
Colorado front range
Aircraft
Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
Total Flight Time
stopped caring at 1000
In my view, the hour requirements are the least meaningful of all the hurdles to pass for licensing. Some people can build up 100 hours of real, varied, and judgment-improving experience while others essentially repeat the same one hour one hundred times, without meaningful progress. Some learn very quickly and some very slowly. The performance standards are the real proof of competence.

I was in San Francisco in 2013 when a a crew from Asiana, with 22,000 hours between them, couldn't hand fly a visual approach on a beautiful clear day to an 11,000 by 200 foot runway, destroying a B777, injuring many, and killing a few. Hours do not impress me.
 
Top