Best margin above a take-off obstacle

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,876
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
you are true but if you accelerate at 2 meter from the ground even if you don't benefit from the ground effect , in case of an engine failure you wont be in the dead zone.
If I climb at Vy I won't be in the shaded (avoid) portion of the height/velocity diagram jm-urbani.
 

ventana7

Gold Member
Joined
Dec 17, 2003
Messages
1,417
Location
Salida, Colorado
Aircraft
Xenon Gyroplane, Cessna 182
Total Flight Time
960
Here are a few flying and life lessons I've learned:
On rare occasions someone invents a better mousetrap -BUT NOT VERY OFTEN.
The gyroplane database of knowledge and flight testing is about .000000000000000000000...0001 percent of the amount of knowledge and flight testing that has gone into fixed wing aviation.

So every time I read on the gyro forum that someone has discovered a better way to fly than what is taught in FW aviation I'm pretty skeptical.
This was true when the guys at El Mirage tried to explain to us how the physics of flight are different out there.
It was true when gyro pilots tried to explain that there was a difference between how your gyro handled flying up wind vs downwind.
And I believe it's true now-

As Vance and all the other CFIs have explained:
The best airspeed to use for obstacle clearance is Vx
The best airspeed to use for climbing to altitude not caring about an obstacle is Vy
The safest takeoff procedure is to accelerate in ground effect until you reach one of the above speeds.
If your gyro's ability to clear an obstacle is at all in question you should either do it when atmospheric conditions are more favorable (cool morning, lighter load or headwind) or you should be flying somewhere else.

If it was possible and safer to start your climb at below Vx speed and have better obstacle clearance results then fixed wing aviation would have been teaching that way all along.
If it was possible and safer to have better obstacle clearance by accelerating beyond Vy then yanking your aircraft up to jump - then FW aviation would have been teaching that all along.

There is a difference between indicated airspeed and calibrated airspeed and gyros without a static port and in a climb are pretty sure to have some instrument error so if your Vx and Vy are only a few knots apart much of this discussion is meaningless- AS LONG AS YOU ARE FASTER THAN INDICATED. If you are testing a climb at slower than Vx and your instrument is off and you are actually slower than indicated then you are conducting flight testing in a regime where there is no margin for error- you could and likely will end up like the video above.

In my Xenon gyro the difference between Vx and Vy is only 3 knots- And Vy and best glide speed (Vg) are the same. (And all three speeds could be compounded by my instruments error).

(In most of the other gyro manuals I looked at Vx, Vy and Vg (best glide) were within 5 knots. In most manuals the best glide or approach speed was within a knot or two of Vy.

For myself in a NORMAL takeoff I climb out 4-5 knots faster than my instruments indicated Vy because that gives me a margin for instrument error that protects me in three ways.
If I am actually flying slower than Vy I am still above Vx so my gyro will continue to climb.
If I am actually flying slower than indicated I am still at or very close to best glide and being at or above best glide keeps me out of the HV envelope.
If when looking outside for traffic and obstacles I stray from my instruments and intended speed I have a buffer.

IMHO having my eyes glued either to an obstacle or to the instruments does not improve safety.
 
Last edited:

chrisk

Gyroplane CFI
Joined
Jun 5, 2015
Messages
278
Location
Round Rock TX
Aircraft
Magni M24, Turbo Mooney 231
Total Flight Time
1000
Because I am covering less ground with a head wind I have a steeper angle of climb at the same Vx indicated air speed.

To me the most important takeaway from this discussion is slower or faster than Vx is not the way to clear an obstruction.

I don’t fly out of short fields with obstructions at the departure end to avoid pretending I know how high I will be when I reach the obstruction.
We are fundamentally in agreement!
 

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
1,963
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)
To me the most important takeaway from this discussion is slower or faster than Vx is not the way to clear an obstruction.
My title explains how to increase the margin above the obstacle by a better choice of forward speed. It doesn't remove the obstacle, but it removes stress

The headwind further decreases the speed / air to be chosen.

If you are taking off from JFK airport, then this subject does not interest you. You only have to manage the possible engine failure or its temperature (Vy is better)

As Vance and all the other CFIs have explained:
The best airspeed to use for obstacle clearance is Vx
Yes, this has already been said many times. This is only true when the obstacle is a mountain, when we can neglect the distance lost in level to reach Vx or Vy.
 
Last edited:

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
If it was possible and safer to have better obstacle clearance by accelerating beyond Vy then yanking your aircraft up to jump - then FW aviation would have been teaching that all along.
Ventana and all,

first of all, I am here to learn not to tell that with my ridiculous 250 flight hours on my monoseater I know everything about flying, I certainly know less then you all , and this is the reason Why I am here .

but I've practised deep mixed gas re-breather diving for a 15 years (and before years 23 of Air scuba diving) and I've flown gyroplanes for 8 years, it does not give me any legacy to speak , I Am just mentioning this to say that my first concern has always been to protect my Ass in those activities in which a couple of my friends died (both in Diving and Gyro ).

without any consideration for obstacle clearance, my gyro having seemingly a Vx of 80 km/h ( It's an home built) I always accelerate up to 100 km on ground effect ( sometimes a bit more) and then I pull the stick and ascend @ 80 km/h

please watch this in the video and tell me where is my dangerous crazy jump in this take off ? ( take into account that this day there was at least 35 km/h of head wind at ground level and 50 km/h in the patern , and tell me where I am at risk during this take off please

thanks

 
Last edited:

Jean Claude

Junior Member
Joined
Jan 2, 2009
Messages
1,963
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)
Who said this takeoff was a crasy jump?
Did I say somewhere that climbing at Vy is a crasy jump ?
Read again my post # 64
 
Last edited:

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
please JC don't always think that I am attacking you, this is absolutely not the case, I always read what you write with interest and even If we had an argument in the past , I don't mind

you never said that this take off was a craz jump and you never said that climbing at Vy was a crazy jump

I think that you talked about crazy jump after reading my exchanges with Fara on an other thread, if it is the case , never mind I don't care at all , I largely prefer to show that I am wrong then to crash someday in the ignorance of things you could teach me even If I know that you always take great pleasure to point out my ignorance ( which I don't care because, I am actually ignoring many things in aviation even if I strictly do what I was taught)

if it is not the case, it is the same because the way I take off does not fit what you have been explaining here on the point that I don't pull the stick at 80 km/h ( that I think is my Vx but that it could be my Vy) but at 100 km/h and sometimes a bit more (105), but after I climb at 80km/h

Ventana says ( ok about obstacle clearance) :

"accelerating beyond Vy then yanking your aircraft up to jump "

en Français cela veut dire : "accèlèrer au delà de Vy en donc arracher ton aeronef pour sauter"

this means sorta, kinda "Crazy jump" no ?

So as I am always taking off this way, and without any willing to fight with you or anyone I am showing the video of me ( the only one that I have ever shot) ;

I just wanted to know if I was in danger doing this hence I asked here because here there are highly experienced pilots and instructors ( much more experienced then you and me)

Even if ventana says that FW well known principles are applicable to gyroplane, I personally think that exceeding of 15% Vx on ground effetc before pulling the stick gives me a little bit more margins in my take off even If I don't climb at more then 80 km/h ( my Vx or Vy), for me it is a jump ( and not a crazy one) but now I am in doubt

so please let them watch this video that they won't watch if it get dug under 15 of or messages
 
Last edited:

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,876
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
If you were my student jm-urbani and I was in the back seat (I understand there isn’t one) I would be saying good rotor management, good smooth control inputs, nice smooth progressive throttle, nice balancing and good lift off and climb out.

Because I could not see the indicated air speed I don’t know exactly what you did on airspeed.

On landing I would be saying nice alignment, good rate of descent, nice smooth control inputs, nice touch down at minimum forward speed, and good after touch down cyclic management. It is good you didn’t waste time on the runway.

I would sign you off for solo or your check ride depending on what other things we had done.

If I was doing your proficiency check ride, assuming your airspeeds were within standards and the rest of the maneuvers were within standards I would sign the form and you would be getting an FAA Sport Pilot, Gyroplane certificate in the mail in a few weeks.

Your demonstrated skills would have me signing your log book for a flight review too. The FAA requires a flight review consisting of at least an hour of ground and an hour of flight within the last 24 months to be current to fly without an instructor.

In other words I would rate you a proficient pilot no mater your level of experience.

Because of conditions and the demonstrated aircraft performance the FAA would consider this a soft field takeoff and a soft field landing.

Because of conditions and aircraft performance it would not be considered a short field takeoff.

I teach in a normal takeoff to accelerate to Vy in ground effect and climb out at Vy. The FAA practical test standard is plus or minus five knots (9kph) on both approach and climb out.

For a short field takeoff I teach to accelerate to Vx in ground effect and climb out at Vx.

In most gyroplanes I have flown there is less than five knots between Vx (best angel of climb) and Vy (best rate of climb).
 

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
thanx for having watched this boring pattern, and thanx for the comments, if I am on the safe side it is reassuring , I can gon on jumping this way ( I am kidding)

as for airspeed, this mono seater is really touchy ... it needs great accuracy, she is light and any input excess is paid in airspeed loss
 
Last edited:

ventana7

Gold Member
Joined
Dec 17, 2003
Messages
1,417
Location
Salida, Colorado
Aircraft
Xenon Gyroplane, Cessna 182
Total Flight Time
960
you never said that this take off was a craz jump and you never said that climbing at Vy was a crazy jump

I think that you talked about crazy jump after reading my exchanges with Fara on an other thread, if it is the case , never mind I don't care at all , I largely prefer to show that I am wrong then to crash someday in the ignorance of things you could teach me even If I know that you always take great pleasure to point out my ignorance ( which I don't care because, I am actually ignoring many things in aviation even if I strictly do what I was taught)

if it is not the case, it is the same because the way I take off does not fit what you have been explaining here on the point that I don't pull the stick at 80 km/h ( that I think is my Vx but that it could be my Vy) but at 100 km/h and sometimes a bit more (105), but after I climb at 80km/h

Ventana says ( ok about obstacle clearance) :

"accelerating beyond Vy then yanking your aircraft up to jump "

en Français cela veut dire : "accèlèrer au delà de Vy en donc arracher ton aeronef pour sauter"

this means sorta, kinda "Crazy jump" no ?

So as I am always taking off this way, and without any willing to fight with you or anyone I am showing the video of me ( the only one that I have ever shot) ;

I just wanted to know if I was in danger doing this hence I asked here because here there are highly experienced pilots and instructors ( much more experienced then you and me)

Even if ventana says that FW well known principles are applicable to gyroplane, I personally think that exceeding of 15% Vx on ground effetc before pulling the stick gives me a little bit more margins in my take off even If I don't climb at more then 80 km/h ( my Vx or Vy), for me it is a jump ( and not a crazy one) but now I am in doubt

so please let them watch this video that they won't watch if it get dug under 15 of or messages
Jm Urbani,

Vance gave you a very nice analysis of your flying. Congratulations.
I would suggest you get clear on your aircraft's Vx, Vy and Vg speeds.

The term crazy jump may be a language issue but we will put that aside for a minute and I will try to comment on your take-off description.
First off you have to promise not to laugh at my drawing.

I don't see anything wrong or dangerous in accelerating well beyond Vy before climbing out at Vy and as I said I exceed Vy by a few knots to account for possible instrument or pitot tube alignment errors.
I do see two advantages to not accelerating far beyond Vy near the ground.
First off as Vance previously mentioned if there is a cross wind you are likely spending more time close to the runway in a cross controlled situation which is inefficient. If you switch to a crab but are still close to the runway an engine failure would not give you much time to switch back to a cross control for landing.
The second advantage to climbing as soon as your reach Vy can be seen in the drawing below.
The solid line is a climb out at Vy and the dashed one shows accelerating longer before climbing out. If you had an engine failure in the first example of accelerating only to Vy you are at point B and have altitude which gives you the option to turn back to the runway which you know is behind you or to land ahead of you into the wind. Both options are open.
If you accelerate much longer and have an engine failure (Point A) your landing is going to be straight ahead- that may be fine especially at the airport in your video but at some places and especially at airports with obstacles which started this thread that may not be so great- there may be rough terrain.

Like you I have been a life long adventurer- a scuba diver for over 40 years, I've climbed big mountains in Alaska and the Himalaya and sailed my own boat around the world, plus flown my gyro to all 48 states in the Continental US. I do "dangerous" things but while doing them I do EVERYTHING possible to stack the deck in my favor. If a Vy take-off gives me two options and a faster than Vy takeoff gives me only one option I know which I'll choose.

Rob

Vy takeoff 2.jpg
 
Last edited:

XXavier

Member
Joined
Nov 13, 2006
Messages
1,013
Location
Madrid, Spain
Aircraft
FW Savannah XL + ELA R-100 and Magni M24 autogyros
Total Flight Time
1396 FW + 537 gyro (Dec. 2019)
The technical discussion in this thread is quite enlightening, at least for me, but I very much doubt that any pilot really keeps his eyes fixed on the anemometer during the take-off, and that not only for safety reasons, but because it isn't probably frequent that the pilot knows with certainty the Vx and Vy of his gyro...
 

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
Rob, Vance , JC, and all,

I really have to thank you very much for the time you spent explaining things to the community, Now I have perfectly understood the whole strategy.
I had been taught to do this famous ground effect acceleration and during dual training take off the instructors are showing us the acceleration , and now that I am thinking f it I realize that this famous jump was the impression I had doing this for the fist time in my life back when everything was new

I telephone to my instructor telling him about this and he told me that it was ok to reach to this famous Vy with a little positive margin but that it would bring me nothing in terms of safety to exceed Vy by 20% ..he also added that with my monoseater is was ok to get to 100km/h cos it is light but that with a 500 kg gyro it would be expensive in terms of take off distance

rob your drawing is perfect.. and dissipated my last doubts .

I was also taught that in order to pass over and obstacle one had to aim at the foot of the obstable ( for example a tree) , and keep enough airspeed instead of pulling too much the stick which lead behind the power curve

but of course this was a "image" , to teach trainees that the most important was to keep the right airspeed, there also I had interpreted it litterrally ... I am a bit stupid in fact , or extremist ( thinking that it would take me on the safe side) ...

the point is that I really thought the best way of clearing and obstacle was to rush on it and pull the stick at the "last moment" , I have never attempted to pull really at the last moment but I could have ..

JC reexplained this too me also;

what I can say is that this week end I will take off taking in account all that was said

so OK guy's all of this will certainly has saved me from my ignorance ..

thanks a lot
 
Last edited:

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,876
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
The technical discussion in this thread is quite enlightening, at least for me, but I very much doubt that any pilot really keeps his eyes fixed on the anemometer during the take-off, and that not only for safety reasons, but because it isn't probably frequent that the pilot knows with certainty the Vx and Vy of his gyro...
I use my sight picture to maintain Vy on climb out and calibrate my sight picture with an occasional glance at the airspeed indicator as a part of my panel sweep.

Two of the questions on my pre-solo test are; what is Vx and Vy for the gyroplane they will be flying?

The FAA practical test standard for climb out is plus or minus five knots.

In my experience if someone is focused on the airspeed indicator they will not be able to meet the standard.

In my experience the airspeed indicator is always well behind the sight picture.
 

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
Hello Vance,

thanks for your contribution

practical question :

. as for descent approach I tune my descent air speed looking at the speed indicator and then I look forward up to a focal point on the runaway, aiming at this point keeps my airspeed stable and I only look at the air speed indicator a couple of times to check

. on ascent it is a bit different because most of the time there is no focal point I can focus on when I climb ( except is there is a mountain ahead)

so when you climb what do you look at ?, again it is crazy because you always point out really practical things .. and as a matter of fact during initial ascent I focus too much on the airspeed indicator and I go to a tough time maintaining a stable airspeed ..
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,876
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
I calibrate my sight picture with a glance at the airspeed indicator during all phases of flight.

In all the gyroplanes I have flown pitch (the sight picture) is very closely related to airspeed in coordinated flight.

In my opinion the air speed indicator is too far behind to use it to fly the aircraft.

Writing in the most general terms the horizon doesn’t change and if you line something up with the horizon the airspeed will remain relatively constant.

Where I fly around mountains I sometimes need to imagine where the horizon is and I may pick a point at the base of the mountain. As I draw close this becomes less accurate.

When I am trying to share this methodology with someone I head out to the ocean where winds tend to be steadier and the horizon is clearly defined.

I find maintaining airspeed by sight picture more difficult with a completely open machine.

Sometimes it helps me to have something specifically to use as a sight with like a line across the windshield or a yaw string that is close to the correct height.

For example if your sight is two inches below the horizon that airspeed will be maintained as long as the two inches are maintained.

I find altitude more difficult to judge from the sight picture and I rely more on the altimeter and vertical speed indicator to maintain altitude although it too is behind the aircraft.
 

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
ok Vance awesome,
in fact I understand now what you mean by sight picture ..
so you take off and then you tune your airspeed and have a look outside, it gives you a " picture " that you have to keep "immobile" ( it must not go up or down) ...
to be honest I had read this in the ultralight pilots book but there are so many things we learn by heart for the exam and that we don't see the practical importance of ...
my instructor had insisted a lot on this for approach and level flight but I don't remember he insisted on it for take off .
the point is that the magni is really stable in airspeed and we were heavy ( two 90 kg guys in the gyro) so he never had to give me a way of stabilizing my ascent airspeed coz I never gone to a though time with this in the M16
in the monoseater it is an other pair of handles ..
I will apply this in my small dragonfly ... good good ... I am not loosing my time here, it is great that I triggered JC attention after my bullshit statement about my bullshit obstacle clearance method ....
fine
thanx again Vance
 
Last edited:

ventana7

Gold Member
Joined
Dec 17, 2003
Messages
1,417
Location
Salida, Colorado
Aircraft
Xenon Gyroplane, Cessna 182
Total Flight Time
960
Vance,
As you know I live and fly in the Rockies. The dot or scratch or mark on the windshield is extremely useful.
You can put a tiny dot on the windshield where your view intersects the horizon over the flats then use that for straight and level in the mountains. Also as you approach the mountain you can gauge clearance, along with noting if you are seeing more or less terrain beyond the mtn. (More means you will clear the mtn, but your dot can help you gauge how much).

A dot is super helpful in teaching steep turns even in the flats. Keep the dot on the horizon throughout your turn and you will keep your altitude the same, much more accurate than reacting to the lag in your VSI or Altimiter.
Rob
 

Kevin_Richey

Yamaha gyro...Oregon, USA
Joined
Nov 16, 2003
Messages
2,152
Location
Oregon, USA
Aircraft
Sport Copter gyroplane
Total Flight Time
300+ gyroplane, 11 airplane, 1.5 PPC, AND... a ZILLION hours of flying in my dreams!
Vance: You most likely can judge accurately your A/S by the wind noise & feel & sight picture w/out even looking @ your ASI.

Jim Vanek told me that he can tell w/out looking @ the ASI while I was taking dual training in the SC tandem trainer, & the back seat didn't have an ASI for him to see, only the front seat for the student.

I'm not @ that level like you instructors are. When guessing my A/S, I'm usually off by at least 5-10 mph when I then look @ the ASI.
 
Last edited:

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,876
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
Vance: You most likely can judge accurately your A/S by the wind noise & feel & sight picture w/out even looking @ your ASI.

Jim Vanek told me that he can tell w/out looking @ the ASI while I was taking dual training in the SC tandem trainer, & the back seat didn't have an ASI for him to see, only the front seat for the student.

I'm not @ that level like you instructors are. When guessing my A/S, I'm usually off by at least 5-10 mph when I then look @ the ASI.
I still calibrate my sight picture with my airspeed indicator Kevin.

When I am in the back seat I can tell plus or minus five knots by how the wind feels.

I would still be lost without my airspeed indicator in the back seat.
 
Top