A common language shared by divergent cultures can inhibit communication.

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
Philbennett;n1142104 said:
and how is any of that relevant to the graph which has a curve labelled "engine power available at full throttle" verse airspeed? If one puts full throttle at zero airspeed is engine power not available?

In my opinion the engine graph showing horsepower at rpm is not relevant to describing flying behind the power curve.

My Lycoming IO-320 will make 140 horsepower at 2,300 rpm if I lift off at 20kts and because I am flying behind the power curve my climb out will be less than 200 feet per minute. If I lift off at 45kts I will still be making a little over 140 horsepower and yet I will be climbing in the range of 1,100 feet per minute.

I refer to that as flying behind the power curve not because I am lazy but because that is the correct term according to the FAA and the physics.

The people I am trying to communicate with share the definition of behind the power curve.

Flying behind the power curve is unrelated to the engine's power curve.

You graph appears to me to be horsepower at rpm rather than horsepower at airspeed.
 

Mac

Member
Joined
Jan 30, 2005
Messages
247
Location
Amarillo, TX.
Aircraft
Dropkeel KB2, EA81, 2.19:1, 68"Warpdrive, 24'Dragonwings, talltail
https://youtu.be/kW65IY39MPU

Performance takeoff - good video!

After watching Phil's video, I wrote down what I considered was ten sequences he used in the video

1. Move stick into the wind (apply brake - my input)
2. Advance throttle to 2000 rpm (912 914)
3. Engage prerotator to begin rotating rotor blades to 200 rrpm
4. Move stick to center/full forward
5. Release prerotator once 200 rrpm is achieved
6. Move stick to center/full back (release brake)
7. Add slight throttle to initiate ground roll (nurse rrpm)
8. With ground roll initiated, watch for a positive increase above 200 rrpm
9. With positive increase in rrpm, unload the stick about 1/5 forward and gradually advance throttle to full within 3 to 4 seconds
10. Climb out @ 70 mph
 

C. Beaty

Gold Supporter
Joined
Apr 16, 2004
Messages
10,031
Location
Florida
Many years ago, a charming young lady said to me; “Knock me up the next time you’re in London.”

In US slang that would mean; “Get me pregnant the next time you’re in London.”

However the simple expression from elementary physics; “Power equals thrust x velocity,” cannot be misinterpreted whatever the language. It is the same whether expressed in English, Chinese or whatever.
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
JM - see the post No.48. Mac gets it - his point 6. The stick is fully back. I can't see what element of the technique is the cause of accidents because the story you relate do not match what I'm suggesting. But hey ho. As you say it doesn't matter. You won't have the issue. All is cool.

C Beaty - can you explain the curve labelled Engine power available at full throttle please.

Vance can you explain that same curve? Or even what your definition of a power curve is.

Thanks.
 

C. Beaty

Gold Supporter
Joined
Apr 16, 2004
Messages
10,031
Location
Florida
In the plot from the Bensen manual of power required vs airspeed, power could be calculated by measuring towline pull vs airspeed. Has nothing to do with engine power.

No matter how much thrust is applied to a stationary object, no power is delivered since power equals thrust x velocity and with a velocity of zero, power available also equals zero, regardless the source of thrust, whether from a propeller churning air or a large rubber band.

The plot of power available in the Bensen chart is calculated from propeller thrust vs velocity which also shows power available to be zero at zero velocity.
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
No Title

Thank you Mr Beaty and therefore you can clearly see where the confusion comes from because the graph you posted in post No.36 clearly shows the curve we are debating is labelled:-

Engine power available at full throttle


Whilst now you have given clarity such that

C. Beaty;n1142152 said:
In the plot from the Bensen manual of power required vs airspeed, power could be calculated by measuring towline pull vs airspeed. Has nothing to do with engine power.

Funny old thing isn't it language?

However wait there is more. You know the modern world is a marvellous thing and can you believe the PRA have scanned old copies of their magazine - great resource. From the archive then are a few more curves. The first another Bensen produced curve this time showing would you believe prop thrust verse forward speed. It doesn't start at zero.

Then a curve that looks awfully familiar - except this time it is simply labelled available with some context in the text, which includes prop thrust.... I guess over time people must have added their own interpretation. Interesting how in 1967 upwind and downwind is seen as unconnected to airspeed, how times change.
 

Attachments

  • photo131572.jpg
    photo131572.jpg
    31.5 KB · Views: 2
  • photo131573.jpg
    photo131573.jpg
    44 KB · Views: 2

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
Philbennett;n1142145 said:
JM

Vance can you explain that same curve? Or even what your definition of a power curve is.

Thanks.

On either side of the minimum power required speed progressively more power is required to maintain level flight.

It is expressed as a curve and that is why being below the minimum power required speed is often called being "behind the power curve".

Don't they teach about the power required curve in the UK Phil?
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
Philbennett;n1142156 said:
Thank you Mr Beaty and therefore you can clearly see where the confusion comes from because the graph you posted in post No.36 clearly shows the curve we are debating is labelled:-

Funny old thing isn't it language?
Interesting how in 1967 upwind and downwind is seen as unconnected to airspeed, how times change.


I am sorry you are confused Phil.

In the USA upwind and downwind are ground reference terms and were in 1967.

The power required curve is about airspeed.

Is this different in the UK Phil?
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
No Title

The confusion came because of the way the graphs have changed over the years and new interpretations taken that are inaccurate and then compounded by people trying to explain something that is fundamentally wrong and having found the original source document the changes that have been made over the years are clear.

Beaty's graph changed the meaning of one curve and indeed at the time that graph was created being behind the power curve was not a phrase being used. It was being on the low or high side of the power curve. See photo 1 here. Indeed that is how Mr Bensen himself termed it and power was not "engine" power but the combination of power delivered by engine and prop thrust at the airspeed to be non-accelerative.

Being behind a curve on a graph is to be on the left of the curve. Power required curve is nothing more than the total drag curve. So you might be on the back of the drag curve which could also be traded for the power REQUIRED curve. Simply saying power curve is ambiguous and in the UK we do not like ambiguity with students as it leads to errors.

So yes we understand the power required curve, yes it is taught as the power required curve, also known as the drag curve - which is more efficient containing less words and students can't find old inaccurate charts. Its just taken until I pushed for everyone to use the correct terms.

If we related to the Beaty chart and the curve labelled engine power available at full throttle then would be impossible at any speed to be at a point to the left of that curve and indeed until flight is no longer possible at no point is the power available curve behind the power required curve. So using this graph and the term "behind" wouldn't seem to reflect things accurately.

On the downwind point you need to read the 1967 magazine to understand the reference.
 

Attachments

  • photo131573.jpg
    photo131573.jpg
    44 KB · Views: 2
  • photo131574.jpg
    photo131574.jpg
    26.5 KB · Views: 2

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
Philbennett;n1142163 said:
The confusion came because of the way the graphs have changed over the years and new interpretations taken that are inaccurate and then compounded by people trying to explain something that is fundamentally wrong and having found the original source document the changes that have been made over the years are clear.

Beaty's graph changed the meaning of one curve and indeed at the time that graph was created being behind the power curve was not a phrase being used. It was being on the low or high side of the power curve. See photo 1 here. Indeed that is how Mr Bensen himself termed it and power was not "engine" power but the combination of power delivered by engine and prop thrust at the airspeed to be non-accelerative.

Being behind a curve on a graph is to be on the left of the curve. Power required curve is nothing more than the total drag curve. So you might be on the back of the drag curve which could also be traded for the power REQUIRED curve. Simply saying power curve is ambiguous and in the UK we do not like ambiguity with students as it leads to errors.

So yes we understand the power required curve, yes it is taught as the power required curve, also known as the drag curve - which is more efficient containing less words and students can't find old inaccurate charts. Its just taken until I pushed for everyone to use the correct terms.

If we related to the Beaty chart and the curve labelled engine power available at full throttle then would be impossible at any speed to be at a point to the left of that curve and indeed until flight is no longer possible at no point is the power available curve behind the power required curve. So using this graph and the term "behind" wouldn't seem to reflect things accurately.

On the downwind point you need to read the 1967 magazine to understand the reference.

In my opinion you are reading things into the charts that aren’t there Phil.

Left is behind for specific charts for specific purposes.

Part of being a good flight instructor is to see what people misunderstand before it gets them into trouble. Sometimes they don’t listen and their misunderstanding gets them into trouble despite the attempted intervention.

With open framed gyroplanes pilots would often substitute ground speed for air speed leading to getting behind the power curve on down wind.

Not everyone who writes about gyroplanes is qualified to do so accurately.

Not all people who make training videos shown on YouTube offer sound instruction.

Everyone makes mistakes.
 

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
Messages
4,910
Location
Colorado front range
Aircraft
Bell 47G-3B-1 / A&S 18A / Phoebus C, etc.
Total Flight Time
stopped caring at 1000
Two observations to begin. First, i am troubled by the idea of "the" drag curve. What seems to be under discussion here is the sum of two curves, an induced drag curve, and a parasitic drag curve, one increasing and one decreasing, with their sum, a total drag curve, being a third drag curve. I am loathe to describe "the" drag curve without also explicitly clarifying that I mean the total. This is important for students to understand why it has the shape that it does, arising from the summing of two others. Second, my understanding of the "back side" of a curve is not identically the same as the left side of a curve, depending at least upon whether that curve is concave up (a valley) or concave down (a hill).

This leads me to ask,
would we all be on the same page if one spoke of the region of reverse(d) command instead of the back side of a curve? Otherwise, it seems to me that we are attempting to put precision into a term that is essence a short-hand at its root, and that is not likely to lead to clarity.

As a separate observation, I offer a thought and a request. (1) Bensen's charts were never the be-all and end-all for aviators at large and the scaling/curve shapes differ somewhat in other sources. I dealt with power required ideas long before I ever encountered anything prepared by Igor Bensen (and spent a great deal of time coping with polar curves for sailplanes as well). (2) If not too big a bother, might somebody be able to dig out copies of the old William Kershner manuals (Student, Advanced, and Flight Instructor) and see how the figures are shaped and labelled there? My whole aviation library is in inaccessible storage while I move to a new house so I can't check them myself, but I would like see how they are drawn, if it's not too inconvenient for somebody who has those resources at hand.
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
Yep Wasp i agree it certainly is good for the sake of understanding to be very clear about what one is trying to describe. Would be interedting to see how the same problem is depicted elsewhere.

Vance i didnt introduce any graph i merely asked for a clarification of how that fitted with the point made. I guess you can instruct two types of people those with prior aviation experience - in which case trying to push magical thinking ideas isnt helpful or you can teach those with no prior aviation experience and in which case they dont know fact from magical thinking. In that case it becomes quite important to be accurate.

have you got a reference for the ground speed / air speed point? Just that i find it incredible! Cheers
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
It was common during the self-taught Bensen era to imagine there was great danger in the downwind turn. They would lift off at low indicated airspeed and turn downwind seeing the ground speed go from perhaps 30kts to 50kts; pulling back on the cyclic to reduce speed climbing the power required curve and hit the ground.

The downwind turn is still a subject of controversy; only less so with the body of the gyroplane blocking some of the sensation of the increase in speed from ground reference.

I do not have any specific references to the downwind turn challenge.

Because our practical test standards are plus or minus ten knots or plus or minus five knots on approach to land my clients have a tendency to get focused inside the aircraft.

It is a part of why I teach people to fly based on the sight picture without reference to the airspeed indicator and why I feel it is important to look out toward the horizon rather than down at the ground or in the cockpit.

In my opinion the concept of the power required for level flight increasing as the speed is reduced below the minimum power required is not magical thinking at all. It is complex and counterintuitive for most of my clients; particularly primary students.

In my opinion J. R. explained in nicely.

There is a lot going on that creates the power required vs. power available curve.

There are fixed wing flight instructors in the USA that call the power required curve the drag curve. It is my understanding that it is not generally accepted by the FAA.

I do not recall a gyroplane flight instructor in the USA who refers to the power required curve as the drag curve. I have flown with thirty three CFIs but it does not always come up.
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
If nothing else it has been good to have the discussion and of course you know what you mean, of course C Beaty will know what he means and perhaps you might be generous to think I know what I mean.

We have spun our wheels for 30-ish posts because I was being patronised with lessons about apes and power when actually the labels on the graph were inaccurate.

Of course what is actually happening is not magical thinking but that phrase fits when or if you start putting a graph on a white board and mis-describe what is happening. In the end your students are coming for a flying lesson. They are not on an aerodynamics course, neither are they on a physics course but they do deserve the respect to have things explained properly and consistently. I might offer up the suggestion that in a small community - such as gyroplane instruction - you are likely to simply mimic the views of the guy who taught or examined you and things get questioned less either out of respect or commonly people like to "get along in order to get along". How many times might that graph for example have been rolled out and nobody says "hang on... that doesn't seem right.."

You can see therefore that if airspeed and ground speed were to be presented as you suggest from the Bensen era that would be very confusing for pilots of today.

Now this isn't a personal attack, I'm not saying you do anything poorly at your school, this is a general chit chat. Where this started was a discussion about landing speeds and my wider point is that in a modern 2 seat gyroplane there is a general focus on "old school" single seat issues which are not issues today BUT having focused on that issue we ignore things that are problematic.

What I can not understand very well is that for people that can fly a gyroplane well or have good experience with a gyroplane they are incredibly easy aircraft to fly and yet for all the "improvements" in knowledge of flying them and technology the accident rate is still terrible. I suggest it is because of above. You may take a different view?
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
With the ground speed vs. airspeed in the Bensen; what I was describing was how accidents happened, not what was taught.

Dr. Bensen taught airspeed and took care to separate it from ground speed and make people aware of the hazards.

Pilots are people and people make mistakes whether they understand the principals involved or not.

No one that I know of teaches to land misaligned with the runway and yet it is often part of the accident sequence.

Everyone I know teaches that the flight is not over till the rotor is stopped and the aircraft is back in the hangar and yet tip overs after landing with the rotor near flight rpm continue to destroy gyroplanes.

Understanding the power required curve is so important to the FAA that they require the pilot perform recognition of and recovery from low airspeed and a high rate of descent and yet people continue to fly into the ground because they are behind the power curve and they imagine the cyclic is the up lever.

I like to imagine that working together pilots and flight instructors can improve the accident rate of gyroplanes.
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
16,568
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2400+ in rotorcraft
Thank you for your input JM. You are on point with a great example.

Most clients of mine want to get their training finished in the minimum number of hours to save money.

As you say; this limits the experience I can provide and basically I am providing them with a license to learn. I give them tools but some quickly rust.

Our proficiency check ride is supposed to catch bad habits before they cause an issue but your example is not unusual. People slowly slip into bad habits.

That is why in the USA every two years pilots are required to have a flight review with a minimum of an hour of ground and an hour of flight. I rarely give a flight review where I don't correct some misunderstanding or bad habit. It is amazing to me when people want me to just sign them off as though I had given them the instruction because they know how to fly.

Fortunately most pilots take the flight review as an opportunity to learn.

People train in a relatively narrow range of environmental conditions and the first time the conditions change bad habits may come to the surface.

You are right; if it wasn't important I wouldn't dwell on it.

It is very difficult for the flight instructor to properly prioritize each specific instruction because there are so many.

As can be seen on the Rotary Wing Forum some people with just a few hours imagine that they have discovered some new magical way to fly a gyroplane and it may get them into trouble when flying in less idyllic conditions.

They often reject input because they imagine they know it all.
 

Tyger

Active Member
Joined
Nov 25, 2017
Messages
930
Location
Germantown, NY
Aircraft
Magni M16
Total Flight Time
360
Like JM, I also recently went through my primary training, and my instructor never talked about "wheel balance" at all. If fact, the technique I was taught was pretty close to Phil's, although we did not focus on the RRPM indicator after starting the takeoff roll. My training was on a concrete strip in an open area, in both very hot and very cold weather, and in all kinds of wind conditions (somehow usually with a lot more crosswind than I would have liked). I now fly off a grass strip, with a fair amount of slope, nestled in a moderately forested area, but I don't find these differences a problem at all, except that taxiing is now a lot bumpier (and slower)!
During my instruction, we talked about the parasite- and induced-drag curves, what they looked like combined, and how they affected flight. We never specifically called it "the drag curve", nor "the power curve", as far as I can recall. As long as the axes and curves are labelled, the graph as a whole really needs no grand title, it seems to me.
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
Vance;n1142213 said:
With the ground speed vs. airspeed in the Bensen; what I was describing was how accidents happened, not what was taught.

Dr. Bensen taught airspeed and took care to separate it from ground speed and make people aware of the hazards.

Pilots are people and people make mistakes whether they understand the principals involved or not.

No one that I know of teaches to land misaligned with the runway and yet it is often part of the accident sequence.

Everyone I know teaches that the flight is not over till the rotor is stopped and the aircraft is back in the hangar and yet tip overs after landing with the rotor near flight rpm continue to destroy gyroplanes.

Understanding the power required curve is so important to the FAA that they require the pilot perform recognition of and recovery from low airspeed and a high rate of descent and yet people continue to fly into the ground because they are behind the power curve and they imagine the cyclic is the up lever.

I like to imagine that working together pilots and flight instructors can improve the accident rate of gyroplanes.

Agree with all of that Vance and I think the biggest win of forums is the communication ad opportunity to share ideas and thoughts.

I think this post is the nub of what has been in my thinking over the last year. In the UK (and from what has been spoken about here I'm sure in the US) pilot training has moved far beyond self-taught and is now a professional endeavour with professional instructors following a well trodden syllabus. Now I think the progress that has been made is where much fewer people are killing themselves but the accident rate is still high and it seems to me - when I reflect on UK accidents - there are a great number that occur in take off and landing.

Exactly as you say Vance the flight isn't over until the aircraft is in the hangar and yet (again speaking from the UK perspective) the pilot syllabus is very poor at allowing a focus upon things that are really going to make a difference verse things that if I speak frankly make chuff all difference.

We have talked about flight behind our drag/power (I think we can agree we know what each other is talking about now!!) and it is a very big issue BUT you look at your average POH and they are just so far behind what your average Cessna / Piper driver is using. I think I posted an extract from the 2017 sport version on take off performance and even today there is a huge range and very poor guidance around the issues.

Now yes we can teach as instructors but then someone comes along with a new aircraft with the sales and marketing music in the ears and how are we left? The very last gyro accident reported in the UK was an instructor in a Cavalon but with literally a handful of hours on that model. https://assets.publishing.service.g...e0d7aa/Rotorsport_UK_Cavalon_G-CKYV_01-19.pdf

On the flip side I taught a helicopter instructor who had circa 4000hours instructional hours in helicopters and yet I had to spend almost 1/3 of his course doing navigational elements and a qualifying cross country (where the student lands away etc) - It just beggars belief because just what possible value did any of that add to this highly qualified pilot? Lets be totally honest in terms of accidents we could almost completely ignore navigation to focus on general handling and give a restricted license then introduce navigation once the pilot has a few hours underneath him/her.

Like you Vance one problem is that new pilots arrive with an expectation they are going to get the whole process done in X hours. Now of course none of us send the guy either solo or to test unless he is ready but there is expectation and clearly everyone understands that the new pilot is not going to be perfect. So the "system" effectively releases the new pilot to the world without (in my opinion) allowing the focus on the items that he really needs to be drilled upon to ensure he is absolutely clear what is going to keep him/her safe.

Post landing rotor management is a big one too - but again how often do we drill that process and some of the worst offenders are experienced pilots. I think its why focus on the RRPM gauge is quite key for me. https://youtu.be/1PGHFDZd7V0?t=120
 

EdL

Comm Rotor Gyro, ASEL
Joined
Feb 11, 2018
Messages
144
Location
Lakeway, TX
Aircraft
Magni M-16, Piper Warrior
Total Flight Time
1300
This has been an interesting thread to follow and to reflect on my own procedures and training.

Again, all of my training has been in a Magni and virtually all by Dayton. I was taught to prerotate to 220, stick full back, advance the power over a few seconds, and do the wheel balance until airborne then stay well within ground effect until 65mph then climb out.

The process I THINK I understand in the video Phil linked to is essentially the short-field process Dayton taught me: essentially, keep the nosewheel on the ground until 65mph then fly off.

I was not taught to pay attention to RRPM once the takeoff roll began, either for standard or short field. That makes sense: so long as the rotor is tilted well back and the roll started at 220rpm (basically 150+% of the 130r “stick-back” RRPM for the M-16), it almost can’t decay to a risky RRPM on roll-out.

Shortly after I first soloed I told Dayton I was going up to practice short-field takeoffs. That’s the one time I can remember him expressing apprehension about me going up. He said that was the most risky maneuver we would do as a student, from his view, since it increased the risk of blade flap. Remember, that’s in the context of not tracking RRPM. Phil’s video specifically adds watching the RRPM, as I recall.

Anyway, all this reflection to share the idea of at least the potential for increased risk of blade flap if one flattens out the rotor on departure, from what I was taught. Monitoring RRPM when doing so - and anticipating the risk of blade flap - would be well advised, I think. And I can imagine some other gyros could carry a greater risk for this than others.

One could envision someone thinking “this process gets me airborne pretty quickly: I could get up even quicker if I put the stick more forward and push the throttle up faster”. Not wise.

As a reminder, I’m not a CFI, so take this with a grain of salt...

/Ed L
 

Philbennett

Junior Member
Joined
Aug 17, 2014
Messages
477
Location
London
Exactly so Ed the risks highlighted are real. They are mitigated in the technique i use by including the RRPM in the scan.

The key to the point is where the bigger risk is deemed o be. Is it blade sailing OR is it trying to take off behind the power/drag curve?

My view is that bail sailing with my technique (and im sure i dont own it but for the sake of giving it a name) is not possible if you monitor RRPM because if you see it decay you can safely abort ultimately. But on the positive side you unstick at a speed you can climb away at.

Plus as a kicker you are getting people used to scanning for the RRPM which is also useful post landing.

My personal view is that the technique is more efficiemt, stops flight behind drag/power curve on take off PLUS if you monotor RRPMs then not omly can you not sail the blades (unless you ignore the gauge) but when you land you are used to looking for RRPMs which keeps you safe again.

it also saves hours of wheel balance type preparation because its not involved and the aircraft take off duel or solo isnt that different where as going solo with a wheel balance technique is a big change. Anyway just 1 view.

The Cavalon accident i linked would have been impossible with my technique because with no RRPM data you would naturally just abort... instead feel was used and it went wrong even with full back stick...
 
Top