Jan 15th

Thoughts on safety.

By Bryan Tuffnell

Why are so many trike pilots dying? We've heard lots of answers to that, most of which I don't buy. God isn't lurking behind a cloud with a Lee Browning taking potshots at unlicensed pilots; if engine failures had to be fatal there wouldn't be a whole lot of hang gliding going on; if higher performing trikes were dangerous how come so many of us are clocking thousands of hours in them?

The root cause of the majority of triking accidents is surely that the pilot lost control of the aircraft, for whatever reason. And yet trikes must be about the easiest aircraft to control. What's going on?

I don't see many stall related accidents; nor is tumbling much of a feature. You've got to be trying to get into trouble through pure pitch. Trike pilots have little direct, independent control of yaw. Trikes don't spin. I'll bet dollars to donuts that most accidents happen because either the pilot can't roll fast enough, or far more commonly, because they can't remove bank - they are locked out of a turn.

This is topical, with all the discussion about roll that's been happening. It's also a pet subject of mine (hold me down).

Every three axis and rotary wing pilot knows how to coordinate a turn. Every trike pilot should know to pull in to initiate a change of bank, and to push out to turn a roll into a constant rate turn. Yet I believe that this lack of what should be a fundamental skill is killing pilots.

This is where the fuss about spiral dives and slipped turns and Arrow wings come from. What's the solution? I see three possibilities:

1 Manufacturers dumb down wings to cater for inadequate skills.

2 An upping of the standard of instruction, somehow.

3 A rating system for matching pilots with trikes.

Higher performing trikes are not harder to fly. There aren't killer wings. There are some trikes that ask their pilots to have a basic comprehension of the roles of pitch and throttle in banked flight, nothing more. I think having instruction that includes Turns 101 could save lives, and is the answer. I don't know how to make that happen.

 

What do you good folks think?

Jan 8th

How a trike rolls presented with a totally new perspective 2

By Paul Hamilton

 

 

This presents a completely different mindset  to look  at the trike rolling into a turn.  It was presented by RB so I will do my best to convey the message/concept. Historically, we have been looking at shifting the weight under the trike wing creating the turn. Forget all that for a minute and open your mind to a different perspective, a new way of thinking about how a trike rolls into a turn.  Simple. We are not shifting our weight under the wing to roll it, WE ARE  TILTING THE WING ABOVE THE TRIKE carriage which starts the turn.

 

 

 

This can be easily seen in this video. Note that the bar is moved, the wing tilts above the trike undercarriage the trike under carriage (with the camera attached) initially do not move much. Then after the wing tilts you can see the trike undercarriage/camera get into the turn AFTER the wing is tilted.  You can see this most clearly flying straight going into a steep turn and also coming out of  a steep turn. This can be clearly seen in this video.

 

http://www.trikepilot.com/videos/view/yaw-string-on-front-tube-showing-trike-flying-sideways-at-times_25064.html

 

 

 

 

Look at the simple physics. As an example: you have a 1000 pound trike undercarriage and a 100 pound wing. You have 1000 pounds verses 100 pounds, TEN TIMES the mass trying to oppose each other. Which one is going to move more, simple: the lighter weight wing. Yes it could be 5 to 10 times based on the specific weights but we will use 10 here to make the math simple.

 

 

 

So with 10 times the difference in mass, basic physics provides us an easy way to quantify this. You tilt the wing 40 degrees and the undercarriage moves 4 degrees.  Exactly as shown in the video.

 

 

 

So we rotate the wing, the lift vector goes to the side so we start turning. Hopefully we all remember this horizontal component of lift. The problem is that our momentum 1100 pounds at 70 MPH (or what ever speed/weight) wants to keeps us going straight based on Newton's First Law of motion.

 

 

 

So now we have a trike initially being pulled to the side from the changed lift vector, turning but pointed straight. Kind of a mess to start. It appears we are flying sideways to the relative wind. That pesky sideways adverse yaw we know happens but debate exactly how.  Well over time, however many fraction or seconds it takes, the trike yaw stabilizer (nose angle/billow/wheel spats/tip rudders or what ever you want to call it), the trike stabilizes in yaw track the trike into the turn. That pesky adverse yaw goes away. At about the same time (before, during or after which can be debated) the undercarriage swings out from the centrifugal force and we are in a coordinated turn.

 

 

 

Make no mistake, we are shifting our weight, changing our CG under the wing which helps roll the aircraft, but start thinking of it in a new way/perspective and perhaps it will make more sense.

 

 You can see from the video clearly that for a trike the wing tilts more than the carriage moves to start the turn.

 

 

 

I know all this perspective is very hard for anyone to swallow after we have been taught what we are shifting our weight to initiate a turn. Yes, again, this weight shift is correct but based on physics we are tilting the wing MORE than shifting our weight under the wing to turn it.

 

 

 

How are hang glider turning dynamics fundamentally different from the Trike? Weight ratio.

 

 

 

Look at the hang glider 70 pounds and the pilot at 170 pounds. Only two and a half difference verses 10 for a trike. So the pilot verses wing ratio is significantly different tilting the wing less and bringing the pilot underneath the wing more. Should we continue to base all our highest levels or roll based on a different animal?

 

 

 

Why is everyone's perspective of the weight shift trike turn initiation, weight shift rather than tilting the wing? We have all been brainwashed from the hang glider designers from day one. I am totally guilty of this myself. It started as we were infant pilots and grew. It goes to the fundamental principles of learning for humans: Primacy- we learned it first creating a strong almost unshakable impression, Readiness - we want to learn to challenge and keep us safe, Exercise - it has been repeated so much it is continually reinforced, Intensity - we practice it and imagine it during flight plus we are passionate and emotional about it as we debate it.

 

 

 

With all these fundamental principles of learning engrained it will be hard for many to embrace this new concept.

 

 

There you have a completely new perspective of looking at roll for the trike. We have a long way to go to develop, understand and evolve our sport so perhaps this new perspective will be helpful.

 

Jan 2nd

Firesleeve or No Firesleeve, that is the question

By Rizwan Bukhari

Hi all,

 

I was reading up on Rotax 912 engines and realized that same 912s come with Firesleeve and  some without Firesleeve. Which got me thinking why some engines on trikes have Firesleeves and some do NOT? Is this a manufacturer's discretion and some order engines with Firesleeves installed and some without it? and is this an important safety concern?

 

Following is the picture of an engine with firesleeve on it's fuel lines. (The firesleeve is orange in color in this picture).

 

My limited understading is that the purpose of firesleeve is to sustain an engine fire for 5- 15 minutes. Hopefully enough time for you to take necessary steps for your safety.

 

Now my question is

1) Howcome in the above picture, there is no firesleeve on the fuel lines running to the carbs? Are there only few critical areas where a firesleeve is needed?

2) Howcome some trike engines come with them and some don't?

3) Are they important safety item for trike pilots?

4) And the most important question is that can a Firesleeve prevent a Fuel Line Vapor Lock? Or does the Firesleeve NOT play any role in preventing a Fuel Line Vapor Lock?

 

Thanks for your help.

 

Regards,

 

Rizzy

 

 

 

 

Jan 2nd

Twist and Washout in the Trike Pilots Handbook and Why Billow was replaced

By Paul Hamilton

 

Background:

 

When the FAA Weight Shift Control Aircraft Flying Handbook was being written, one of the objectives was to standardize the terminology so that the WSC trike could most easily be understood by existing and new pilots.

 

 

 

The term billow was initially used by hang glider manufacturers with the original Rogollo wings to add material so the wing was not flat. The nose angle was 90 degrees and the sail was designed to be 95 degrees. At this time this was considered billow so the term "billow" has hung on over the years.

 

 

 

In fact with my hang glider design background,  I personally used this term in the manual along with wing "twist" and "decreasing angle of attack" towards the tips. My FAA review team asked "what is this billow term?. We do not see it in any credible aerodynamic description". The dictionary term was interesting and did not look like any thing related to sail design:

 

 

 

billow

 

[bil-oh] /ˈbɪl oʊ/

 

noun

 

1. a great wave or surge of the sea.

 

2. any surging mass:

 

billows of smoke.

 

verb (used without object)

 

3. to rise or roll in or like billows; surge.

 

4. to swell out, puff up, etc., as by the action of wind:

 

flags billowing in the breeze.

 

verb (used with object)

 

5. to make rise, surge, swell, or the like:

 

A sudden wind billowed the tent alarmingly.

 

  

 

It was explained that all these ancient "Tribal" terms from old times/technology needed to be updated/modernized to commonly known aerodynamic principles. I was initially perturbed/irritated with this but I moved on.

 

 

 

rIt was also brought to my attention that the current FAA reference 2005 for trikes (Lucian/Hal Trikes- Flex Wing Flyers) Page 3-29 Flex Wing Flyersdoes not have the term "billow" anywhere. It uses the common aerodynamic terms "Twist" and "Washout" as the concept was introduced. Again on page 3-39 Flex Wing Flyers the word twist and washout were used to describe turning. No reference or term "Billow" anywhere in the book or  anywhere in any credible aerodynamic resource i could find with an exhaustive search.

 

 

 

I was convinced/forced to comply that both "Twist" and "Washout" were credible aerodynamic terms and we did not need to invent billow to confuse the issue.

 

 

 

So I added in the Aerodynamics section page 2-3 the common aerodynamic terms twist and washout and addressed the term billow to transition everyone over to the established aerodynamic terms on page 2-3:

 

 

 

Wing twist is the decrease in chord angle from the root

 

to the tip chord, common to all WSC wings and ranging

 

from 5° to 15°. This wing twist is also called washout as

 

the wing decreases its angle of attack from root to tip. The

 

term billow was originally used for the early Rogallo wings

 

as the additional material in degrees that was added to the

 

airframe to create the airfoil. It is still used today to define the

 

amount of twist or washout in the wing. The WSC may not

 

have twist/washout when sitting on the ground, and must be

 

flying and developing lift to display the proper aerodynamic

 

twist characteristic of WSC wings. [Figure 2-6]

 

 

 

 

Again on Page 2-13 twist and washout are described in turning on page 2-13:

 

 

 

Longitudinal Axis— Roll

 

Turning is initiated by rolling about the longitudinal axis, into

 

a bank similar to an airplane using aileron and rudder control.

 

To turn, shift the weight to the side in the direction of the turn,

 

increasing the weight on that side. This increases the twist on

 

that side while decreasing the twist on the other side, similar

 

to actuating the ailerons on an airplane. The increased twist

 

on the side with the increased weight reduces the AOA on the

 

tip, reducing the lift on that side and dropping the wing into a

 

bank. The other wing, away from which the weight has been

 

shifted, decreases twist. The AOA increases, increasing the

 

lift on that wing and thereby raising it.

 

Thus, shifting the weight to one side warps the wing (changes

 

the twist) to drop one wing and raise the other, rolling the

 

WSC aircraft about the longitudinal axis. [Figure 2-24] More

 

details on the controls that assist wing warping are covered

 

in chapter 3, which should be considered with use of the

 

controls in the takeoff, landing, and flight maneuvers sections

 

of this handbook.

 

 

 

 

Again on Page 3-9

 

 

 

Roll Control System

 

Control bar movement from side to side controls the roll about

 

the longitudinal axis. The wing attachment hang point allows

 

the carriage to roll around the wing keel. Thus, it can also be

 

looked at from the carriage point of view, when the control

 

bar is moved side to side, the wing rotates around the wing

 

keel relative to the carriage. [Figures 2-31 and 3-19]

 

It would fi rst appear that moving the control bar to one side,

 

thus shifting weight to the opposite side, could alone bank

 

the aircraft. It is true that shifting weight to the right would

 

naturally bank the aircraft to the right and put it into a right

 

hand turn. However, the weight alone is not enough to provide

 

adequate roll control for practical flight.

 

As weight is moved to one side, the keel is pulled closer to

 

that side’s leading edge. The actual keel movement is limited

 

to only 1 to 2 inches each side of center. However, this limited

 

keel movement is sufficient to warp the wing, changing the

 

twist side to side (as discussed earlier in the aerodynamics

 

section) to roll the aircraft [Figure 2-24] by changing the

 

lift side to side. Simply, the shifting of weight from side to

 

side pulls the keel toward the leading edge on that side and

 

warps the wing to roll the aircraft.

 

Besides the keel shifting relative to the leading edges and

 

crossbar, overall roll control is adjusted by the designers to

 

fit the mission of the wing through sail material/stiffness,

 

leading edge stiffness/flexibility, amount of twist, amount

 

of travel the keel is allowed, airfoil shape, and the planform

 

of the wing. [Figures 3-20 and 3-21]

 

 

 

 

 

So there we have it, why we used Twist and washout instead of billow and how the wing turns from the shift of washout and/or change in twist...