Jun 25th

Call to Action. Adding Spiral recovery Tasks to the Practical Test Standards (PTS).

By Paul Hamilton

Intentional or unintentional spiral dives have caused a number of fatalities throughout the world. Therefore,  I have decided to pursue getting spiral dive recovery into the Practical Test Standards (PTS) so all new pilots and CFI's will start training for this important maneuver in the US and hopefully worldwide. Additionally, this will also emphasize the importance of this important safety concept for pilots and instructors while performing a flight review required for all pilots ever 24 months in the USA. If we are successful with this, we can make spiral training visible and available to all pilots in the US within 24 to 30 months.

I have contacted the FAA and discussed this addition to the PTS so here is my plan based on this conversation. It is more than likely we can achieve this so I am asking others for input to this important evolution in trike safety. All input is appreciated.

There are two specific topics that need to be achieved to accomplish this:.

1. Justification for addition to PTS

2. What specifically to test for in the PTS which will be the basis of training for spiral dive recovery.

Before we get to the specifics, let's look at the closest item in the PTS that would relate to this subject.

The PTS is located at www.faa.gov/ training_testing/ testing/ test_standards/ media/ FAA-S-8081-31.pdf or you can purchase a paper copy at http://www.pilot-stores.com/asa-practical-test-standards-sport-pilot/

In the PTS Power Off Stall Task, the turning stall task is made to simulate the base to final turn and specifies a maximum 20 degree banked stall to represent this base to final scenario with no more than a +/- 10 degree variation. Hopefully this maneuver is thought by instructors to cover this base to final stall/spiral avoidance as a starting point to avoid this situation altogether in the first place. Typically the inside wing falls and the recovery is the same as a spiral recovery - reduce angle of attack (AOA) while leveling the wing, EXCEPT, repeat EXCEPT, you add throttle to recover at a slow speed and bank angle below 45 degrees  RATHER  than let off the throttle to recover in a spiral dive when the nose is pointed down. Significantly different recovery methods based on the bank angle.

Back to the JUSTICICATION before we get to the specifics of the spiral recovery maneuver.  I can easily write a paragraph describing the problem but specific instances involving pilots in accidents is important to make this happen. I will put this into another blog/article to keep it separate and on track since this may create some discussion on this topic. Here we will focus on the specifics of the PTS task here.

Where should this be in the PTS as a task? Well it can be either in the Slow Flight and Stalls Area after the whip stall and tumble awareness OR in the Emergency Operations Area. The Slow Flight and Stalls Area is similar to the tuck tumble task for WSC/trikes and similar to the Spin Awareness for the Airplane Task which is in the slow flight and stalls for airplane. The Emergency procedures is appropriate since it is an Emergency recovery procedure. Ideas and input as to where the appropriate place in the PTS are appreciated from CFI's and DPE's.

The problem is how I teach this is not easily replicated for student to practice nor testing during a checkride. I now teach this with a two step process:

1. Get into a very high 60 degree bank and recover from there. Nose falls and the recovery procedure is initiated by simultaneously decreasing angle of attack, level wings and reduce throttle. Additionally at a very high bank angle, push out to demonstrate the stall and how this will initiate a spiral as the wing drops and things get worse. Again, the recovery procedure is initiated by simultaneously decreasing angle of attack, level wings and reduce throttle.

2. Get into a steep bank angle (example 45 degree bank performance maneuver) and bumping the bar to a higher bank angle as if there was some event that put the student into a very high bank angle (example 60 degrees) unable to maintain altitude at full throttle. Nose falls and the recovery procedure is initiated by simultaneously decreasing angle of attack, leveling wings and reducing throttle.

There may be a difference of opinion of exactly the sequence among flight instructors, but  I teach a simultaneous pitch/roll/throttle where a sequence 1,2,3 can also be utilized for specific wing/trike situations. The PTS tasks needs to be open enough to accomplish either method depending on the specific trike/wing.

So how do we provide a recovery technique to initiate and recognize a spiral that can be thought by CFI's and practiced by the student on their own.

Here is my first cut at this in the PTS to accomplish this task. The objective is to obtain input before I submit this to the FAA to have it incorporated into the PTS.  Here is a first cut at the two tasks as a starting point:


REFERENCES: FAA-H-8083-5; Aircraft Flight Manual(AFM)/POH/AOI,  .

Objective. To determine that the applicant:

1. Exhibits knowledge of the elements related to power on spiral recovery.

2. Selects an entry altitude that allows the task to be completed no lower than 1,000 feet AGL (Typically this would be at least 2000 AGL).

3. Establishes a high banked minimum 45 degree turn maintaining altitude at 1.6 Vs  as specified by the examiner. Applicant simulates unintentional spiral by bumping to higher bank angle not to exceed 60 degrees and nose down attitude 30 degrees. Transitions smoothly and immediately from nose down high banked turn to level flight with 0 to 30 degrees bank angle.

4. Minimizes altitude loss, with no high pitch angle recovery, with immediate correction to new heading with no more than 180°correction in direction from simulated spiral initiated heading.

5. Recognizes and recovers promptly after the spiral is initiated  by reducing the angle of attack , leveling the wing and reducing throttle to return to a straight-and-level flight attitude with a minimum loss of altitude appropriate for the specific weight-shift control aircraft.

6. Returns to the altitude, heading, and airspeed specified by the examiner.




REFERENCES: FAA-H-8083-5; Aircraft Flight Manual(AFM)/POH/AOI,  .

Objective. To determine that the applicant:

1. Exhibits knowledge of the elements related to power off spiral recovery.

2. Selects an entry altitude that allows the task to be completed no lower than 1,000 feet AGL.

3. Reduces throttle and establishes a high banked minimum 45 degree descending turn at 1.6 Vs  as specified by the examiner. Applicant simulates unintentional spiral by bumping to higher bank angle not to exceed 60 degrees and nose down attitude 30 degrees. Transitions smoothly and immediately from nose down high banked turn to level flight with 0 to 30 degrees bank angle.

4. Minimizes altitude loss , with immediate correction to new heading with no more than 180°correction in direction from simulated spiral heading.

5. Recognizes and recovers promptly after the unintentional spiral is initiated  by simultaneously reducing the angle of attack, leveling the wing and increasing throttle as appropriate to return to a straight-and-level flight attitude with a minimum loss of altitude appropriate for the weight shift control aircraft.


6. Returns to the altitude, heading, and airspeed specified by the examiner.

Jan 2nd

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

By Paul Hamilton




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:






[bil-oh] /ˈbɪl oʊ/




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...






Sep 6th

A study in recent trike accidents

By Rizwan Bukhari

I am so sad at the news of Bill Crow passing away. His Revo crashed and he sustained many injuries. He was air lifted and passed away in the hospital.

Before we go any further, I want to be very clear in saying that all I want to do is to find some answers. This is a fact finiding mission and that is the only purpose here. As we know that in a year and a half (since last may 2014) This is the fourth Revo trike incident/accidents. Out of the four, three proved to be a fatal. This is not good statistical data. And I feel this is important to point out and discuss what caused them. I can think of atleast 6 or 7 Revo accidents.

Now I know many of you trike pilots are thinking this but I will put it in words that we would like some answers from the industry leaders and their mouth pieces who leave no stone unturned to promote their product via blogs as the best trike money can buy.

I hope you realize that every life lost affects many other lives. The pilots that perished flying your machines, their death impacted their children, spouse, friends and their entire life style. That is a huge cross to bear.

If I was to compile a data of total "top of the line trikes" sold and total accidents and fatalities of these trikes. The percentage so far would not look very favorably towards the manufacturer and the dealers. And hopefully we can find an answer for pilot safety, whether it is more training or some other solution, whatever it maybe.

So lets examine some of the accidents and what caused them.
First Gerry of Birds in Paradise perished last May, he had modified the vent system, that caught fire during the flight and we all know that much but no one has ever answered why he felt the need to modify the vent system? Was it a poor design?

Then Craig died and according to eye witnesses his Revo trike and the wing seperated. Should any trike (forget top of the line trike claims for a second) behave like that. Craig, like Gerry was an experienced pilot. I would like to know what happened there?

William in Virginia Revo stalled and crashed in five to six feet deep water. The trike was totalled but he should be counting his blessings that it didn't happen on asphalt or the outcome could have been fatal.

And now Bill Crow....this is very sad. These four accidents have happened in about one and a half year.

And while we mourn the loss of our good friend Bill, the loss of Scmidt's brother and near death experience of the gentleman flying Henry's trike with a Revo wing are fresh in memory.
 I hope you can give us an explanation with the same enthusiasm as you promote your products. Because pilot lives are important too.

Another thing while we are at this topic is that majority of trike pilots already are talking about (and I am pretty sure that you are aware of this) your wing being prone to instability at high speed that could cause spirals, but what do I know. And if that is true, the solution should have been to fix the problem with a poor desinged or tuned wing rather than shoving Spiral Dive Recovery as PTS manuvers to protect yourself from impending law suits . So the question is that how many lives will be lost before we fix these problems?

I sincerely hope that I am not offending the manufacturer and the leaders, but firmly making my point that next time you aggressively promote or sell your product, please also be prepared to answer about the fatalities and imperfections too and what are you doing to fix them. Because pilot lives matter.

We all learn from our mistakes, the important question here is what have you done or are you doing to make sure that no more lives are lost.

Thank you,



(PS: My intention here is to learn to clarify some qustions that are on many mind and find some solutions that are on your mind).

Feb 9th

Delivery Flight in My New Revo -- The Actual Trip!!!

By Glade Montgomery
Tomorrow morning I catch a 5:15 am flight from Seattle to Tampa.   I'll have dinner in Tampa with friends, then head to Zephyrhills.   With first light Monday morning (or perhaps a little sooner), I'll be at Larry's hangar, eager to begin final preps -- for the long ride home -- in my new Revo.

I plan to make posts here, at least each evening if circumstances permit, describing my progress.  Y'all are welcome to direct-track my progress at this site:


So long as the DeLorme InReach device is working as intended (and, of course, assuming I remember to turn it on), there should be position updates (including velocity and altitude) once every two minutes.
Mar 22nd

Joy and frustrations of a student pilot

By Bob Lemke


What I would like to solicit from this blog is other's learning experiences along with their mind set. As I type this I've received 9 hours of instruction, 7.5 of those hours in the last three days. The first 1.5 hours was at my CFI's airport, the rest at my hangar/home in my airpark. 


The joy comes from flying again after a 37 years absence. 40 years ago I soloed with 0 hours because back then nobody was doing tandem hang glider flights yet, let alone giving dual instruction. I bought a used Seagull III and three other beginners from work joined me in the quest to learn how to fly. We learned in the Sierra foothills just east of Sacramento, California and on our 2nd outing one of the beginners crashed, destroying the Seagull and placing him in the hospital for 3 weeks. I became a dealer for Seagull to receive better pricing and placed a order for 3 new gliders for us remaining students. When the 3 of us resumed training, instead of the 20 minute drive to that foothill site, we drove 3 hours to a coastal site named Dillon's Beach with a 100' tall sand dune hill. There was a lot of physical effort involved in climbing with our wing in the sand but the reward was launching into a constant sea breeze that elongated our flight time and more importantly the soft sand in the LZ for our beginner pilot landings. With that long drive it was a serious time commitment so we always camped and had two or three days of learning per trip. After many trips we felt we were ready to return to that foothill site and continued training there. Between the 100' sand dune and the 500' high foothill site, all flights were short compared to the time of hiking our gliders up those hills. The time had come for our 1st "altitude" flight at a place north of Clear Lake, California called Elk Mountain with the LZ in the dry creek beds next to the Middle Creek Campground. The launch was 3500' AGL above the LZ. This area is famous for thermals so as low time pilots the three of us launched early morning to insure a 10 minute sled ride to the LZ. That was at least 5 times the air time of the other two sites. All three of us wound up doing what the more experienced pilots predicted, and that was pulling the bar in a bit past minimum sink and flying with more speed, hence a shorter flight. But 10 minutes in the air did give valuable input as to where each of us had set up our hang point CG, and so we could make adjustments on future flights to insure our CG setting would provide minimum sink for hands off the control bar straight and level flight. Getting the right CG proved very important for our next altitude site which was Big Sur. This site was famous for giving that first altitude flight so I was looking forward to that trip already having some altitude flights at Clear Lake. The club I belonged to went to Big Sur every Thanksgiving due to the whales migrating south that time of year. Nothing curls your toes like flying over a pod of whales in a prone position and your wing acts as a sound amplifier when they surface and force air out of their blow hole. It is loud. The club owned a old hot rod 4X4 Ford truck with a 427 and manual transmission that pulled a custom trailer built to accommodate 24 gliders. i know a lot about that truck because when I didn't feel comfortable about conditions on the launch hill, I would drive the truck back down the hill with just my glider on board. This happened more times than I'm willing to admit but hell I was one of the lowest hour pilots in the club and had every intention of surviving my early learning phases to become a higher hour pilot. On one of these Big Sur trips I didn't exercise my previous good judgement and launched above the fog before it had burned off because there was a good size opening in that fog along my proposed flight path. Well I'm sure anyone reading this is going to think what happens after you launch and are flying that VFR path and it closes back in again? You would be correct and I shouldn't have launched because in the time it took me to reach that clearing in the fog, it had closed in. This was why I mentioned how important it was at the Elk Mountain site to properly dial in my CG attach point for hands off minimum sink. When your in a white out that is your only option, remove input to the control bar and experence that feeling of time stretching out, where every 10 seconds feel like a minute. I am however keeping track of the time waiting for a break in the fog because my due west flight path will take me over highway 1 and then the Pacific Ocean. I finally saw a break in the fog and turned towards the opening and once there was relieved to see Highway 1 just west of my position. Total relief but that was short lived because on further observation I had no idea where I was in respect to the LZ and didn't know if I should fly north or south over Highway I. I chose north and that was incorrect, wound up landing 4 miles north of the LZ at the gas station/greasy spoon. After folding my wings I had breakfast wondering how long it would be before the truck/trailer would find me and pick me up. During the course of eating, 3 other pilots landed there to prove I wasn't the only idiot to launch into a sucker hole in the fog and after breaking out of the fog heading the wrong direction.



I got off subject, damn I'm good at that. Well back on subject, these early days of flying lit a fire under my ass (or lit my ass on fire) and 3 years after learning to fly hang gliders I was at my local FBO taking lessons in their Cessna 150 trainer. This was a low budget flying club that even though they had the new 152s, I preferred the old 150 for two reasons, manual flaps vs the slow moving electric, and more important for the budget minded, the 150 only recorded tach time hours unlike the 152 Hobbs time. Lower RPM settings would net more log hours and less billing hours. On this note you are probably aware I'm a budget minded person and as such I'm having some diffculty with time to solo and instruction rates. If memory serves I think the 150 I rented from the club I belonged to and paid monthly dues went for $25 per hour wet and the instructor was an additional $15 per hour. Granted this was 37 years ago. I feel like I'm getting a good rate from my current CFI at $150 per hour in his trike at my hangar/home location. However, time to solo might be different. I don't want or expect to solo at 0 hours like I had no choice in my hang glider. I did solo GA aircraft at 10.8 hours and as a newly minted solo student pilot moved my touch and go's from my 2400' FBO field to a little airstrip my U/L friends were using at 1200' in length. I got to practice short field and spot landings all day at that little strip which was only 3 miles from my home strip. I got pretty good at this and when my club had its Fun Day with flour bomb drop, balloon burst, and spot landing competition I was eager to participate. Only problem was students weren't allowed, so I was bummed. I could understand a low hour student pilot could get into trouble attempting the balloon burst and even the simple flour bomb drop, but spot landings? This is what we practice all the time we are accumulating, not just hours flying straight on cross country flights. I spoke up, the powers to be contacted their insurance agent and the green light was given to allow the students to do spot landings. That was the very first 1st place flying trophy I ever received, still proud to this day.


So this gets me back to the first paragraph, I have 9 hours dual and have the impression from my CFI that my first solo is further away than the 10.8 hours I soloed the 150. I know we need to trust our instructor's judgement as to our flying abilities but input from others would be appreciated. What was your flying experience before trike instruction? How many hours before solo in the trike. How did you feel about your CFI? I really want the good, bad and ugly.


Here is my thoughts on flying. As a little boy I was a tree climber for the perspective of being above the ground and the solitude. As I grew older I would climb mountains for the same reason, to escape the 2D world and enjoy a 3D experience. I will never fly as a means of transportation and as such would never ever fly to a schedule. I'll leave that to the pros. Unlike my hang gliding days when so much time was committed to driving to the flying site and hence a bit of pressure to get some air time even if conditions were less than perfect, now doesn't exist due to my home/hangar fronting a taxiway and just 900' to the active runway. Yep, with no time commitment envolved in getting to the flying site, I have the luxury everyday I wake up to decide if conditions are benign enough to serve my level of experience. Life is good retired at a residental airpark.


Feb 20th

Revo v. Tanarg

By Glade Montgomery

I'm a new WSC pilot, and am loving it.  I purchased an AC Buggy prior to my first lesson.  I soloed a couple of months ago, and have been flying the heck out of that Buggy (somewhat cold this time of the year here in the great State of Washington --  but, oh well). 

Like many new pilots who start with a more "junior" level aircraft, I've quickly developed the itch for something more substantial.  I happened to have significant hangar exposure to AC Tanargs, and could not resist feeling they were rather awesome.  On top of that, they're obviously much better suited for my 6'3" (short-torso, long-legged) frame than is my little Buggy. 

I'm also a computer guy, and could not help but encounter incredibly impressive online references to the Evolution Revo.   I spent a lot of time on that company's website (much more real info offered there than you'll ever find online regarding AC products).  The more I saw, the more I was convinced Larry Mednick is not merely an incredible pilot.  This guy is positively passionate -- beyond determined to make the best WSC aircraft possible, and in regard to every detail. 

Frankly, I like the best.  Indeed, I somewhat crave it. 

I've not yet flown a Tanarg, and plan to do so soon.  This last weekend, however, I had my first opportunity to see and fly the Revo.  I was on a business trip in San Antonio, and decided to extend it by flying to Tampa. 

As above-intimated, my expectations had been raised to a very high level.  Were they disappointed?  To be very candid, not even in a little tiny bit.  Larry had a series of Revo trikes in various stages of production, allowing me to carefully examine (and in minute detail) the engineering and materials involved at every level.  There was only one element I saw that looked remotely pedestrian.  It was the mount for the BRS (which is of course supplied by BRS Aerospace, and is not an Evolution product).  It was, indeed, fascinating how that particular element looked out-of-place (in a sense inferior) in comparison to all the other elements in the Revo trike. 

The one sad thing about my trip is the weather did not cooperate.  Larry, his dad Phil and staff were all beyond terrific.  The weather was contrary.  We managed to do 20-minutes real flying time in Larry's own Revo with 10-meter wing.  But an amazing 20 minutes it was.   Speed, agility, control.  I so much wanted to spend more time.  Alas, I had the deadline of a return flight home. 

So far as I can presently see, it appears to me the downsides in the Revo versus Tanarg are less-prevalent storage (the Revo offers no multiplicity of soft-pouches, as does the Tanarg), and total pricing that's a bit higher.  I expect to do extensive real-life testing of a Tanarg in the very near future, and will report further at such time.  In the meantime, I invite comment from any others with interest.  

Apr 23rd

What do we need to know? What can we learn from Gerry's accident in Hawaii

By Paul Hamilton

Gerry from Birds in Paradise, a commercial training operation  in Hawaii had a fatal accident March 11, 2014. Gerry was a huge influence on triking and myself and we mourn his death and will miss him greatly. I flew with Gerry’s operation for 5 months, 24,000 miles in Gerry’s trikes and know Gerry from the old days of Hang Gliding, we have been friends for decades. However, with this loss, I feel it is important what can we learn together as pilots to help us all in the future.


Yes there is allot of speculation about what happened to Gerry in Hawaii. What does everyone need to know to learn and be safe to avoid what ever happened, to make sure it does not happen again and we all learn from his mistake is simply:  Do not  modify your trike (including/especially the fuel system), without the expertise, engineering background, manufacturers consultation/approval  and/or experience for similar trike modifications or it could end badly. Simple.


What exactly happened, we will all form opinions, speculate and may never know. For every pilot/wife/child out there, what happened exactly does not really matter. Let me say it one more time:  Gerry was modifying his fuel/venting system with the intent of carrying more fuel. This ended badly.

Here is the actual accident report which I will make comment on after:

NTSB Identification: WPR14FA135
14 CFR Part 91: General Aviation
Accident occurred Tuesday, March 11, 2014 in Kekaha, HI
Aircraft: EVOLUTION TRIKES REVO, registration: N98EV
Injuries: 2 Fatal.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

On March 11, 2014, about 0910 Hawaiian standard time, a special light sport Revo Evolution Trikes weight-shift control aircraft, N98EV, impacted terrain and was consumed by fire in Kekaha, Hawaii. Birds in Paradise, LLC., owned by the accident pilot, was operating the trike under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certified light sport instructor and student pilot sustained fatal injuries; the trike was destroyed. Visual meteorological conditions prevailed and no flight plan was filed for the instructional flight. The trike departed Port Allen Airport, Hanapepe, Hawaii about 0850 and the introductory flight was intended to take 60 minutes before returning to the airport.

A second Birds in Paradise certificated flight instructor (CFI) was giving instruction in another trike while flying in close proximity with the accident trike. He stated that about 0615 that morning he met up with the accident pilot at the company's facilities. They began to take their respective trikes out of the hangar and he noticed the accident pilot was on a ladder routing compressed air into the accident trike's fuel vent. The second pilot commented to the accident pilot that the fuel cap was still affixed on the tank and removed it for him, which produced a "pop" sound from the compressed air escaping the system. They wheeled the trikes over to the staging area and greeted their student pilots shortly thereafter. After fitting the students with flight suits and helmets, the pilots gave them a briefing and departed around 0850.

After departure, the accident pilot told the second pilot that he was going "on company," meaning that they would communicate to one another on the company frequency 123.450; this was the last transmission the CFI heard from the accident pilot.

Approaching the Barking Sands class D airspace, the second pilot transmitted over the company frequency that he was switching to the Barking Sands frequency to receive a clearance from the control tower, to transition through their airspace as a flight of two.

As the CFI's trike was approaching the northwest side of Polihale Beach , he descended to about 600 feet above ground level (agl) and observed the accident trike about 1,000 feet agl and 75 feet away horizontally at his 1-o'clock position; that was the last time he saw the accident trike flying. The CFI and his student performed two near-360 degree turns over the ocean and attempted to contact the accident pilot over the radio. They noticed smoke on the base of the ridgeline and maneuvered over to the area.

The trike came to rest at the base of a ridgeline about one nautical mile east of Polihale State Park. The main wreckage was consumed by fire but all major structural components were located within the wreckage debris area. The accident pilot had recently had problems with the fuel system suctioning the fuel supply out of the main vent line (located in the belly of the aircraft). In an effort to rectify the problem, he routed the vent line up the mast and through the keel pocket toward the trailing edge.

The wreckage and a camera were recovered for further examination.

End of NTSB report



Paul’s comments:

Fuel venting is a critically important part of the design to keep the engine running. Not enough pressure the engine will stop. Too much pressure and a number of things can happen, lines/tank/fittings can leak/burst, fuel pressure could rise and pop the carb venting onto the exhaust, vent line could pop spewing fuel all over………. Plenty of options that will be batted back and forth.


Since I fly a Revo I have received calls from concerned pilots/instructors and I am pretty sure this unfortunate accident is the result of unauthorized modification of the fuel system by someone who is not an engineer and should not have been making such modifications. To all pilots, do not modify your trike without the practical experience on the modification being performed, engineering background to perform the modification or manufacturers consultation/approval  for the modification.


This is a very simple lesson for all. If you have not learned it yet, please learn from this.

Jan 20th

What initially rolls the trike wing and what creates billow shift/washout/twist change. Five fundamental forces/moments

By Paul Hamilton


There is plenty of speculation about what "initially" rolls the wing and creates billow shift/washout/twist change. We tend to focus on only a few and there are five fundamental forces. Three that help and two that do not. Note there are many more but here are the five  that are the greatest contributors.  We will look at these FORCES individually to get a basic understanding.  We are going to ignore the anhedral/dihedral and roll coupling because it complicates matters and we are looking at the FORCES and resultant MOMENTS that initially roll the wing.


 Forces helping us to roll:


1. As the weight is shifted to one side that weight shift moves the center of gravity to one side creating a moment rolling the wing. Gravity pulling down on the weight of the carriage and lift pulling up on the wing. As an example we will say the bar is moved 6 inches with a 1000 pound carriage to get 6000 inch pound rolling moment on the wing simply from weight shift. Let's call this "1 WEIGHT MOMENT" for short. This is the most straight forward and easiest to understand.


2. As the weight is moved over, it loads up the wing which creates uneven loading on the heavier wing side and the flexibility of the wing of the loaded side creates more billow shift/washout/twist change. Let's call this "2 WING LOADING ROLL" for short.


3. As we rotate the wing at an angle the weight can be broken down into two components, a component perpendicular to the wing and a side component . This can most easily be seen in this diagram. Let's call this "3 KEEL PULL" for short.




Note for this example the side load is 350 pounds pulling the keel to the side from basic gravity creating billow shift/washout/twist change. Note this force starts with any movement of the bar/shifting of the weight. One degree is 17 pounds and 30 degrees is 577 pounds. This is a huge force pulling that keel to the side starting billow shift/washout/twist change initially with the movement of the bar starting a turn.


We have all these factors helping us turn. The big question is how much does each of these three specific forces effect the turn. We will cover this later but they are different for every wing.


We have two specific forces working against us for rolling.  Both work against airplanes the same as trikes. We will number them consecutively since we are forces


Factors hurting is from rolling


4 MASS. Newton's laws of motion. Back to the basics for review:


Newton’s Basic Laws of Motion


Newton’s First Law: “Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it.” This means that nothing starts or stops moving until some outside force causes it to do so. An aircraft at rest on the ramp remains at rest unless a force strong enough to overcome its inertia is applied. Once it is moving, its inertia keeps it moving, subject to the various other forces acting on it.


Newton’s Second Law: “Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration.” When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force. This takes into account the factors involved in overcoming Newton’s First Law. It covers both changes in direction and speed, including starting up from rest (positive acceleration) and coming to a stop (negative acceleration or deceleration).


Newton’s Third Law: “For every action, there is an equal and opposite reaction.”


In triking, we have this 100 pound (more or less), 32 feet (more or less) wing above us that must be moved. This is a pretty formidable force which many ignore. Take a 32 foot long pole weighing 100 pounds and try to roll it 30 degrees in 4 seconds. Takes allot of force/effort, more than you would think.




Here is a new one for some. As we roll, the wing going down sees a greater angle of attack than the side going up which creates  a lower angle of attack, thus this slows down the rolling. However, the billow shift/washout/twist change relieves this roll dampening by reducing the angle of the airfoil on the down going tip and increasing the angle on the up going tip. Again how much billow shift/washout/twist change is a question which we will cover later. First an example to look at the actual roll dampening angle of attack increase for a rigid wing or trike with no billow shift/washout/twist change :


In a steady state start to finish, 50 MPH airspeed, 4 seconds to roll from level to 30 degree bank, with no billow shift (stiff wing), how many degrees is the angle of attack increased from the lowering wing with a 32 foot wingspan?


Lets use 50 MPH (70 FPS feet per second) for this. First we need to figure out how fast your tip is going down.
Your tip is 15 feet out and with a 30 degree bank it travels about 9 feet (8 in an arc) in an arc as it drops. So it is dropping at about 2 foot/sec.
So as it drops 2 FPS into 70 FPS air the change in angle is about 1.5 degrees. Again note this does not have any billow shift/washout/twist change. Stiff wing.


With a stiff wing and no billow shift/washout/twist change how much force out on that tip is that?


If we have a rigid wing with no twist and the desired roll rate adds 1.5 degrees of angle of attack on the wing about 15 feet out on the tip what is the force of 1.5 degrees additional angle of attack? Some basic math produces a force of 75 pounds. Calculating a moment for this we can compare to the weight shift moment we calculated above: 12 feet out for a moment of 10800 inch pounds. Note this is significantly more than the 6000 foot moment for the "1 weight moment" alone.


So we know that with no billow shift/washout/twist change, considering ONLY weight shift and roll dampening ONLY,  it is going to be much longer than 4 seconds. Almost twice as long. Note this is ONLY 2 of the 5 total forces for initial rolling. Add force "4 MASS" makes it harder/longer and "2 WING LOADING ROLL" and 3 KEEL PULL" make it easier with billow shift/washout/twist change.


To summarize,  we now have 3 forces helping is roll 1 WEIGHT MOMENT, 2 WING LOADING ROLL and 3 KEEL PULL. Note that 2 WING LOADING ROLL and 3 KEEL PULL BOTH create billow shift/washout/twist change.  We have both 1 MASS and 2 ROLL DAMPENING slowing/not helping roll.


Quite the mix of forces/factors. All of these forces come into play as the bar is moved to initiate a turn. Yes some believe that as the wing starts to drop and the rushing up air  helps billow shift/washout/twist change however this may or may not be is a secondary effect which is a result of the primary forces.


Which ones are more influential. Two of the four are pretty much the same for all similar wings, the 1 WEIGHT MOMENT help,  and the 4 MASS moment hurt. All others 2 WING LOADING ROLL, 3 KEEL PULL and 5 ROLL DAMPENING are effected by  billow shift/washout/twist change. It should be noted that the force from the 2 WING LOADING and 3 KEEL pull is the same but the effect with billow change/washout/twist change is different.


Why do some wings roll faster than others? Because the 2 WING LOADING ROLL , 3 KEEL PULL and "EFFECTIVE" 5 ROLL DAMPENING are effected by  billow shift/washout/twist change.


Faster rolling wings have more billow shift/washout/twist change. Slower rolling wings have less.


A rigid wing will not roll fast enough to be flown safely with 1 WEIGHT MOMENT force alone so billow shift/washout/twist change is needed. Again how much billow shift/washout/twist change is accomplished when the weight is shifted depends on the specific wing. Each wing is different.


So how much does the billow shift/washout/twist change in a turn, the following video shows plus and minus 6 degrees at the tip with one of the fastest rolling wings in the world.




So we know we only need 1.5 degrees to overcome the roll dampening to at least get the lift on each wing tip equal. We are getting 6 degrees in the above video for the fastest turning wing abruptly turning 45 to 45 degree turns. From this measured look at twist change for this wing that probable was one of the highest billow shift/washout/twist change, a good approximation for maximum twist change is 6 degrees plus and 6 degrees minus. Most other wings/situations will be probably be less. We can also see that it does not take much billow shift/washout/twist change to overcome the 1.5 of 6 degrees   "5 ROLL DAMPENING" force.


I would assume most wings are able to overcome this roll dampening force to provide less lift on the down going wing to roll fast enough to fly safely under the pilots control.  This is the magic of the FLEX wing.


This is a diagram showing the lift distribution of the wing in a turn with the twist greater than the 1.5 degrees needed to overcome the roll dampening










May 22nd

Hawaii Quik Fatality

By Magdi Shalash
Steve Sprague a fellow Brother triker,LSRM & an FAA Safety inspector for over 20 years succumbed to fatal crash on a Quik with a 280lbs passenger from California ,in KAUAI announced on friday NTSB Jim struhsaker 
-Eye witness who knows Steve ,who heard 2 subsequent pops before the aircraft hits the Ocean water has more to say on this newspaper link
Can we stay tuned to this & keep our P&M friends posted if unaware
Aug 29th

Does everyone need an expensive, high power, fast trike?

By Paul Hamilton

Recently, there have been a number of comments that EVERYONE is pushing EVERYBODY into expensive, high power, fast trikes. I would like to set the record straight as to my feeling about this.

Does everyone need an expensive, high power, fast trike? Simply… NO.

Here is my story about my decisions to buy the trikes I bought.

I first put a trike undercarriage on my modified hang glider in 1981. A Fugi Robins  engine. About 30 HP. Not much. It would barely get off the ground at 5000 foot density altitude but it was awesome to get flying in a trike. I had a great time with this. Fast forward to 2001.

I decided to buy a two place trike since my wife/girlfriend wanted to go up and move on from Hang Gliding. It was allot of money so I economized bought a Cosmos 503 (verses a 582) because it was light weight, less expensive, and I liked the wing. Soon after I got it I flew this slow Rotax 503 on a cross country from Carson, down the Sierras, up to Mount Whitney 14,000 and the trike Odyssey was filmed.

See www.youtube.com/watch?v=glVFOSgNBXE

I flew this slow, underpowered trike to 17,000 feet, flew 250 pound students to 10,000 MSL regularly,  trained many pilots. Did I need an expensive, high power, fast trike? NO.

Than in 2010, the FAA cracked down and my experimental was no longer allowed to be used for flight training. I waited for the LODA. Nothing. So I decided to buy a trike. By this time everyone was flying the 80 HP Rotax 912 and EVERYONE is pushing EVERYBODY into these more expensive, high power, fast trikes. I simply could not afford a 912 so I bought an Apollo Monsoon 582 S-LSA when I decided to go into trike flying full time.

Again, I would fly it to 10,000 feet with 250 pound students, etc…. I was making a living at flight instruction in a Rotax 582. Did I need a need an expensive, high power, fast trike? NO. However, it is a 14.5 meter stiff wing and had wind turbulence limitations. I had to shut down training earlier than I wanted.

After 3 years and my third Rotax 582 engine which operated great all the time, I wanted a smaller wing that I could blast through the bumps with an easy handling wing I could increase my flight hours since I had to turn many flights down when the wind came up and it got bumpy during the day.

If I had a smaller wing, I could fly more hours and everyone would be happier. Bottom line, a smaller wing needs more horsepower . So after 3 years of flying full time I decided to sell my great Apollo Monsoon 582 and go to a 912S so I can get a smaller wing.

OK which trike? Here are the reasons why I choose a Revo, generally in the order of importance which helped my decision:

Topless small wings.

Easy to get in and out of loading and unloading people (similar to my Apollo Monsoon)

Easy handling/response for ease of flying and safety/recovery in the bumps

Almost everyone who calls and asks about buying a trike wants a Revo.

Super sexy looking.

Made in the USA with easy parts/great service.

Did I have to have an expensive Revo? No but it allows me to fly comfortably is more bumpy and windy conditions.

In fact we have a number of 503, 582, and 912 80 HP trikes at the airport here and the pilots are very happy with them.

Again. Do they need an expensive, high power, fast trike? NO. Not if you can live with the limitations.  

However, if you can afford a trike and you want to climb faster, get there quicker, fly in stronger conditions and be more comfortable overall, spend as much as you can and get the trike you want. You basically get what you pay for.