Transcript
NARCA Eagle Next Meeting Place: Epps Airpark (NARCA field) Date: Thursday June 8, 2017 Time: 6:30 PM Program: Prop Savers by Kevin Reynolds
June 2017 201November North Alabama Radio Control Association P.O. Box 173 Harvest, AL 35749 http://www.flynarca.com
Upcoming Club Events June 10 – Monthly Aerotow, Epps Airpark June 24 – Open House and Trunk Sale
Eagle Droppings from the President: I hope everyone has been getting out to the field with some regularity the past few weeks. The runway is in great shape, the grass is growing well for a change, and flying conditions have been great. If the wind has been keeping you on the ground let me urge you to push your comfort zone and go out when it's a little bit breezier than you like. You'll find you get used to the wind pretty quickly and once you do your flying opportunities open up. Our next club activity is the Open House/Trunk Sale scheduled for the 24th of June. The date has been changed by Exec to de-conflict with Father's Day and the international boating event being held downtown on the 17th. This is a low key event with little for the club to do AFTER we get the grounds and building tidied up. Clean up of the area will be on the 23rd with open flying after, so the more folks that help out the more flying time we'll have. The only other thing on my mind is to keep your email address book current. Some folks' club-wide blasts that go out have names on them that are no longer with us. The guys that have moved out of state aren't going to come out, so maybe it's just best not to bother them. Charge something and I'll see you at the field!
Rick Nelson, President
Membership Vote Status
Jeff Youngblood passed second vote at May 2017 meeting – sponsor was Archie Phillips Scott Morales passed first vote at May 2017 meeting – sponsor is Chuck Pierce Robbie Henslee second vote is due in June 2017 – sponsor is Rick Nelson Bethany Pierce, Mark Grim, and Mark Ainsworth second votes due August 2017 – sponsors are Chuck Pierce, Archie Phillips, and Rick Nelson Rich Wegrich second vote is due September 2017 - sponsor is Al Clark Christopher Jennings and Jeff Garland second votes due October 2017. Sponsors are Rich Lawrie and Archie Phillips. Scott Morales second vote is due November 2017 – sponsor is Chuck Pierce
11 May 2017 General Meeting Minutes Meeting called to order by NARCA President Rick Nelson at the NARCA flying site (Epps Airpark). There were fifteen persons in attendance.
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Visitors: Mark Grim’s spouse Kim (Kim #1) and Scott and Isaac Morales (both prospective members- Scott is learning to fly for his work and son Isaac is extremely interested in R/C). Minutes of previous NARCA General Meeting were approved as published in the NARCA Eagle newsletter. Officer Reports: Secretary Archie Phillips: Retrieved mail on way to meeting and distributed such. There is a second vote this meeting for Jeff Youngblood. Distributed Officer Pins from the AMA (noted to attendees that they could get an officer pin next year as we know not all officers will be available for reelection) Treasurer Bob Stewart: Absent (car trouble) Vice-President Larry Holcomb: Absent (on travel) President Rick Nelson: Nelson request NARCA members straighten up the site on leaving especially putting away the chairs and starting stands. The pylon race has been indefinitely postponed as the CD is engaged in other AMA business. The swap meet went well and gave a general report on the swap meet finances. Old Business: There was a second NARCA vote for Jeff Youngblood (sponsor Archie Phillips). Motion for full membership passed on written ballot (Collected as per tradition in a Marine’s hat). Welcome to Jeff as NARCA member with full privileges. New Business: There was a first vote for Scott Morales with Chuck Pierce as his sponsor. He was accepted by voice vote. Welcome to Scott as a NARCA introductory member. After the announcement of the June fun fly Mark Grim requested that the 17 June fun fly be postponed to 24 June due to the International R/C boat Championship meet being held in Huntsville. Since there had been no public announcement of the fun fly the matter was referred to the NARCA Executive Committee (Secretary note: At the May NARCA Executive Committee Meeting in consideration of the request and it being Father’s Day weekend the Executive committee changed the date to 24 June 2017). Program: There was no program presentation at this meeting but Don Apostolico gave a review of the recent flight tips published in the NARCA newsletter and available on the NARCA website.
Archie Phillips, Secretary
What’s Going On at The Flying Field This column is dedicated to photos of NARCA member’s activities at the Flying field. Please snap a photo of whatever you’re doing at the field and email it to Al Clark at
[email protected] Include a brief note about it and I will put it into the newsletter. Come on, folks, get those cell phones out of your pockets and snap some photos! Photo from Chuck Pierce with the caption “Why I Enjoy NARCA Membership” Bethany sent me this photo last night. As I was looking at the photo, the thought jumped into my mind that this photo really captured what NARCA club membership means to me. I really enjoy the camaraderie of our club atmosphere. In this photo is a guy prepping his plane for flight with 3 other club members standing around the table chatting, joking, offering help, being friendly and fun. If help was needed any one of these guys would’ve been first in line to help. This is what I enjoy about club membership, and why I have chosen NARCA as my RC club. 2
Back In the Day This column is dedicated to photos by NARCA members from their earlier modeling days. Many of you have been in the modeling hobby for a long time, so please let other NARCA members see what you were doing/flying in the past. Email your photos to Al Clark at
[email protected] and include a brief note, and I’ll get it into the next newsletter! I received this nice photo from Don Apostolico. Here’s what Don had to say: Below is a photo taken in the 70’s of my wife Judy’s Falcon 56 powered by a Fox 40 RC and guided by a basic Kraft 4 channel radio that cost over $400.00 with tax. She did a good job flying her plane. This was also the plane I used to perform the Flying Farmer and other routines with the Blue Angels and Thunderbirds, and performed at air shows which was described in a previous newsletter. Today’s fancy stick on graphics for aircraft are taken for granted as they are printed on high tech laser or quality printers and they are simply stuck on to the aircraft surface. No such thing in 1970. If you wanted fancy graphics you designed and created them yourself. This distinctive one of a kind rainbow lace paint scheme used Nitrate/Butyrate dope over silk, and always elicited great comments from the crowd. That plane was a great flyer and trainer type aircraft.
Classified Ads If you have modeling items you want to sell, buy, swap, or donate, this is the place to post them. Please email your ad with a photo or two and pertinent details to Al Clark at
[email protected] and I will get them into the newsletter. For Sale: Sig 1/4 scale J-3 Cub kit. Partially framed up by experienced builder. One wing, stabilizer, and fuselage sides are already completed. Your chance to get a great Sig kit with some of the building already done, at a huge discount. $100. Contact Ron West at 256-883-8729. For Sale: New in the Package Spektrum Lithium-Ion Transmitter Battery - Model SPMA9602. When I purchased a new Spektrum Transmitter I purchased an extra Battery. Paid thirty-odd dollars for it at the Hobbytown. Make me an offer - How about twenty-five Bucks. Archie Phillips - My contact info is in the Roster. See photo below.
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Interesting Web Sites These are Internet links to modeling related web sites that I think you might find interesting or useful. You can check these out when you get bored with TV! Weather Forecasts Here are some weather related web sites that I use to see what flying conditions are going to be like. I’ve found these to be fairly accurate, with the Aviation Weather Report site maybe being a little better. http://www.usairnet.com/cgi-bin/launch/code.cgi?Submit=Go&sta=KHSV&state=AL This specific link will take you to the Aviation Weather Report for Huntsville, AL. https://www.wunderground.com/q/zmw:35749.1.99999 This is the Weather Underground specific forecast for Harvest, AL. Many of you are probably already familiar with Weather Underground. https://www.wunderground.com/MOS/DisplayMOS.asp?AirportCode=KMDQ&SafeCityName=Harvest&StateCode=AL This is another version of WU which just shows wind, temperature, and humidity plots. http://forecast.weather.gov/MapClick.php?CityName=Madison&state=AL&site=HUN&lat=34.7029&lon=86.7497&lg=ep&FcstType=digital This is a National Weather Service website that provides some good info in a tabular format. I sometimes find this useful for looking at an hour-by-hour forecast that covers a couple of days.
Don's Flight Tip #17 4
Understanding the Flight Envelope What is a flight envelope and why is it important to understand it? A flight envelope is the normal operating limits and performance parameters of an aircraft that results in safe flight. Failure to understand the flight envelope and operate within its limits is a safety issue and the perpetuation of the ol’ wives tail that “sooner or later all planes crash”. Have you ever wondered why some modelers can fly for years without putting so much as a scratch on their planes while others regularly drill their planes into the ground? One of the reasons is that some pilots have never been thoroughly trained to fly within the safe operational limits of the planes they fly. Well, fasten your seatbelts. This flight tip has a lot of information that will help pilots avoid many of the common pilot errors that cause plane crashes. Pilot Error, is often the result of not understanding and flying within the flight envelope often caused by incomplete or lack of flight training. The consequence is that pilot error has been and continues to be the leading cause of RC crashes. My comments are not meant to criticize the wonderful people who help others to learn to fly, rather to identify a generic training issue that is common all across the country and to offer information that will help reduce the problem. The good news is that training issues can be solved with proper information and education. The following narrative addresses a condensed ground school version of subjects, related flight envelope and pilot error issues that are important for the reader to understand to avoid pilot error crashes. This information applies to all sizes and types of planes and applying it will help modelers break the cycle of that ol’ adage that “sooner or later all planes crash”. First of all to fix a problem one has to understand what the problem is. Some who crash don’t know why they crash therefore they are destined to crash again. - Why do they crash? Well, there are 30 reasons in four main categories as to why planes crash. Some of these issues overlap into more than one of the major following categories. The following major categories are the main reasons why pilots crash their planes.
Pilot error from incomplete or bad training of new pilots with the “wrong stuff”. Equipment failure from buying the wrong equipment for the application Buying the right equipment and setting it up incorrectly Not routinely maintaining/checking the equipment correctly
So how is the “Sooner or later all airplanes crash” cycle broken?
Proper and complete pilot training – Purchase the correct equipment for the task Set the equipment up correctly Maintain and check the equipment on a periodic basis
Well doesn’t that just make sense? Elements of the Flight Envelope Once a pilot learns the elements and limits of the flight envelope, the knowledgeable pilot can spot impending crashes 5-10 seconds before the crash occurs thus avoiding the crash. Inexperienced pilots often fail to recognize when the plane is operating outside its safe parameters. To help beginners better understand the flight envelope, the following topics will be introduced to the reader: Aircraft axis
4 forces that act on a plane Stalls Stall speed versus bank angles. G Load factor versus bank angle Torque P- factor (propeller factor) Slipstream effect. 5
Adverse Yaw Tricycle gear - tail dragger techniques. Wind drift correction WDC Control Surface authority varies with speed Crosswind Takeoffs and Landings – (Detailed coverage in an upcoming flight tip)
Note the 3 Axis of the Aircraft Aircraft Axis – See illustration above All aircraft have 3 axis intersecting at the aircraft center of gravity. The Lateral axis goes from wingtip to tip, rotates around the longitudinal axis and is controlled by ailerons. The longitudinal axis goes from nose to the tail, rotates around the lateral axis and is controlled with elevator The vertical axis is oriented vertically thru the CG and the aircraft rotates around this axis when rudder is applied.
4 Forces that act on a plane
Lift is the force that is generated that directly opposes gravity. Most of an airplanes lift comes from the wings although the fuselage and other parts of the plane contribute to generating lift. Drag is the aerodynamic force that opposes the movement of the aircraft thru the air. Gravity is the pulling force generated by the earth on the aircraft which opposes lift Thrust is the force which moves the aircraft thru the air and is used to overcome drag.
When the lifting force exceeds gravity the plane climbs. When thrust exceeds drag the plane accelerates. When gravity exceeds lift the plane descends. When drag exceeds thrust the plane slows down.
Stalls A wing stalls when the critical angle of attack is exceeded. Angle of attack is the angle between the relative wind and the wing chord line and a wing can be stalled at any speed. When the angle between the relative wind and the chord line (line drawn between the leading and trailing edge of the airfoil) exceeds a certain point, airflow separates from the airfoil, (critical angle of attack) drag increases, lift decreases and controllability decreases until lift is regained by lowering the angle of attack. For most trainer flat bottom airfoils the critical angle of attack is about 14 degrees.
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Normal smooth airflow around an airfoil
Stalled Condition
Some of the main factors that affect stall speed of all aircraft Density altitude (temperature and pressure) affects stall speed High wing loading increases stall speed High G (gravity) loading increases stall speed. High bank angles increase stall speed Increased gross weight of the aircraft increases stall speed Note: A plane can be stalled at any speed. That means even at high speed a plane can be stalled by applying a high G load to the plane and or exceeding the critical angle of attack. In addition high G loads can create structural damage resulting in the loss of the aircraft.
Bank Angle affects Stall Speed 7
This is an important issue to understand. Many modelers are not aware that regardless of the aircraft size, in a 60 degree bank, stall speed goes up by 40%. Wow. If your trainer or sport plane normally stalls at 20 mph in level flight and you are making an approach at 25 mph and execute a 60 degree banked turn the stall speed is now 28 mph. The plane will stall and crash if there’s insufficient altitude to recover. This scenario describes the classic downwind stall on approach to landing with the blame often being placed on radio failure rather than pilot error.
Steep bank angles increase stall speed and, if the plane is going slow on takeoff or landing, can result in a stall/crash. This photo shows my LT 40 at about 5 feet of altitude in a 60 degree bank (approximately) at slow speed. Inexperienced pilots, who don’t know what to feel for at the edge of the flight envelope, should avoid these steep banks at slow speed at low altitude. Look at the up elevator, in this photo, which is loading this wing to about 2 g’s (see below chart for 60’ bank). This plane is right on the edge of the flight envelope but I know what to feel for when the plane is on the edge. Anyone can learn to do this but this condition should be practiced at altitude to learn what the plane “feels like” before performing steep banks at slow speed a few feet above the ground. Simply go to altitude and practice going slower and steeper and applying more G load in the steep turns until the plane becomes uncontrollable. This will make the pilot aware of the edge of the flight envelope. When you learn to “feel the edge” of the “Danger Zone” the pilot can take appropriate corrective action to avoid the stall and or crash by: Lowering angle of attack which reduces G load Adding power Leveling the wings This procedure should be practiced until it becomes instinctive as failure to take corrective action at low altitude, NOW, means another toasted aircraft. High G load factors increase stall speed and can cause structural damage
Let’s talk about High G loads. G loads are applied to a plane typically by applying up or down elevator. G loading can destroy a plane and it also raises the stall speed. Some modelers are also not aware that in unaccelerated straight and level flight the plane is operating at 1 x the force of gravity (1G) but in a 60 degree bank in level flight the G load on any plane is 2 G’s. (See 8
above chart) In this example that means that the vertical lift component that your 5 pound trainer or sport plane needs to generate to sustain level flight is 10 pounds. To increase the lift component requires an increased angle of attack by applying back pressure (up elevator while upright and down elevator while inverted) to maintain level flight. If the critical angle of attack is reached the plane stalls. Caution: G load is typically applied with elevator and can be increased to the point of stalling the wing or failure of the airframe. Stalls can occur at high or low speeds if the critical angle of attack is exceeded. Also, the higher the G load and bank angle the higher the stall speed. Additionally, lack of “Power Management” can cause high G’s and structural failure. Power management? What’s that? Power management is the variable amount of throttle settings used in flight. The amount of power used varies with the maneuver being flown and the G loading being applied. Observant readers who have seen Stars and Stripes fly (40% Carden Extra330) may have noticed that when the nose is down the throttle is reduced. This is to manage the speed-G load factor so as not to experience structural failure. The power use is performed in such a way that unless the observer is watching for it, one may not even notice it. Additionally when a very high G maneuver at high speed is executed the throttle is reduced to lessen the G load. The danger comes when one, who has not been observant or aware of power management, goes out and performs all maneuvers at full power regardless of the G loads being applied. This sometimes overloads the plane causing structural failure. Experienced pilots avoid high speed stalls or structural damage from high G loads by practicing “Power Management”. I’ve observed pilots new to modeling destroy their small and giant scale planes by over stressing them by not applying throttle management techniques. When one exceeds the structural limits, especially on a large plane it sounds like a bomb exploding - a spectacular sight to see. Foamies will usually just fold a wing or stab and lawn dart into the ground if overloaded, especially if they have been over stressed on a previous flight with unobserved stress damage. (Lack of proper preflight check) Small overpowered electrics are susceptible to overloading sometimes due to lack of significant structural reinforcement to the foam parts and when overstressed, experience in-flight structural failures. My recommendation is to give the airplane some respect and err on the safe side of the flight envelope rather the crash side of the envelope. Abrupt extreme control deflection at high speed causes high G loads that can cause structural failure. If a hard landing occurs, stop and check the plane over for damage before flying it again. Extreme Control Travels Overloading planes and structural failure is sometimes the result of pilot error or planes with massive control travels being applied at high speeds. Airplanes with massive travels are the ones who often have problems with controllability, especially on test flights. There is no need for these extreme travels, even on aerobatic planes, especially on test flights. To illustrate how unnecessary these massive travels are, properly trimmed aerobatic planes can perform virtually any aerobatic maneuver including snap rolls, shoulder snaps, Lomcevaks and other high energy maneuvers with 8-15 degrees of travel. Sport modelers by contrast, are frequently seen bringing their new trainers, sport, or scale airplanes to the field for a test flight with 30 degrees or more of control travel. These planes with massive travels are never the ones that take off bullet straight down the runway, climb out in a realistic stable manner and fly smoothly in flight. They dart right –left- right- left and then leap into the air semi out of control and gallop around the sky. No wonder so many sport planes with extreme travels are toasted on takeoff or landing. (See Flight tip #4 for discussion of recommended control travels).
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All of my competition aerobatic planes for the past 50 years, large and small, have performed all of the high energy radical maneuvers with about 6-10 degrees of low rate and 11-15 degrees of high rate travel except for 3D and Alpha flight, (flight below the stall speed)- but how many sport modelers do you see performing alpha flight? If all these planes can perform all these precision and high energy aerobatic maneuvers with limited travels, why would a sport plane need 30-40 degrees or more of travel, especially for a test flight? They don’t! This loss of control due to massive travels resulting in high speed stalls, low speed stalls and high G loads are a problem that beginning pilots need to learn how to avoid by using proper setup and pilot techniques. New pilots need to know that when one exceeds the low or high end flight envelope limits, a crash is likely. One should not be afraid of this rather one needs to understand it and know how to safely fly at the high and low speed part of the flight envelope. You certainly don’t want to discover where the limit is on a steep slow high G downwind turn to landing. How do you learn the edge of the flight envelope? It is suggested that new pilots go to altitude to play with the flight envelope limits discussed in this narrative. Learn what the plane feels like when on the edge of it becoming uncontrollable so you can recognize the flight condition and take corrective action NOW, not 5 seconds from now, as that’s too late when you are close to the ground. Avoiding and recovering from a Stall Regardless of the planes size, one must be careful to avoid the “Danger Zone” when flying at high and low speed and high G loading. Tip: Observant modelers will note that you will often hear throttle management applied when experienced pilots fly slowly and turn with high bank angles close to the ground. The increased power gives a safety margin to help avoid a stall in a bank. How much power? Go to altitude and find out what it takes for your plane to avoid a stall in a steep turn. This practice at altitude gives the pilot a degree of confidence and will improve flying skills because it teaches the feel of the plane when operating at the edge limits of the envelope. To prevent the plane from stalling or to recover if the plane has stalled simply Decrease the angle of attack Level the wings Increase power If you are too close to the ground when the plane stalls get out the ol’ dust bin. If a pilot develops the skill of safely flying slow with high bank angles at high G loadings, stalls can be avoided and t he plane can be safely flown. It looks deceivingly easy when properly performed so do not discount the importance of becoming proficient in this area of the flight envelope. Go to altitude and practice. Other Factors that affect stall speeds Flaps, slats or leading edge cuffs increase lift and reduce stall speed. Trailing edge flaps or leading edge slats change the chord line relative to the oncoming air. It has the effect of increasing the angle of attack and increasing lift up to the point of the critical angle of attack. Airfoil shapes affect stall speed. Flat or under cambered airfoils reduce stall speed but offer higher drag factors. They are also unsuitable for sustained inverted flight. Symmetrical airfoils offer less drag but have higher stall speeds. They are suited perfectly for inverted flight.
Minor flap deflection increases lift on takeoff. My 30% scale 34 pound 44cc powered DHS (Don’s Hobby Shop) Cessna 152 uses 10 degrees of flap for takeoff. Caution: Taking off with full flaps creates more drag than lift and can be very dangerous. Don’t do it. Observant modelers who have seen my Cessna 152 shooting touch and goes should have noticed the flaps fully extended to 30 degrees for landing but after touchdown the flaps are retracted to 10 degrees for takeoff on the touch and go.
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The left photo shows flaps deployed 30 degrees for landings which increases drag to slow the plane for slower touchdowns. If the wind is blowing hard, less or no flap deflection is needed as the headwind will slow the ground speed sufficient for an easy touch down. The right photo shows up elevator being used to (break the glide) slow the plane or “flair” the plane for touchdown on the main wheels. Remember that elevator controls airspeed and throttle controls rate of decent. Once this elevator –throttle skill is mastered the pilot will be able to more consistently spot land the plane at a place the pilot chooses. (See Flight Tip #1 for a discussion on this skill).
Other Forces Acting on a Plane Torque Loosely defined torque is a twisting force around an axis. On an aircraft torque is the reaction of a spinning propeller applying a turning moment to cause the aircraft to roll left (prop rotating clockwise as viewed from the cockpit). If left rotation is encountered the correction is to apply right aileron.
P-Factor (Propeller factor) Also known as asymmetrical blade effect causes the plane to yaw left at high angles of attack due to the higher angle of attack of the descending right blade (as viewed from the pilots seat) creating more thrust than the ascending left blade operating at a lower angle of attack. This offsets the center of thrust toward the right side of the crankshaft causing the plane to yaw left. It is corrected with right rudder.
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Torque – P-factor and Incorrect CG Effects For those who attended the CG presentation at a recent club meeting the above photo is the scratch built 12 foot, 45 pound B 17 bomber test flight described at the meeting. Photo was taken moments after takeoff pitching up due an incorrect rear CG. This rear CG setting was caused due to the builder using an incorrect method to set the CG location. Note the beginnings of the left roll, due to torque effect of the 4 engines described above and countered by applying right aileron. What the photo does not show is the full right rudder applied moments after this photo was snapped which was required to counteract severe left yaw created from P- Factor resulting from the high angle of attack. Full down elevator was insufficient to keep the plane from looping on takeoff due to the aft CG so read on to see how this giant scale plane was safely landed. Fortunately due to dry flying (see Flight Tip#15) various fight scenarios, the power was decreased to keep the plane from looping over the top and a certain crash of this magnificent plane. Once the appropriate power level was determined the rate of decent was controlled with power. Full down elevator was maintained, due to being tail heavy, slightly less than full right rudder due to the reduced effects of P factor, and because of the lower power setting, allowed the plane to be gingerly controlled. The power was varied to control altitude and rate of decent (see flight tip #1) and was safely landed. This successful save was one of my most challenging test flights. Challenge yourself and answer the question: If you had this happen on one of your test flights of any big or small plane would you have applied the proper procedure to save the plane or would you have crashed? If the answer is the latter I recommend the reader review the recently published flight tip #15 on “Dry Flying” procedures so one can sharpen your skill level and avoid needless crashes.
Slipstream Effect Slipstream effect is the spiral airflow that twists around the fuselage and while its effects are often considered minimal, may cause a left turning effect on the plane. Proper right thrust normally nulls out this effect.
Adverse Yaw Adverse yaw causes a plane to bank in one direction and yaw in the opposite direction due to the unequal lift and drag crated by the up and down movement of the ailerons relative to the wings angle of attack. This can be corrected by adding coordinated rudder in the turns to null out the adverse yaw but it can also be trimmed out on many airplanes by adjusting the travel on each aileron. 12
For example, when differential is not adjusted properly or the pilot does not correct with rudder application, applying right aileron in an attempt to correct the plane from going left on takeoff, can cause the plane to bank right but yaw left. This is due to the increase drag of the downward deflected left aileron into the air stream causing more drag on the left wing which results in moving the left wing backwards. The right aileron goes up decreasing the angle of attack, reducing the drag on that wing allowing the right wing to move forward creating a left yaw with right aileron application. When the left aileron moving downward exceeds the critical angle of attack on the left wing the left wing stalls and loses lift, the right wing is flying and the result is the plane snap rolls left with right aileron input. The same yaw- roll relationship is true for a left aileron input i.e. with a left aileron input is made the plane may roll left and yaw right if rudder correction is not applied and/or the differential is not adjusted correctly.
The worst example of adverse yaw I personally experienced was a test flight I did for a friend test flying his multi thousand dollar scale 144” wingspan replica of the Spirit of St. Louis. He did a magnificent job of detailing this aircraft and I thought it was going to fly like a trainer. Those familiar with the Spirit’s wing may recall it had a relatively long wing span to carry the weight of the plane but small wide chord ailerons. Small wide chord ailerons at the tip on an expanded wingspan aircraft amplify the effects of adverse yaw because the leverage is greater due to the increase wingspan. Well, after all the taxi tests, range check, and engine checks were done it was show time. The wind was out of the north which dictated a right to left takeoff pattern. Power was added with a touch of down elevator to get the tail up in the flying position and a little right rudder to keep the plane going straight down the runway. Everything was going to plan. The plane lifted off beautifully and the climb out angle was established and everything felt good. This was going to be a great test flight. Now it was time to make the right traffic procedure turn while still climbing out so right aileron and a little right rudder was added to turn the plane right. YOWWEEEEE!!!! The plane banked right and turned hard left so I added hard right rudder. This had little effect as the small rudder could not overcome the leveraged effects of extreme adverse yaw. The plane was flying away from me so I had to do something quick to get this magnificent airplane turned around. This incident is the classic case of extreme adverse yaw. It is standard practice to always dry fly before test flights to plan for various types of failures. The correction was to get off the ailerons immediately and fly the plane with the rudder and elevator. It then flew like a big trainer. The plane was brought around and landed without incident. After shutdown we checked the plane and the setup had no differential at all. I don’t recall exactly how much differential we wound up putting in the plane but it was about twice the up aileron travel deflection as the down travel deflection. It took a few test flight to get it perfect. Once the differential was set properly the plane flew like a big trainer! 13
Photo of the 12 foot span Spirit of St. Louis test flight after takeoff. Photo taken at the moment of entering a right turn prior to the extreme adverse yaw effect. Quick reaction (due to dry flying before takeoff) to this in flight control problem saved this beautiful plane. Using just rudder to steer the plane right-left, allowed the plane to be controlled and landed without incident. Thank you “Dry Flying” This Spirit of St. Louis story illustrates the significant effect that adverse yaw can have on the flight characteristics of a plane. While this example is a worst case, if the reader is observant one can see varying degrees of this adverse yaw problem on sport, scale or aerobatic aircraft at almost any flying field across the country – gas, glow, or electric. To trim out this yaw problem, the upward moving aileron must be deflected more than the downward moving aileron balancing the drag factors on both wings. How much or how little adjustment is required? This subject with flight trimming procedures was covered in Flight Tip #6 (Trimming Sport Aircraft) and the amount varies with the plane. Additionally, if any residual effects of adverse yaw exist after the adjusting the aileron travel, rudder application in the direction of turn will null out the anomaly. Don’t forget that if you are flying inverted, rudder input is opposite the aileron input.
My Carden 40% Extra 330 uses about 20% more up aileron travel than down travel to eliminate the effects of adverse yaw allowing it to roll perfectly straight. The right and left settings vary by a few degrees of travel because of the effects of torque which makes the plane easier to roll left than to roll right. For those readers who have more advanced planes and are interested in the complete advanced flight trimming schedule, contact me and I will provide you with a 2 page flight trimming bible competitors have developed over the past 30 years to properly trim aircraft for all flight conditions. Departure Stalls Beginners sometimes experience a departure stall and crash. Let’s take a look at a typical departure stall. The stall is created when pilots lift off at marginal speed, nose high and because of Torque, P factor, slipstream effect, and adverse yaw described above, the plane yaws rolls and turns left on takeoff. The inexperienced modeler will add right aileron to attempt the correction. When a right turn is attempted at slow speed with the wing at a high angle of attack the left aileron goes down increasing the 14
angle of attack on the left wing and if the critical angle of attack is exceeded on that left wing the plane will stall and snap roll left on takeoff. This is the typical departure stall. Now if the pilot had carefully lowered the nose to decrease the angle of attack and lifted the wing with rudder on a trainer, sport or scale plane with positive stability (an introduction to positive, neutral, and negative aircraft stability is the subject of an upcoming flight tip) with a little added aileron the chances of stalling the left wing are substantially reduced. Wow! I bet some readers have not heard that one before yet this is a basic technique that is more effective on typical trainers and many sport aircraft especially at slow speed. Why are these flight envelope factors important to understand? When pilots fail to fly in the safe zone of the flight profile crashes occur. Why Do Planes Go Left on Takeoff? – Excluding Crosswinds Have you ever closely watched planes fly? I mean really watch - Some modelers look but don’t see these effects described above. Many planes yaw left on takeoff or after liftoff and some actually bank right but the plane is turning left or do a wings level left turn? Some untrimmed planes cock the fuselage left while in a climb due to being untrimmed. By being observant when watching others fly you will sometimes see this effect. Proper right thrust, and differential trim adjustments will help null out some of these factors. Proper pilot application of right rudder on takeoff will also control the left turning tendency on takeoff. In short proper flight trim and pilot technique and trim will allow bullet straight takeoffs. See following summary illustration to review why planes tend to go left on takeoff. Any properly trimmed plane can be setup and trimmed to go straight on takeoff. It’s so nice to just add power and point the plane down the runway and it goes as straight as an arrow. When takeoff speed is achieved simply apply a little back pressure (up elevator) and it climbs out straight like it was on rails (crosswinds excepted).
Wind Correction Angles Another flight skill that some modelers need to master is wind correction angles. Crosswinds complicate the forces acting on a plane which is why it’s important to dry fly what you should expect on takeoff and landing so the pilot can be prepared to correct the path of the plane and not be surprised. In the strictest sense wind correction angles are not an aircraft flight profile rather it is a pilot proficiency function that is either not practiced or understood, especially by beginners. This is sometimes due to being self-taught or not being taught these relationships during their training process. This skill is important to master if the pilot is to develop the skill to competently fly the plane in adverse conditions. To maintain the correct path over the ground requires the plane’s in-flight heading be pointed into the wind to compensate for the wind drift over the ground. The heading difference between the ground track and the flight heading is referred to as the “Crab Angle” The amount of crab angle is directly proportion to wind velocity, The higher the wind speed the higher the crab angle. The diagram is self-explanatory and once the beginner understands and practices the bank angles relative to wind direction depicted in the drawing, the pilot will have a greater mastery over their aircraft. Note: To maintain the track over the ground the planes bank angle is increased and back pressure (up elevator) is applied when turning downwind. Bank angle and back pressure is decreased when turning into the wind. Learning to fly, rectangular and figure 8 patterns with intersections facing in and facing out and performed in both directions are excellent training tools and the altitude at which they are performed at can gradually be decreased as flight proficiency improves. Practicing the “Right Stuff” creates a more “proficient pilot”. That’s why my flight instruction pilot’s manual that I published is called “Proficient Pilot”. 15
Study the above illustration and the observer will see the wind crab angle relationships necessary to accurately fly a prescribed path over the ground. Mastering this skill allows the pilot to fly the plane rather than the plane flying the pilot. Note that when landing in a wind the steepest bank is performed when turning from downwind to base leg. If you perform a steep bank with G load applied at low altitude and too low an approach speed, the steep bank angle and G load will increase the stall speed. These conditions create the infamous downwind stall that has killed so many RC and full scale planes. To prevent this while on approach, bank angles should be limited to 30 degrees or less, add a slight power increase in the turn, and avoid loading the wing, which will reduce the chance of stalling. Tricycle gear versus Conventional gear take offs Tricycle gear aircraft are easier to taxi, take off and land due to the location of the main gear relative to the CG. The tricycle gear CG is forward of the main gear. This CG Gear setup is like an arrow with the weight concentration being at the front of the arrow causing it to be stable. This tricycle configuration gives greater ground handing stability than conventional gear planes. For Tricycle gear planes take off power is gradually applied until takeoff speed is attained and a little back pressure (up elevator) is applied. Right rudder is used to maintain directional control during the takeoff roll. If the right thrust adjustment is set correctly there is little to no need for right rudder on takeoff. (This assumes no crosswind)
Note the CG ahead of the main gear. This CG location makes for more stable ground handling similar to an arrow that flies straight because the weight is concentrated forward. On conventional gear planes the CG is behind the main gear making the steering on the ground more challenging as the weight is concentrated behind the gear.
When the CG is behind the main gear any left right movement on takeoff or landing, especially at high angles of attack, have to be done delicately and with precision to avoid the famous ground loop. The CG behind the main gear is always trying to move forward. It’s like shooting an arrow where the weight is back on the end where the feathers are. That arrow will not be stable. This CG weight relationship makes for a greater pilot challenge and when not handled correctly, or the airplane is not setup properly, causes the famous ground loop. You will rarely see a tricycle gear plane ground loop unless there is massive pilot error but it is quite common to see tail draggers ground loop from pilot error or setup issues. Tail Dragger Techniques and Steering Issues One of the issues that cause problems on conventional gear planes is the improper application of back pressure (up elevator) when adding throttle on takeoff believing that this will help steer the aircraft better on the takeoff run. You can go to any field in 16
America and see these yahoo right- left- right galloping semi out of control take offs culminating with the plane leaping into the air at low airspeed and semi out of control due to pilot error or improper aircraft setup. I have crash tapes (some in slow motion) full of these takeoffs that I’ve used in club flight training seminars clearly showing the out of control condition created with this pin it to the ground up elevator technique. For whatever the reason this flawed technique keeps getting handed down from one modeler generation to the next with the same negative results. All one has to do is watch, I mean really watch, and observe take offs of pilots who go straight as an arrow down the runway and lift off with about a 10-15 degree nose up climb out attitude like a real plane. Wow. So nice! How do they do that? I can tell you they don’t do it by pinning the tail to the ground with up elevator. It’s done as follows.
If the conventional gear aircraft is set up correctly with the elevator in neutral, most planes will naturally raise their tail as speed increases due to the tails angle of attack. If needed a delicate touch of down elevator to get the tail flying can be applied and once the plane is in the level flight attitude get off the down elevator or the plane may nose over as the elevator becomes more effective with increased speed. Every plane is slightly different in the amount of control input used but all use the same principle.
Rudder is the dominant right – left steering force (not the tail wheel) on takeoff and landing. The tail wheel is for taxiing. By getting the tail up into the flying position the plane is more controllable with rudder, than pinning the tail to the ground with up elevator with a tail wheel linkage setup that is so sensitive that it creates those almost out of control takeoff runs. If by chance the pilot is trying to steer the plane right or left on takeoff with ailerons be advised that delicate use of rudder is the correct control to use.
In a crosswind expect the plane to weather vane into the wind which requires delicate application of downwind rudder and a slight amount of upwind aileron to keep the plane going straight (subject of an upcoming flight tip). Can you get the plane in the air without compensating for the crosswind? Yup – but it’s often not a pretty sight to see at best and at worst another toasted airplane. How much control do you add to compensate? That’s something that the reader has to experiment with to determine how much control input to use relative to the crosswind velocity as every plane is different. These are usually fine nuanced inputs of a few degrees. Not bend a dog leg in the stick applications. In general, less is more.
Note: I keep using the term “delicate” in reference to the amount of stick movement when applying corrective control inputs. Experienced pilots use small inputs and limited travels that are learned by going to altitude and practicing the maneuvers in question until the correct amount of limited input is learned for the flight condition. Be aware that no matter how much practice one performs, if the plane is not setup correctly it is difficult to master the elements of flight. So let’s cover a technical setup issue that causes steering issues on taildraggers.
Tail Dragger Steering Issues If one is less than “delicate” on rudder control inputs, (Delicate = PC term for PILOT ERROR) Ha – or improper setup, this often results in the left-right galloping, take off run. This is sometimes caused by incorrect tail wheel linkage geometry relative to the rudder throw. Linkage geometry controls tail wheel throw sensitivity. Like massive control travels that cause control problems, many sport planes are setup with steering linkage geometry that is way too sensitive and squirrelly to be of practical use on takeoff. Just because the RTF comes from a factory doesn’t necessarily mean the settings are optimum. Add to that, pilot error from coarse control inputs, this massive travel and linkage geometry issue quickly becomes a control problem which can be minimized by modifying the steering linkage. See below photos and note the significantly extended tail wheel steering arms to desensitize the steering.
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Note in every photo, that extended steering arms are used to desensitize the tail wheel steering. On average, the length of the steering arm is doubled compared to what the factory provides as you can see in the photos. One would think that a tail wheel assembly that costs $50 to $100 dollars would be configured properly. Small planes also have this problem of steering issues related to linkage geometry. Most people I’ve flown with have modified their assemblies to desensitize the steering. Additionally, a few holes are drilled in the arm to adjust the steering sensitivity to fine tune the steering authority. This modification makes the rudder the dominant steering force on takeoff and landing rather than the tail wheel. The small downside is that in a strong crosswind the ground steering authority is reduced unless the modeler properly sets up the radio travels and expo settings. The fix is simple. Program max travel (140-150% depending on your radio) for your rudder and use a lot of exponential to get more steering authority at extreme stick deflections. (See Flight Tip # 5 Servo setup Issues - related to programming control travel percentages for max resolution) Even with these extended steering arms the tail should still be raised on takeoff. The transition from tail wheel down to tail up, however, will be far smoother with this modification providing the pilot does not create other takeoff pilot errors. For those who wonder what all the lead, feeler gauge and Master padlock is doing on one of the above tail wheel photos please refer to Flight Tip #4 Control Setup Issues for explanation. If the plane noses over on takeoff there could be some problem with the gear setup or the throttle is being applied too fast, especially with planes with long landing gear legs and sitting nose high. If power is applied in a slower deliberate manner, get the tail up to flying attitude, steer the plane with rudder until a safe flying speed is attained, apply slight backpressure - up elevator, to lift off and establish a realistic rate of climb, the result will be a takeoff that looks like a real plane. Ahhhhh that’s how it’s done. So Nice. Control Surface Effectiveness Here is another in flight issue that creates problems for inexperienced pilots. Sport modeler crashes on takeoff or landing are sometimes caused because they use ailerons only at slow speeds to turn the plane. Ailerons are not the dominant turning force at slow speeds. Wow – What’s this guy talking about? On aircraft with positive stability (sport aircraft) ailerons are not nearly as effective as rudder at slow speeds. (One can force the turn with ailerons with extreme travels – but then you get into the problem of slow speeds, high angle of attack on the wing with the downward moving aileron exceeding the critical angle of attack and the subsequent left snap roll into the ground when right aileron is deflected. Rudder is the more effective turning force when combined with aileron at slow speed on most sport planes with positive stability because of wing dihedral. It’s important to understand that control effectiveness varies with airspeed. Ailerons are generally less effective, compared to rudder inputs at slow speeds or just above the stall speeds. I’ve demonstrated this many times to students in both full scale aircraft as a flight instructor and RC model aircraft. Simply take the full scale or 18
model plane and slow it to just above stall speed with a little power to maintain level slow flight and then quickly move the ailerons full -stop to stop- left-right-left a few times. The plane barely responds because of the slow airspeed. Then at the same slow speed quickly apply full rudder both left- right-left and WOW! Fasten your seatbelt and hang onto your hat. The nose will swing hard left- right left with great authority. The point is at slow speed rudder is more dominant than ailerons on virtually all planes with positive stability. That means if a pilot is using ailerons only to correct a problem at slow speeds the response is anemic and may be insufficient to correct the flight condition compared to using rudder and aileron. For those who fly properly trimmed aerobatic planes that are neutrally stable and have little or no dihedral, rudder deflection, at virtually any speed results in yaw – not roll. I qualify that because leading edge sweep, at slow speeds and high angles of attack acts like dihedral to induce some slight roll with rudder inputs even on a neutrally stable plane. Since most in our club fly sport type planes with positive stability, rudder application with a plane with dihedral, induces a roll component to the plane at slow speed. When rudder is coordinated with a slight amount of aileron input the control effectiveness is significant and the chance of stalling the wing with the downward moving aileron is reduced due to the reduced down aileron travel input. These rudder inputs are very delicate inputs not 30 degree deflections. Coordinating rudder with aileron is a flight instruction issue and is easily solved by incorporating this skill training into the flight instruction schedule. To learn how much input to use go to a safe altitude and slow the plane down and practice how much rudder and aileron are needed in various attitudes. You will find that once you learn the relationship of rudder to aileron at various speed you will be able expand your personal flight envelope. Learning this skill 10 feet off the ground on takeoff or final approach is not conducive to success. Make your mistakes at a safe altitude. Cross Controlling The rudder is also used to increase landing accuracy by cross controlling the plane to perform a slip to a landing. Cross controlling is the application of aileron in one direction while applying rudder in the opposite direction. A number of readers have seen my Sig LT 40 shooting touch and goes. Rudder is always used while flying that plane, sometimes using full rudder deflection to control the planes slip rate of decent in the turns and on final approach. The casual observer probably can’t tell that sometimes full rudder deflection in one direction and full aileron deflection in the opposite direction is used to control the glide path. This maneuver is called a slip and acts like flaps on a plane that doesn’t have flaps. A slip is a pilot technique that will enhance your ability to more accurately control your touchdown point rather than flying past runway center and having to walk several hundred feet to pick up your plane. You can become skilled in this procedure if you practice. When one becomes proficient in this skill, control inputs, done with a reasonable degree of precision, make the control inputs hard for observers to see. Wow! That’s a lot of information to digest for new pilots but it is essential to master these skills and others related topics discussed in previous flight tips as the alternative is to not learn it and keep crashing. No Fun. Becoming proficient will help break the “sooner or later all planes crash mantra”. One should note that if you do all of the things noted above you decrease the chances of crashing. The number 2, 3 and 4 reasons noted above for crashing have been discussed to some degree in other flight tips and those must also be done correctly to enhance your chances of not destroying your aircraft. Flight profile accidents are avoidable if one practices the techniques described in this flight tip. I recommend that readers who want to or need to improve their flying skills internalize cause and effect of these topics and consciously apply this information when you fly. Additionally it is recommended that beginners, especially, read this narrative at least twice as you will see things the second time through that you missed the first time through. To sum up, this ground school overview is meant to make newer pilots aware and give the experienced pilots a refresher and flight instructors a reminder of some of the factors that cause crashes. Flying within the envelope promotes safe flying and exceeding the flight envelope causes crashes. Applying this information will obviously improve a pilot’s skill level. By contrast, crashing is certainly the hard way to learn and by practicing to “get it” your “fun meter” will go off scale when you fly the “Right Stuff”. Until next time, Fly Safe
Diagrams, photos and illustrations provided courtesy of Gemstone Publications 19
