QuickTalk 29 - Q-2 HINTS
- Category: Q-Talk Articles
- Published: Sunday, 31 August 1986 07:11
- Written by Jim Masal
- Hits: 1334
We had some very educational, informal and daily bull sessions in the homebuilder's tent on the flight line at OSH. During one, Duane Swing related his valuable experiences and a QBAer who was there encouraged me to get Duane to write it up for QUICKTALK. I asked.
You asked for it, and now here it is: the 10 most critical items that could lead to ground handling difficulties in a Q2/Q200. Keep in mind that a combination of 2 or more means that correcting any one may not solve a ground handling problem.
1. WING ANGLE OF INCIDENCE. This is the relationship of the wings, as assembled in the fuselage, to a level aircraft. I know - you all put them in right the first time. CHECK AGAIN. Make a couple of female templates of the canard and main wing using the foam hotwire templates to construct these FEMALE templates. It would be best if at least 2 different BL locations were checked to insure proper wing twist (wash out). You may have to round off the contour portion of the templates to compensate for the glass layups. Transfer the level line from the original template to the female (not chord line). Now level the aircraft and place the templates at their proper BL location and check, with a level, to see if all is OK. If not within 1/2 degree or so, you may want to get in contact with Gene Sheehan to get a more precise incident measurement method. Keep in mind that the old GU was installed at +1 degree and the LS at 0 degree. If you're going to be in error, make sure it is on the + side of these measurements. The main wing should be at 0 degree in both cases. Remember, it's the relationship between the main wing and canard that is most important.
2. GROUND ANGLE OF ATTACK. This is the relationship of the waterline of the aircraft to the ground. This can be checked with a protractor level on the outside armrests and should be 7 1/2 to 8 degrees. To correct for any discrepancies, you must either change wheel size or change the tail height. The tail height is the most commonly reworked area, and consists of cutting a slot, starting at just below the rudder, forward enough to clear the tailspring rod, then cutting an inverted "V" on the fuselage from the bottom just ahead of the tailspring to connect with the previously cut slot.
Once the "V" piece is removed, the tailspring can be repositioned to give the proper ground angle of attack.
3. AILERON RELEXER. This is the device used to adjust the ailerons up or down as needed. Many builders have told me they have a reflexer but don't know what to do with it. Simply stated, the reflexer is used most often to reduce lift on the rear wing (reflex up), thus providing more weight on the tail wheel during take-off and landing. How much UP, do you say? Three sixteenths of an inch to 1/4-inch trailing edge up is a good starting point on that first flight. We have found that if we adjust the reflexer in flight to give us a 4-degree up ELEVATOR at a power back 100 mph pattern speed, this then provides us with the proper amount of elevator for a tail down landing, REGARDLESS of weight or CG location. The 4-degree elevator up happens to be where we placed the wheel fillet and is a handy reference. Please remember, as you move the AILERON reflexer up - the ELEVATORS will move up so long as you maintain the same flight attitude, thus providing more elevator for landing. Keep in mind that we haven't flown with the new LS airfoil and this relationship may not be the same.
4. WEIGHT AND BALANCE. We all know what this is, but many Q-2's have been damaged by not properly weighing the airplane and incorrectly determining CG location. DOUBLE CHECK before you fly and establish a MID CG for the first several hours of flying to get used to your airplane. DON'T attempt a full gross operation in one step. Add weight in 25 to 50 lb. increments until full gross is reached.
5. WHEEL ALIGNMENT. More than one Q2 has "bit the dust" due to this problem. Don't assume that just because it was "right" on the wing jig, it will be "right" with all the weight on it. You can check this at night by placing a cardboard sheet in the center of the airplane and removing the wheel through bolts. Shine a light through the axle hole onto the cardboard and check one side against the other. They should be within 1/4" of each other (1/2" max. out of alignment). I don't think it make much difference toe out - toe in - or neither, just make sure they're close to the same (I'm not sure about how much out of alignment is permissible; check with Gene if in doubt).
6. BRAKES. If one brake has more stopping power than the other, you are guaranteed to have brake-stopping problems. Hard braking with a light tail will spin you around faster than you can believe.
7. ELEVATOR TRAVEL. One Q2 I flew had a mush (not pitch buck) at about 75 mph indicated. Landings could not be made three-point even with 3/8" reflexer. The builder had damaged this airplane in high-speed taxi tests at least three times. The flight instructor test pilot had flown the airplane almost 50 hours and it had been signed off for cross-country. A check with a protractor level showed maximum down elevator set at about 12 degrees. After properly setting elevator travel, the pitch buck changed to 64 mph indicated, and corrected the 3 point landing problem. This builder was absolutely positive he had set his elevators properly the first time.
8. TAIL KING PIN GEOMETRY. Here, I am referring to the pivot pin for the tail fork assembly. This pivot pin should be as close to vertical as possible and WILL require cutting and welding to achieve this vertical position. Usually, once the pin is changed to the vertical, the tail will be lower by an inch to 1 1/2" and the fork must then be modified to bring the tail back to the proper height (remember, 7 1/2 to 8 degrees ground angle of attack).
9. ENGINE POWER. A Revmaster engine developing only 50 or so hp at take-off power will lengthen your take-off roll by at least 50%. This translates into more time on the runway and more possibilities of a ground accident. Make sure you are getting all the power available (approx. 2800 rpm minimum, static).
10. MAIN WING MODIFICATION. Many builders are adding "fancy tips" to the Q2/Q200. Please keep in mind that any added high lift device (drooped tips, for example) will disturb the delicate balance between canard and main wing and may have to be compensated for by adding more reflexer than normal. Without a reflexer, DON'T DO IT.
11. (So I can't count) CANARD CHARACTERISTICS. Most canard airplanes have a pitch-up tendency on take-off that requires a FORWARD movement of the control after breaking ground. This is not what most pilots are used to and WILL result in over control, in most cases, of first flight. A common scenario we hear all the time goes like this: "I rotated the airplane with full aft stick (just like the flight manual suggests) and when it came unglued, it pitched up so rapidly I thought something was wrong so I chopped the throttle and promptly stalled the canard and ---CRUNCH---one more broken airplane." My suggestion here is to NOT use full aft stick. Trim for nose up (about an inch or so elevators down) and rotate the airplane AFTER flying speed has been achieved. (NO - don't look over at the airspeed indicator. You will need ALL the concentration possible to keep your airplane in the center of the runway). Simply wait until the tail comes up (about 60 to 65 mph), wait a few more seconds and gently lift the airplane into the air. Attitude flying is very important to learn. Keep the horizon in sight over the nose at all times during your take-off and climb.
12. COMMON SENSE. I'll throw this one in as a bonus. Use all the common sense you have in the early stages of your flying. For instance, don't fly when tired or on medication. Don't fly if crosswinds are beyond your ability. Don't fly if runway length is marginal; don't fly if temperatures are 105 degrees out of Denver; don't fly with known defects in your airplane, etc., etc.,
13. T-TAILS. I'm on a roll now and can't stop. The T-tail can do several things for you.
A. Give better longitudinal control.
B. Stall at any angle above about 14 degrees causing severe rudder yaw.
C. Cause a pitch down right after take-off if set in the full nose down position (sound impossible but at least one builder installed the T-tail trim to work opposite the regular trim system).
D. Create additional drag.
E. Add pilot workload.
CONCLUSION: If you can handle all the above, have at it.
14. CABIN ERGONOMICS. I'll give you this one free. If you're still in the building phase, arrange as many hand-operated items as possible on the left side. Throttle, mixture, carb heat, cowl flap, T-tail trim, reflexer actuator, switches, etc. This will then allow your right hand to do the flying.
15. WING SURFACE WAVINESS. Almost forgot this one. This problem has been with us for a long time, especially with the old GU. Fellows, keep 'em smooth and add the vortex generators on the GU if you want to STAY out of trouble.
BONUS, BONUS. You all listen up now. If all else fails, covert to a Tri-Q. After all, how else can I afford the time to tell you how to make your Q2/Q200 safe.
Well, that's it. Can't think of another thing. If you want to talk about it, call Scott on (513) 890-1925. As for me, I'm going flying.
Duane Swing N1711Q
P.S. Almost forgot, you Tri-Q drivers write QBA and let us all know how you're doing.
ED. NOTE: he DID think of something else a couple weeks later:
17. REVERSE AILERON STEERING. This is a tendency for the airplane to turn opposite the deflection of the aileron control. A typical reaction of a pilot starting to turn left (for example) will be to "turn right" with the control stick. This action further aggravates the turn to the left and can end up in a ground loop or worse. A very important lesson to learn is to "lock" your aileron right/left control once on the ground and steer with your feet. That is, in fact, what the rudder pedals are for, ain't it?
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