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     First Flight Prep
     Flight Testing
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Copyright © 2008 by
Randy Pflanzer
Technology Professionals Consortium
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Links on this page:
    First Flight

    Flight Testing
    Injector Balancing

    

First Flight

     

I was at the airport early Saturday to finish up the weight and balance stuff.  Back at the hangar, I was updating my paperwork and waiting for Docthrock (Matt Throckmorton) to show up when two of my fellow Rocket flyers, Tom Utterback and Jim Winings stopped by.  They knew I was getting close to flying and they wanted to check out the airplane.  Pretty soon, four additional RVs stopped by as well, on their way back from breakfast.  After chatting for awhile, they all left about 15 minutes before Matt stopped by in his Decathlon.  Matt volunteered to allow me to fly his airplane from the front seat in order to get my motor skills tuned up for my first flight.  I showed him how not to fly for the first two or three landings, but eventually, it all came together and I greased one on.  We stopped at my hangar and I thanked Matt.  After a few minutes, I looked at the great weather and decided "It's not going to get much better than this!"  So I strapped into the Rocket and taxied out, Matt following in the Decathlon.  After a low speed taxi run down the runway to ensure the Rocket tracked straight (it did), I taxied back to the end of the runway to wait for Matt to come around.  Once he turned on final, I pulled onto the runway and eased the throttle forward.

After a very brief rollout, I eased back on the stick and I was airborne.  My flight plan was to stay in a circling pattern above the airport the entire time to ensure the engine and fuel systems were operating properly.  I leveled off at 2,100' to stay under the Indy class C airspace and started turning left.  I played with different power levels but I ran mostly wide open per the engine break in instructions.  I don't remember much about the flight other than the airspeed was indicating 198 knots and all the engine temperatures remained in the green.

I only spent about 20 minutes circling.  I was anxious about making the landing so I eased the throttle back and slowed down.  I pegged the airspeed indicator at 80 knots and turned final.  The airplane felt extremely stable and solid and that MT prop was smooth as can be.  I flew her down to the runway and eased the throttle back as well as the stick.  She settled onto the runway with just a couple of squeaks from the tires.  I even made the first turn off.  YEAHAW!

I'll share a little secret with you.  All week, I'd been telling my friends and my wife that I planned to make my first flight Tuesday.  I did that knowing that I would probably fly it sooner.  You know why?  To take the pressure off of me.  I really didn't want the added pressure of an audience the first time up.  The only one who knew I was flying was Matt.  If I had to do it over again, I would do exactly the same thing.  I didn't want to disappoint my friends but I had to do what I thought was right for me and I'm glad I did.  Now I feel a little better taking it up with others around.

Another note on the first flight.  I am way behind this airplane.  It is moving faster than I can think at the moment.  I need to get more out in front of this thing and I'm sure that will happen over time, but as Jim Winings warned me, "When things happen in this airplane, they happen fast!" and he was right.  I was at altitude before I even knew it.  The airspeed build up is very quick, and the airplane left the runway in just a couple of hundred feet.  The nice thing is that she's rock steady in the pattern and easy to slow down.

Next step is to begin following a documented, step by step, process of checking out the airplane.  I'll start posting my flight plan cards as I produce them and update you on the results.  That info should be forthcoming as the weather allows.  Stay tuned.

Below you will find my flight test cards.  Each card is organized to outline the goal and objectives of that particular flight.  They contain the step-by-step plan for completing the flight and they also contain pertinent flight data on engine parameters, squawks, and other notes.  There is a general structure to these plans.  At first, the goals are to ensure engine and fuel systems work properly.  Then the flight envelope is expanded to include more maneuvers to ensure the flight controls work as expected.  Then the systems are checked out like GPS, EFIS, and autopilot.  Interspersed throughout are test plans just for the purpose of verifying squawk corrections.

Flight Testing

I began my flight testing by first staying close to the airport to make sure that the engine was going to stay running.  After a couple of flights that confirmed that all was well firewall forward, I began to focus on the flight characteristics of the airplane.  After the first three flights, I found two problems that required some immediate attention.

 1)         Correct Elevator Feel
The very first issue was the heavy feel of the elevators, especially at slow speed.  This was expected as my fellow fliers had pre-warned me of the heavy feel.  They were correct.  The heavy elevators just donít seem in harmony with the flying characteristics of the rest of the airplane.  So I pulled out the interior, seats, baggage area, etc. in order to get at the elevator bell crank thatís next to the battery.  I took the bell crank apart and used it as a guide to cut new bell crank halves that shortened the distance from the bearing to the upper attach point by 7/8Ē.  This change also required me to re-rig the elevator torque tubes to the front stick since I needed more throw.  I set the stick for maximum forward throw so it just missed the panel and hoped I had enough rear throw to miss my belly.  It turns out that I have just enough room.

2)         Correct A/P Wiring
During the first flights, I wanted to engage the altitude hold feature on my A/P so that I could concentrate on writing down notes.  When I tried to engage it, I got nothing.  Hmmmm.  Since I had the interior pulled for the elevator change, I decided to track down this problem as well.  After pulling the harness for the roll servo, I pinged each wire to make sure I hadnít crossed anything up.  It turns out that I had lost continuity on one of my wires somewhere.  There are no breaks in the wire so this was a real puzzler.  Fortunately, I had pulled two extra wires in that bundle so the fix was relatively easy.  I just pulled the pins out, crimped new pins on the extra wires and plugged them into the harness.  Bingo, it now looks like it works.

I then conducted another series of flights to verify the two changes that I made and to look for additional flight characteristics that might need tweaking.  Iím happy to report that the elevator change worked well and I highly recommend it.  The elevators have a much softer feel in the flair.  Also, the A/P now works so I can focus on flight and engine parameters, write down notes, etc, without worrying about flailing all over the sky.

After two more flights, it became obvious that I have two rigging problems.  The easy problem is that I have a heavy right wing.  This is easily fixed by tweaking the ailerons.  The more difficult and troubling problem is that the airplane flies in a left slip at cruise speed.  The ball is about two balls out of center to the left.

3)         Correct Heavy Right Wing
This is a common problem in all of the RV-type airplanes.  The problem has to do with the rounded shape of the trailing edge of the ailerons.  The solution is to lightly squeeze the trailing edge of the light aileron and use a block of wood to lightly blunt the trailing edge of heavy aileron. 

4)         Correct Left Slip
Initially, this was a puzzling problem.  I re-checked the alignment measurements of the wings, horizontal stabilizer, and vertical stabilizer.  I even checked the airfoil shape of the rudder and the alignment of the counterweight arm of the rudder with the centerline of the rudder.  These all checked out.  At the urging of Jim Winings, I ran two strings from the rear spar of the VS parallel to the VS centerline, forward to the firewall to check where the VS was pointing.  Sure enough, the VS was pointing to the left.  This has the effect of pushing the tail to the left in flight and hence, the slip.  Hmmmmm.  A couple of more checks pointed to the culprit.  Seems that all of these airframes have a twist in the rear part of the fuselage cone.  (Donít ask me why fuselages built in a steel jig canít be manufactured without any twist, but apparently, they canít.  Thanks Petr!)  This has the unwanted effect of moving the lower attach point of the vertical stabilizer spar to the right of the centerline of the fuselage.  This point is fixed because the bolt has to go through the tail wheel mounting bracket.  So, when the leading edge of the VS is centered and the spar is offset to the right unintentionally, this results in my rigging problem.  I confirmed this by dropping plumb bobs from the center of the fuselage and drawing a centerline on the hangar floor.  I then plumbed the center of the tail cone and sure enough, it was offset to the right by about ľĒ   The solution was to offset the leading edge of the VS to the right.  The question is ďHow much?Ē.  I used the dual string method again to get the VS pointing straight down the centerline.  This resulted in an offset of about 5/16Ē.  I drilled a new set of four holes in the upper attach bracket, taped a chopped up empennage fairing in place, and went flying.  It was still slipping to the left but by between a Ĺ and full ball depending upon speed.  So I moved the VS over another ľĒ and drilled my new mounting holes up from a -3 bolt to a -4 bolt and tried it again. 

The next set of flight tests were to confirm these two changes.  Regarding the heavy wing, I apparently got over zealous on the squeezing and now I have a heavy LEFT wing.  So after a few more adjustments and a few more flights, I was able to get them reasonably balanced.  If you do this on your airplane, make sure you even out the fuel load.  An unbalanced fuel load will shoot all your efforts to hell. 

I did manage to correct most of the slip.  At least the A/P can fly the airplane mostly straight at this point.  In slow flight, Iím a half ball out to the right, at mid-speed the ball is centered, and at high speed cruise, the ball is half out to the left.  The fix for this is a trim tab added to the rear edge of the rudder to give it a little kick at higher airspeeds.

 5)         Add Rudder Trim Tab
To help my feet, I went ahead and riveted a trim tab to the bottom of the rudder trailing edge.  My tab is about 8Ē high by about 2 ĹĒ wide.  I drilled out the necessary rivets and re-set the rivets with the tab in place.  My tab is on the right side of the rudder giving me some additional left rudder.  This is opposite most RVs, which have the tab on the other side.  After a couple of flights and a couple of adjustments in the bend of the tab, I was able to get the airplane to cruise at high speed with the ball only slightly off center.  I think this is close enough for now.

So after the first 8 to 10 flight tests, I feel like I have the flying characteristics of the airplane sorted out to my liking.  Did I mention how happy I am that I didnít paint the airplane first?  Iíve had to yank the interior out twice, I had to cut up and re-fiberglass the empennage fairing, and Iíve had the engine cowlings off four times in the first 15 hours.  Iíd really hate to think what I would have done to the paint job while fixing these quirks.

6)         Correct Interface between EFIS/A/P, and Garmin
With the other problems corrected, Iíve been able to concentrate a little more on the systems in the airplane.  Iíve had a problem getting the EFIS to talk to the A/P and the Garmin in the way that the manual says it should work.  After sending a few emails out, I found out that my interface wiring is incorrect.  This means pulling the boot cowl, radio stack, and EFIS units to get at the harnesses.  I pulled the harnesses apart, ran a few extra wires, and changes pins in the Garmin unit to get everything working.  I think I finally have them sorted out.  It sure would have been better to wire this stuff up on the bench and test it over there rather than inside the airplane, but thank God for the boot cowl.  I would hate to fix this stuff without it.

A few more test flights have confirmed that the EFIS is talking to the A/P and the transponder, that the transponder is talking to the Garmin, and that the Garmin is talking to the EFIS.  I can control the A/P from the EFIS and the flight plan and course info is being fed to the EFIS from the Garmin.  I actually like the map feature of the EFIS better than the Garmin, but the Garmin gives me a certified GPS.  Once the new terrain map for the EFIS is released, I think Iíll have it all.

I have been practicing my landings a lot.  It seems that either I am a horrible pilot or I just havenít gotten the visual cues down for making a smooth landing.  In fact a couple of landings have been borderline ground loops.  After asking a bunch of advice, I finally got around to checking my wheel alignment.  Well no wonder Iím having problems.  I checked the toe-in of my wheels both in the three-point and level configuration and what I found astounded me.  First off, the two wheels have different amounts of toe-in.  That problem is on me.  My left gear has about Ĺ degree of toe in while the right gear has about 2 degrees of toe-in.  These are in the three-point configuration.  When you raise the tail, the left gear goes to toe out while the right gear remains toe-in.  No wonder this things wants to dive off the runway when landing.

 7)         Correct the Wheel Alignment
There are differences of opinion as to whether a little bit of toe-in is preferred over a little bit of toe-out.  What I think is important is that both wheels need to be the same and as close to straight as possible in the three-point configuration.  Without cutting up and re-welding the axle sockets, thereís not much you can do to significantly change the camber, but the toe-in/out can be changed with shims.  Also, and this is a very important point, thereís absolutely no way to check all this stuff out without the airplane on the gear, fully weighted down to simulate full tanks and heavy pilot.  The gear leg flexes too much, which changes the camber and the toe-in/out as well.  In short, I hate the engineering on the gear leg sockets and I think itís all messed up.  The REAL fix is to shorten the gear legs a little and rebuild the sockets, but thatís another story.  My short term fix is to shim the two axles to get them as close together and as close to straight as possible.  I installed some shims from Mark and they've corrected things pretty well.

8)         Fix Rudder Pedal Interference
I encountered a problem with the rudder pedals while landing my Rocket.  On rollout, the left rudder pedal bolt head, that holds the brake pedal to the tubular frame, caught on the side of the firewall and prevented me from using full rudder.  As a result, I exited the side of the runway and my prop caught a taxi light stanchion.  Unfortunately, this ruined my whole day.  I fixed it in three ways.  First, I replaced the -3 bolts with AN363 washer head screws.  Second, I malletized the side of the firewall box to provide a little more clearance.  Three, I shorted the attachments to the rudder cables, moving the pedals a little forward.  This fits my body just a little better and gives me more throw as a consequence.

9)         Replace the Steering Arm
I installed a set of stainless steel rudder springs from Vans that replaces my Jantzi steering link.  I like the ground handling much better now.  Landings are a little easier since the springs are more forgiving.  This was a good change.

10)       Replace/Rework Lower Gear Fairings and Wheel Pants
After changing the alignment, my fairings didn't fit anymore.  I ordered a new set of lower gear leg fairings and was pleasantly surprised at the improved quality of the parts.  They are much better than the ones shipped with my kit.  Now I wish I would have ordered a new set of upper fairings as well.  In any event, I had to rework all the fiberglass parts to make it look presentable again.  I hate doing rework, but it was necessary.  Now all that's left are the wing intersection fairings.  I'm having too much fun flying at this point to stop and work on them.  They'll have to wait for some crappy weather.

Injector Balancing

One of the big benefits of having fuel injection on your engine, is the ability to tune your injectors so that you can run your engine on the lean side of peak EGT.  At that point, your engine is running cooler, has less engine deposits, and uses much less fuel while still delivering the same power as running rich of peak. 

In order to run LOP, your injectors must be sized correctly such that each cylinder reaches LOP at the same fuel flow.  Right out of the box, you will probably find that your cylinders peak at different FF due to differences in the intake flows to the cylinders.  In order to find out, you will need an engine monitor that accurately records CHT and EGT on each cylinder and can accurately record fuel flow.  For me, my GRT EFIS does all that and more.  First step is to go fly and record the information contained in the following chart. (Blank Injector Test Run Table).

I have an Airflow Performance injection system.  It is typically shipped with .028 restrictor fittings in each injector.  On my baseline run, I leveled off at 7,500' at 2100 RPM and 23" MAP, and engaged the autopilot.  I then started at about 14.5 GPH and recorded a line in the table.  After doing so, I leaned the engine about .3 to .5 GPH, waited about 5 minutes for the temps to stabilize, and recorded another line of data.  I continued doing this until every cylinder reached peak EGT and started to decline.  Now, the first couple of times you do this the engine will run rough because you'll likely have 1 or 2 cylinders reach peak before the others.  This causes them to eventually misfire as they get too lean.  Don't worry, this process will fix that so continue to lean until you have all the data.

After my initial test, this is what I found.

Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 Cylinder 5 Cylinder 6
Fuel Flow EGT w/.028 EGT w/.028 EGT w/.028 EGT w/.028 EGT w/.028 EGT w/.028
12.5 1360 1275 1268 1273 1272 1262
12.3 1362 1299 1284 1292 1292 1283
11.8 1352 1325 1314 1316 1315 1303
11.4 1340 1350 1337 1338 1333 1316
11.1 1323 1355 1346 1348 1341 1325
10.7 1311 1358 1364 1368 1354 1331
10.2 1304 1333 1357 1379 1347 1315
9.8 1304 1310 1339 1372 1314 1392

The data indicates that cylinder 1 is reaching peak far before any other cylinder.  I faxed this data to Don Rivera at AFP and he made the following restrictor recommendations: Cylinder 1 - .029; Cylinder 2 - no change; Cylinder 3 - .0275; Cylinder 4 - .027; Cylinder 5 - .0275; Cylinder 6 - .0275.

After a couple of days, the new restrictor fittings came in the mail.  I pulled the cowling and plenum and installed the new fittings.  After the second test flight, flown at the same altitude and engine settings, this is what I found.

Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 Cylinder 5 Cylinder 6
Fuel Flow EGT w/.029 EGT w/.028 EGT w/.0275 EGT w/.027 EGT w/.0275 EGT w/.0275
11.8 1364 1301 1307 1328 1313 1303
11.3 1366 1335 1327 1348 1334 1318
10.8 1353 1354 1362 1378 1358 1332
10.3 1343 1346 1372 1391 1359 1324
9.8 1330 1320 1344 1380 1334 1307

Now, the FF spread is much closer, but not quite as close as it needs to be.  After another round with Don, he made the following restrictor recommendations:  Cylinder 1 - no change; Cylinder 2 - no change; Cylinder 3 - .027; Cylinder 4 - .0275; Cylinder 5 - .027; Cylinder 6 - no change.

I thought these changes were a little strange since there was no change to cylinder 1 and we were messing with cylinders that were all peaking together.  Don explained to me that he is trying to get the cylinders to peak around 11 GPH.  Below that, the flow divider starts moving fuel around in a less predictable way.  He's not changing number 1 at this point because changing the others will drive this one down as the fuel is redistributed.

Here are the results of the third test.

Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 Cylinder 5 Cylinder 6
Fuel Flow EGT w/.029 EGT w/.028 EGT w/.027 EGT w/.026 EGT w/.027 EGT w/.0275
11.7 1349 1311 1326 1346 1324 1300
11.1 1351 1338 1354 1371 1350 1321
10.6 1347 1346 1360 1378 1352 1324
10.0 1326 1319 1336 1358 1313 1305

Now that I've got the cylinders peaking within .5 GPH of one another, I'm going to declare victory.

That completes my Flight Testing phase.  Now, the fun begins. 

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