I decided to take the airplane down to modify before I start flying my last 12 hours of testflying. It had become clear that the Turbo was not working as advertised.
Lots of data crunching eventually let me to compare the engine setup as it is to what it was before. When the engine ran on a piper Aztec, the only change I made to make it fit to my Velocity was that I left off the RAM Air intakes for the engine and the turbo. I thought that both would just suck the air in as a static port type. It has become clear that that that is not the case.
The MP data oscillating didn’t help make a clear decision. All components from the Turbo system were removed and inspected, and none were found to be deficient.
Now we have arrived at the last possible item in our list. Now, we might expand the list once again, or even go back to certain items we looked at before. So we need to feed the Turbo air, more like force feed. That means that at this point we need to make a scoop to transport air to the turbo.
I started out with going to Lowe’s, and the plumbing section. I bought some 2” pipe, a few elbow connectors and a 3,5 inch to 2” transition piece. The plan was to route the pipe pieces, glue them together,cut the pieces lengthwise and use both halves as templates by duck taping the inside and then curing a layer of fiberglass in both. After drying, we take out the pieces and cut the excess, then taping both halves together and fiberglass another layer to secure them together.
In the meantime, I used an extra turbo inlet and fiberglassed one layer of BID around it, let it cure, cut two sides, and that was the start of the transition piece that would connect the pipe to the turbo inlet. I did shape it so that if I needed another pipe to feed from the other side of the oil cooler, I could cut it to shape and add it on. I also added another layer of BID to strengthen and air proof the complete unit. For now, I hope it will be enough with the one scoop. The data will show us once we test fly.
All this took a few days, as fiberglass needs to cure and harden, and that takes time. Two weeks later, I am now complete with the turbo inlet RAM Air Scoop. Of course, work gets in the way as well, so I will have to wait a few more days before I get to try it out.
As discussed earlier, through my 28,5 hours of flying I have come to the conclusion that the turbo is not working, and needs RAM Air to feed the turbo compressor inlet.
So today I started with once more removing the cowling, and remove the waste gate, as it was the only item not inspected yet again. After a few hours of work, I got the waste gate removed sandwiched between its space close to the firewall and middle accessory case. I kept one side of the exhaust pipes connected in position to fit it back correctly.
All pipes had a white coating inside.. looking at the inter webs that has residual from running at lean position.. which made sense as I had done that at the previous flight for a long time at altitude. It also showed up in the turbo exhaust pipe, and through the waste gate, although clearly the valve moved while gas came through. That made me feel good that the system was working, but I got this far so I took the waste gate operating cylinder apart. The valve moved freely when I disconnected it.
When I opened the oil operating valve I noted that all seemed clean, and moving, and the springs were all in great shape and not broken. I put it all back together and tightened the bolts, before I tried to reinstall the waste gate back onto the exhaust system. I wasn’t able to align it and so I requested Aad to come and assist me the next day.
Together with Aad, it took a whole afternoon to perfectly align all pipes and fittings. All oil lines were connected and it took until the next day to do a runup to check it all. We noted no issues, other than some oil leakage in three places. Two were noted quickly as the source was clear, the third drip came from behind the engine accessory area, and was not quite sure from where exactly. Some smoke was noted to come from the feedline to the turbo bearing housing, and I might need to check the bolts for tightness.
In the meantime, Aad and I worked on using PVC pipe to make a snorkel to the RH front engine air scoop, to catch RAM Air to feed the turbo compressor. We had cut the PVC pipe to length the day before, and with some elbows aligned it towards the compressor inlet. At home, I cut the pipes lengthwise and glued the fittings together.
Now it was time to add some ducktape on the inside before we laid some fiberglass, so the mold would let go once it hardened out. We cut a layer of Fiberglass and cut it in half and with a generous amount of epoxy laid it in the mold, to copy the shape. I let it dry overnight, and this morning went back to remove it from the molds.
Both halves came out perfectly, and so I taped them together with two strips of ducktape, and used to pieces of fiberglass to fasten the halves together. My epoxy exothermed before I could put another fiberglass piece over the inlet area, but I decided to let it all dry for a few days before continuing making it one piece.
Sofar the piece looks like a good fit, and I will have to make another scoop to fit over the turbo compressor inlet bracket to make a sturdy leak free system. It might take all next week before I have it all finished and can perform another TestFlight.
Today would be filled flight. Another look at the turbo, together with stability tests, as part of the EAA Test cards. After that I climbed to altitude to see where max altitude would be in this configuration.
First, I got fuel.. 30 gallons in the left, 25 in the right tank.. that matched with what I had left in the tanks to get back up to full fuel, 70 gallons total. Startup was nominal, and so was taxi to the runup area. after the runup, I got in line for departure on runway 32.
After my clearance for take off, I lined up hit the turbo switch to ON, and departed with 29.7”MP and 2670rpm. Still a little low, but the reset helped it 40rpm higher. Still oscillations on the MP, but climb out was 800ft/min.
Flying to the east, I climbed to 5500ft MSL, as per the EAA test cards, 5000 ft AGL. I had planned to perform a couple of stability check test cards. I started out with Pitch stability. The plane performed as expected, and tried roll stability, push and pull sequences. All in all, TN worked well. I did notice that the rudders have far more power than the ailerons. Only half rudder is needed to overcome full aileron input. With that, EAA test cards 17, 18 and 19 were completed.
After that I stabilized the plane and found engine data points for 5500ft MSL then I climbed in steps to eventually 10,500 ft MSL.clearly the turbo did not help much, as I ended up with 22”MP up there, and I had to make a intermediate stop at 10,400 ft as I was almost at stall speed. Buffet was felt but we still kept climbing , until I sped up before climbing the last 100 ft.
I also leaned the mixture, to get more data points for endurance. In the second half of the flight I descended in stages to get more data points at different altitudes.
I then set up for a LPV approach on runway 32 into Smyrna. Good practice and the autopilot was well in control of the glide path down to 50 ft AGL. It made me comfortable for when I have to operate in IMC conditions.
After taxi in and shutdown, I noted the fuel was approximately 7,5 gallons on the Left tank and 6 gallons in the right tank, which should be about 45 minutes of flying, IFR reserves. The plane handled well at that weight and CG.
With 3,5 hrs flown, and 18 minutes on the ground taxiing, we handled 486 nautical miles. The average speed was 135 knots true. At this time, without Turbo, climbing to between 4K-8k, delivers the best performance.
I was afterwards also convinced that the Turbo was not working at all, in flight. The difference in setup when the engine was used as a tractor, versus the pusher now, made me lose the RAM Air scoop for both the engine as well as the turbo inlet. The engine doesn’t seem to be hindered as much, but the Turbo seems to need the RAM Air in order to operate. So I will build a scoop to recover the RAM Air, for the turbo alone initially. If I need to add another scoop for the engine breathing, I can do that later.
After collecting lots of data, and a turbo problem still present, it was time to really look at the graphs that I have been producing with the help of http://www.flightdata.com, a free graphing service. All my flight data can be found here at https://www.flightdata.com/flights/N405PS/?hr=1
I need to figure out what really makes the turbo oscillate. The top side of the Manifold Pressure suggests that the turbo is working, but somehow it drops off but then quickly recovers again, then builds pressure again and cycles like that. What makes it do that? Is it the controller? Is it the waste gate? Or is it something I have not added which was build into the original Piper Aztec setup, namely RAM Air Recovery? What about the connection with the Propeller RPM? What about Pitch control?
So I took the last data from Flight Test 19, sofar the best setup mechanically now I have adjusted the Pitch trim a bit. I have broken the data into a few areas, so you can easily follow what I am looking at.
The first part of the graph is from right after take off, during climb.I have drawn a few lines and numbered them. The line colors are found on the right next to the graph. We will be looking at the correlation between Manifold Pressure (MP) in Blue, Engine RPM in Red, and Altitude in Green/Yellow (indicated versus GPS)
In the graph above, before line 1, take off power is set. MP is increasing to 29.3” which is above normal pressure, which indicates that the turbo is actually working. The RPM is at 2630, a little lower than nominal, which is 2700.
During the climb clearly the MP is oscillating, and slowly diminishing, as I climb to altitude and static air pressure lowers. This would seem like the turbo is either not working, or is not creating enough pressure to keep up with the climb, or the oscillating MP is getting in the way of holding pressure. As the top end of the turbo MP is still producing good MP, but the average is below what is expected.
At line 2, we start a 120 kias climb from a short level off at speed increase to 140kias, which created some minor pitch oscillations, and some wild MP oscillations. so, is there a connection between the two? We also see that the Mp oscillations are a lot less as we shallow the climb to almost zero, and they become bigger as we increase our Pitch angle. This suggests that there is a connection between pitch and stable MP.
As we get to line 3, we start a constant vertical speed climb. This coincides with a constant medium oscillating MP, which once again directs to a correlation. Once we level off just before line 4, there is another change in MP oscillation. Major ups and downs, which seems to settle.
After line 5, the RPM stabilized, the altitude stable as well, while in smooth air, the MP all of a sudden settles as well. This all suggests that we might have an airflow issue. Although still lower MP than nominal, this is the part of the graph that I like to see all over.
After line 4, the oscillations become all of a sudden very minor. This happens as soon as the Engine is pulled back to 2450 RPM. But the rpm is not stable, and it seems to interact with the MP.
In this next graph, we have a more detailed look at the former graph line 5, now line 1. After the line, the RPM and the Altitude both remain constant, u til at line 2, I pull the power back to 2400RPM. Instantaneously, there is a change showing in the MP. It rises some, but remains fairly steady.
At line 3, I hit an upset in altitude. A few bumps in the sky made for a pitch change, which translated into pretty bad MP oscillations. This once again suggests an air flow issue.
Another look to the third part of the flight. line 1 corresponds with line 2 in the former graph, and line 2 is equal to former graph line 3.
As the altitude upsets continue after line 2, the MP remains unstable, unchanged , until we start a descend at line 3. There is a clear change in oscillations while level, and during descent. The RPM remains the same, and throttle position was not changed. As we descend, the MP rises as expected.
After digesting all this, I have come to a few conclusions. First, there is a clear connection between altitude changes, or pitch changes, with MP changes. Second, the higher the Pitch attitude, the bigger the MP oscillations. Third, lower engine RPM, the lower the oscillations. Fourth, when in smooth flight, with no changes in RPM, the MP is rather constant, albeit lower than expected turbo boosted pressure.
All this made me think about what design changes I had made compared to the original Aztec installation. In that tractor (propeller in front of the engine) setup, the air filter and air supply to both engine and turbo were right behind the propeller, and in a RAM Air Recovery position. In my current setup, both pull air from static airflow, as they are 90 degrees on to the airflow going through the air scoop. Plus, the air is somewhat blocked by the oil cooler and subsequent scoop. This protects the inlets from contaminants entering, but also creates a lot of aerodynamically turbulent air, which could create turbo issues, as well as fuel servo deficiencies.
So, I might have to fix two problems with one solution.. I need to build a RAM Air Recovery scoop that feeds the air from around the oil cooler, and efficiently feed them to the Turbo inlet, and the engine fuel servo inlet. That should give the turbo a smoother laminair flow, and higher start pressure to feed the turbo.
Now, I might be completely off in my thinking. And if you see flaws in my thinking, or have another suggestion or thought about this problem, please contact me. The more of you think with me, the better. or, if you think I am on the right path, I like to hear that as well, to confirm my thesis.
After returning from flight 18, I adjusted the pitch trim as I had noticed that I got a constant “trim down” indication, meaning the pitch servo was asking for help. Some play was noted in the pitch trim and the air pressured the elevator so that it wouldn’t operate in the full range was planned.
I also wanted to see if that changed speeds and also turbo performance as well. With a smoother cruise level off altitude, maybe the air scoop would give more laminair flow to the turbo and thus less oscillation, well that was the theory to be checked.
Take off from runway 32 was nominal, another roll of about 2200 ft before liftoff at 85 knots. Initial climb out at 100kias, with a climb rate of 1100 ft/min.. I was asked to remain below the class C, as I always do, but then traffic crossed my path and I stayed at 1800 ft for a bit until I cleared the traffic anc then climbed at 120 kias, which I asked the autopilot to handle. It did that pretty well, a little constant up/down pitch was noted.
Also noted that the turbo did its usual thing, MP up and down.
At 4500ft MSL, I leveled off and sped up. I kept my eye on the MP and saw no real change as the autopilot had a much easier time keeping the plane level. I kept max MP, 26.5” and used 2450rpm as a setting. That gave me 139kias, with 149ktas with 9C OAT. I boxed the plane around on the cardinal headings, and found the wind pretty steady.
On the north leg, I decided to descent and try to see if the autopilot could handle that now. It did, but as we sped up with no powerchange, the autopilot needed more help pitching the nose down above 135kias.
After the box was complete, I returned to Smyrna airport, but had to set up a long final for other traffic. The straight in approach gave me another chance to try out the V/S descent by autopilot. I did have to pull the power back so it would descent, but it would handle it much better than before.
After some maintenance the past week, it was time for another TestFlight.
Specifically, I wanted to check up on the Turbo as we found the electric switchology problem which made my turbo always turned off. I had already McGyver-ed a switch to turn off the turbo oil bypass valve so the oil would only pass through the controller back to the reservoir, operating the waste gate. We had also checked on the controller as much as I could, and found no real issues. I was then pointed to the filter, which gave a friend of mine some issues in an Aerostar with a similar turbo system. Although the filter is old, it is clear and no real clogging noted. I did order some new ones to replace this one, at a later date. I now have really boiled it down to two points where the oscillations can start, with a third I’d like to investigate last: is the turbo getting enough clean air to boost?
A nice blue sky cool morning, 70F when I reached the airport. I put the cowlings back on, checked the oils and after preflighting and installing my new GoPro 10 camera, I started up with some difficulty, pilot induced .. if you do not follow the checklist, you mighet miss some important steps, like the magneto’s in this case.
I also noted that the fuelpump was weak starting, and that the fuelflow indication was not working. But after the start I noted that all seem to run fine.
Taxiing out to runway 32, the right hand brake seemed a little spongy, another item on the list for next time to check. Runup was completed and nominal, and shortly I was cleared for takeoff, but not before a query from the tower about my cruising speed after departure.. No, I was not just yet able to overtake the preceding Cessna Caravan after departure..
I started the take off without turbo selected, and at max power stabilized, I hit the turbo switch and found a boost of about 1,5 inches Manifold pressure, as expected. At 70 kias, I lifted the nose wheel and shortly thereafter I was airborne. Highest CHT was number 6 cylinder, at 442F.
Acceleration altitude at 1100ft MSL meant speeding to 120knots, but I quickly decided that 100 knots was just fine in these temperatures. I co tinted the climb to 5500 ft MSL, but found a scattered cloud layer and decided to climb above to 7500 ft.
At level off, I accelerated at 24”MP and 2450rpm. Speed was 128kias, 143ktas. I pushed the throttle many times to see if I could find a connection to MP change. I did not find any. The MP oscillations remained throughout the flight. I also checked on pitch attitude oscillations, as the autopilot has a hard time keeping the nose down. I wondered if the air scoop was creating airflow issues for the turbo intake. What I did seem to see was that when I helped keep the nose pitch steady level, the turbo oscillations seemed to get closer to median. But the data will have to prove that.
After some testing eastbound towards Knoxville, I decided to land in Rockwood, just inside my test box on the east side. I abandoned the idea to make a precision landing when I noticed that my seat was not in the perfect position ( I had moved the seat forward to change the CG inflight and see if it would help the autopilot pitch the nose down). I landed about 1500 ft down the runway, and rolled to the end as I couldn’t make the midfield turnoff at 2500 ft.
I taxied back, and reset the plane. The fuelpump still was not quite happy sounding, which we will investigate next time as well.
The take off and turn westward over the hills was done with the turbo on, as the airport is at 1600ft MSL, well above the minimum turbo ON altitude. The power 29”MP and 2630RPM gave me 1100ft/min climb rate, at 98kias.
After clearing the hills, I accelerated and climbed to 6500 ft MSL, above the layer once again, in smooth air. The turbo is not holding MP pressure as I climbed. So, in short, my turbo problem is not resolved.
On the way back to Smyrna, I flew overhead Smithville and decided this was a great area to perform some accelerated stalls..I started with just a normal stall, level flight. It was very hard to stall, but at 61kias, it did loose altitude quickly.
I then started with a 30 degree back turn to the right and tried an accelerated stall. It did stall at 66 kias. Then a left turn and got it to stall once again, and broke once again at 66 kias. After that I climbed back to 6500ft and continued on west. Planning on flying the ILS 32 back in to Smyrna, I setup the navigation. Then found out the .glide path was notam-ed out of service. I continued west to my most sw text box corner, and turned and found my self weaving a way down below a Southwest 737, and above some other GA traffic before setting up for an 8 mile final into MQY, just in front of other inbound traffic. The ADS-B really helped, as I was listening in to Nashville approach.
Landing was on the numbers, easily within 2300 feet. Taxi back and shutdown were nominal and without other squawks then mentioned before.
Some frustration after I shut down the cameras to find out that the new GoPro10 only recorded the first 4 minutes of the flight. The Garmin VIRB360 did record the whole flight so we have footage. It will be added as soon as possible.
To take a little break from all the regular TestFlight I’ve take, sofar, I decided to combine a days flying with a visit to a fly inn situated inside my flighttest box.
As part of remembering 9/11 twenty years ago, Gallatin Music City Executive airport and their EAA chapter arranged a flyin breakfast, and had the Detroit DC-3 on hand for rides, as well as two blackhawk helicopters that flew in from Clarksville.
That morning I was part of a string of aircraft leaving Smyrna for XNX, with empty stomachs. Most were ahead of me in departure. I made the flight in 22 minutes, overtaking one traffic ahead on the way in. I landed and was parked right behind the DC-3. I then met up with a few friends out of Smyrna, to catch up and have breakfast.
After that, I returned to my plane and found some interested folks milling around. From that moment on, I got to speak about my plane a lot. Howard, one of my trusted helpers in the project, came and joined me and helped with answering questions.
A few hours and many young kids in my pilot seats later, it was time to fly back home again. It was my first outing where the focus was less on the testing and more on the fun of flying the Velocity.
Both departures were tried with the turbo switched on. It indeed came alive, as I saw 29.4 and 29.7 inches MP respectively as max. Still meandering though, but after discussing with an A&P friend, we concluded what needs to be done to fix it. But that will be another discussion.
The flight over was short at 3500ft, at 145ktas. The MP kept oscillating throughout the flight. The traffic pattern was flown at 100 kts, to fit in with the other traffic. Touchdown was at 85kts, with a first nosewheel touch at 76 and the last at 69 kts. Rollout was long to the next available taxiway. Brakes were used late, with no fading.
On the flight home, climbout was at 93 kias, a little low, with a 2610rpm. It seems as if the rpm has reset lower in the last flights.
Back at 3500ft, I flew almost straight south until the Class C got in the way, the aimed a bit left. I descended quickly to get underneath the Class C shelf, before aiming for the LH base for runway 19. Touchdown at 89 kts, with nosewheel touch at 70 kias.
During both flights the autopilot kept the plane much more stabil, and easy to control. On the way home, I noted that the ailerons seemed stiffer to control. So all in all, a few items to dive into next maintenance day.
After the maintenance done yesterday, I decided to complete another test to check the turbo operation.
As I added a temporary switch that controls the turbo bypass valve, I wanted to see if I could now see some clear sign the waste gate operates, and the turbo kicks in.
The bypass valve happened to be constantly powered, which opened the bypass, which relieved the oil pressure so that the waste gate would never be hydraulically opened. By adding the switch in the power wire to the bypass valve, I know directly controlled the bypass valve at all times.
The risk involved was that the overboost function would be essentially be blocked, or unless I recognized it and powered the bypass valve by flipping the switch. So, I had to focus a bit more on the manifold Pressure. If it got above 30 inches, I would have to power the bypass valve to relieve the high pressure,
I decided that I would just focus on the turbo this flight, with different switch positions being tested for 5 minutes at a time, with the temporary switch put in the two positions. That left me with 6 different scenarios to test.
I decided to put the switch in the supposed “OFF” position, with the “Turbo ON” lit up, and the “overboost” sign unlit, and the temporary bypass valve switch in the disconnect position. That should give me turbo power on take off., and a quick decision on the take off roll to see if the turbo would overboost on its own.
Startup was nominal, and taxi out went without issues. Runup also was normal, even though the RH mag gave me more irregular running and a big drop of RPM initially, but after leaning the mixture, that cleaned up quickly.
After being cleared for take off runway 01, I lined up, and smoothly added power. The manifold pressure rose to 28.6” initially, and about 7 seconds later, it rose again slowly to 29.7”MP. Clearly the turbo was working now. It then dropped off again and landed on 28.2” MP. It would oscillate like that during the flight. I did pull the power back somewhat when it hit 29.7” as I was afraid it would overboost during the take off roll. Engine power responded with the MP dropping, and then I added full power once again just before I lifted off and got airborne.
I was glad to see the turbo working, even though it was meandering the MP +/-1,5”MP. Not ideal, and will have to be investigated. During climbout, I didn’t notice too much climb issues. A nice 1200 ft/min ascend got me to 1000ft AGL, with all CHT temps staying below 435F.
The secondary climb at 120kts gave a 600ft/min climb. I decided to continue to 4500ft MSL. As I climbed, I noticed that the MP slowly diminished and the meandering would lessen. That was later verified by the graphs from the data my avionics collect.
At altitude, I started my switch combination tests, and just figured out that the turbo switch seems to be wired backwards, and two positions the bypass valve remains powered when it shouldn’t. So, a few electrical switchology problems,
On top of that, the oscillation of the MP is not normal. Reading up in the engine manual later gave me a checklist to confirm and fix this behavior. Two options stood out as possible problems to look at: the controller not working correctly, and the waste gate being blocked or not moving freely and thus responsive.
NOTE : a few days later, I spoke with my A&P for the Cessna, and Harvard, and discussing my test flights and this particular issue, it became clear that I was thinking in the same direction as he. So next maintenance time I will remove the turbo switch from the panel, and double check the electric wiring. I will also pull the waste gate, and clean it and operate it by hand.
But I am glad that the turbo does respond, even if it meanders right now.
I took the cowling off and removed the turbo controller. I tried to open it and see if it was stuck. The air part was not able to be opened. The seals were intact and so I closed that back up.
I then opened the oil valve and checked on dirt etc. Nothing seemed out of order.
After that I decided to build in a test switch so I could manually depower the electric bypass valve. That way I know that the controller is at work. The switch is only in the electric bypass valve circuit, to open or close it. When powered, the valve is open and the controller is bypassed, so the turbo should not operate. But, when we remove power to the bypass valve, the valve closes and now all the oil pressure goes to the controller and operates the waste gate, which should make the turbo kick in.
I temporarily installed two electric leads with a switch in the cockpit connected to one electric lead behind the firewall, to break the power to the bypass valve. I manually control that now.
I did a very short test run, hoping to gather some data. But.. it was inconclusive. Tomorrow I tend to go fly and see if I can make the turbo operate.
If it doesn’t operate, I either have a controller failure, or the waste gate doesn’t close. If it does work, I know I have an electric wiring issue.
After my 3.5 hrs flight 13, I took a break and fueled up at Hollingshead. The ramper pointed out the oil streak coming from the crankcase breather. I took 23.6 gallons in the RH tank and 21.2 in the left tank. That calculated to 12.8 gallons per hour. Not bad.
Flight 14 was going to be another endurance check, with a shorter leg, at a lower altitude, 6500 ft MSL. I planned to also look at the wind vector and IAS/TAS. I had noticed that I always seem to have wind from the right hand side of the plane, even after reversing on the same track.
I got airborne from runway 01, and turned east. I climbed to 6500 ft MSL, and checked the CHT’s. As always number 6 is the highest. OAT on the ground had risen to 22C, but at altitude it was still a nice cool 16C. I ended up with 23”MP at 2350rpm, getting 129 kias, 143 ktas. I know at some point I switched the turbo switch position, which will play a role later on.
One other item that needs a bit of investigation is that my ADS-B IN seems to “hang” at times. The data says it’s still receiving but no changes on the screen happen. Wonder if it is a heat issue, or a data exchange issue.
After I flew east for almost an hour, I reversed course and let the autopilot follow the NAV direct to MQY airport. And yes, the wind which was south, was now from the north, and both about 25 kts.
Comparing with earlier data from Foreflight it should have been calm at 6000 ft. But… checking with XM FIS-B it noted a wind from the north at 25 kts west near Nashville, and winds 150/25 east of my testbox area. That seemed to match my data. I am not quite convinced this is correct. I might plan another magnetic check to verify.
Then I performed a few stall series. Initially the airplane fought me for pitch control. The G3X system has a feature where it will not let you fly too slow, after an “airspeed” vocal warning. You can override by holding the autopilot disconnect button pushed. After trying that, I found that the plane did not want to stall as low as 59 kias. She did start a 700 ft/min descent, and I recovered from that. I abandoned the stalls to read up more on the G3X system before I start accelerated stall series.
10 minutes out, I started my descent and was asked to setup for a RH base for runway 32. Landing was once again nominal, powered pulled at 100 ft and touching on the touchdown blocks. Rollout was well within 3000 ft, and I didn’t really maximize breaking.
Taxi back to my hangar was blocked by another airplane so I had to take my alternate route. More braking was required, and after shutdown I found that the aircraft was hard to move. I blame hot brakes.
After return home, I downloaded all the data and looked at the graphs on flightdata.com. I noticed that the MP was jumpy, as I expected to see. But what caught my eye was that there were three distinct areas of MP operation.
The first was from take off to right after level off at 6500ft, with very erratic quick changes in MP. Then a time where the changes were less frequent, and less peaks and valleys. Then just over halfway the flight, it got back to more erratic and higher peaks/valleys.
Checking against other engine and flight data, there is no change interaction with the two MP changes. The only thing I could have done is operate the turbo switch. I know I did once, but maybe I did twice. The video I took will prove that.
If so, then there is some action in the turbo system responding to the turbo switch, even if it doesn’t give us the requested MP boost to 28.5”. This will be investigated next week when we have more maintenance time.
Then, we will also know the fuel burn on this 2hr trip after we fill up once again.
Right now we are at 17.8 hrs of testflights, I am convinced that 40 hrs is exactly what is needed to give the plane a proper shake out.
Sieders Family Velocity Aircraft 