Details
Hits: 2923
Sunday 20 Sept 2009
0.6 air time
0.6 flt time

Inter-flight activities:

  1. None.

Purpose:

Handling tests at mid CG. 75 lb of ballast was well secured in the aft baggage compartment to bring the CG to 82.34" aft of the datum at engine start.

Events:

  1. Static longitudinal stability tests with one-third flap and zero flap at low speed.
  2. Static lateral and directional stability tests with one third flap at low speed.

Results:

  1. The flight was cut short due a buzzing sound that started after one of the early test points. After landing, it was noted that the left wing intersection fairing rubber seal had come loose in a small area near the leading edge.
  2. An interesting event occurred while doing a right wing down, full rudder, steady heading sideslip test with the fuel supplied by the right fuel tank. The sideslip was sustained for longer than previous tests, with 30 degrees of bank required to hold heading - then suddenly the engine stopped, apparently due to fuel starvation - it was very quiet for a few seconds. The engine restarted immediately when the fuel was changed to the other tank. The fuel was left on the left tank for the remainder of the flight so it could be seen how much fuel it took to refill the right tank after landing. Only 4.6 USG of fuel was required to fill that tank. It is hard to fathom how a fuel pickup could unport on a tank that was almost 80% full but I can't come up with any other possible cause of the momentary engine stoppage.

Lessons of the day:#. Do all tests at a safe altitude, to allow recovery from unexpected events.#. Select fuel to high wing prior to sustained sideslips.

New Snags:

  1. Left wing intersection fairing rubber strip has come loose three times. It was planned to use glue to secure the rubber seal to the intersection fairing after the aircraft had been painted. Perhaps it will be necessary to do this now.

Existing Snags:

  1. Max rpm still decreases late in the flight.
  2. SD-8 Alternator - must run power wire to regulator.
  3. Small amount of right rudder pedal force needed in cruise. Need to add a wedge on the left side of the rudder trailing edge.
  4. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.

Details
Hits: 2580
Sunday 20 Sept 2009
1.0 air time
1.1 flt time

Inter-flight activities:

  1. None.

Purpose:

Stall and one turn spin testing at mid CG. 75 lb of ballast was well secured in the aft baggage compartment to bring the CG to 82.34" aft of the datum at engine start.

Events:

  1. Wings level, turning and accelerated stalls at idle and max power for each flap position.
  2. One turn spins at each flap position (six turn spins with flaps up will be done later, as part of the aerobatic evaluation).

Results:

  1. Spins - There is not enough up elevator authority to hold the aircraft in a spin, even at mid CG. The angle and attack and rotation rate are oscillatory, and the airspeed continually increases, indicating the aircraft has transitioned to a full aft stick spiral dive. After seeing the same result in both left and right spins, the right spin was repeated with a longer duration, to see if perhaps the airspeed indication was erroneous, and the aircraft was really in a spin. The spin rate increased, and as the IAS hit about 90 kt, there was a very violent flick to the right, like a snap roll - perhaps the right wing stalled during one of the angle of attack oscillations.

The planned one-third and full flap test points were not attempted.

The up elevator travel will be checked, to confirm that the proper up travel is being achieved.

New Snags:

  1. None

Existing Snags:

  1. Max rpm still decreases late in the flight.
  2. SD-8 Alternator - must run power wire to regulator.
  3. Small amount of right rudder pedal force needed in cruise. Need to add a wedge on the left side of the rudder trailing edge.
  4. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.

Details
Hits: 2605
Saturday 19 Sept 2009
1.0 air time
1.1 flt time
9.1 hrs to go to finish the official flight test phase

Inter-flight activities:

  1. None.

Purpose:

This had originally been planned as the second handling test flight, at mid CG. However, the intrepid test pilot was tired after the morning flight at forward CG, and decided to push the mid CG flight to the next day. This flight was used to conduct cruise power experimentation, and to practice landings. 80% of the landings are quite acceptable. 20% are hopefully not on anyone's video camera, as I'm not happy with the small skips and hops.

Events:

  1. Cruise speed vs fuel flow. The air was smoother than the last test, and the results seemed a few knots faster.

Preliminary Results:

  1. It looks like the typical cruise condition will be 2400 rpm, full throttle, leaned to 50 deg F lean of peak EGT. This looks like it produces 160 to 165 kt TAS at 8.0 US GPH at 8000 ft.
  2. 2500 rpm, full throttle, leaned to 100 deg F rich of peak yields about 178 kt TAS at about 11.5 US GPH. That is a lot of extra fuel to burn to get 15 more knots.

New Snags:

  1. None

Existing Snags:

  1. Max rpm still decreases late in the flight. Need to take another look at the prop control cable.
  2. SD-8 Alternator - must run power wire to regulator.
  3. Small amount of right rudder pedal force needed in cruise. Need to add a wedge on the left side of the rudder trailing edge.
  4. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.

Details
Hits: 3137
Saturday 19 Sept 2009
1.5 air time
1.5 flt time

Inter-flight activities:

  1. Chased down source of rattling noise heard during approach and landing on the previous flight. The rubber sealing strip at the left wing root fairing had come loose in a short section about 18 inches aft of the leading edge.
  2. Adjusted max rpm stop on the prop governor 1/3 turn.
  3. Traced standby alternator wiring. Found that the wire that supplies power from the control relay to the regulator had never been installed. Must obtain a suitable ring terminal, and then install the missing wire.

Purpose:

First in a planned series of flights to investigate aircraft handling at various CG positions. An exhaustive series of handling tests will be conducted at forward CG, mid CG, aerobatic aft CG and full aft CG. The tests include:

  1. Static longitudinal stability at all flap positions, with power at idle and max power, at low and high speed for each flap setting.
  2. Stick force per g at VH and VA.
  3. Static lateral and directional stability tests at all flap positions at idle and max power at low and high speed for each flap setting.
  4. Dynamic lateral and directional stability tests at all flap positions (aft CG flights only).
  5. Wings level, turning and accelerated stalls at idle and max power for each flap position.
  6. One turn spins at each flap position (six turn spins with flaps up will be done later, as part of the aerobatic evaluation).

This flight was at the most forward CG that will be seen in service - pilot, with no passenger or baggage. The CG was 79.79" aft of the datum. Van's recommended forward limit is 78.7", but there is no practical need for the CG to be that far forward on this example of the RV-8, so there is no point in testing there. If a passenger is carried, the CG is sure to be further aft. If a solo flight is flown with baggage, the baggage will be loaded in the aft baggage compartment. The forward baggage compartment will only be used if a passenger is carried.

Events:

  1. Static longitudinal stability at all flap positions, with power at idle and max power, at low and high speed for each flap setting.
  2. Static lateral and directional stability tests at all flap positions at idle and max power at low and high speed for each flap setting.
  3. Dynamic lateral and directional stability tests at all flap positions (aft CG flights only).
  4. Wings level, turning and accelerated stalls at idle and max power for each flap position.
  5. One turn spins at each flap position (six turn spins with flaps up will be done later, as part of the aerobatic evaluation).

Results:

  1. Engine speed for take-off was 2690 rpm - just about perfect. It came down to 2650 after the engine warmed up, but was found to have decreased to 2550 later in the flight. More investigation needed.
  2. Static longitudinal stability is fairly strong at all conditions (forward CG flight).
  3. Stick force was estimated at 10 lb per g up to 3 g.
  4. Static directional stability is strong at all conditions.
  5. Static lateral stability is weak at high speed conditions - i.e. there is very little roll response to sideslip, making it difficult to pick up a wing with rudder.
  6. Stall characteristics are excellent, with very little wing drop. Stall warning is marginal, with light buffet felt about 3 kt prior to the stall. There is not enough up elevator authority to fully stall the aircraft with idle power and flaps up or with one third flap.
  7. Spin - There is not enough up elevator authority to hold the aircraft in a spin. The angle and attack and rotation rate are oscillatory, and the airspeed continually increases, indicating the aircraft has transitioned to a full aft stick spiral dive. The one-third flap test point was aborted very quickly to prevent a flap overspeed. The full flap test point was not attempted.

New Snags:

  1. None

Existing Snags:

  1. Max rpm still decreases late in the flight.
  2. SD-8 Alternator - must run power wire to regulator.
  3. Small amount of right rudder pedal force needed in cruise. Need to add a wedge on the left side of the rudder trailing edge.
  4. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.

Details
Hits: 4991

I noted a long time ago that my 8 amp B&C Specialty Products SD-8 standby alternator wasn’t working. But, every time I wen to the hangar, I’ve either had more important snags to chase, or the weather was good and I went flying. This afternoon, the wind was howling straight across the runway, and I wasn’t too motivated at work, so I went to the hangar to finally attack this snag.

First, I compared the wiring diagram in the B&C installation drawings against my wiring diagram - they matched perfectly. Then I crawled under the instrument panel with a voltmeter to check my wiring. I found that there was no power at the voltage regulator. Tracing the wiring, I found that for some stupid reason I hadn’t fully finished installing all the wiring for the alternator control. I had not installed the wire that went between the control relay and the noise filter capacitor.

Now that I know what the problem is, I need to find the best way to run a 12 AWG wire from the control relay, behind the right side of the instrument panel, and the capacitor way over on the left side, on the front of the landing gear box. I’ll attack this fix in the near future, once I acquire anther 12 AWG ring terminal - the lack of one of these is perhaps why I never finished the job in the first place.

Details
Hits: 4859

This post documents a “gotcha” - hopefully some other folks will find this and avoid having to spend as much time troubleshooting as I did.

When installing my new Aero Technologies PCU-5000X propeller governor, I found that the governor control arm travel was large enough such that the prop control in the cockpit tended to hit one of its stops before the governor control arm hit its stop at the governor. I finally managed to get things adjusted so the governor arm would hit both the high and low rpm stops just before the prop control in the cockpit hit its stops. But there wasn’t much margin between the cockpit control and its stops.

When I got the aircraft flying, I noted that as the engine warmed up, the maximum selectable rpm would drop by more than 100 rpm. I pulled the cowlings, and confirmed that the governor control arm was hitting its max rpm stop before the cockpit control hit its stop. I discussed the problem with Aero Technologies, and they suggested that perhaps there was an internal oil leak between the governor and the prop. As the oil warmed up, the viscosity would decrease, and more oil would leak, which could impair the ability of the governor to control the prop. I’ve got an aerobatic prop, which defaults to coarse pitch (low rpm), and the governor sends oil pressure to the prop to force it to low pitch (high rpm). Thus an oil leak in the prop control path could cause the rpm to be lower than selected.

I used the procedure in Lycoming Service Instruction 1462A to confirm the oil leakage at the front of the engine was acceptable, but I couldn’t check the oil leakage at the back of the engine without pulling the prop governor. The access to the governor is poor, as it is on the back of the engine, surrounded by hoses, wire bundles, etc. So I put that task off while I did more thinking.

One day, in flight, I did some more experimenting. I recorded the max selectable rpm and the oil temperatures as the engine warmed up. Then, later in the flight, I fully opened the oil cooler door, and cooled the oil down, then checked the max rpm again. I found that the max rpm was lower than it had been earlier in the flight at the same oil temperature. There had to be another variable. Hmm.

I then hypothesized that perhaps the problem was due to differences between the coefficient of thermal expansion of the prop control cable and that of its sheaf. If the external sheaf expands more than the steel control cable, that would tend to reduce the travel of the cable end, and the cockpit control could then hit its stop before the control arm hit the stop at the governor. As a test, I adjusted the cable at the governor bracket to give more margin to the stop at the cockpit control when the governor control was at the max rpm stop. This meant that the low rpm stop could no longer be reached, as the cockpit control would hit its stop first. But, the low rpm stop is much less important than the high rpm stop.

On the next flight, I found that now the rpm only decreased 40 to 50 rpm as the engine warmed up. This is in the range reported by another local pilot who has three Pitts Specials with MT aerobatic props, so I think I have solved my problem.

Lesson Learned - Be sure to leave adequate clearance between the cockpit controls and the full throttle and max rpm stops. Otherwise you might be sacrificing some throttle or prop control travel after things warm up.