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 Monday, February 08 2010 @ 08:08 PM EST

Flt 44 Report

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Flight Test

Monday 16 Nov 2009
1.4 air time
1.3 flt time

Inter-flight activities:

  1. Installed missing standby alternator control wire.
  2. Moved fuel flow transducer to be between engine-driven fuel pump and fuel injection servo.

Purpose:

  1. Standby alternator functional test.
  2. Fuel flow indication test.
  3. CHT cylinder-to-cylinder difference check.
  4. Engine restart tests.
  5. Glide performance tests.

Events:

  1. Checked standby alternator performance between 1800 and 2100 rpm.
  2. Checked fuel flow indication stability.
  3. Checked CHT values in climb and cruise.
  4. Conducted engine shutdown and restart tests.
  5. Conducted glide performance tests with prop windmilling and with prop stopped.

Results:

  1. The standby alternator maintains essential bus voltage at 12.9 volts with battery master and alternator OFF, and rpm at 1900 rpm or higher. Bus voltage starts to decrease at 1800 rpm (12.8 volts). All essential bus-powered avionics were ON for this test.
  2. Fuel flow indication is much, much more stable than before.
  3. All four CHTs are now within 30 deg F of each other the vast majority of the time.
  4. The engine restarts instantly once the mixture is moved from OFF to rich, with the throttle cracked open. The indications of engine failure at idle are very, very subtle, as the prop maintains the engine rpm at the selected value, and there is very little change in thrust. The fall in EGTs is the clearest indication of engine failure at idle.
  5. Once the mixture is pulled to OFF, it is extremely difficult to get the prop to stop turning. It persists in windmilling, even as the speed is slowed to the stall with flaps UP. The prop will eventually slow and stop, if flaps are selected to FULL, and the airspeed is held just above the stall for about two minutes. Once the prop was stopped, the airspeed could be increased to about 95 kt before the prop would start turning again.
  6. The glide performance was measured in reciprocal heading descents, with prop windmilling (mixture OFF, prop control full aft, throttle at idle) at 80, 90, 100, 110 and 120 kt.
  7. The glide performance was measured in reciprocal heading descents, with prop stopped (prop control full forward, throttle at full) at 80 kt. The glide ratio was approximately 9.4:1, based on hand-recorded data.
  8. Full glide performance results will be reported later.

New Snags:

  1. None.

Existing Snags:

  1. Max rpm still decreases late in the flight.
  2. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.


4 comments
Most Recent Post: 11/23 09:15PM by Kevin Horton

Glide Performance Testing

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Flight Test

I had a very interesting glide performance test flight late yesterday afternoon.

Eventually, I plan to use the RV-8 for quite a few trips back to Yarmouth, NS, to visit my parents and sister. Yarmouth is on the western tip of Nova Scotia, and you have a choice of flying over the Bay of Fundy, or going quite a bit further east to stay over land. The "over land" route adds an hour to the trip, so I am very interested in the Bay of Fundy route.

The Bay of Fundy is 24 nm wide if you cross from Grand Manan Island to Digby Neck. I want to know how high I need to be to ensure that I could get to land if the engine failed in the middle of the crossing.

I had assumed that it would be relatively easy to get the engine to stop turning after it was shut down, by reducing the airspeed. I planned to conduct a series of glide tests with the engine stopped at various airspeeds. I would then repeat with prop windmilling near best glide speed, and do another one with the engine running at idle, to see the differences.

After getting airborne yesterday, I did a couple of practice forced landings with the engine at idle, just in case. Then I climbed to 8000 ft, slowly pulled the power to idle, then pulled the mixture to OFF. The prop continued to windmill. I trialed the restart procedure (throttle just above idle, and smoothly push the mixture to RICH). The engine started immediately, as evidenced by the EGTs increasing. I shut it down again, and slowed to the stall, intending to do another restart test using the starter. The prop continued to windmill, even at the stall. I quickly amended the plan of the day to do all glide tests with prop windmilling.

I did two runs at each speed, one at 030 heading, and one at 210 heading (the forcast wind was 300, i.e. at 90 degrees to these headings). I flew test points at 80, 90, 100, 110 and 120 kt), timing the decent from 8000 ft to 7000 ft.

I was still wondering whether it was possible to get the prop to stop, so I climbed to 10,000 ft, pulled the mixture OFF, pushed the throttle to MAX (to increase the torque required to spin the engine), put the flaps fully DOWN, and slowed to just above the stall. The rpm very slowly decreased, and the engine finally stopped about 2 minutes after shutdown. I increased the airspeed, retracted the flaps, and did a glide test at 80 kt from 7300 ft to 6300 ft, then used the starter to restart the engine. I climbed back up and repeated on the reciprocal heading. After this one I very slowly increased the speed, and found that the engine would start spinning again at about 95 kt.

I cleverly left my log card with all the times, fuel quantities, etc in the aircraft, but I do have all the data I recorded on the laptop. But analyzing that data will be more work than expected, as I neglected to put the EFIS altimeter to 29.92.

The original Dynon EFIS software sent barometric altitude in every record, so if you forgot to set 29.92 you simply had a correction to make to the altitude on every record. But they eventually changed the software to alternate between pressure altitude and barometric altitude - one record has pressure altitude, and the next one has barometric altitude. They set a bit at the end of the record to indicate which type of altitude is contained in that record. But, I never updated my data recording script to check that bit, so it simply records every altitude, no matter what kind it is. So if I plot the altitude from this flight, I see that it jig zags up and down. I know what the altimeter setting was - now I need to write a script to correct every other record so I have a clear set of data to analyze.

I did a very quick "back of the envelope" calculation, using the raw data that I recall for 80 kt with prop stopped, and 90 kt with prop windmilling. The glide ratio was about 9.4:1 at 80 kt with prop stopped. It would be slightly better at 90 kt, but there would be a significant risk that the prop would start spinning. The glide ratio at 90 kt with prop windmilling, prop control full aft and throttle at idle was about 8.2:1. These intial estimates will be updated once the full data analysis has been completed.

Lessons learned - Don't count on getting the prop to stop if the engine fails. While it may be possible to get it to stop if the airspeed is kept just above the stall with full flap for two minutes, this yields a steeper glide during those two minutes, and thus it is unlikely that this lost altitude will ever be recovered, even with the slight improvement in glide performance that would occur if the prop could be stopped.

If the prop has stopped on an undamaged engine (engine stoppage due to fuel exhaustion, etc), care should be taken to not increase the airspeed above 90 kt, or the prop may start turning again.

I'll need to be at least 9,500 ft to be able to make land from any point in the crossing of the Bay of Fundy. I can go as high as 13,000 ft for 30 minutes without oxygen, so I'll plan to go to at least 11,000 ft to have some margin for winds, etc.


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Flight 37 Report

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Flight Test

Monday 12 Oct 2009
0.5 air time
0.6 flt time

Inter-flight activities:

  1. Extended under-cylinder head wrap around baffle on bottom of #1 cylinder, in an attempt to raise the CHT.
  2. Tightened inverted oil lines to hopefully resolve two oil leaks.
  3. Removed one link in tailwheel chain
  4. Connected wing leveler pushrod to flight controls.
  5. Conducted wing leveler ground test procedure and adjustments.

Purpose:

  1. Navaid Devices wing leveler flight test

Events:

  1. Checked wing leveler performance at low and cruise speed in wing leveler mode.
  2. Checked wing leveler performance at cruise speed in GPS track mode, with GPS in enroute sensitivity.
  3. Checked wing leveler performance at cruise speed in VOR track mode.
  4. Checked wing leveler performance at cruise speed in GPS track mode, with GPS in terminal sensitivity.
  5. Checked wing leveler performance at intermediate and final approach speed in GPS track mode, with GPS in LPV angular sensitivity.

Results:

  1. Wing leveler works well in both wing leveler and track modes. Turns in wing leveler mode are smooth. GPS and VOR tracks are followed within about 1/10 deflection of the CDI needle, without control stick oscillations. No adjustments needed. Need to test in turbulence.
  2. The use of the wing leveler promises to greatly reduce the workload during cross country flights. The wing leveler appears to do a better job than a pilot of tracking the lateral navigation signal. The aircraft is quite stable in pitch once it is trimmed, so the workload to hold the desired altitude is quite low in smooth air. Testing will be conducted in turbulent air.
  3. #1 CHT is still significantly lower than the others. The reduction of the under-cylinder baffle gap caused a very small increase in the difference between the hottest and coldest CHTs.

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. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.
  4. #1 CHT is about 50 deg F lower than the others. Probably should recheck the CHT probe calibration in boiling water as the next step.


3 comments
Most Recent Post: 10/14 01:27PM by flyeyes

Flight 36 Report

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Flight Test

Thursday 08 Oct 2009
0.7 air time
0.8 flt time

Inter-flight activities:

  1. Semi-permanently installed rudder trim tab using 3M double-sided tape.

Purpose:

  1. Cruise performance testing at 8000 ft

Events:

  1. Cruise performance test at 2400 rpm, wide open throttle (WOT), 50 deg F lean of peak EGT (LOP).
  2. Cruise performance test at 2600 rpm, WOT, 100 deg F rich of peak EGT (ROP).
  3. Cruise performance test at 2150 rpm, WOT, 50 deg F LOP.

Results:

  1. Pending data analysis

New Snags:

  1. The ball is now very, very slightly to the left at the typical cruise condition. While it was perfect when the trim tab was taped in place with the wedge flush against the rudder skin, the double-sided tape that now holds it in place is about 0.06" thick. This puts the tab out slightly more into the airflow, and apparently increases its effectiveness. The tab must be trimmed slightly.

Existing Snags:

  1. Max rpm still decreases late in the flight.
  2. SD-8 Alternator - must run power wire to regulator.
  3. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.


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Flight 35 Report

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Flight Test

Thursday 08 Oct 2009
0.4 air time
0.4 flt time

Inter-flight activities:

#. Temporarily installed rudder trim wedge using metal tape.

Purpose:

  1. Rudder trim check

Events:

  1. Checked rudder trim at the expected typical cruise condition of 2400 rpm, wide open throttle, 50 deg F lean of peak EGT.

Results:

  1. All three balls (EFIS, turn and bank, and wing leveler) were centred.

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. Pitch trim speed of movement is slow during a touch and go. Need to try it with the pitch trim speed governor removed.


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Flight 33 Report

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Flight Test

Saturday 25 Sept 2009
1.3 air time
1.4 flt time

Official flight test phase now complete!. Just need to visit the local Transport Canada regional office to get the new paperwork - hopefully on Monday.

Inter-flight activities:

  1. Removed all the ballast.
  2. Installed the rear seat riser under the rear seat cushions.

Purpose:

  1. Cruise performance (but, the air wasn't smooth enough, so the alternate test plan of cloud chasing was conducted)

Events:

  1. Cloud chasing.

Results:

  1. All clouds chased from the local area.

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.


2 comments
Most Recent Post: 09/28 03:26PM by psychose

Flight 32 Report

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Flight Test

Saturday 25 Sept 2009
1.5 air time
1.6 flt time
1.1 hrs to go to finish the official flight test phase

Inter-flight activities:

  1. Reinstall rubber sealing strip at left wing root fairing. Added pieces of duct tape on the bottom in an attempt to hold it in place.
  2. Checked elevator trim tab position. It had been left in the position required for trim at VNE with aerobatic aft CG from the previous flight. The plan was to adjust the elevator trim tab travel so this angle was achieved at the nose down limit, thus potentially allowing increased travel in the nose up direction. But, it was found that the tab was only a fraction of a degree from the stop, so there was little to be gained by an adjustment.

Purpose:

  1. Stability and control tests at aerobatic aft CG.

Events:

  1. Static longitudinal stability tests at idle and high power, at low and high speeds, with flaps UP, 1/3 and DOWN.
  2. Static lateral and directional tests at idle and high power, at low speed, with flaps UP, 1/3 and DOWN.
  3. Stick force per g tests at VA and VH.
  4. Two landings with 8 to 10 kt crosswind.

Results:

  1. Stick free static longitudinal stability is positive at high speed, at idle and high power.
  2. Stick free static longitudinal stability is weakly positive at low speed at idle power.
  3. Stick free static longitudinal stability is negative at low speed at high power. If the aircraft is trimmed at Vy with flaps up, 1.2 Vs with 1/3 flap, or 1.3 Vs with full flap, and the speed is reduced, a push force is required to stabilize at any lower speed. If the stick is released, the aircraft will decelerate to the stall. While there is little risk of stalling with max power if flying in VMC conditions, pilots flying at aft CG in IMC conditions should be aware of this adverse characteristic.
  4. Strong buffet with full left rudder sideslip with full flap at 1.3 Vs. The horizontal stabilizer tips move up and down several inches. Fortunately, there is so much discing drag at idle this prop that there should be no need for full rudder sideslips.
  5. A strong nose down pitching moment is seen at full rudder with 1/3 flap at 1.2 Vs with max power, likely indicating that the downwind side of the horizontal stabilizer is affected by disturbed airflow from the vertical stabilizer or aft fuselage.
  6. Stick force per g is on the order of three pounds per g.
  7. Static directional stability is strongly positive under all conditions.
  8. Static lateral stability is positive under all conditions tested.

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.


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Flight 31 Report

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Flight Test

Friday 25 Sept 2009
2.4 air time
2.5 flt time
2.6 hrs to go to finish the official flight test phase

Inter-flight activities:

  1. Added more ballast to the passenger seat to bring the CG to 85.1" aft of the datum. The CG moved further af to the aerobatic aft CG limit (85.3") as fuel was burned. Weight at engine start was 1803 lb, the highest weight that has been flown to date.

Purpose:

  1. Stalls and one turn spins at aerobatic aft CG.
  2. AWM 549.111 climb performance test (amateur-built aircraft in Canada must demonstrate the ability to climb 1000 ft in 3 minutes, at max take-off weight, corrected to sea level, standard day conditions).

Events:

  1. Wings level, turning and accelerated stalls at idle and max power for each flap position.
  2. One turn spins in each direction with flaps up (six turn spins with flaps up will be done later, as part of the aerobatic evaluation). The planned one turn spins with flaps extended were cancelled due to the significant risk of flap overspeed, and the likelihood that any in-service spins with flaps extended would likely occur at too low an altitude to allow a recovery.
  3. Trimmed at VNE, then landed without retrimming. The trim angle will be measured, and the pitch trim will be adjusted to achieve this angle at full nose down travel. Reducing the nose down trim travel will increase the nose up trim travel, which will reduce the stick forces during final approach at forward CG.
  4. Recorded full throttle MP vs IAS at 7500 ft.

Results:

  1. Stick free longitudinal static stability is still positive at idle power, but is noticeably negative at low speed at maximum power at all flap settings. If the aircraft is trimmed at 80 kt at full power, forward stick force is required as the speed is reduced without changing the power. If the speed is reduced from the trim speed, and the stick is released, the speed continues to reduce until the aircraft stalls. Positive forward stick pressure is required to recover from the stall.
  2. Stick force during approach and landing with trim at the position for VNE was less than 5 lb.
  3. Post-flight analysis suggests that the induction system is achieving about 2/3 of the theoretical maximum amount of ram air pressure recovery, which is surprisingly high.

New Snags:

  1. Rubber sealing strip between the left wing intersection fairing and the fuselage came loose, again. Tape will be used on the bottom of the intersection fairing to attempt to hold the sealing strip in position, without resorting to the glue that will be used once the aircraft has been painted..

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.


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Flight 30 Report

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Flight Test

Thursday 24 Sept 2009
1.6 air time
1.7 flt time
5.0 hrs to go to finish the official flight test phase

Inter-flight activities:

  1. Added ballast to the passenger seat to bring the CG to 84.3" aft of the datum. Weight at engine start was 1757 lb, the highest weight that has been flown to date.

Purpose:

Qualitative handling assessment at aft CG.

Events:

  1. Slow flight
  2. Longitudinal static stability
  3. Trim at VNE
  4. Stalls
  5. Three touch and goes and a full stop landing.

Results:

  1. Rudder pedal forces required to turn the tailwheel are much higher than at more forward CGs.
  2. Stick forces noticeably lighter as the CG is moved aft.
  3. Longitudinal static stability is still positive, but is much weaker than at forward CG.
  4. Still able to trim at VNE.
  5. Now able to trim at final approach speed at idle (cannot trim in this condition at mid or forward CG)

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.


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Flight 29 Report

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Flight Test

Wednesday 23 Sept 2009
0.7 air time
0.8 flt time
6.6 hrs to go to finish the official flight test phase

Inter-flight activities:

  1. Troubleshoot data recording snag. It turned out to be an error I had made while making an "improvement" to my data recording program.
  2. Added more ballast in the aft baggage compartment to bring the CG to 83.5" aft of the datum. Weight at engine start was 1717 lb, the highest weight that has been flown to date.

Purpose:

Qualitative handling assessment at aft CG.

Events:

  1. Slow flight
  2. Longitudinal static stability
  3. Trim at VNE
  4. Stalls
  5. Three touch and goes and a full stop landing.

Results:

  1. Much greater forward stick force required to lift the tail in the early part of the take-off run.
  2. Stick forces noticeably lighter as the CG is moved aft.
  3. Longitudinal static stability is still positive, but is much weaker than at forward CG.
  4. Still able to trim at VNE.
  5. Now able to trim at final approach speed at idle (cannot trim in this condition at mid or forward CG)

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.


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