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I was at the hangar pretty much all day on Saturday, and Sunday morning. The engine installation is like an onion, with many layers. It is hard to get at some things in the inner layers unless the stuff in the outer layers are removed first. I got almost everything removed from the engine, working from the outside in, carefully writing down the order that I removed things, and putting the hardware for each step in storage containers with multiple compartments. I should hopefully be able to follow my notes to reverse the steps, and avoid the risk of getting all the layers of the onion reinstalled, only to find an inner layer item that I forgot to install.

Mark Richardson grabbed an engine crate that was in a hangar at Carp, and delivered it to the hangar on Saturday AM. Thanks Mark.

I hope to borrow an engine hoist on Tuesday or Wednesday and pull the engine and put it in the crate.

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Another RV guy contacted me this morning to tell me that a friend recently had a large overspeed on his RV He said that his friend found that the rpm in his event was high enough that Hartzell said the prop had to be scrapped, rather than inspected and returned to service.

I sent an e-mail to Hartzell tech support asking them about this, and got an answer this afternoon. For short duration events (20 seconds or less), the official info in the Special Inspections sectionj of Hartzell's Standard Practices Manual says:

  1. overspeed of 100% to 110% - no action required
  2. overspeed of 110% to 115% - inspect prop and return to service
  3. overspeed of 115% to 120% - overhaul prop and return to service
  4. overspeed of greater than 120% - scrap the prop

The recommendation to scrap the prop at 120% overspeed or higher is partially due to the centrifugal loads, and partially due to the potential for much higher harmonic vibration loads at rpms above the normal rpm limit.

My overspeed was about 148%. The loads at that speed would be more than twice the normal loads, which made me nervous about continuing to use this prop, even if it had been inspected. Hartzell's official inspection info pretty much makes the decision for me. I'll scrap the prop and buy a new one. Maybe I can sell it to the airboat guys.

This is getting more expensive by the day. To put salt in the wound, the Canadian dollar to US dollar exchange rates are moving in the wrong direction, and very quickly. Not too many months ago, the two dollars were pretty much equal in value. Now the Canadian dollar is worth less than 0.80 US dollar.

Terry, bless her heart, has been extraordinarilly understanding. She offered to work an extra day per week for the next few months, and she will use more restraint when shopping. I was in the habit of taking overtime as banked time off - I'll start taking it as cash for awhile.

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I spoke with Bart Lalonde at Aerosport Power on Monday - he agreed with me that the engine should be opened up and inspected. He will magnaflux the significant components, and replace the connecting rod bolts and crank counterweight bushings. I was happy with the ballpark price that he quoted. Obviously the cost will go up if he finds other components that need replacing.

As far as the root cause of the event goes, Bart is familiar with other events where angle-valve IO-360s with Christen inverted oil systems. The angle-valve IO-360s have very long, flat, oil sumps, and the oil moves towards the front in steep descents. The Christen oil pickup is at the back of the sump. He suggested I replace my current oil pickup with one made by Raven Aircraft. They apparently make one that is longer, which puts the pickup more towards the middle of the oil sump. I may also add an accumulator in the oil system. And, I’ll experiment with running more oil in the sump. I had 8.5 quarts in the whole system, but I don’t know how much of that was in the sump.

Another local RV guy has offered me engine and prop crates. I’ll remove the prop this weekend, and start pulling all the stuff off the engine. If things go very smoothly, I might be able to get the engine in the crate by Sunday night. If not, I should be able to finish it up by next weekend.

I’m still working on the plan for the prop. It certainly will not fly again without an inspection by a qualified prop shop. I may replace it with an "aerobatic" prop, that moves towards the coarse position if oil pressure is lost. That would lead to an engine underspeed, which is a lot nicer than an overspeed. I'm communicating with Hartzell and MT to get the details on their respective offerings.

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This has been an expensive day. I had flown a climb performance test yesterday, and another airspeed calibration test this morning. Everything was going well, and I was hoping to get to the 25 hour point by the end of next weekend, weather permitting. This afternoon I strapped 75 lb ballast down in the aft baggage compartment to move the CG back to the middle of the envelope, and took off to fly a series of tests that I will repeat at successively more aft CGs as I work back to the aft limit.

Many of the points in my test program are pulled from the FAR 23 requirements for single-engine aircraft - they are the same tests that would be done during the type certification flight testing on a production aircraft. I added the FAR 23 test points as I was curious how the aircraft matched up.

One of the tests on the card was a pitch trim check with idle power at VNE, as called for in FAR 23.161(c)(3). I didn’t expect that there was any risk associated with this test, so I didn’t do any sort of build up test points. I pushed over to VNE, then smoothly brought the throttle towards idle. As I got back to about one-third throttle all hell broke loose. The rpm ran away, increasing rapidly through 3500 rpm. My instinctive reaction was to undo the last action I had just taken, so I pushed the throttle forward a bit. The rpm continued to increase, and I saw over 3800 rpm before it decreased back into the normal range.

I stopped the testing, and headed back towards Smiths Falls. The engine showed no signs of distress, but it was clear that the smart thing to do was to land ASAP. I looked at the recorded data, and it shows that shortly after I brought the throttle back the oil pressure started to drop sharply, indicating as low as 22 psi (but, there is almost certainly some air in the line from the engine to the oil pressure transducer, which would dampen the oil pressure indication, so the actual pressure may have been lower), and obviously the prop governor stopped getting the oil it needed to control the prop. The prop will go to low pitch if the oil supply stops, and low pitch and a bit of power at VNE led to a very high rpm. The data shows the max rpm as 3991. Ouch.

Now I need to figure out what to do next. It is clear that all rotating or reciprocating components would have experienced very high stresses. It is possible that no damage was done. It is also possible that the high stresses could have started a crack in a critical component, leading to a catastrophic engine or prop failure down the road. I looked at my Hartzell Propeller Operators Manual, and it calls for an inspection by an overhaul shop if the prop experiences a speed of more than 110% the normal limit. The normal limit is 2700 rpm, so the prop saw 148% of the limit. If the prop sheds one blade, the out of balance forces usually cause the engine mount to fail, and once the engine departs the aircraft the CG is so far aft that control is usually lost, resulting in a fatal accident. I'm not willing to risk that, so I’ll either send the prop to an overhaul shop for inspection, or buy a new one. I’ll look into the option of getting an “aerobatic” prop, which goes to high pitch if the oil pressure drops. Unfortunately, that would require a different spinner, as apparently the counterweights at the blade root won't fit inside Van's spinner. Hopefully the base diameter of the spinner isn't too much larger, or I may have to do some cowling mods too.

I’ll call Bart Lalonde at AeroSport Power to get his take on the engine aspects, but I expect I’ll pull the engine and have him open it up for inspection. I may replace things like connecting rods, pistons, etc.

I was hoping to finish off the mandatory 25 hour test program next weekend. But, now I have grounded the aircraft after 12 flights and 17.4 hours. I expect there will be a couple month hiatus in the test program. I’ll post more when I have a plan.

In retrospect, I should have paid more attention to a small drop in oil pressure that I had seen during a power-on dive on an earlier flight. That was a sign that the oil was moving towards the front of the oil sump, away from the oil pickup. After that flight I added some oil, and repeated the condition with negligible effect on the oil pressure. But, I should have recognized that pulling the power to idle could cause the oil pressure to drop, and I should have done a work-up in speed on this test. I.e. do the test at a lower speed, and repeat at successively higher speeds. Also, I had already recognized that the propeller low pitch stop was set too fine, and I had made an adjustment before this flight. I shouldn’t have even tried this test until I was satisfied that the low pitch stop was correctly set (i.e., set so that the rpm is a bit less than 2700 during the initial part of the take-off run).

I’m glad this event didn’t occur when I was on the road. If you are going into a large airport, it is not uncommon for ATC to request a high speed until about five miles on final, to facilitate approach sequencing with the airliners. I can envision that I could be coming down the ILS at 180 KIAS, then pulling the power back a long ways to slow down.

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It has been a busy week. On Wednesday 8 Oct, I flew to Wichia for some avionics testing on the Hawker Beechcraft T-6B prototype. I flew three flights, finishing on Saturday, and came back home on Sunday. The T-6B has the same airframe and engine as the T-6A, but the avionics are all new, including a full glass cockpit, HUD, IRS, etc. Very nice aircraft.

Back home in Ottawa, I flew flight 7 on the RV-8 on Monday, concentrating on cruise performance testing. Flight 8 was on Tuesday, concentrating on airspeed system calibrations from 110 KIAS to 180 KIAS. The raw data shows about a one kt error at all speeds. The recorded data seems to confirm that. This afternoon I flew flight 9, doing a whole bunch of circuits with about a 5 kt left crosswind, sideslip tests, stalls, cruise power experimentation and a WAAS approach.

Flight 9 summary

Purpose: 1. Circuits, 1. SHSS build up.
1. Stall characteristics, 1. Min trim speed investigation1. Cruise power experimentation1. WAAS approach test

Snags:Turn coordinator needle does not move when the aircraft is yawed. The flag does remove when power is applied to the unit, so it seems that the gyro has died. Or, is it possible that there is some kind of shipping lock that I forgot to remove - I'll stick my head behind the panel to see if there is anything moveable on the other end of the instrument.

Results:No data was recorded, as the planned tests did not need it.

Circuits - 8 touch and go and one full stop landing were completed with approximately a 5 kt left crosswind. A final approach speed of 70 KIAS on the analog ASI was used, with full flap on all landings, except the final landing. The final landing was completed with 1/3 flap and a 75 KIAS approach speed. No handling issues were noted.

Stalls - with flaps up, at idle power, it seems that the aircraft cannot be completely stalled at full aft stick. Buffeting starts at 65 KIAS (EFIS) with full aft stick at 62 kt. There is no nose drop or wing drop, with aileron control still available. With full flap, there is buffet coincident with the stall at 51 KIAS (EFIS) The stall is identified by a nose drop, followed by wing rocking if the stick is held full aft. The ailerons remain effective.

SHSS build-up - idle power, full rudder steady heading sideslips were conducted at 80 and 70 KIAS with flaps up and with full flap. With flaps up, there is strong buffeting of the tail surfaces at approximately 90% rudder travel. The characteristic is the same in left and right sideslips. There is no buffeting out to full rudder with full flap. In principle, full rudder sideslips are only normally used if an approach is too high, so that would imply that full flap had already been selected.

Min trim speed - with full flap, and idle power, a small amount of aft stick force is required even at VFE.

Cruise power experimentation - the fuel flow system is still not completely calibrated, so no formal tests were conducted. It was noted that at 9500 ft, 2500 rpm and full throttle (21.2 in HG MP) and mixture leaned to 50 deg F LOP gave about 170 kt TAS (based on the EFIS IAS), and an indicated fuel flow of approximately 8 USG/hr.

A GPS Rwy 24 approach was conducted. The GNS 430 gave the expected indications, and the vertical guidance was present on the CDI. No anomalies were noted.

Total air time is now 12.7 hours, more than half way through the required 25 hours testing. I'm looking for some decent ballast to start moving the CG aft.

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I headed out to the airport first thing this morning, and hoped to perhaps get two flights done. But, when I did the walk around, I noted that I didn't have nearly enough clearance between the wheel pant openings and some parts of the tire. In fact, one tire was touching the wheel pant opening in one place. So, off came the wheel pants, and I removed a bunch of fibreglas. Two hours later I finally was ready to go flying.Given that this was the first flight with wheel pants, I concentrated on cruise performance. The air quality wasn't perfect, but initial indications are that I am getting very close to the speeds that I expected. I.e, I believe that Van's claimed 75% cruise numbers at 8000 ft actually were done with 2700 rpm and full throttle, as many people believe that this represents 75% power. In fact, with Van's excellent airbox design, and with the ram pressure recovery from RV speeds, the manifold pressure at full throttle at 8000 ft is high enough to develope quite a bit more than 75% power. Van's RV-8A prototype was tested by the CAFE Foundation, and at 2700 rpm and full throttle at 8000 ft it achieved the speeds that Van claims for 75% power.I also did some testing at 7500 ft with 75% power with mixture set to approximately best power, and 65% power with the mixture set lean of peak. I also did a series of runs at 2200 and 2300 rpm and full throttle, with the mixture set to get various fuel flows. At 75% power at 7500 ft, the speed with wheel pants, landing gear leg fairings, etc, was about 15 kt faster than the speed without those items. This is an approximate value, as the air quality today was not as good as when I did the baseline testing.I also did some forward CG stall characteristics testing. I was disappointed to find that I have essentially zero aerodynamic stall warning. This is good buffet right at the stall, but no warning before that. The aircraft does have a good stall, in that it does not drop a wing, except during full power stalls in a left turn, when the right wing drops.I did a bit deeper analysis of the hand recorded data from the airspeed calibration tests I did yesterday. If I use a reasonable assumption for OAT probe recovery factor (to be verified by later test), that brings the actual OAT values down a bit, and I get an airspeed error of about one knot. This is still preliminary data, as I should get more precision from the flight test data, when I find time to look at it.I've got 7.3 hours on the aircraft with 6 flights done.