Kevin Horton's RV-8 Project

Results:

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.

Fuel flow indication is much, much more stable than before.

All four CHTs are now within 30 deg F of each other the vast majority of the time.

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.

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.

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.

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.

Full glide performance results will be reported later.

Flt 44 Report | 4 comments | Create New Account

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Flt 44 Report

Authored by: psychose on Friday, November 20 2009 @ 12:44 PM EST

Hello Kevin,

What was the problem with the Fuel Flow transducer in its previous position? I've read through many of your previous pages but did not find any mention of it.

I was thinking of installing the transducer immediately after the electric fuel pump in the cockpit. Do you think there would be anything wrong with this?

Also, was wondering if some kind of friction brake to stop the turning prop might be useful in order to get the better glide ratio in the event of an engine failure...

Keep flying!

Normand

Flt 44 Report

Authored by: Kevin Horton on Friday, November 20 2009 @ 06:00 PM EST

Norm,

The fuel flow indication wasn't as stable as I hoped for in its original location, between the electric boost pump and the engine-driven fuel pump. The average indication was good, as evidenced by the excellent accuracy of the fuel quantity calculated by the fuel flow system. But, even at a stable power setting, the fuel flow indication would frequently vary up or down one or two USG/hr. It isn't perfectly stable in its new location, but the variations are much smaller.

Apparently, the Floscan fuel flow transducers don't like being on the suction side of the engine-driven fuel pump. They are apparently much happier if they are on the pressurized side of the system. Apparently, the Electronics International FT-60 fuel flow transducer is much more tolerant of a location on the suction side of the fuel pumps.

I don't think the advantage of being able to stop the prop is worth the cost of the extra weight, cost, complexity and new failure modes of a friction brake. Just my opinion.

---
Kevin Horton

Flt 44 Report

Authored by: psychose on Monday, November 23 2009 @ 03:45 PM EST

I realise that an additional gizmo probably is not worth the trouble. Was thinking afterwards, do you believe that increasing the electrical load (i.e., taxi/landing lights, pitot heat, strobes) could work?

Normand

Flt 44 Report

Authored by: Kevin Horton on Monday, November 23 2009 @ 09:15 PM EST

Norm,

I had the pitot heat ON, and the landing and taxi lights were running in wig-
wag mode. Adding the strobes and selecting the landing and taxi lights to full
time ON would only add a few amps. An extra 10a load would take only about
1/4 extra hp to drive the alternator. I doubt that this tiny extra load would make
that much difference. But, you never know.

---
Kevin Horton

Flt 44 Report

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