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In July of 2001, Jim Crabtree, a BD-5 builder, contacted us with a request to perform the break-in on his Rotax 582. A tight installation, particularly pusher configuration, like the BD-5, often makes the published break-in nearly impossible. Neglecting the break-in is always a bad idea, especially so with the BD-5 and it's very high landing speed ...Blasting off into the wild blue with zero operational evaluation is a foolhardy act. Other issues were the modified exhaust system, and function of the special HAC (high altitude compensating) carburetors
The fact that this powerplant performed as expected during this test does not automatically mean it will do so when installed in the BD-5. However, these checks do eliminate some unknowns in preparation for testing in that aircraft.
Below are some images from that day of testing.
Click to enlarge
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Here, and at the right Removing the GSA Remanufactured 582 |
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On this engine, a single compensator (HAC) regulates pressure to each carburetor float bowl there by changing the mixture. Changes in density altitude are sensed through a static line on one airfilter to affect the deflection of a diaphragm in the HAC chamber. The diaphragm moves a metering pin which varies vacuum to the float chamber(s) |
Caution!
The HAC will alter the mixture of both Carburetors.
Solution: On dual carb HAC installations, use the single oval filter with provision for both carbs |
Once the installation was pretty much set, Mr Crabtree was invited to proceed with the Rotax Break-In Sequence |
This muffler started out as a The inlet cone was cut in the middle and turned 180 degrees. No change in tuning wouldbe expected from such a modification. Observe, though, on the muffler canister, the last (silencing) chamber was eliminated for airframe clearance consideration. Theoretically, this mod would affect only the sound, but a comparison test would be the proof. Note: The 90° elbow pictured attached to the inlet end, is a stock (973 180) elbow, connected by an "aftermarket" fastener. |
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The exhaust configuration
for the Zippy Sport is a 100% stock Rotax 3-piece system, with Fisher style
muffler. On this day of testing, the subject engine was set up with
a Type B 2.58:1 Gearbox, 54 inch GSC Tech III
Prop
with standard blade profile, set to degrees pitch. The
owner's HAC carburetors with standard HAC jetting were also used. During
the early stages of the Break-in sequence, it was discovered that propeller
loading was limiting full throttle rpm to an acceptable (for purposes of
this test) 6,250±, however, EGT was very close
to the 1200°F limit, so the run was halted long enough to set
jet needles one position richer. Upon resumption of the sequence, engine
break-in was completed without exceeding any temperature or operational
limit.
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Exhaust Test
Conclusion:
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Following completion of the break-in, the engine was allowed to cool, and a general inspection of the installation was performed. Later, a brief test flight was conducted
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Jim and Jerry ham it up for the camera |
If
you would like to view some pictures from a pilots perspective, click 
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