Page 26 - Volume 18 Number 8

An unfeathering accumulator is simply an oil reservoir. When you feather the propeller, a valve traps pressurized oil in the accumulator. When you move the prop control out of feather to restart the engine, the valve opens. Pressurized oil rushes into the prop dome and helps move the blades out of feather and back into a running angle of attack (and therefore rpm).Unfeathering accumulators are really only useful for training, because there are few cases outside of training when you’d feather a propeller and then restart. Consequently, many airplanes, especially early light twins, don’t have them—it’s added weight and complexity that you don’t need to carry around unless you do a lot of inflight engine shutdowns. My PRI’s engines do not have unfeathering accumulators, so we briefed the Air Start procedure from the Pilot’s Operating Handbook that applies in such a case:• Fuel selector – On• Throttle – Set approximately 1⁄4 travel• Mixture – Full Rich• Fuel boost pump – Low• Magnetos – On• Propeller control – Out Of Feather To Mid-Range• Engine starter – Engage if propeller does not unfeather If engine fails to run:• Mixture - Idle Cutoff• When engine fires – Mixture Full RichPilots with fuel-injected engines know they’re sometimes hard to start when hot. Add a reduction in induction air and cooling airflow, as a result of doing this exercise at a safe altitude, and you can see the possibility things might not turn out as planned.Such was the case with my PRI. Despite his checklist efforts, the engine just didn’t want to restart. After several attempts, while I coached him to maintain blue line and appropriate bank and rudder inputs, we resigned ourselves to making a real-world single-engine landing at the nearby runway. During our shallow descent, I made sure we arced continually toward the airport, while also diligently watching out for other traffic.As we were about to call the tower, I suggested he try one more thing. We still had plenty of altitude and were pretty close to the airport. I suggested lowering the nose to gain about 10 to 15 knots, then try the starter one more time. The added airflow, tending to make the propeller windmill, did the trick. The engine relit. After a little hesitant adjustment of the power controls, we determined the engine was indeed running, and made an uneventful two-engine landing. The entire exerciseAircraft Performance ModificationsQuarter Page4/C AdLazy Susan for360° Free Rotation.Completely hands-free from load to unload.AC Air TechnologyQuarter Page4/C AdAC TrackTech T2For larger aircraft up to 21,000 lbsThe World’s Lowest Profile, Remote-Control Aircraft TugOrder yours now! (855) 884-7222 www.acairtechnology.com24 • TWIN & TURBINEAUGUST 2014